Periodic Limb Movements during Sleep in Children with Narcolepsy

Study Objectives: In adults with narcolepsy, periodic limb movements of sleep (PLMS) occur more frequently than in control population, and presence of increased PLMS is associated with greater sleep disruption and shorter mean sleep latency. This study was performed to determine whether PLMS are common in children with narcolepsy, and whether the presence of PLMS is associated with greater sleep disruption. Design: Demographic and polysomnographic information were collected from consecutive patients diagnosed with narcolepsy identified retrospectively by diagnosis-based search. Descriptive data were compiled, and sleep characteristics of children with and without PLMS were compared. Setting: Sleep disorders center in a children's hospital. Patients: 44 patients, 6-19 years old (mean 13 years, SD 3.57), were identified. Twenty-eight were African American. Interventions: None. Measurements and Results: Four patients had a PLMS index (PLMI) >= 5/h (considered abnormal in literature). Sixteen (36%) had "any PLMS" (PLMI > 0/h). The mean PLMI was 1.3/h (SD 2.5). Sleep was significantly more disrupted, and the mean sleep latency was shorter in patients with "any PLMS" as compared to those with no PLMS. There was no correlation between the PLMI and other diagnostic criteria for narcolepsy. "Any PLMS" were present equally in children of African American and Caucasian heritage, 35.7% vs. 37.5%. Conclusions: As in adults, children with PLMS and narcolepsy have more sleep disruption and shorter mean sleep latencies than those with narcolepsy but without PLMS. Our findings also suggest that the use of adult criteria for diagnosis of "significant" PLMS in children may not be sufficiently sensitive.