There may be a carryover effect for certain patients with chronic migraine (CM) who respond positively to serial onabotulinumA (BotoxA) injection therapy, according to a study published in Headache.

In this prospective cohort study, researchers evaluated a consecutive series of patients with CM aged ≥19 years (N=131). The patients reported a >6-month history of CM at baseline and no prior history of exposure to BotoxA, and maintained a headache diary during a 30-day pre-treatment baseline period. BotoxA therapy was administered every 12 weeks and was continued in patients who reported a reduction in headache burden at 12 weeks following a second treatment and a >5-day decline in headache day frequency over the 30 days preceding their third treatment. Researchers discontinued BotoxA treatment when patients met a stopping rule, defined as 2 consecutive periods of 12-weeks between-treatments with <5 headache days within each 4-week interval, and migraine disability assessment (MIDAS) questionnaire scores of <10 for each of the 12-week periods.

No clinical worsening or need to resume prophylactic therapy was reported by 80% of the patients (n=105) over the 6 months after discontinuing BotoxA therapy. The mean number of BotoxA treatments received was 6.8 (SD=2.7); the mean number of consecutive months patients were treated before meeting the stopping rule was 17.3 (SD=8.3). For every increase in the number of BotoxA administrations required to reach the stopping rule, the odds of remaining at a low level of headache burden decreased by a factor of 0.576.

This study may have limited relevance to other CM populations because this was a single-center study. The primary end point of “no clinical worsening or associated need to resume prophylactic therapy” following BotoxA discontinuation was assessed on a case-by-case basis rather than by strictly predetermined criteria. Further studies are needed to confirm the existence of a carryover effect after discontinuation of BotoxA and the CM subpopulations likely to experience a sustained reduction in headache burden without continued prophylactic therapy.

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“Although it can be argued that some of our patients were destined spontaneously to experience an extended respite from migraine regardless of any pharmacologic prophylaxis administered, the fact that all patients enrolled reported a history of CM extending to at least 6 months prior to study entry would seem to minimize the likelihood that spontaneous remission occurred at high frequency in our study population,” the researchers concluded. “Our data suggest that, on average, a total course of therapy approximating 18 months (7 treatments) may be required to achieve stabilization of CM sufficient to ensure persistence of a low headache burden following discontinuation of BotoxA.”

Reference

Ching J, Tinsley A, Rothrock J. Prognosis following discontinuation of onabotulinumA therapy in “super-responding” chronic migraine patients [published online September 9, 2019]. Headache. doi: 10.1111/head.13630