An 18-year-old man comes to the physician for daytime sleepiness lasting several months. The patient recently started college, has difficulty staying awake during classes, and often falls asleep suddenly even though he "gets a good night's sleep." He typically goes to bed at 2 am and sleeps until at least 9 am, usually later. The patient's sleep pattern at night is fragmented. He wakes frequently but is usually able to go back to sleep within a few minutes. He does not snore or wake up gasping. The patient feels like "someone is in the room with me when I'm just falling asleep and I sometimes hear my name being called." His past medical history is otherwise insignificant. The patient does not use tobacco or alcohol. Blood pressure is 120/70 mm Hg and heart rate is 70/min. His body mass index is 23 kg/m². Item 1 of 3
Which of the following is the best next step in diagnosing the cause of this patient's symptoms?

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Explanation: 11ec2b69_bffe_cd3d_8f63_7f44f0edd6f7_MD0005_00 Insufficient sleep is the most common cause of excessive daytime sleepiness (EDS). Other common causes can include medication effects, alcohol or illicit drug use, and obstructive sleep apnea. However, in addition to EDS, this patient experiences fragmented sleep, hypnagogic hallucinations, and the sudden onset of sleep during the day, features consistent with narcolepsy. The typical age of onset for narcolepsy is late teens to early 20s. Polysomnography (sleep study) can diagnose narcolepsy; characteristic findings include multiple spontaneous awakenings and reduced sleep efficiency (total sleep time divided by total recording time) and latency of rapid eye movement (REM) sleep. Polysomnography can also exclude other causes of EDS (eg, sleep apnea). (Choice A) CT scan of the head can be useful for identifying signs of increased intracranial pressure (ICP) that can cause EDS. However, this patient lacks other features of increased ICP (eg, headaches, nausea/vomiting, gait disturbances). (Choice B) Absence seizures are characterized by repetitive staring spells and can be documented with electroencephalography. This patient's excessive daytime sleepiness and hypnagogic hallucinations are unlikely to represent absence seizures. (Choice C) Hypnagogic hallucinations (eg, feelings of people walking around, hearing one's name called on falling asleep) are not evidence of psychiatric disease but are characteristic of narcolepsy. They are likely to result from a combination of REM sleep dreaming and wakefulness. (Choice D) A sleep diary can document a patient's sleep pattern over several weeks and is helpful for evaluating circadian rhythm disorders. This patient has a delayed sleep phase (late to bed, late to rise), which is common at his age. This patient seems to get an adequate amount of sleep (at least 7 hours nightly), making a sleep study a more useful diagnostic test. Educational objective: Excessive daytime sleepiness (EDS) is a common symptom and is most commonly caused by insufficient sleep. However, narcolepsy should be considered in a young patient with EDS, especially if the patient also experiences falling asleep suddenly at inappropriate times, hypnagogic hallucinations, or cataplexy. References: Excessive daytime sleepiness. (http://www.ncbi.nlm.nih.gov/pubmed/19275068)

An 18-Year-Old Man Comes to the Physician for Daytime Sleepiness