Cortical silent period in patients with amyotrophic lateral sclerosis

J Neurol Sci. 1999 Oct 31;169(1-2):93-7. doi: 10.1016/s0022-510x(99)00223-3.


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.

MeSH terms

  • Aged
  • Amyotrophic Lateral Sclerosis*
  • Electric Stimulation
  • Electromagnetic Phenomena
  • Evoked Potentials, Motor*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Sensitivity and Specificity