Corticosteroid-responsive narcolepsy type II after COVID-19: A relevant differential diagnosis of post-COVID syndrome (a case report).

Excessive daytime sleepiness is a possible symptom of post-COVID syndrome and is also the cardinal symptom of narcolepsy, a rare life-long sleep disorder with a possible autoimmune background. Recent reports indicate that COVID-19 infection may trigger narcolepsy. However, it remains unclear how best to identify and treat such cases. A 25-year-old male developed daytime sleepiness after COVID-19 infection. A diagnosis of narcolepsy type II was made based on pathologically shortened sleep latencies in polysomnography and multiple sleep latency tests (MSLT) together with several sleep-onset REM-sleep periods (SOREMs). Pupillography and neuropsychological testing revealed reduced alertness levels. Hypocretin levels in the cerebrospinal fluid were borderline. Based on the postulated autoimmune background of narcolepsy, we performed an intravenous high-dose corticosteroid pulse therapy with methylprednisolone. Narcoleptic symptoms immediately and consistently remitted after the corticosteroid pulse. Follow-up after 4 months revealed normalisation of sleep latencies, no further SOREMs in the MSLT, and increased alertness in pupillography and neurocognitive testing. No further wakefulness promoting drug therapy was required. Narcolepsy should be considered in the differential diagnosis of post-COVID syndrome with leading symptoms of daytime sleepiness. Furthermore, immunosuppressive therapy may offer a treatment option in managing an otherwise lifelong disorder in select cases.