The most common of all headache types in the world is the tension headache. Around the 
world, between 80 to 90 percent of the population suffers from tension headaches at least some time in their lives. 88 percent of females and 69 percent of males experience tension headaches with the average age of first onset occurring between nine and twelve years of age.
Episodic tension headache occurs in more than 70% of most of the world’s populations, and chronic tension headaches affect between 1 and 3% of adults.
Tension headaches usually begin during adolescence, affecting three women to every two men. The mechanism of causation is often stress-related or associated with musculoskeletal problems in the neck such as over exercising, sitting at a computer, or minor injuries such as a mild whiplash.
Mild injuries which recur frequently, such as might come from playing basketball of running on uneven ground, have a cumulative effect and may be the nidus for chronic neck tension which is manifest as headache—usually bifrontal in location. This type of headache is classically described as pressure or tightness, like a band around the head, sometimes spreading into or from the neck.
Twenty-eight million Americans, including one out five women and one out of twenty men, experience migraine headaches making migraines the second most common type of head pain. Sixteen to seventeen percent of the U.S. population complains of migraines on a more or less frequent basis. Twenty-five percent of women and eight percent of men suffer a migraine at least once in their lifetime. 60 percent of migraines are unilateral, or present on one side, and 85 percent of migraineurs report some sort of trigger that kicks off their headaches.
Migraine is a primary headache disorder which most often begins at puberty and most significantly affects people aged between 35 and 45 years. Although the process of causation is inadequately understood, it can be considered a true disease with a potential for brain and other organic injury. It appears to be caused by the activation of a mechanism deep in the brain that leads to release of pain-producing inflammatory substances around the nerves and blood vessels of the head. Once the process gets underway to produce a migraine headache, the superficial temporal artery in the skin enlarges. As this process occurs, nerves which surround the artery stretch and release chemicals which cause inflammation and pain. The larger the artery gets, the greater the pain becomes and the more it spreads.
A variant of migraine is called temporal arteritis, which is a true inflammatory disease which puts the sufferer at risk of blindness and requires that the patient have a segment of the artery removed to protect the eyes and other organs.
Migraine is recurrent, often life-long, and is characterized most often by episodic attacks, which may be severe enough to render the migraineur bed-ridden or even to require hospitalization. Interestingly, the incidence is higher in rural areas and among patients in the lowest income quartile. The rate of ER visits is double that in the wealthiest communities in the country.
Attacks include features such as headache of moderate or severe intensity, nausea–the most characteristic symptom—sometimes abdominal symptoms, one-sided and/or pulsating quality pain, aggravation by routine physical activity and especially by vigorous activity, have a duration of a few hours to two or three days. The attack frequency is anywhere between once a year and once a week, but a few people have what can best be described as status migrainous syndrome where a rolling series of headaches or unrelenting symptoms may last for days or even weeks.
In children, attacks tend to be of shorter duration and abdominal symptoms more prominent.
Migraine is a genetic disorder which is both a significant vascular disease, and also a serious neurologic disease. 80% of migraine patients have a family history of migraine. Identical twins are more than twice as likely to have migraine than are fraternal twins.
The underlying science of the condition is bolstered by the evidence that several chromosomal and gene abnormalities have been isolated that lead to the hyper-excitability of the nervous system, and they are related to migraine and to seizure disorders. The genetic hyper-excitability results in a lower threshold for activation and longer retention of sensory information which elevates the tone for re-excitement both during and between episodes.
Migraineurs tend to do well in school, and are artistic, conscientious, well organized and aware of feelings and needs within their environment—perhaps excessively so.
In people who do not suffer from migraine, their nervous systems are largely balanced between risk factors—triggers—and protective factors. Migraineurs have an imbalance of these competing factors. A migraine attack is triggered—often by multiple triggers—occurring over a short period of time.
The triggers include hormones as is seen in perimenstrual migraine, too little or too much sleep, physical or emotional stress, and elements in the environment including bright lights, blinking or flashing lights, fasting from food, and allergens. This imbalance causes the migraineur to have a brain which is characterized by an enduring–abnormally elevated–electrical potential that can generate attacks of headache due to factors that are innocuous in the nonmigraineur, and do not cause headache in them.
