Shortened cortical silent period in facial muscles of patients with cranial dystonia.
OBJECTIVE
To study the cortical silent period (SP) in the orbicularis oculi and perioral muscles in 23 patients with cranial dystonia and 10 age-matched control subjects.


METHODS
High-intensity magnetic stimuli were delivered with a round coil centered at the vertex during a maximal muscle contraction. Electromyographic (EMG) responses were recorded from surface electrodes placed over the orbicularis oculi and perioral muscles.


RESULTS
SPs elicited in upper and lower facial muscles had a similar duration. Facial muscle SPs were significantly shorter in patients than in control subjects. Patients with blepharospasm plus oromandibular dystonia had shorter SPs than patients with blepharospasm alone. Although patients' recordings showed reduced voluntary and evoked EMG activity, neither activities correlated with the duration of the SP.


CONCLUSIONS
Silent period (SP) shortening depends neither on the level of electromyographic activity nor on segmentary mechanisms. The shortened SP in facial muscles reflects hypoexcitability of cortical inhibitory neurons in cranial dystonia.
Currà
A
A
Dipartimento di Scienze Neurologiche, Istituto Neurologico Mediterraneo Neuromed, Pozzilli, Isernia, Italy.
Romaniello
A
A
Berardelli
A
A
Cruccu
G
G
Manfredi
M
M
D000328:Adult; D000368:Aged; D001764:Blepharospasm / Q000503:physiopathology; D002540:Cerebral Cortex / Q000503:physiopathology*; D020821:Dystonic Disorders / Q000503:physiopathology*; D004576:Electromyography; D005152:Facial Muscles / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D008410:Masticatory Muscles / Q000503:physiopathology; D008538:Meige Syndrome / Q000503:physiopathology; D008875:Middle Aged; D009055:Mouth / Q000503:physiopathology; D015999:Multivariate Analysis; D010812:Physical Stimulation