Britt Talley Daniel MD
7777 Forest Lane Suite B-220
Dallas, Texas 75230
Allodynia with migraine and medication overuse headache
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, shaving, showering, wearing glasses, or earrings. 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 2004. Migraine is generally an episodic, paroxysmal disorder occurring at most 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 periodic migraine rarely occurs more than twice a week. Daily headache or headache 3 or 4 days a week is usually Chronic Daily Headache (CDH), a syndrome defined as >15 headache days a week. About 70% of persons with CDH have a common headache syndrome from overtreating with analgesics, caffeine, or triptans called Medication Overuse Headache. Also read my article on the subject of Medication Overuse Headache on this blog.
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) episodic migraine attacks spend most of the time in stage 4 central sensitization. The general thinking is that all patients with medication overuse headache are continuously in stage 4 central sensitization. Both of these circumstances can produce 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. In time the offending neurochemicals are metabolized and consequently the headache clears.