Case 3: Change in personality and daytime sleepiness in a seven-year-old boy

A seven-year-old boy presented to his paediatrician with his mother for learning and school difficulties. During the appointment, the boy fell asleep intermittently; therefore, a referral was made to sleep medicine.

His mother described him as a completely different boy than one year before. At that time, he began to experience difficulty staying awake during the day and would fall asleep when not fully engaged or when sitting still. There were concerns from the school regarding falling asleep in class, learning difficulties, aggression and being teased. On weekends, he would play video games all day to stay awake. Implementation of a strict sleep schedule allowing for 10.5 h of sleep per night resulted in some improvement; however, he continued to be a restless sleeper with frequent singing, sleep walking and occasional snoring. He significantly decreased his activity level and his weight increased. Further history revealed that his sisters had discovered that if they made him laugh, he would fall down. His mother noted that he had previously laughed often but now suppressed it. Around the start of these symptoms, he had an infected tooth treated with penicillin. Medical history was significant for several episodes of tonsillitis and speech difficulties. He was in a modified grade 2 program and lived with his parents and two sisters, one of whom had a seizure disorder secondary to encephalitis.

CASE 3 DIAGNOSIS: NARCOLEPSY

An overnight polysomnogram (sleep study) and multiple sleep latency test (MSLT) were performed. The sleep study revealed short sleep and rapid eye-movement (REM) sleep latency (1 min 54 s and 4 min, respectively). Sleep was fragmented with frequent arousals, stage changes and intrusion of REM sleep into other sleep stages. Despite this, his sleep efficiency (83%) was acceptable. The MSLT revealed a mean sleep latency of 1 min 10 s across five daytime nap opportunities, with REM noted in the first and fifth naps; a mean sleep latency <8 min and REM noted on ≥2 naps is consistent with a diagnosis of narcolepsy (1). Loss of muscle tone with laughter is consistent with cataplexy leading to a diagnosis of narcolepsy type 1 (with cataplexy). A normal neurological examination, electroencephalogram, magnetic resonance imaging of the head and immunological work-up supported primary narcolepsy.

Narcolepsy is a chronic disorder affecting the central nervous system. Its hallmark feature is excessive daytime sleepiness with an irresistible need to sleep. Additional features include episodes of cataplexy, sleep paralysis and hypnogogic/hyponopomic hallucinations, although all of these features occurring together is rare in young children. Worldwide incidence is estimated to be 0.025% to 0.40%, making it a rare disease with significant socioeconomic burden (2,3). Once believed to be a disorder affecting adults, it is now clear that narcolepsy presents in childhood with decades of delayed or misdiagnosis; approximately one-half of adults diagnosed with narcolepsy recall symptoms in childhood (3). Young age of onset is associated with an increased severity, higher frequency of cataplexy and shorter mean sleep latency on MSLT. This may, however, be because symptoms of severe narcolepsy are more readily identified, leading to earlier diagnosis of more severe narcolepsy.

The recognition of narcolepsy in childhood is not easy, with a broad differential for daytime sleepiness (2). This includes common conditions such as inadequate sleep hygiene, obstructive sleep apnea, delayed sleep phase syndrome and mood disorders. The symptoms of narcolepsy in children may be severely life-disrupting and are often misinterpreted as laziness, attention deficit, behavioural, lack of interest or even seizures, particularly absence seizures. Children and adolescents with narcolepsy often present with changes in personality and behaviour, irritability or aggression, poor school performance and have significantly higher rates of depression. These patients may also have alterations of other neurobiological functions such as the mechanism to regulate hunger leading to weight gain. Secondary narcolepsy (ie secondary to another disease, predominantly structural brain lesions resulting from inherited diseases or brain tumours) is found in up to 30% of children; therefore, additional investigations, including head imaging, may be warranted (2). A child who presents with excessive daytime sleepiness not improved by good sleep hygiene should be considered for further investigation of sleep problems.

Narcolepsy is linked to a dramatic reduction of the neuropeptide hypocretin/orexin or its receptors in the brain (4). A deficiency in this neuropeptide presents as REM intrusion into awake state causing sleep attacks and/or episodes of cataplexy, as well as intrusion into other sleep stages causing sleep fragmentation. Studies have shown that approximately 90% of hypocretin-producing neurons are lost in narcolepsy with cataplexy (5). The reason for reduced hypocretin levels is under investigation; however, given the association of narcolepsy with HLA-DQB1*0602, an autoimmune condition is suspected. Several triggers for the autoimmune destruction of hypocretin neurons in the brain of predisposed individuals have been postulated, including an association between H1N1 immunization and an increased incidence of narcolepsy. The patient in the present case did not receive influenza or H1N1 vaccination before symptom onset.

CLINICAL PEARLS

• A sleep history should be obtained for children presenting with abrupt changes in personality, behaviour or mood.

• Daytime sleepiness that does not resolve with good sleep hygiene and age-appropriate sleep duration requires further investigation.

• With increasing awareness and recognition of excessive daytime sleep, an earlier diagnosis of narcolepsy is possible.