The Anterolateral Thigh Flap as a Solution for Extensive Lateral Skull Base Defects: A Case Series

Abstract

Introduction: Tumors of the lateral skull base, particularly those arising from the external auditory canal and peri-retroauricular regions, present considerable surgical and reconstructive difficulties due to their intricate anatomy and aggressive nature. The anterolateral thigh (ALT) free flap offers a viable reconstruction option, enhancing oncological radicality while minimizing morbidity. Materials and Methods: A retrospective analysis was conducted on five cases of malignant tumors involving the external auditory canal and adjacent soft tissues, treated at a tertiary center from March 2023 to March 2025. All patients underwent radical resection, which included lateral or subtotal temporal bone resection, along with parotidectomy and neck dissection when necessary. Reconstruction was performed using myocutaneous anterolateral thigh free flaps. The study evaluated clinical outcomes, complications, and esthetic results. Results: The ALT flap was used in all cases without major postoperative complications. Two patients received adjuvant radiotherapy; one did not start treatment due to early recurrence. At follow-up, three patients were disease-free, while two had died from unrelated causes. Esthetic and functional outcomes were satisfactory in all patients. Conclusions: The ALT free flap is a universal and reliable option for the reconstruction of complex lateral skull base defects, especially in patients following the radical removal of tumors of the external auditory canal and peri-retroauricular areas. It offers excellent tissue coverage, facilitates adjuvant treatment, and has a low complication rate. While our experience supports its use in aggressive oncological resection, larger studies are needed to confirm these findings. Level of evidence: 4.

1. Introduction

The resection of tumors involving the lateral skull base presents a challenge for surgeons due to several factors. The anatomy of this region is complex, featuring various critical structures that contribute to different tumor histology, each with varying levels of aggressiveness and outcomes. Additionally, the nonspecific nature of symptoms often leads to delayed diagnosis, necessitating the creation of large defects during resection both comprising extracranial and intracranial structures exposing critical structures such as meningi and the brain. The skull base defects can be categorized using the classification system proposed by Irish et al., which is based on anatomical boundaries and expected tumor dissemination (Figure 1) [1].

