A proposed new, minimally invasive, and painless method for studying impairment of the autonomic system of the penile region in type 2 diabetes patients.
Thirteen subjects were selected from 150 patients with type 2 diabetes and erectile dysfunction who were studied in accordance with the National Institutes of Health consensus. The 13 subjects (group A), aged 55 ± 8 years, had acceptable metabolic control (HbA1c, <8%); no arterial or venous diseases or initial Peyronie's disease, as evaluated by penile Doppler ultrasonography and intracavernous prostaglandin E1 injection; and penile tumescence at the base (PTB) <30 mm. Group B consisted of 13 control subjects with the same characteristics, including mean age (53.1 ± 9 years), metabolic control (HbA1c, 7.3 ± 0.7%), and duration of disease (8.3 ± 0.7 years), but PTB was =30 mm. Student's t test was used to evaluate differences in the results of autonomic cardiovascular tests, somatic tests (vibration perception threshold [VPT]), and diabetic neuropathy score (DNS) in both groups. The coefficient of variation of PTB was evaluated using the Rigiscan device (Dacomed, Minneapolis, MN), and Bayes' test was used to test sensitivity, specificity, and positive predictive values of the cardiovascular tests.
Patients with PTB <30 mm had significant (P < 0.05) impairment of parasympathetic tests (lying to standing, P < 0.02; standing to lying, P < 0.04; squat test, P < 0.03) compared with subjects with higher PTB values. No difference in DNS and VPT at the base and tip of the penis was found between the two groups. The variability of the test is 10% in normal subjects and 15% in both groups of patients. PTB sensitivity was 54%, specificity 89%, and positive predictive value 79%.
In patients with diabetes and without vascular diseases, the PTB evaluated by Rigiscan is related to impairment of the autonomic nervous system. A PTB value <30 mm may be considered a useful, noninvasive marker in studying parasympathetic damage of the penile region.
