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Why is the vermis of the cerebellum associated with speech?

Why is the vermis of the cerebellum associated with speech?


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I've found multiple sources claiming that damage or impairment as a result of alcohol to the vermis of the cerebellum results in speech impairment. I find this a bit surprising, since the only areas I know that are used for speech production are Broca's area. Additionally, I don't know of any way that the vermis influences this area or any other facial nerve that may need co-ordination to produce speech.

So why does damage/impairment of the vermis result in dysarthria?


Although speech production is in generally executed in the cerebral domain, the dysarthria resulting from damage of the vermous is a symptom of the resulting general muscle weakness. So yes, you get slurred speech because your muscles are weak, but the weak muscles certainly aren't ever isolated to speech production.


Difference Between Cerebrum and Cerebellum

The difference between cerebrum and cerebellum is mainly due to the following properties like size, constitution to brain and location. They both contribute to the human brain or central nervous system and plays an integral role in our everyday life. The size of the cerebrum is the largest part of the brain, while cerebellum is much smaller or the second largest part of the brain.

Cerebrum constitutes about 83% of the total brain, whereas cerebellum constitutes about 11% of the brain. The cerebrum is a part of the brain located in the forebrain, whereas cerebellum is located in the hindbrain.

Cerebrum and cerebellum are the two major parts of the brain, which remain isolated through dura matter and communicate through the brain stem. Here, you will get to know a detailed comparison of the topic through the comparison chart, and the key differences explained in this article. Also, the definition and the structural components of the cerebrum and cerebellum are discussed.


Cerebellum: Meaning, Feature and Functions | Human Physiology

In this article we will discuss about:- 1. Meaning of Cerebellum 2. Special Features of Cerebellum 3. Division 4. Connection 5. Function.

Meaning of Cerebellum:

Cerebellum is also termed as little brain. Present in the posterior part of cranial fossa below occipital lobe.

Connected to other parts of brainstem by three pairs of peduncles, namely:

In cerebellum, there is a lot of white matter just like in cerebral cortex. Deep below the white matter many nuclei of cerebellum are present.

c. Globose (the nucleus emboliform and globose together sometimes refer to as nucleus interpositus)

Special Features of Cerebellum:

a. Though cerebellum receives a lot of afferent inputs fibers of proprioceptors from various parts of body, conscious perception of sensation will not be possible.

b. It cannot exert its control directly over LMN. However, influence from cerebellum on LMN is essential for proper co-ordination of any movement.

c. Unlike cerebral cortex that controls activity of contralateral half of body, cerebellum controls motor activity of ipsilateral half of body.

d. Apart from nuclei, we find Purkinje, granular, basket, and Golgi cells are also present. There is lot of connection between these various cells.

Divisions of Cerebellum:

Formed by important parts (anatomically) Fig. 9.37:

Phylogenetically (i.e. depending on order of development during evolution), cerebellum is sub­divided into:

a. Archicerebellum (primitive)

Functionally cerebellum is subdivided into (Fig. 9.38):

a. Flocculonodular lobe (corresponds to archicere­bellum) also known as vestibulocerebellum.

b. Vermis and part of cerebellum immediately lateral to vermis on either side in anterior and posterior lobes is known as spinocerebellum.

c. Most lateral part of cerebellar hemisphere is known as cerebrocerebellum/corticocerebellum. This part is very highly developed in human beings.

Connections of Cerebellum (Fig. 9.39):

Afferent Connections:

Cerebellum has a lot of afferent inputs coming from proprioceptors (receptors involved in sense of position and movement). However, when impulse reaches cerebellum, it will not come to conscious perception.

a. The proprioceptive inputs from head and neck region reach cerebellum through cuneocerebellar tract.

b. Vestibulocerebellar pathway carries proprioceptive inputs from vestibular apparatus present in inner ear. Proprioceptive impulses from vestibular apparatus reach cerebellum through vestibular nuclei present in brainstem.

c. Dorsal and ventral spinocerebellum tracts carry proprioceptive impulses from both contralateral and ipsilateral sides of various parts of body.

d. Tectocerebellar pathway carries afferent impulses from superior and inferior colliculi of tectum of midbrain. This colliculus receives afferent inputs from visual and auditory areas.

e. Olivocerebellar tract takes origin from inferior olivary nucleus. Inferior olivary nucleus receives afferent proprioceptive inputs from almost all parts of body.

f. Also there are corticopontocerebellar fibers which come from motor and premotor (area number 4 and 6) areas of cerebral cortex.

Efferent Connections:

The cerebellum can exert its influence either on nuclei in brainstem or neurons present in motor and pre­motor areas of cerebral cortex through the following efferent connections namely:

Cerebellum has no direct influence on LMN present in spinal cord. But, influence on LMN of spinal cord is through various descending tracts that take origin from brainstem regions (Fig. 9.40).

Functions of Cerebellum:

a. Regulation of posture and equilibrium:

Flocculonodular lobe is involved in this function. It receives afferent inputs from vestibulocerebellar tract and proprioceptors from all over the body. Afferent inputs coming to flocculonodular lobe are processed, and efferent impulses from cerebellum are sent to vestibular and reticular nuclei present in brainstem.

From these nuclei, impulses are sent to lower motor neurons through vestibulospinal and reticulospinal tracts. Impulses coming from flocculonodular lobe control activities of axial (midline trunk) muscles and proximal limb muscles (muscles which attach limb to trunk part of the body).

Hence cerebellum has an important role to play in maintenance of posture and equilibrium.

b. Also controls activities of extraocular muscles which control eye movements through medial longitudinal bundle. This bundle controls activity of 3, 4, and 6 cranial nerve motor nuclei. Thus flocculonodular lobe of cerebellum helps in fixing gaze/vision. Even though position of head is fixed, we can move eyeballs to focus on any particular object/subject that we want to see.

c. Cerebellum also brings about coordination of movements. For smooth movements to be brought about, there will be involvement of three groups of muscles.

i. Agonists/protogonists—directly involved in performing a movement.

ii. Antagonists—muscle group involved in opposing movements are made to relax.

iii. Synergistic—not directly involved but needed for coordination of smooth movement.

In cerebral cortex, only movements are represented and not individual muscles.

During coordination of movement, the following characteristic features have to be taken care off:

i. Force generated during movement

If there is an error in any one or all of characteristics, there is said to be in-coordinated movement (ataxia). Ataxia is characteristic feature in cerebellar lesion and this is called as motor ataxia. Ataxia can also occur due to some sensory deficits in which case it is called as sensory ataxia (posterior or afferent nerve root lesion, thalamic syndrome).

Coordination of movement is possible because cerebellum acts as servo comparator.

Whenever impulses are sent from motor and pre- motor areas of cerebral cortex to LMN, a copy of the command is sent to cerebellum through the corticopontocerebellar pathway (Fig. 9.41).

Cerebellum behaves as a servo comparator. Movements are initiated in the body due to impulses coming to part of body through corticospinal tracts. A copy of the command sent to LMN by cerebral cortex is also sent to cerebellum through cortioponto- cerebellar pathway.

