2026 American Academy of Neurology Abstract Website

Objective:

To describe a rare case of reversible ventral brainstem syndrome secondary to alternating overdrainage and underdrainage of a ventriculoperitoneal shunt.

Background:

Brainstem dysfunction secondary to cerebrospinal fluid (CSF) shunting is a rare but potentially reversible complication. Alternating episodes of overdrainage and underdrainage can produce mechanical traction and compression of ventral brainstem structures, resulting in impaired consciousness, cranial nerve palsies, and extrapyramidal symptoms.

Design/Methods:

We describe the clinical evolution, neuroimaging features, and therapeutic response of a 21-year-old man with congenital hydrocephalus who developed a ventral brainstem syndrome following valve replacement of a ventriculoperitoneal (VP) shunt.

Results:

A 21-year-old male with a history of congenital hydrocephalus underwent VP shunt valve replacement due to suspected malfunction. Fifteen days later, he developed psychomotor slowing, hypomimia, somnolence, and marked rigidity with severe bilateral upper limb tremor. A left abducens palsy (VI) and a right oculomotor palsy (III) were found during examination, indicating pontine and ventral midbrain involvement.
Neuroimaging revealed alternating ventricular dilatation and collapse, with initial overdrainage and subsequent underdrainage, which is consistent with dynamic brainstem distortion. The patient underwent endoscopic third ventriculostomy and valve adjustment. Subsequently, levodopa was initiated, producing a clear improvement in rigidity and tremor, while modafinil was added for persistent hypersomnolence. Over the following weeks, his level of alertness and motor function progressively improved, with full resolution of cranial nerve deficits.

The patient achieved functional independence and continued to recover during rehabilitation.

Conclusions:

This case highlights a rare and reversible ventral brainstem syndrome secondary to alternating CSF overdrainage and underdrainage after VP shunt manipulation. Early recognition and timely management—including ventriculostomy, valve readjustment, and symptomatic therapy with levodopa and modafinil—can lead to complete neurological and functional recovery.