Going High with Preexisting Neurological Conditions

Fly and treat: Endovascular treatment of ruptured aneurysms at an insular tertiary center

(Objectives) Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening condition associated with poor outcomes. Early intervention is critical, particularly in low-volume hospitals, which are advised to transfer aSAH patients to high-volume centers. This study examines a novel protocol implemented in 2016 at Região Autónoma da Madeira, a Portuguese island. It involves the mobilization of experienced neurointerventionalists from high-volume hospitals to provide aSAH treatment. (Methods) We conducted a retrospective analysis on 30 aSAH patients who underwent endovascular treatment at the island center between November 2016 and April 2022. Additionally, we included a comparison group of 74 aSAH patients, treated with the endovascular approach at Hospital de Braga (high volume center at Portugal mainland). (Results) There was no statistical difference in patients' clinical severity between both hospitals (median WFNS score of 1). Although 90 % of patients in the novel protocol group received treatment within 3 days, we observed a significant delay compared to Hospital de Braga. Rates of aneurysm occlusion and intra-procedure complications between the two groups were similar. At the 3-months follow-up, there were no statistically significant differences between groups regarding patients that achieved a modified Rankin score of 2 or less. However, the island center exhibited a significantly higher mortality rate. (Conclusions) Overall, our results suggest that making the neurointerventionalist fly to an insular center is feasible and allows most patients to be treated within the first 72 h, as recommended. We highlight some potential recommendations for implementing this model and discuss possible causes that might justify the high mortality rate.

Stroke at Moderate and High Altitude

Syed, Maryam J., Ismail A. Khatri, Wasim Alamgir, and Mohammad Wasay. Stroke at moderate and high altitude. High Alt Med Biol. 23:1-7, 2022. Background: Stroke at high altitude is an understudied area in stroke research. With improvements in road infrastructure, access to high-altitude areas for recreation and living purposes has risen. Subsequently, it has been anticipated that due to normal physiological changes to high altitude the incidence of stroke is also likely to increase in these regions. Methods: We searched PubMed for available literature about stroke at high altitude. Cross-referencing was done from available articles and through other scientific search engines. Relevant case series and case reports were included in this review of the topic. Results: Only one review article, eight case series (including review of literature), and seven case reports were identified that could be included in this review. Most of the available data come from moderate and high altitude. Conclusions: There is limited available literature about stroke at high and extreme altitudes. Stroke at high altitude is likely to become an important subset of stroke population. Currently, there is inadequate knowledge about the incidence and prevalence, mechanisms, and stroke outcomes. Cerebral venous thrombosis is more common than arterial stroke. Stroke is probably secondary to conventional risk factors, polycythemia, and other coagulopathies. A case-control study may identify the at-risk population for stroke at moderate and high altitudes.

Recommendations for traveling to altitude with neurological disorders

BACKGROUND

Several neurological conditions might worsen with the exposure to high altitude (HA). The aim of this review was to summarize the available knowledge on the neurological HA illnesses and the risk for people with neurological disorders to attend HA locations.

METHODS

A search of literature was conducted for several neurological disorders in PubMed and other databases since 1970. The neurological conditions searched were migraine, different cerebrovascular disease, intracranial space occupying mass, multiple sclerosis, peripheral neuropathies, neuromuscular disorders, epileptic seizures, delirium, dementia, and Parkinson's disease (PD).

RESULTS

Attempts were made to classify the risk posed by each condition and to provide recommendations regarding medical evaluation and advice for or against traveling to altitude. Individual cases should be advised after careful examination and risk evaluation performed either in an outpatient mountain medicine service or by a physician with knowledge of HA risks. Preliminary diagnostic methods and anticipation of neurological complications are needed.

CONCLUSIONS

Our recommendations suggest absolute contraindications to HA exposure for the following neurological conditions: (1) Unstable conditions-such as recent strokes, (2) Diabetic neuropathy, (3) Transient ischemic attack in the last month, (4) Brain tumors, and 5. Neuromuscular disorders with a decrease of forced vital capacity >60%. We consider the following relative contraindications where decision has to be made case by case: (1) Epilepsy based on recurrence of seizure and stabilization with the therapy, (2) PD (± obstructive sleep apnea syndrome-OSAS), (3) Mild Cognitive Impairment (± OSAS), and (4) Patent foramen ovale and migraine have to be considered risk factors for acute mountain sickness.

