Key Inclusion Criteria:

   - Between the ages of 18 and 75 years

   - Been previously diagnosed with migraine (with or without aura), in accordance with the
   ICHD-3 criteria

   - Experiences between 8 to 20 headaches days per month (during the last 3 months), with
   at least 5 of them being migraine days

   - Onset of migraine at age 50 years or younger

   - Agrees to refrain from initiating or changing any prophylactic medications for
   indications other than migraine

Key Exclusion Criteria:

   - Concomitant medical condition that will require oral or injectable steroids during the
   study

   - Currently on a stable regime of more than 1 migraine preventative therapy

   - Other significant pain problem (e.g., cancer pain, fibromyalgia, other head or facial
   pain disorder)

   - Known or suspected severe cardiac disease (e.g., symptomatic coronary artery disease,
   prior myocardial infarction, congestive heart failure)

   - Known or suspected cerebrovascular disease

   - Previous cervical vagotomy

   - Currently implanted with an electrical and/or neurostimulator device

   - Been implanted with metal cervical spine hardware or has a metallic implant near the
   nVNS stimulation site

   - Known history or suspicion of secondary headache

   - Currently using marijuana (including medical marijuana) or has used marijuana
   (including medical marijuana) or cannabidiol oil within the last 6 months

   - Currently takes simple analgesics or NSAIDs >15 days per month or triptans, ergots, or
   combined analgesics >10 days per month for headaches or other body pain

   - Currently takes prescription opioids more than 2 days per month for headaches or body
   pain

   - Failed an adequate trial (2 months or greater) of at least 3 classes of a drug therapy
   for migraine prevention

   - Surgery for migraine prevention

   - Undergone nerve block (occipital or other) in the head or neck within the last 3
   months

   - Received Botox or CGRP mAb injections within the last 6 months

   - Pregnant or thinking of becoming pregnant during the study period, or of childbearing
   years and unwilling to use an accepted form of birth control

   - Previously used gammaCore