During every step of movements, proprioceptive impulses arising from muscles and joints are sent back to cerebellum from the part of body that is involved in movement. These inputs keep informing cerebellum about various aspects of movement that is taking place (like degree of movement, direction, force, etc.).

If movement is not according to motor command, cerebellum compares command for intended movement with the movement that is going on (afferent inputs will be informing about this) and any rectification of error is faithfully relayed back to motor cortex through dentato-rubro-thalamo-cortical pathway. This leads to modification/rectification of movements so that target is reached accurately.

d. Cerebellum also helps in maintenance of muscle tone:

Vestibulocerebellum influences activity of vestibular nucleus and pontine reticular formation. Spinocerebellum influences activities of nuclei present in brainstem. Rubrospinal, vestibulospinal and pontine reticular formation extend their influence over LMNs present in spinal cord.

The efferent impulses coming from cerebellum through these nuclei are generally excitatory to LMNs. Because of this, if there is cerebellar lesion it leads to hypotonia (decreased muscle tone).

e. Cerebellum also has a role to play in learning and memory especially some of movements which are to be excelled for a short time by repeated trials.

Features of Cerebellar Lesion:

1. Imbalance in posture and equilibrium

2. Incoordination of movements

4. Knee jerk gets affected (pendular knee jerk)

Applied Aspects:

Vestibulocerebllar damage:

Unsteady gait/posture. The person will have drunken gait (feet far apart from each other).

Control of subconscious associated movements will be absent, for example, swinging of arms while walking will be absent.

Ataxia or incoordination of movement is also seen:

Incoordination leads to features, like.

Rate of movement (it may over shot or under shoot the target). Unable to gauge length of movement efficiently.

Inability to perform rapid alternating movements (alternatively supinating and pronating the palm, or flexion and extension fingers, etc.) cannot be brought about.

c. Decomposition of movement:

When one has to perform any complex movement involving many joints, normally the movement can be quite brisk and smooth. But when there is in-coordination or ataxia, complex movement will occur, but in steps and slowly, that is movement at each joint will be performed as a separate entity one after the other.

Speech is also affected. Speech is usually a complex movement involving articulation of lips, laryngeal muscles, tongue, etc. In cerebellar lesion, slow staccato speech is observed that is a single word is broken into many syllables.

As long as the person is at rest, tremors will be absent. Tremors are seen when any voluntary movement starts and the intensity of tremors increase during the course of movements. So these are known as intention/kinetic tremors.

Knee jerk is an example of deep reflex. When knee jerk is elicited in a person suffering from cerebellar lesion, the knee jerk becomes pendular. Muscle tone will be less than normal that is hypotonia in the case of human beings.


Cerebellum

The cerebellum is the largest structure in the posterior fossa (see figures 15.1, 15.2, & 15.3). It is attached to the dorsal aspect of the pons and rostral medulla by three white matter peduncles and forms the roof of the fourth ventricle. It consists of:

  • Vermis – the midline structure, named for its “wormlike” appearance
  • Cerebellar Hemispheres

Cerebellar Tonsils

  • Important landmark on the inferior surface, which may be herniated secondary to mass lesions of the cerebrum or cerebellum, or brain swelling and associated severely elevated intracranial pressure
  • With severe herniation, the tonsils may herniate through the foramen magnum, compress the medulla, and cause death through impingement on the medullary respiratory centers

Cerebellar Peduncles

  • Superior Cerebellar Peduncle Carries mainly output from the cerebellum
  • Middle and Inferior Cerebellar Peduncles Carry mainly input to the cerebellum

Cerebellar Functions

  • Serves to integrate sensory and other inputs from many regions of the brain and spinal cord (SC)
  • Coordinates and “smoothes” ongoing movements and participates in motor planning
  • Has no direct connections to lower motor neurons, but exerts its influence through connections to motor systems of the cortex and brainstem

Different regions of the cerebellum have specialized functions

  • Inferior Vermis and Flocculonodular Lobes Regulate balance and eye movement through interactions with the vestibular circuitry
    • Act with other parts of the vermis to control medial motor systems (i.e., proximal trunk and limb muscles)

    Additional Functions of the Cerebellar Pathways

    • Articulation of speech
    • Respiratory movements
    • Motor learning
    • Higher-order cognitive functions

    Functional Regions of the Cerebellum – Table

    Region Functions Motor Pathways Influenced
    Lateral Hemispheres (largest part of the cerebellum) Motor planning for extremities Lateral Corticospinal tract
    Intermediate Hemispheres Distal limb coordination (especially the appendicular muscles in the legs and arms) Lateral Corticospinal tract and Rubrospinal tract
    Vermis Proximal limb and trunk coordination Anterior Corticospinal tract, Retibulospinal tract, Vestibulospinal tract and Tectospinal tract
    Flocculonodular Lobe Balance and vestibulo-ocular reflexes Medial Longitudinal fasciculus

    Of Interest: Cerebellar lesions typically result in a characteristic type of irregular uncoordinated movement – Ataxia.

    Cerebellar Output Pathways

    Output pathways are organized around the three functional regions of the cerebellum:

    • Lateral Hemispheres
    • Intermediate Hemispheres
    • Vermis plus Flocculonodular Lobe

    Pathways from the cerebellum to the lateral motor systems and then to the periphery are “double crossed”

    • 1st crossing occurs as the cerebellar output pathways exit in the decussation of the superior cerebellar peduncle
    • 2nd crossing occurs as the corticospinal and rubrospinal tracts descend to the spinal cord. Inputs also follow this pattern, so each cerebellar hemisphere receives information about the ipsilateral limbs

    Cerebellar Input Pathways

    Input to the Cerebellum Arises From

    • All areas within the CNS
    • Multiple sensory modalities (e.g., vestibular, visual, auditory & somatosensory systems)
    • Brainstem nuclei
    • Spinal cord

    Input is somatotopically organized, with the ipsilateral body represented in both the anterior and posterior lobes Major source of input consists of corticopontine fibers (i.e., from frontal, temporal, parietal & occipital lobes) that travel in the internal capsule and cerebral peduncles

    • Derive from primary sensory and motor cortices and part of the visual cortex
    • Travel to the ipsilateral pons and synapse in the pontine nuclei
    • Pontocerebellar fibers cross the midline to enter the contralateral middle cerebellar peduncle and give rise to mossy fibers that innervate much of the cerebellar cortex

    Spinocerebellar fibers comprise another major source of cerebellar input and provide afferent information to the cerebellum

    • Information about limb movements conveyed by the dorsal spinocerebellar tract and the cuneocerebellar tract
    • Of Interest: Spinocerebellar input is either ipsilateral or “double-crossed” —> ipsilateral limb ataxia when lesioned

    Vascular Supply to the Cerebellum

    Blood Supply to the Cerebellum

    Provided by three branches of the vertebral and basilar arteries:

    Posterior Inferior Cerebellar Artery (PICA)

    Anterior Inferior Cerebellar Artery (AICA)

    Superior Cerebellar Artery (SCA)

    In addition to supplying the cerebellum, these arteries course through the brainstem, providing blood to portions of the lateral medulla and pons.

    Of Interest: Infarcts are more common in the PICA and SCA than in the AICA territory.

