Altitude Illness - Cerebral Syndromes Clinical Presentation

  • Author: N Stuart Harris, MD, MFA, FACEP; Chief Editor: Rick Kulkarni, MD   more...
 
Updated: Apr 30, 2010
 

History

AMS is a syndrome of nonspecific symptoms with a broad spectrum of severity. AMS occurs in nonacclimatized persons in the first 48 h after ascent to altitudes above 2500 m, especially after rapid ascent (1 d or less). Symptoms usually begin a few hours after arrival at the new altitude but may arise as much as a day later, often after the first night's sleep. Headache is the principal symptom, typically frontal and throbbing. Gastrointestinal symptoms (anorexia, nausea, or vomiting), and constitutional symptoms (weakness, lightheadedness, or lassitude) are common. AMS is similar to an alcohol hangover, or to a nonspecific viral infection, but without fever or myalgias.

Fluid retention is characteristic of AMS, and persons with AMS often report reduced urination, in contrast to the spontaneous diuresis observed with successful acclimatization. As AMS progresses, the headache worsens, and vomiting, oliguria, and increased lassitude develop. Ataxia and altered level of consciousness herald the onset of clinical HACE.

Using the Lake Louise consensus criteria, the diagnosis of AMS requires headache plus at least one of the following symptoms: gastrointestinal (anorexia, nausea, vomiting), constitutional (lightheadedness, dizziness, weakness, fatigue), or insomnia. Most conditions similar to AMS can be excluded by history and physical examination. Onset of symptoms more than 3 days after ascent, lack of headache, or failure to improve with descent, oxygen, or dexamethasone suggests another diagnosis. Dehydration is commonly confused with AMS, as it can cause headache, weakness, nausea, and decreased urine output.

The most common history in HACE is a person ascending further despite symptoms of AMS; however, rarely, it may develop in the absence of AMS after a very rapid ascent or at extreme altitude in an apparently acclimatized person. Also, HACE commonly occurs in conjunction with HAPE.

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Physical

  • Acute mountain sickness
    • Patients may appear ill but otherwise have no characteristic physical findings.
    • Neurologic examination (especially mental status and gait) is normal.
    • Heart rate and blood pressure are variable and nondiagnostic.
    • Pulmonary crackles may be present in some patients, but oxygen saturation will be normal or, at most, slightly lower than acclimatized persons at the same elevation.
    • Fever is absent.
    • Funduscopic examination may reveal retinal hemorrhages, but these are not specific to AMS.[2]
    • Peripheral and facial edema may be present, particularly in women.
  • High-altitude cerebral edema
    • In a patient with symptoms of AMS who develops gait ataxia (ie, unable to walk heel-to-toe in a straight line) or mental status changes, HACE is the diagnosis until proven otherwise. Immediate treatment and descent is indicated.
    • Regardless of AMS symptoms, a combination of ataxia and mental status changes suggests HACE.
    • Usually, the neurologic examination findings are otherwise normal.
    • In rare cases, focal neurologic signs (eg, cranial nerve III palsy, cranial nerve VI palsy) appear in end-stage HACE, although they are more suggestive of other causes of focal deficits at altitude (eg, stroke, transient ischemic attack [TIA], migraine, brain neoplasm).
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Causes

  • Rapid ascent to altitudes greater than 2500 m can cause AMS.
  • The risk of HACE or AMS increases with altitude.
  • Special attention should be paid to the elevation at which the person sleeps. Daytime climbs to higher elevations, with return to a lower sleeping altitude are preferred.
  • Continued ascent despite symptoms of AMS is a major risk factor for developing HACE. At altitudes over 5000 m, ascents of as little as 200 m for individuals with moderate AMS have precipitated HACE.
  • HACE frequently is seen secondary to HAPE, presumably because of rapidly worsening hypoxia, which is equivalent to continued ascent.
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Contributor Information and Disclosures
Author

N Stuart Harris, MD, MFA, FACEP  Chief, Division of Wilderness Medicine, Massachusetts General Hospital (MGH) Fellowship Director, MGH Wilderness Medicine Fellowship. Attending Physician, MGH Assistant Professor in Surgery, Harvard Medical School

N Stuart Harris, MD, MFA, FACEP is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, International Society for Mountain Medicine, and Massachusetts Medical Society

Disclosure: Nothing to disclose.

Coauthor(s)

Sara W Nelson, MD  Staff Physician, Harvard Affiliated Emergency Medicine Residency, Brigham and Women's Hospital and Massachusetts General Hospital

Sara W Nelson, MD is a member of the following medical societies: American College of Emergency Physicians, Emergency Medicine Residents Association, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Specialty Editor Board

Dan Danzl, MD  Chair, Professor, Department of Emergency Medicine, University of Louisville Hospital

Dan Danzl, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Kentucky Medical Association, Society for Academic Emergency Medicine, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Eddy S Lang, MDCM, CCFP(EM), CSPQ  Associate Professor, Senior Researcher, Division of Emergency Medicine, Department of Family Medicine, University of Calgary Faculty of Medicine; Assistant Professor, Department of Family Medicine, McGill University Faculty of Medicine, Canada

Eddy S Lang, MDCM, CCFP(EM), CSPQ is a member of the following medical societies: American College of Emergency Physicians, Canadian Association of Emergency Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

John D Halamka, MD, MS  Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center

John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Rick Kulkarni, MD  Attending Physician, Department of Emergency Medicine, Cambridge Health Alliance, Division of Emergency Medicine, Harvard Medical School

Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: WebMD Salary Employment

Additional Contributors

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Thomas E Dietz, MD, to the development and writing of this article.

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High-altitude cerebral edema (HACE). Image courtesy of Dr Peter Hackett.
A very ataxic man with high-altitude cerebral edema (HACE) at 4250 m being assisted toward the Gamow bag.
Ultrasonography - Optic nerve sheath diameter measurement. Top of field is cornea, bottom of field reveals retina, then optic nerve in lowest field. Images courtesy of Dr Peter Fagenholz et al.
Horse evacuation of nonambulatory altitude illness. Patient in the Khumbu, Nepal. Image courtesy of Dr Peter Fagenholz.
 
 
 
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