[Transient radicular nerve conduction block in patients with intermittent neurogenic claudication].

Patients with neurogenic claudication do not usually exhibit symptoms at rest. The diagnosis is uncertain when there are no signs of lumbar radiculopathy. However, the functional deficiary could show up during a brief time at presentation of the symptoms if appropriate electrophysiological techniques are used to measure nerve conduction at the radicular segment. In 8 patients with neurogenic claudication, we examined the curve of recruitment of the soleus H reflex and in four of them the chronodispersion of the F wave of the posterior tibial nerve, before and after walking was also examined. Both studies showed normal results before walking in all patients. The H wave showed a transient diminution of excitability in 6 patients after walking, which lasted for a mean period of 7 min. Only one of these patients also showed an increase in the chronodispersion of the F wave. Our data suggest that conduction is transiently blocked in large myelinated fibers at a radicular level in patients with neurogenic claudication after walking. This could partially explain the symptoms of neurogenic claudication.