    Principles for Localizing Cerebellar Lesions

    • Ataxia is ipsilateral to the side of the cerebellar lesion
    • Midline lesions of the cerebellar vermis or flocculonodular lobes mainly cause unsteady gait (i.e., truncal ataxia) and eye movement abnormalities, which often are accompanied by intense vertigo, nausea and vomiting
      • Affect the medial motor systems
      • Do not typically cause unilateral deficits because the medial motor systems influence the proximal trunk muscles bilaterally

      Of Interest: The cerebellum has multiple reciprocal connections with the brainstem and other regions therefore ataxia may be seen with lesions in those areas as well

      Lesion Location Functional Impact
      Lateral cerebellum Distal limb coordination
      Medial cerebellum Trunk control, posture, balance and gait

      Of Interest: Deficits in coordination occur ipsilateral to the lesion

      Cerebellar Infarcts – Key Clinical Concepts

      Characteristic Symptom Presentation

      • Vertigo
      • Nausea and vomiting
      • Horizontal nystagmus
      • Limb ataxia
      • Unsteady gait
      • Headache (localized to occipital, frontal, or upper cervical regions)

      Of Interest: Many of the signs and symptoms of cerebellar artery infarct result from infarction of the lateral medulla or pons, rather than the cerebellum – Infarcts of these areas may cause trigeminal and spinothalamic sensory loss, and Horner’s syndrome.

      *Conversely, infarcts of the lateral medulla or pons can cause ataxia because of involvement with cerebellar peduncles, even if the cerebellum is spared.

      Infarct Patterns

      • Infarcts that spare the brainstem and involve predominantly the cerebellum are more common with SCA infarcts than with PICA or AICA, therefore infarcts causing unilateral ataxia with little or no brainstem signs are most commonly in the SCA territory
      • Infarcts of the PICA and AICA more often involve both the lateral brainstem and cerebellum
      • Infarcts of the lateral pons or medulla that spare the cerebellum typically occur with PICA or AICA rather than SCA
      • Large cerebellar infarcts that involve the territories of the PICA or SCA can cause swelling of the cerebellum
        • Subsequent compression of the fourth ventricle can cause hydrocephalus
        • Compression in the posterior fossa may be life threatening because the respiratory centers and other vital brainstem structures may be affected
        • Surgical decompression and resection of portions of the infracted cerebellum
        • Hemorrhage into the cerebellar white matter also can cause brainstem compression

        Cerebellar Hemorrhage – Key Clinical Concepts

        Characteristics Symptom Presentation

        Large Cerebellar Hemorrhages May Cause

        • Hydrocephalus [treated with ventriculostomy]
        • 6th nerve palsies
        • Impaired consciousness
        • Brainstem compression
        • Death

        Can Occur Secondary To

        • Chronic hypertension
        • Arteriovenous malformation
        • Hemorrhagic conversion of an ischemic infarct
        • Metastases
        • May include surgical evacuation of the hemorrhage and decompression of the posterior fossa.
        • Hydrocephalus treated by ventriculostomy carries with it the risk of upward transtentorial herniation.

        Signs and Symptoms of Cerebellar Disorders

        • Nausea
        • Vomiting
        • Vertigo
        • Slurred speech
        • Unsteadiness
        • Uncoordinated limb movements
        • Headache Occurs in the frontal, occipital, or upper cervical regions, and usually occurs on the side of the lesion

        Most Abnormalities a Combination Of

        Dysrhythmia

        Incipient Tonsilar Herniation Lesions May Cause

        • Depressed consciousness
        • Brainstem findings
        • Hydrocephalus
        • Head tilt [also seen with lesions to the anterior medullary velum]

        Additional Cerebellar Disorders

        Dysdiadochokinesia

        • (aka adiadochokinesia) Abnormalities of rapid alternating movements, such as tapping one hand with the palm and dorsum of the other hand

        Eye Movement Abnormalities

        • Ocular Dysmetria Saccades overshoot or undershoot their target
        • Slow Saccades Present in some degenerative disorders involving the cerebellum
        • Nystagmus Typically of the gaze paretic type in which the patient looking toward a target in the periphery exhibits slow phases toward the primary position and fast phases occur back toward the target. May change directions depending upon the direction of gaze (unlike peripheral vertigo).
        • Vertical Nystagmus may occur.

        Speech Abnormalities

        • Scanning or Explosive Speech Individual’s speech may have an ataxic quality in cerebellar disorders with irregular fluctuations in both rate and volume
        • Cerebellar dysfunction also may cause slurring or articulatory problems

        Cerebellar Disease

        Abnormalities That Can Confound the Cerebellar Exam

        Upper Motor Neuron Signs

        Lower Motor Neuron Signs

        • With severe upper or lower motor weakness, cerebellar testing may not be possible
        • Precision finger tapping may be helpful, as cerebellar involvement typically causes the tip of the finger to hit a different spot on the thumb each time [See neuroexam.com Video 63]

        Sensory Loss

        • Loss of joint position sense can cause sensory ataxia
        • Loss of position sense must be severe and sensory ataxia usually improves with visual feedback

        Basal Ganglia Dysfunction

        • Movement disorders (e.g., parkinsonism) associated with basal ganglia involvement can cause slow, clumsy movements or gait unsteadiness
        • Tremor and dyskinesia also may confound the cerebellar examination

        Clinical Findings and Localization of Cerebellar Ataxia

        • Means literally “lack of order”
        • Refers to the disordered contractions of the agonist and antagonist muscles and lack of normal coordination between movements at different joints
        • Characterized by movements that have an irregular, wavering course that seems to consist of continuous overshooting, overcorrecting and then overshooting again around the intended trajectory

        Characteristics of Ataxic Movements

        Ipsilateral Localization of Ataxia

        • Cerebellar connections involved in the lateral motor system are either ipsilateral or cross twice (i.e., “double crossed’) between the cerebellum and spinal cord
        • Lesions of the cerebellar hemispheres cause ataxia in the extremities ipsilateral to the side of the lesion
        • Lesions of the cerebellar peduncles lead to ipsilateral ataxia

        In contrast: cerebellar lesions affecting the medial motor system cause truncal ataxia, which is a bilateral disorder, but patients with truncal ataxia often fall or sway toward side of lesion

        False Localization of Ataxia

        • Ataxia may be caused by lesions to the cerebellar input or output pathways located outside the cerebellum
        • Lesions in the cerebellar peduncles or pons (without damage to the cerebellar hemisphere) —> severe ataxia
        • Hydrocephalus [which may damage frontopontine pathways] and lesions within the prefrontal cortex —> gait abnormalities similar to truncal ataxia
        • Disorders of the spinal cord —> gait abnormalities

        Truncal Ataxia versus Appendicular Ataxia

        Truncal Ataxia

        • Caused by lesions confined to the cerebellar vermis
        • Affect primarily the medial motor systems
        • Lead to wide-based, unsteady, or “drunk like” gait or truncal ataxia
        • In severe cases, patients may even have difficulties sitting up without support

        Appendicular Ataxia

        • Caused by lesions of the intermediate and lateral portions of the cerebellum
        • Affect the lateral motor systems
        • Cause ataxia on movement of the extremities

        Of Interest: Lesions often extend to include both the vermis & cerebellar hemispheres and truncal and appendicular symptoms may coexist. More severe and longer-lasting deficits may occur with lesions of the intermediate hemisphere, vermis, deep nuclei, and cerebellar peduncles.

