The Cushing reflex (Cushing response) consists of hypertension, bradycardia, and irregular respiration. Which pathophysiological sequence accurately explains this triad?

• A Elevated ICP → systemic hypotension → baroreceptor reflex hypertension → reflex tachycardia
• B Elevated ICP → cerebral ischemia → sympathetic surge → hypertension → baroreceptor-mediated bradycardia; respiratory irregularity reflects brainstem compression ✓
• C Cerebral ischemia activates vagal centers → bradycardia → reflex hypertension via systemic vasoconstriction
• D Compression of cranial nerve X directly causes bradycardia without medullary ischemia

Explanation

The Cushing reflex is a last-ditch emergency response to cerebral ischemia from severe raised ICP. Ischemia of the vasomotor center in the medulla triggers a massive sympathetic discharge → systemic vasoconstriction → hypertension (MAP may reach 200+ mmHg). The resulting hypertension activates baroreceptors → parasympathetic (vagal) bradycardia. The medullary respiratory centers, being compressed, produce irregular/ataxic breathing (Biot's or Cheyne-Stokes pattern). This triad indicates impending herniation — a neurological emergency requiring immediate ICP reduction.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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