Rapid Weight Gain in an Excessively Sleepy Girl With Asthma

Timothy D. Murphy, MD


October 09, 2020


This case is very challenging because the patient had the findings of and met the criteria for OSA, periodic limb movement disorder (PLMD)/restless legs syndrome (RLS), and hypersomnolence. She also had several historical findings that were highly suggestive of narcolepsy with cataplexy. These included a strong family history of narcolepsy, a history of the sudden onset of sleep and greatly increased sleep pressure, and rapid weight gain. A critical finding was a nocturnal sleep-onset REM sleep period (SOREMP). A nocturnal SOREMP (defined as REM sleep within 15 minutes of falling asleep) has a very high specificity for narcolepsy with cataplexy in adults and children.[1,2] However, the importance of the nocturnal SOREMP was not initially noted in her evaluation and management.

OSA and PLMD were initially diagnosed, and the otolaryngologist performed an adenotonsillectomy. The patient returned to the pediatric pulmonary and sleep medicine clinic after the procedure. At 3 weeks after the surgery, her somnolence improved very little. She had been gaining weight more rapidly and symptoms of apparent instability in her asthma were noted.

Further history-taking revealed a complex set of interactions around eating (some involved her father catering to her desire for higher-carbohydrate foods), increased sedentary behavior, and a history suggestive of vocal cord dysfunction. She was having "asthma attacks" characterized by rapid onset with inspiratory stridor and rapid resolution at the onset of activity. Her family was willing to make changes in their diet and to encourage activity, and they sought help for the vocal cord dysfunction from a speech and language pathologist.

Despite these measures, her weight gain rapidly progressed and the daytime fatigue and sleepiness continued. The pediatrician referred her to the neurologist who had interpreted the first NPSG. His history presented a differential diagnosis of narcolepsy, primary hypersomnolence, persistent OSA, and PLMD. He recommended a second NPSG with a multiple sleep latency test (MSLT), to be done immediately following the NPSG to assess her sleepiness more formally. His history documented that she felt as if she was "going to fall" when she laughed. He also noted that her father had OSA (treated with CPAP) and that she had an uncle and a grandfather with narcolepsy.

The second NPSG revealed the following:

  • A respiratory disturbance index of 1.4 (improved)

  • Sleep latency of 2.5 minutes and REM latency of 68.5 minutes

  • A sleep efficiency of 68.3%

  • 31.6% of total sleep time in stage N1, 43.8% in N2, 20% in N3, and 4.6% in REM sleep

  • An arousal index of 23.5 (increased)

  • A periodic leg movement index of 5.9 (slightly lower)

  • "3 REM periods, 2 of them were very brief," and a period of wakefulness after sleep onset of 180.5 minutes (increased)

The MSLT showed a mean sleep latency calculated at 9.5 minutes and no sleep onset–associated REM sleep (REM sleep within 20 minutes of sleep onset).

The neurologist provisionally diagnosed narcolepsy (vs hypersomnolence). He prescribed methylphenidate and then gradually increased the dose. Despite slightly improved daytime alertness, the patient started to develop more classic findings of cataplexy. The patient's mother brought her back to the pediatric pulmonary and sleep medicine clinic. Methylphenidate was discontinued and therapy with modafinil was initiated.

When the patient was 9 years old, sodium oxybate was added to her regimen and her condition finally stabilized. Her therapy was complicated by the treatment of her inattention with dextroamphetamine and levoamphetamine (Adderall) and the effects of all of her therapy on her weight. Her rapid weight gain was followed by an equally rapid weight loss, and these changes finally settled into her currently stable pattern of tracking around the 75th percentile after starting sodium oxybate (Figure 2).

Figure 2.


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