Pearls & Oy-sters: Transient Horner syndrome associated with autonomic dysreflexia

DISCUSSION

Horner syndrome refers to the cluster of signs—ptosis, miosis, and anhidrosis—that occur as a result of interruption of the sympathetic supply to half of the face. Depending on the anatomical location of the underlying pathologic process, Horner syndrome usually is associated with unique clinical features classified into central, preganglionic, and postganglionic types (figure, B).¹

While Horner syndrome occurs as a result of interruption of sympathetic activity, autonomic dysreflexia is defined as acute episodic hypertension resulting from overactivity of spinal sympathetic circuits in individuals with SCI. The etiology of autonomic dysreflexia is not entirely understood. However, the loss of supraspinal inhibitory inputs following cervical or high thoracic injuries (typically at or above the sixth thoracic spinal segment [T6]) is among the primary causes for the development of autonomic dysreflexia. These injuries isolate sympathetic preganglionic neurons that supply the mesenteric arterial bed from inhibitory supraspinal control. In addition, evidence from human and animal studies indicates there are plastic changes in the spinal cord and periphery that result in this aberrant cardiovascular response following SCI. Namely, hyperresponsiveness of vascular α-adrenergic receptors or impaired reuptake of catecholamines following SCI may contribute to the development of autonomic dysreflexia.² Injury-induced hypertrophy and sprouting of primary sensory neurons could also contribute.³ Furthermore, SCI-induced alterations of intraspinal autonomic circuits, including abnormal connections on interneurons and morphologic alterations of sympathetic preganglionic neurons, may also contribute to the etiology of autonomic dysreflexia.^4,5

Transient Horner syndrome has been previously described in another study with respect to hypertension (in an able-bodied individual) where Horner syndrome was resolved 1 month after the initial event.⁶ The authors attributed Horner syndrome in this able-bodied individual to a TIA.⁶ In addition, autonomic dysreflexia has been previously described in relation to syringomyelia.⁷ However, transient Horner syndrome has not been previously described in relation to an episode of autonomic dysreflexia.

It may be that in our patient, as a result of the autonomic dysreflexia–induced hypertension, there was an increase in intramedullary pressure with a concomitant increase of intrasyrinx pressure that would selectively compromise sympathetic output.⁸ We could only speculate that the pressure was distributed asymmetrically on the preserved tissue of the spinal cord, with more prominent compression of the right side during the episode of autonomic dysreflexia. With resolution of the episode and normalization of blood pressure, the intraspinal pressure would decline, and pressure on the fragile nervous tissue would resolve, resulting in the disappearance of Horner syndrome.

While this was an unusual presentation of autonomic dysreflexia, the condition is relatively common among individuals with high thoracic and cervical SCI. Autonomic dysreflexia occurs to some extent in up to 90% of these individuals and can be a daily event for many people with SCI.⁵ Autonomic dysreflexia also occurs, though less frequently, in nontraumatic SCIs, such as multiple sclerosis.⁹

Although autonomic dysreflexia can in some cases be silent, there are several characteristic signs and symptoms. In addition to the aforementioned signs and symptoms of headache, flushing, diaphoresis, and elevated blood pressure, other signs and symptoms include reflexive bradycardia, anxiety, blurred vision, nasal congestion, and piloerection.⁵

Episodes of autonomic dysreflexia are triggered by painful or nonpainful stimuli originating from below the level of injury, and are most commonly related to bladder or bowel irritation.⁵ Such stimuli may include bladder distention, bladder or kidney stones, blocked or kinked catheters, urinary tract infections, fecal impaction, constipation, and bladder or rectal examination. Other stimuli may include tight clothing or equipment, hemorrhoids, sunburns, pressure sores, ingrown toenails, broken bones or fractures, sexual activity, menstruation, and labor.

It is important for the clinical management of patients with SCI to recognize that individuals with higher injuries typically have low resting systolic blood pressure (90–100 mm Hg), as in this case, so the elevated blood pressure from autonomic dysreflexia may go unrecognized upon initial presentation. In most instances, autonomic dysreflexia is resolved as soon as the irritating stimuli are removed. However, in some cases, malignant episodes can occur that require immediate medical attention. Autonomic dysreflexia has been linked to adverse events such as cerebral hemorrhage, myocardial ischemia, and even death.¹⁰

Guidelines for the management of autonomic dysreflexia recommend to first sit the patient upright in order to induce a decrease in blood pressure due to the orthostatic response.⁵ It is recommended next to loosen or remove restrictive clothing, and survey the precipitating causes. If systolic blood pressure remains above 150 mm Hg, it is recommended to use an antihypertensive agent such as nifedipine or captopril. Also, heart rate and blood pressure should be monitored regularly at 5-minute intervals. In this case, the cause of autonomic dysreflexia was bladder related, and antihypertensive agents were not necessary.

We report on an unusual presentation of a common condition among individuals with high thoracic and cervical SCIs. Early recognition and prompt management of this potentially life-threatening condition are imperative to reduce the risk of cardiac and cerebrovascular events in this population.