10. Sexual Dysfunction in Suprapontine Lesions
KeywordsSexualityNeurological diseaseErectile dysfunctionPremature ejaculationLubricationOrgasmic dysfunctionHypersexuality
Sexuality is a component of a fulfilled life. Neurologic disease may affect the sexual function by the neural lesion itself, or by its treatment, but also because of other disease-related deficits and issues including psychosocial and cultural changes resulting from the chronic disease.
Loss of sexual desire (or hypersexuality), erectile and ejaculatory dysfunction in men, decreased lubrication in women, and disturbances of orgasm are more common in neurological patients than in the general population, but are often not communicated by them to their doctor. Sexual symptoms may be relevant for the diagnosis, significantly affect the quality of life, and may be responsive to treatment.
10.1 Sexual Function and the Nervous System
The sexual response is traditionally conceptualized as a sequence of phases, desire, arousal, and orgasm, but it can also be seen as a cycle of overlapping phases, more appropriate for the description of the female sexual response . In any case, sexual behavior involves a series of neurally controlled phenomena including normal vasculature, occurring in a hormonally defined milieu.
The primary sensory areas in the brain and the parietal and inferior temporal lobes process sexual stimuli; the forebrain regulates the initiation and the execution of sexual behavior; the medial preoptic area integrates sensory and hormonal signals; and the amygdala plays a role in the reward aspects of sexual function. Neurons from the paraventricular nucleus project to the thoracic and lumbosacral spinal cord nuclei, which, by way of the sympathetic, parasympathetic, and somatic nerves, affect the genital response . Fertility and procreation are importantly linked to sexuality, but will not be discussed here.
10.2 Change in Sexual Function with Aging
When examining the sexuality of neurological patients, their premorbid status has to be ascertained.
In the elderly the frequency of intercourse as a rule decreases and sexual dysfunction is more prevalent than in younger patients; nevertheless, about a quarter of those aged 75–85 years report sexual activity. Males need more time and stimuli to achieve erection and orgasm, and their refractory period after detumescence is prolonged. In the female, there is decreased libido and thinning of the vaginal wall with decreased elasticity and lubrication .
10.3 Evaluation of Patients with Sexual Dysfunction and Neurologic Disorders
The history reveals the relevant sexual symptoms, and other factors influencing sexual functioning, including drugs. Formal questionnaires can be used to obtain standardized information on male and female sexual function.
On clinical examination changes in pigmentation and body hair, and presence of galactorrhea, should be noted. Functional investigations of genital arousal are not performed, unless vasogenic erectile dysfunction is suspected (in men). Neurophysiological testing may clarify the topical diagnosis only in infrapontine lesions. Patients with suspected endocrine dysfunction should be referred to the endocrinologist.
10.4 Sexual Dysfunction in Patients with Suprapontine Lesions
In patients with suprapontine lesions the prevalence of sexual dysfunction is reportedly higher than in the general population, but few epidemiological studies have been done.
10.4.1 Head and Brain Injuries
Some cognitive impairment, personality change, and sensorimotor disability often remain after traumatic brain injury and may be accompanied by sexual dysfunction. Among patients with closed-head injury admitted for 24 h or more, significant sexual dysfunction was found in 50% over a 15-year time span.
Frontal and temporal lesions seem to result more often in sexual disturbances than parieto-occipital lesions. Symptoms may occur, at least in part, as a consequence of posttraumatic pituitary dysfunction .
Hypersexuality, disinhibited and inappropriate sexual behavior, sexually aggressive behavior, and changes in sexual preference sometimes follow basal frontal and limbic brain injury and may lead to sex offences. Bilateral anterior temporal lesions result in the Klüver–Bucy syndrome with hypersexuality and pansexuality .
10.4.2 Hypothalamopituitary Disorders
Hypothalamopituitary dysfunction is usually caused by a pituitary adenoma. Three-fourths of patients have decreased or absent libido at the time of diagnosis. Erectile dysfunction is common, but because of reduced sexual interest is less distressing.
Most female patients have amenorrhea. Women with hypoprolactinemia complain of loss of sexual desire .
10.4.3 Cerebrovascular Disease
About 75% of patients who were sexually active before the stroke report a subsequent decrease in coital frequency. Late outcome studies are scant; poor sexual functioning may persist even with otherwise good improvement. Many men (up to 65%) have erectile dysfunction after a stroke; orgasmic and ejaculatory dysfunction are common. Decreased vaginal lubrication and inability to achieve orgasm occur in female patients. Function may, however, return within a year.
Patients and their partners may avoid sexual intercourse out of concern of recurrence. The workload during sexual activity is similar to that of climbing stairs or walking briskly. Although the exact risk of stroke during sexual activity is not known, it seems to be low. Patients and their partners may thus be reassured that, in resuming sexual activity, the gains in most instances outweigh any slight risks.
Hypersexuality after stroke has been described, but seems to be rare .
