Prolonged cortical silent period but normal sensorimotor plasticity in spinocerebellar ataxia 6

Mov Disord. 2008 Feb 15;23(3):378-85. doi: 10.1002/mds.21847.


Spinocerebellar ataxia 6 (SCA6) is a hereditary disease characterized by a trinucleotide repeat expansion in the CACNA1A gene and late-onset bilateral cerebellar atrophy. It is unclear if there is significant pathology outside of the cerebellum. We used transcranial magnetic stimulation to assess sensorimotor cortical circuits and cortical plasticity in 8 SCA6 patients and 8 age-matched controls. Behavioral performance was assessed using a rhythmic tapping task. Neurophysiological measures of SCA6 patients showed a prolonged cortical silent period (CSP) but normal MEP recruitment curve, short-latency afferent inhibition, long-latency afferent inhibition and ipsilateral silent period. Paired-associative stimulation induction also increased motor-evoked potentials normally. SCA6 patients had greater variability with cued rhythmic tapping than normals and deteriorated when the cue was removed; in comparison, normal subjects had similar variability between cued and uncued rhythmic tapping. Analysis using a Wing-Kristofferson timing model indicated that both clock variance and motor delay variance were abnormal. Conclusion. In SCA6, the circuits for sensorimotor integration and the mechanisms for LTP-like plasticity in the sensorimotor cortex are unimpaired. A prolonged CSP in SCA6 just like in other cerebellar atrophies would suggest that this neurophysiological change typifies cerebellar dysfunction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Case-Control Studies
  • Electric Stimulation / methods
  • Evoked Potentials, Motor
  • Evoked Potentials, Somatosensory
  • Female
  • Humans
  • Male
  • Middle Aged
  • Motor Cortex / physiopathology*
  • Neural Inhibition / physiology
  • Neural Inhibition / radiation effects
  • Neuronal Plasticity*
  • Reaction Time
  • Somatosensory Cortex / physiopathology*
  • Spinocerebellar Ataxias / pathology*
  • Spinocerebellar Ataxias / physiopathology*
  • Transcranial Magnetic Stimulation / methods