The brain itself is insensitive. The only possible sources of PAIN within the skull are blood vessels, the DURA MATER (see MENINGES), and some of the CRANIAL NERVES. Yet headache is one the most frequent complaints confronting the family medical practitioner. Most cases therefore have an extra-cranial origin, and of these the most common is the so-called TENSION HEADACHE. This condition is thought to be associated with spasm of the muscles of the scalp, triggered in an unknown way by factors such as depression, eye-strain, lack of SLEEP, dietary indiscretion, hangovers and hang-ups. MIGRAINE headaches are quite distinct and are primarily vascular in character: they may be linked to a local disorder of SEROTONIN function, and are usually preceded by transient changes in the underlying CEREBRAL CORTEX. CLUSTER HEADACHE (Horton’s cephalalgia) is a distressing variant, with AUTONOMIC involvement. Severe head pain is also a feature of giant-cell arteritis, an auto-immune inflammatory (see INFLAMMATION) condition usually affecting the superficial temporal artery and its branches, and leading to retinal infarction and BLINDNESS unless halted with IMMUNOSUPPRESSANT drugs (see also INFARCT). Pain referred to the head also commonly arises from the teeth, cervical spine, glaucoma, postherpetic and trigeminal NEURALGIA, and inflammation of the nasal sinuses.
Intracranial causes of headache include any condition causing mechanical traction or displacement of the dura, blood vessels or cranial nerves. Space-occupying lesions such as tumours, abscesses, cysts and blood clots (haematomata) are obvious examples that usually call for surgery. Sometimes these conditions act indirectly by obstructing the free flow of CEREBROSPINAL FLUID, causing a rise in intracranial pressure and producing HYDROCEPHALUS. Conversely, an abnormally low intracranial pressure following leakage of cerebrospinal fluid after LUMBAR PUNCTURE, is a notorious cause of IATROGENIC headache. Some causes of headache can be recognized by the special character of the pain. The ‘mule-kick’ headache that follows rupture of an artery in the SUBARACHNOID SPACE is remarkable for its abrupt onset and severity. Recurrent early-morning throbbing headache may signal HYPERTENSION. When in doubt, skull X-ray and other neuroimaging procedures, examination of the cerebrospinal fluid obtained from the spine by diagnostic lumbar puncture, and ophthalmoscopic examination of the RETINA may assist diagnosis. Treatment may be straightforward where a cause is identified, while other cases may obtain symptomatic relief from analgesics (such as paracetamol). Tension headache and psychogenic headache tend to be less responsive to treatment, while the relief of post-concussional headache commonly requires the satisfactory conclusion of legal proceedings.
L.JACOB HERBERG
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