The Food and Drug Administration (FDA) approved the use of a specific neurotoxin, onabotulinumtoxinA, as a preventive treatment for chronic migraine in 2010. This treatment is intended for individuals who experience chronic migraine, which is defined as having 15 or more headache days per month, with at least eight of those days meeting the criteria for migraine over a three-month period. The neurotoxin acts by blocking the release of pain-signaling chemicals, such as calcitonin gene-related peptide (CGRP), from peripheral sensory nerve endings in the head and neck. This mechanism helps to interrupt the pain transmission pathways that contribute to the frequency and severity of chronic migraine.
The treatment’s effectiveness relies on the precise injection of the neurotoxin into strategically chosen areas of the head, neck, and shoulders. Unlike cosmetic applications, the goal is not muscle paralysis for wrinkle reduction but rather the modulation of pain signals at the nerve level. The neurotoxin is absorbed by the sensory nerves distributed throughout the injected muscles, preventing the activation of pain networks in the brain.
The Standardized Injection Protocol
The standard method for administering the neurotoxin for chronic migraine is based on the Phase III Research Evaluating Migraine Prophylaxis Therapy, or PREEMPT, protocol. This standardized approach involves a total of 31 fixed injection sites across seven specific muscle groups in the head and neck. Each site receives a small, precise dose of the neurotoxin, typically five units, for a total dose of 155 units in the fixed-site approach.
The injection locations are carefully chosen to target the sensory nerve endings in muscles supplied by the trigeminal and cervical nerves, which are often overactive in chronic migraine. Injections are first administered into the corrugator and procerus muscles, which are located in the brow and between the eyebrows, respectively. The frontalis muscle, stretching across the forehead, is also a fixed injection area.
Moving laterally, the temporalis muscles, situated on the temples above each ear, receive several injections. The occipitalis muscles, found at the back of the head just above the neck, are targeted next to address posterior head pain. These injections are generally performed while the patient is in a supine or sitting position.
The protocol extends down the neck and into the upper back to cover the cervical paraspinal and trapezius muscle groups. The cervical paraspinal muscles are located on the back of the neck near the midline, while the trapezius muscles are the large muscles that extend across the upper shoulders and back of the neck. Targeting these muscles aims to reduce the transmission of pain signals and lessen tension that can contribute to headache.
Clinicians may administer additional injections, up to a total of 195 units, using a “follow-the-pain” approach. These extra injections are given to areas where the patient experiences the most significant pain, such as additional sites in the temporal, occipital, or trapezius muscles.
Preparing for the Procedure
The process begins with a consultation to confirm the diagnosis of chronic migraine, as the neurotoxin is not approved for episodic migraine. The physician will review the patient’s headache diary to assess the frequency and characteristics of their attacks.
Prior to the injection appointment, patients are advised to avoid consuming alcohol and using blood-thinning medications, such as aspirin or ibuprofen, for a few days. This precaution is taken to reduce the risk of bruising or bleeding at the numerous injection sites. Patients should also come to the appointment with clean skin, avoiding makeup, and those with long hair should secure it in a way that exposes the neck and back of the head.
The procedure itself takes about 10 to 15 minutes. The injections are administered using a very fine, small-gauge needle. Patients are often positioned sitting up or lying down to allow the physician access to all the necessary injection points.
While the needle pricks may cause brief stinging, the discomfort is generally well-tolerated. Some patients opt to apply a topical numbing cream to the injection areas 30 to 60 minutes before the procedure to minimize sensation. The neurotoxin is injected just beneath the skin or superficially into the muscles.
Treatment Frequency and Post-Injection Care
The treatment for chronic migraine is not a single-session cure but a scheduled, prophylactic regimen. To maintain the preventative effect, injections must be repeated at regular intervals. The recommended administration interval for the neurotoxin is typically every 12 weeks, or three months.
The effects of the neurotoxin wear off over time, so it often takes two or more treatment cycles before the full benefit of reduced headache days is experienced. Staying on schedule is important to prevent the return of severe, frequent migraine attacks.
Immediately following the procedure, patients can typically resume most daily activities. However, there are a few simple post-injection care instructions to follow for the first 24 hours. Patients should avoid rubbing or massaging the injection sites, as this could cause the neurotoxin to spread to unintended areas.
It is also advised to avoid strenuous exercise, intense heat, and hair-washing for the rest of the day to allow the medication to fully settle. Common, temporary side effects that may occur include mild neck pain, soreness at the injection sites, or a temporary headache. In rare instances, temporary drooping of an eyelid or eyebrow may occur, but this resolves as the neurotoxin wears off after several weeks.