['treatment for prevention of chronic migraine']
['placebo']

        Inclusion Criteria:

          -  History of at least 5 attacks of migraine without aura and/or migraine with visual
             sensory, speech and/or language, retinal or brainstem aura.

          -  History of ≥ 15 headache days per month of which ≥ 8 headache days were assessed by
             the subject as migraine day.

          -  ≥ 4 distinct headache episodes, each lasting ≥ 4 hours OR if shorter, associated with
             use of a triptan or ergot-derivative on the same calendar day based on the eDiary
             calculations.

          -  Demonstrated at least 80% compliance with the eDiary.

        Exclusion Criteria:

          -  History of cluster headache or hemiplegic migraine headache

          -  Unable to differentiate migraine from other headaches

          -  Failed > 3 medication categories due to lack of efficacy for prophylactic treatment of
             migraine .

          -  Received botulinum toxinin head or neck region within 4 months prior to screening.

          -  Used a prohibited migraine prophylactic medication, device or procedure within 2
             months prior to the start of the baseline phase
      