An electrophysiological study of the corticospinal projections in amyotrophic lateral sclerosis.
OBJECTIVE
To elucidate the pattern of corticospinal tract involvement in patients with amyotrophic lateral sclerosis (ALS), we analyzed motor evoked potential (MEP) waveforms and their relationship to the behaviour of single motor units using the peristimulus time histogram (PSTH) technique.


METHODS
Abnormality of the corticospinal pathways was studied in 35 ALS patients using MEPs. PSTHs were also constructed to assess the effect of magnetic cortical stimulation on the discharge pattern of a voluntarily activated motor unit.


RESULTS
MEPs showed a complex waveform in 10 out of 18 (56%) ALS patients with upper motor neuron signs (UMN). PSTHs revealed double primary peaks (PPs), PP1 and PP2, in 6 out of 16 motor units (38%) in ALS with UMN, as compared to only 2 out of 16 (13%) motor units in multiple sclerosis or cerebrovascular disease with UMN. None of the patients with lower motor neuron diseases or ALS without UMN had these abnormalities. The late component of complex MEPs showed a good correlation to PP2 (P < 0.0001), both probably being mediated by relatively preserved slower conducting corticospinal volleys.


CONCLUSIONS
These findings suggest preferential involvement of the fast conducting direct corticospinal tracts, sparing the slower or polysynaptic projections in ALS.
Kohara
N
N
Department of Neurology, Kyoto University Hospital, Japan. kohara@kuhp.kyoto-u.ac.jp
Kaji
R
R
Kojima
Y
Y
Kimura
J
J
D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology