Cortical silent period in patients with amyotrophic lateral sclerosis.
Transcranial magnetic stimulation (TMS) during a muscle contraction induces a motor-evoked potential (MEP) in the skeletal muscle followed by a cessation of EMG activity, the cortical silent period (C-SP). The C-SP is a useful parameter to indicate the activation of the motor system. Accurate determination of the C-SP can be important in amyotrophic lateral sclerosis (ALS), a progressive disorder of unknown etiology characterised by degeneration of upper and lower motor neurons. The aim of this study was to evaluate the sensitivity of C-SP as an index of motor system involvement, in ten patients affected by ALS, with a mean duration of the disease: 5. 5+/-3.4 months, by means of an objective computer-aided method to measure C-SP and its relationship to stimulation intensity. C-SP duration was significantly reduced in ALS patients compared to controls at low stimulation intensity corresponding to an MEP threshold increased by 15%. While in less severely affected patients C-SP duration approached control values at higher stimulation intensities (25 and 50% upper MEP threshold), in more severe ALS subjects it showed a further reduction, allowing them to be discriminated.
Siciliano
G
G
Department of Neurosciences, Neurological Clinics, University of Pisa, Pisa, Italy. gsilicia@neuro.med.unipi.it
Manca
M L
ML
Sagliocco
L
L
Pastorini
E
E
Pellegrinetti
A
A
Sartucci
F
F
Sabatini
A
A
Murri
L
L
D000368:Aged; D000690:Amyotrophic Lateral Sclerosis; D004558:Electric Stimulation; D055590:Electromagnetic Phenomena; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity