Botulinum Toxin Injection for Chronic Migraine Headache

Indications and Clinical Considerations

Migraine headache is defined as a periodic unilateral headache that may begin in childhood but almost always develops before the age 30 years. Attacks may occur with a variable frequency ranging from every few days to once every several months. More frequent migraine headaches can occur and in some patients may become chronic. Migraine headaches are often associated with a phenomenon called analgesic rebound. Between 60% and 70% of patients suffering from migraine are female, and many report a family history of migraine headaches. Migraineurs have been described as having a unique personality type characterized by a meticulous, neat, compulsive, and often rigid nature. They tend to be obsessive in their daily routines and often find it hard to cope with the stresses of everyday life. Migraine headaches may be triggered by changes in sleep patterns or diet or by the ingestion of tyramine-containing foods, monosodium glutamate, nitrates, chocolate, or citrus fruits. Changes in endogenous and exogenous hormones such as occur with the use of birth control pills can also trigger migraine headache. Approximately 20% of patients suffering from migraine headache also experience a painless neurologic event before the onset of headache pain called an aura ( Fig. 25.1 ). Aura most often takes the form of visual disturbance but may also manifest as an alteration in smell or hearing; these are called olfactory and auditory auras, respectively.

Migraine headache is by definition a unilateral headache. Although with each episode the headache may change sides, the headache is never bilateral. The pain of migraine headache is usually periorbital or retro-orbital. It is pounding in nature, and its intensity is severe. The onset-to-peak of migraine headache is rapid, ranging from 20 minutes to 1 hour. In contradistinction to tension-type headache, migraine headache is often associated with systemic symptoms, including nausea and vomiting, photophobia, and sonophobia, as well as alterations in appetite, mood, and libido. Menstruation is also a common trigger of migraine headaches. Migraine that manifests without other neurologic symptoms is called migraine without aura. Migraine headache that occurs 15 or more days a month that includes a minimum of 8 days of migraine-like symptoms for more than 3 months is termed chronic migraine headache and may be amenable to treatment with pericranial injection of botulinum injection ( Fig. 25.2 ).

As mentioned, approximately 20% of patients suffering from migraine headache also experience a painless neurologic event before the onset of headache pain called aura (see Fig. 25.1 ). Aura is thought to be the result of ischemia of specific regions of the cerebral cortex. Visual aura will often occur from 30 to 60 minutes before the onset of headache pain and may take the form of blind spots called scotoma or a zigzag disruption of the visual field called fortification spectrum ( Fig. 25.3 ). Occasionally, migraine patients may lose an entire visual field during aura. Auditory aura most often takes the form of hypersensitivity to sound, but other alterations of hearing, such as sounds perceived as farther away than they are, have also been reported. Olfactory aura may take the form of strong odors of substances that are not actually present or extreme hypersensitivity to otherwise normal odors of items such as coffee or copy machine toner. Migraine headache that is preceded by aura is called migraine with aura.

Rare patients who suffer from migraine will experience prolonged neurologic dysfunction associated with their headache pain. Such neurologic dysfunction may last for more than 24 hours and is termed migraine with prolonged aura . Although extremely rare, such patients are at risk for developing permanent neurologic deficit, and risk factors such as hypertension, smoking, and oral contraceptives must be addressed. Even less common than migraine with prolonged aura is migraine with complex aura. Patients suffering from migraine with complex aura experience significant neurologic dysfunction associated with their headache pain. This dysfunction may include aphasia or hemiplegia. As with migraine with prolonged aura, patients suffering from migraine with complex aura may develop permanent neurologic deficits.

The patient suffering from all forms of migraine headache will appear systemically ill. Pallor, tremulousness, diaphoresis, and light sensitivity are common physical findings. Tenderness of the temporal artery and associated area may also be present. If aura is present, neurologic examination results will be abnormal; otherwise, the neurologic examination is within normal limits before, during, and after migraine without aura.

There is no specific test for migraine headache. Testing is aimed primarily at identifying occult pathology or other diseases that may mimic migraine headache. These include tumor; diseases of the eyes, ears, nose, and throat; glaucoma; temporal arteritis; sinusitis; cerebral hemorrhage pseudotumor cerebri; and chronic subdural hematoma ( Box 25.1 ). All patients with a recent onset of headache thought to be migraine should undergo magnetic resonance imaging (MRI) scan of the brain. If neurologic dysfunction accompanies the patient’s headache symptomatology, the MRI scan should be performed with and without gadolinium contrast medium; magnetic resonance angiography should also be considered. MRI scans should also be performed in patients with previously stable migraine headache who are experiencing an inexplicable change in headache symptomatology. Screening laboratory testing that includes erythrocyte sedimentation rate, complete blood count, and automated blood chemistry should be performed if the diagnosis of migraine is in question. Ophthalmologic evaluation is indicated in those patients suffering from headache who experience significant ocular symptoms.