Narcolepsy With Cataplexy
Case Presentation
Mr. A, a 21-year-old college student, came to a sleep disorders center for evaluation of excessive daytime sleepiness. This symptom started at age 11, when he and his family noticed that he seemed to need more sleep than his peers. At age 13, he had daily spells of a sudden inability to move that were consistently triggered by laughter. During these episodes, his head would nod or his knees would buckle, but he would not fall down. These phenomena are consistent with cataplexy. The patient also experienced incidents of inability to move for several minutes after awakening from sleep, which indicated sleep paralysis, and he had nightly dreams that he described as “very real.” These vivid dreams featured activities he had been engaged in during the preceding day. When the patient was 14, he had an overnight polysomnogram, which his parents reported gave no explanation for his symptoms. The records of that previous sleep study were unavailable for review.After high school, the patient’s excessive daytime sleepiness and cataplexy persisted. He attended college but struggled academically, with a grade point average of 2.0 on a 4.0-point scale. His description of his sleeping habits indicated an altered sleep-wake pattern. He would typically stay awake until 2:00 or 3:00 a.m. watching television or listening to music. After falling asleep, he often awakened several times during the night.Although Mr. A had a history of ongoing nicotine dependence, he reported no past history of psychiatric disorders such as major depression or chemical dependency. He had no record of any learning disorder. His medical history and surgical history were significant only for a tonsillectomy.The patient was attending community college and living at home with his parents. He was socially active and spent considerable time with friends or working out in the gym. He drove a motor vehicle short distances on a daily basis and reported no motor vehicle accidents. He had no known family history of a sleep disorder or a psychiatric disorder.A mental status examination showed Mr. A to be alert and able to make good eye contact. His speech and language skills were normal. His mood was slightly anxious, and his affect was appropriate. His thought form was unremarkable, and his thought content lacked any delusional thinking or hallucinations. A Mini-Mental State Examination revealed no cognitive impairment.
Diagnostic Evaluation
A sleep evaluation was conducted that consisted of activity monitoring with a portable motion detector on the wrist, overnight polysomnography, and a multiple sleep latency test. Mr. A was not taking any medications at the time of testing. He rated himself as 24 out of 24 on the Epworth Sleepiness Scale (2), a widely used self-report rating of sleepiness. Wrist activity monitoring conducted for 1 week revealed a fairly irregular sleep-wake pattern with a delayed sleep phase and a short total sleep time (mean=5 hours per night). Polysomnography confirmed the absence of sleep-disordered breathing or excessive periodic limb movements. Mr. A had a total sleep time of 430 minutes (7.2 hours) and a normal initial latency of 88 minutes to REM sleep. He did get sufficient sleep during polysomnography to proceed with a multiple sleep latency test the next day. The starting time was adjusted to account for his typically delayed sleep. The multiple sleep latency test showed a markedly short mean initial sleep latency of 30 seconds and the presence of REM sleep during all four naps. A urine drug screen done the same day was negative for any drug of abuse. Testing for the human leukocyte antigen (HLA) revealed the presence of the DQB1*0602 allele. In the context of a delayed sleep phase disorder and insufficient sleep, these data supported the diagnosis of narcolepsy with cataplexy. However, Mr. A declined a lumbar puncture to collect cerebrospinal fluid (CSF) for a measurement of his hypocretin-1 level; narcolepsy has been attributed to low concentrations of this neuropeptide (3).
Treatment
Mr. A was counseled about the importance of adequate sleep hygiene, which involved establishing a consistent schedule and obtaining sufficient sleep time, at least 7 hours. He indicated a willingness to make obtaining adequate sleep a higher priority. Methylphenidate hydrochloride, 10 mg h.s., and time-release methylphenidate hydrochloride, 18 mg h.s., were tried sequentially for a few days. The patient discontinued each sleep aid after a few days because it made him “feel strange.” Treatment with modafinil, 100 mg every morning, was better tolerated but only partially effective for his excessive daytime sleepiness. Mr. A did not tolerate higher doses of this novel agent because it precipitated headache. He was given a prescription for amphetamine-dextroamphetamine, 10 mg every morning, and tolerated a gradual increase in the dose to 50 mg/day. His reported excessive daytime sleepiness was reduced from 23 to 15 on the Epworth Sleepiness Scale.Not unexpectedly, the patient’s cataplectic episodes triggered by laughter continued to occur daily. To target the cataplexy, Mr. A began taking a morning dose of 25 mg of the tricyclic antidepressant imipramine hydrochloride. This medication effectively reduced the frequency of his cataplectic episodes. However, Mr. A did not always take this medication because of its side effects, most notably dry mouth and constipation. He was then given sertraline, 50 mg/day, which he tolerated better and which improved his compliance. His cataplectic attacks decreased from daily events to several episodes a week.Mr. A also made an effort to improve his sleep schedule. He indicated that he had set a more consistent bedtime closer to midnight than 2:00 a.m. However, he continued to awaken several times each night. The addition of zolpidem tartrate, 5 mg h.s., to his medication regimen helped improve the continuity of his sleep somewhat from midnight to 3:00 a.m. However, he continued to awaken frequently after 3:00 a.m.Despite trials of multiple medications, Mr. A continued to have unsatisfactory, excessive daytime sleepiness, cataplexy, and poor sleep. His intolerance of various medications limited his treatment options. His partial lack of adherence with the recommended sleep hygiene measures also contributed to his ongoing symptoms. In particular, he had difficulty conforming to the earlier bedtime and developing a more consistent sleep schedule, which is not uncommon for patients attending college. Although he withdrew from several classes, his academic performance remained poor. We then recommended sodium oxybate, a medication approved by the U.S. Food and Drug Administration (FDA) for the treatment of cataplexy, as an adjunct to the amphetamine-dextroamphetamine. Mr. A was given extensive patient education materials about sodium oxybate. Because of the possibility of synergistic effects of sodium oxybate and other hypnotic medications, Mr. A’s zolpidem was discontinued. A starting dose of 2.25 g of sodium oxybate was to be taken after Mr. A got into bed, and a second dose was to be taken 3 hours later. With this medication, the quality of Mr. A’s sleep improved and he reported feeling more refreshed in the morning. His excessive daytime sleepiness was somewhat reduced, and he gave his sleepiness a rating of 14. The sleep paralysis and hypnagogic hallucinations also resolved, but the cataplexy persisted albeit with decreased frequency.When the dose of sodium oxybate was increased to 3.00 g twice nightly, his excessive daytime sleepiness and the frequency of his cataplexy continued to improve. However, at this higher dose, he was observed wandering around the house at night but had no recollection of his behavior. In the morning, he would sometimes find objects that he had presumably moved during the night. On one occasion, he wet his bed. The sodium oxybate most likely precipitated his sleepwalking and his single episode of enuresis. Mr. A was advised about how he might modify his sleep environment to reduce the possibility of injury. At follow-up 6 months later, he was continuing to take the same medications.
Discussion
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