Broadened Friedreich's ataxia phenotype after gene cloning. Minimal GAA expansion causes late-onset spastic ataxia.

We describe three siblings from an Italian family affected by an autosomal recessive spinocerebellar degeneration. Gait ataxia, presenting between 38 and 45 years, was the first symptom in all three patients. Dysarthria, dysmetria, brisk tendon reflexes, extensor plantar response, and scoliosis were constant features. Disease progression was slow. Electrophysiologic studies demonstrated a slight reduction in sural nerve sensory action potential in only one patient. Analysis of GAA expansion within the X25 gene showed that patients were homozygous for the expansion, with the shorter expanded allele ranging from 120 to 156 triplets. The size of the GAA expansion may be smaller than we previously described. Such minimal expansions may result in atypical forms of Friedreich's ataxia.

The abnormality of N30 somatosensory evoked potential in idiopathic Parkinson's disease is unrelated to disease stage or clinical scores and insensitive to dopamine manipulations.

We recorded short latency somatosensory evoked potentials (SEPs) to median nerve stimuli in 40 patients affected by idiopathic Parkinson's disease (PD) classified from I to IV on the Hoehn and Yahr disability scale. SEPs were recorded before and after chronic administration of L-Dopa and bromocriptine, before and after acute administration of L-Dopa. Fourteen patients experiencing wearing off and dystonic-dyskinetic disturbances were recorded during the occurrence of these oscillations of their clinical status. Absent or reduced N30 components were found in 32.5% of patients. SEPs were not modified by acute or chronic administration of L-Dopa or bromocriptine or during off and dystonic or dyskinetic conditions. Multiple correlations of N30 with scores of the Unified Parkinson's Disease Rating Scale showed that N30 abnormality did not classify patients with prominent clinical features, nor did it predict the outcome of treatment.