Pure cerebellar syndromes are rare. Cerebellar symptoms are frequently associated with brain stem dysfunction because of the cerebellum's close neighborhood to the brain stem. Vascular disorders frequently damage the cerebellum and brain stem together because all cerebellar arteries supply cerebellar as well as brain stem structures. Degenerative cerebellar disorders are frequently accompanied by pyramidal and extrapyramidal symptoms. Cerebellar symptoms might be mimicked by frontal lobe lesions.
Cerebral. Frontal signs include motor abnormalities, impairment of cognitive function, and changes in personality. There are important anatomical connections between the contralateral frontal lobe and ipsilateral cerebellum. Therefore, frontal lobe disorders might cause cerebellar-like symptoms with walking difficulties and clumsiness. However, frontal lobe tumors commonly start with mental symptoms. Cognitive dysfunction accompanies some degenerative ataxic disorders. Incontinence associated with dementia and gait ataxia suggests normal pressure hydrocephalus.
Cranial Nerves. The history of previous subacute monocular visual loss suggests a diagnosis of multiple sclerosis. Some degenerative ataxias are associated with gradual visual loss due to retinitis pigmentosa. Diplopia, facial numbness, facial droop, vertigo, or hearing loss resulting from associated cranial neuropathies (cranial nerves III, IV, V, VI, VII, and VIII) associated with ataxia suggest a disorder in the brain stem. Tumors of the cerebellopontine angle, such as acoustical neurinomas, are frequently associated with nerve palsies of cranial nerves V, VII, and VIII.
Motor/Reflexes/Gait. A slight loss of muscular power and increased fatigability of muscles may occur with acute cerebellar disorders. However, paresis associated with increased muscular tone, hyperreflexia, and extensor plantar reflexes (Babinski's sign) suggest an additional involvement of upper motor neurons (corticospinal or pyramidal syndrome). Paresis accompanied with atrophy, hypotonia, and loss of tendon reflexes (areflexia) suggests the involvement of the lower motor neuron and is usually associated with polyneuropathy, for example in Friedreich's ataxia. Several demyelinating neuropathies may give rise to prominent tremor and sensory ataxia, which might be confused with cerebellar ataxia, such as the demyelinating type of hereditary motor and sensory neuropathy, chronic inflammatory and paraproteinemic neuropathies, and Refsum's disease. In these cases, ataxia is improved by visual feedback. The Miller-Fisher variant of Guillain-Barre syndrome may present with cerebellar ataxia of subacute onset, usually associated with arreflexia, ophthalmoplegia, and facial weakness.
Rigidity, akinesia, and static tremor suggest parkinsonism and are associated with multiple system atrophy. Abnormal involuntary movements might occur in cerebellar disorders. Powerful but brief involuntary movements at the beginning of the movement are due to intention myoclonus, not tremor, and occur in diseases involving the dentate nucleus or the superior cerebellar peduncle. Palatal tremor occurs in lesions of the inferior olive in the brain stem or dentatoolivary pathway. Hemiballism and chorea are associated with basal ganglia disorders.
Sensory. Pure cerebellar lesions do not cause disturbances in sensation. Hemianesthesia involving one side of the body suggests an additional lesion of the contralateral parietal lobe. Crossed sensory disturbances with a loss of pain on one side of the face and on the opposite side of
the body are common in patients with a brain stem lesion. Symmetrical sensory impairment over the feet, legs, and hands associated with reflex loss and various degrees of paresis suggests peripheral neuropathy. Peripheral neuropathies are frequently associated with degenerative cerebellar disorders.
Autonomic Nervous System. Horner's syndrome (miosis, ptosis, and retraction of the eyeball) and ipsilateral dysautonomia (increased skin temperature due to vasomotor paralysis and anhidrosis due to impaired sudomotor function) associated with cerebellar ataxia suggest an additional brain stem lesion. Postural hypotension is associated with multiple system atrophy. Urgency of micturition is common in multiple sclerosis and might be present in degenerative ataxic disorders.
Neurovascular. Fundal examination may disclose diabetic, hypertensive, or atherosclerotic retinal changes. Auscultation of the mastoid may reveal a bruit in a patient with stenosis of a vertebrobasilar artery or vascular malformation. A carotid or subclavian bruit might be heard in a patient with symptomatic artherosclerotic disease of the vertebrobasilar arteries. A reduced radial pulse and blood pressure suggests subclavian stenosis and might be associated with subclavian steal syndrome.
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