Cerebellar Ataxia Type 1
Spinocerebellar ataxia-type 1 (SCA1) was the first dominantly inherited ataxia for which the locus and gene defect were identified. SCA1 is caused by polyQ-encoding CAG repeat expansions resulting in production of the abnormal protein, Ataxin-1. Similar to other polyQ diseases, SCA1 shows considerable phenotypic variability and anticipation that reflects differences in repeat size among affected individuals. Most patients present in the fourth decade with a pancerebellar syndrome including ataxia of gait, stance, and limbs and dysarthria. Oculomotor abnormalities include gaze-evoked nystagmus, saccadic hypermetria, breakdown of smooth pursuit eye movements, and reduced opticokinetic nystagmus. In most patients, there are additional noncerebellar signs. Spasticity with extensor plantar responses and hyperreflexia occur in more than 50% of SCA1 patients.
KeywordsCerebellar Ataxia Vocal Cord Paralysis SCA1 Patient Repeat Size Important Clinical Problem
The patient is being examined for cerebellar signs. He is able to walk independently but unsteadily. His gait is slightly wide-based. He performs tandem gait with difficulty with a tendency to veer to the right. Tandem stance and heel-knee-shin testing are normal. Speech is slow and dysarthric with a monotonous low-pitch tone. (Video contribution from Dr. Susan Perlman, Department of Neurology at David Geffen School of Medicine at UCLA.)
Exam of patient w SCA.mp4(MP4 35,988KB)