CSF-profile and hypocretin levels in children with narcolepsy type 1 and 2

Narcolepsy is a rare neurological disease caused by dysfunction of hypocretin-producing neurons. Hypocretin concentrations in the cerebrospinal fluid (CSF) of less than 110 pg/ml are considered pathological in adults. To compare hypocretin levels of children with narcolepsy type 1, type 2 and disease control groups, in addition to a detailed CSF analysis, clinical and polysomnographic parameters. In a retrospective, cross-sectional study, children diagnosed with narcolepsy based on clinical and polysomnographic parameters, who received a CSF analysis and hypocretin measurement, in addition to controls, were included. CSF was analyzed for the presence of cells, total protein, lactate, intrathecal synthesis of antibodies against measles, rubella and/or varicella zoster, and oligoclonal bands. All children had a complete sleep study including a multiple sleep latency test (MSLT). 49 children with narcolepsy type 1, 15 children with type 2 and 37 children with other (suspected) neurological diseases were included. CSF routine analysis did not reveal any differences between the three groups. All children with narcolepsy type 1 had hypocretin levels of less than 110 pg/ml (range: 10–101 pg/ml). Hypocretin levels in type 2 patients ranged from 43 to 436 pg/ml (median 157 pg/ml). The median hypocretin level in the control cohort was 365 pg/ml (range: 153–583 pg/ml). In 4 children with narcolepsy type 2 the diagnosis was changed to narcolepsy level 1 because of a CSF hypocretin level of less than 110 pg/ml according to the recently proposed criteria, which consider the measurement of hypocretin in CSF. Children with narcolepsy type 1 showed significantly lower CSF hypocretin levels than children with narcolepsy type 2 and controls. As suggested by the recently published narcolepsy criteria, hypocretin levels of less than 110 pg/ml should be used as an additional criterion for the presence of narcolepsy type 1 in children.