Electrophysiological assessment of corticorespiratory pathway function in amyotrophic lateral sclerosis.
Respiratory muscle paralysis is inevitable in the clinical course of amyotrophic lateral sclerosis (ALS). Our objective was to electrophysiologically assess the function of the phrenic nerve and diaphragm motor cortex in ALS. Phrenic nerve M waves, diaphragm motor evoked potentials (MEPs) induced by transcranial magnetic stimulation, and their clinical correlations were analyzed in 29 ALS patients. The M wave amplitude was significantly lower in patients than in healthy control subjects (p<0.001). The MEP amplitudes both in the expiratory and inspiratory phases were significantly decreased in patients (p<0.01). In particular, 15 patients showed no MEPs in the expiratory phase, six of whom also showed no MEPs in the inspiratory phase. Five of them had no respiratory complaints. There was a weak, non-significant correlation between the inspiratory MEP amplitude and forced vital capacity (p=0.052). We conclude that the loss of MEP might reflect the subclinical involvement of the voluntary respiratory drive from the diaphragm motor cortex, potentially leading to further respiratory deterioration.
Shimizu
Toshio
T
Department of Neurology, Tokyo Metropolitan Neurological Hospital, Japan. tshimizu@tmnh.fuchu.tokyo.jp <tshimizu@tmnh.fuchu.tokyo.jp>
Komori
Tetsuo
T
Kugio
Yumiko
Y
Fujimaki
Yumi
Y
Oyanagi
Kiyomitsu
K
Hayashi
Hideaki
H
D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000150:complications / Q000503:physiopathology*; D003964:Diaphragm / Q000294:innervation / Q000503:physiopathology*; D004525:Efferent Pathways / Q000503:physiopathology; D004576:Electromyography; D045853:Exhalation / Q000502:physiology; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009431:Neural Conduction; D010791:Phrenic Nerve / Q000502:physiology; D012129:Respiratory Function Tests; D012131:Respiratory Insufficiency / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D014836:Volition / Q000502:physiology