Not all patients require a combined intracranial and extracranial approach [2]. Group 3 according to Irish et al., are tumors that often require a thorough surgical approach to achieve complete resection. The surgical plan aims to obtain oncological radicality with clear margins, considering the specific neoplasm involved, and is primarily dictated by three factors: tumor histology, site of origin, and extension [3]. While other regions have more predictable histologies such as squamous cell carcinoma (SCC) or lymphoma for the head and neck district [4,5] according to Irish, Region 3 of the lateral skull base can have three main types of lesions: primary malignant ear tumors, advanced parotid gland malignancies, and aggressive tumors in the infratemporal fossa and parapharyngeal space [6]. Surgical options must be tailored to the patient and can range from total parotidectomy, subtotal petrosectomy, to lateral temporal resection, either subtotal or total. To achieve oncological radicality, lateral neck dissection is often required. There is considerable ambiguity in the literature when discussing malignant tumors of the external auditory canal. Specifically, the difference between subtotal temporal resection and subtotal petrosectomy is often unclear, with some descriptions treating them as a single procedure [7]. It is important to make a clear distinction: subtotal temporal resection involves drilling the temporal bone after performing a lateral temporal resection, during which the temporal bone is removed en-bloc, including the anterior wall of the external auditory canal, also exposing the retroparotid soft tissues. On the other hand, subtotal petrosectomy does not involve the removal of the anterior wall of the external auditory canal, nor the complete resection of the temporal bone. It does not require exposure of the retroparotid soft tissues or removal of the auricular pavilion [7]. The resection of tumors in this area often results in the creation of large defects, which are very complex to repair and expose sterile and vital structures to the external environment. The goal of obliterating these defects includes protecting vascular and cerebral structures, preventing cerebrospinal fluid fistulas, and, not least, achieving a satisfactory esthetic outcome and an appropriate facial contour for the patient. Traditional options for reconstructing periauricular defects include the use of local or regional rotational flaps, split-thickness skin grafts, and free flaps. Local flaps are effective for covering smaller, generally superficial defects, such as separating the nasal cavity from the intracranial space, but they are not always sufficient for covering large defects. Additionally, surrounding tissues that are not affected by the disease may be rendered unusable due to prior radiation therapy or scarring and fibrosis from previous surgeries. Therefore, for extensive bone loss or skin defects that extend to the parietal scalp or involve exposed dura mater, these methods may not provide adequate reconstruction [8]. Regional pedicled flaps, such as the pectoralis major or suprascapular flaps, have been effectively used in these types of reconstructions, but the esthetic outcome is often unsatisfactory. Moreover, the pectoralis major flap presents a significant limitation related to its size, as it is often insufficient to cover large defects. Additionally, the pedicle may occasionally be too short to reach the reconstruction site, resulting in tension at the insetting, an increased risk of wound dehiscence and fistula formation, and, in some cases, necrosis of the most cranial portion of the flap. In recent years, free flaps have gained increasing importance. Various types of free flaps have been described for the reconstruction of lateral skull base defects: rectus abdominis, latissimus dorsi, scapula, radial forearm, or fibula flaps [9]. All these types of flaps present various limitations, including the need to reposition and move the patient, the small skin paddle, limited thickness, and comorbidities associated with the donor site [9]; in contrast, the ALT flap is a highly versatile flap, with a volume that lies between the radial and latissimus dorsi flaps [8]. It is widely used in head and neck surgery and can be harvested based on either septocutaneous or musculocutaneous perforators. It also offers the advantage of low morbidity and generally provides a long vascular pedicle [8]. The present study consists of a case series of 5 cases, all performed at our tertiary university referral center. This study evaluates the advantages, challenges, and outcomes associated with employing the ALT flap for reconstruction of lateral skull base defects. Owing to the uncommon nature of these cases and the fact that not all surgeries yield cutaneous defects requiring free flap reconstruction, case numbers remains limited.

2. Materials and Methods

This paper presents a continuous case series of five patients, all treated at the same tertiary academic center, who were diagnosed with malignant neoplasms of the auricular and retroauricular regions between March 2023 and March 2025. Inclusion criteria consisted of patients of any age diagnosed with malignant neoplasm of any histology, excluding lymphoproliferative diseases, who required surgical excision. Eligible cases involved defects that could not be closed by simple suturing. Patients whose defects were small and closed with local flaps, or those with larger and composite defects managed using pedicled flaps (such as the pectoralis major flap), were excluded from this study. Specifically, it includes five men with a mean age of 74.2 years (range 62–81): of whom three had external auditory canal carcinoma and two had retroauricular skin carcinoma, although all cases involved the external auditory canal (EAC). Three out of the five subjects were smokers or former smokers, and one of them was an active drinker. The examined clinicopathological features include presenting symptoms, tumor size, tumor histology, and staging. The three patients with external auditory canal carcinoma were staged according to the Pittsburgh classification [10], while the remaining two were staged according to the 8th edition of the American Joint Committee on Cancer (AJCC TNM system of the cutaneous carcinoma. All patients underwent whole-body staging CT and a dedicated CT scan of the ear and petrous bone. The histological analysis reported a diagnosis of squamous cell carcinoma in two of the tumors of the external auditory canal, while in the third case, the diagnosis was infiltrative basal cell carcinoma [11,12]. Regarding the histology of the two tumors of the retroauricular skin, one was a dermal sarcoma, and the other was a squamous cell carcinoma. We considered the Rosenthal classification for resections of the auricular region: specifically, in Class I, patients preserve the external auditory canal; in Class II, the patient undergoes a lateral temporal bone resection and may preserve part or all of the auricle; and in Class III, patients undergo total auricolectomy. According to this classification, four of our patients underwent a Class III resection, while one underwent a Class II resection with partial preservation of the auricle [8].

