Which brain death criterion is assessed using caloric stimulation with ice water?

Which brain death criterion is assessed using caloric stimulation with ice water?

• A. Pupillary light reflex
• B. Corneal reflex
• C. Oculocephalic reflex
• D. Caloric responses to ice water stimulation

Answer: (D)

This tests the vestibulo-ocular reflex, a brainstem-mediated eye movement pathway. When ice-cold water is irrigated into the ear, it drives endolymph flow in the horizontal semicircular canal and should provoke a predictable nystagmus if the brainstem circuits are intact. If that caloric-induced eye movement is absent, it signals loss of brainstem function, which is a key part of brain death assessment. The other reflexes test different brainstem connections—pupillary reactions involve the midbrain, corneal reflex uses trigeminal and facial nerves, and the oculocephalic (doll’s eyes) response tests eye movements with head movement—but the caloric response specifically measures the vestibulo-ocular axis.

This tests the vestibulo-ocular reflex, a brainstem-mediated eye movement pathway. When ice-cold water is irrigated into the ear, it drives endolymph flow in the horizontal semicircular canal and should provoke a predictable nystagmus if the brainstem circuits are intact. If that caloric-induced eye movement is absent, it signals loss of brainstem function, which is a key part of brain death assessment. The other reflexes test different brainstem connections—pupillary reactions involve the midbrain, corneal reflex uses trigeminal and facial nerves, and the oculocephalic (doll’s eyes) response tests eye movements with head movement—but the caloric response specifically measures the vestibulo-ocular axis.