What are Zones?
Zones represent the area associated with pain and the nerve or nerves within that area.
For instance the Surpraorbital nerve or Supratrochlear nerve seen below may be considered Zone 1 to some surgeons. Each surgeon may have his or her own zone configurations, zone 1 might be at the back of the neck for some surgeons. Often times the pain from a migraine will cross from one zone to another. Your surgeon may choose to address one or more zones at a time for surgery.
Part of the evaluation that helps determine surgical candidacy involves the identification of peripheral migraine trigger zones that are responsible for the triggering of some if not all of your migraine headaches. Fortunately only a minority (5-15%) of patients have central (i.e. within the central nervous system or brain) triggers which can be persistent and cannot be addressed through migraine surgery. Peripheral triggers involve irritation, compression, vibratory stimulation, or simply errant signal interpretation through primarily branches of the trigeminal nerve (cranial nerve #5) and or the greater occipital nerve.
The trigeminal nerve supplies sensation to the face, frontal scalp, nasal and ocular linings. The greater occipital nerve supplies sensation to the posterior scalp. Both of these nerves have a nucleus or “home base” nestled together in the hind brain just above the spinal cord where they also communicate with the brain’s pain relay station, an area referred to as “the migraine generator,” areas responsible for nausea, and other autonomic centers that control secretions and vasodilation in the nose, sinuses, eyes etc.
Proximal compression of the trigeminal nerve trunk as it exits the skull is often referred to as tic de Leroux and results in an extremely severe episodic pain, usually in the distribution of the upper two thirds of the face. It has been treated by neurosurgeons with what is called a “microvascular decompression” of the nerve with placement of padding between the freed nerve and the adjacent artery. This is a higher risk, much more involved surgery with similar principles to migraine surgery, but in an area closer to the brain with more critical structures exposed. These similar principles involve freeing a nerve from any compressive structures which can be a tight fiber, scar tissue, an artery, a muscle or even bone. The nerve is then often padded with fatty tissue.
Migraine surgery involves the decompression of several of the small terminal branches of the trigeminal and of the greater occipital nerves. When intranasal vibratory stimulation through the trigeminal nerve is felt to be a trigger, elimination of the vibration through opening of the nasal airway is performed.