        • Unilateral lesions in the medial portion of the cerebellar hemisphere may produce no appreciable deficit.

        Ataxia-Hemiparesis

        • Syndrome caused by lacunar infarcts
        • Presentation includes a combination of unilateral motor neuron signs and ataxia, usually affecting the same side
        • Both the ataxia and hemiparesis are contralateral to the lesion side
        • Most often caused by lesions in the:
          • Corona radiata
          • Internal capsule
          • Pons that involve both corticospinal and corticopontine fibers
          • Frontal lobes
          • Parietal lobes
          • Sensorimotor cortex
          • Midbrain lesions that involve fibers of the superior cerebellar peduncle or red nucleus

          Sensory Ataxia

          • Occurs when the posterior column – medial lemniscal pathway is disrupted
          • Causes impaired or loss of joint position sense [not typically observed in cerebellar patients]
          • Characterized by ataxic-appearing overshooting movements of the limbs and a wide-based, unsteady gait [similar to cerebellar involvement]
          • May improve significantly with visual feedback
          • Worsens with eyes closed or in the dark
          • Typically involves lesions of the peripheral nerves or posterior columns —> ipsilateral ataxia
          • May occur secondary to lesions in the thalamus, thalamic radiations or somatosensory cortex —> contralateral ataxia

          Tests for Ataxia

          Finger-Nose-Finger Test

          (see Figure 15.14 and neuroexam.com Video 64)

          • Patient alternately touches her nose and then the examiner’s finger
          • Sensitivity of the test may be increased by holding the target finger at the limit of the patient’s reach or by moving the target finger to a different position each time the patient touches her nose

          Heel-Shin Test

          (see neuroexam.com Video 65)

          • Patient rubs his heel up and down the length of his shin in as straight a line as possible
          • Performed in the supine position to decrease contribution of gravity
          • Variations include tapping the heel repeatedly on the same spot just below the knee or having the patient alternately touch his knee and the examiner’s finger

          Of Interest: Rapid tapping of the fingers together, hand on the thigh, or foot on the floor are good tests for dysrhythmia (see neuroexam.com Videos 52 & 53).

          Testing for Overshoot or Loss of Check

          • Have patient raise both arms suddenly from their lap or lower them suddenly to the level of the examiner’s hand [see neuroexam.com Video 66] or
          • Apply pressure to the patient’s outstretched arms and suddenly release it

          Testing for Truncal Ataxia

          Wide-based, unsteady gait that resembles the drunk or a toddler may be observed with cerebellar involvement. Alcohol impairs cerebellar function and the cerebellar pathways of toddlers is not fully myelinated.

          Tandem Gait Testing

          • The patient is instructed to touch the heel with the toe of the other foot on each step, which forces the patient to assume a narrow stance
          • Patients will fall or deviate toward the side of the lesion (see neuroexam.com Video 68)

          Romberg or Romberg’s Test

          • Patient is asked to stand with feet together for half a minute, then asked to close eyes
          • A positive Romberg’s test occurs if the patient can stand with eyes open, but falls when they are closed.
          • The Romberg test indicates a proprioceptive lesion and is NOT a test of cerebellar function
          • With midline cerebellar lesions, the patient has difficulty standing with eyes open as well as closed [with these lesions, a peculiar tremor of the trunk or head, titubation, also can occur]
          • May help differentiate cerebellar lesions from lesions of the vestibular or proprioceptive systems

          (see neuroexam.com Video 67)

          Differential Diagnosis and Common Causes of Ataxia

          Differential Diagnosis (depends on)

          Common Causes

          Acute Ataxia in Adults

          Chronic Ataxia in Adults

          • Brain metastases
          • Chronic toxin exposure (especially to alcohol)
          • Multiple sclerosis
          • Degenerative disorders of the cerebellum or cerebellar pathways

          Acute Ataxia in Pediatric Patients

          Chronic or Progressive Ataxia in Pediatric Patients

          • Cerebellar astrocytoma
          • Medulloblastoma
          • Friedreich’s ataxia
          • Ataxia-telangiectasia

          Brief Anatomical Study Guide

          • Located in the posterior fossa
          • Consists of:
            • midline vermis
            • intermediate part of the cerebellar hemisphere
            • lateral part of the cerebellar hemisphere
            • superior cerebellar peduncle
            • middle cerebellar peduncle
            • inferior cerebellar peduncle

            Outputs of the Cerebellum

            All are carried by the deep cerebellar nuclei and the vestibular nuclei. The cerebellar cortex and the deep nuclei can be divided into three functional zones:

            • Vermis (via fastigial nuclei) and flocculonodular lobes (via vestibular nuclei)
              • Function in the control of proximal and trunk muscles and vestibulo-ocular control, respectively
              • Functions in the control of more distal appendicular muscles mainly in the arms and legs
              • Largest part of the cerebellum
              • Involved in planning the motor program for the extremities

              Cerebellar input and output pathways

              • Form a complex system
              • Follow a medial-lateral organization and all pathways to the lateral motor systems are either ipsilateral or double crossed so that cerebellar lesions cause ipsilateral deficits

              Local Cerebellar Neurons

              • Granule cells
              • Inhibitory cells
              • Golgi cells
              • Basket cells
              • Stellate cells

              Principles of Localizing Cerebellar Lesions

              (based on anatomical organization of the cerebellar pathways)

              • Ataxia is ipsilateral to the side of the cerebellar lesion
              • Midline lesions of the cerebellar vermis or flocculonodular lobes cause mainly unsteady gait (i.e., truncal ataxia) and eye movement abnormalities
              • Lesions of the intermediate part of the cerebellar hemisphere cause mainly ataxia of the limbs (i.e., appendicular ataxia)
              • Ataxia is often caused by lesions of the cerebellar circuitry in the brainstem or other locations rather than in the cerebellum itself, which can lead to false localization
              • Because of the strong reciprocal connection between the cerebellum and vestibular system, cerebellar lesions often are associated with:
                • Vertigo
                • Nausea
                • Vomiting
                • Nystagmus

