Episodic Hypersomnolence Secondary to Baclofen Toxicity in a Patient with an Intrathecal Baclofen Pump with Normal Functional Studies
Mawj Alzakar1, Susan Herman1, Kyle Kaneko1, Josiah Chang1, David Harris1
1Barrow Neurological Institute, Department of Neurology
Objective:
To describe a case of recurrent episodic hypersomnolence secondary to intrathecal baclofen pump toxicity despite negative functional studies.
Background:
Intrathecal baclofen pump provides targeted therapy for muscle spasticity with fewer systemic side effects. Baclofen pump toxicity can present as confusion, hypersomnolence, and encephalopathy. Diagnosis can be difficult in patients with a history of seizures who have normal pump interrogation, side port studies, and roller studies.
Results:
A 30-year-old woman with spastic hemiparesis after arteriovenous malformation resection in early childhood, managed with an intrathecal baclofen pump, with subsequent drug-resistant epilepsy, presented with recurrent discrete episodes of hypersomnolence and confusion progressing to obtundation for 24-48 hours. Brain magnetic resonance imaging showed no acute intracranial abnormalities and electroencephalogram (EEG) during the episodes showed diffuse delta activity, left frontal interictal epileptiform discharges (IEDs), and triphasic waves, but no seizures. Antiseizure medication was escalated for presumed postictal episodes. Although the IEDs on EEG initially improved, frequent episodic hypersomnolence persisted. Mental status between episodes was normal. Prolonged video-EEG monitoring showed no seizures but one episode of progressively deepening sleep, then diffuse slowing and generalized triphasic waves over 24 hours. Side port study, roller study, and pump interrogation of her baclofen pump were all normal. Cerebrospinal fluid and autoimmune encephalitis panel were unremarkable. Despite multiple negative functional studies, baclofen toxicity from her baclofen pump was suspected based on the EEG pattern. Her baclofen pump was replaced and her episodes of hypersomnolence resolved.
Conclusions:
Intrathecal baclofen pump toxicity can occur even with negative diagnostic studies. Persistent, unexplained episodic hypersomnolence in patients on intrathecal baclofen should prompt clinicians to consider pump malfunction and replacement when other causes like seizures have been excluded. Clinical judgment remains essential when diagnostic studies are inconclusive, as timely pump replacement may be both diagnostic and therapeutic.
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