Objective: To investigate the clinical features of early onset narcolepsy.
Methods: The clinical data of 105 consecutive patients with narcolepsy, 63 of which with an onset age of 9.7 +/- 3.1 on average and 42 with an onset age of 22.8 +/- 9.3 on average. Interrogation, physical examination, CT, and MRI were carried out. Polysomnography was conducted. Then the data were compared between these 2 groups.
Results: All 105 patients showed daytime sleepiness. The incidence rate of cataplexy was 92% in the early onset group, significantly higher than that of the late onset group (P = 0.023). There were no significant differences in the rates of sleep paralysis, hypnagogic hallucination, and disturbed nocturnal sleep. Multiple sleep latency test showed that the mean sleep latency of the early-onset group was 4.5 +/- 4.0 min, significantly shorter than that of the late onset group (7.0 +/- 5.7 min, P = 0.018); the REM sleep latency of the early onset group was 3.4 +/- 3.2 min, significantly shorter than that of the late onset group (4.8 +/- 2.2 min, P = 0.02). The number of REM sleep of the early onset group was 3.4 +/- 2.0, significantly more than that of the late onset group (2.5 +/- 1.9, P = 0.09). The apnea and hypopnea index of the late onset group was 9.2 +/- 16.5, significantly higher than that of the early onset group (1.9 +/- 6.3, P = 0.009). The 3 cases of narcolepsy with family history were all cases of early onset narcolepsy.
Conclusion: Early onset narcolepsy patients have more severe daytime sleepiness and higher rate of cataplexy. The pathogenesis of early onset narcolepsy may be more closely associated with genetic factors.