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|TOPIC OF THE ISSUE: ORIGINAL ARTICLE
|Year : 2012 | Volume
| Issue : 1 | Page : 75-78
Clinical and polysomnographic characteristics in 20 North Indian patients with narcolepsy: A seven-year experience from a neurology service sleep clinic
Anupama Gupta, Garima Shukla, Vinay Goyal, Achal Srivastava, Madhuri Behari
Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||18-Jul-2011|
|Date of Decision||27-Aug-2011|
|Date of Acceptance||26-Dec-2011|
|Date of Web Publication||7-Mar-2012|
Room no. 2, 6th Floor, Department of Neurology, Neurosciences Center, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
Background: Narcolepsy is not an uncommon sleep disorder in the West. There is, however, only one reported case in literature from India. In this study, we report characteristics of patients with narcolepsy over a seven-year period. Materials and Methods: Details of all patients with narcolepsy seen at a Sleep Disorders Clinic over seven years were analyzed. Diagnosis had been established by clinical history and two or more Sleep Onset Rapid Eye Movement Periods (SOREMPs) on Multiple Sleep Latency Test (MSLT) following an overnight Polysomnography (PSG), using the International Classification of Sleep Disorders - 2 (ICSD-2) criteria. Patients fulfilling the criteria, but suffering from other disorders were excluded. Results: Data of 20 patients were analyzed and 4 patients were excluded, as they had other associated conditions. Mean age at onset of symptoms was 25±10 years; 12 (60%) patients had narcolepsy with cataplexy, 4 (20%) patients presented with all cardinal symptoms of narcolepsy, 8 (40%) with 3 symptoms, while 8 (40%) presented with 2 symptoms. History of Excessive Day-Time Sleepiness (EDS) was present in all patients. Three patients reported accidents due to sleep attacks, one being life-threatening. On PSG, mean sleep efficiency was 79.4±12.40%. Mean sleep latency during MSLT was 1.30 minute (range: 0.30-2.30 minute) and mean REM latency was 2.58±0.64 minute. Conclusion: Narcolepsy with and without cataplexy is infrequently seen in the North Indian population; however, clinical and polysomnographic features are similar to those observed in Western and other Asian populations.
Keywords: Cataplexy, multiple latency test, narcolepsy, polysomnography
|How to cite this article:|
Gupta A, Shukla G, Goyal V, Srivastava A, Behari M. Clinical and polysomnographic characteristics in 20 North Indian patients with narcolepsy: A seven-year experience from a neurology service sleep clinic. Neurol India 2012;60:75-8
|How to cite this URL:|
Gupta A, Shukla G, Goyal V, Srivastava A, Behari M. Clinical and polysomnographic characteristics in 20 North Indian patients with narcolepsy: A seven-year experience from a neurology service sleep clinic. Neurol India [serial online] 2012 [cited 2019 Sep 16];60:75-8. Available from: http://www.neurologyindia.com/text.asp?2012/60/1/75/93602
| ╗ Introduction|| |
Narcolepsy is a chronic sleep disorder characterized by Excessive Day Time Sleepiness (EDS) in the form of sleep attacks along with abnormal Rapid Eye Movement (REM) sleep events such as cataplexy, hypnagogic hallucinations, and sleep paralysis. ,, In Western populations, the reported prevalence is 0.02%-0.05%, , with onset generally occurring during adolescence. ,, Yet, from the Indian subcontinent, there is only one published case report of narcolepsy.  It is possible that the prevalence in India is lower than that in the Western world; it is also possible, that a large number of patients go undiagnosed due to lack of awareness among patients and physicians. The aim of the present study is to analyze clinical and polysomnographic characteristics of consecutive patients with narcolepsy presenting to the Sleep Disorders Clinic of All India Institute of Medical Sciences, New Delhi, India.