                Characteristic irregular movement abnormalities seen in cerebellar disorders


                Conclusion

                Multiple functional imaging studies show the cerebellum is active during volitional swallowing [18, 50, 51]. Additionally, animal studies have shown that electrical stimulation of the cerebellum can trigger chewing and feeding behaviour in different animal species [43, 46]. Subsequent non-invasive neurostimulation studies in healthy human participants have shown rTMS targeted over the cerebellar hemispheres or vermis can cause cortical pharyngeal area excitation [34] or suppression [41] as well as resulting in changes to swallowing behaviour [16]. When taken together, the narrative these studies give is that the cerebellum is an important part of swallowing motor control. However, studies involving cerebellar pathology have cast some doubt on the importance of the cerebellum in the neurological co-ordination of swallowing. Stroke studies have shown isolated and discrete cerebellar lesions are unlikely to directly lead to dysphagia [85]. These seemingly disparate and contrasting strands of evidence can perhaps be interwoven by reference to studies indicating the neurophysiological control of swallowing is driven not, as may be expected, by a single large circuit encompassing all swallowing related brain areas, but instead by multiple modular swallowing circuits each interacting with and running parallel to each other [19]. The cerebellum influences other swallowing circuits including, for example, a circuit composed of the primary motor, supplementary motor and primary sensory cortical areas and the cingulate gyrus [19] (Fig. 5). The manner of this influence is not just thought to be fine tuning of distantly initiated motor activity [89], but the generation of a hypothetical internal model of motor activity immediately prior to movements being initiated so as to allow movements to be compared and adjusted against this internal ideal [19, 90]. Therefore, it may be that the cerebellar part of the modular circuit is not as essential to the initiation of swallowing as for example circuits containing the primary motor areas or brainstem structures. Instead, isolated damage to the cerebellum may more likely result in relative incoordination as opposed to complete cessation of a swallow and clinically relevant dysphagia. Despite this, the cerebellum, given its modulatory effects on the cortex, offers an exciting new avenue for neuro-stimulatory treatments which need to be studied in further detail. More and larger functional imaging and neurostimulation studies are required in this field so as to provide answers to bridge these gaps in our knowledge.

                Modular swallowing areas within the brain. Arrows show cortical parietal insula circuit and cerebellar modulation. Image simplified and adapted from [19]


                Treating the Effects of Cerebellar Damage

                Most effects of cerebellum brain damage are a result of poor communication between the brain and the muscles. Because of the damage that has occurred, the signals that the brain sends to coordinate movements do not reach the correct muscles.

                Therefore, to treat these effects, patients must improve communication between their brain and the rest of the body. Fortunately, you can accomplish this by activating your brain’s natural repair mechanism, neuroplasticity. The best way to do this is through repetitious exercise.

                When you practice a task, even if you can’t do it perfectly, your brain forms new neural pathways in response. After enough time and practice, the new pathways become stronger and the connection to your muscles may partially return. This allows you to coordinate movement again.

                Apraxia Treatment

                Since apraxia after cerebellum brain damage affects the neuromuscular system, the best way to treat it is to activate neuroplasticity through practicing the movement you want to regain.

                For example, if you have trouble eating, break down the process into separate steps, and practice each step individually before putting them all together. A sample exercise might look like this:

                • Bring hand down to the table
                • Open fingers
                • Grasp spoon
                • Bring spoon to mouth

                The more you practice, the more your brain will create new neural pathways. This can allow you to regain that function.

                Sometimes cerebellar brain damage makes it hard to visualize the steps you need to take to complete an action. A physical or occupational therapist can help you with this.


                Inheritance Inheritance

                Cerebellar degeneration is associated with a variety of inherited and non-inherited conditions. One example of an inherited form of cerebellar degeneration is spinocerebellar ataxia (SCA), which refers to a group of conditions characterized by degenerative changes of the cerebellum, brain stem, and spinal cord. Depending on the type, SCA can be inherited in an autosomal dominant , autosomal recessive , or X-linked manner. [3] [1]

                Other complex conditions such as multiple sclerosis and multisystem atrophy are also associated with cerebellar degeneration. These conditions are likely caused by the interaction of multiple genetic and environmental factors . Although complex conditions are not passed directly from parent to child, reports of familial forms exist. This suggests that a genetic susceptibility to these conditions can run in families. [4] [5]

                Many causes of cerebellar degeneration are acquired (non-genetic and non-inherited) including strokes, transmissible spongiform encephalopathies, chronic alcohol abuse and paraneoplastic disorders. [1]


                REVIEW OF THE LITERATURE

                Cases of intellectual impairment and aberrant behavior in patients with cerebellar disease were described as early as 1831. 5 Through the latter part of our century, there have been selected reviews of the potential role of the cerebellum in cognition and behavior. 6–8 However, the role of the cerebellum has remained largely ignored by psychiatry until relatively recently. By analogy, the basal ganglia initially were felt to subserve primarily motor functions, and it was not until the early 1970s, when interest developed in “subcortical dementia,” 9 that the role of the basal ganglia in cognition and behavior became appreciated. Since that time, supported by a growing anatomical and theoretical literature in nonhuman primates, 10,11 psychiatrists have become very interested in the role of the basal ganglia in the psychiatric features associated with Parkinson's disease, 12 Tourette's syndrome, 13 and obsessive-compulsive disorder, 14 among others. It may be useful to investigate the role of the cerebellum in understanding the complex neural circuitry underlying cognition, affect, and behavior in a similar manner. Ultimately, a thorough understanding of this circuitry may lead to improved outcomes for individuals suffering from psychiatric disorders related to these circuits.

                The Cerebellum and Cognition

                Schmahman and Sherman, 15 using bedside cognitive testing as well as neuropsychological testing in a group of 20 patients with isolated cerebellar disease, described a syndrome that included impaired spatial cognition, dysprosody, and anomia, as well as executive dysfunction with difficulties in planning, set-shifting, abstraction, working memory, and verbal fluency. Abnormalities of the posterior cerebellum, especially if bilateral, were particularly associated with these cognitive difficulties. Although this study detailed both bedside cognitive abnormalities and neuropsychological testing in subjects with isolated cerebellar lesions, the patient group was heterogeneous, including patients with various diseases of the cerebellum. Additionally, neuropsychological testing was analyzed by using z-scores, with no control group for comparison. Moderate to severe executive dysfunction was similarly found by Storey et al. 16 in an Australian pedigree of spinocerebellar ataxia. Although this study assessed executive functioning by use of various measures, there were only 5 subjects who completed all of the neuropsychological testing, and a control group was again lacking. Subjects with cerebellar disease have been often found to have “frontal-like” cognitive impairment, with much more variable findings in the areas of visuospatial dysfunction, language, and memory (see more detailed review by Daum and Ackermann 17 ).

                The cerebellum may also be relevant in the cognition of normal subjects without overt cerebellar disease. Cerebellar size has been found to be weakly correlated with memory retention and to show a trend for correlation with general IQ, even when covaried for cerebral volume in normal subjects. 18 The relatively weak associations suggest that the role of the cerebellum in the cognition of normal subjects may well be mediated through the cortical areas with which it is intimately linked. In functional neuroimaging studies of normal subjects, the cerebellum has been seen to activate in tasks involving learning and word generation. 19 These cerebellar effects do not occur in isolation and are rarely the areas of the most robust change, suggesting that the role of the cerebellum in cognitive changes in normal subjects is mediated by cortical areas.

                The Cerebellum and Mood/Behavior

                Apart from its potential role in “coordinating” movement and cognition, the cerebellum may also be implicated in emotional and behavioral control. Schmahman and Sherman 15 found that in their group of patients with isolated cerebellar disease, particularly those with midline and vermal pathology, personality changes of either flattening of affect or disinhibited and inappropriate behavior were common. The lack of standardized measures of these behavioral changes in subjects and the lack of a control group make this conclusion rather tentative. On the other hand, in a controlled study by Kish et al., 20 patients with olivopontocerebellar atrophy had significantly higher depression scores than control subjects, and depression correlated weakly with cognitive testing. Mayberg et al. 21 found that induction of transient sadness in healthy volunteers and patients with depression was associated with increased cerebral blood flow in the cerebellar vermis. However, this was but one of the brain areas found to have changes in cerebral blood flow with induction of sadness, and it is difficult to ascertain the role that the cerebellum plays independently of cortical and limbic changes.

