Allodynia with migraine headache symptoms
Allodynia comes from the words “allo” which means “other” and “dynia” which means “pain.” Clinically it refers to pain produced by a non-painful stimulus, such as touch. Allodynia is an uncomfortable heightened sensitivity to touch. Normally it doesn’t hurt to touch the head or the brow or the temple, but during the late stages of a migraine or during medication overuse headache, a simple touch to the head or temple may be perceived as painful. This is like a sunburn. Normally if I touch my arm it doesn’t hurt but after a sunburn at the beach, my arm is painful to touch. This is what allodynia is like.
Allodynia can be divided into: tactile allodynia-pain from touch or light pressure like a belt or bra strap, mechanical allodynia-pain from motion across the skin such as light massage or the touch of fabric, and thermal allodynia-pain from heat or cold that makes the limbs feel needle like, sharp pain.
The pain of allodynia can be provoked by combing or brushing the hair, pulling your hair back/ponytail, shaving, showering, wearing contact lenses or glasses, wearing necklaces, earrings, or tight clothes. Allodynia may come while taking a shower, when water hits your face, while resting your face on the pillow on the side of your one-sided migraine, or while being exposed to heat (like when cooking), or exposed to cold. The pressure of a strand of hair may feel like the jab of a hot knife. Allodynia is the migraine patient who notes on the third day of headache suffering that it hurts her to brush her hair or lay her head on the pillow.
Allodynia occurs mostly in long duration episodic migraine attacks or in patients transformed to medication overuse headache by overtreatment of headache with analgesics. The duration of migraine is 4-72 hours, as defined by the International Classification of Headache. Episodic Migraine may occur only 2 times a week. One can easily see by doing simple math that multiplying 72 hours or 3 days by 2 equals 6 days. This is why episodic migraine rarely occurs more than twice a week. Daily headache or headache 3 or 4 days a week is usually Chronic Migraine (CM), a syndrome defined as more than 15 headache days a week, 8 of which have migraine features. Seventy percent of persons with CM have a headache syndrome from overtreating with analgesics, caffeine, or triptans called Medication Overuse Headache. Medication Overuse Headache was formerly called Rebound Headache.
An attack of migraine has 4 stages: 1) trigeminal activation, 2) neurochemical release, 3) arterial vasodilatation, 4) central sensitization of the thalamus in the brain. In general patients with an attack of migraine are at stage 3 in two hours and after two hours they are in stage 4. Thus, patients with long-duration (headaches lasting more than several hours) spend most of their time in stage 4 central sensitization. Patients with medication overuse headache are continuously in stage 4 central sensitization which causes allodynia.
With episodic migraine the allodynia clears when the headache ends and the offending neurochemicals are metabolized and excreted. The same thing occurs during treatment of medication overuse headache when the patient is detoxed off of analgesics, caffeine, or triptans and in time the offending neurochemicals are metabolized and the headache clears.