Porth's Essentials of Pathophysiology, 4e

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Nervous System

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prolonged aura, or migrainous infarction. 48 In most cases, preventative treatment must be taken daily for months to years. First-line agents include β -adrenergic blocking medications (e.g., propranolol, atenolol), anti- depressants (amitriptyline), and antiseizure medications (e.g., divalproex, valproic acid). When a decision to dis- continue preventive therapy is made, the medications should be gradually withdrawn. Cluster Headache Cluster headaches are relatively uncommon headaches that occur in about 1 in 1000 individuals, affecting men (80% to 85%) more frequently than women with the typical age of onset between 20 to 40 years of age. 50 These headaches tend to occur in clusters over weeks or months, followed by a long, headache-free remission period. Cluster headache is a type of primary neuro- vascular headache that typically includes severe, unre- lenting, unilateral pain located, in order of decreasing frequency, in the orbital, retro-orbital, temporal, supra- orbital, and infraorbital regions. 50–52 The pain is of rapid onset, builds to a peak in approximately 10 to 15 min- utes, and lasts for 15 to 180 minutes. The pain behind the eye radiates to the ipsilateral trigeminal nerve (e.g., temple, cheek, gum). The headache frequently is associ- ated with one or more symptoms such as restlessness or agitation, conjunctival redness, lacrimation, nasal con- gestion, rhinorrhea, forehead and facial sweating, mio- sis, ptosis, and eyelid edema. Because of their location and associated symptoms, cluster headaches are often mistaken for sinus infections or dental problems. The underlying pathophysiologic mechanisms of clus- ter headaches are not completely known. It is thought that heredity, through an autosomal dominant gene, plays some role in the pathogenesis of the headaches. The most likely pathophysiologic mechanisms include the interplay of vascular, neurogenic, metabolic, and humoral factors. The regulating centers in the hypothalamus are thought to play a role because of circadian biologic changes and neuroendocrine disturbances (e.g., changes in cortisol, prolactin, and testosterone) that are observed both in active periods and during clinical remission. Because of the relatively short duration and self- limited nature of cluster headache, oral preparations typically take too long to reach therapeutic levels. The most effective treatments are those that act quickly (e.g., oxygen inhalation and subcutaneous sumatriptan). Intranasal lidocaine also may be effective. 51,52 Oxygen inhalation may be indicated for home use. Prophylactic medications for cluster headaches include ergotamine derivatives, verapamil (a calcium channel blocker), corti- costeroids, and valproic acid. Deep-brain surgical neuro- stimulation is an experimental approach beginning to show promise in the elimination of cluster headaches. 51 Tension-Type Headache The most common type of headache is tension-type head- ache. Unlike migraine and cluster headaches, tension-type headache usually is not sufficiently severe that it interferes with daily activities. Tension-type headaches frequently

are described as dull, aching, diffuse, nondescript head- aches, occurring in a hatband distribution around the head, and not associated with nausea or vomiting or worsened by activity. They can be infrequent, episodic, or chronic. The exact mechanisms of tension-type headache are not known and the hypotheses of causation are con- tradictory. One popular theory is that it results from sustained tension of the muscles of the scalp and neck. Another theory suggests that migraine headache may be transformed gradually into chronic tension-type head- ache. Oromandibular dysfunction, psychogenic stress, anxiety, and depression may contribute, and overuse of analgesics or caffeine may also be involved. 53 Tension-type headaches often are more responsive to nonpharmacologic techniques, such as biofeedback, mas- sage, acupuncture, relaxation, imagery, and physical ther- apy, than other types of headache. For persons with poor posture, a combination of range-of-motion exercises, relaxation, and posture improvement may be helpful. The medications of choice for acute treatment of ten- sion-type headaches are analgesics, including acetylsali- cylic acid, NSAIDs, and acetaminophen. 53 Persons with infrequent tension-type headache usually self-medicate using over-the-counter analgesics to treat the acute pain, and do not require prophylactic medication. These agents should be used cautiously because rebound headaches can develop when the medications are taken regularly. Other medications, including the entire range of migraine medications, may be tried in refractory cases. Chronic Daily Headache The term chronic daily headache (CDH) is used to refer to headaches that occur 15 days or more a month, including those due to medication overuse. 54,55 Little is known about the prevalence and incidence of CDH. Diagnostic criteria for CDH are not provided in the IHS Classification System. The cause of CDH is unknown, although there are several hypotheses. They include transformed migraine headache, evolved tension-type headache, new daily persistent headache, and post- traumatic headache. In many persons, CDH retains certain characteristics of migraine, whereas in others it resembles chronic tension-type headache. Chronic daily headache may be associated with chronic and episodic tension-type headache. New daily persistent headache may have a fairly rapid onset, with no history of migraine, tension-type headache, trauma, or psycho- logical stress. Although overuse of symptomatic medi- cations (e.g., analgesics, ergotamine) has been related to CDH, there is a group of patients in whom CDH is unrelated to excessive use of medications. For patients with CDH, a combination of pharma- cologic and behavioral interventions may be necessary. As with tension-type headaches, nonpharmacologic techniques, such as biofeedback, massage, acupunc- ture, relaxation, imagery, and physical therapy, may be helpful. Measures to reduce or eliminate medica- tion and caffeine overuse may be helpful. If the patient is abusing medications, the overuse must be managed