                An earlier study by Heath et al. 22 showed that anterior cerebellar electrode stimulation improved some refractory cases of depression, psychosis, and behavioral problems in patients with diagnoses of schizophrenia, depression, epilepsy, and organic brain syndrome. With the availability of pharmacological treatments, now the mainstay of treatment for depression and schizophrenia, these observations may be seen as historically interesting but of limited practical value. However, the emerging use of transcranial magnetic stimulation, 23 other methods such as vagal stimulation, and stereotactic surgery for refractory cases in psychiatry may refocus attention on this previous observation.

                The Cerebellum in Schizophrenia

                There has been a growing interest in the role of the cerebellum in schizophrenia. An uncontrolled study showed that young male patients with schizophrenia who were on medications but not using alcohol had a preponderance of mild lower-extremity cerebellar signs 24 suggesting cerebellar involvement. Additionally, abnormal smooth-pursuit eye tracking has been found to be more common in schizophrenic patients (off neuroleptics) than in control subjects. 25 The abnormal eye movements may well be related to cerebellar pathology, although it is likely that alternative cortical systems including frontal eye fields were also involved. 26 These studies did not control for cortical involvement.

                Some structural imaging studies have found cerebellar atrophy in schizophrenia, 27–29 but others have failed to replicate this. 30–32 One study in fact showed hyperplasia of the vermis. 33 Differences in both inclusion criteria and imaging methods may have accounted for these differences in the results. More precise MRI volumetric measures will be instrumental in resolving this debate.

                Postmortem pathological studies in schizophrenia have shown smaller vermal area compared with subjects with no psychiatric illness or with other psychiatric illnesses 34 smaller Purkinje cell size 35 and decreased linear density and increased surface density of Purkinje cells compared with age-matched controls. 36 The influence of chronic treatment was not considered in these limited sample studies, nor have they been replicated. Additionally, although the control subjects when living had had no known psychiatric illnesses, they had not been thoroughly screened for the absence of psychiatric problems. Firm conclusions on structural changes of the cerebellum in schizophrenia therefore cannot yet be made.

                A functional neuroimaging study by Volkow et al. 37 suggested that individuals with schizophrenia have lower cerebellar metabolism compared with control subjects. In this study, the subjects with schizophrenia were receiving neuroleptics and the control subjects were not therefore it is unclear whether the cerebellar hypometabolism in the schizophrenic subjects was related to the illness or the medication. Additionally, the role of concomitant cortical changes was not explored. An intriguing new study by Crespo-Facorro et al. 38 of Andreasen's group 39 has suggested that subjects with schizophrenia have less blood flow in the cerebellum than control subjects during the performance of a novel memory task. This group has suggested the presence of a “cognitive dysmetria” in schizophrenia patients that relates to their cerebellar activity, analogous to the motor dysmetrias demonstrated in cerebellar patients. Their findings also suggest involvement of cortical-thalamic-cerebellar loops, since the cerebellum was but one area of altered blood flow, in addition to the frontal cortex, thalamus, and other areas. The role of metabolism or blood flow of the cerebellum in isolation in schizophrenia remains unclear. Validation of the paradigm in subjects with known cerebellar disease will be important for testing the specificity of these findings.

                The Cerebellum in Other Psychiatric Disorders

                With respect to bipolar disorder, there has been some suggestion of cerebellar atrophy in patients with bipolar disorder or mania, 28,40 and another study showed a trend to this effect in patients over the age of 50. 32 The role of alcohol abuse, however, may be a confounder. In one of the studies, 28 only the subjects with concomitant bipolar disorder and alcohol abuse had smaller cerebellar dimensions or vermis than control subjects. The other studies 32,40 did not control for alcohol abuse. Anticonvulsant medication use may be an additional confound.

                Autism has been associated with hypoplasia of lobules VI and VII of the cerebellar vermis in a study by Courchesne et al., 41 although this finding has not been consistently replicated. (A recent review by Courchesne and others 42 has demonstrated that in several MRI studies, patients with autism may have two types of cerebellar pathology—hypoplasia and hyperplasia—of the posterior vermis.) Kates et al. 43 studied a pair of monozygous twins, one of whom met criteria for strictly defined autism and the other of whom showed constrictions in social interaction and play but did not meet these criteria. Smaller cerebellar vermis lobules VI and VII were found in the affected twin compared with the nonaffected twin, further suggesting a role for the cerebellum in autistic disorder however, there were differences in other brain regions as well, making this conclusion tentative. A recent study has shown smaller volumes of the posterior inferior lobe of the cerebellum in children with attention-deficit/hyperactivity disorder than in age-matched control subjects, even adjusting for brain volume and IQ. 44 Adults with Down's syndrome have also been found to have smaller cerebellar volumes than age-matched control subjects, also controlling for total intracranial volume and total brain volume. This difference did not appear to change over time in a small subset of patients followed serially. 45 These studies had the benefit of both a control group and covariate analysis controlling for brain volume. Specificity for symptoms in these disorders is not addressed in these studies, and dissimilarities in clinical presentations across syndromes likewise have not been addressed.

                The Cerebellum in Aging and Dementia

                The cerebellum also appears have relevance to mechanisms in aging and dementia. With aging, a 10% to 40% decrease in Purkinje cell layer 46 and a reduction in the area of the dorsal vermis 47 have been reported, suggesting the possibility that any functions (motor and nonmotor) that are subserved by the cerebellum may be affected to some degree by the aging process. The role of the cell loss in mental or postural stability has not yet been studied. Alcoholic dementia is one of the classic dementias associated with cerebellar atrophy. 48 Although alcoholic dementia is commonly complicated by medical comorbidity, patients with this illness may have more ataxia and stereotypic behavior changes but less overt cortical dysfunction (e.g., less anomia, less deterioration in cognitive status) than do those with Alzheimer's disease (AD). 48 In contrast, Kish et al. 20 found that patients with olivopontocerebellar atrophy (OPCA) demonstrate multiple deficits in intellect, memory, attention, language, and visuospatial and executive functions compared with a control group. It is unclear whether these cognitive skills deteriorate over time in this population and to what extent these subjects had subtle cortical involvements implicating other sites of involvement in the absence of MRI correlation. Thus, although both alcoholic dementia and OPCA are associated with cerebellar abnormalities, it is uncertain how static these deficits are, and specificity remains uncertain because cortical and subcortical areas are also involved.

                The cerebellum is not considered to be a primary focus of pathology in AD. However, diffuse amyloid plaques and increased microglia (but an absence of neurofibrillary tangles) can be found in the cerebellum, usually later in the AD process. 49 Purkinje cell density is decreased, especially in familial AD. 50 Ishii et al. 51 found decreased cerebellar metabolism in severe AD, and this decrease was correlated with Mini-Mental State Examination (MMSE) scores. It is important to note, however, that this association may be an artifact of the temporal and parietal hypometabolism in these same patients, since this correlation was not corrected for cortical hypometabolism. In one autopsy study by Barclay and Brady, 52 gross cerebellar atrophy had been found on CT scan in 2/8 (25%) of subjects with mixed dementia, but in none of 15 subjects with AD or 14 with multi-infarct dementia (diagnoses confirmed at autopsy) in view of these results, cerebellar atrophy on CT was tentatively suggested as a marker for mixed dementia. If replicated, this could be most helpful clinically.

