Multimodal electrophysiologic follow-up study in 3 mutated but presymptomatic members of a spinocerebellar ataxia type 1 (SCA1) family.

ABSTRACT

The objective was to determine the progression of nervous system involvement in spinocerebellar ataxia type 1 (SCA1). Three presymptomatic members of an Italian SCA1 family underwent molecular analysis and showed the SCA1 mutation. They were defined as "at risk/mutated" individuals. A clinical and electrophysiologic 7-9 year follow-up was performed. The Inherited Ataxia Progression Scale was used for clinical staging. Sensory and motor conduction velocities, somatosensory evoked potentials and transcranial magnetic stimulation were performed at least three times in each subject. Clinical examination showed the early corticospinal pathway involvement. Electrophysiologic investigations confirmed that at the asymptomatic stage only magnetic motor cortex stimulation was abnormal and rapidly worsened with time. Somatosensory pathway studies showed a later involvement and a light sensory-motor neuropathy was the last electrophysiologic abnormality to be recognised. These data confirm that SCA1 phenotype is characterised by early and prevalent pyramidal tract involvement and that peripheral neuropathy is a late and moderate complication.