What is locked-in syndrome, and which functions are preserved?

• A. Brainstem lesion (ventral pons) causing quadriplegia and inability to speak, with preserved consciousness and vertical eye movements.
• B. Cerebral cortex lesion causing aphasia.
• C. Cerebellar lesion causing ataxia.
• D. Spinal cord transection.

Answer: (A)

Locked-in syndrome is a brainstem–based state where a person is fully conscious and aware but cannot move most of the body or speak because the pathways that control voluntary movement are damaged, usually from a ventral pontine lesion. What makes this pattern distinctive is that while the limbs and bulbar muscles are paralyzed, the patient can still follow with the eyes and blink, typically with intact vertical eye movements. That preservation of consciousness and vertical gaze signals that the problem lies in the lower brainstem affecting motor tracts, not in the cerebral cortex or overall brain function. A cerebral cortex lesion would more likely produce aphasia or cognitive changes rather than total paralysis with preserved eye movements. A cerebellar lesion causes coordination problems like ataxia, not this profound, selective loss of voluntary movement with preserved awareness. A spinal cord transection would cut off signals to the body below the injury level, but would not typically spare eye movements or consciousness, and the pattern of intact eye movement with widespread paralysis points to a brainstem ventral lesion.