High altitude headache
Headache is the most common symptom of high altitude sickness
As increasing numbers of people live, work and holiday at high altitude, so awareness of the neurological consequences has become more important. Despite studies examining altitude sickness, the underlying mechanisms of the spectrum of altitude related illnesses are still elusive.
High altitude sickness is a common name for illnesses that can occur at high altitude, usually over 3000 meters above sea level. Another term used is acute mountain sickness. The cause is hypoxia (meaning a deficiency in the amount of oxygen reaching body tissues) but the underlying physiological process is a complex mixture of factors.
The most common symptom is headache, but loss of appetite, nausea and sleep disturbances are also common complaints. High altitude sickness can be prevented by slow ascent and avoiding overexertion. Medication is available that can help reduce symptoms.
Many trekkers or climbers develop two or three symptoms of high altitude illness after rapid ascent (over 300 metres per day) to an altitude above 3000 to 4000 metres.
Defining high altitude headache
The International Headache Society (IHS), an international group of headache specialists, has included a definition of high altitude headache in the second edition of their International Classification of Headache Disorders.
Their definition is:
A. Headache with at least two of the following characteristics and fulfilling criteria C and D
- Frontal or frontotemporal (at the front of the head in the region of the temples)
- Dull or pressing quality
- Mild or moderate intensity
- Aggravated by exertion, movement, straining, coughing, or bending
B. Ascent to altitude above 2500 metres
C. Headache develops within 24 hours after ascent
D. Headache resolves within eight hours of descent.
Headache is the most common neurological symptom and complication, arising from ascent to altitudes greater than 2500 to 3000 metres. Until recently there have been few systematic attempts to define the clinical features of high altitude headache (HAH) and only a small number of trials of therapies, which at times yielded conflicting results. Most descriptions of HAH originated with doctors who had extensive personal experience of it at altitude.
What are the risk factors for developing high altitude headache or acute mountain sickness?
The prevalence of acute mountain sickness has been found to increase with altitude. Heavy perceived exertion, a history of migraine, the absolute altitude reached, little mountaineering experience and inadequate water intake (less than two litres) have been found to be independent risk factors for acute mountain sickness.
A study published in 2003 analysed the incidence, risk factors, and clinical characteristics of HAH in members of an expeditionary unit to the Kanchenjunga base camp in Nepal (5100 metres). Participants were interviewed prior to the trip and while trekking. They recorded headaches experienced at greater than 3000 metres using a structured questionnaire incorporating the diagnosis for HAH and acute mountain sickness. In addition, 19 trekkers from other groups above 3000 metres recorded features of headaches using the same questionnaire. This study demonstrated that 83 per cent reported at least one HAH at a mean altitude of 4723 metres.
Those who developed HAH were significantly younger than those who did not, suggesting that age-related cerebral atrophy (loss of brain cells) might accommodate mild cerebral edema (or swelling). Women and people who have headaches in daily life, were also more likely to report severe headaches at altitude. In this study, 95 per cent of the women reported headaches compared to 82 per cent of the men, and the headaches of the women were reported more frequently and described as of greater severity than those of the men. At normal altitudes, women have a higher rate of migraine and most other headaches than men, raising the possibility that they may be more susceptible to headache at altitude.
HAH often awakened the study participants from sleep or occurred upon wakening and was exacerbated by bending, coughing, or sneezing, suggesting the possibility of intracranial (meaning within the cranium or skull) hypertension as a contributing factor.
What are the symptoms of high altitude headache and acute mountain sickness?
The typical features of HAH are an onset of symptoms within 24 hours of reaching a particular height, duration of less than a day, and in most cases a bilateral, generalised, dull pressure sensation. HAH is not usually reported to be accompanied by hypoxic symptoms such as a desire to overbreathe or shortness of breath after exertion but this may be because those taking part in research considered these to be normal features at altitude and so did not report them.
The principal symptom of acute mountain sickness is moderate or severe headache, combined with one or more other symptoms including nausea, anorexia (loss of appetite), fatigue, dizziness, and sleep disturbances.
