title: Motor potentials evoked by magnetic stimulation of the motor cortex in normal subjects and patients with motor disorders.
abstract: Motor evoked potentials (MEPs) elicited by magnetic coil stimulation of motor cortex were studied at rest and during maximum voluntary muscle contraction in 20 normal subjects and 42 patients with motor disorders. MEP parameters employed in this study included: onset latency, amplitude, MEP/M wave amplitude ratio and background EMG/MEP area ratio. Maximum voluntary contraction increased the amplitude of MEPs compared to the size of M waves elicited by peripheral nerve stimulation. A reduced MEP/M wave amplitude ratio had a higher correlation with pyramidal tract involvement than did a prolonged MEP onset latency. Analysis of MEP parameters may help in the differential diagnosis of cerebral infarction, ALS and cervical spondylotic radiculomyelopathy. The inhibitory period which follows MEPs during voluntary contraction was observed in all subjects; the mean duration in normal subjects was 126.6 +/- 29.5 msec. The mean duration of the inhibitory period in patients with cerebral infarction, ALS and cervical spondylotic radiculomyelopathy was 73.9 +/- 41.7 msec, 79.5 +/- 54.5 msec and 85.1 +/- 36.5 msec, respectively. These values were significantly shorter than in normal subjects.
authors.affiliation: Department of Neurology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu City, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Uozumi
authors.forename: S
authors.initials: S
authors.lastname: Tsuji
authors.forename: Y
authors.initials: Y
authors.lastname: Murai
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology; D001927:Brain Diseases / Q000503:physiopathology*; D005071:Evoked Potentials; D006801:Humans; D008280:Magnetics; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009048:Motor Skills; D009103:Multiple Sclerosis / Q000503:physiopathology; D009119:Muscle Contraction; D010300:Parkinson Disease / Q000503:physiopathology; D013118:Spinal Cord Diseases / Q000503:physiopathology