Erectile dysfunction (ED) in diabetes is multifactorial. So far, the impact of neuropathy has not been well determined. This study was performed to assess the frequency of abnormal neurophysiological tests in patients with ED due to diabetes compared to patients with ED due to nondiabetic neuropathies in order to estimate the contribution of neuropathy in diabetic ED. Forty-nine men with ED were studied. We classified ED as 'diabetic" 'neuropathic' or 'ED of other origin'. 26.6% of the men fulfilled the criteria of diabetic ED, 42.9% had neuropathic ED. In every patient history taking, a questionnaire focusing on autonomic symptoms other than ED, clinical examination, nerve conduction studies (NCS), sphincter ani electromyography (EMG), heart rate variability testing (HRV) and quantitative sensory testing (QST) was performed. Vascular function was assessed by the intracavernosal prostaglandin El (PGE1) injection test. The frequency of abnormal results in diabetic and neuropathic patients was compared. Vascular function was abnormal in only one patient with diabetic ED and three patients with neuropathic ED. Both groups had similar frequencies of autonomic symptoms other than ED (64% in diabetic vs. 64% in neuropathic patients), abnormal EMG (33% vs. 40%) and abnormal QST (vibratory perception 83% vs. 84%, cold perception 9% vs. 19%, warm perception 42% vs. 43%). Abnormal clinical findings (50% vs. 33%), NCS (75% vs. 50%) and HRV (39% vs. 25%) were slightly, but not significantly more frequent in men with diabetic ED than neuropathic ED. The tests indicating neuropathy showed abnormalities in men with diabetic ED as frequently as in men with neuropathic ED. Some tests even suggested neuropathy more often in diabetic than in neuropathic ED. The findings support the hypothesis that neuropathy contributes significantly to the pathophysiology of ED in diabetes mellitus. [Neurol Res 2001; 23: 651-654]
Keywords: Pathophysiology of diabetic erectile dysfunction; neuropathy; vasculopathy; nerve conduction studies; quantitative sensory testing
Diabetic men frequently present with erectile dysfunction (ED)1. ED may even be the first symptom of diabetes mellitus2. ED is defined as the persistent inability to obtain or maintain an erection to permit satisfactory sexual performance3. ED may be due to various causes such as neuropathy, cavernosal arterial insufficiency, corporal veno-occlusive dysfunction, endocrine abnormalities, or psychogenic etiology4-7.
The impact of neuropathy on diabetic ED has not been well established as yet, and it is unclear whether angiopathy of the genital vasculature or dysfunction of the nerves supplying the genitalia is the predominant pathophysiological factor of diabetic ED6-8. Assuming primary vascular changes to be the major pathophysiological factor in diabetic ED, one would expect a higher frequency of neuropathic findings in patients with ED, caused by a neuropathy without accompanying vasculopathy, than in diabetic ED. If neuropathy, on the other hand, was the major pathophysiological factor in diabetic ED, frequencies of abnormal findings suggestive of neuropathy should be similar in patients with diabetic ED and patients with purely neuropathic ED.
To clarify this issue and to estimate the impact of neuropathy on the pathogenesis of diabetic ED, we studied diabetic men with ED and men with ED caused by other neuropathies not affecting the vasculature, and we compared the frequency of clinical symptoms and neurophysiological abnormalities indicating neuropathy in both groups.
PATIENTS AND METHODS
Forty-nine patients (age 23-70 years, mean 52.3 years) with ED participated in the study. All men were referred to our department without prior selection.
The tests indicating neuropathy showed abnormal results in men with ED due to diabetes as frequently as in men with ED due to other neuropathies. Some of our tests, such as clinical signs of polyneuropathy, nerve conduction studies and heart rate variability studies, even suggested that neuropathy is slightly more frequent in diabetic than in neuropathic ED. The findings support the hypothesis that neuropathy is a major contributing factor in the pathophysiology of ED in diabetes mellitus. To refine the evaluation of the pathophysiology of ED and improve therapeutical decisions, an extended neurological work-up, including neurophysiological assessment of myelinated and unmyelinated nerve fibers, should be part of the diagnostic procedures used in diabetic patients with erectile dysfunction.
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Martin J. Hecht, B. Neundorfer, F. Kiesewetter* and Max J. Hilz
Department of Neurology, *Department of Dermatology, University of Erlangen-Nuremberg, Erlangen, Germany
Correspondence and reprint requests to: Professor Dr Max J. Hilz, Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
[email@example.com] Accepted for publication March 2001.
Copyright Forefront Publishing Group Sep 2001
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