Autonomic dysreflexia

Autonomic dysreflexia represents a medical emergency that strictly requires support from specialized equipment and medication in order to maintain normal functions of the body. Read and find out all about the causes, symptoms, diagnosis and treatment of this disorder.

Autonomic dysreflexia Definition

This is an extremely serious condition marked by an over-active autonomic nervous system (ANS) – a part of the nervous system that controls involuntary activities like heartbeat, breathing and digestive processes. It is most often abbreviated as AD. The disorder is also referred to as Autonomic hyperreflexia.

Autonomic dysreflexia Symptoms

Patients affected by AD usually experience an array of life-threatening clinical features that could place them at a fatal risk. The condition is clearly evident when individuals with defects in the autonomic nervous system display intermittent bouts of the following symptoms:

  • Elevated blood pressure (over 200 mm Hg)
  • Pounding headache
  • Profuse sweating
  • Restlessness
  • Nausea
  • Goose pimples
  • Nasal blockage
  • Red blotches on skin
  • Retinal damage
  • Facial redness
  • Cold and clammy skin
  • Excessively slow heart rate
  • Low pulse rate
  • Cognitive impairment
  • Overwhelming sense of doom

Autonomic dysreflexia Causes

The condition is significantly present in individuals with a spinal cord injury. Medical researchers believe that presence of lesions above the spinal nerve 6 of the thoracic segment (T6) is responsible for causing an uninhibited and exaggerated reflex of the ANS to any form of stimulus. In a few patients, the spinal lesions can develop at or lower than the spinal nerve 10 of the thoracic segment (T10). The ANS forms an essential segment of the peripheral nervous system, which comprises of 12 pairs of cranial nerves, spinal nerves and peripheral nerves.

ANS normally regulates homeostasis of the body through its two branches, the parasympathetic autonomic nervous system (PANS) and the sympathetic autonomic nervous system (SANS). Various flight-or-fight responses are promoted by the SANS, responsible for causing dilation of pupils, acceleration of heart rate, and increased blood pressure. The PANS, on the other hand, is associated with a number of relaxation responses, including slow heart rate, contraction of pupils, decreased blood pressure and increased peristalsis. In simple words, these two branches perform complementary roles through a negative feedback system to maintain proper functioning of the entire ANS.

In individuals with a severely damaged spinal cord, the lower motor neurons can recognize the painful stimuli below the level of injury and transmit signals to the brain. However, the pain signals undergo interruption at the site of damage that prevents them from being transmitted to the cerebral cortex. In this way, the two branches of the ANS get disconnected with the feedback loop and begin to function independently. As the SANS exits via the thoracic and lumbar spinal nerves, the clinical manifestations of the condition are typically an outcome of a sympathetic response due to excessive stimulation. The injured spinal cord inhibits the PANS, which normally exits through the midbrain, pons, medulla and the sacral level of the spinal cord, from counteracting responses like:

  • Increased blood pressure
  • Visual modifications
  • Anxiety
  • Throbbing headache

Post-injury, a myriad of stimuli can initiate AD that normally originates below the level of the spinal cord lesion. Some of these painful, discomforting, and physically irritating triggers include:

Distended or irritated bladder

In patients with a damaged spinal cord, loss of urinary bladder function prevents the nerve impulses to travel past the injury, resulting in a sympathetic reflex to the ANS in response to pain. The other stimulants are:

  • Urinary tract infection
  • Prolonged retention of urine
  • Bladder spasms
  • Bladder stones
  • Incompatible catheters

Overstretched bowel

AD can also occur when the bowel gets overfilled with stool or gas. Irritation in the rectum can readily cause hyperreflexia of the ANS. These causative factors include:

  • Constipation
  • Hemorrhoids
  • Anal fissure
  • Intestinal infections
  • Digital stimulation conducted during a bowel program

Dermatological disorders

Minor pressure on the region below the level of injury can trigger the condition. Burns, sores, cuts, scrapes, ulcers, allergy and ingrown toenails are the additional causes of AD.

Problems in the reproductive system

Over-stimulation during sexual intercourse can arouse the organs in a painful manner, giving rise to the condition. Most women experience sharp pain in the belly and pelvic areas during menstrual period. However, these mild menstrual cramps can cause marked increase in the sympathetic response to such a minor stimulus. Labor pains and contractions prior to delivery can also lead to AD.

