Cerebellar Disorders PDF

Cerebellar Disorders Dr Galit Seligmann 17 May 2024 Content Anatomy of the cerebellum Cerebellar circuits Clinical examination and signs Localisation of lesions Approach to aetiology Investigations Cerebellum “Little brain” à half neurons in the CNS are in this st...

Cerebellar Disorders Dr Galit Seligmann 17 May 2024 Content Anatomy of the cerebellum Cerebellar circuits Clinical examination and signs Localisation of lesions Approach to aetiology Investigations Cerebellum “Little brain” à half neurons in the CNS are in this structure Integrates sensory and other inputs from brain, vestibular organs and spinal cord to coordinate movement and for motor planning Control signals to correct between intent and action Situated in posterior fossa 1. Anatomy of Cerebellum 3 lobes 1. Anterior (spinocerebellum à posture, trunk & limbs) 2. Posterior (cerebrocerebellum à planning and non motor function) 3. Floculonodular (vestibulocerebellum à balance with head and eye movement) Spinocerebellum receives somatic information from mechanoreceptors which innervate muscle in trunk and limb Dorsal spinocerebellar tract originates from Clarke’s nucleus and transmits sensory info from leg and lower trunk to cerebellar nuclei and cortex Cuneocerebellar tract from accessory cuneate nucleus which transmits info from arm and upper trunk Friedreich’s ataxia causes degeneration here 1. Anatomy of the Cerebellum 3 lobes 1. Anterior (spinocerebellum à posture, trunk & limbs) 2. Posterior (cerebrocerebellum à planning and non motor function) 3. Floculonodular (vestibulocerebellum à balance with head and eye movement) Cerebrocerebellum involved in planning of movement and connects with areas of the cerebral cortex Major input = contralateral cerebral cortex from motor and sensory areas via ipsilateral pontine nuclei Working memory and higher functioning Vestibulocerebellum crucial for gaze through combined eye/head movements Major input = primary vestibular afferents  Anatomy of the Cerebellum Cerebellar peduncles 3 peduncles 1. Superior à midbrain Majority efferent 2. Middle à pons Majority afferent 3. Inferior à medulla Anatomy of the Cerebellum 4 Cerebellar nuclei Multipolar Input from cerebellar cortex and other parts of CNS Axons form the cerebellar peduncles Lateral à medial “Don’t Eat Greasy Foods” Dentate à Emboliform à Globose à Fastigial  Anatomy of the Cerebellum Functional zones 1. Lateral zone à dentate 2. Intermediate/paramedian à emboliform and globose 3. Vermal à fastigial Anatomy of the Cerebellum Functional zones 1. Lateral zone 2. Intermediate/paramedian 3. Vermal  2. Cerebellar circuits Two inputs: Climbing fibres and mossy fibres which project to deep nuclei and cortex Climbing fibres are from inferior olivary nucleus which synapse on Purkinje cells and generate a cerebellar output signal via deep nuclei Vestibular nuclei have similar inputs from both climbing fibres and Purkinje cells Mossy fibres have excitatory and inhibitory interneurons  3. Clinical Exam (headàtoe) Eye Signs Nystagmus: Rhythmic regular oscillation of the eyes. It may consist of alternating phases of a slow drift in one direction with a corrective quick "jerk" in the opposite direction, or of slow, sinusoidal, "pendular" oscillations to and fro. 2 phases: eye drifts away from target, then a movement towards to target Jerk or pendular? à describe according to the fast phase Horizontal or vertical or rotational? Frequency and amplitude? Opsoclonus: bilateral conjugate gaze disorder that is rapid with no intersaccadic interval and is of high speed, similar to flutter Square wave jerk: saccade occurs during horizontal gaze Cool video: https://www.youtube.com/watch?v=HXOaRGNnijU Peripheral vs Central Nystagmus Localisation Nystagmus  3. Clinical Exam Titubation Involuntary nodding of head and neck which is semirhythmic Vertigo Speech: ataxic dysarthria Cerebellar ‘staccato’ speech à alternating loudness and fluctuating pitch levels, emphasis is placed on syllables that should not be stressed. Scanning speech, which refers to slow enunciation with pauses in between syllables and words.  