|March 26, 2016|
A headache or cephalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the pain-sensitive structures around the brain. Several areas of the head and neck have these pain-sensitive structures, which are divided in two categories: within the cranium (blood vessels, meninges, and the cranial nerves) and outside the cranium (the periosteum of the skull, muscles, nerves, arteries and veins, subcutaneous tissues, eyes, ears, sinuses and mucous membranes).
There are a number of different classification systems for headaches. The most well-recognized is that of the International Headache Society. Treatment of a headache depends on the underlying etiology or cause, but commonly involves analgesics.
Headaches are most thoroughly classified by the International Headache Society's International Classification of Headache Disorders (ICHD), which published the second edition in 2004. This classification is accepted by the WHO.
Other classification systems exist. One of the first published attempts was in 1951. The National Institutes of Health developed a classification system in 1962.
The International Classification of Headache Disorders (ICHD) is an in-depth hierarchical classification of headaches published by the International Headache Society. It contains explicit (operational) diagnostic criteria for headache disorders. The first version of the classification, ICHD-1, was published in 1988. The current revision, ICHD-2, was published in 2004.
The classification uses numeric codes. The top, one-digit diagnostic level includes 13 headache groups. The first four of these are classified as primary headaches, groups 5-12 as secondary headaches, cranial neuralgia, central and primary facial pain and other headaches for the last two groups.
The ICHD-2 classification defines migraines, tension-types headaches, cluster headache and other trigeminal autonomic cephalalgias as the main types of primary headaches. Also, according to the same classification, headaches due to stabbing, cough, exertion and sexual activity are classified as primary headaches. The daily-persistent headaches along with the hypnic headache and thunderclap headaches are considered primary headaches as well.
Secondary headaches are classified based on their etiology and not on their symptoms. According to the ICHD-2 classification, the main types of secondary headaches include those that are due to head or neck trauma such as whiplash injury, intracranial hematoma, post craniotomy or other head or neck injury. Headaches caused by cranial or cervical vascular disorders such as ischemic stroke and transient ischemic attack, non-traumatic intracranial hemorrhage, vascular malformations or arteritis are also defined as secondary headaches. This type of headaches may also be caused by cerebral venous thrombosis or different intracranial vascular disorders. Other secondary headaches are those due to intracranial disorders that are not vascular such as low or high pressure of the cerebrospinal fluid pressure, non-infectious inflammatory disease, intracranial neoplasm, epileptic seizure or other types of disorders or diseases that are intracranial but that are not associated with the vasculature of the central nervous system. ICHD-2 classifies headaches that are caused by the ingestion of a certain substance or by its withdrawal as secondary headaches as well. This type of headache may result from the overuse of some medications or by exposure to some substances. HIV/AIDS, intracranial infections and systemic infections may also cause secondary headaches. The ICHD-2 system of classification includes the headaches associated with homeostasis disorders in the category of secondary headaches. This means that headaches caused by dialysis, high blood pressure, hypothyroidism, and cephalalgia and even fasting are considered secondary headaches. Secondary headaches, according to the same classification system, can also be due to the injury of any of the facial structures including teeth, jaws, or temporomandibular joint. Headaches caused by psychiatric disorders such as somatization or psychotic disorders are also classified as secondary headaches.
The ICHD-2 classification puts cranial neuralgias and other types of neuralgia in a different category. According to this system, there are 19 types of neuralgias and headaches due to different central causes of facial pain. Moreover, the ICHD-2 includes a category that contains all the headaches that cannot be classified.
Although the ICHD-2 is the most complete headache classification there is and it includes frequency in the diagnostic criteria of some types of headaches (primarily primary headaches), it does not specifically code frequency or severity which are left at the discretion of the examiner.
The NIH classification consists of brief definitions of a limited number of headaches.
The NIH system of classification is more succinct and only describes five categories of headaches. In this case, primary headaches are those that do not show organic or structural etiology. According to this classification, headaches can only be vascular, myogenic, cervicogenic, traction and inflammatory.
GNU Free Documentation License. It uses material from the Wikipedia article "Headache Symptoms".
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