To correlate abnormalities of nerve fibres in the lower limbs with erectile dysfunction in male diabetic patients, using a range of quantitative sensory and autonomic function tests.
Patients and methods
The study included 68 male diabetic patients with symptomatic erectile dysfunction and 11 matched diabetics without erectile dysfunction; none had clinical evidence of peripheral vascular disease or psychological disorder. Patients were evaluated with a symptom questionnaire based on the Michigan Neuropathy Screening Instrument questionnaire and examined clinically. Sural and peroneal nerve-conduction studies, and quantitative sensory and autonomic tests (vibration, thermal, light-touch thresholds, sensory and autonomic cutaneous axon-reflexes) were used to detect nerve abnormalities in the lower limbs, which were correlated with erectile dysfunction.
Symptoms of neuropathy were more common in the group with male erectile dysfunction (MED), but statistically significant only for neuropathic pain (53% MED, 18% nonMED, P<0.05, chi-square test) and gastroparesis (44% MED, 0% nonMED, P<0.05). Tests of unmyelinated afferents (warming perception and capsaicin-induced sensory axon-reflex vasodilatation) were most often abnormal, sometimes with no other abnormalities on tests or neurological examination. However, abnormality of warm perception was not significantly different between groups (81% MED, 70% nonMED), suggesting that it is a poorer discriminant than abnormal sensory axon-reflex vasodilatation (89% MED, 22% nonMED, P<0.001). The only other significant test difference was decreased sural nerve action potential (70% MED, 22% non-MED, P<0.01).
There appeared to be preferential involvement of unmyelinated sensory fibres that mediate axon-reflex vasodilatation in the limbs of diabetic patients with erectile dysfunction. This test appears to be a helpful indicator of neurological involvement in erectile dysfunction, and may be used to monitor the effect of new treatments.