Priapism after spinal cord injury – a case report and review of the literature

Abstract

Involuntary unwanted erections are extremely rare after spinal cord injury (SCI). A sudden loss of sympathetic tone to the pelvic vasculature following SCI causes an increase in the parasympathetic tone and uncontrolled arterial blood flow into the penile sinusoidal spaces. When occurring immediately after an acute SCI, it is generally self-limiting and settles within a few hours. In contrast, recurrent, unwanted erections in patients with chronic SCI are more unpredictable in frequency and duration and may require treatment. We present a case of recurrent involuntary unwanted erections in a patient with chronic SCI after a stab wound to his neck and review the pathophysiology and available management options.

Introduction

Involuntary unwanted erections are extremely rare after spinal cord injury (SCI), and the exact incidence is unknown. ¹ The oldest known case dates back to the 17th century BC: The Edwin Smith Surgical Papyrus, thought to be the oldest discovered medical papyrus, describes a patient with a cervical spine fracture complicated by quadriplegia priapism, seminal emission, and urinary incontinence. ² The Ancient Egyptian physician concerned with the case noted that the prognosis was guarded and dolefully declared that his patient had “an ailment not to be treated.” ³ We present a case of recurrent involuntary unwanted erections in a patient with chronic SCI after a stab wound to his neck and review the pathophysiology and available management options.

Case presentation

A 34-year-old male patient was brought to our emergency department by his neighbor after sustaining a single stab wound to the neck and finding himself unable to walk. Physical examination found him fully conscious, hemodynamically stable and without any neck restraint. A single right-sided stab wound was noted in the lower anterior triangle of the neck (Figure 1), and air entry was reduced over the right hemithorax. He could not move his lower limbs or feel sensation below the waist, and his cervical spine was immobilized forthwith. A chest x-ray revealed a right-sided pneumothorax, and an intercostal drain was inserted. A multidetector helical computed tomography (CT) with angiography and contrast swallow ruled out vascular, laryngotracheal, and pharyngo-oesophageal injuries. T2-weighted magnetic resonance imaging (MRI) of the spine revealed a central intramedullary high signal lesion of the spinal cord at the T2–T3 level as the cause of his acute paraplegia (Figure 2).

Figure 1.

Clinical photograph depicting a single stab wound in zone 1 of the right anterior triangle.

Figure 2.

T2-weighted MRI a central intramedullary high signal lesion of the spinal cord at the level of T2–T3.

Our urology department was consulted 5 h after admission with a complaint of persistent erection of 4-h duration. He denied the use of antipsychotics, recreational drugs, or any oral medication or self-injection for erectile dysfunction. He gave no history of hematological diseases such as sickle cell anemia or leukemia. Further, examination revealed no evidence of trauma to the pelvis, perineal, or genital area. A full blood count, liver, renal and thyroid function tests and serum electrolytes were normal. No sickle cells were detected on the peripheral smear. A tox screen was negative. Penile corporal blood gas analysis demonstrated a high-flow, non-ischemic priapism with pH 7.42, pCO₂ 35.2 mmHg, and pO₂ 93.5 mmHg. Repeat penile corporal blood gas analysis reaffirmed the priapism to be non-ischemic in nature, and it was decided to manage the patient conservatively. The priapism resolved spontaneously 7 h after onset. The patient reported two further episodes of unwanted erections, each lasting 30 min over the next 24 h. He was transferred to a rehabilitation unit. He showed no demonstrable improvement in motor and sensory function at follow-up 5 months later and no recurrence in priapism episodes.

Discussion

High-flow priapism is a persistent erection caused by unregulated cavernous arterial inflow. Although more commonly caused by blunt perineal or penile trauma, it is a rare complication of SCI. The proportion of male patients with priapism post-SCI is unclear because of the scarcity of reported cases in the literature. ⁴ A sudden loss of sympathetic tone to the pelvic vasculature following SCI causes an increase in the parasympathetic tone and uncontrolled arterial blood flow into the penile sinusoidal spaces. ⁵ Lesions and injuries of the cervical spinal cord are most frequently associated with priapism. However, since the sympathetic outflow to the penis arises from the most caudal aspect of the spinal cord, the conus, a lesion at any level of the spinal cord, can be associated with priapism.^6,7

Although SCI patients with priapism have been found to present with high-flow, non-ischemic priapism, this diagnosis should not be assumed ab initio. Causes of low-flow priapism should first be excluded routinely since delayed intervention for low-flow ischemic priapism may result in permanent corporal fibrosis, cellular damage, and permanent impotence. Therefore, the history should inquire for risk factors such as pharmacotherapy for erectile dysfunction (both oral and intracavernous), medications such as antipsychotics, illicit drug use, and a history of hematological diseases such as sickle cell anemia or leukemia. Penile blood gas analysis is critical to confirm the diagnosis of high-flow, non-ischemic priapism. A penile ultrasound may be helpful to further reaffirm the diagnosis of non-ischemic priapism by demonstrating normal bilateral penile artery Doppler velocities. Seeing that our patient had sequential penile blood gas analyses that were suggestive of non-ischemic priapism, we did not perform a penile Doppler ultrasound.

