Seven years earlier, this 75-year-old woman was just about to descend some concrete steps when she hesitated because of poor balance. Since then, she felt increasing need to hold onto the rails or walls for support. Sometimes, she made sure that both feet were on one step at the same time, but in doing so, she still felt she was rocking back and forth.

This 75-year-old woman had a 7-year history of slowly progressive ataxia, mild sensory loss, and downbeat nystagmus. Finger-to-nose testing showed a very mild symmetric endpoint tremor, left greater than right, but no overt dysmetria. Heel-shin testing was mildly abnormal bilaterally. Rapid alternating movements were decreased bilaterally. Sensory examination showed decreased sensation to pinprick in both hands and feet. She had a wide-based stance, could not stand unassisted, and had to use a walker to ambulate.

Identification of the type of cerebellar syndrome could predict a probable etiology. Four cerebellar syndromes are recognized: hemispheric syndrome, rostral vermis syndrome, caudal vermis syndrome, and pancerebellar syndrome. The cerebellar hemisphere syndrome (ipsilateral appendicular greater than truncal ataxia) often results from acute ischemic or hemorrhagic vascular events, trauma, neoplasms, or abscess. The rostral vermis syndrome (truncal ataxia with wide-based stance and gait but relatively minor or no dysmetria on heel-to-shin testing) results from alcoholism or nutritional deficiencies. The caudal vermis syndrome (truncal ataxia with staggering but rarely wide-based gait and little if any limb ataxia) often results from a midline cerebellar neoplasm such as medulloblastoma, ependymoma, or astrocytoma. The pancerebellar syndrome usually results from vitamin deficiencies (e.g., vitamin E), toxic/metabolic disorders, and demyelinating, immune-mediated, paraneoplastic, or hereditary (autosomal recessive, autosomal dominant, or X-linked ataxias) or nonhereditary degenerative ataxias (e.g., multiple system atrophy [MSA], cerebellar type). Besides the spectrum of hereditary cerebellar ataxias, other inheritable genetic or metabolic causes include abetalipoproteinemia, ataxia telangiectasia, adrenoleukodystrophy, ataxia with Co-Q deficiency, late-onset G_M2 gangliosidoses, mitochondrial diseases, sialidosis, maple syrup urine disease, organic acidurias, cerebrotendinous xanthomatosis (CTX), Refsum disease, Wilson disease, and Niemann-Pick type C.