6Detection 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.
|The pain starts at the eyebrow level or immediately below or above it|
|Doppler signal is often present in the most tender sites|
|There is strong corrugator muscle activity causing deep frown lines on animation and repose|
|The points of emergence of the supraorbital and supratrochlear nerves from corrugator muscle or the foramen are tender to the touch|
|Patients commonly have eyelid ptosis on the affected side at the time of active pain|
|Pressure on these sites may abort the MH during the initial stages|
|Application of cold or warm compresses on these sites often reduces or stops the pain|
|The pain is usually imploding in nature|
|Stress can often result in triggering MH|
|The pain starts in the temple area about 17 mm lateral and 6.5 mm cephalad to the lateral canthus|
|Patients usually wake up in the morning with pain having been clenching or grinding their teeth all night|
|Often the pain is associated with tenderness of the temporalis or masseteric muscle|
|One may see wearing of the dental facets|
|Rubbing or pressing the exit point of the zygomaticotemporal branch of the trigeminal nerve from the deep temporal fascia can stop or reduce the pain in the beginning|
|Application of cold or warm compresses to this point may reduce or stop the pain|
|The pain is characterized as imploding|
|Stress can trigger MH in this site|
|Doppler signal could be identified in this site|
|The pain starts behind the eye|
|Patient commonly wakes up with the pain in the morning or at night|
|Commonly the MHs are triggered by weather changes|
|Rhinorrhea can accompany the pain on the affected side|
|This type of MH can be related to nasal allergy episodes|
|Menstrual cycles can trigger MH|
|The pain is usually described as exploding|
|Concha bullosa, septal deviation with contact between the turbinates and the septum, septa bullosa, and Haller’s cell can be seen in the computed tomography|
|The pain starts at the point of exit of the greater occipital nerve from the semispinalis capitis muscle (3.5 cm caudal to the occipital tuberosity and 1.5 cm off the midline)|
|Doppler signal could be identified in the most tender spot|
|The patients may have a history of whiplash injury|
|The neck muscles are usually tight|
|Heavy exercise can trigger MH|
|Compression of this site can stop the pain in the early stage, while at the later stage, this point is tender|
|Application of cold or heat at this site may result in some improvement in the pain|
|Stress can be a major trigger for the occipital MH|
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.
6.5 Using the Fingertip
One of the most important aspects of detecting the trigger site is successful solicitation of patient cooperation in pointing to the headache commencement site with a fingertip. This could prove extremely easy in some patients and very challenging in others. It is crucial to be relentless. Repeated questioning could help in identifying and confirming this site. It is possible to entice even patients who do not have pain at the time of examination to find a tender point that is the likely site of the beginning of the MH. Another way to find this spot is to ask the patient to point to the site where they or their spouse or friends press on firmly to abort or mitigate the headache in the beginning of the migraine cascade. Pressure in the spot stops the blood flow through the vessel near the nerve that could be causing irritation of the nerve. Not every patient will reliably find this spot, but the overwhelming majority will do so. When the trigger site is identified, it is lightly marked to be explored with a Doppler probe.
6.6 Doppler Signal
One of the tools that have become exceptionally helpful in the detection of trigger sites is the ultrasound Doppler. We have discovered that patients who point to the MH site, especially those with nummular headaches, almost invariably have a Doppler signal at that site.2 It is fascinating that this signal can be so consistently identified if the patient can point to the migraine site precisely. Sometimes it is necessary to ask the patient to point to the area several times before detecting the Doppler signal. However, this Doppler signal can be commonly identified on the first attempt. Our anatomical dissections3–12 have demonstrated that, frequently, there is a vessel that is crossing the nerve or is intertwined with the nerve that is often the site of the start of MHs. The nerve/vessel interaction as the mechanism of peripheral irritation has been the subject of previous reports going back many decades.13 Our electron microscopy and proteomic study has demonstrated that patients with MH have a myelin deficiency.14 Whether this pulsation in the vessel next to a myelin-deficient nerve is the real trigger source of MH needs to be proven, but it seems to be a logical potential explanation.
To use the Doppler accurately, the patient is asked to point to the area of pain beginning with the index fingertip. The site is marked and the Doppler is utilized to detect a signal. It may be necessary to move the Doppler probe around to small extent to identify the vessel signal. A combination of the pain starting at a specific site that the patient can point to with an index finger and detection of a Doppler signal at that site is an extremely reliable and objective means of identifying the trigger site. The ultrasound Doppler is a handheld, low-cost device that has become an integral part of our migraine surgery practice for several years.
Our team has demonstrated that the auriculotemporal nerve intersects the superficial temporal artery in approximately 34% of examined specimens.15 While in most cases this is a single point crossover, this could also be a helical intertwining of the vessel with the nerve, although the latter relationship is more common with the occipital nerve than with the auriculotemporal nerve. The lesser occipital nerve can also cross over or under the occipital artery branches 55% of the time through a simple intersection.3 This crossover point can be commonly found 16 to 22 mm caudal to the external auditory canal and 51 mm lateral to the midline.
The ultrasound Doppler has also been an extremely valuable tool in identifying a secondary trigger site following decompression of the main trigger sites. These sites are along the course of the previously decompressed nerve but are often more peripheral than the main trigger sites, such as the vertex, upper forehead, lateral upper cervical area, and especially the temporal area. These commonly behave like nummular headaches. The site of the detectable temple trigger ultrasound Doppler signal could be at any point from near the origin of the ZTBTN to the area immediately above the ear and sometimes in the preauricular region (►Figs. 6.2–6.4). It is intriguing to see how often one can find a Doppler signal on these rare MH trigger sites.