10.3 Is Migraine Surgery the Right Term for Frontal Decompression Surgery

Before we go into the details regarding the surgery and its possible effects, we have to know exactly which headache disorder we intend to treat. Because headaches comprise such a heterogenic group of disorders, it is advisable to adhere closely to the International Classification of Headache Disorders (ICHD 3-Beta is the most up to date). The ICHD 3-Beta classifies headaches into major groups, types, subtypes, and subforms following explicit diagnostic criteria [11]. A list of specific diagnostic criteria (ICHD 3-Beta) for each of the major headache groups is shown in Table 10.2.

Table 10.2

International classification of headache disorders 3-beta [11]

Adapted from: Filipović B, de Ru JA, van de Langenberg R, Borggreven PA, Lacković Z, Lohuis PJFM. Decompression endoscopic surgery for frontal secondary headache attributed to supraorbital and supratrochlear nerve entrapment: a comprehensive review. Eur Arch Otorhinolaryngol. 2017;274:2093–2106. doi: https://​doi.​org/​10.​1007/​s00405-017-4450-x

In our practice, candidates for decompression surgery suffer from frequently occurring frontal headache (>15 days per month), with severe pain (visual analog score 7–10), described as a frontally localized pressure or tension, which is often accompanied by photophobia and sometimes by nausea. If we adhere to the ICHD 3-Beta, these frontal headaches should be classified as secondary headaches as we anticipate the underlying cause to be the entrapment of the supraorbital and supratrochlear nerves. When we further evaluate the headache symptoms of our patients, they often seem to mimic chronic migraine or chronic tension-type headache.

It is our opinion, when referring to the criteria of ICHD 3-Beta, that migraine surgery is not the ideal term as it implicates that surgery would alleviate the cause of a primary headache—migraine. This creates unnecessary disagreement between neurologists and surgeons because by following diagnostic criteria (Table 10.2) per definition, the specific underlying cause in primary headaches cannot be determined.

Therefore, we recently propose a new subclass of headache: frontal secondary headache attributed to supraorbital and supratrochlear nerve entrapment. In addition, we believe that a more appropriate term for the surgical procedures related to this type of headache would be as follows: “decompression surgery for frontal secondary headache attributed to supraorbital and supratrochlear nerve entrapment” [12].

10.4 Screening Algorithm: Which Patients with Frontal Headache Are Good Candidates for Decompression Surgery?

A screening algorithm was developed by our group (Fig. 10.2) to help identify those patients with frontal secondary headaches that have the highest chance for a successful surgical treatment outcome. Similar algorithms have been described by other authors [13, 14]. Some authors reported that also simple clinical signs (applied pressure in the area of the nerves inducing higher pain intensity) could be used to identify patients suitable for surgery [15, 16]. In some clinics, questionnaires facilitate the screening process [11].

Our screening algorithm includes both clinical (1 and 2) and pharmacological (3) elements. To properly identify the patients for surgery, each step in the algorithm is to be completed in the following order (Fig. 10.2):

1. 1.
   
   
   

   ICHD 3-Beta criteria for secondary headache

   
   

   Patients with frontally localized headaches are referred by different specialists (primary care physicians, neurologists, anesthesiologists, etc.) to be evaluated by the team member who is a specialist with experience in headache disorders. He takes patient history, performs physical examination, and fills questionnaires (scales and scores) for validation of headache symptoms and characteristics. Pain should be moderate to severe in intensity (VAS score 7–10), frontally located (>15 days per month), described as pressure or tension that intensifies with applied pressure on the area of supratrochlear and supraorbital nerves. Candidates for decompression surgery can only be those patients having headache that fulfills the ICHD 3-Beta criteria for frontal secondary headache [12], which mimic chronic migraine or chronic tension-type headache.

   
   
    
   
   
2. 2.
   
