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headache (hedīāk″)   pain in the head; see also migraine. One of the most common ailments of humans, it is a symptom rather than a disorder in itself; it accompanies many diseases and conditions, including emotional distress. Although recurring headache may be an early sign of serious organic disease, relatively few headaches are caused by disease-induced structural changes. Most result from vasodilation of blood vessels in tissues surrounding the brain, or from tension in the neck and scalp muscles.




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