Cataplexy Mistaken for Seizures in a Patient With Undiagnosed Narcolepsy Type I

TL;DR

A young man with undiagnosed narcolepsy type 1 had cataplexy mistaken for seizures, highlighting the need for thorough clinical evaluation and proper diagnostic tests.

Contribution

This case emphasizes the diagnostic challenges of cataplexy and the importance of using PSG and MSLT for accurate narcolepsy diagnosis.

Findings

Anti-seizure medications were ineffective in treating the patient's symptoms.

Ambulatory EEG revealed no epileptic activity during events, leading to further investigation.

Polysomnogram and mean sleep latency test confirmed the diagnosis of narcolepsy type I.

Abstract

Narcolepsy Type 1 is a sleep disorder, with cataplexy as its cardinal feature, characterized by sudden decrease or loss of muscle tone triggered by strong emotions. Cataplexy can be misdiagnosed as epileptic seizures given its clinical similarity to atonic seizures. The low prevalence of the disease added another layer of complexity in providing timely and accurate diagnosis. We report a case of a young man with recurrent episodes of falling and an inability to respond, initially misinterpreted as epileptic seizures due to findings in routine electroencephalography (EEG). Anti-seizure medications were ineffective, and subsequent ambulatory EEG revealed no epileptic activity during events. A detailed history uncovered symptoms of cataplexy and daytime sleepiness, leading to the correct diagnosis of narcolepsy type I confirmed by polysomnogram (PSG) and mean sleep latency test (MSLT). Discontinuation of anti-seizure medications and treatment with venlafaxine successfully resolved cataplexy. The case highlights the importance of a thorough clinical history in distinguishing cataplexy from seizures, as well as the caution against relying solely on EEG findings for epilepsy diagnosis. Ambulatory EEG can help exclude epileptic events, and PSG with MSLT are necessary to confirm narcolepsy type I.

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