10.4.4 Parkinsonism and Basal Ganglia Disorders
The dopaminergic system is intimately involved in neural circuits controlling desire and arousal. Patients with Parkinson’s disease of both genders show a decrease in libido, in frequency of intercourse, and in the ability to reach orgasm. In men, erection and ejaculation may be affected. In women, vaginal tightness and involuntary urination during intercourse are reported.
Muscle rigidity and bradykinesia may impair sexual activity; tremor may be enhanced during sexual arousal. All these may be worse in the late evenings if dose scheduling is aimed at favoring daytime activities.
Dopaminergic treatment may result in an apparent increase, or normalization, of libido even without corresponding improvement in motor symptoms. Spontaneous erections have been reported in patients receiving levodopa and dopaminergic agonists. About 3% of treated patients demonstrate true hypersexuality.
Deep brain stimulation of the subthalamic nucleus may have a positive influence on sexual well-being of men, but hypersexuality has also been reported .
In multiple system atrophy, erectile dysfunction usually begins several years before the onset of other neurologic symptoms. By the time of diagnosis, 30% of patients were also unable to ejaculate. Patients of both genders have a decrease in desire and the ability to reach orgasm, and the frequency of intercourse falls. Hypersexuality may occur with dopaminergic treatment.
Approximately 10% of patients with Huntington disease have increased sexual activity, sometimes associated with mania or hypomania. Promiscuity may be an early or initial symptom of the disease. But patients also report difficulties in becoming sexually aroused. Paraphilias such as sexual aggression, exhibitionism, and pedophilia occur.
Disinhibited sexual behavior is common in patients with Gilles de la Tourette syndrome .
10.4.5 Multiple Sclerosis
Sexual dysfunction affects eventually the majority of patients and decreases their quality of life.
Erectile dysfunction is rare initially, but becomes more common with the evolution of multiple sclerosis. Spontaneous improvement sometimes occurs. Problems with ejaculation are frequent and are often coupled to the erectile dysfunction.
Decreased vaginal lubrication and sensory disturbances involving the genital region (hypoesthesia, hyperesthesia, and different types of pain) are common and may be apparent already in the early stages of multiple sclerosis. Sacral-segment dysesthesias may be so severe that patients are unable to bear direct genital contact.
Decreased libido but also hypersexuality may occur.
Other symptoms related to multiple sclerosis, such as fatigue, depression, cognitive dysfunction, spasticity in the lower limbs, urinary and bowel disturbances, and use of aids to manage incontinence, can inhibit sexuality, as can paroxysmal motor and sensory disturbances, triggered by sexual intercourse .
Epilepsy is associated with sexual problems, more often in men than women. It is helpful to determine whether disturbances relate to seizures or occur during the interictal period.
Hyperventilation accompanying sexual activity can provoke generalized epileptic seizures. Sexual fantasies as well as genital stimuli (masturbation) or orgasm may trigger reflex epilepsy.
Sensations in the genital organs may be manifestations of a partial epileptic seizure arising from a genital sensory cortical area. Motor symptoms such as erection and ejaculation or the sensory experience of an orgasm may also occur, the latter particularly from right mesio-temporal foci. Pelvic sexual movements, as a part of epileptic automatisms, or compulsive masturbation in front of others may occur during or after a seizure. Such events may be experienced by patients as sexual or nonsexual.
Complex sexual experiences occur most often in patients with temporal lobe lesions. Sexual automatisms may also occur with frontal lobe lesions.
Interictally, loss of sexual desire, reduced sexual activity, or inhibited sexual arousal are reported. Sexual interest is more reduced in patients with left temporal lobe lesions. Paranoid delusions of a sexual nature occur in some.
Antiepileptic drugs, especially older agents (phenytoin, phenobarbital, primidone, carbamazepine, and valproate), lead to hormonal changes (particularly increased estradiol and decreased free testosterone levels in men), and decreased sexual desire and performance in both sexes. The effect of the newer anticonvulsant drugs on sexual function is claimed to be less. Restoration of sexual function has been reported after successful surgery for epilepsy .
10.5 Treatment of Sexual Dysfunction
Sexual dysfunction associated with neurologic disease often increases patients’ distress. Discussion with patients and partners about their sexual life should be part of any rehabilitation strategy. In all instances, drug regimens should be reviewed for possible effects on sexual function. Sexual education, counseling, and specific suggestions about therapeutic methods are important, and should be provided by the treating physician. In a limited number of patients, referral to a sexual therapist may be indicated. Methods for sexual rehabilitation in the context of neurologic disorders have been described .
10.5.1 Treatment of Neurogenic Erectile Dysfunction
The development of drug treatments by the oral and intracavernous routes has revolutionized the outlook for men with erectile failure. The selective inhibitors of type 5 cyclic guanosine monophosphate phosphodiesterase augment the nitric oxide-mediated relaxation pathway in penile tissues by increasing available cyclic guanosine monophosphate in the corpus cavernosum. These medications therefore do not cause erection but enhance the response to sexual arousal. Sildenafil taken at bedtime also significantly increases nocturnal erections.
