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Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Going To High Altitude with a Preexisting Neurological Condition

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"Going High with Preexisting Neurological Conditions" is an article written by Ralf Baumgartner, Adrian Siegel, and my good friend Peter Hackett that appeared in Volume 8, Number 2 (2007) of the journal High Altitude Medicine & Biology, published by the International Society for Mountain Medicine.

A very common question of wilderness medicine physicians is whether a person can engage in certain activities and/or travel in a particular environment, depending on their state of health and medical history. Given the number of persons with preexisting conditions, especially those who are part of a growing senior population, these are very important considerations. Whether a person has diabetes, rheumatoid arthritis, sickle cell anemia, or any other of thousands of conditions, it is important to understand what situations are felt to be safe, and what situations are felt to be risky.

Paraphrasing the abstract and article, here is what I learned from Baumgartner et. al.:

There are potential impacts of high altitude exposure on persons with preexisting neurological conditions who normally reside at low altitude. These conditions include permanent and transient lack of oxygen to (portions of) the brain (e.g., stroke, transient ischemic attack [TIA, or stroke "warning"]), occlusive cerebral artery disease (e.g., atherosclerosis of the cerebral arteries), central venous thrombosis (clotted large veins in the brain), abnormal blood vessels within the skull (e.g., aneurysms), multiple sclerosis, space-occupying lesions within the skull (e.g., benign and malignant tumors), dementia, movement disorders, migraine and other headaches, and epilepsy (seizures).

A very important point made early in the article is that much of what is stated is that the recommendations are made mostly from review of case reports (clinical anecdotes), rather than from "controlled" clinical trials, in which there are large, statistically significant numbers of patients who have been observed and studied.

Preexisting neurological conditions are stable or unstable. If they are unstable, they are worsening or improving. Patients with unstable conditions should not travel to high altitude, because resultant low blood oxygen levels may impair or prevent recovery from the condition.

For starters, here is a listing of absolute and relative contraindications for ascent to high altitude:

Absolute contraindications for active (e.g., trekking or climbing) or passive (e.g., motorized vehicle transport) ascent:

1. "Unstable" (progressive, recovering, or fluctuating) condition
2. High risk for a repeat stroke
3. TIA within the past 90 days

Absolute contraindication for active ascent:

1. Residual deficit, either central (e.g., from a stroke), or peripheral (e.g., from multiple sclerosis or severe diabetic neuropathy); these persons may consider passive ascent.

Relative contraindications for active or passive ascent:

1. Severe narrowing or occlusion of a cerebral artery
2. Space-occupying lesion (e.g., brain tumor)
3. Poorly controlled seizure disorder
4. Cerebral aneurysm (dilated blood vessel that might leak or burst)

Here are a few more recommendations from the article:

Stroke and TIA

There are some data from the military to suggest that long-term residence at altitude might increase risk for stroke, but there is no evidence yet to suggest a risk to a short-term traveler. There are factors pro and con, and some thought that inactivity, dehydration, cold, and increased red blood cell count (in response to low oxygen at altitude) may contribute to an increased risk for stroke, but no statistics to support the thesis. Fairly well accepted is the notion that persons who have suffered a stroke are at increased risk for suffering a second stroke. Any persons who has suffered a stroke should consult with his or her physician to determine whether or not a high altitude sojourn should be allowed, and if so, if anti-platelet (anti-blood clotting) therapy with an agent such as aspirin, should be initiated. Persons who have suffered a TIA have a 25% risk of suffering a stroke, another TIA, heart disease, or a major cardiovascular/cerebrovascular incident with the next 90 days. This suggests that they not travel to high altitude during this time period.

Occlusive Cerebral Artery Disease (narrowed or otherwise occluded cerebral artery)

Severe occlusive cerebral artery disease is considered to be a worrisome situation, since an increase in cerebral blood flow is an important adjustment to the diminished oxygen available at high altitude. It is possible that a person would be at increased rish for a situation of low oxygen delivered to the brain and thus a propensity for altitude illness.

Hemorrhage Within the Skull and Blood Vessel Malformations

There is no good study to offer data about the risk of bleeding into or around the brain at high altitude. While high altitude-related blood pressure changes might increase the pressure within blood vessels and therefore the risk of aneurysmal rupture, there are not data. High altitude increases the fragility of very small blood vessels, which theoretically could increase the risk for bleeding.

Multiple Sclerosis

There is no evidence that high altitude in and of itself causes problems for persons with multiple sclerosis.

Intracranial (within the skull) Space-Occupying Lesions

If such a lesion is known to be cancer and is causing neurological symptoms, the person should not travel to high altitude. If the lesion is not cancer (e.g., it is "benign"), caution is warranted, because it is not entirely known which lesions are prone to expansion and thereby inciting neurological symptoms.

Dementia

Persons with dementia be watched very closely for increase in impairment.

Pre-existing Migraine and Other Headaches

The presence of pre-existing headaches is not a contraindication for a trip to high altitude. Clinicians working at high altitude have noted that altitude can be a trigger for migraine headache.

Seizures (Epilepsy)

Rapid ascent to high altitude may predispose to increased frequency of seizures. Gradual ascent may not pose the same risk. To date, there is not evidence that there is an increase in frequency or severity of seizures when anti-seizure medications are contiued at high altitude.

photo by Mathias Schar

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Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.

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