A good predictor of response to Botox injections in chronic migraine patients has been found by Spanish researchers.
While Botox is a very effective treatment for chronic migraines and possibly other types of headaches and pain, it does not help everyone. Approximately 30% of patients with chronic migraine headaches do not respond to Botox. We usually try at least two sets of injections three months apart before considering the patient to be a non-responder. Considering that Botox is an expensive treatment, it would be very useful to know beforehand which patients will respond and which will not. Besides the cost, it would also save patients time, during which they could be trying other treatments.
Some studies show that having a constricting headache or pain in the eye is usually a positive predictor of response to Botox. On the other hand, exploding headache (that is when the pain is felt pushing from the inside out), is less likely to respond to Botox injections. However, these are very subjective descriptions and predictions based on them are not that reliable.
A new study by Spanish researchers just published in the journal Headache reported that the levels of CGRP (calcitonin gene-related peptide) and VIP (vasoactive intestinal peptide) in patients’ blood are good predictors of response to Botox in chronic migraine sufferers. These two chemicals, which circulate in the blood and perform various important functions in the brain have long been the subject of scientific research. Actually, we think that Botox works by blocking the release of CGRP from the peripheral nerve endings. Dr. Julio Pascual and his colleagues measured the levels of these two chemicals in chronic migraine patients before they were treated with Botox. Botox was administered according to the standard protocol every 12 weeks for at least two treatment cycles. A patient was considered a moderate responder when both: 1) moderate-severe headache episodes were reduced by between 33 and 66%; and 2) subjective benefit on a visual scale from 0 to 100 was recorded by the patient of between 33-66%. Patients were considered to be excellent responders when both items improved by more than 66%. Those without improvement of at least one-third in the two items were considered as nonresponders.
The study involved 81 patients with chronic migraine and 33 healthy controls. CGRP and VIP levels were significantly increased in the chronic migraine population vs controls. CGRP and, to a lesser degree, VIP levels were significantly increased in responders vs nonresponders. The probability of being a responder to Botox was 28 times higher in patients with a CGRP level above the threshold.
The measurement of CGRP and VIP is done only by research institutions and is not yet offered by commercial laboratories. However, considering how much money can be saved by not giving Botox to those who are unlikely to respond, these tests should become widely available once these findings are confirmed by other researchers.
