Pro: Headache Should Be a Required Symptom for the Diagnosis of Acute Mountain Sickness

Abstract

The diagnosis of acute mountain sickness (AMS) continues to pose problems to altitude sojourners, physicians, and researchers because of its subjective nature relying essentially on a subject’s appreciation of the presence and severity of symptoms (Roach and Kayser, 2007). Even though AMS is characterized by an ensemble of symptoms (Hackett and Roach, 2001), headache has been recognized as its key symptom at least since Ravenhill’s description in 1911 (Ravenhill, 1913). He described the experiences of ‘‘a majority of newcomers . . . . wake up the next morning with a severe frontal headache . . . . . any attempt at exertion increases the headache, which is nearly always confined to the frontal region.’’ This central role of headache was codified in the current version of the Lake Louise Questionnaire (Roach et al., 1993) that states that a ‘‘diagnosis of AMS is based on a recent gain in altitude, at least several hours at the new altitude, and the presence of headache and at least one of the following symptoms: gastrointestinal upset (anorexia, nausea or vomiting), fatigue or weakness, dizziness or lightheadedness and difficulty sleeping.’’ All surveys of AMS identify headache as the predominant and most prevalent symptom. Singh et al. (1969) noted from a survey of 1925 soldiers rapidly transported to high altitude that ‘‘Headache was not only the commonest but also the most persistent symptom.’’ In a study of 146 trekkers with AMS, Hackett et al. observed the following predominance of headache compared to other symptoms: headache (96%), insomnia (70%), anorexia (38%), nausea (35%), dizziness (27%), excessive breathlessness on exertion or at rest (25%), headache unrelieved by analgesics (26%), reduced urine (19%), marked lassitude (13%), vomiting (14%), incoordination (11%) (Hackett et al 1976). And finally, in a large survey at moderate altitudes, Honigman et al. confirmed the importance of headache in AMS with 62% of 3158 conference attendees reporting moderate to severe headache, and the next most common complaint being sleep disturbance at 31%, and anorexia at 11% and vomiting at only 3% (Honigman et al., 1993). Thus it seems clear that for AMS the cardinal symptom is headache in all studies, in all populations, and at a wide range of altitudes. Our position is that from a research perspective there are important advantages to defining AMS as a collection of symptoms that includes, always, a headache. The same is obviously not true for clinical management of altitude illness. This contrast between the needs for research versus best practice in clinical care forms the basis of our stance. In spite of several decades of sustained research efforts, the basic pathophysiology of AMS still remains elusive. We believe that a focus on high altitude headache will help unravel the puzzle of the pathophysiology of AMS. By stipulating for research purposes that headache be included in the definition of AMS, scientists seek to increase signal-to-noise ratio in AMS subjective symptom reporting. Unfortunately, subjective perception and reporting of symptoms is currently the only way to diagnose and quantify AMS. An example of excess noise is that without obligatory headache, a research subject who had a very bad night sleep and is dizzy at the time of completing the questionnaire could have a ‘‘severe’’ AMS score. Yet we know from several studies that poor sleep at altitude is not necessarily related directly to AMS. And dizziness can be secondary to hypoxemia, or to hypohydration, a common, non-AMS-related phenomenon at high altitude. Similarly, nausea and vomiting can be associated with the onset of AMS, or secondary to a bad headache of any cause, especially migraine, and in the field can also be secondary to gastrointestinal infection. Thus, obligatory presence of headache in the research scoring of AMS symptoms serves an important role by increasing the likelihood that the central symptom of AMS, first reported so clearly by Ravenhill, remains the focus of research studies. It should be noted that