Patients with chronic migraine for 10 years or fewer had better outcomes, suggesting that more prolonged compression may be associated with permanent, irreversible nerve injury.
PHILADELPHIA—Some patients with chronic migraine may benefit from surgical decompression of posterior sensory nerves, according to research presented at the 14th Congress of the International Headache Society. Among 53 chronic migraineurs who underwent the procedure, 72% converted from chronic to episodic migraine, which included a reduction in headache frequency and severity during a six-month follow-up. The surgical success rate was greatest among persons who had had chronic migraines for 10 years or fewer.
Surgical Decompression of Posterior Sensory Nerves
Pamela Blake, MD, Director of the Headache Center of Northwest, Memorial Hermann Northwest Hospital in Houston, and colleagues performed surgical decompression of sensory nerves of the posterior neck in patients who experienced severe, chronic headaches at least 15 days a month for a year.
Prior to surgery, patients reported that the headaches failed to respond adequately to at least three preventive medications as well as therapeutic nerve blocks, usually involving the greater and lesser occipital nerves. Conversion from chronic to episodic migraine was defined as achieving a greater than 50% reduction in overall headache burden.
“The majority of study patients had daily or near daily headaches for more than five years and had tried an average of seven medications,” Dr. Blake told Neurology Reviews. “The headaches were so severe that they affected function, often to or near the point of being on medical leave from work or school.”
Restoring Nerve Function
Nerve decompression for headache is similar to decompressing the median nerve to treat carpal tunnel syndrome or removing a herniated disc to reduce nerve pressure in a patient with radiculopathy, noted Dr. Blake. With chronic headache, however, the process is not as simple, she pointed out.
Superficial sensory nerves of the skull—the trigeminal nerve branches in the front of the head and the occipital nerves in the back—can be compressed by surrounding muscles or connective tissue. Removing the pressure allows the nerve to function normally again, if the process has not gone on so long that the nerve is irreversibly damaged, Dr. Blake pointed out.
Among study participants, entrapment of the occipital nerve was often observed within the semispinalis capitis muscle, along with thick connective tissue that was probably due to chronic pressure on the nerve. This constant pressure leads to inflammation that eventually thickens the connective tissue, causing even more nerve compression, according to Dr. Blake.
“The longer that a patient has migraines, the harder it becomes to treat,” said Dr. Blake. Study participants who reported having chronic migraines for fewer than 10 years achieved an 82% conversion rate, whereas those who had chronic migraines for more than 10 years had a 55% conversion rate.
Structural Differences May Be Congenital
“Our findings suggest that normal anatomic variants may predispose patients to chronification of their headaches, and that chronification of migraine may be an indication of peripheral afferent nerve involvement,” Dr. Blake and colleagues noted.
“The underlying anatomic aberration of the nerve running within the body of the semispinalis capitis is believed to be an embryologic anomaly, which was found in about 30% of cadavers and all study participants,” Dr. Blake commented. “There are clinical and anatomic connections yet to be explained between the mechanical processes we observe affecting the superficial nerves and involvement of the trigeminal system that is more reminiscent of migraine. For instance, even headaches that get better with nerve decompression sometimes respond to triptans and [occasionally are caused] by classic migraine triggers, such as menses, stress, and weather changes.
“More research is needed to understand these connections,” she added, “but the findings we have presented are compelling and present a low-risk treatment for a condition that can be disabling and ruin a person’s quality of life.”
—Rebecca K. Abma