Sildenafil is an effective treatment for erectile dysfunction in neurological patients; good studies have been done in patients with multiple sclerosis  and with Parkinson’s disease (cf 8), but experience supports the use of this (and similar) medicine in all neurological patients.
Sildenafil (25, 50, or 100 mg) can be taken orally 1 h before intended sexual activity. (Significant effects have been reported between 30 min and 4–6 h after taking the medication.) It should be noted that a meal delays absorption of the drug, and so does slowed gastric emptying such as seen in Parkinson’s disease and autonomic neuropathy. Treatment should be begun with 25–50 mg, and the same dose taken several times before it is increased. Dose-finding studies have demonstrated a dose-response curve. Sildenafil can be used repeatedly, and if used once or twice per week there should be no fear of tachyphylaxis.
Phosphodiesterase-5 inhibitors are contraindicated in combination with vasodilator drugs of the nitro type and nitric oxide donors, but a cardiologist can change such drug regimens in suitable patients with erectile difficulties requiring treatment. Phosphodiesterase-5 inhibitors should not be used in patients with retinitis pigmentosa. They are contraindicated in men with hypotension (blood pressure below 90/50 mmHg). Care should be taken to identify men with multiple system atrophy who may have erectile dysfunction, atypical parkinsonism, and asymptomatic postural hypotension. In our experience, an intelligent patient can use sildenafil after clear explanation, with careful planning of activity during the several hours after drug intake and performing sexual activity in the recumbent position.
No evidence was found of sildenafil effects on the myocardium or the conduction system. However, evaluation of functional capacity is necessary in patients with coronary artery disease, who need to know the risks of physical (and sexual) activity. Patients who can exercise up to 4.5 metabolic equivalents without angina or hypotension can probably use sildenafil safely. Recommendations for the use of sildenafil in patients with cardiovascular disease have been published. In controlled and open-label studies, no increased risk of cerebrovascular events has been reported.
The most common adverse events of sildenafil are headache, flushing, and dyspepsia. Temporary visual symptoms (mainly color-vision disturbances) may occur with higher doses (100 mg), and nonvasculitic anterior optic neuropathy has been described in rare instances. Adverse effects are mostly transitory and of minor intensity .
Treatment with apomorphine sublingually is an effective option for men with erectile dysfunction, but due to its weaker effect and obnoxious side effect (nausea) it is not available commercially in most countries.
Yohimbine is an ancient aphrodisiac which has little to offer in the presence of modern drugs .
10.5.2 Intracavernous Injection Therapy with Vasoactive Drugs
Prostaglandin E1 (alprostadil) is the preferred drug for self-injection therapy in erectile dysfunction, and low doses are effective in neurogenic impotence. The effect is rapid and independent of sexual excitement and may last for 2–4 h. Local bleeding, pain, and fibrosis may develop in the corpora cavernosa, leading to loss of effectiveness. This treatment is contraindicated in patients taking anticoagulants or with hematologic malignancies.
Long-lasting erections—priapism—as an adverse drug reaction usually have a good prognosis with conservative treatment .
10.5.3 Other Treatment Options
With a dedicated vacuum device, rigidity adequate for penetration occurs in most patients with neurogenic erectile dysfunction. The most common complications are bruises, petechiae, and skin edema. The constriction band should not stay in place for longer than 30 min.
The use of a constriction band on its own may help patients who can obtain an erection, albeit not a durable one; the same restrictions concerning the duration of application should be observed.
In neurogenic erectile dysfunction, part of the problem may be penile sensory loss. Additional vibratory stimulation may help in producing a rigid erection sufficient for vaginal penetration.
As a last resort, surgical treatment is also possible (penile prostheses) .
10.5.4 Premature Ejaculation
Counseling on the use of particular techniques during coitus may lead to improvement. Pharmacotherapeutic options include antidepressants (selective serotonin reuptake inhibitors such as paroxetine), and phosphodiesterase-5 inhibitors, used off label .
10.5.5 Treatment in Women with Sexual Dysfunction
Vibratory stimulation and dildos may be helpful and are routinely advised in patients with genital sensory disturbances and in those with weakness or motor disorders.
In women with dysesthetic or painful sensations in the genitalia that are not alleviated by improving lubrication, antiepileptic drugs such as gabapentin, pregabalin, and carbamazepine may help. Efficacy and safety of flibanserin (with minor effects in treatment of hypoactive sexual desire syndrome) in neurogenic dysfunction are not reported.
10.5.6 Treatment of Hypersexuality
For abnormally increased libido, pharmacologic treatment should be checked. Androgen antagonists (cyproterone acetate, medroxyprogesterone acetate) may be effective. In resistant cases, neuroleptics are usually helpful .
10.6 Concluding Comments
Tools to define the individual role of different biologic factors (such as endocrine, neurologic, vascular, endothelial, and other factors) and of psychosocial influences in the individual with sexual dysfunction are still crude. The options to help patients have nevertheless improved significantly and help can be offered to the patient and the partner.