All ablative surgical procedures were performed by the same senior surgeon (L.S.). All microvascular flaps were harvested by the same operator (R.N.) with the assistance of the same second operator (V.A.). Microvascular anastomoses were consistently performed under an operating microscope (Zeiss Pentero 900^®, Oberkochen, Germany). Ethilon 9-0 sutures were used for arterial anastomoses and 8-0 sutures for venous anastomoses. The number of sutures placed depended on the vessel diameter and varied among patients, but generally ranged from eight to twelve stitches. Oncological radicality was prioritized in all cases; therefore, flap size was determined only after completion of the ablative procedure. The defect was measured, and the ATL flap was designed 1–2 cm larger than the measured size. All flaps were harvested as myocutaneous, with a preference for greater thickness in order to achieve more adequate defect filling and thereby obtain an improved esthetic outcome. All donor sites were closed primarily, with suction drains maintained for 4 days or until drainage ceased. Postoperatively, all patients were mobilized to a chair on postoperative day one and began ambulation on postoperative day two.

The standard protocol of our center for the preoperative assessment, monitoring and postoperative care of patients undergoing free flap reconstruction was applied. During the pre-operative assessment, all patients included in the study underwent comprehensive anesthesiological and cardiological evaluations, as well as CT angiography. In all five cases, no major cardiovascular risk factors for flap failure—including vascular stenosis, signs of vasculopathy, or cardiac arrhythmias (notably atrial fibrillation)—were detected. Anesthesiological evaluation is crucial to identify additional risk factors for free flap failure, such as diabetes, smoking, hypertension and renal insufficiency, allowing the anesthesiologist to implement appropriate intraoperative measures during general anesthesia in order to minimize the risk of flap failure.

Postoperative monitorization was characterized by scheduled follow-up visits at set times using Doppler technology, monitoring of Antithrombin third (ATIII), albumin, and antibiotic therapy. All patients were followed by the speech therapy service for facial nerve (cranial nerve VII) deficits. All patients provided written informed consent for the surgical procedure and for the acquisition and use of related photographic material.

Patient characteristics are summarized in

Table 1. Clinical anamnestic features of patients (EAC, External Auditory Canal; EAC External Auditory Canal; SCC Squamous cell carcinoma).

Patient	Age at Surgery	Smoking Habit	Site of Primary Tumor	Pittsburgh Staging	TNM Staging	Rosenthal’s Class	Histological Diagnosis
1	62	Ex	EAC	T1N0M0		III	Infiltractive basal cell carcinoma
2	77	Ex	Retroauricolar skin		pT4aN0 v0n1 R0 M0 G3	III	Dermal Sarcoma
3	79	Yes	EAC	T2N2cM0		III	SCC
4	81	No	Retroauricolar skin		pT4aN2b n1v1R0 M0 G3	III	SCC
5	72	No	EAC	T2N0M0		II	Verruciform SCC

.

3. Results

The surgical approach was based on the site of the primary tumor and staging (see Table 1). The patients with carcinoma of the EAC underwent subtotal temporal bone resection in one case and lateral temporal bone resection in the other two cases. The two patients with tumors in the retroauricular region underwent subtotal petrosectomy to ensure greater surgical radicality on the mastoid bone, sparing the anterior wall of the external auditory canal, which was not involved by the disease. Regarding the management of the parotid region: in the three cases with evident extension to the skin and pre-parotid soft tissues, total parotidectomy was performed for oncological radicality (patients 2, 3, 4). In patients 2 and 4, the tumor was in direct contact with the facial nerve, requiring complete nerve sacrifice. A tarsorrhaphy was performed simultaneously. In patient 3, nerve sacrifice was partial, with preservation of the temporofacial branch. In two cases of EAC carcinoma, one (patient 5) showed macroscopic involvement suspicious for parotid region involvement, so total parotidectomy was performed. The last patient (patient 1) had no macroscopic signs of disease, but since an adequate margin was not obtained from the facial nerve after subtotal petrosectomy and removal of the mastoid tip, partial parotidectomy was performed. Moreover, both patients had undergone LTBR, so we opted for parotidectomy to ensure radicality in the region adjacent to the anterior wall of the EAC (

Table 2. Surgical procedures and follow up. LTBR (lateral temporal bone dissection); STP (subtotal petrosectomy); STBR (subtotal bone resection).

