Impotence is the inability to obtain and sustain an erection satisfactory for sexual intercourse.
Causes can be grouped into the following categories: neurologic, vascular, endocrine, systemic, pharmacologic, and psychological. Treatment is directed accordingly.
Reflex erections are mediated by the afferent fibers of the pudendal nerve and efferent fibers of the parasympathetic outflow (S2-4). Psychogenic erections are initiated via cerebral centers. Specific neurologic diseases that may cause impotence may be congenital (spina bifida), acquired (cerebrovascular accident, Alzheimer disease, multiple sclerosis), iatrogenic (electroshock therapy), neoplastic (pituitary or hypothalamic tumors), traumatic (cord compression), infectious (tabes dorsalis), and nutritional (vitamin deficiency).
Vascular causes of impotence may be cardiac (anginal syndromes, congestive heart failure), aortoiliac disease (Leriche syndrome, atherosclerosis, other embolic phenomena), microangiopathy (diabetes, radiation injury), and abnormal venous drainage.
The accepted endocrine causes of impotence are hypogonadism, hyperprolactinemia, pituitary tumors, hypothyroidism, Addison disease, Cushing syndrome, acromegaly, and testicular feminizing syndrome.
Impotence is a common and often unsuspected complication of many therapeutic and illicit drugs. Major groups that may cause sexual dysfunction are the following: tranquilizers, antidepressants, antianxiety agents, anticholinergic drugs, antihypertensives, and many drugs with abuse potential. One should recognize that virtually all antihypertensives (including diuretics) can be associated with impotence or ejaculatory dysfunction. Drugs with abuse potential include alcohol (both as a direct effect and secondary to cirrhosis) and cocaine.
Up to 50% of cases of impotence are related to psychogenic factors. Establishing an organic cause of impotence is important in choosing appropriate therapy. Factors that indicate a psychogenic cause are the following: selective erectile dysfunction (episodic, normal nocturnal erections, normal erections with masturbation), sudden onset, associated anxiety or external stress, affect disturbances (anger, anxiety, guilt, fear), and patient convinced of an organic cause.
The history and physical examination suggest the cause in most cases. Confirmatory tests are necessary to ensure an appropriate choice of therapy.
In investigating a possible neurologic cause of impotence, the neurologic examination should include review of systems with respect to bladder and bowel function. More invasive studies include a cystometrogram, electromyography of the external urethral sphincter, and bulbosphincteric reflex latency.
Vascular impotence is suggested by signs of peripheral vascular disease as well as a history of atherosclerotic heart disease. Noninvasive diagnostic testing is performed with penile duplex Doppler studies to assess arterial inflow. Venous leak can be evaluated with cavernosography and cavernosometry. Arteriography is rarely required but may be indicated in patients with a history of pelvic trauma and those considering microvascular arterial revascularization.
Endocrine evaluation mandates measurement of serum testosterone and prolactin; many investigators include assessment of FSH and LH. Routine automated chemical screening may suggest other hormonal abnormalities that require additional testing. These studies should also detect systemic disease capable of causing impotence: cirrhosis, renal failure, scleroderma, and diabetes.
Psychogenic impotence may be established by nocturnal penile tumescence monitoring or outpatient snap-gauge cuffs. Additional testing includes one of the following: Minnesota Multiphasic Personality Inventory, DeRogatis Sexual Function Inventory, and Walker Sex Form.
First-line treatment includes oral phosphodiesterase inhibitors (sildenafil, vardenafil, tadalafil). These medications are contraindicated in men with heart disease who are taking nitroglycerin. These medications work in patients who have normal blood flow and neurologic innervation. In patients without arterial-vascular causes of impotence, intracorporal injections of papaverine, phentolamine, or prostaglandin E1 (or all three) offer a nonoperative means of restoring sexual function. Intractable psychogenic impotence may also respond to this treatment. Intraurethral pellets of alprostadil (prostaglandin E1) can also be used; however, they often cause pain and are not favored by most patients. Finally, a vacuum erection device can be used to sustain erection.
Endocrine disturbances responsible for impotence include low testosterone and hyperprolactinemia. Testosterone deficiency is treated by replacement therapy using a once-daily topical testosterone gel or depot testosterone intramuscular injection every 2-3 weeks. Hyperprolactinemia is treated by bromocriptine therapy; the patient should be evaluated to assess the presence of a pituitary tumor.
Pharmacologic causes of impotence require altering medical treatment to ameliorate or eliminate secondary impotence. The ability to change medications depends on the severity of the underlying disease.
Psychogenic impotence is treated by a trained sex therapist, and response may be anticipated in most cases. The importance of eliminating organic causes of impotence before embarking on psychological therapy is obvious: The best psychological methods applied to organic impotence do not resolve the dysfunction but serve to frustrate both the therapist and patient.
Penile prosthesis insertion is currently the most common operative method for treatment of impotence. Two categories of prosthesis are in use: semirigid and inflatable. The semirigid prostheses are composed of a rigid shaft and a flexible hinge at the penile-pubic junction or a malleable soft metal case within the prosthesis; the erection is constant and is satisfactory to effect vaginal penetration, but the penile circumference is not equal to that of a natural erection.
Inflatable prostheses offer erections more similar in size to those experienced by the patient prior to the onset of impotence when compared to those achieved by semirigid prostheses. Two types of inflatable prostheses are available: The standard inflatable prosthesis consists of two corporal inflatable rods, a reservoir situated in the retropubic space, and a pump placed in the scrotum; the new inflatable rods combine the simplicity of two corporal rods with the sophistication of a self-contained pump and reservoir system (FlexiFlate and Hydroflex), permitting the convenience of inflation and deflation without tubing and multiple components.
Satisfactory results are achieved in 85% of patients. Complications common to both types of prostheses are infection and erosion of skin or urethra. The inflatable prostheses are also at risk for mechanical failure of the pump, tubing or reservoir leak, and aneurysm or rupture of the corporal cylinders.
Arterial revascularization of the penile arteries has met with limited success. Aortoiliac reconstruction improves erectile function in only 30% of cases. Microsurgical revascularization of the penile arteries (dorsal artery of the penis or deep corporal arteries) is successful in about 60% of patients. Although these methods avoid the risks of prosthetic infection and offer the advantage of reestablishing the natural physiologic mechanisms or erection, the mediocre success rate (when compared with the results of prosthetic insertion) would suggest that microsurgical penile revascularization be reserved for carefully selected cases.