Clinical Exam Intention tremor Increases as finger approaches target Dysmetria Upper limb = past pointing Lower limb = heel to shin Ask the patient to make a circular movement, with the heel raised off the shin once it has reached the ankle, before placing it on the knee again. Simply gliding one heel up and down the opposite shin will miss early ataxia Dysdiadochokinesis Difficulties with making rapid alternating movements, such as pronation- supination  Clinical Exam Rebound phenomenon The patient is asked to maintain his arms in the outstretched position with eyes closed. Downward pressure is applied to the arms and is released suddenly. In a cerebellar syndrome, the arms will shoot upward when pressure is released and will oscillate before returning to the original position. The cerebellum functions as a calibrator of forces, and dysfunction results in the generation of inappropriate muscle forces to fix the limb in a particular position Hypotonia of arms and legs Pendular reflexes: the movement elicited by percussion is not dampened, resulting in swinging back and forth of the limb. Failure of calibration of muscle forces, resulting in abnormal ‘dampening.’  Other important examination Demyelination: RAPD, INO Spinocerebellar ataxias: variety of additional Space-occupying lesion à especially if signs, including UMN and extrapyramidal unilateral or asymmetrical signs, do cranial nerve examination to exclude CP angle tumour signs, peripheral neuropathy, and Alcoholic degeneration history of ophthalmoplegia alcohol intake with CAGE questionnaire, Friedreich ataxia: ataxia with peripheral clinical features of alcohol use neuropathy, spasticity, optic atrophy, diabetes Drugs: e.g., carbamazepine, phenytoin (gum mellitus, hypertrophic CMO and deafness examination), and barbiturates. Ataxia-telangiectasia: skin and eye Metabolic: B12, copper, or vitamin E telangiectasia, dystonia and chorea; deficiency (may also cause sensory ataxia) autosomal recessive inheritance. Hypothyroidism Weight gain, mood, sleep, bowel habit Von Hippel–Lindau syndrome with Nutritional: Celiac disease à history of cerebellar haemangioblastomas diarrhoea, GI symptoms Multiple system atrophy with predominant Paraneoplastic: clubbing, masses, weight loss cerebellar features 4. Localising lesion Typically causes ataxia which is: 1. Ipsilateral to side of lesion 2. Midline lesions cause truncal ataxia, wide based gait and eye movement abnormalities accompanied by vertigo, nausea and vomiting 3. Lateral lesions cause appendicular ataxia (i.e. ataxia of limbs) Note: due to multiple cerebellar inputs, ataxia can be seen in disorders of other locations Clinical Exam – sensory ataxia? Look for evidence of a sensory rather than cerebellar ataxia: positive Romberg’s test or pseudoathetosis (apparent writhing of fingers of outstretched hands when eyes are closed, due to proprioceptive impairment). If suspected, assess proprioception and distal weakness of a peripheral neuropathy Localising lesion Midline lesions Hemispheric cerebellar dysfunction Vermis, the fastigial and interposed nuclei, the flocculus and nodulus and the paravermis/intermediate zone. Motor planning and coordination of complex tasks. Motor execution, rapid and slow eye movements, Ipsilateral signs balance/lower extremity coordination, and vestibular function. Dysdiadochokinesis Imbalance – wide based gait Dysmetria Truncal ataxia Limb ataxia difficulty with coordinated tasks. Titubation Intention tremor Lower-limb dysmetria Ataxic dysarthria Saccadic intrusions Ocular findings – Ocular findings are generally less prominent but Nystagmus – Horizontal gaze-evoked nystagmus is commonly broken smooth pursuits and ipsilateral gaze-evoked nystagmus are seen with midline cerebellar injury. More prominent when often seen. looking towards the side of the lesion. Ocular dysmetria à hypermetric saccadic eye movements. After overshooting, the eyes rapidly correct their position to focus. Vertigo Approach to diagnosis Acute vs subacute vs chronic à better for POC purposes Acquired or inherited à better for exam purposes Useful Approach Onset? Age at onset Family history Other conditions Minutes -