How should I evaluate a patient with a cervical spinal cord injury for dysautonomia?

Evaluating Dysautonomia in Cervical Spinal Cord Injury

Assess dysautonomia in cervical SCI patients through cardiovascular monitoring (orthostatic vital signs, heart rate variability), sympathetic skin responses, and plasma catecholamine levels, as these directly correlate with injury level and predict life-threatening complications like autonomic dysreflexia and orthostatic hypotension. 1, 2

Clinical Assessment Framework

Cardiovascular Testing (Primary Evaluation)

Orthostatic vital sign monitoring is essential and should be performed systematically:

• Measure continuous heart rate and beat-to-beat blood pressure while supine, then after passive assumption of upright seated position 1
• Document baseline supine values: heart rate, systolic/diastolic/mean arterial pressures 1
• Cervical SCI patients characteristically show: lower supine heart rate, systolic pressure, and absent blood pressure increase when upright (unlike thoracic SCI or controls who show increases) 1
• Calculate stroke volume, cardiac output, and total peripheral resistance to identify impaired cardiovascular compensation 1
• Neurogenic orthostatic hypotension is highly prevalent in cervical SCI patients with autonomic dysreflexia 2

Autonomic Dysreflexia Screening (Critical for High Lesions)

Test for autonomic dysreflexia in all patients with lesions at or above T5:

• Perform bladder filling test: monitor for systolic blood pressure increase ≥20 mmHg, which defines AD 2
• Recognize that 63.6% of AD episodes are asymptomatic, making objective testing mandatory rather than relying on symptoms alone 2
• AD typically develops 2-3 months post-injury in those with lesions above T5 3
• This condition is life-threatening and can cause cerebrovascular complications 3

Sympathetic Skin Response Testing

Sympathetic skin responses (SSR) identify autonomic pathway integrity:

• SSR assessment reveals autonomic completeness, which does not necessarily correlate with motor/sensory completeness on ASIA scale 1
• SSR identifies patients at greatest risk of orthostatic hypotension and impaired cardiovascular control 1
• This test should be included in neurological evaluation in addition to standard ASIA assessment 1

Laboratory Assessment

Measure plasma catecholamines in supine and upright positions:

• Cervical SCI patients show lower noradrenaline levels both supine and upright compared to thoracic SCI and controls 1
• AD patients display dropped sympathetic outflow with decreased noradrenaline plasma levels 2
• Measure vasopressin levels at both positions for comprehensive autonomic profiling 2

Advanced Autonomic Function Testing

Perform standardized autonomic tests:

• Deep breathing test to assess parasympathetic function 2
• Valsalva maneuver to evaluate integrated autonomic responses 2
• Tilt table test for comprehensive orthostatic assessment 2
• Baroreflex sensitivity (BRS) measurement: AD patients show increased BRS indicating decreased sympathetic activity 2
• Spectral analysis of heart rate and blood pressure variability at rest to quantify sympathovagal balance 2

Injury Level-Specific Considerations

Cervical injuries (above T5) result in the most severe dysautonomia:

• Parasympathetic (vagal) control remains intact while spinal sympathetic circuits lose supraspinal control 4
• Injuries below T5 preserve both sympathetic and parasympathetic control of heart and bronchopulmonary tree 4
• Injury level and severity directly correlate with severity of autonomic dysfunction 4

Critical Pitfalls to Avoid

• Do not rely solely on ASIA motor/sensory assessment to determine autonomic completeness—SSR testing is required 1
• Do not assume symptomatic presentation of autonomic dysreflexia—most episodes are silent 2
• Do not delay autonomic assessment until chronic phase—acute phase autonomic imbalance affecting cardiovascular and respiratory systems may be life-threatening 3
• Do not overlook thermoregulatory dysfunction, which affects pressure sore risk from the moment of injury 3, 5

Acute Phase Monitoring

In the acute phase, monitor for life-threatening complications:

• Cardiovascular instability requiring continuous monitoring 3
• Risk of over-hydration leading to pulmonary edema or hyponatremia 3
• Paralytic ileus causing vomiting/aspiration risk 3
• Temperature dysregulation 3, 5