Comparison of Narcolepsy with Cataplexy and without Cataplexy: Clinical Variables, HLA-DQB1*0602, and Hypocretin

Jeong, Jong Hyun; Hong, Seung Chul; Shin, Yoon Kyung; Han, Jin Hee; Lee, Sung Pil

Abstract

OBJECTIVES
Narcolepsy is a sleep disorder, characterized by excessive daytime sleepiness, cataplexy, sleep paralysis and hypnagogic hallucination. Among these symptoms, cataplexy is one of the most pathognomonic symptoms in narcolepsy. This study was designed to investigate the clinical features, frequency of DQB1*0602 and CSF hypocretin levels in Korean narcoleptics with cataplexy to compare with those who have not cataplexy.
METHODS
From August 2003 to July 2005, we selected 72 patients who have narcolepsy confirmed by nocturnal polysomnography and multiple sleep latency test (MSLT) as well as their history and clinical symptoms at Sleep Disorders Clinic of St. Vincent's Hospital, Catholic University of Korea. Patients were divided into 56 cataplexy-positive group (narcolepsy with cataplexy group) and 12 cataplexy-negative group (narcolepsy without cataplexy group). HLA typing was done in all patients for the presence of DQB1*0602, and patients received spinal tapping to measure the level of CSF hypocretin. Clinical variables were examined by semi-structured interview for narcolepsy patients.
RESULTS
1) In cataplexy-positive group, compared with cataplexy-negative group, the frequency of HLA-DQB1*0602 was found to be significantly increased (50 subjects, 89.3% vs. 8 subjects, 50.0%)(p=0.000). 2) In 48 out of 56 cataplexy-positive patients (85.7%), hypocretin levels were decreased (< or =110 pg/ml) or were below the detection limit of assay (<40 pg/ml). However, only 6 out of 16 cataplexy-negative patients (37.5%) exhibited decreased hyopcretin level. The difference between two groups were statistically significant (p=0.000). 3) Cataplexy-positive group, compared to cataplexy-negative group, reported more frequent hypnagogic hallucinations (36 subjects, 64.3% vs. 4 subjects, 25.0%)(p=0.005). However, there were no significant differences in frequency or severity of daytime sleepiness, sleep paralysis and demographic data. 4. In nocturnal polysomnography and MSLT findings, there were no significant differences in all sleep parameters between two groups.
CONCLUSION
Higher frequency of HLA-DQB1*0602, and lower hypocretin levels in cataplexy-positive groups than catapelxy-negatives suggest that narcoleptics with cataplexy might be a etiologically different disease entity from narcoleptics without cataplexy. Additionally, Current criteria prevail for the diagnosis of narcolepsy need to be reclassified according to the presence of cataplexy or not.