Multiple Sclerosis Exacerbation Associated With High-Altitude Climbing Exposure

The spectrum of the neurological effects of high-altitude exposure can range from high-altitude headache and acute mountain sickness, to the more severe end of the spectrum with high-altitude cerebral edema. In general, patients with known unstable preexisting neurological conditions and those patients with residual neurological deficits from a preexisting neurological condition are discouraged from climbing to high altitudes because of the risk of exacerbation or worsening of symptoms. Although multiple sclerosis exacerbations can be triggered by environmental factors, high-altitude exposure has not been reported as a potential trigger. We are reporting the case of a multiple sclerosis exacerbation presenting in an active duty U.S. Air Force serviceman upon ascending and descending Mt. Fuji within the same day.

Pupil-Involving Third Cranial Nerve Paresis at High Altitude

Blomquist, Preston H. Pupil-involving third cranial nerve paresis at high altitude. High Alt Med Biol. 19:286-287, 2018.-Although sixth cranial nerve palsies are a well-recognized entity at high altitude, other cranial nerve palsies due to altitude are much more uncommon. A case of a 55-year-old woman is presented who flew from Dallas, Texas (elevation 176 m) to Breckenridge, Colorado, where she hiked up to 3600 m above sea level. She developed a pupil-involving right third cranial nerve paresis that resolved over the next 3 months. In the absence of significant abnormalities on neuroimaging and serum laboratories, the etiology is presumed to be due to high altitude.

Risk of Complications After Intracranial Procedures at High Altitude

BACKGROUND

Postoperative hemorrhagic or ischemic complications cause significant morbidity and mortality after craniotomy. High altitude creates a state of relative hypoxia, resulting in increased cerebral blood flow for compensation. This potentially creates an increased risk at high altitude of having increased morbidity from hemorrhagic or ischemic events, and some neurosurgeons forbid air travel to patients immediately after craniotomy for this reason. We hypothesized there was no difference in postoperative complications based on altitude.

METHODS

We retrospectively reviewed all craniotomies performed at a high-altitude medical center to assess whether originating, surgical, or destination altitude affected postoperative outcomes.

RESULTS

Between 1 July 2014 and 30 June 2016, 1807 craniotomy procedures were performed. There were 53 (2.9%) postoperative hemorrhagic or ischemic complications during the first 30 days after surgery, 44 (2.4%) hemorrhagic events, and 9 (0.5%) ischemic events. From the 36 patients who had postoperative complications at the hospital, 10 of them lived in an altitude below the hospital, 26 lived in an altitude above the hospital, and 1 has no record of address. Excluding the patients who had complications at the hospital, we had 8 patients discharged to a ZIP code below the altitude of the hospital (7 hemorrhagic events and 1 ischemic) and 9 were discharged to a location at an altitude above that of the hospital (8 hemorrhagic events and 1 ischemic). There were no statistically significant differences between cohorts.

CONCLUSIONS

Altitude does not appear to have a significant impact on postoperative rates of hemorrhagic or ischemic complications.

General Medical Considerations for the Wilderness Adventurer: Medical Conditions That May Worsen With or Present Challenges to Coping With Wilderness Exposure

Participation in wilderness and adventure sports is on the rise, and as such, practitioners will see more athletes seeking clearance to participate in these events. The purpose of this article is to describe specific medical conditions that may worsen or present challenges to the athlete in a wilderness environment.

A prospective epidemiological study of acute mountain sickness in Nepalese pilgrims ascending to high altitude (4380 m)

Background

Each year, thousands of pilgrims travel to the Janai Purnima festival in Gosainkunda, Nepal (4380 m), ascending rapidly and often without the aid of pharmaceutical prophylaxis.

Methods

During the 2012 Janai Purnima festival, 538 subjects were recruited in Dhunche (1950 m) before ascending to Gosainkunda. Through interviews, subjects provided demographic information, ratings of AMS symptoms (Lake Louise Scores; LLS), ascent profiles, and strategies for prophylaxis.