The process of migraine has fascinated scientists for hundreds of years and has been the subject of considerable productive research. The early or premonitory symptoms include fatigue, food craving, uncontrollable yawning, muscle pain and aches, and sinus congestion. Some, but not all, of these premonitory symptoms go on to the classical headache.
Next comes the aura—focal neurologic deficits, usually short-lived but serve as a warning that a headache is on its way in all likelihood. A neurological aura occurs in about 25% of cases. Then comes the headache itself. It is often mild in its early stages but in time progresses to moderate to severe symptoms.
The classical symptoms described above begin to appear and finally to take over the life of the sufferer. With rest in a quiet dark room and sometimes with medication, the headache eventually subsides and resolves; but the patient is left with a postdrome of lethargy, weakness, and often, confusion.
Considerable scientific investigation has gone into an effort to understand the phenomenon of the migraine aura because it seems to hold the answer to what migraine is and perhaps what can eventually be done to prevent or treat the condition more effectively.
It is known that migraine is associated with a neuronal network excitability, as described above. Specifically the excitability occurs with activation and sensitization of the trigeminovascular system—the blood vessels associated with the fifth cranial nerve, the trigeminal.
Cortical spreading depression (CSD), recognized as the neuronal phenomenon underlying the common visual aura, is believed to begin in the occipital region and then gradually spread forward. This phenomenon is accompanied by a transient diminution in blood in selected cortical arterioles, followed by hyperemia—increased blood supply–in other parts of the cortex.
Various molecular and cellular mechanisms may lead to the increased susceptibility to CSD in migraineurs, which could potentially play an important role in the pathophysiology of migraine variants. Researchers have suggested that a vasogenic leakage from leptomeningeal vessels (small blood vessels of the inner coverings of the brain), with activation of the trigeminovascular system, probably contribute to the prolonged aura in patients with hemiplegic migraine which will be described more fully in the next blog post.
In episodic migraine, the nervous system regains its normal function with little indication of having suffered any damage.
Chronic migraine, on the other hand, occurs in a nervous system that allows migraine attacks to occur with such a frequency that the nervous system cannot fully recover between episodes.
Lacking full recovery, especially over an extended period of time, the nervous system shows progressive dysfunction manifest not only during the acute episode, but also between episodes.
The evolution of chronic migraine results in lessening ability to defend against triggers.
The dysfunction can lead to medication overuse, physiologic disruptions such as sleep disorders, irritable bowel syndrome, fibromyalgia, cutaneous allodynia—hyper-sensitive skin wherein even a light touch produces pain–mood and anxiety disorders including panic episodes and persistent depression.
Headaches become more debilitating and interfere more seriously with mental function, work productivity, and interpersonal relationships. The described co-morbidities intensify and persist more indelibly as the chronic migraine evolves. Treatment becomes more difficult and less successful.
Evidence is accruing that chronic migraine and the accompanying co-morbidities may cause phenotypical end-organ damage. Brain white matter develops increasing hyperintensities and may develop oxidative damage to ascending and descending pain pathways owing to iron deposition. There are several unusual and specific different types of migraine which will be discussed in the next blog post along with other fairly uncommon causes of head pain.
Any headache is annoying and painful, but recurrent and chronic headache syndromes are also disabling, sometimes significantly so. What is said for tension headache can be more emphatically described for migraine.
In the Global Burden of Disease Study, updated in 2004, migraine, on its own, was found to account for 1.3% of years lost due to disability (YLD).
Headache sufferers spend over $2 billion on over-the-counter medications. Headaches cost American businesses approximately 157 million missing work hours and 150 million days of lost productivity each year due to migraine headaches and $12 billion in direct or indirect costs.
10% of emergency department visits each year are for headaches, and. headaches are the seventh leading cause of ambulatory care accounting for over 18.3 million outpatient visits per year.
Next in this series of blog posts on headache, we will discuss less common headache types and then we’ll move on in to headache treatments.
Carl Douglass – Author
Carl Douglass Books
www.carldouglass.com
“Neurosurgeon Turned Author Writes With Gripping Realism”
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