Because of the broad health benefits of being in nature–or merely to benefit once again from pleasures that they had previously enjoyed — many people recovering from cerebral amyloid angiopathy (CAA) may wish to visit mountains, national parks, or other high altitude (HA) locations. HA locations also include cities like Colorado Springs (1,800 meters), or even countries like Peru (average of 1,500 meters). In any case, simply flying in the pressurized cabin of a commercial flight is equivalent to being on a mountain at 2,500 to 3,000 meters. Therefore, it is useful to consider whether high altitude represents a health threat to anyone recovering from CAA.
While there does not appear to be a great deal of research on this important subject, Marika Falla, MD, PhD, Guido Giardini, MD, and Corrado Angelini, MD, FAAN, have published an important and highly relevant article, “Several neurological conditions might worsen with the exposure to high altitude (HA),” in the Journal of Central Nervous System Disease.
Here is a link and a reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8695750/
J Cent Nerv Syst Dis. 2021; 13: 11795735211053448.
According to the authors, some of the factors to consider before visiting HA locations include the nature of the neurological condition, the altitude, the speed of reaching the altitude, and the length of stay. (Years’ long stays at altitudes over 5,000 meters can be risky even for people without CAA or any other neurological conditions).
WHAT DOES HIGH ALTITUDE MEAN?
For purposes of this article by Falla et al, “altitude is classified as low (500–2000 m), moderate (2000–3000 m), high (3000–5500 m), or extreme (>5500 m).” Since many vacationers or other travelers are likely to be traveling in the so-called “low” altitude areas, they might be most concerned with the “absolute contraindications” mentioned below.
ABSOLUTE CONTRAINDICATIONS
The authors suggest “absolute contraindications to HA exposure for the following neurological conditions: Unstable conditions–such as recent strokes,… Transient ischemic attack in the last month, …”
RELATIVE CONTRAINDICATIONS
Falla et al also consider the “following relative contraindications where decision has to be made case by case: (1) Epilepsy … (2) PD (± obstructive sleep apnea syndrome-OSAS), (3) Mild Cognitive Impairment (± OSAS) [obstructive sleep apnea], and (4) Patent foramen ovale and migraine….”
In order to better explain the physiological bases for their recommendations, the authors have singled out the “special conditions” of hemorrhagic stroke, subaracnoid hemorrhage, and mild cognitive impairment for additional discussion.
SPECIAL CONDITIONS
Hemorrhagic stroke
“…The hemorrhage occurs within the brain parenchyma (i.e., intracerebral hemorrhage) or within the subarachnoid space and ventricular system (also termed subarachnoid hemorrhage). The main cause of intracranial hemorrhage is considered the arterial hypertension that may worsen at HA due to cardiovascular response to HA– but in patients with amyloid angiopathy there is the risk of high recurrence of lobar hemorrhage even at sea level and therefore these patients should not be recommended to ascent to HA. In case of recent acute neurological events patients should not ascend to HA. In case of previous hemorrhages, the situations need to be carefully evaluated considering comorbidities and stable conditions.“
Editor’s question: Since the key concern for patients who have experienced a hemorrhagic stroke seems to be that high altitude might increase systolic and diastolic blood pressure, perhaps patients might want to use a portable (battery operated) blood pressure monitor) to test their blood pressure while at altitude. We plan to experiment with this technique, will report back in a future blog post, and would welcome any comments from medical personnel or anyone else who has experiment with this approach or would like to do so. You can reach us at postmaster@csdr.org
Subarachnoid hemorrhage
“At HA there is an increasing blood flow and augmented capillary permeability related to the brain adaptation to HA. The adjunctive role of the decreased barometric pressure may increase the aneurysm or arteriovenous malformations rupture event.”
“Subarachnoid hemorrhage (SAH) is usually related to an aneurysm rupture due to increased pressure which force the blood into the subarachnoid space. Aneurysm of 10 mm or more of diameter are more susceptible to rupture being the likelihood of rupture those smaller than 10 mm between .05% and .7% per year…. Risk factors includes hypertension, physical activity (e.g., sexual activity), straining at stool or during natural delivery, sometimes even due to coughing or sneezing. The leading symptoms is the headache usually refers by the patients as the “worse ever had” and various degree of altered mental status which make the differentiation with HACE difficult.”
Mild cognitive impairment and dementia
“Mild cognitive impairment (MCI) is a condition in which individuals demonstrate minimal cognitive impairment of instrumental activities of daily living and it is considered to be an intermediate state between normal cognitive aging and early dementia…. ”
“The possible contribution of hypoxia in the progression of the MCI into dementia is not yet established. … In patients with cardiac arrest have been found that hypoxia increase β-amyloid (Aβ) level.… In an animal model has been found that chronic HA exposure induces learning and memory deficits and the reduced expression of several synaptic proteins and astroglial cell markers in different brain areas.
Editor’s question: Since blood pressure is likely to rise with hypoxia–and given the concern that hypoxia might increase β-amyloid (Aβ) levels,, it may be useful to test for blood pressure at HA as an indirect way of testing for adverse effects of hypoxia. This has been suggested above. If you have comments, please let us know at postmaster@csdr.org
“…Recent studies suggest a potential beneficial role of limited exposure to hypoxia. Experimental intermittent hypoxia (IH)-hyperoxia training has demonstrated improvement in cognitive functions and decreased Alzheimer’s disease (AD) biomarker in MCI patients.”
“...Due to the potential deleterious effect exerts by hypoxia on cognitive functions it is not advisable to allow patients with any type of dementia to go to altitude and this could be applied also to MCI patients.” “...Due to the potential deleterious effect exerts by hypoxia on cognitive functions it is not advisable to allow patients with any type of dementia to go to altitude and this could be applied also to MCI patients.”
CONCLUSIVE REMARKS AND RECOMMENDATIONS FOR PATIENTS
“Arterial hypertension is the main cause of hemorrhagic stroke and HA increases blood pressure leading to adverse effects on cerebral aneurisms and arterial venous malformations. Patients with amyloid angiopathy are at risk of lobar hemorrhage, therefore patients with such conditions are advised to avoid altitude. A moderate or severe disability post-stroke measured with the Rankin scale (>2) is a contraindication to visit a wild environment. It is advisable to encourage patients with previous stroke (but this applies to most neurological patients) to avoid trekking alone.
Editor’s note: A Rankin scan greater than 2 would mean requiring some help with daily affairs but still being able to walk with the help of another person.
“Recommendations for HA exposure for neurological patients.”
| Recommendations | Neurological Conditions |
|---|---|
| Absolute contraindications | • Unstable conditions, such as recent strokes |
| • Diabetic neuropathy | |
| • TIA in the last months | |
| • Brain tumors | |
| • Neuromuscular disorders, with a decrease of FVC of >60% | |
| Relative contraindications a | • Epilepsy based on seizure recurrence of and stabilization with the therapy |
| • Parkinson’s disease (±OSAS) | |
| • Mild Cognitive Impairment (±OSAS) | |
| • PFO and migraine have to be considered as a risk factor for AMS |