Levin syndrome).
A. Recurrent periods of an irrepressible need to sleep. Iapsing into sleep, or napping oc- curring within the same day. These must have been occurring at least three times per week over the past 3 months.
B. The presence of at least one of the following: 1. Episodes of cataplexy, defined as either (a) or (b), occurring at least a few times per month: a. In individuals with Iong-standing disease, brief (seconds to minutes) episodes of sudden bilateral loss of muscle tone with maintained consciousness that are precipitated by laughter or joking.
b. In children or in individuals within 6 months of onset, spontaneous grimaces or jaw-opening episodes with tongue thrusting or a global hypotonia, without any obviods emotional triggers.
2. Hypocretin deficiency, as measured using cerebrospinal fluid (CSF) hypocretin-1 immunoreactivity values (less than or equal to one-third of values obtained in healthy subjects tested using the same assay, or less than or equal to 110 pg/mL).
Low CSF levels of hypocretin-1 must not be obsen/ed in the context of acute brain injury, inflammation. or infection.
3. Nocturnal sleep polysomnography showing rapid eye movement (REM) sleep Ia- tency less than or equal to 15 minutes, or a multiple sleep latency test showing a mean sleep latency less than or equal to 8 minutes and two or more sleep-onset
REM periods.
Specify whether: 347.00 (647.419) Narcolepsy without cataplexy but with hypocretin deficiency: Cri- terion B requirements of low CSF hypocretin-1 levels and positive polysomnography/ multiple sleep latency test are met. but no cataplexy is present (Criterion B1 not met).
347.01 (647.411) Narcolepsy with cataplexy but without hypocretin deficiency:
In this rare subtype (less than 5% of narcolepsy cases), Criterion B requirements of cataplexy and positive polysomnography/rnultiple sleep latency test are met, but CSF hypocretin-1 levels are normal (Criterion B2 not met).
347.00 (647.419) Autosomal dominant cerebellar ataxia, deafness, and narco- lepsy: This subtype is caused by exon 21 DNA (cytosine-5)-methyltransferase-1 mu- tations and is characterized by Iate-onset (age 30—40 years) narcolepsy (with low or intermediate CSF hypocretin-1 levels), deafness, cerebellar ataxia, and eventually de- mentia.
347.00 (647.419) Autosomal dominant narcolepsy, obesity, and type 2 diabetes:
Narcolepsy, obesity, and type 2 diabetes and low CSF hypocretin-1 levels have been described in rare cases and are associated with a mutation in the myelin oligodendro- cyte glycoprotein gene.
347.10 (647.429) Narcolepsy secondary to another medical condition: This sub- type is for narcolepsy that develops secondary to medical conditions that cause infec- tious (e.g., Whipple‘s disease. sarcoidosis), traumatic, or tumoral destruction of hypocretin neurons.
Coding note (for |CD-9-CM code 347.10 only): Code first the underlying medical con- dition (e.g., 040.2 Whipple’s disease; 347.10 narcolepsy secondary to Whipple’s dis- ease).
Specify current severity:
Mild: Infrequent cataplexy (less than once per week), need for naps only once or twice per day, and less disturbed nocturnal sleep.