Percutaneous cervical stimulation: effects on intraspinal structures.
Changes in the amplitude of motor evoked potentials (MEPs) from percutaneous cervical stimulation (PCS) obtained at rest in the thenar muscles, and smaller than 0.8 mV, were studied under 3 different experimental conditions. A significant enhancement was observed mainly with a conditioning subthreshold transcranial stimulus and when MEPs were obtained in coincidence with weak voluntary contraction of the target muscle. Subthreshold stimulation of Ia fibers of the median nerve seemed to have a smaller facilitatory effect. It is generally accepted that PCS excites the spinal motoneuron (SMN) axons at the spinal nerve. However, our results show that other SMNs, usually not recruited, may be triggered by PCS when they receive excitatory postsynaptic potentials from the pyramidal tract (PT) or Ia fibers. This behavior suggests that low intensity PCS also exerts subthreshold excitation of the PT fibers and, perhaps, of the incoming spindle afferents, which adds its effects to the conditioning stimuli.
Segura
M J
MJ
Division of Neurology, Hospital J.M. Ramos Mejia, Buenos Aires, Argentina.
Gandolfo
C N
CN
Sica
R E
RE
D000293:Adolescent; D000328:Adult; D000368:Aged; D004558:Electric Stimulation; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009476:Neurons, Efferent / Q000502:physiology; D012867:Skin; D013116:Spinal Cord / Q000502:physiology*