                The cerebellum may be implicated in the behavioral aspects of dementia as well. Gutzmann and Kuhl 53 found that affective lability and emotional incontinence in dementia are associated with cerebellar atrophy, third ventricular width, and interhemispheric fissure width, but not with other measures of cortical atrophy. However, it was unclear how affective lability and emotional incontinence were quantified, despite a clear attempt at attaining a homogeneous sample. Meguro et al. 54 found that wandering in vascular dementia was associated with sparing of the metabolic rate in the cerebellum as well as frontal, left parietal, temporal-parietal-occipital, and left occipital areas of the cortex. This finding only tentatively points to a role of the cerebellum and may be due to reciprocal functional connections between the cerebellar and cortical areas. In contrast to the finding of hypometabolism in the cerebellum in severe AD, 51 Dolan et al. 55 found that patients with cognitive impairment in depression show higher cerebellar blood flow in the vermis and less blood flow in the left medial frontal cortex than depressed patients without cognitive impairment. This effect appears to be related specifically to cognitive dysfunction, since the investigators controlled for depression severity. If this finding is replicated, cerebellar activation may help distinguish between AD and the cognitive impairment of depression.


                Contents

                The CCAS has been described in both adults and children. [3] The precise manifestations may vary on an individual basis, likely reflecting the precise location of the injury in the cerebellum. [4] These investigators [5] subsequently elaborated on the affective component of the CCAS, i.e., the neuropsychiatric phenomena. They reported that patients with injury isolated to the cerebellum may demonstrate distractibility, hyperactivity, impulsiveness, disinhibition, anxiety, ritualistic and stereotypical behaviors, illogical thought and lack of empathy, aggression, irritability, ruminative and obsessive behaviors, dysphoria and depression, tactile defensiveness and sensory overload, apathy, childlike behavior, and inability to comprehend social boundaries and assign ulterior motives. [5]

                The CCAS can be recognized by the pattern of deficits involving executive function, visual-spatial cognition, linguistic performance and changes in emotion and personality. Underdiagnosis may reflect lack of familiarity of this syndrome in the scientific and medical community. The nature and variety of the symptoms may also prove challenging. Levels of depression, anxiety, lack of emotion, and affect deregulation can vary between patients. [6] The symptoms of CCAS are often moderately severe following acute injury in adults and children, but tend to lessen with time. This supports the view that the cerebellum is involved with the regulation of cognitive processes. [8] [9]

                Psychiatric Disorders Edit

                There are a number of psychiatric disorders that are thought to be related to dysfunction of the cerebellum and that appear similar to symptoms of CCAS. [4] It has been suggested that lesions in the cerebellum may be responsible for certain characteristics of psychiatric disorders, such as schizophrenia, depression, bipolar disorder, attention deficit hyperactivity disorder (ADHD), developmental dyslexia, Down syndrome, and Fragile X syndrome. [4] [6] [10] [11] Schmahmann’s dysmetria of thought hypothesis has been applied to these psychiatric disorders. In schizophrenia, it has been suggested that there is dysfunction of the cortical-thalamo-cerebellar circuit, which leads to problems with emotional behaviors and cognition. [12] Supporting this idea are postmortem studies that have shown smaller anterior portions of the vermis [13] and reduced density of the Purkinje cells in the vermis in schizophrenia. [14] There are several pieces of evidence that support the hypothesis that symptoms of some psychiatric disorders are the result of cerebellar dysfunction. One study found that people with schizophrenia had smaller inferior vermis and less cerebellar hemispheric asymmetry than control adults. [14] It has also been found that individuals with ADHD have smaller posterior inferior lobes than a control group. [15] Other studies have suggested that the size of the vermis is correlated with the severity of ADHD. A study of people with dyslexia showed lower activation via positron emission tomography (PET) in the cerebellum during a motor task relative to a control group. [16] It may be possible to further understand the pathology of these psychiatric disorders by studying CCAS.

                The causes of CCAS lead to variations in symptoms, but a common core of symptoms can be seen regardless of etiology. Causes of CCAS include cerebellar agenesis, dysplasia and hypoplasia, cerebellar stroke, tumor, cerebellitis, trauma, and neurodegenerative diseases (such as progressive supranuclear palsy and multiple system atrophy). CCAS can also be seen in children with prenatal, early postnatal, or developmental lesions. [3] In these cases there are lesions of the cerebellum resulting in cognitive and affect deficits. The severity of CCAS varies depending on the site and extent of the lesion. In the original report that described this syndrome, patients with bihemispheric infarction, pancerebellar disease, or large unilateral posterior inferior cerebellar artery (PICA) infarcts had more cognitive deficits than patients with small right PICA infarcts, small right anterior interior cerebellar artery infarcts or superior cerebellar artery (SCA) territory. Overall, patients with damage to either the posterior lobe of the cerebellum or with bilateral lesions had the greatest severity of symptoms, whereas patients with lesions in the anterior lobe had less severe symptoms. [2] In children, it was found that those with astrocytoma performed better than those with medulloblastoma on neuropsychological tests. [3] When diagnosing a patient with CCAS, medical professionals must remember that CCAS has many different causes.

                Cerebellar pathways Edit

                There are pathways that have been proposed to explain the non-motor dysfunctions seen in CCAS. A leading view of CCAS is the dysmetria of thought hypothesis, which proposes that the non-motor deficits in CCAS are caused by dysfunction in the cerebrocerebellar system linking the cerebral cortex with the cerebellum. [2] [7] The normal cerebellum is now thought to be responsible for regulating motor, cognitive and emotional behaviors. When there is some type of damage to the cerebellum, this regulation is affected, leading to deregulation of emotional behaviors. This effect has been compared to dysmetria of movement, which describes the motor dysfunctions seen after cerebellar lesions. [17] These ideas build upon earlier theories and results of investigations indicating that the cerebellum is linked with the frontal orbital cortex, limbic system, and reticular structures. It was proposed that these circuits are involved with emotional regulation, such that damage to this circuit would result in behavioral dysfunctions such as hyperactivity, apathy, and stimulus-seeking behaviors. [18]

                Connections lead from the cerebral cortex (including sensorimotor regions as well as cognitively relevant association areas and emotion-related limbic areas) to the cerebellum by a two-stage feedfoward system. The pathway starts in the layer V neurons of the cerebral cortex that project via the cerebral peduncle to the neurons of the anterior portion of the pons (the basis pontis). The pontine axons projects via the contralateral middle cerebellar peduncle, terminating in the cerebellar cortex as mossy fibers. The feedback circuit from the cerebellum to the cerebral cortex is also a two-stage system. The cerebellar cortex projects to the deep cerebellar nuclei (the corticonuclear microcomplex). The deep nuclei then project to the thalamus, which in turn projects back to the cerebral cortex. [5] This cerebrocerebellar circuit is key to understanding the motor as well as the non-motor roles of the cerebellum. The relevant cognitive areas of the cerebral cortex that project to the cerebellum include the posterior parietal cortex (spatial awareness), the supramodal areas of the superior temporal gyrus (language), the posterior parahippocampal areas (spatial memory), the visual association areas in the parastriate cortices (higher-order visual processing), and the prefrontal cortex (complex reasoning, judgment attention, and working memory). There are also projections from the cingulate gyrus to the pons. [5] The organization of these anatomical pathways helps clarify the role the cerebellum plays in motor as well as non-motor functions. The cerebellum has also been shown to connect brainstem nuclei to the limbic system with implications for the function of the neurotransmitters serotonin, norepinephrine, and dopamine and the limbic system. [19] The connection with the limbic system presumably underlies the affective symptoms of CCAS.

