PROXIMALLY EVOKED SOLEUS H-REFLEXES IN THE EVALUATION OF AXONAL NEUROPATHY

It is sometimes difficult to differentiate physiologically distal axon opathy from proximal root or nerve disease. Standard soleus H reflexes evoked by distal tibial nerve stimulation at the popliteal fossa are often absent in both syndromes. In this study we distinguish the two b y the presence or absence of soleus H reflexes evoked by proximal scia tic nerve stimulation at the gluteal fold. In 12 normal subjects maxim um H reflex amplitudes evoked by distal tibial and proximal sciatic st imulation were essentially equal. In 12 patients with suspected distal polyneuropathy, proximal but not distal stimulation evoked H reflexes . By contrast, in 10 patients with lumbosacral root or proximal nerve disease, both proximal and distal stimulation failed to elicit H refle xes. In 2 patients with lower motor neuropathy, low but comparable amp litude H reflexes were evoked at both sites. We conclude that the pres ence of a proximally evoked soleus H reflex may provide specific evide nce of distal axonopathy when standard soleus H reflexes are absent.