6 Detection of Migraine Headache Trigger Sites
The patient is asked to keep a 1 month log of migraine headaches (MHs) recording the MH starting site, frequency, intensity, duration and the associated symptoms prior to the first visit.
During the first visit, the patient is asked to identify the most common and most intense MH sites which are confirmed by reviewing the log.
The constellation of symptoms related to each trigger site is reviewed to further validate the MH beginning site.
The patient is asked to point to the area of the most pain or tenderness using the tip of the index finger, especially if the patient is experiencing headaches at the time of examination.
If the patient can identify a specific site that is tender, it is marked and a Doppler signal is searched for.
A combination of the patient identifying the site of onset of MH, presence of site-specific constellation of symptoms and presence of a Doppler signal at the site of inception of pain or most tender point reliably identify the trigger site.
Elimination of pain after a nerve block with injection of 0.5 to 1 mL of ropivacaine (Naropin) in the identified or suspected trigger site can further confirm the trigger site.
Should the patient fail to identify the trigger site as a specific point and refer to a diffuse zone of active pain, the potentially involved nerve in that anatomical zone is blocked with injection 0.5 to 1 mL of ropivacaine (Naropin), if the patient has pain at the time of examination.
If the patient refers to a zone of inactive pain at the time of examination and is unable to identify a point of pain or tenderness, one must either rely on the constellation of symptoms or inject botulinum toxin A (BT-A), unless the headache starts from a retrobulbar site.
A paranasal computed tomography (CT) scan can be invaluable in assessing the MHs originating from the retrobulbar site.
The constellation of symptoms including retrobulbar pain, CT findings of contact points, concha bullosa, paradoxical curl, and/or Haller’s cell are diagnostic of rhinogenic trigger site.
A negative nerve block or lack of response to BT-A injection does not necessarily exclude MH in the suspected site since central sensitization and diffuse inflammation of the trigeminal nerve or the occipital nerve may prevent a meaningful response to a nerve block or injection of BT-A.
Injection of BT-A may not be effective on sites where MHs are the consequence of irritation of the nerve by intranasal contact points, a vessel, fascial band, or within a bony foramen.
It is essential to make sure the patients understand that while most will have complete elimination of migraine headache, for some, additional surgeries could be necessary to achieve a migraine-free state.
For the ease of communication, the migraine trigger sites have been assigned Latin numbers from I to VII.
Our substantial experience with migraine surgery has led us to the conclusion that the patients who experience incomplete response to the initial surgery often observe migraine headaches (MHs) arising from a site that was not detected during assessment for the initial surgery. While the patients may surmise that the surgery failed, often after further inquiry, they concur that the residual MHs are not emanating from the initial surgery sites. Most commonly, these are secondary MH trigger sites. 1 However, on rare occasions, the failure to respond is the consequence of incomplete primary surgery. Paying careful attention to the patients’ statements has helped us to improve our trigger site detection techniques over the last 17 years. In this chapter, we will review our current means of detection of the migraine trigger sites in detail (► Fig. 6.1).
6.2 Maintenance of Migraine Log
The patients are asked to keep a 1-month log of MHs while they are waiting to be seen. The logging period does not necessarily have to be exactly 1 month, but a 30-day log would offer the most valuable information. The goal of this log is to document the common trigger sites from which the MHs initiate, the intensity, frequency, and duration of MHs, and to assemble the symptoms associated with the MHs. These findings can then be compared to postoperative values. This logging technique avoids solely relying on patient recall. Most patients with MH are on a variety of medications that impair their memory and cognitive function and thus may not be able to accurately remember the information that is essential for detection of the trigger sites and the decision about the surgery site and overall patient candidacy for surgical treatment of MHs. This log will also document the associated symptoms and medications they consume each time they experience MH.
6.3 Identifying Migraine Starting Point
The most valuable piece of information that the patient can provide to the examiner is the site of onset of MHs. On the initial assessment of headache sites, the patients are often very vague about the migraine site and point to the area with the whole hand or with multiple fingers. It is paramount to elicit as much cooperation from the patient and to identify the trigger site as narrowly as possible. To that end, it is important to encourage the patient to use the index fingertip and point to the area where they may experience beginning of the pain or tenderness several times to assure consistency. Often the patients may resist the idea of having a point of pain or tenderness, but after emphasizing the importance of this information, one can almost invariably produce the intended results from the examination. Each patient may have multiple trigger sites and the initial step is to focus on the point from which the MHs commence most commonly and are most severe. After confidently detecting the most common trigger site, the next question will center on the second most common trigger site the MH arises independent of the first trigger site. Extension of pain from one site to another area is very common and it does not constitute a second trigger site. Through a step-by-step process and with persistence, one can identify each autonomous trigger site. The identified site is then marked lightly with a marker. There are rare patients who, despite perseverance, may not be able to identify a point of origin for their MH. Asking this group of patients to obtain a photograph while they are pointing to the area of the pain at the onset of MH in different times could prove very helpful. Again, it is extremely important to assure by repeated questioning that the observed MH in each site is an independent headache site, it is not the extension of the ache from another site, and headache can be present in each site without the other sites being painful.
6.4 Constellation of Symptoms
After the patient points to the area of pain, it is helpful to consider the constellation of symptoms that the patient is experiencing. Again, the most important piece of information that the patient can supply the examiner is the site of origin of the MH. However, the constellation of symptoms that aid in the detection of trigger sites is also very useful in confirming the triggers sites, especially on patients who cannot precisely identify the point of inception of headaches. The common collection of symptoms for all four main trigger sites is listed in ►Tables 6.1–6.4. This assemblage of symptoms is extremely reliable and often aids in the discovery of trigger sites, even in the absence of Doppler signal or failure of patient to point to the precise site of start of MH. However, the more information one garners, the more likely that all trigger sites will be detected and dealt with, resulting in a successful elimination of the MH, rather than improvement.
It is vital to realize that many of the symptoms can be shared between different trigger sites. Also, the pain from one site can extend to another site. It is of utmost importance to keep redirecting the patient’s attention to the origin of the pain and confirm the independence of the identified site.
Some findings are highly specific, such as pain starting from the eyebrow area with a prominent corrugator supercilii muscle group on patients with frontal MHs. Patients with temporal MHs arising from irritation of the zygomaticotemporal branch of the trigeminal nerve (ZTBTN) point to the hollowed area in the temple centered about 17 mm lateral and 6.5 mm cephalad to the lateral canthus. Pain lateral or posterior to this site could be related to the posterior branch of this nerve, or anterior branch of the auriculotemporal nerve, or even a branch of the zygomaticfacial nerve. Patients with zygomticotermporal nerve trigger site commonly report nightly tooth grinding or clenching and wake up in the morning with pain in this site. Patients with rhinogenic trigger sites will have pain starting from behind the eyes, almost always associated with weather changes, and commonly wake up in the middle of night or in the morning with headaches. Orgasm- or menstrual-related MHs are commonly experienced in this site. It is interesting to note that all of these conditions that trigger rhinogenic MHs cause enlargement of the turbinates through hormonal, atmospheric, or postural changes. The increase in the size of the turbinates may intensify the contact between the structures inside the nose. Occipital MHs related to the greater occipital nerve commonly begin close to the midline or within 5 cm of the midline of the occipital region, at least 2.5 cm above the occipital hairline and extend more cephalically in a vertical and lateral fashion.
The lesser occipital MHs are closer to the hairline and more lateral to the greater occipital nerve territory, and often extend to the top of the ear or temple. The patients with occipital MH or neuralgia commonly have a history of whiplash injury.