The prolonged cortical silent period in patients with Huntington's disease.
OBJECTIVE
In a group of patients with Huntington's disease and age-matched controls, we studied the cortical silent period (SP) elicited by single transcranial magnetic stimulation (TMS) pulses.


METHODS
We measured the area of the pre-stimulus electromyographic (EMG) activity, the area of the motor evoked potentials (MEPs) and the duration of the SP induced by stimuli delivered at an intensity of 150% of motor threshold with a round coil placed over the vertex. We determined the cortical SP by sampling only the 5 traces containing the shortest SPs and by collecting 10 consecutive unselected traces without selecting trials.


RESULTS
Patients and controls had normal EMG background areas, and MEP latencies and areas. Whereas data measured from selected trials gave a normal duration of the SP (patients, 154+/-58 ms; controls, 166+/-22 ms), data from unselected trials yielded a significantly longer SP duration in patients than in controls (356+/-251 vs. 159+/-44 ms) and also a larger variance and range.


CONCLUSIONS
We conclude that in Huntington's disease, an abnormal cortical SP is best sought by collecting unselected consecutive traces. We suggest that the prolonged SP in HD originates from a dysfunction of the mechanisms controlling the restart of voluntary movement after TMS.
Modugno
N
N
Dipartimento di Scienze Neurologiche, Università di Roma 'La Sapienza', Viale dell'Università 30, 00185, Rome, Italy.
Currà
A
A
Giovannelli
M
M
Priori
A
A
Squitieri
F
F
Ruggieri
S
S
Manfredi
M
M
Berardelli
A
A
D000328:Adult; D000368:Aged; D004558:Electric Stimulation; D004576:Electromyography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D006816:Huntington Disease / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009046:Motor Neurons / Q000502:physiology*