   
   

   CT scan

   
   

   CT scan of the head and neck should be routinely performed in previously selected patients in order to exclude secondary pathology (frontal sinusitis, concha bullosa, contact point spine, etc.) that can cause pain sensation in the frontal area.

   
   
    
   
   
3. 3.
   
   
   

   Pharmacological screening
   

   
   

   
   
   1. (a)
      
      
      

      Testing with local anesthetic (LA)

      
      

      Pain reduction after application of LA is regarded as evidence of a peripheral origin of the pain. As a first diagnostic tool, a local anesthetic such as Xylocaine (lidocaine 2%, adrenaline 1:80,000) can be injected around the exit points of the STN and SON at the supraorbital rim. By acting on voltage-gated sodium channels of the entrapped peripheral sensory nerves, LA directly decreases peripheral firing, resulting in decreased pain symptoms [17]. Pain should decrease to at least half of the initial VAS headache score.

      
      
       
      
      
   2. (b)
      
      
      

      Testing with BoNT/A

      
      

      Patients with pain reduction after LA injections may receive additional BoNT/A (approximately 15 IU Botox^®, Allergan, USA) injections into the corrugator muscle on both sides, in at least two sessions [16]. BoNT/A-mediated cleavage of SNAP 25 (complex that is responsible for Ca²⁺-dependent exocytosis) in motor nerves leads to prevention of acetylcholine release resulting in a reversible neuromuscular paralysis [18]. This action is only resolving entrapment of STN and SON caused by the constriction of muscles. Pain should decrease to at least half of the initial VAS headache score. With this information, we can suspect the leading cause of headache to be neural entrapment (muscle) in the trigger area [13]. The effect of BoNT/A on headache can last for several months [19], after which it can be repeated if necessary. Subsequently, patients should be given an option to continue with the BoNT/A therapy or to proceed with the decompression surgery (Fig. 10.1).

      
      
       
   
   
    

In conclusion, according to our algorithm (Fig. 10.2), patients suitable for decompression surgery are those with a headache that fulfills the ICHD 3-Beta criteria for secondary headache, with high pain scores (VAS 7–10) and refractory to any prior pharmacological treatment. To elucidate the cause of frontal secondary headache (supraorbital and supratrochlear nerve entrapment), both CT scan and injections of LA and BoNT/A should be performed.

10.5 Headache Anatomy

Muscular entrapment points related to the corrugator muscle were identified with different branching patterns of the STN and SON, running either underneath the muscle or through the muscle [3–5].

The SON and STN separately exit the orbit (STN more medially) through either bony passages (foramina) or bony-periosteal elevations (notch) structures which are positioned at the supraorbital ridge (Fig. 10.3) [5, 20]. The supraorbital foramen, a bony opening at the supraorbital ridge, completely circulates the nerve resulting in a higher possibility of a bony entrapment. If a notch is found, this also results in a higher chance for periosteal encirclement or entrapment of the nerve since the floor of the notch contains fascial bands (remnants of the periosteum) which are connected to the roof of the notch (supraorbital ridge) (Fig. 10.3).

10.6 Surgical Technique: Endoscopic Approach

Based on the anatomical studies, the goal of decompression surgery in the frontal region is to release muscular, periosteal, and bony entrapment of the SON and STN. To achieve this goal, two surgical approaches where introduced: the endoscopic approach [8, 10, 21, 22] and the open-transpalpebral approach [2, 6, 7, 9].

Nowadays, for our group, the state of the art is the endoscopic approach as it allows complete release of the periosteum at the level of supraorbital ridge, while at the same time the entire glabellar muscle group can be dissected. Some authors believe that muscle de-entrapment can only be achieved by complete excision of the glabellar muscle group. By employing endoscopic approach in our practice, we found that blunt dissection of the muscles (without excision) in combination with periosteum release is a sufficient maneuver to achieve an adequate level of decompression indicating that the periosteal entrapment is most likely the leading causative factor. Additionally, by blunt dissection of the glabellar muscles, the chance of more serious adverse effects of the surgery is decreased.

The open-transpalpebral approach can be regarded as an extension of an upper blepharoplasty procedure. After opening the skin and visualization of the muscles and nerves, decompression is achieved by complete excision of the glabellar muscles, while the periosteum and fascial bands of the supraorbital ridge are left intact. In line with that, Liu et al. (2012) showed that endoscopic approach has better treatment outcomes compared to the transpalpebral approach, and it was advocated that it should be used as the approach of first choice whenever it is anatomically feasible [21].

Some authors discussed the need to additionally perform a supraorbital bony foraminotomy in patients with high pain sensation at the supraorbital foramina. The procedure involves percutaneous release of the supraorbital foramina roof using a guarded 2 mm osteotome. In their opinion, this ensures complete bony release of the SON resulting in improved treatment outcome [23]. However, in our practice, we have not found the need to perform this procedure up to now. Adequate release of the supraorbital ridge periosteum and blunt dissection of the glabellar muscle group by the endoscopic approach are sufficient in almost all our cases.

All of our patients are operated under general anesthesia. Prior to the skin incision, the forehead is injected with xylocaine to minimize the bleeding in the operating field. A pre-hairline incision (W shape, 12 mm long) is made in the midline with a 15-blade scalpel. Although a second skin incision can be made laterally to the midline in order to allow an extra surgical instrument, we have not found it necessary in most cases (Fig. 10.6).

Under direct control of the endoscope, the Obwegeser periosteal elevator is used to elevate skin–muscle–periosteum flap in a subperiosteal plane. Dissection is carried caudally in the medial line until the supraorbital rims are visualized at which level the periosteum is incised. We do not remove any of the glabellar muscles. Instead, we use the elevator for blunt dissection of the muscles through the periosteal incision, until both STN and SON and accompanying vessels are well visualized. This procedure is safe and in our hands has been proved to be efficient to achieve the necessary level of muscle and periosteum de-entrapment of the SON and STN finally resulting in satisfactory postoperative frontal pain relief. Surgery is finished with homeostasis and stapling of the skin incision. Dressings with bandage are placed around the forehead for 1 day. Parts of the endoscopic procedure are shown in Fig. 10.7a, b.

10.7 Surgical Outcome

Evidence about the efficacy of surgical treatment for frontal secondary headache is accumulating rapidly as different surgical groups are continuously reporting their results. Apparently, the surgery has a long-lasting effect [6–10]. In these studies, outcome was measured by the percentage of patients who experienced late postoperative reduction of headache symptoms of 50% or more on a VAS (0–10). Surgical success rates from the early publication to the latest published study have improved from 68.3% [6] to 93.3% [10].

It is important to emphasize, as headache can emerge from other head regions (temporal and occipital) [24, 25], that some authors implicate the need to operate these regions simultaneously with the frontal region to achieve better outcomes [26]. However, the frontal region is the single most frequently operated site with the highest success rate reported by some studies with a level 2 of clinical evidence (Table 10.1) [6–10]. Also, in our practice, the patients most often have frontally localized headache, while other regions are far less presented. We believe that a potential successful outcome of surgery depends highly on the precise preoperative patient selection by using a screening algorithm (Fig. 10.2).

10.8 Adverse Effect

Every treatment modality for headache has adverse effects. Reported adverse effects of decompression surgery in the literature primarily include transient paresthesia of the surgical field, hematoma formation, and brow asymmetry (Table 10.1). In our practice, we find decompression surgery of the frontal region to be one of the safest procedures, while the only observed adverse effects have been transient paresthesia (duration of 1–2 months, from the hairline to the orbital rims) and postoperative swelling around the orbit. Although the bleeding in the surgical field is a possible intraoperative complication, occurring especially around the nerves, it can be avoided by blunt dissection and easily resolved with appropriate surgical instruments (Fig. 10.5). Our patients are routinely discharged from the hospital on their first postoperative day.

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