Clinical picture of spinocerebellar ataxia type I (SCA1)

: Spinocerebellar ataxia is a group of diseases with autosomal dominant inheritance heterogenous both clinically and genetically. So called dynamic mutations underlie most these nosological units. The clinical patterns of various SCA types have not yet been defined completely. The purpose of the present report was description of the typical symptoms and signs of type 1 SCA. Seventeen patients from 13 families (M-2, F-15) were studied clinically in detail. The diagnosis was confirmed by DNA analysis. The assessment included neurological status, cognitive functions, the results of EEG, EMG, SEP, VEP, BAER and MRI examinations. The pedigrees indicated autosomal dominant inheritance pattern. The mean age at onset was 35.5 +/- 6.8 years (range 23-45 years) and it suggested negative correlation with the number of CAG repetitions. Cerebellar syndrome limb and truncal, ataxia and dysarthria was present in all cases. Six patients had nystagmus, 3 had slow saccades, 2 had gaze limitation upward, and lateral and 6 had dysphagia. Signs of pyramidal system involvement were found in 10 cases, one had athetotic movements, one had orthostatic hypotension. Two patients had dementia features, 9 had some decline of intellectual functions, mainly with difficulties of memorization, learning and concentration. In 16 cases MRI demonstrated vermis atrophy and atrophy of cerebellar hemispheres, 14 had fourth ventricle dilatation, 8 had flattening of pons base, 8 had narrowing of cervical spinal cord, 8 had dilated CSF spaces over frontal lobes and in 6 cases lateral ventricles were dilated. Electrophysiological peripheral nervous system investigations showed in 16 cases long-standing damage to the motor and sensory peripheral neurons at the level of nerve trunks, more pronounced in sensory nerves. In 13 cases peripheral neuron damage was subclinical. SEP showed in all patients disturbed function of ascending sensory pathways at peripheral and spinocortical levels.