In Part I of this blog, we talked about the first published report, in 1992, that stated that compression of the occipital nerves in the posterior neck could cause chronic head and neck pain, and that surgical removal of pressure from the nerves in a surgical procedure called ‘decompression’ could provide relief. Work in this field paused for many years after 1992, likely due to the success of new medications used for the treatment of headache in reducing patients’ suffering. It was by serendipity that in 2000 Dr. Bahman Guyuron, a plastic surgeon practicing at that time at Case Western University in Ohio, was able to revisit the role of compression of superficial nerves of the skull in headaches. Dr. Guyuron published in that year his observation that surgical removal of muscles called the corrugators – muscles that furrow the brow and cause dreaded frown lines – resulted in a reduction of headaches in 80% of patients who had undergone that cosmetic procedure. Link to article The resolution of headaches lasted for an average of almost four years at the time of publication. This finding, involving the muscles in the front of the face, mirrored the results of the doctors in Norway – that removal of pressure from superficial nerves in the back of the neck – could reduce – sometimes significantly – refractory or episodic headaches.
Progress in the field of nerve decompression for chronic headaches continued and moved ahead by a group of dedicated plastic surgeons, spearheaded by Dr. Guyuron. Their work was impressive as they detailed the anatomy of the relevant nerves in cadavers, catalogued the various possible sites of anatomic compression of nerves in both the back and the front of the head, described various surgical techniques to provide thorough decompression of the nerves, and ultimately formed a professional society called the Migraine Surgery Society (MSS), which is dedicated, as the website states, ‘to advance the understanding, diagnosis and treatment of headaches that can be treated with nerve compression.’ Migraine Surgery Society
A dilemma that arose, however, was that the research and work of the surgeons was published in the plastic surgery literature, however, and was generally not seen or read by practitioners of headache medicine. Incidentally, in the early 2000s, while the plastic surgeons were busy working on the above research, headache medicine physicians were also busy, formalizing and standardizing the process for a physician to become a board-certified Headache Medicine subspecialist. The field was formally recognized as a subspecialty with board certification through the United Council of Neurological Subspecialties UCNS in 2004.
The lack of contact and communication between Headache Medicine specialists and plastic surgeons created a bidirectional problem…Headache Medicine specialists were largely unaware of the anatomic findings and surgical techniques that were being described by the plastic surgeons, as well as even the possible mechanism of nerve compression as a cause of refractory headache, and the plastic surgeons had little opportunity to work with neurologists who could identify those patients whose headaches were due to nerve compression. This siloing of subspecialties may thus have unwittingly furthered the distance between them.
Interestingly, however, headache medicine research was underway in the early 2000s that supported the concept that nerves on the outside of the head could cause headaches that look like migraine. It may be helpful at this point to clarify exactly what the term ‘migraine’ means. ‘Migraine’ is diagnosed if a patient’s headaches meet the criteria of the International Classification of Headache Disorders (ICHD-3), the classification system of the International Headache Society that is used globally to ensure uniformity of headache diagnosis. As with all other conditions in the ICHD, the diagnostic criteria of the ICHD are based on symptoms, not the mechanism, meaning cause, of the headaches. A migraine without aura (visual and other neurological symptoms that accompany a migraine, beyond the scope of this article) is a headache that:
- has occurred on at least five occasions
- lasted 4-72 hours if untreated or unsuccessfully treated
- having at least two of the following four characteristics:
- unilateral pain (on one side of the head)
- pulsating quality
- moderate-severe intensity
- aggravated by, or causing avoidance of, routine physical activity such as walking or climbing stairs
- associated with one of the following:
- nausea and/or vomiting
- sensitivity to lights or sounds
We know from several large epidemiologic studies that migraine typically occurs four or fewer times per month. They are typically triggered by factors such as emotional distress, hormonal fluctuation, missing a meal or inadequate sleep, among other triggers. Most migraine pain is in the forehead and temple area and the front part of the eye. Migraines typically respond well to medications taken to stop the headache, providing the sufferer relief; the sufferer will then be pain-free until the next attack is triggered. The current understanding of migraine among headache medicine specialists is that the condition is caused by an overly-sensitive brain (which is usually due at least in part to genetic factors) which responds to an environmental trigger occurring either outside of or inside of the individual (e. g. strong chemical smells or intense emotional distress) that the nervous system regards as posing a threat. The nervous system, in an effort to alert the individual, causes an activation of complex systems in the brain and alterations in level of messenger molecules in the brain that ultimately result in activation of the trigeminovascular system, which involves the trigeminal nerve, a large nerve that emerges from the lower part of the brain, supplying the eye, face, and front part of the head. Thus, the pain of migraine is typically felt in the distribution of the nerve, in the forehead and front part of the eye and temple.
It was typically accepted, prior to 2000, that migraines were always due to these mechanisms involving the brain. Many headache medicine specialists today continue to be of the opinion that only factors involving the brain can be a trigger for migraine, and that factors outside of the brain, and particularly outside of the skull, are not important for migraine. However, in 2009, an eminent headache medicine researcher named Dr. Rami Burstein published new data that provided an explanation for how factors on the outside of the head may, indeed, be related to conditions on the inside of the head. Dr. Burstein and colleagues at Harvard determined through remarkable basic science research on mice that nerves on the inside of the head – branches of the trigeminal nerves that we discussed above – passed through the skull and emerged on the outside of the head. Link to article Dr. Burstein proposed that these trigeminal nerve branches ‘may be positioned to mediate migraine headaches triggered by pathophysiology of extracranial tissues.’ Similar anatomy in humans was described in 2014 Link to article leading the researchers to conclude that ‘the finding of extracranial projections of meningeal afferents may be important for our understanding of extracranial impacts on headache generation and therapy.’
This new anatomic information thus provided an anatomic pathway for conditions on the outside of the head to result in changes on the inside of the head, and this information aligns with the findings of the plastic surgeon that compression of nerves on the outside of the head could indeed play a role in the generation of head pain that may look just like migraine.
We will continue this conversation in Part 3.
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