Narcolepsy Workup

  • Author: Ali M Bozorg, MD; Chief Editor: Selim R Benbadis, MD   more...
 
Updated: Feb 19, 2010
 

Laboratory Studies

  • HLA typing
    • DQB1*0602
    • DQA1*0602
    • In general, HLA typing is clinically useful to exclude narcolepsy. It is less valuable to confirm the diagnosis, since HLA-DR2 and DQw1 are present in 20-30% of the general population.
  • CSF hypocretin levels below 110 pg/mL is indicative of narcolepsy. On the other hand, high CSF hypocretin levels do not exclude the diagnosis of narcolepsy.
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Imaging Studies

  • In most cases, imaging studies are unrevealing.
  • A few small studies have implicated MRI changes of the pons within the reticular activating system. Structural abnormalities of the brain stem and diencephalon may present as idiopathic narcolepsy.
  • On MRI of the brain, patients with secondary narcolepsy may show various abnormalities that correspond to the underlying cause.
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Other Tests

  • An overnight polysomnogram followed by a multiple sleep latency test (MSLT) is essential in the workup. All central nervous stimulants and sedative-hypnotics should be discontinued 2 weeks prior to the PSG and MSLT.
    • These tests allow exclusion of other causes of EDS, especially sleep apnea.
    • They provide information about daytime sleepiness by measuring sleep latency and sleep-onset REM periods (SOREMPs).
    • The MSLT involves 5 opportunities to nap at 2-hour intervals over the day.
    • More than 2 SOREMPs and a mean sleep latency of less than 8 minutes strongly suggest narcolepsy. These findings are not completely specific and also can be seen in patients with severe sleep deprivation or severe sleep apnea.
    • For these reasons, a polysomnogram of the previous night is necessary to interpret the MSLT.
    • The overnight polysomnogram findings typically are normal in narcolepsy, although they may show sleep fragmentation
    • MSLT cannot be used alone to confirm or rule out narcolepsy.
  • Diagnosing narcolepsy in children presents numerous difficulties.
    • One study found that 85% of children with narcolepsy also suffered from sleep-disordered breathing.
    • Serial MSLTs may be required, and usually multiple confounding factors are involved (eg, increased alertness in the novel environment of the sleep laboratory).
    • Normative MSLT values for children have not been established.
    • HLA typing may provide collateral data but is more useful in excluding the diagnosis.
    • Measurement of CSF hypocretin levels may aide in the diagnosis.
    • Imaging studies such as MRI are useful to exclude rare causes of symptomatic narcolepsy.
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Contributor Information and Disclosures
Author

Ali M Bozorg, MD  Assistant Professor, Comprehensive Epilepsy Program, Department of Neurology, University of South Florida

Ali M Bozorg, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, and American Epilepsy Society

Disclosure: Nothing to disclose.

Coauthor(s)

Selim R Benbadis, MD  Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association

Disclosure: UCB Pharma Honoraria Speaking, consulting; Lundbeck Honoraria Speaking, consulting; Cyberonics Honoraria Speaking, consulting; Glaxo Smith Kline Honoraria Speaking, consulting; Ortho McNeil Honoraria Speaking, consulting; Pfizer Honoraria Speaking, consulting; Sleepmed/DigiTrace Speaking, consulting

Specialty Editor Board

Carmel Armon, MD, MSc, MHS  Professor of Neurology, Tufts University School of Medicine; Chief, Division of Neurology, Baystate Medical Center

Carmel Armon, MD, MSc, MHS is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Association of Neuromuscular and Electrodiagnostic Medicine, American Clinical Neurophysiology Society, American College of Physicians, American Epilepsy Society, American Medical Association, American Neurological Association, American Stroke Association, Massachusetts Medical Society, Movement Disorders Society, and Sigma Xi

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Senior Pharmacy Editor, eMedicine

Disclosure: eMedicine Salary Employment

Jose E Cavazos, MD, PhD, FAAN  Associate Professor with Tenure, Departments of Neurology, Pharmacology, and Physiology, University of Texas Health Science Center at San Antonio; Co-Director, South Texas Comprehensive Epilepsy Center; Director of the Epilepsy Center, Audie L Murphy Veterans Affairs Medical Center

Jose E Cavazos, MD, PhD, FAAN is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, American Neurological Association, and Society for Neuroscience

Disclosure: Nothing to disclose.

Paul E Barkhaus, MD  Professor, Department of Neurology, Medical College of Wisconsin; Director of Neuromuscular Diseases, Milwaukee Veterans Administration Medical Center

Paul E Barkhaus, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Neurological Association

Disclosure: Nothing to disclose.

Chief Editor

Selim R Benbadis, MD  Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association

Disclosure: UCB Pharma Honoraria Speaking, consulting; Lundbeck Honoraria Speaking, consulting; Cyberonics Honoraria Speaking, consulting; Glaxo Smith Kline Honoraria Speaking, consulting; Ortho McNeil Honoraria Speaking, consulting; Pfizer Honoraria Speaking, consulting; Sleepmed/DigiTrace Speaking, consulting

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