Porth's Essentials of Pathophysiology, 4e

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Somatosensory Function, Pain, and Headache

C h a p t e r 3 5

There are two major types of migraine headache— migraine without aura and migraine with aura. Migraine without aura , which accounts for approximately 85% of migraines, is a pulsatile, throbbing, unilateral head- ache that typically lasts 1 to 2 days and is aggravated by routine physical activity. The headache is accompanied by nausea and vomiting, which often is disabling, and sensitivity to light and sound. Visual disturbances occur quite commonly and consist of visual hallucinations such as stars, sparks, and flashes of light. 43 Migraine with aura has similar symptoms, but is preceded by a sensory experience called an aura . It typically consists of visual symptoms, including flickering lights, spots, or loss of vision; sensory symptoms, including feeling of pins or needles, or numbness; and speech disturbances or other neurologic symptoms. These symptoms precede the headache, developing over a period of 5 to 20 min- utes, and last from 5 minutes to 1 hour. 43 Although only a small percentage of persons with migraine experience an aura before an attack, many persons without aura have prodromal symptoms, such as fatigue and irritabil- ity, that precede the attack by hours or even days. A retinal migraine is a rare form of migraine char- acterized by recurrent attacks of fully reversible scintil- lations (visual sensation of sparks or flashes of light), scotomata (visual blind spots), or blindness affect- ing one eye, followed within an hour by a headache. Migraines can also be chronic, occurring on 15 or more days per month for 3 months or more, in the absence of medication overuse. Migraine headache also can present as a mixed headache, including symptoms typi- cally associated with tension-type or sinus headaches. These are called transformed migraine and are difficult to classify. Migraine headaches occur in children as well as adults. 45,46 Before puberty, migraine headaches are equally distributed between the sexes. The essential diagnostic criterion for migraine in children is the pres- ence of recurrent headaches separated by pain-free peri- ods. Diagnosis is based on at least three of the following symptoms or associated findings: abdominal pain, nau- sea or vomiting, throbbing headache, unilateral loca- tion, associated aura (visual, sensory, motor), relief during sleep, and a positive family history. 46 Symptoms vary widely among children, from those that interrupt activities and cause the child to seek relief in a dark environment to those detectable only by direct question- ing. A common feature of migraine in children is intense nausea and vomiting. The vomiting may be associated with abdominal pain and fever; thus, migraine may be confused with other conditions such as appendici- tis. More than half of children with migraine undergo spontaneous prolonged remission after their 10th birth- day. Because headaches in children can be a symptom of other, more serious disorders, including intracranial lesions, it is important that other causes of headache that require immediate treatment be ruled out. The pathophysiologic mechanisms of the pain asso- ciated with migraine headaches remain poorly under- stood. Although many alternative theories exist, it is well established that during a migraine the trigeminal cranial nerve (CN V) becomes activated. 47 This may lead to the

release of neuropeptides, causing painful neurogenic inflammation within the meningeal vasculature charac- terized by plasma protein extravasation, vasodilation, and mast cell degranulation. Another possible mecha- nism implicates neurogenic vasodilation of meningeal blood vessels as a key component of the inflammatory processes that occur during migraine. Supporting the neurogenic basis for migraine is the frequent presence of premonitory symptoms before the headache begins; the presence of focal neurologic disturbances, which cannot be explained in terms of cerebral blood flow; and the numerous accompanying symptoms, including those related to autonomic and somatic nervous system dysfunction. Fluctuations in hormone levels, particularly in estro- gen levels, are thought to play a role in the pattern of migraine attacks. For many women, migraine headaches coincide with their menstrual periods. Dietary substances, such as monosodium glutamate, aged cheese, and choco- late, also may precipitate migraine headaches. The actual triggers for migraine are the chemicals in the food, not allergens. The treatment of migraine headaches includes pre- ventive and abortive nonpharmacologic and pharmaco- logic treatment. 48 Nonpharmacologic treatment includes the avoidance of migraine triggers, such as foods, that precipitate an attack. Many persons with migraines ben- efit from maintaining regular eating and sleeping habits. Measures to control stress, which also can precipitate an attack, also are important. During an attack, many per- sons find it helpful to retire to a quiet, darkened room until symptoms subside. Pharmacologic treatment involves both abortive therapy for acute attacks and preventive therapy. A wide range of medications is used to treat the acute symptoms of migraine headache. First-line agents include aspirin and other NSAIDs (e.g., naproxen sodium, ibuprofen), combinations of acetaminophen, acetylsalicylic acid, and caffeine; serotonin (5-HT 1 ) receptor agonists (e.g., sumatriptan); ergotamine derivatives (e.g., dihydroergot- amine); and antiemetic medications (e.g., ondansetron, metoclopramide). Non-oral routes of administration may be preferred in individuals who develop severe pain rapidly or on awakening, or in those with severe nau- sea and vomiting. Both sumatriptan and dihydroergota- mine have been approved for intranasal administration. For intractable migraine headache, dihydroergotamine may be administered parenterally with an antiemetic or opioid analgesic. 49 Frequent use of abortive headache medications may cause rebound headache. Because of the risk of coronary vasospasm, the 5-HT 1 receptor agonists should not be given to persons with coronary artery disease. Ergotamine preparations can cause uter- ine contractions and should not be given to pregnant women. They also can cause vasospasm and should be used with caution in persons with peripheral arterial disease. Preventive pharmacologic treatment may be neces- sary if migraine headaches become disabling, if they occur more than two or three times a month, if abortive treatment is being used more than two times a week, or if the individual has hemiplegic migraine, migraine with