Priapism usually occurs immediately after an acute SCI, and, in this setting, the priapism is generally self-limiting and settles within a few hours (up to 30 h) after the injury – as was the case in our patient.^6,7 In contrast, the clinical course of recurrent or refractory priapism in patients with chronic SCI is far more variable. Koyuncu et al. and Vaidyanathan et al. both described patients with tetraplegia after a diving accident and another after a mountain bike accident.^1,8 In both cases, the patients first experienced involuntary, unwanted erections many weeks after their acute SCI. The recurrent erections reduced significantly in both duration and frequency on oral baclofen, a γ-aminobutyric acid derivative, which is known to inhibit both erection and ejaculation by relaxing the ischiocavernosus and bulbospongiosus muscles.^9–11 Oral baclofen may prove ineffective in many patients. Because the spinal cord represents only about 2% of the brain’s mass and therefore receives a proportionately lower fraction of cardiac output, ¹² cerebral side effects often occur before the therapeutic anti-spastic effects of oral baclofen are observed. Intrathecal baclofen (ITB) therapy injected directly into the subarachnoid space has proven beneficial in patients with chronic priapism after SCI. A pump is implanted surgically in the subcutaneous tissue of the anterior abdominal wall, and baclofen is delivered via a silicone rubber catheter into the lumbar subarachnoid space. The ITB pump delivers approximately 100–900 μg/day of baclofen and is titrated for the desired clinical response. ¹² When baclofen is introduced directly into the intrathecal space, sufficient CSF concentrations can be achieved with plasma concentrations 100 times less than those occurring with oral administration. D’Aleo et al. reported the case of a 41-year-old male with C3 tetraplegia after a motor vehicle accident who had priapismic episodes commencing a month after his injury. ¹⁰ Oral baclofen (75 mg/day) had minimal benefit. After a successful test dose of ITB proved effective in controlling the priapism episodes, further ITB therapy was administered via an implanted pump system. Denys et al. studied nine men with SCI or multiple sclerosis and chronic priapismic episodes who received ITB via an implantable pump. ¹³ After an average of 44.4 months follow-up, eight of the nine patients reported decreased erection rigidity and duration after ITB therapy. Prolonged ITB infusion causes a down-regulation of GABA_B receptors in the CNS and spinal cord. The baclofen itself causes increased inhibitory tone in the CNS and spinal cord. ¹⁴ Abrupt ITB withdrawal results in the cessation of this inhibitory tone in the CNS and results in the predominance of excitatory effects with the reappearance of a baseline level of spasticity associated with mild symptoms such as pruritis, anxiety, and disorientation. ¹² More severe consequences of ITB withdrawal syndrome are hyperthermia, exaggerated rebound spasticity and muscle rigidity, seizures, rhabdomyolysis, multisystem organ failure, cardiac arrest, and coma.^15–17 Prompt initiation of high-dose benzodiazepines, reinstitution of baclofen, and proper supportive intensive care management are the essential pillars for managing ITB withdrawal syndrome. ¹²

Other suggested options for treating stuttering priapism include hormonal manipulation with gonadotropin-releasing hormone (GnRH) agonists or antagonists, anti-androgens, diethylstilbestrol, and ketoconazole, but their efficacy is unclear. ¹ Pseudoephedrine, digoxin, and terbutaline have been used to reverse erections by increasing corpus cavernosal smooth muscle tone. Low-dose phosphodiesterase type 5 (PDE-5) inhibitors, gabapentin, hydralazine, and hydroxyurea are other alternatives. ¹⁸ These drugs may be used in carefully selected patients where oral and ITB have failed. Digoxin or terbutaline may have detrimental cardiac side effects. Diethylstilbestrol increases the risk of deep-vein thrombosis in immobilized patients with severe SCI, and hormonal agents are contraindicated in children and in men who wish to remain fertile. ¹⁸ The high incidence of androgen deficiency and hypogonadism in SCI patients also precludes anti-androgenic measures in these patients.^19,20

Conclusion

Priapism after SCI may be associated with injury to any part of the spinal cord and is extremely rare. When occurring immediately after an acute SCI, it is generally self-limiting and settles within a few hours. In contrast, recurrent, unwanted erections in patients with chronic SCI are more unpredictable in frequency and duration and may require treatment, with ITB being highly effective. Therefore, patients should first respond to a screening dose of ITB before considering long-term infusion via an implantable pump.