Introduction

According to early studies,^{1, 2, 3} the overall incidence of traumatic and medical spinal cord injury (SCI) in Spain is estimated to range between 12 and 20 cases per million inhabitants. The highest percentage occurs between the ages of 20 and 40 y. In all, 75% are traumatic in origin, and nearly 80% of those affected are men.

After SCI, the complex mechanism regulating normal sexual activity is severely altered. In men, it causes a serious alteration of the physical phenomena that controls sexual activity, such as erection, ejaculation, and perception of orgasm, and changes the sexual behavior of the patient.⁴ These alterations are often accompanied by a personality disorder, manifesting as decreased self-image, low self-esteem, feelings of distrust, and fear of abandonment. At times, these feelings are more overwhelming than those resulting from paralysis itself. Thus, it is necessary for these dysfunctions to be treated from a multidisciplinary perspective, in which the paraplegia specialist works together with a team of psychologists/psychiatrists to help the patient develop a new model of sexuality, which is satisfactory for him and his partner. Therefore, management of sexual dysfunction in an SCI patient is considered an important part of the Comprehensive Rehabilitation Program.⁵

Pathophysiology

Under normal conditions, erections can be triggered by a sensory stimulus in the genitals through a reflex arc that carries the nerve impulse from the penis to the spinal cord (at the level of the sacral S2-S4 segments, the parasympathetic center) and then travels back to the penis, resulting in a reflex erection.⁶ When the lesion is located above the thoracic T10 spinal segment in complete SCI, the sympathetic and parasympathetic control centers are intact and the period of spinal shock in the acute phase of the lesion has passed. The patient can achieve reflex erections (without regulation by the brain) when they are provoked by manual stimuli (spinal reflex arc). These erections usually last for a limited time and are not useful for maintaining satisfactory sexual relations.⁷

Penile erection, however, can be initiated through another pathway (central erection) triggered by stimuli perceived or generated in the brain (psychogenic). These stimuli are sent through a spinal center (sympathetic center), which is located at the thoracolumbar T11-L1 level of the spinal cord.⁷

Most cases of ED result when the lesion destroys the T11-L2 segments. Nevertheless, depending on the extent of the lesion and the level of the segments affected, reflexogenic and/or psychogenic erections may still occur. When the lesion is located in the lumbosacral segments (L3-S5), the sympathetic center can receive central stimuli and the patient can achieve psychogenic erections. However, these erections are often less rigid and more difficult to maintain.^{7, 8}

In men with complete SCI, more than 80% can achieve an erection, whether reflexogenic, psychogenic, or mixed; however, most of these patients require some type of treatment for ED. In men with incomplete SCI, the response varies. A large number of patients with incomplete SCI also require treatment.

Diagnostic proposal

Diagnosis and neurological classification of SCI, a thorough examination of sensitivity, the bulbocavernous reflex, and an urodynamic assessment of neurogenic bladder help determine the severity of ED. These examinations usually establish adequate therapeutic management.

Most patients with SCI are young men in whom a diagnosis of neurogenic ED is clear. It is essential to take a focused history to rule out the presence of ED from either psychogenic or organic causes before the occurrence of the injury. Patients with incomplete lesions who need no treatment may not suffer from a neurogenic cause. Organic, psychogenic, or multifactorial causes for ED should first be ruled out. Consequently, the same diagnostic proposal that was established in the core document should be applied.

Changes in erectile response in those patients with established lesions are often either arterial or veno-occlusive in nature. Arterial insufficiency may be a consequence of hypertension, hyperlipidemia, diabetes mellitus, smoking, and so on.

The possibility that ED is iatrogenic or secondary to a surgical procedure, such as sphincterotomy, bladder surgery, neobladder, or prostatectomy, should be ruled out, because these causes are frequent in patients with SCI. Certain drugs, such as high doses of the oral antispasmodic baclofen, antipsychotics, antidepressants, or antihypertensives, which are used in the treatment of patients with established SCI, may also modify erectile response.

Therapeutic proposal

Sexual counseling

Management of ED in a paraplegic or tetraplegic man should include a psychological assessment of the impact the disability may have on general health. Therefore, collaboration with teams that specialize in psychology or psychiatry is desirable.

The patient should know how his SCI will affect his sexual response, not only the specific problem of ED but also overall perception of orgasm. Orgasm is often eradicated or altered (unsatisfying orgasms or unpleasant sensations) in patients with complete lesions of the spinal cord above L1–L2, in a high percentage of patients with incomplete lesions, and in patients with lesions at lower levels.

The patient should be counseled on how to find pleasure in erogenous zones unaffected by the SCI, such as the neck and back, so that he can achieve orgasm-like sensations. He should also learn the most appropriate positions based on his capacity of movement. In short, the patient will have to modify his sexual behavior and may need to look for sexual relations less focused on the genitals, in which fantasy, communication, and tenderness are equal in importance to his own sensory perceptions.

