As Botox has become more popular in the treatment of Chronic Migraines, treating physicians must make sure that their diagnosis is appropriate in order to get maximum the benefit from it. The patient should have had at least four episodes, each one with at least two of these features:
- Unilateral distribution (one-sided)
- Pulsatile quality (throbbing)
- Moderate or severe pain (a least 5/10)
- Worsened by physical activities
They must have at least one of the following: nausea or vomiting or sensitivity to light or noise.
Patients have an aura when the visual effects precede the actual episode at least by five minutes; it usually involves an expanding blind spot or some visual scintillations (shimmering objects) An aura can also manifest itself by difficulties of speech and/or language like missing words or inability to spell certain ones. It could also involve sensory phenomena like dysesthesias in the upper or lower extremities, muscular weakness, gait imbalance or cranial nerve problems.
Episodic migraines occur when the patient has 14 or fewer episodes per month. Chronic Migraines occur when the patient has 15 or more episodes per month. If the patient has headaches more than half the number of days in a month, with characteristic features in 8 of them, then he/she has CM.
The Food and Drug administration (FDA) has only approved Onabotulinum toxin A for the use in Chronic Migraines so far; its safety and efficacy were proved in the phase III of the “Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) where the participants were treated every 12 weeks, whether or not their episodes had ameliorated or there was a good outcome after 2 treatment cycles. On average the study participants had 19 episodes per month and after treatment with Botox they had 8-9 episodes less. A quarter of these patients improved by a 75% reduction.
Only a 30G or 31 G half-inch needle should be used for injections as longer needles penetrate deeper with the consequent risk of muscle weakness and associated cervical pain. Preservative-free normal saline is the only accepted solution to dilute the drug before the injection. With an effective dose using 2ml/100 units of Onabotulinum A, a mean dosage of 165 should be used.
In order to avoid the collateral effect of ptosis, the frontalis muscle should be carefully injected; the needle should not be moved higher or pointed up.in order to avoid diffusion of the liquid to it. Following the PREEMPT guidelines, one injection at a 45% angle of 5 units of Onabotulinum A should be injected in four different places of the frontalis muscle (for a total amount of 20 units)
If the patient had pre-existing cervical pain and/or weakness, the injection of the drug in the occipitalis, paraspinal or trapezius muscles can worsen that symptom and the ensuing limitations. Following the PREEMPT guidelines, 5 units of Onabotulinum A should be administered at two different places on both the right and left sides for a total dosage of 20 units at four different sites.
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