The value of testing for unmyelinated fibre, sensory neuropathy in diabetic impotence

Measurement of thermal thresholds provides a means of assessing neurological deficit and in particular of recognising a neuropathic process affecting unmyelinated and small myelinated fibres of the peripheral nerve. These groups of fibres cannot be tested by nerve conduction studies but are particularly susceptible to disease in diabetes. Thresholds for thermal sensation on the sole of the foot were measured in 33 men presenting with erectile dysfunction. All 15 men with erectile dysfunction, which had been considered on clinical grounds to be neuropathic, had abnormal thermal thresholds. Diabetics with non-neuropathic erectile dysfunction had normal results. Whereas tests of unmyelinated sensory fibre function were abnormal in all those with neuropathic erectile dysfunction, electrophysiological measurement of the bulbocavernosus reflex was normal in five of nine men with diabetic neuropathic impotence.