Study ties sexual problems in MG to nerve issues

Sexual dysfunction is common among adults with myasthenia gravis (MG) and appears to be associated with impairment of the autonomic nervous system, which regulates involuntary bodily processes, a study shows.

“These findings support an association between autonomic dysfunction and [sexual dysfunction] in patients with MG beyond psychosocial factors alone,” the researchers wrote.

The study, “Autonomic dysfunction and its association with sexual dysfunction in myasthenia gravis,” was published in Clinical Autonomic Research by a team of researchers in Turkey.

MG is caused when antibodies mistakenly attack receptor proteins at the neuromuscular junction, the place where nerves signal muscles. This leads to fluctuating weakness in certain muscle groups that worsens with exertion and improves with rest.

The autonomic nervous system regulates functions such as heart rate, blood pressure, sweating, digestion, certain eye functions, and breathing. Autonomic impairment has traditionally not been considered a defining feature of MG.

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Sexual complaints frequent

Sexual function, including arousal, blood flow, lubrication, and orgasm, is also regulated by the autonomic nervous system. While not considered a core symptom of MG, sexual complaints from patients are frequently reported in clinical practice. Yet the relationship between autonomic impairment and sexual dysfunction has not been directly assessed in MG.

“We hypothesized that impaired autonomic function would be associated with a higher prevalence of [sexual dysfunction] in patients with MG,” the researchers wrote.

The team examined data from 44 MG patients (52.3% women), ages 18-60, who had been in a sexual relationship with a regular partner for six months or longer. A group of 50 age- and sex-matched healthy individuals served as controls.

Anxiety and depressive symptoms were significantly more common in the MG group than in the control group.

The researchers found that MG patients had signs of autonomic dysfunction across all four extremities, as indicated by tests on sweat gland nerve function. Here, MG patients showed significantly longer latencies (slower nerve responses) and lower amplitudes (weaker nerve responses) than healthy controls.

In eye tests, patients showed significantly reduced tear production, smaller pupils in dim light, and more severe nerve damage to the cornea (the clear, outer layer on the eye’s surface) than controls.

The median Composite Autonomic Symptom Score-31, a questionnaire on autonomic symptoms, was significantly higher (worse) in MG patients than in controls (16.5 vs. 11.5 points). In particular, scores were significantly higher in the subdomains of vasomotor (blood pressure), secretomotor (tear and sweat secretion), gastrointestinal, and bladder control.

At the same time, sexual dysfunction was significantly more frequent in adults with MG than in controls (72.7% vs. 48%).

Men with MG showed significantly more problems with premature ejaculation than controls, as assessed with the Premature Ejaculation Profile score. But erectile dysfunction, defined by the International Index of Erectile Function, did not differ between groups.

Among women, sexual dysfunction, as indicated by the Female Sexual Function Index (FSFI), was significantly more frequent, by twofold, in those with MG (82.6% vs. 39.3%).

Within the MG group, older age correlated with erectile dysfunction for men and worse FSFI scores for women. Erectile dysfunction also correlated with shorter corneal nerve fiber length, lower corneal nerve fiber density, and lower (worse) heart rate variability during hyperventilation (rapid or deep breathing).

Even so, disease severity, as assessed by the MG Foundation of America classification, was not related to autonomic or sexual function measures. Anxiety and depression scores also showed no links with sexual function tests, and FSFI scores did not correlate with autonomic measures.

Statistical analyses adjusted for age, depression, and anxiety showed that lower corneal nerve fiber length and density were independently associated with sexual dysfunction.

In men, lower heart rate variability during hyperventilation and more gastrointestinal symptoms were significantly associated with premature ejaculation. No such associations were found in healthy men.

“These findings highlight [sexual dysfunction] as a potentially underrecognized manifestation of autonomic involvement in MG and underscore the importance of considering autonomic dysfunction when evaluating nonmotor symptoms in this population,” the researchers concluded.