Introduction:
Narcolepsy is an uncommon sleep disorder characterized by excessive
daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep
paralysis. It occurs in about 44.3 per 100,000 people1. Sleepiness is the core symptom in these patients
and is seen in nearly all patients. Cataplexy is the second most common
symptom; hypnagogic hallucinations and sleep paralysis are less common
associations. Patients with narcolepsy usually present with a few of
these primary symptoms; All symptoms rarely occur in the same patient
simultaneously 1.
The International Classification of Sleep Disorders (ICSD-3) categorizes
narcolepsy into two types: Type 1 narcolepsy (NT1), which is associated
with cataplexy, and type 2 narcolepsy (NT2), which presents without
cataplexy 2,3. Pathophysiologically, NT1 is
differentiated from NT2 in that it is associated with the loss of
hypocretin-producing cells in the lateral
hypothalamus4. Thus, NT1 may be a distinct
pathological entity from NT2 and idiopathic
hypersomnia4. The neuropeptide hypocretin(also called
orexin) plays a role in sustaining wakefulness and suppressing
rapid-eye-movement sleep5. The loss of
hypocretin-producing neurons thus results in loss of sleep continuity
and breaks the border between sleep and wakefulness.
Narcolepsy may occur secondarily to other conditions (e.g. Parkinson’s
disease, Niemann-Pick type C, and various vascular, neoplastic, or
inflammatory lesions involving the lateral hypothalamic
area)2. Numerous studies have postulated that
narcolepsy may be an autoimmune disorder resulting in a loss of
hypothalamic neurons expressing hypocretin5-8.
Notably, almost all patients with NT-1 have the HLA DQB1*0602 variant
that regulates T-cell immunity in viral and bacterial
infections9.
On the other hand, COVID-19 has been associated with many neurological
sequelae10. Since the incidence of narcolepsy has been
previously shown to increase during the H1N1 pandemic in China and
vaccinations11,12, researchers have called for
particular attention to its occurrence in the setting of the current
pandemic as a unique opportunity for a better understanding of its
clinical and biological features13.
We present the case of a woman who presented with classical symptoms of
narcolepsy that had started following her recovery from COVID-19. Since
there are many immune-mediated presentations after COVID-19
infection10, we propose that our patients’ narcolepsy
had para-infectious pathogenesis.