Review Question - QID 107139

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Sleep Sleep Disorders Narcolepsy QID: 107139 (M1.NE.15.4671)

QID 107139 (Type "107139" in App Search)

A 23-year-old woman is seen by her primary care physician. The patient has a several year history of excessive daytime sleepiness. She also reports episodes where she suddenly falls to the floor after her knees become weak, often during a laughing spell. She has no other significant past medical history. Her primary care physician refers her for a sleep study, which confirms the suspected diagnosis. Which of the following laboratory findings would also be expected in this patient?

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Increased serum methoxyhemoglobin

11/161

Reduced serum hemoglobin

7/161

Undetectable CSF hypocretin-1

76%

123/161

Increased CSF oligoclonal bands

9/161

Increased serum ESR

5/161

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This patient most likely has narcolepsy with cataplexy. Undetectable CSF levels of hypocretin-1 is seen in patients with this condition.

Narcolepsy has four major characteristics: (1) rapid, non-preventable transition to sleep during the daytime, (2) onset of REM sleep within several minutes of sleep start, (3) hallucinations while going to sleep or waking up, and (4) sleep paralysis. In addition, some patients also suffer from cataplexy (as in this case), which presents as "drop attacks," when experiencing strong emotion. Although the cornerstone of treatment for most patients includes stimulants and scheduled daytime napping, patients with cataplexy may benefit from additional treatment with an SSRI.

Ramar et al. discuss the presentation of narcolepsy, which has a prevalence of around 0.02% and typically manifests in the teens or twenties. Episodes of cataplexy typically follow an emotional trigger (laughter, anger, surprise) and can manifest in a wide spectrum, ranging from sudden loss of jaw muscle tone (jaw dropping) to complete collapse on the floor (loss of postural muscle tone).

Liblau et al. discuss the role of hypocretin in narcolepsy. They write that narcolepsy with cataplexy is caused by hypocretin deficiency. This is a result of destruction of hypocretin-producing neurons in the hypothalamus, destruction of which in animal models presents with a narcolepsy phenotype. The exact mechanism of hypocretin deficiency is not clear, but research suggests an autoimmune neuron attack.

Incorrect Answers:
Answers 1,2,4, and 5: These findings have no association with narcolepsy with cataplexy. Increased CSF oligoclonal bands is seen with multiple sclerosis.