Which sign or test is primarily used to assess brainstem function in a coma by turning the head?

• A. Romberg test
• B. Kernig sign
• C. Babinski sign
• D. Doll's Eyes Test

Answer: (D)

The test relies on the oculocephalic reflex, the Doll's eyes response. When the head is rapidly turned from side to side in a comatose patient, a functioning brainstem makes the eyes move together in the opposite direction to the head turn to keep looking forward. This head-rotation test specifically probes the brainstem pathways that control eye movements through vestibular and ocular motor circuits in the midbrain and pons. If the eyes move oppositely, brainstem function is preserved; if the eyes fail to move correctly or stay fixed with the head, that signals brainstem dysfunction and often a worse prognosis. Other signs mentioned assess different systems—Romberg looks at proprioception and cerebellar/vestibular function, Kernig tests meningeal irritation, and Babinski checks corticospinal tract integrity—so they don’t directly measure the brainstem oculomotor reflex the way the Doll's Eyes test does.