Epidemiology Pathophysiology and Clinical Features

The frequency of autonomic dysreflexia varies widely, but appears to be relatively common in spinal cord-injured patients with a lesion at or above the sixth thoracic neurologic level (T6). Sometimes autonomic dysref-lexia is also seen in paraplegic patients with lesions below T6, but usually the clinical presentation is milder. Lifetime frequency of autonomic dysreflexia is between 19% and 85% (Snow et al. 1978; Braddom and Rocco 1991; Shergill et al. 2004). In particular, patients with cervical lesions (60%) show autonomic dysreflexia compared to patients with thoracic lesions (20%).

In healthy persons, an afferent stimulus enters the spinal cord and then ascends to the brain. Some inter-neurons are reflexively connected with preganglionic sympathetic neurons and excite them, resulting in va-

soconstriction below the neurologic lesion and causing a rise in blood pressure. In neurologically intact persons, higher centers inhibit these sympathetic effects by a compensatory vasodilatation of the splanchnic bed, resulting in normalized blood pressure.

In SCI patients, these higher inhibitory pathways are not intact and cannot reach the splanchnic bed, resulting in high blood pressure. As a parasympathetic reflex, the heart beat is also reduced (bradycardia). Typical clinical signs and symptoms are:

Sudden severe hypertension

• Bradycardia (tachycardia is also possible) Severe pounding headache

• Flushed (reddened) face Paresthesia neck, shoulder, and arms

Nasal congestion Blurred vision Tightness in chest Nausea

• Feeling of anxiety and agitation Arrhythmia

Bladder and bowel contraction Penile erection

Sweating and red blotches above the level of spinal cord injury

• Piloerection (goose bumps) and cold, clammy skin below the level of spinal cord injury

It is important to note that the resting blood pressure decreases after a spinal cord injury. Often a blood pressure of 90/60 mmHg is normal for SCI patients and this means that even a normal blood pressure of 120/ 80 mmHg might be considered increased. If possible, SCI patients should be asked for their normal resting blood pressure.

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