Can acute mountain sickness be dangerous?
Acute mountain sickness is relatively benign and usually self-limiting. The rarer syndromes of high-altitude cerebral edema (swelling of the brain) or HACE, and high-altitude pulmonary edema or HAPE are more serious.
In extreme cases, acute mountain sickness may progress to HACE, an acute brain disorder characterized by ataxia (unsteady movements) and a depressed level of consciousness. Magnetic resonance imaging (MRI) studies of individuals with HACE suggest that a proportion of headaches at altitude, and certainly acute mountain sickness, may be part of a similar process, with HACE at the extreme end of the continuum.
HAPE symptoms are incapacitating fatigue, chest tightness, shortness of breath at minimal effort that develops to shortness of breath at rest and when laying flat, and a dry cough. Anyone suffering from worsening symptoms of HACE or HAPE must descend immediately and be evacuated to a medical facility for treatment.
How can high altitude headache and acute mountain sickness be prevented or managed?
Management of the condition is empiric due to the absence of controlled research trials. Preventive strategies include a slow ascent at a rate of 300 metres a day, allowing two days of acclimatisation prior to engaging in strenuous exercise at high altitudes, avoiding alcohol, and liberal fluid intake.
Most high altitude headaches respond to simple analgesics such as paracetamol or ibuprofen.
Acetazolamide 125 mg, two or three times daily, may reduce susceptibility to acute mountain sickness.
I have migraine, can I take my triptans at high altitude?
Triptans have been shown to be effective for migraine headaches experienced at altitude. However one study found ibuprofen 600 mg was effective for high altitude headache whilst sumatriptan 100 mg was ineffective. Nevertheless this study showed that there appeared to be no safety issues provided that there are no other medical reasons to contraindicate sumatriptan.
Can you get high altitude headache whilst travelling by plane?
There is evidence that acute mountain sickness occurs in some unacclimatised people who travel to terrestial altitudes at which barometric pressures are the same as those in commercial aircraft during flight. Whether high altitude headache occurs in passengers in commercial aircraft during flight is unknown.
There is a newly recognised form of headache that appears during flight when the plane is landing or taking off. It is not known how many people experience it and the underlying cause is uncertain, although sinonasal barotrauma has been suggested. Barotrauma means damage to tissues caused by a difference in pressure between the interior and exterior of an air space inside the body. Barotrauma of the ear is the most common type of barotrauma, which develops when the air pressures on the two sides of the eardrum are not equal. Based on the few reported cases, airplane ascent- and descent-triggered headache is characterised by sudden onset, severe pain mainly on one side of the head, in the area of the eye, temple and at the front of the head, or sometimes situated near the side or top of the skull and facial regions.
The symptoms rarely last more than one hour and the pain has been described as jabbing, stabbing, shooting, bursting, pressing, piercing and sharp in quality. It is rare to have any other symptoms, although watering of one eye, nasal congestion and a stuffy feeling of the face may be experienced. Physical examination, routine blood tests and scans of the heads of sufferers have shown normal results.
It is always wise to see your doctor following a first episode of sudden severe headache during an airplane flight, for an evaluation including looking for evidence of barotrauma. For those with repeated episodes, evaluation of the symptoms by an ENT physician to discover any treatable pathology resulting in barotraumas may be helpful. Empirical treatment with an anti-histamine and a nasal decongestant spray might be considered before the flight for those whose evaluation shows normal results but who have repeated episodes of airplane headache where sinonasal barotrauma is an issue.
Travel, including by plane and train, is also a frequently mentioned migraine trigger factor. There is the stress of preparing for a trip – clearing your desk at work, tidying your house, and packing. Then there is the stress of travelling – carrying heavy suitcases, missing meals, coping with a lack of sleep and jet-lag, and climate changes.
Flying is associated with specific problems of reduced oxygen in the circulating air, dehydration, erratic mealtimes and sitting in a cramped seat for several hours. Advance planning can help. Have snacks to eat, avoid alcohol, drink plenty of fluids and walk around the plane regularly.
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