Symptomatic treatment

Following the recommendations given in the core document, treatment should account for certain considerations that are applicable to persons with SCI.

First-line treatment

Oral drugs

Sildenafil citrate: Sildenafil citrate has shown high efficacy and safety in the treatment of ED in patients with SCI. Clinical studies have shown efficacy rates of 75–94% in this population compared with 7–10% for placebo-treated patients.^{9, 10, 11, 12, 13, 14}

The Investigación de Disfunción Eréctil en Lesión Medular (IDELEM [Erectile Dysfunction Research in Spinal Cord Injury]) study examined the response of 170 men with SCI aged 18 y of age or older (after the spinal shock phase). The results revealed that sildenafil treatment was highly effective in this type of patient, achieving an efficacy of 88%, which was corroborated by 85% of their partners.¹⁰

In patients treated with sildenafil, 70% had an improved response with 50 mg of sildenafil; 30% improved with 100 mg of sildenafil.¹⁰ Among treatment responders, the improvement was confirmed by an increase from 13 to 25 points in the Erectile Function domain of the International Index of Erectile Function,¹⁵ as well as significant improvements in the Sexual Satisfaction and Overall Satisfaction domains.¹⁰

In patients with grades 3 and 4 baseline erections (reflex or voluntary erections of medium rigidity and short duration) and in those who retained the perception of orgasm at baseline, the probability of a positive response was 4.5 and five times higher, respectively. For sildenafil to be effective in SCI patients, some degree of reflex erection must remain or the spinal sympathetic and parasympathetic centers must be intact, or at least partially intact.¹⁰ A correlation could not be established between the level and type of SCI recorded and the effectiveness of the drug. However, the contribution of this study to the investigation of ED in patients with cervical lesions should be noted because it demonstrated a lack of severe side effects in these patients with higher level SCI.¹⁰

The safety profile of sildenafil in patients with SCI was another notable aspect of this study. No serious adverse events occurred during the study, and side effects were limited to the known symptoms of headache, flushing, nasal congestion, visual disturbances, and dyspepsia in 24% of patients. However, special caution should be exercised in patients with cervical lesions or lesions above T5 because hypotension and orthostasis can coincide.

Sublingual apomorphine hydrochloride

No studies have assessed the efficacy of apomorphine in SCI patients; however, based on its mechanism of action, it is reasonable to assume that it may not be effective in spinal cord lesions above segment T10. Similarly, apomorphine likely has little effect on T11–L2 lesions; although it may be useful in lesions below L3 and in incomplete spinal cord lesions. This needs to be confirmed in ongoing studies.

Vacuum devices and constriction rings

When oral drugs are ineffective, the next step in first-line treatment is to recommend constriction rings or bands. These methods are recommended only in cases in which the patient was previously able to achieve a potent reflex erection because the rings will allow the patient to maintain the erection for a longer period of time.

Vacuum devices can be used in cases in which a reflex erection is absent. Both methods use constriction rings and must be monitored for potential erosions or decubitus ulcers, which may occur because of insensitivity.^{16, 17}

Second-line treatments

Intracavernous injection of vasoactive drugs

The patient should be instructed on how to self-inject, and in cases of poor manual dexterity, the physician can teach the partner or caregiver.

In published studies, intracavernous injections have been shown to have high efficacy rates, ranging from 80 to 90% in patients with SCI and reflex erections and 70 to 80% in those with areflexive erections. Few complications have been observed and their management is relatively easy.^{18, 19, 20}

An intracavernous injection should be performed when the penis is in a flaccid state; otherwise, abrupt detumescence may easily occur with passage of the drug into the general circulation. The dose should be adjusted individually for each patient because the response is variable. A better response is more likely to occur in patients with SCI who initially have an intense reflex erection. In these cases, treatment should start with a lower initial dose of 5 g of prostaglandin E₁ or 3 mg of papaverine.

Third-line treatments

Only cases in which the previous treatments have proven ineffective should other treatment options, including surgical procedures (penile prosthesis and sacral root stimulation) performed by specialists in urology or andrology, be proposed.^{21, 22}

Any man with SCI, regardless of age, cause, or level and extent of injury, may be treated with these methods while bearing in mind the absolute or relative contraindications for each treatment method.

Referral criteria and causes

Paraplegia specialists, whose basic training in andrology allows them to apply first- and second-line treatments, have traditionally treated patients with ED of neurogenic origin. Only surgical treatments lie outside their area of expertise, and these cases would be referred to an urologist/andrologist specializing in ED. The paraplegia specialist should decide when treatment of ED is warranted and inform the appropriate specialist about the patient's general condition. The paraplegia specialist should also discuss spasticity, neurogenic bladder status, the possibility of decubitus ulcers, and the psychological state of the patient. As with other specialties, this specialist should follow the referral algorithm if he or she does not intend to diagnose or treat patients with ED.

References

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