| ╗ Materials and Methods|| |
This study is a retrospective analysis of all consecutive patients seen over a 7-year period (September 2003 to August 2010) fulfilling the International Classification of Sleep Disorders - 2 (ICSD-2) diagnostic criteria for narcolepsy.  Patients with other primary sleep disorders such as sleep apnea; co-existing neurological disorders, e.g., encephalitis, stroke, multiple sclerosis, and neuromuscular disorders; history of substance abuse; and those in whom polysomnography and Multiple Sleep Latency Test (MSLT) findings are not sufficient for diagnosis were excluded. Clinical features including socio-demographic aspects of the patients are listed in [Table 1]a and b. Although sleepiness was evaluated using questions of the Epworth Sleepiness Scale, , we tried to classify patients into three categories-mild, moderate, and severe,  and have not analyzed the scores, as most patients did not drive and one of the questions in the scale is related to driving.
Polysomnography and MSLT
Overnight Polysomnography (PSG) followed by a four- or five-nap MSLT was conducted for all patients. These tests were carried out on a video-PSG system (Care fusion, Nicolet 1) using 6-channel Electroencephalography (EEG), Electrooculography (EOG), Submentalis Muscle Electromyogram (EMG), thermistor and nasal pressure transducers to record air flow, chest and abdomen piezoelectric belts to record effort, oxyhemoglobin saturation by pulse oximetry, and Electrocardiogram (ECG). Leg movements were recorded by placement of electrodes over the right tibialis anterior muscle.
Sleep staging, respiratory events, and leg movements were re-scored by either of the first two authors according to the American Academy of Sleep Medicine (AASM) 2007 guidelines.  MSLT was recorded according to the AASM task force recommendations. , Naps were scheduled at two-hour intervals starting 1.5 hour after awakening. Four naps were conducted in all patients, and a fifth nap was added if REM was detected in the last nap. If no sleep occurred in 20 minute, the nap trial was ended and sleep latency recorded as 20 minute. If sleep occurred within 20 minute, the onset was defined as the time from lights out to the first epoch of sleep (including stage one). The test was continued for at least 15 minute after sleep onset to detect Sleep Onset REM Periods (SOREMPs).
All clinical, polysomnographic, and mean sleep latency test data were entered on Microsoft® EXCEL spreadsheets and descriptive statistics used for analysis of data on Microsoft® EXCEL 2007.
| ╗ Results|| |
Of the 1024 patients seen at the Sleep Disorders Clinic during the study period, 712 patients were diagnosed to be suffering from primary sleep disorders. Of them, 24 (2.8%) patients diagnosed with narcolepsy were identified and 20 fulfilled the inclusion criteria for narcolepsy. Three of the 24 patients were excluded because they had severe obstructive sleep apnea; one had epilepsy and was on multiple antiepileptic drugs. Only eight patients (7 male and 1 female) had narcolepsy with cataplexy and 12 (11 male and 1 female) had narcolepsy without cataplexy.
Mean age at presentation was 29±12 years, and mean age of onset of symptoms was 25±12 year. Male predominance was observed with a male: female ratio of 18:2. The mean duration of symptoms was 4.75 ± 6.25 years (range: 1-23 year). Among the cardinal symptoms (eg, EDS, cataplexy, hypnagogic hallucinations, sleep paralysis) of narcolepsy, four patients presented with all, eight patients with three, and eight patients with two symptoms [Table 1]a. History of sleep attacks and EDS was obtained in all patients, while 14 patients reported a history of sleep paralysis. History suggestive of cataplexy was found in eight patients. Mean Body Mass Index (BMI) of patients was 26±4.
Mean total sleep time was 7.6 hours and all reported feeling refreshed in the morning. Six patients had frequent nocturnal awakenings; all had a history of 2-7 naps during day-time with the mean duration of naps being 5-20 minutes. Only one patient had long nap duration of one to two hours. Eight patients had cataplexy. In patient# 3, cataplexy was misdiagnosed as epilepsy for 20 years before the diagnosis of narcolepsy was established. Hallucinations at sleep onset (hypnogogic) were reported by eight patients and one of them had both hypnogogic and hypnopompic hallucinations. Patient number 2 had supernatural premonitions during dreams, which he claimed to have often come true later. Automatic behavior was present in one patient. One patient suffering from narcolepsy with cataplexy had co-morbid restless legs syndrome and another without cataplexy had migraine without aura. Three patients gave history of automobile accidents due to sleep attacks.
