Late response and sural conduction studies. Usefulness in patients with chronic renal failure.

Late response (H reflex and F response) and sural conduction studies were used in addition to conventional motor and sensory conduction to detect peripheral neuropathy in 30 randomly selected patients with chronic renal failure (18 receiving hemodialysis), five of whom had no clinical evidence of peripheral neuropathy; 30 age-matched control subjects were also studied. Conventional motor (median, ulnar, peroneal, and tibial) and sensory (median and ulnar) nerve conduction studies showed abnormalities of motor conduction in 25 (83%) and of sensory conduction in 26 (87%) patients. Abnormalities of sural nerve conduction and of late responses were present in all 30 patients. Five patients (17%) who had normal routine motor conduction showed abnormalities of late responses in the same nerve distribution. All electrophysiologic abnormalities were significantly more evident in lower limbs. Studies of late responses and sural conduction, in addition to improving the diagnostic yield, provide a method whereby effects of dialysis and medical management can be followed quantitatively in patients whose neuropathy would otherwise be undetectable.