Autonomic dysreflexia

This condition is distinct and usually episodic, with the people potentially experiencing remarkably high blood pressure, intense headaches, profuse sweating, facial erythema, goosebumps, nasal stuffiness, a "feeling of doom" or apprehension, and blurred vision.[5] An elevation of 20 mm Hg over baseline systolic blood pressure, with a potential source below the neurological level of injury, meets the current definition of dysreflexia.[10]

The first episode of autonomic dysreflexia may occur weeks to years after spinal cord injury takes place, but most people at risk (80%) develop their first episode within the first year after injury. Early AD tends to be associated with less severe increases in blood pressure.

One common causative factor may be an undetected urinary tract infection. The difficulty in assessing this may be complicated with the usage of indwelling or suprapubic catheters. Other causes include medication side effects and various disease processes. The use of stimulants such as cocaine and amphetamines which can result in urinary retention, and the use of CNS depressants and other psychoactive drugs can also lead to urinary retention and constipation thus leading to autonomic dysreflexia when in use over an extended period of time.

Supraspinal vasomotor neurons send projections to the intermediolateral cell column, which is composed of sympathetic preganglionic neurons (SPN) through the T1-L2 segments.[7] The supraspinal neurons act on the SPN and its tonic firing, modulating its action on the peripheral sympathetic chain ganglia and the adrenal medulla.[7] The sympathetic ganglia act directly on the blood vessels they innervate throughout the body, controlling vessel diameter and resistance, while the adrenal medulla indirectly controls the same action through the release of epinephrine and norepinephrine.[7] The descending autonomic pathways, which are responsible for the supraspinal communication with the SPN, are interrupted resulting in decreased sympathetic outflow below the level of the injury.[7] In this circumstance, the SPN is controlled only by spinal influences.[7] The first couple of weeks after a spinal injury, the decreased sympathetic outflow causes reduced blood pressure and sympathetic reflex.[7] Eventually, synaptic reorganization and plasticity of SPN develops into an overly sensitive state, which results in abnormal reflex activation of SPN due to afferent stimuli, such as bowel or bladder distension.[7] Reflex activation results in systemic vasoconstriction below the spinal cord disruption. The peripheral arterial vasoconstriction and hypertension activates the baroreceptors, resulting in a parasympathetic surge originating in the central nervous system, which inhibits the sympathetic outflow; however, the parasympathetic signal is unable to transmit below the level of the spinal cord lesion.[8] This results in vasodilation, flushing, pupillary constriction and nasal stuffiness above the spinal lesion, while there's piloerection, pale and cool skin below the lesion due to the prevailing sympathetic outflow.[8] The reason this issue is much more prominent for lesions at or above the T6 level is because the Splanchnic nerves emerge from the T5 level and below. Loss of brain's control over T6 and below causes splanchnic arteries to reflexively vasoconstrict and since the Splanchnic arteries are the body's largest reservoir for circulating blood, their vasocontriction dramatically affects the blood pressure of the body.

The symptoms are usually not subtle, although asymptomatic events have been documented. Autonomic dysreflexia differs from autonomic instability, the various modest cardiac and neurological changes that accompany a spinal cord injury, including bradycardia, orthostatic hypotension, and ambient temperature intolerance. In autonomic dysreflexia, patients will experience hypertension, sweating, spasms (sometimes severe spasms) and erythema (more likely in upper extremities) and may experience headaches and blurred vision. Mortality is rare with AD, but morbidity such as stroke, retinal hemorrhage and pulmonary edema if left untreated can be quite severe. Older patients with very incomplete spinal cord injuries and systolic hypertension without symptoms are usually experiencing essential hypertension, not autonomic dysreflexia. Aggressive treatment of these elderly patients with rapidly acting antihypertensive medications can have disastrous results.

Proper treatment of autonomic dysreflexia involves administration of anti-hypertensives along with immediate determination and removal of the triggering stimuli. Often, sitting the patient up and dangling legs over the bedside can reduce blood pressures below dangerous levels and provide partial symptom relief. Tight clothing and stockings should be removed. Straight catheterization of the bladder or relief of a blocked urinary catheter tube may resolve the problem. The rectum should be cleared of stool impaction, using anaesthetic lubricating jelly. If the noxious precipitating trigger cannot be identified, drug treatment is needed to decrease elevating intracranial pressure until further studies can identify the cause.

Drug treatment includes the rapidly acting vasodilators, including sublingual or topical nitrates or oral hydralazine or clonidine. Ganglionic blockers are also used to control sympathetic nervous system outflow. Topical nitroglycerin ointment is a convenient and safe treatment—an inch or two can be applied to the chest wall or forehead, and wiped off when blood pressures begin to normalize.[13][9] Autonomic dysreflexia is abolished temporarily by spinal or general anaesthesia. These treatments are used during obstetric delivery of women with autonomic dysreflexia.

The cause of autonomic dysreflexia itself can be life-threatening, and must also be completely investigated and treated appropriately to prevent unnecessary morbidity and mortality.

The Consortium for Spinal Cord Medicine has developed evidence-based clinical practice guidelines for the management of autonomic dysreflexia in adults, children, and pregnant women. There is also a consumer version of this guideline.