M. De Carvalho et al., Neurophysiological features of fasciculation potentials evoked by transcranial magnetic stimulation in amyotrophic lateral sclerosis, J NEUROL, 247(3), 2000, pp. 189-194
We report 13 patients with amyotrophic lateral sclerosis in whom fasciculat
ion potentials (FPs) driven by transcranial magnetic stimulation (TMS) were
recorded. ii total of 18 different FPs were analyzed. TMS-driven fascicula
tions had a simple morphology and were stable. Complex potentials were neve
r cortically driven. Recruitment by a slight voluntary contraction was veri
fied in 7 of 13 tested FPs. FPs were driven by threshold stimuli in 7 of 10
patients and by stimuli 5% below threshold in 3 of 6. Mapping demonstrated
that FPs were driven in an area close to the center of gravity of the musc
le cortical area. In one case FPs were evoked from most of the cortical rep
resentation area of a very weak muscle. Three other patients with profuse f
asciculations associated with other clinical conditions were also studied.
No TMS evoked fasciculation was observed in this group. The results of this
systematic study suggest that cortically evoked FPs arise centrally, at sp
inal cord or even more proximally, and can represent a marker of increased
corticomotor excitability, which is predominant at an earlier phase but can
persist as the disease progresses.