Results

In the 491 subjects (91% follow-up rate) who were assessed upon arrival at Gosainkunda, the incidence of AMS was 34.0%. AMS was more common in females than in males (RR = 1.57; 95% CI = 1.23, 2.00), and the AMS incidence was greater in subjects >35 years compared to subjects ≤35 years (RR = 1.63; 95% CI = 1.36, 1.95). There was a greater incidence of AMS in subjects who chose to use garlic as a prophylactic compared to those who did not (RR = 1.69; 95% CI = 1.26, 2.28). Although the LLS of brothers had a moderate correlation (intraclass correlation = 0.40, p = 0.023), sibling AMS status was a weak predictor of AMS.

Conclusions

The incidence of AMS upon reaching 4380 m was 34% in a large population of Nepalese pilgrims. Sex, age, and ascent rate were significant factors in the development of AMS, and traditional Nepalese remedies were ineffective in the prevention of AMS.

Can migraine prophylaxis prevent acute mountain sickness at high altitude?

Acute mountain sickness (AMS) develops in people trekking at high altitude. The underlying mechanism is vasodilation due to low pressure of oxygen. However, individual susceptibility for AMS is unknown, thus, one cannot predict when or to whom it happens. Because AMS usually begins with headache, and because migraineurs are more vulnerable to AMS, we studied by the literatures review on the mechanism and clinical features in common, and assessed the treatment modalities for both disorders. This led to us the following hypothesis that, migraine prophylaxis may prevent or delay the onset of AMS at high altitude. Clinical features of AMS include nausea or vomiting when it progresses. Hypobaric hypoxia, dehydration or increased physical exertion trigger or aggravate both disorders. In migraine, cerebral vasodilation can happen following alteration of neuronal activity, whereas the AMS is associated with peripheral vessel dilation. Medications that dilate the vessels worsen both conditions. Acute treatment strategies for migraine overlap with to those of AMS, including drugs such as vasoconstrictors, or other analgesics. To prevent AMS, adaptation to high altitude or pharmacological prophylaxis, i.e., acetazolamide has been recommended. This carbonic anhydrase inhibitor lowers serum potassium level, and thus stabilizes membrane excitability. Acetazolamide is also effective on specific forms of migraine. Taken together, these evidences implicate that migraine prophylaxis may prevent or delay the onset of AMS by elevating the threshold for high altitude.

Intracranial hemorrhage during aeromedical transport and correlation with high altitude adaptations in the brain

Aeromedical transport is challenging not only because of limitations of equipment, unfamiliar surroundings, and challenging environmental conditions, but also due to difficulty in developing methodologies for research and data collection. To our knowledge, neurological changes at the oxygen tensions of a pressurized cabin have not been systematically studied. Here we report a case of intracranial hemorrhage during aeromedical transport and review the body's cardiovascular and respiratory adaptation to decreased ambient oxygen tension. Previous experience with high altitude cerebral edema serves as guidance for mitigating the effects of vasogenic edema in patients at risk of neurological events who travel by air. Review of this case and relevant altitude-related physiological changes may be grounds for more conservative recommendations on aeromedical transport after an acute neurological event.

Occupational health of miners at altitude: adverse health effects, toxic exposures, pre-placement screening, acclimatization, and worker surveillance

CONTEXT

Mining operations conducted at high altitudes provide health challenges for workers as well as for medical personnel.

OBJECTIVE

To review the literature regarding adverse health effects and toxic exposures that may be associated with mining operations conducted at altitude and to discuss pre-placement screening, acclimatization issues, and on-site surveillance strategies.