Patient	Resection	Parotidectomy	Sacrifice VII cn	Tarsorrhaphy	Neck Dissection	Size Flap Pan	Venous Anastomosis	Arterial Anastomosis	Hause Brackmann VIICN Grading
1	LTBR	Partial	No	No	SND IB-II-III	12 × 6	Facial vein	Facial artery	III
2	STP	Total	Yes	Yes	SND I-V	20 × 8	Thyro-linguo-facial trunk	External Carotid artery	VI
3	STBR	Total	Partial	No	SND I-VII	20 × 8	Superior thyroid vein	Superior thyroid artery	IV
4	STP	Total	Yes	Yes	MRDN (IJV preserved)	11 × 9	Superior thyroid vein	Superior thyroid artery	V
5	LTBR	Total	No	No	SND IB-II-III	10 × 6	Facial vein	Facial artery	I

).

The House–Brackmann grading is reported in Table 2. As mentioned earlier, four patients underwent complete Class III resection according to Rosenthal, with total removal of the auricle; one patient underwent Class II resection, with partial preservation of the auricle. All the patients examined underwent unilateral SND, and the details are reported in Table 2. Regarding the reconstruction of the defect after resection, all patients underwent an appropriately sized anterolateral thigh flap (ALT), harvested as a myocutaneous free flap. Microvascular anastomosis was performed using Ethilon 8.0 for venous anastomoses (9.0 ethilon was reserved for arterial vessels) and the details of the vessels involved are listed in Table 2. In two cases (patients 1 and 5), the recipient artery for the anastomosis was the facial artery; in another two cases (patients 3 and 4), it was the superior thyroid artery; and in patient 2, the external carotid artery. For the venous anastomosis, the facial vein was used in two cases (patients 1 and 5), the superior thyroid vein in another two cases (patients 3 and 4), and the thyrolinguofacial trunk in patient 2. All anastomoses were end-to-end, with an adequate vessel caliber match.

The postoperative course was almost completely uneventful: only one case presented with a seroma at the donor site, which was resolved with conservative treatment within a few days.

Of the five patients under examination, only two were indicated for adjuvant treatment with radiotherapy; only one of them completed the treatment at another facility (patient 2) and is currently in follow-up, with no evidence of residual disease. The other patient, who was a candidate for radiotherapy, was unable to begin the treatment due to the detection of persistent disease on the PET/CT scan, and was therefore referred for oncological treatment. Regarding the long-term follow-up, with respect to the other patients, one is disease-free, and the last two have passed away due to other issues, but at the time of their last check-up, they showed no evidence of disease.

From a reconstructive standpoint, in all patients, the flap appeared well-integrated, with excellent defect filling and minimal residual bulging (Figure 2).