PSG and MSLT findings
On PSG, all patients demonstrated excessively fragmented sleep with average sleep duration of 7.02 ± 1.43 hours and mean sleep efficiency of 79.4 ± 12.40%. Average REM sleep percentage was high, i.e., 36.74 ± 3.5%. No patients demonstrated any respiratory disturbance [mean AHI = 0.4 ± 1.1)] [Table 2]. The mean arousal index in the narcolepsy with cataplexy group was observed to be 29.3 and the same in the narcolepsy without cataplexy group was 13.45, reflecting a highly fragmented nocturnal sleep in the former. On MSLT, all patients showed short sleep latencies with an average of 1.30 ± 0.38 minute and two or more SOREMPs.
|Table 2: Overnight polysomnography and MSLT findings in patients diagnosed with narcolepsy (n = 20)|
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| ╗ Discussion|| |
This is the first large series of narcolepsy reported from India, and prior to this, there has been only one case report published.  In our study, the proportion of patients with narcolepsy among all patients with primary sleep disorders was 2.8%, which may appear similar to that in previous reports, but given the specialized tertiary referral nature of our clinic, the number is small. No epidemiological data are yet available from this part of the world; hence, it will be difficult to comment whether narcolepsy is less common in India. However, a study published from Singapore has highlighted a similar issue, reporting 28 cases of narcolepsy seen over a period of four years by a single physician.  The authors have discussed the issue of fewer cases being diagnosed, which might go under-recognized in their population. A similar problem might exist within the North Indian population.
The mean age of onset of symptoms in our series was 25 years, which is slightly younger than the age of onset previously reported. In the study by Bassetti et al.,  in the US, the mean age of patients was 46 years for patients with narcolepsy with cataplexy and 34 years for monosymptomatic narcolepsy, while other studies from Netherlands and Japan reported a mean age of 34 and 29, respectively. , In our series, there was male gender predominance (18:2) as compared to the gender distribution in other published case series. ,, In population-based studies, narcolepsy has been found to be 1.6 times more common in the male population.  In the series reported from Singapore, the male: female ratio was 5.5. This wide variation in different studies could be attributable to the small number of cases or even underestimation of problems experienced by female patients. Automatic behavior was reported by only one of our patients, while this has been reported commonly in the western population (30%-57%) , Since the present study was a retrospective review, it is possible that unless patients came up with a history of bizarre automatic behavior on their own, this history would have been missed.
On polysomnography, mean REM sleep percentage observed was 37, which was significantly higher than previously reported (17.5%). Similarly, mean slow wave sleep percentage observed was 4, which is significantly less than in previous reports.  However, sleep fragmentation reported in the form of Wake After Sleep Onset (WASO mean: 31.33) and arousals (AI = 18.73); as well as the short sleep latencies on MSLT, (mean 1.30 and mean REM latency2.58); are observations similar to those in previous studies.  We observed a much greater sleep fragmentation in the narcolepsy with cataplexy group than in the narcolepsy without cataplexy group (arousal index of 29 versus 13.4, respectively). This has also been a prominent observation by Aldrich et al., who found significantly more frequent awakenings, low percentage of stage 3 and 4 sleep, and higher stage 1 sleep percentage among patients with narcolepsy with cataplexy. 
In conclusion, narcolepsy with and without cataplexy is not frequently seen in the North Indian clinic population; however, clinical and polysomnographic features are similar to those observed in the Western and other Asian populations. It is unclear whether narcolepsy is not as common or it is frequently under-diagnosed here.
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