Gastrointestinal conditions

Gastric ulcer, colitis and peritonitis can cause simultaneous episodes of sympathetic and parasympathetic activity.

Skeletal disorders

Heterotopic ossification, a disorder manifested by formation of bone at abnormal locations can easily injure the spinal cord, initiating an autonomic reflex in response to the pain. Vertebral fractures of the thoracic and lumbar spine can afflict the spinal cord, causing AD.

Intake of drugs

Urinary retention and constipation can occur as side effects of amphetamines as well as cocaine. Consumption of CNS depressants and a variety of psychoactive drugs could lead to exaggeration of the ANS.

Autonomic dysreflexia Diagnosis

Clinicians normally conduct a proper evaluation of the specific symptoms of AD in order to rule out the possibility of another condition called autonomic instability, which broadly describes any malfunction of the ANS. The absence of other severe neurological and cardiac deficits should be considered in the differential diagnosis of AD. The patients may have to undergo some of the following tests and exams for further clarification:

Blood and/or Urine test

In case of a suspected bladder or urinary tract infection, doctors usually perform an analysis on a sample of a patient’s blood or urine, or both. Increased WBC count and high concentration of bacteria in urine confirms the cause of the condition.

Cystometry

The clinical procedure assesses the bladder function by specifically measuring the contractile force of the organ when voiding. It may either involve insertion of one or two catheters into an emptied bladder through the urethra.

X-ray

The test can only determine a bone fracture.

Imaging studies

A series of CT or MRI images can provide a better insight into the condition. The radiological investigations are highly crucial in determining the location of the injury in the spinal cord.

Tilt-table testing

This simple medical exam involves placing a patient with a foot-support on a table, which is later tilted upward. The table is initially placed in a horizontal direction and slowly tilted by degrees to a vertical position. The main intention of the examination is to monitor the blood pressure, pulse and other symptoms of the affected patients. Any changes in these characteristics indicate AD.

Toxicology screening test

The numerous drugs known for triggering an autonomic reflex are metabolized by the liver or kidneys. On long-term exposure, these compounds can build up in both blood and urine. Testing for these drugs can be done with several simple hematology and urine exams.

Autonomic dysreflexia Treatment

Antihypertensives can be used for treatment of high blood pressure to prevent cardiac complications. The abnormal levels of blood pressure can be lowered by making the affected patients sit up and allowing their legs to hang freely. The manual therapy can however, partially alleviate the symptoms. Wearing tight clothes and shoes can exert sufficient amount of pressure. Therefore, tight clothing should be avoided altogether. Patients who undergo catheterization must check the urinary catheter tube from time to time for any blockage.

Accumulation of a mass of stool in the rectum due to chronic constipation should be cleaned with the help of an anesthetic lubricating jelly. The painful stimuli in most cases remain unidentified due to which physicians prescribe some medications for temporary relief. The constriction of blood vessels can be prevented with the immediate use of vasodilators like oral clonidine and nitrates. Ganglionic blockers can completely hinder the PANS and SANS and are used only in emergency situations, including AD. A nitrate medication called nitropaste can be applied topically in patients suffering from hypertension, owing to its vasodilatory property. To prevent recurrent episodes of the symptoms, prolonged treatment with alpha blockers or calcium channel blockers is essentially required. General or spinal anesthesia during obstetric delivery in women with AD is performed to prevent the occurrence of symptoms.

Autonomic dysreflexia Complications

Chronic form of the condition is obvious in patients who have sustained the spinal injury over a long duration of time. The existence of the chronic symptoms can eventually give rise to some of the most-feared complications like:

  • Retinal hemorrhage
  • Cerebral hemorrhage
  • Seizures
  • Pulmonary edema
  • Kidney damage
  • Myocardial infarction

Autonomic dysreflexia Prognosis

Unlike autonomic instability, AD does not lead to a fatal outcome. Healthcare providers generally follow a set of clinical practice guidelines that enable appropriate management of the condition.

Autonomic dysreflexia is a life-threatening condition that requires immediate care. Medical professionals must educate the patients about the potentially-lethal complications of the ailment. Various strategies and preventive measures must be followed by individuals to avoid the dangerous consequences of AD.

References:

http://en.wikipedia.org/wiki/Autonomic_dysreflexia

http://emedicine.medscape.com/article/322809-overview#aw2aab6b5

http://calder.med.miami.edu/pointis/automatic.html

http://www.bcm.edu/crowd/reprod/modules/autonomic.html

 

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