4. Discussion

In the case of tumors of region 3, according to Irish, there has always been significant debate regarding the extent and type of resection most appropriate; generally, the tumor’s extent influences the recommended treatment [13,14]. Resection options include lateral and extended temporal bone resection [15], and other studies have distinguished between lateral, subtotal, and total petrosectomy [16]. For advanced cases, en bloc resection with tumor-free margins remains the oncological principle [7,17,18]. A case series by Gidley et al. also reports lateral petrosectomy even for smaller tumors [19]. Our surgical strategy was based on tumor origin. Temporal bone resection was performed for all external auditory canal SCCs due to their aggressiveness. For skin and retroauricular soft tissue tumors, which show similar behavior, subtotal petrosectomy was chosen to ensure radicality at the mastoid. In both cases, STP was also necessary for functional reasons, to prevent middle ear infections and cholesteatoma, as type III resection (Rosenthal) was required [8,20]. Regarding the parotid management, our decisions were supported by the literature, where Mazzoni et al. describe extensive approaches even for T1 and T2 EAC tumors involving the parotid, in order to perform en bloc resection of the temporal bone with the adjacent soft tissues and ensure oncological radicality [21]. In more advanced cases (cT3 or cT4), when the bone between the roof of the auditory canal and the dura is reduced, Mazzoni et al. even propose a mini-craniotomy to be included in the en bloc resection [21]. The prognosis of SCC of the temporal bone is good in early-stage tumors (T1 and T2), but much poorer for T3 and T4 disease, with reported five-year survival rates ranging from 14% to 73% [18]. Reconstruction of large skin defects with local or free flaps is always essential to cover the defect, and even more so if adjuvant radiotherapy is planned. In our opinion, when a flap transfer is necessary, free flaps are clearly superior for esthetic reasons (to avoid pedicle bulging), more reliable in previously irradiated fields, and better when postoperative radiotherapy is planned [18]. A wide range of reconstructive options is available, and each free flap has specific pros and cons, and selection should be guided by these along with patient factors. The rectus abdominis flap, for example, often exceeds defect size, has a short pedicle, and carries a high risk of donor-site morbidity, particularly abdominal hernia. The radial forearm flap, although it is esthetically less pleasing, offers easier harvest and a suitable pedicle but may lack sufficient volume for large defects and carries a rare risk of limb ischemia due to radial artery involvement. This risk is very low but has been described in the literature [22]. It is usually addressed by the precautionary use of the Allen test; however, this test does not completely eliminate the risk. The most effective and minimally invasive examination for detecting a potential radial-dominant circulation is upper limb duplex ultrasonography. The subscapular system could be an excellent option, but it is often avoided due to the need to reposition the patient during surgery. This can significantly prolong operative time, and not all patients are suitable for this type of intraoperative management from an anesthesiological perspective [23,24]. The tensor fascia lata (TFL) flap is generally considered less versatile and, consequently, is utilized less frequently [25]. The posterior medial thigh free flap based on profunda artery perforators (PAP) often lacks sufficient bulk for large lateral cranial base defects and presents challenging perforator anatomy, despite their consistency and relative ease of dissection [26]. The medial sural artery perforator (MSAP) flap is often excluded, at least in our operative series, because it requires a longer dissection and is very thin, comparable to the radial flap. This makes it suboptimal for reconstructing large, deep defects [27]. The gracilis flap could be a valid alternative in terms of ease of harvest, complication rates, and outcomes; however, although no consensus exists in the literature, it is generally used for smaller defects, such as those of the parotid region, perioral area, tongue, or for facial reanimation [28]. The gastrocnemius flap competes closely with the ALT flap, as it is very versatile and easy to harvest; however, compared with the ALT flap, it is associated with a greater functional deficit at the donor site [29].

The ALT flap, on the other hand, is highly versatile and offers numerous advantages: it can be harvested without changing the patient’s position during surgery and while allowing for flexibility in selecting the flap’s dimensions. Typically, the pedicle is long, and it can be prepared simultaneously with the resection phase, using two surgical teams [8]. The flap can be prepared with varying thickness, depending on whether it is a cutaneous or myocutaneous flap, and the decision can be made based on the defect that need to be reconstructed. The versatility of ALT extends from small, ultrathin flaps to bulky myocutaneous reconstructions (such as ALT combined with TFL), which is a major advantage when addressing the complex tridimensional requirements of head and neck reconstruction.

