This review attempts to outline the present understanding of diabetic autonomic neuropathy. The clinical features have been increasingly recognised but knowledge of the localization and morphology of the lesions and their pathogenesis remains fragmentary. A metabolic causation as postulated in somatic nerves accords best with clinical observations. Most bodily systems, particularly the cardiovascular, gastrointestinal and urogenital, are involved with added disturbances of thermoregulatory function and pupillary reflexes. Possible effects on neuroendocrine and peptidergic secretion and respiratory control await definition. Current interest centres around the development of a new generation of tests of autonomic nerve function that are simple, non-invasive, reproducible and allow precision in diagnosis and accurate quantitation. Most are based on cardiovascular reflexes and abnormality in them is assumed to reflect autonomic damage elsewhere. Probably no single test suffices and a battery of tests reflecting both parasympathetic and sympathetic function is preferable. Little is known of the natural history. The prevalence may be greater than previously suspected and although symptoms are mild in the majority, a few develop florid features. The relation of control and duration of diabetes to the onset and progression of autonomic neuropathy is not clearly established. Once tests of autonomic function become abnormal they usually remain abnormal. Symptomatic autonomic neuropathy carries a greatly increased mortality rate possibly due to indirect mechanisms such as renal failure and direct mechanisms such as cardio-respiratory arrest. Improved treatment of some of the more disabling symptoms has been possible in recent years.

https://link.springer.com/content/pdf/10.1007/BF01235856.pdf

Diabetic autonomic neuropathy

New method for continuous measurement of nocturnal penile tumescence and rigidity.

Nocturnal penile tumescence (NPT) was assessed in 30 impotent patients for the purpose of differential diagnosis. In 11 psychogenic cases, with several exceptions, NPT was found to be normal, with a marked discrepancy between the NPT findings and the patients' estimates of their daytime erectile capacity. In 19 organic patients, maximal NPT corresponded closely to and mirrored the patient's subjective estimate of his impaired waking performance. Statistically, the figures for frequency, degree, duration, and amount of NPT were found to be significantly and markedly greater in the psychogenic group. Statistical significance was maintained when the 11 psychogenic patients were closely age-matched with 11 of the 19 organic cases. The method is not 100% accurate; some 15% of impotent patients without organic findings have reduced NPT, several of whom were shown to be psychogenic, but others in this group may have undetected organic pathology. The NPT method is very promising, but beset by a number of methodological problems.

Evaluation of nocturnal penile tumescence in the differential diagnosis of sexual impotence. A quantitative study.

The authors conducted a study of nocturnal penile tumescence (NPT) in 35 diabetic men, aged 33 to 70, who complained of impotence and in 35 age-matched control subjects. EEGs and other measurements showed that the diabetic men as a group exhibited significant reductions in the total amount of NPT and in the amount and frequency of full erection, thus suggesting that impotence in this cohort was organogenic. Although NPT monitoring represents an advance over the less precise traditional procedures for the differential diagnosis of impotence, the authors stress the need for more research in this area.

Nocturnal penile tumescence and diagnosis in diabetic impotence.

Apomorphine (Apo), a short acting dopamine (DA) receptor agonist induces penile erections in normal subjects. The erectile response to one or more doses of Apo HCl (0.25, 0.5, 0.75, 1.0 mg sc) or placebo was investigated in eight impotent subjects and penile tumescence monitored using a mercury strain gauge and strip chart recording. Four patients showed a full erection with Apo and one a partial response. Distressing side effects (nausea, sweating) were associated with non-response or partial response. Three responders to Apo were treated with low doses of the long acting DA receptor agonist, bromocriptine (2.5-3.75 mg/d po); all three showed complete recovery of erectile function within two weeks. A subgroup of impotent patients may have impaired central DA function. Testing with Apo may provide a diagnostic and predictive test to identify such patients who may respond to treatment with low doses of bromocriptine or other DA receptor agonist.

P J Salis

Papers

Nocturnal erections, differential diagnosis of impotence, and diabetes.