Impaired motor cortex inhibition in patients with amyotrophic lateral sclerosis. Evidence from paired transcranial magnetic stimulation

Neurology. 1997 Nov;49(5):1292-8. doi: 10.1212/wnl.49.5.1292.


We investigated 14 patients with amyotrophic lateral sclerosis (ALS) by paired conditioning-test transcranial magnetic stimulation to test the hypothesis that the motor cortex is hyperexcitable in ALS. Intracortical (corticocortical) inhibition was significantly less in the ALS group than in an age-matched healthy control group (85.3 +/- 27.0% versus 45.2 +/- 15.5%, respectively; p < 0.0001). In contrast, intracortical facilitation, motor threshold, and cortical silent period duration in the ALS patients were not different from the control group. We suggest that the selective abnormality of intracortical inhibition is best compatible with an impaired function of inhibitory interneuronal circuits in the motor cortex that in turn renders the corticomotoneuron hyperexcitable.

MeSH terms

  • Aged
  • Amyotrophic Lateral Sclerosis / physiopathology*
  • Electric Stimulation
  • Electromyography
  • Evoked Potentials, Motor*
  • Excitatory Postsynaptic Potentials / physiology
  • Female
  • Humans
  • Interneurons / physiology
  • Male
  • Middle Aged
  • Motor Cortex / cytology
  • Motor Cortex / physiopathology*
  • Motor Neurons / physiology
  • Neural Inhibition*
  • Transcranial Magnetic Stimulation