METHODS

We used the Ovid ( http://ovidsp.tx.ovid.com ) search engine to conduct a MEDLINE search for "coal mining" or "mining" and "altitude sickness" or "altitude" and a second MEDLINE search for "occupational diseases" and "altitude sickness" or "altitude." The search identified 97 articles of which 76 were relevant. In addition, the references of these 76 articles were manually reviewed for relevant articles. CARDIOVASCULAR EFFECTS: High altitude is associated with increased sympathetic tone that may result in elevated blood pressure, particularly in workers with pre-existing hypertension. Workers with a history of coronary artery disease experience ischemia at lower work rates at high altitude, while those with a history of congestive heart failure have decreased exercise tolerance at high altitude as compared to healthy controls and are at higher risk of suffering an exacerbation of their heart failure. PULMONARY EFFECTS: High altitude is associated with various adverse pulmonary effects, including high-altitude pulmonary edema, pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness. Mining at altitude has been reported to accelerate silicosis and other pneumoconioses. Miners with pre-existing pneumoconioses may experience an exacerbation of their condition at altitude. Persons traveling to high altitude have a higher incidence of Cheyne-Stokes respiration while sleeping than do persons native to high altitude. Obesity increases the risk of pulmonary hypertension, acute mountain sickness, and sleep-disordered breathing. NEUROLOGICAL EFFECTS: The most common adverse neurological effect of high altitude is acute mountain sickness, while the most severe adverse neurological effect is high-altitude cerebral edema. Poor sleep quality and sleep-disordered breathing may contribute to daytime sleepiness and impaired cognitive performance that could potentially result in workplace injuries, particularly in miners who are already at increased risk of suffering unintentional workplace injuries. OPHTHALMOLOGICAL EFFECTS: Adverse ophthalmological effects include increased exposure to ultraviolet light and xerophthalmia, which may be further exacerbated by occupational dust exposure. RENAL EFFECTS: High altitude is associated with a protective effect in patients with renal disease, although it is unknown how this would affect miners with a history of chronic renal disease from exposure to silica and other renal toxicants. HEMATOLOGICAL EFFECTS: Advanced age increases the risk of erythrocytosis and chronic mountain sickness in miners. Thrombotic and thromboembolic events are also more common at high altitude. MUSCULOSKELETAL EFFECTS: Miners are at increased risk for low back pain due to occupational factors, and the easy fatigue at altitude has been reported to further predispose workers to this disorder. TOXIC EXPOSURES: Diesel emissions at altitude contain more carbon monoxide due to increased incomplete combustion of fuel. In addition, a given partial pressure of carbon monoxide at altitude will result in a larger percentage of carboxyhemoglobin at altitude. Miners with a diagnosis of chronic obstructive pulmonary disease may be at higher risk for morbidity from exposure to diesel exhaust at altitude.

CONCLUSIONS

Both mining and work at altitude have independently been associated with a number of adverse health effects, although the combined effect of mining activities and high altitude has not been adequately studied. Careful selection of workers, appropriate acclimatization, and limited on-site surveillance can help control most health risks. Further research is necessary to more completely understand the risks of mining at altitude and delineate what characteristics of potential employees put them at risk for altitude-related morbidity or mortality.

The cerebral effects of ascent to high altitudes

Cellular hypoxia is the common final pathway of brain injury that occurs not just after asphyxia, but also when cerebral perfusion is impaired directly (eg, embolic stroke) or indirectly (eg, raised intracranial pressure after head injury). We Review recent advances in the understanding of neurological clinical syndromes that occur on exposure to high altitudes, including high altitude headache (HAH), acute mountain sickness (AMS), and high altitude cerebral oedema (HACE), and the genetics, molecular mechanisms, and physiology that underpin them. We also present the vasogenic and cytotoxic bases for HACE and explore venous hypertension as a possible contributory factor. Although the factors that control susceptibility to HACE are poorly understood, the effects of exposure to altitude (and thus hypobaric hypoxia) might provide a reproducible model for the study of cerebral cellular hypoxia in healthy individuals. The effects of hypobaric hypoxia might also provide new insights into the understanding of hypoxia in the clinical setting.

Medication and dosage considerations in the prophylaxis and treatment of high-altitude illness

With increasing numbers of people traveling to high altitude for work or pleasure, there is a reasonable chance that many of these travelers have preexisting medical conditions or are receiving various medications at the time of their sojourn. As with all travelers to high altitude, they are at risk for altitude illnesses such as acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema. While there are clear recommendations for pharmacologic measures to prevent or treat these illnesses, these recommendations are oriented toward healthy individuals and do not take into account the presence of preexisting medical conditions. In this review, we consider how the choice and dose of the medications used in the management of altitude illness-acetazolamide, dexamethasone, nifedipine, tadalafil, sildenafil, and salmeterol-are affected by a patient's underlying medical conditions. We discuss the indications and current dosing recommendations for individuals without underlying disease, and then consider how drug selection or dosing regimens will be affected by the presence of renal insufficiency, hepatic insufficiency, other important medical conditions, and the potential for serious drug interactions. We include comments about interactions with antimalarial medications and antibiotics used in the treatment of traveler's diarrhea, as well as the safety of use during pregnancy. By giving these issues adequate consideration, clinicians can increase the chances that properly evaluated patients with underlying medical conditions will enjoy a safe trip to high altitude.