This is the main advantage of this flap: for large defects, such as in the temporal region, it is ideal as it allows filling without causing unsightly bulging. For this reason, in all our patients, it was harvested as myocutaneous rather than just cutaneous. Moreover, preparing the ALT myocutaneous flap is easier, as the dissection of the vascular pedicle is simpler and quicker, because it is not necessary to follow the perforating vessel inside the muscle, this does not ensure the success of the anastomosis, but it reduces the risk of perforator injury. Esthetic outcomes are important; the submental rotation flap offers good color match but is often too small for large defects and cannot reach the temporal region. The pectoralis flap can provide adequate reach with a long pedicle, but esthetic results may be suboptimal due to visible pedicle bulk. The ALT flap is also associated with very few donor site complications. The few reported in the literature by Abdulbaki et al. are mainly related to wound dehiscence, hematoma at the donor site, seromas or infections [30]. However, Rosenthal et al. reported a higher incidence of donor site complications with the abdominal rectus flap compared to the ALT flap donor site [8]. Instead, Thompson et al. reported wound complications in 11 out of 14 cases treated with the ALT flap, including infections, seromas, and dehiscence [31]. Oranges et al. used the ALT flap for lateral skull base reconstruction in ten patients. Complications occurred at the recipient site in six patients: infections in two, hematoma in two, and dehiscence in two cases. They reported donor-site complications in four patients, mainly due to dehiscence [32]. In our series, however, we did experience in only one case a seroma at the donor site, which resolved with conservative treatment within a few days. This is in line with what was described by Trojanowski et al. [33]. Given its rapid healing and low complication rate, which help minimize delays in adjuvant radiotherapy, the ALT flap represents a reliable and safe reconstructive option. When planning reconstruction and evaluating the choice of flap, the potential need for radiotherapy should also be considered. Cardiovascular disease and advanced age, particularly over 60, increase the risk of flap ischemia after oncologic resection, due to poor vessel quality, reduced tolerance to blood loss, and prolonged anesthesia times [34,35]. In the series of 5 patients described, 4 were older than 70. None experienced cardiac complications postoperatively; however, one patient was later diagnosed with a second tumor at a different site, which ultimately led to death. In this case series, we did not perform facial nerve grafting after resection, but considering the patients’ age and the extent of the procedure, we opted for a conservative treatment approach rather than a rehabilitative one (tarsorrhaphy), in order to avoid further prolonging the operating time, which could have negatively impacted the general condition of the patients and led to systemic postoperative complications. We acknowledge the limited significance of the patient population under examination, as the sample size is extremely small. However, our case series is consistent with the oncological outcomes found in the literature. In conclusion, we believe it is essential to keep in mind the following key points: firstly, the aggressiveness of EAC carcinomas requires a radical surgical approach, with at least a lateral temporal bone resection (LTBR) or subtotal temporal bone resection (STBR), even for early-stage tumors. Secondly tumors of the peri- and retroauricular region, according to our experience, should be treated with the same level of care as those involving the external auditory canal, as they seem to exhibit comparable aggressiveness toward the temporal bone, as found in the literature. In this regard, STP may play a crucial role. In a third place we want to underline that the reconstruction of the defect with the ALT flap is effective, manageable, and not associated with significant complications either at the donor or recipient site. Finally, we strongly believe that the esthetic outcome after ALT flap reconstruction is satisfactory and is achieved in relatively short periods, which is advantageous for patients who require adjuvant therapy.

5. Conclusions

Temporal bone tumors, originating from the EAC or from the pre- and retroauricular soft tissues, are very rare and locally aggressive neoplasms. An adequate patient assessment, a tailored surgical planning specific to the case, and a generally invasive approach are crucial to ensure oncological radicality. The reconstruction of large defects in the lateral skull base and temporal region is successfully achieved with the free anterolateral thigh (ALT) flap. This free flap offers numerous advantages for both the surgeon and the patient, providing satisfactory functional and esthetic outcomes, while avoiding complications that could interfere with the multidisciplinary treatment of these complex patients. The results obtained in this case series align with findings in the literature, although further prospective studies with an adequate sample size are needed to provide greater statistical significance to the described outcomes.