Prolonged cortical silent period but normal sensorimotor plasticity in spinocerebellar ataxia 6.
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.
Teo
James T H
JT
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom. jteo@ion.ucl.ac.uk
Schneider
Susanne A
SA
Cheeran
Binith J
BJ
Fernandez-del-Olmo
Miguel
M
Giunti
Paola
P
Rothwell
John C
JC
Bhatia
Kailash P
KP
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004558:Electric Stimulation / Q000379:methods; D019054:Evoked Potentials, Motor; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology / Q000528:radiation effects; D009473:Neuronal Plasticity; D011930:Reaction Time; D013003:Somatosensory Cortex / Q000503:physiopathology*; D020754:Spinocerebellar Ataxias / Q000473:pathology* / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods