Abstract
Background:
The temporalis muscle is commonly dissected and mobilized during craniotomy. Cosmetic and functional complications may arise from the improper handling of this muscle. Surgery for recurrent pathologies may be challenging due to adhesions and muscle damage.
Material and methods:
A systematic review following PRISMA guidelines was conducted to consolidate literature on the potential techniques used for preserving the temporalis muscle during neurosurgical interventions. PubMed, Scopus, and Web of Science were systematically searched using predefined criteria from inception to 2025. A qualitative synthesis was done summarizing the primary cranial pathology, type of surgical approach, the technical clue for temporalis muscle preservation, follow up and complications.
Results:
We included 27 eligible articles with a total number of 811 patients. About 508 (62.6%) of patients underwent pterional approach, while 150 (18.4%) patients had decompressive craniotomies. Aneurysm clipping was the surgical indication in 172 (21.2%) patients, while decompressive surgery was done for traumatic brain injuries in about 48 (5.9%) patients. Osteoplastic temporalis muscle flap was used in 178 (21.9%) patients, while some authors sutured the temporalis muscle to the cranioplasty plate in 79 (9.7%) patients. Fixation of the temporalis muscle to the bone using sutures through small holes was done in 100 (12.33%) patients. No chewing problems were recorded among all the patients analyzed. Temporalis muscle atrophy was observed in only 13 (1.6%) patients.
Conclusion:
Proper manipulation of the temporalis muscle during surgery is crucial for the vitality of its fibers and to prevent postoperative functional or cosmetic drawbacks.
Keywords: cosmetic, decompressive craniotomy, pterional, temporalis muscle
Introduction
Pterional craniotomy and its modifications provide adequate surgical exposure for approaching several skull base lesions. Dissecting and mobilizing the temporalis muscle is a common neurosurgical maneuver encountered in pterional surgery. In 1984, Yasargil described the pterional approach and the subgaleal dissection was used for mobilization of the temporalis muscle[1].
HIGHLIGHTS
Dissecting and mobilizing the temporalis muscle during craniotomy is a common neurosurgical maneuver.
Pterional craniotomy and its modifications are widely used for neurosurgical exposure.
Certain cosmetic and functional problems could result from temporalis muscle dissection.
There are possible technical suggestions that could prevent the temporalis muscle from atrophy.
Proper reconstruction of the muscle with adequate reaproximation is a way to preserve muscle fiber integrity.
The use of anti-adhesion methods during decompressive craniotomy may facilitate the process of dissection.
Several problems resulted from the surgical mobilization of the temporalis muscle as a step of pterional craniotomy. Temporal asymmetry, muscle atrophy, chewing disorders could follow muscular atrophy. The main etiology is unclear, and the most possible mechanisms include interruption of the vascular and nerve supply of the temporalis muscle or disrupting the temporalis fat pad or improper reconstruction of the temporalis muscle[2,3]. The related functional and cosmetic complications are always overlooked and underreported.
A number of techniques have been proposed for preservation of the integrity, structure and function of the temporalis muscle during surgery. Cosmetic surgery is becoming a more popular way to correct temporal hollowing[4]. However, despite various proposed strategies, there remains a lack of consensus on the most effective approach to mitigate temporalis muscle atrophy following craniotomies. The variability in surgical techniques, differences in patient outcomes, and the absence of standardized guidelines highlight the need for a comprehensive synthesis of available evidence. The present study aims to conduct a systematic review, focusing on the possible ways to mitigate temporalis muscle atrophy following craniotomies. By synthesizing existing evidence from a multitude of studies, this research endeavors to provide possible surgical techniques that could improve the cosmetic outcome related to temporalis muscle mobilization.
Materials and methods
This review thoroughly identified pertinent research on potential techniques to protect the temporalis muscle during neurosurgical procedures. We carried out a systematic review in accordance with the recommendations given in the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) framework[5] to guarantee a methodical and thorough evaluation.
Search strategy
To find pertinent publications, the PubMed, Scopus, and Web of Science databases were thoroughly searched. The analysis did not include anatomy studies, cadaveric studies, animal studies, or studies published in non-English languages. The inclusion criteria were rigorously derived from research that supplied all relevant information. The search strategy involved conducting a thorough literature search using specific keywords, and other terms relevant to the topic, including “temporalis muscle preservation,” “temporalis muscle hollowing,” “temporalis muscle anchoring,” “temporalis muscle atrophy” “pterional approaches” “decompressive craniotomy/craniectomy” “hemicraniectomy,” “hemicraniotomy,” “cranial osteoplastic flaps,” “temporalis muscle and cranioplasty,” “cranioplasty.”
In the first screening, titles and abstracts were reviewed to find pertinent papers and remove duplicates. After that, two authors separately carried out a thorough investigation to settle any disagreements and guarantee a conclusive analysis. The potential ways for preservation of temporalis muscle integrity were the main topic of the gathered data.
Eligibility criteria
We included studies with the following criteria: (1) Adult or pediatric patients undergoing neurosurgical procedures involving the temporalis muscle. (2) Studies describing or comparing temporalis muscle preservation techniques. (3) Studies reporting on at least one relevant clinical outcome (e.g., temporalis muscle atrophy, temporal hollowing, functional deficits, or complications). (4) Randomized controlled trials, cohort studies (prospective or retrospective), technical notes, case reports and case series. (5) Studies published in English. (6) No restrictions on publication dates were made. We excluded narrative reviews, commentaries, editorials, and abstracts without full text. We also excluded studies not published in English.
Level of evidence and quality assessment
Most of the included studies were technical notes, case series, and case reports, with a smaller proportion being retrospective cohort studies. According to established evidence hierarchies, retrospective cohort studies are typically categorized as Level III–IV, whereas technical notes, case series, and case reports are categorized as Level IV–V. While these studies provide valuable insights into surgical techniques and clinical outcomes, they lack the methodological robustness of randomized controlled trials or prospective cohort studies due to factors such as the absence of randomization, control groups, small sample sizes, and potential for selection bias. We used the following tool to assess the evidence of the included studies:
Retrospective cohort studies: The Newcastle–Ottawa scale (NOS) was utilized to evaluate the quality of these studies, focusing on domains such as selection, comparability, and outcome assessment.
Case reports/case series: The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Case Reports or Case Series was used to evaluate methodological quality, including criteria such as clear descriptions of patient demographics, interventions, outcomes, and follow-up.
Technical notes: A descriptive appraisal was conducted to assess clarity and reproducibility of the surgical technique, as well as any reported clinical outcomes or complications.
Data extraction
The data was retrieved and arranged in an extensive excel document that included information extracted from each study. The extracted data included age, sex, primary cranial pathology, type of surgical approach, the technical clue for temporalis muscle preservation, follow up and complications.
Data synthesis
A qualitative synthesis was performed to summarize the findings on the primary cranial pathology, type of surgical approach, the technical clue for temporalis muscle preservation, follow up and complications. Due to the predominance of technical notes, case series and retrospective cohort studies, no meta-analysis was conducted.
Results
Study selection
Our search initially identified 586 studies. After screening titles and abstracts, 170 studies qualified for full-text review. Of these, 27 studies involving a total of 811 patients met the inclusion criteria and were incorporated into our systematic review (Fig. 1).
Figure 1.
The PRISMA flowchart.
Descriptive analysis of the included studies
A total of 27 studies including 811 patients who underwent neurosurgical operations with temporalis muscle preservation techniques were included. Fifteen studies were technical notes, 5 were case series, 4 retrospective cohort studies, and 3 case reports. Male patients accounted for 53% (177/334). About 508 (62.6%) of patients underwent pterional approach, while 150 (18.4%) patients had decompressive craniotomy. Aneurysm clipping was the surgical indication in 172 (21.2%) patients, while decompressive surgery was done for traumatic brain injuries in about 48 (5.9%) patients, surgery was done for multiple other pathologies in 205 (25.27%) patients. Osteoplastic temporalis muscle flap was used in 178 (21.9%) patients, while some authors sutured the temporalis muscle to the cranioplasty plate in 79 (9.7%) patients. Fixation of the temporalis muscle to the bone using sutures through small holes was done in 100 (12.33%) patients. Other different techniques are listed in Table 1. No chewing problems were recorded among all the patients analyzed. Temporalis muscle atrophy was observed in only 13 (1.6%) patients.
Table 1.
List of studies and techniques for temporalis muscle preservation
| Study | Study design | Patients number | Age | Sex (M/F) | Primary cranial pathology | Neurosurgical approach | Technical preservation method | Follow-up |
|---|---|---|---|---|---|---|---|---|
| Zhang et al [6] | Retrospective cohort | 23 | 35–77 Y | 5/18 | Aneurysm | Pterional surgical approach | A small temporalis muscle incision for a focused sylvian approach | 3 |
| Jiao et al [7] | Case report | 1 | 65 Y | 1/0 | Moyamoya | Cranioplasty | Suturing temporalis muscle to the cranioplasty mesh | NM |
| Figueroa-Sanchez et al [8] | Retrospective case series | 8 | 36–88 Y | 6/2 | 7 Stroke, 1 TBI | Frontotemporoparietal | Suturing temporalis muscle to the cranioplasty mesh | 1–8 |
| Sangrador-Deitos et al [9] | Retrospective case series | 108 | NM | NM | Multiple pathologies | Pterional surgical approach | Subgaleal pre-interfascial dissection | 6 |
| Varol et al [10] | Retrospective cohort | 52 | NM | 32/20 | NM | Pterional surgical approach | Osteoplastic temporalis flap | 6 |
| Wang et al [11] | Technical note | 7 | 35–50 Y | 4/3 | Multiple pathologies | Decompressive | Temporalis muscle wrapping to separate it from the dura | 2–3 |
| Rai et al [12] | Technical note | 50 | 26–81 Y | 29/21 | Aneurysm | Pterional surgical approach | Antegrade, subfascial, subperiosteal elevation, and posterior rotation of temporalis muscle without incising in its bulk | 6 |
| Tsunoda et al [13] | Retrospective cohort | 33 | 45–87 Y | 10/29 | Aneurysm | Pterional surgical approach | Skin incision that went slightly posterior to the parietal branch of STA | 6–24 |
| Pulling the temporalis muscle posterior caudally preserve the frontal periosteum medial to the linear temporalis when reflecting the muscle skin flap | ||||||||
| Soto et al [14] | Technical note | 7 | 2 m–78 Y | 4/3 | TBI | Decompressive | Modified hemicraniectomy technique (placing the inferior aspect of the incision posterior to the ear) | NM |
| Choque-Velasquez et al [15] | Case report | 34 | NM | NM | Stroke | Decompressive | Preservation of the STA | NM |
| Avoid incising the preauricular temporalis muscle | ||||||||
| Adeleye et al [16] | Retrospective case series | 40 | NM | 38/2 | TBI | Decompressive | Osteoplastic flap | 1–31 |
| Di Rienzo et al [17] | Retrospective case series | 30 | NM | NM | Multiple pathologies | Decompressive | Temporalis muscle wrapping to separate it from the dura | NM |
| Missori et al [18] | Technical note | 21 | NM | NM | Multiple pathologies | Decompressive | Through a three-leaf clover flap skin incision, the temporal muscle was detached en-block and overturned anteroinferiorly conjoined with the frontal myocutaneous flap | 12 |
| McLaughlin et al [19] | Case report | NM | NM | NM | Aneurysm | Pterional surgical approach | The deep temporal fascia and temporal muscle are incised vertically, completing a T-shaped incision so the muscle is not completely dissected from the temporal fossa. | NM |
| Subperiosteal dissection | ||||||||
| Matsumoto et al [20] | Technical note | 40 | NM | NM | NM | Pterional surgical approach | Osteoplastic temporalis flap | 12 |
| Sharma et al [21] | Technical note | 44 | NM | NM | NM | Cranioplasty | Suturing temporalis muscle to the cranioplasty mesh | NM |
| Kim et al [22] | Technical note | 40 | NM | 12/28 | Aneurysm | Pterional surgical approach | Osteoplastic bone flap | 6 |
| Miller et al [23] | Retrospective case series | 6 | 1–15 Y | NM | Multiple pathologies | Pterional surgical approach | Osteoplastic bone flap | 5–22 |
| Missori et al [24] | Technical note | 11 | NM | 10/1 | Multiple pathologies | Decompressive | Temporalis muscle wrapping to separate it from the dura | NM |
| Bowles et al [25] | Technical note | 100 | NM | NM | Multiple pathologies | Pterional surgical approach | Temporalis muscle reattachment to the bone through bone holes passing sutures | NM |
| Zager et al [26] | Technical note | NM | NM | NM | NM | Pterional surgical approach | Temporalis muscle microfixation to the bone using screws | NM |
| Horimoto et al [27] | Technical note | NM | NM | NM | NM | Frontotemporoparietal | Subfascial temporalis muscle dissection | NM |
| Park et al [28] | Retrospective cohort | 26 | 57–66 Y | 10/16 | Aneurysm | Pterional surgical approach | Contourable strut plate (CSP) is fashioned into the contour of the temporal line of the frontal bone and fixed to the temporal line using two screws then the edge of the temporalis fascia and muscle is sutured and fixed to the CSP | 10 |
| Oikawa et al [4] | Technical note | 100 | NM | NM | NM | NM | Retrograde subperiosteal dissection | 72 |
| Hönig et al [29] | Technical note | NM | NM | NM | NM | NM | Temporalis muscle reattachment to the bone through bone holes passing sutures | NM |
| Brunori et al [30] | Technical note | NM | NM | NM | NM | NM | Temporalis muscle reattachment to the bone through bone holes passing sutures | NM |
| Rai et al [12] | Technical note | 30 | 12–65 Y | 16/14 | Multiple pathologies | Pterional surgical approach | Suturing the free edge of the temporalis muscle to the reflected fascial layer exactly along the superior temporal line, proceeding from anteriorly to posteriorly | 6 |
M: male, F: female, NM: not measured, STA: superficial temporal artery, TBI: traumatic brain injury
Risk of bias assessment
Two independent authors did the quality assessment KS and MA. Any discrepancies were resolved through discussion or consultation with a third reviewer to ensure consistency and objectivity. Regarding the four retrospective cohort studies, they were all rated as good quality based on the NOS, with strengths in clearly defined patient selection criteria and outcome assessment but limitations in comparability due to the lack of adjustment for confounding variables (Table 2). The five case series (Table 3) and the three case reports (Table 4) were evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist demonstrated adequate reporting of patient demographics, interventions, and outcomes in most studies, but follow-up duration and completeness of outcome data were inconsistently reported. The 15 technical notes were generally well-documented, providing clear descriptions of surgical techniques and their reproducibility; however, few reported long-term clinical outcomes or complication rates. Overall, the evidence base was limited by the inherent design constraints of the included studies, but the quality assessment highlighted important insights into surgical approaches and outcomes that were systematically reported in this review.
Table 2.
Quality assessment for retrospective cohort studies using Newcastle–Ottawa scale (NOS)
| Study | Risk of bias assessment of the observational studies according to NOS | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Selection | Comparability | Outcome | Total score | Quality | ||||||
| Representativeness of the exposed cohort | Selection of the non-exposed cohort | Ascertainment of exposure | The outcome of interest was not present at the start of the study | Assessment of outcome | Was follow-up long enough for outcomes to occur | Adequacy of follow-up of cohorts | ||||
| Zhang et al[6] | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | 7 out of 9 | Good | |
| Varol et al[10] | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | 8 out of 9 | Good |
| Tsunoda et al[13] | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | 8 out of 9 | Good |
| Park et al[28] | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | ⭐ | 7 out of 9 | Good | |
Table 3.
Quality assessment of case series using the Joanna Briggs Institute (JBI) tool
| No. | Major components | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| 1 | Were there clear criteria for inclusion in the case series? | Y | Y | Y | Y | Y |
| 2 | Was the condition measured in a standard, reliable way for all participants included in the case series? | Y | Y | Y | Y | Y |
| 3 | Were valid methods used for identification of the condition for all participants included in the case series? | Y | Y | Y | Y | Y |
| 4 | Did the case series have consecutive inclusion of participants? | Y | Y | Y | Y | Y |
| 5 | Did the case series have complete inclusion of participants? | Y | Y | Y | Y | Y |
| 6 | Was there clear reporting of the demographics of the participants in the study? | Y | Y | Y | Y | Y |
| 7 | Was there clear reporting of clinical information of the participants? | Y | Y | Y | Y | Y |
| 8 | Were the outcomes or follow-up results of cases clearly reported? | Y | Y | Y | Y | Y |
| 9 | Was there clear reporting of the presenting site(s)/clinic(s) demographic information? | Y | Y | Y | Y | Y |
| 10 | Was statistical analysis appropriate? | NA | NA | NA | NA | NA |
| Overall appraisal | I | I | I | I | I |
Table 4.
Quality assessment of case reports using the Joanna Briggs Institute (JBI) tool
| No. | Major components | 1 | 2 | 3 |
|---|---|---|---|---|
| 1 | Were the patient’s demographic characteristics clearly described? | Y | Y | Y |
| 2 | Was the patient’s history clearly described and presented as a timeline? | Y | Y | Y |
| 3 | Was the current clinical condition of the patient on presentation clearly described? | Y | Y | Y |
| 4 | Were diagnostic tests or assessment methods and the results clearly described? | Y | Y | Y |
| 5 | Was the intervention(s) or treatment procedure(s) clearly described? | Y | Y | Y |
| 6 | Was the post-intervention clinical condition clearly described? | Y | Y | Y |
| 7 | Were adverse events (harms) or unanticipated events identified and described? | Y | Y | Y |
| 8 | Does the case report provide takeaway lessons? | Y | Y | Y |
| Overall appraisal | I | I | I |
Discussion
In our systematic review a total of 27 studies including 811 patients who underwent neurosurgical operations with temporalis muscle preservation techniques were included. Aneurysm clipping was the surgical indication in 172 (21.2%) patients. Osteoplastic temporalis muscle flap was the most common technique used in 178 (21.9%) patients, followed by suturing the temporalis muscle to the cranioplasty plate in 79 (9.7%) patients. No chewing problems were recorded among all the patients analyzed and temporalis muscle atrophy was observed in only 13 (1.6%) patients.
Clinical anatomy implications
The temporalis muscle is frequently detached and mobilized in decompressive hemicraniectomy and pterional approaches. This muscle is derived from the first branchial arch and has a complex anatomy. Its functional integrity depends on its vascular supply, innervation and the integrity of its fibers[2]. The temporalis muscle receives its blood supply from the anterior deep temporal artery (ADTA), posterior deep temporal artery (PDTA), and middle temporal artery (MTA)[31]. The vessels run in between the muscle and the periosteum and subperiosteal dissection should preserve a sufficient muscular blood supply. The deep temporal nerve provides motor innervation to the temporalis muscle, and the temporomandibular joint. Injury to these nerves could result in chewing problems[4]. Specifically, muscle atrophy is most likely to happen between the anterior zygomatic arch and the orbit’s lateral wall. Therefore, it is necessary to maintain the ADTA supplying this area[4,32]. Muscle dissection, cauterization for hemostasis, and protracted muscle retraction can collectively cause damage to these structures as well as muscle fibers[32]. Furthermore, surgical techniques that may cause temporalis atrophy include incorrect reattachment, improper muscle fiber incision, and the use of a large muscular cuff for reattachment.[4,32,33]. Severe long-term contraction, shortage and atrophy of the temporalis may be the end stage of poor surgical techniques. Various techniques have been proposed to facilitate the manipulation of the temporalis muscle without compromising its vascular supply, innervation, or the integrity of its fibers (Table 1).
Temporalis muscle reconstruction
Less attention has been considered for the proper reconstruction of temporalis muscle during surgery resulting in cosmetic problems. Level II evidence supports the need to preserve the temporalis muscle’s origin as a fundamental way to preserve its function[34]. Spetzler and Lee used a muscle cuff left over from the dissection of the free bone graft to reattach the temporalis muscle[33]. The postoperative volume loss of the temporalis muscle was less pronounced when the cuff was left in place for reattachment than when the muscle was fully elevated without reattachment[35]. However, a large gap forms between the muscle and the cuff, making a perfect reapproximation unachievable.
Zager et al found that fixation of the muscle using micro screws is more effective than suturing the muscle to a leftover cuff. It eliminates the need to incise and split the muscle, reducing muscle fiber disruption[26]. This is the best option for elderly patients whose muscle fibers are fragile and cannot be sutured. However, in certain situations, placing screws at the superior temporal line is worrisome for some patients due to skin palpability. Webster et al reattached the muscle to its point of origin, using suspensory absorbable sutures anchored to 3 mm titanium micro screws placed inferior to the limits of the muscle rendering them impalpable[36]. Honig et al used to drill a V-shaped tunnel in the outer bone cortex through which the muscle is fixed by sutures[29]. Transosseous fixation of the temporalis muscle using sutures anchored to the bone is considered an easy method for proper reattachment, but it may be time consuming[37]. Rai et al reattached the muscle and fascial layer to their initial position by approximating sutures that ran through the free edge of the temporalis muscle with intact fascia from anterior to posterior[12]. Suturing the temporal fascia to the cranioplasty titanium mesh is another option with satisfactory esthetic results.[7]. The surgical setting, availability of resources and the surgeon’s preference could determine which method is used to anchor the temporalis muscle.
Osteoplastic flap
There are few studies that describe pterional craniotomy with a myofascial bone flap technique. Schlitt et al initially described the osteoplastic flap technique for frontotemporal craniotomies[38]. Hinge craniotomy involving elevating the whole muscle attached to the bone into a single segment was also used for decompressive craniotomy[16]. The technique does not involve blind temporalis dissection, thus, helps in protecting the facial nerve branches. Varol et al compared the cosmetic results using conventional pterional craniotomy and the osteoplastic technique. They observed that the osteoplastic technique outperforms the conventional one in terms of preserving the muscle bulk and aesthetic outcome[10]. Moreover, osteoplastic flaps maintain the blood supply to the bone, which promotes bone union. However, Schlitt et al reported a limited surgical exposure due to the inferiorly displaced muscle bulk[38]. Myofascial bone flap combined with zygomatic osteotomy promotes better surgical exposure than the conventional osteoplastic pterional approach (Fig. 2)[39]. Additionally, because dissecting the temporalis muscle from the bone is not performed, chances of preserving neurovascular supply are higher than the conventional pterional approach. However, there is a chance that the Gigli saw could partially violate the temporalis muscle, resulting in possible damage[20]. Matsumoto et al used this technique in 40 patients and there were no surgical exposure limitations. The cosmetic results were satisfying over the follow-up period[20]. The temporalis muscle, neurovascular system, underlying bone, temporalis fat pad and fascia are all preserved using the Agnes Fast craniotomy technique[40]. Moreover, the use of this technique is highly recommended in emergent situations where the time factor is critical.
Figure 2.
Osteoplastic temporalis muscle flap.
Temporalis muscle dissection
The MTA, anterior and posterior DTAs, and their connections represent an extensive vascular network supplying the temporalis muscle and connect to the STA[3]. The DTAs and STAs are necessary for the vascularity of the mobilized temporalis muscle, and the preservation of these vessels is crucial. Basal exposure, inferior displacement of temporalis muscle and extensive retraction for more than 15 minutes compromise the blood flow through the temporal arteries[40].
There are several techniques for temporalis muscle dissection.
Interfascial technique: The Interfascial technique was made popular by Yasargil in the 1980s and is widely used today[41]. The superficial fat pad, located between the superficial and deep layers of the temporalis fascia emerge when the incised superficial layer is pulled back anteriorly with fishhooks (Fig. 3). Along the superior temporal line, another incision is made, preserving the temporalis fascia’s cuff for future reconstruction. The muscle is then retracted anteriorly after being separated from the bone using a periosteal elevator[41].
Figure 3.
Interfascial technique.
Submuscular technique: By cutting the temporalis muscle all the way down to the bone and separating it, the temporalis fat pad could be elevated, together with the temporalis fascia, and TM as one block. Additionally, the muscle is separated from the bone using periosteal elevators.
Subfascial technique: The temporalis muscles’ superficial and deep layers are cut, together with the scalp folds are reflected anteriorly. To reach the zygoma, the subfascial dissection is a potential way (Fig. 4).
Figure 4.
Subfascial technique.
To preserve the neuro-vascular supply of the temporalis muscle, retrograde subperiosteal dissection has been described[1,4]. Oikawa et al used the retrograde subperiosteal dissection without any cosmetic or functional complications[4]. Bowles and colleagues also recommended this technique to preserve the vascular supply of the temporalis muscle[25]. Avoidance of dissection through the intermediate fat pad or beneath the superficial temporal fascia was considered by Vaca et al as level I and II evidence for preventing temporal hollowing[34]. Temporalis muscle denervation and atrophy are more likely to occur if the temporal fat is violated[34]. Rai et al described a new technique that involves antegrade, subfascial, and subperiosteal elevation of the temporalis muscle with posterior rotation, without any muscle incisions[12]. They used this technique in 50 patients, and the cosmetic outcome was satisfactory[12]. Excessive use of monopolar cautery could result in temporalis muscle devascularization. Oikawa et al found that 100 patients had cosmetically satisfying results by less extensive use of monopolar cautery[4]. Furthermore, Hwang et al analyzed the effect of electrocautery on the volume of temporalis muscle. They found that dissection of the muscle using monopolar cautery does not significantly lead to its atrophy if the surgical technique is properly employed[42]. Periosteal dissection should replace electrocautery especially with deeper layers, as these layers are rich in nerve supply. Considerable effort should be made to prevent the cautery blade from penetrating the muscle fibers. If bleeding occurs, it should be controlled by fine tip bipolar cautery.
Incisions design
A new technique for cutting and manipulating the temporalis muscle while performing hemicraniectomy is the retro-auricular incision[5,14]. Retroauricular incisions protect against temporalis muscle transgression and STA injury compared to the conventional reverse question mark incision[43]. McLaughlin et al vertically incised the deep temporal fascia and the temporal muscle in a T-shaped fashion without completely dissecting the deep aspect of the muscle preserving its vasculature[19]. Zhang et al designed a small temporalis incision for a focused Sylvian exposure and the small size of the incision did not undermine adequate surgical exposure meanwhile maintaining the integrity of the temporalis muscle[6].
Retraction tips
Prolonged surgical retraction of the muscle may lead to denervation and atrophy. Increased pressure in the muscle with reduction of its blood flow causes subsequent damage[44,45]. Prolonged downward retraction of the temporalis muscle could affect its vascular supply. Kadri and Al-Mefty reported ischemic changes following 15 minutes of retraction and irreversible ischemic damage if retraction extended for 6–8 hours[3,44]. Baldoncini et al suggested two safe zones for temporalis muscle hook placement, an anterior safe zone extending 14 mm posterior to the frontozygomatic suture and a posterior safe zone extending 30 mm anterior to the external auditory canal[46]. Dynamic retraction in the form of intermittent application of a retractor would alleviate pressure injuries. Padding the retractor blades with a sponge or a piece of gauze would prevent direct contact of the sharp blades with the muscle, minimizing its injury.
Surgical approach modifications
New minimally invasive surgical techniques have been put forth to reduce the surgical risks of pterional craniotomy, shorten hospital stay, reduce tissue damage, and enhance functional and aesthetic results. Superciliary, supraorbital and mini-pterional keyhole approaches are frequently employed as substitutes for pterional craniotomy. In patients undergoing aneurysm surgery, the incidence of postoperative temporal atrophy was significantly lower in the mini-pterional group[13]. In the minipterional approach, the surgical bone window is entirely situated beneath the temporalis muscle allowing easier repositioning of the temporalis muscle compared to the conventional approach. Incisions for decompressive craniotomy could be modified to avoid injury of the branches of STA. Placing the incision posterior to the ear is an example[14]. Preservation of the branches of STA is essential for proper muscle healing.
Temporalis adhesions and cranioplasty
Preserving the temporalis muscle during decompressive craniotomy is crucial for both postoperative masticatory function and cosmetic appearance. Following decompressive craniectomy, identifying a proper surgical plane between the dura and temporalis muscle is crucial for cranioplasty to avoid dural injury and subsequent CSF leak. At the time of closure, using materials like silicone elastomer sheets, expanded polytetrafluoroethylene membranes, bovine pericardial patches, and absorbable films is advocated as anti-adhesion methods for safe dissection. These materials are positioned between the dura and the temporalis muscle to reduce adhesions and facilitate future dissection[47-49].
Which technique is ideal
Cosmetic complications and temporalis hollowing occurred variably with almost all the techniques. There is heterogeneity in the complication rates among different techniques and we were not able to identify the most ideal one. The variability in surgical techniques, resources, differences in patient outcomes, and the absence of standardized guidelines undermines our ability to define the best technique. The choice depends upon several factors. The availability of surgical resources such as fixation screws, anti-adhesion dural substitutes, and water jet dissection tools is an important determining factor. Moreover, the surgical pathology is an important factor, for example, if a pterional is intended, supraorbital and mini-pterional keyhole approaches could be an alternative, while in decompressive craniotomies, incision modifications could be an alternative. Therefore, the surgical approach and the clinical situation could affect the decision which technique is the best option.
Additionally, the training level of the surgeon could be a determining factor. For experienced neurosurgeons, the keyhole approaches are technically easy, while for beginners other techniques such as subfascial, interfascial, and muscle approximation are easier. In critical situations under urgent neurosurgical interventions where time is a critical factor, the Agnes Fast craniotomy technique is a good choice. In geriatric populations, due to friability of muscle fibers, using micro screws fixation is more effective than suturing the muscle. To summarize, choosing a certain technique to preserve the temporalis muscle is a multifactorial decision that depends on several factors. The ideal technique choice is conditional depending on certain clinical, institutional and surgical factors.
Study limitations
Our study has several limitations. First, the lack of comparison between different techniques limits our ability to determine which technique is best in terms of cosmetic appearance and rate of complications. Additionally, meta-analysis was not feasible due to the variability across the studies. Significant variability in study designs, the small sample size and the lack of control group made a meta-analysis unlikely. The lack of standardized reporting and the heterogeneity in methodologies made statistical pooling inappropriate, as combining such diverse data could lead to misleading conclusions.
Some data was missing in certain articles, and the follow-up periods are variable, therefore, we were not able to properly determine the long term functional and cosmetic outcome over several years. The follow-up duration in included studies varies, affecting consistency in outcome assessment. Longitudinal multi-center studies are essential to adequately investigate pertinent outcomes. The learning curve of such techniques has not been assessed thoroughly indicating the need for adequate cadaveric simulation anatomical workshops for neurosurgery residents.
All the studies did not investigate the use of these techniques in redo surgeries, which doubt their usefulness in manipulating the temporalis muscle in recurrent cases. Most studies evaluated the cosmetic and functional outcome based only on patients’ clinical criteria such as cosmetic appearance, temporal hollowing, chewing problems, and flap appearance which are considered subjective parameters. Proper radiological volumetric analysis of the temporalis muscle is required to assess the individual effect of each technique on muscle size and function. Proper electromyographic studies could evaluate the functional outcome and confirm the effect of each method.
Conclusion
There are several techniques for preserving the integrity of the temporalis muscle through either proper reattachment, reapproximation, or surgical approach modifications that maintain the neurovascular supply of the muscle and keep the integrity of its fibers.
Footnotes
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
Contributor Information
Mohammed A. Azab, Email: mohammed.azab@kasralainy.edu.eg.
Khalid Sarhan, Email: kwssarhan@std.mans.edu.eg.
Oday Atallah, Email: oday.atallah@yahoo.de.
Alan Hernández-Hernández, Email: atefneuroemergency@gmail.com.
Ismail A. Ibrahim, Email: ismailaiaibrahim@gmail.com.
Ahmed Hazim, Email: Ahmedabuelnasr@gmail.com.
Ethical approval
Not applicable.
Consent
Not applicable.
Sources of funding
None.
Author contributions
M.A. contributed to the general idea and drafting; K.S. contributed to the analysis; O.A. contributed to supervision; A.F. contributed to figure designs; M.S. contributed to data extraction; B.K. contributed to revision and review.
Conflicts of interest disclosure
None.
Research registration unique identifying number (UIN)
reviewregistry1958.
Guarantor
Mohammed A Azab.
Provenance and peer review
Not commissioned, externally peer-reviewed.
Data availability statement
None.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
None.