                Cerebellar anatomy Edit

                It has been suggested that specific parts of the cerebellum are responsible for different functions. Mapping of the cerebellum has shown that sensorimotor, motor, and somatosensory information is processed in the anterior lobe, specifically in lobules V, VI, VIII A/B. The posterior lobe (notably cerebellar lobules VI and VII) is responsible for cognitive and emotional functions. Lobule VII includes the vermis in the midline, and the hemispheric parts of lobule VIIA (Crus I and Crus II), and lobule VIIB). This explains why CCAS occurs with damage to the posterior lobe. [20] In the study of Levisohn et al. [3] children with CCAS showed a positive correlation between damage to the midline vermis and impairments in affect. The authors hypothesized that deficits in affect are linked to damage of the vermis and fastigial nuclei, whereas deficits in cognition are linked to damage of the vermis and cerebellar hemispheres. These notions were consistent with the earlier suggestion (by psychiatrist Robert G. Heath [21] ), that the vermis of the cerebellum is responsible for emotional regulation. The deep nuclei of the cerebellum also have specific functions. The interpositus nucleus is involved with motor function, the dentate nucleus with cognitive functions, and the fastigial nucleus with limbic functions. [5] It has been shown that phylogenetically the dentate nuclei developed with the association areas of the frontal cortex, [22] supporting the view that the dentate nucleus is responsible for cognitive functions.

                Lateralization Edit

                There have been studies that show laterality effects of cerebellar damage with relation to CCAS. Language in the cerebellum seems to be contralateral to the dominant language hemisphere in the frontal lobes, meaning if the language is dominant in the left hemisphere of the frontal lobes, the right side of the cerebellum will be responsible for language [23] (see Tedesco et al. [24] for a discussion of lack of lateralization). Lateralization is also observed with visuospatial functions. One study found that patients with left cerebellar lesions performed more poorly on a visuospatial task than did patients with right cerebellar lesions and healthy control adults. [25] It has also been shown that lesions of the right cerebellum result in greater cognitive deficits than lesions of the left hemisphere. [26]

                The current treatments for CCAS focus on relieving the symptoms. One treatment is a cognitive-behavioral therapy (CBT) technique that involves making the patient aware of their cognitive problems. For example, many CCAS patients struggle with multitasking. With CBT, the patient would have to be aware of this problem and focus on just one task at a time. This technique is also used to relieve some motor symptoms. [5] In a case study with a patient who had a stroke and developed CCAS, improvements in mental function and attention were achieved through reality orientation therapy and attention process training. Reality orientation therapy consists of continually exposing the patient to stimuli of past events, such as photos. Attention process training consists of visual and auditory tasks that have been shown to improve attention. The patient struggled in applying these skills to “real-life” situations. It was the help of his family at home that significantly helped him regain his ability to perform activities of daily living. The family would motivate the patient to perform basic tasks and made a regular schedule for him to follow. [26]

                Transcranial magnetic stimulation (TMS) has also been proposed to be a possible treatment of psychiatric disorders of the cerebellum. One study used TMS on the vermis of patients with schizophrenia. After stimulation, the patients showed increased happiness, alertness and energy, and decreased sadness. Neuropsychological testing post-stimulation showed improvements in working memory, attention, and visual spatial skill. [27] Another possible method of treatment for CCAS is doing exercises that are used to relieve the motor symptoms. These physical exercises have been shown to also help with the cognitive symptoms. [28]

                Medications that help relieve deficits in traumatic brain injuries in adults have been proposed as candidates to treat CCAS. Bromocriptine, a direct D2 agonist, has been shown to help with deficits in executive function and spatial learning abilities. Methylphenidate has been shown to help with deficits in attention and inhibition. Neither of these drugs has yet been tested on a CCAS population. [10] It may also be that some of the symptoms of CCAS improve over time without any formal treatment. In the original report of CCAS, four patients with CCAS were re-examined one to nine months after their initial neuropsychological evaluation. Three of the patients showed improvement in deficits without any kind of formal treatment, though executive function was still found to be one standard deviation below average. In one patient, the deficits worsened over time. This patient had cerebellar atrophy and worsened in visual spatial abilities, concept formation, and verbal memory. [2] None of these treatments were tested on a large enough sample to determine if they would help with the general CCAS population. Further research needs to be done on treatments for CCAS.

                There is much research that needs to be conducted on CCAS. A necessity for future research is to conduct more longitudinal studies in order to determine the long-term effects of CCAS. [3] One way this can be done is by studying cerebellar hemorrhage that occurs during infancy. This would allow CCAS to be studied over a long period to see how CCAS affects development. [5] It may be of interest to researchers to conduct more research on children with CCAS, as the survival rate of children with tumors in the cerebellum is increasing. [3] Hopefully future research will bring new insights on CCAS and develop better treatments.


                Complications

                Patients whose cerebellar degeneration is a result of a tumor, for example paraneoplastic cerebellar degeneration, typically have a poor prognosis. The tumors tend to progress quickly and often fatal.

                Although uncommon, there have been some reports of sleep disturbances associated with cerebellar degeneration. It is thought that this may be a result of unregulated eye movements in REM sleep.

                Patients sometimes experience strained relationships with family and friends. Lack of coordination in muscles of facial expression makes conveying emotion difficult and can impair communication.

                Highlights

                Overall, cerebellar degeneration presents with decreased muscle tone and loss of coordination in both skeletal and smooth muscle tissue. The group of disorders associated with progressive degeneration of cerebellum is Degenerative cerebellar ataxia. In general there is wide legged and unsteady walk with tremors in the trunk of the body and jerky movements of the arms or legs. Patients may also exhibit slow and slurred speech nystagmus is also a feature commonly seen. More specific symptoms reflect the region of the cerebellum that is degenerating.

                • Spinocerebellum
                  • Truncal ataxia
                  • “drunken” gait
                  • Ataxia of limbs
                  • Jerky voluntary muscle movements
                  • Loss of coordination
                  • Dysmetria - difficulty judging distance, may overshoot objects when reaching
                  • Dysdiadochokinesia - inability to perform rapidly changing actions, for example turning a door handle
                  • Rebound phenomena
                  • Intention tremor
                  • Equilibrium is affected
                  • Nystagmus - involuntary eye movements

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