Axial T2 MRI. Early-stage pontine basis stroke. Clot visualizable. Asymmetric, partial locked-in syndrome on exam.
Pontine Stroke: Locked-In Syndrome
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OVERVIEW
In locked-in syndrome, the pontine basis and ventral tegmentum are injured, causing devastating paralysis, which is often misperceived as coma when in reality consciousness is preserved.
CLINICAL CASE
Patient is found in an apparent comatose state. Exam reveals normal pupil reactivity, normal vertical eye movements, volitional blinks, complete bilateral face and body paralysis, normal sleep–wake states, and an absent gag reflex.
EXPLANATION
Paralysis of the face results from destruction of the exiting facial motor nerve fibers. The facial nucleus, itself, lies within the dorsal pons and is spared.
Paralysis of horizontal eye movements in this case results from destruction of the PPRF; note that although most of the reticular formation is spared, this small portion is injured. Volitional vertical eye movements are spared because the center for volitional vertical eye movements lies within the midbrain (above the level of the lesion).
The patient’s ability to blink results from the ability to elevate and retract the upper eyelids through spared third nerve innervation of the levator palpebrae and through third nerve relaxation, which passively closes the eyelids. Orbicularis oculi is required for forced eyelid closure; it is innervated by the facial nerve, which is injured in this syndrome.