The Cushing response, also known as the Cushing reflex, is a physiological nervous system reaction to increased intracranial pressure in the setting of severe brain injury, impending brain herniation or neuroendoscopic procedures 1. It is characterized by a triad of signs 1-4:
hypertension
bradycardia
irregular breathing or apnea.
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Hypertension
In the Cushing response, hypertension is observed as a compensatory mechanism that attempts to maintain cerebral perfusion pressure and thus cerebral blood flow despite elevated intracranial pressure 1,2.
Bradycardia
Bradycardia is thought to be a response to hypertension, resulting from the activation of baroreceptors, which trigger a parasympathetic response that slows the heart rate. It is often preceded by a brief period of tachycardia 1,2. The exact mechanism behind bradycardia in the Cushing reflex is still debated, with some suggesting it may also be due to direct compression of the vagal nerve by increased intracranial pressure, or distortion of the floor of the third ventricle 1.
Apnea/irregular breathing
Apnea or irregular breathing occurs due secondary to compression of the brainstem, where the respiratory centers are located. This can progress to agonal breathing and eventually respiratory arrest.
History and etymology
The Cushing reflex was first described in 1901 by Harvey Williams Cushing (1869-1939), a pioneering American neurosurgeon 4.
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