**3. Diagnosis of chronic migraines and candidacy for onabotulinumtoxinA**

Prior to being treated for migraine headaches by BTX-A injection, it is critical for the patient to be seen by a board-certified neurologist, preferably one who specializes in headache medicine. If the neurologist does not offer BTX-A injection, collaboration with other specialties such as plastic surgery, ENT, or pain management for the injections can be done. A multidisciplinary team approach with plastic surgery, neurology, psychiatry, sleep medicine, and pain management working in conjunction with each other is an effective and preferred approach. The neurologist should evaluate and confirm the diagnosis of chronic migraine headache, ruling out other likely causes of recurring headaches that may not respond to BTX-A injection. Results from the PREEMPT part 1 and part 2 trials established BTX-A as safe and effective for chronic migraine patients. However, BTX-A should be avoided in patients who have previous hypersensitivity reactions to the toxin. Other contraindications include pre-existing neuromuscular disorders (myasthenia gravis and Lambert-Eaton syndrome), peripheral motor neuropathies, and amyotrophic lateral sclerosis that can increase the risk of significant side effects. It is unclear how effective BTX-A is in treating other commonly seen headache types, such as cluster, tension, and episodic headaches, as results have been mixed [15–17, 28–30]. Lastly, the majority of insurance carriers in the United States require documentation of migraine and headaches days, and previous failure of several classes of migraine medications.
