What causes neurogenic shock in high-level spinal cord injury?

• A. Loss of parasympathetic tone
• B. Overactive adrenal glands
• C. Excessive breathing
• D. Loss of sympathetic tone

Answer: (D)

Neurogenic shock from a high-level spinal cord injury happens because the sympathetic nervous system’s outflow below the injury is disrupted. When the sympathetic pathways are interrupted, vessels lose their usual constrictor input, so they dilate (vasodilation) and blood pools in the venous system. This lowers systemic vascular resistance and causes hypotension. At the same time, the heart loses sympathetic stimulation, and the parasympathetic (vagal) influence can dominate, leading to bradycardia. The combination of widespread vasodilation and slow heart rate characterizes this distributive shock type, often seen with injuries above the T6 level because most of the sympathetic outflow to the vasculature originates there. Other options don’t produce this pattern: loss of parasympathetic tone wouldn’t cause the same vasodilatory, bradycardic state; adrenal overactivity would raise sympathetic effects rather than diminish them; and excessive breathing isn’t a mechanism for neurogenic shock.