SOLEUS H-REFLEX TO S1 NERVE ROOT STIMULATION

H-reflexes in normals were elicited by percutaneous electrical and mag netic stimulation of proximal nerve roots at the cauda equina. H-M int erval to S1 nerve root stimulation at the level of the S1 foramen was 6.8 +/- 0.33 ms, with side to side difference of 0.16 +/- 0.13 ms. Com pression/ischemia of the sciatic nerve in the mid-thigh abolished the I-I-reflex to stimulation of the tibial nerve at the popliteal fossa w hen the H-reflex to S1 nerve root stimulation was preserved. The lengt h of the S1 nerve root in human cadavers was measured to be 17.5 +/- 0 3 cm, providing an estimated dorsal root conduction velocity of 67.3 m /s and a ventral root conduction velocity of 54 m/s. We conclude that the H-M interval to S1 root stimulation can provide reliable measures of conduction within the spinal canal including proximal afferents, an terior horn cells and ventral roots. (C) 1998 Elsevier Science Ireland Ltd.