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Arch Hand Microsurg > Volume 29(2); 2024 > Article
Nuch and Hong: Reconstruction methods for large cranial-nasal communications: surgeons’ concerns about proper anterior skull base reconstruction

Abstract

Purpose

Skull base reconstruction is one of the most difficult reconstructive surgical procedures. Due to its complexity, most surgeons have modified the reconstruction methods to minimize the postoperative complications and mortality rate. In the past, flap surgery was not usually performed, but it has recently become more common due to advances in medicine. In this study, we analyzed successful flap surgery methods in skull base reconstruction for large cranial-nasal communications.

Methods

Patients who underwent skull base reconstruction from April 2015 to January 2024 were eligible for this study. Of these patients, we included those who underwent reconstruction using a volumetric flap. Reconstructions that only used the conventional galeal flap, allograft skin, or bone substitute were excluded. The reconstruction methods used local flaps and free flaps.

Results

In total, 22 patients underwent skull base reconstruction. The most frequently used local flap was the bilateral reverse temporalis muscle flap (seven of 11 cases), and the most frequent free flap was the anterior lateral thigh flap (10 of 11 cases). Other local flap operations used the modified temporalis muscle flap and scalp flap. A rectus myocutaneous flap was also used. There were no cases of flap necrosis.

Conclusion

Flap surgery is needed for skull base reconstruction in patients with large cranial-nasal communications. As long as the flap volume is large enough to block and fill the defect, either a local flap or a free flap can be used for reconstruction.

Introduction

Head and neck reconstruction (skull base reconstruction) is a difficult type of craniofacial reconstruction surgery, even for reconstructive surgeons. It is probably one of the surgeries that provides the most concern to neurosurgeons and ear-nose-throat (ENT) surgeons, who are responsible for removing the primary lesions. Plastic surgeons must trust the neurosurgery (NS) and ENT teams to perform the resection, and the NS and ENT teams must also trust the plastic surgery team to perform surgery [1-4]. If the flap surgery located outside the skull area fails, another nearby flap can usually be used for the second revision, but in the skull base reconstruction, there is little available tissue around. Additionally, if the flap surgery in the other areas fails, there is enough time for the next surgery. However, patient mortality is very high when the flap fails in skull base reconstruction [5,6].
Skull base defects can occur due to various causes such as tumors, trauma, or lumpectomy. If the posterior wall of the frontal sinus is open, the frontal sinus area must be closed or blocked. The method for doing so involves removing the frontal sinus mucosa and inserting a galea flap, bone substitute, or fat tissue to block the cranial-nasal communication [7-9]. However, if the frontal sinus extensively damages or if the tumor simultaneously invades the cranium and nasal cavity, the entire frontal sinus will completely open after the lesion is resected. Defects can also impact the cribriform area. In this case, the extent of the defect lesion up to the skull base may be too large to solve using the existing methods [10,11]. Skull base reconstruction plays an important role in preventing infections from ascending into the cranium by blocking cranial-nasal communication [1,12,13].
The authors have performed skull base reconstruction since 2015, mainly using the reverse temporalis muscle flap and free flaps for reconstruction. The skull base defect was not a common disease in the head and neck surgery that affected both the cranium and nasal cavity. The skull base reconstruction is a complex surgical procedure, it needed to be performed collaboratively by three departments—plastic surgery, NS, and ENT surgery. Here, the authors aimed to describe the advantages and disadvantages of the skull base reconstruction methods with an emphasis on surgical techniques.

Methods

Ethics statement: This study was approved by Institutional Review Board of Severance Hospital, Yonsei University Health System (No. 4-2024-0234). Written informed consent was waived due to its retrospective study.
Patients who underwent skull base reconstruction from April 2015 to January 2024 were eligible for the study. Of these patients, the authors included those who underwent reconstruction using a volumetric flap. Reconstructions that used only the conventional galea flap, allograft skin, or a bone substitute were excluded.
The superficial temporal artery was marked before both free flap and local flap surgeries; this was especially important when the reverse temporalis muscle flap was used. Moreover, when using a scalp flap or bipedicle flap, more distal tissues were used by designing an axial flap instead of a random flap.
The surgical methods were divided into local flap and free flap procedures. Local flap surgery was performed using the temporalis muscle flap and scalp flap. The free flap procedures used the anterior lateral thigh (ALT) flap and rectus myocutaneous flap. The local flap procedures used a flap that could be harvested nearby and were performed according to each patient’s situation. The authors had previously used the reverse temporalis muscle flap method [1,12]. Briefly, this method involved turning over the temporalis muscle and sending it as far as possible.
The superficial temporal fascia acted as a bridge to supply blood flow to the temporalis muscle and was attached to the superficial temporal artery. The superficial temporal fascia and deep temporal fascia remained connected, allowing blood flow to the temporalis muscle. This connection area must be at least 2 cm. When both frontal sinuses were completely opened, bilateral reverse temporalis muscle flaps were applied. The flaps were connected at the medial lines together (Fig. 1).
The free flap procedures used the superficial temporal artery and vein as the main pedicle. The patient was in a supine position because NS and ENT surgery were performed together. Therefore, can only be used in the supine position. After the tumor ablation by the NS and ENT teams, the skull base was properly cleaned and prepared. In particular, the small wall and bony spur of the frontal sinus had to be removed and burred until flat and round. Otherwise, dead space, fluid collection, and infection could have occurred between the spaces.
Flap in-setting was performed by packing the cranial-nasal communication. At this time, because it should not be pushed up from below, it was fixed to surrounding tissues, such as the frontal bone and fascia, rather than to the nasal cavity area. The volume was sufficient to cover the entire brain dura. When covering the bone flap again, the surgeons avoided pressing on the part where the pedicle entered (Fig. 2).
In this study, some problems that were not directly related to the surgery were not analyzed, such as the recurrence of existing cancer or skin lesions after radiotherapy.

Results

Twenty-two patients were included, consisting of 16 male and 6 female patients. The average patient age was 52.8 years, and the ages ranged from 26 to 79 years. Eleven local flap procedures and 11 free flap procedures were performed on the 22 patients (Table 1). Of the local flap procedures, seven used bilateral reverse temporalis muscle flaps and the rest used the unilateral reverse temporalis muscle flap, temporalis muscle flap transposition, or scalp flap transposition. As for the free flap procedures, 10 cases used the ALT flap, and one used the rectus myocutaneous flap (Table 2). Most of the local flaps were bilateral reverse temporalis muscle flaps (Fig. 1). Most of the free flaps were ALT flaps (Fig. 2).
All surgeries were completed without flap necrosis, and all patients were discharged. No side effects occurred within 1 year after the reconstruction. Patients who underwent the surgery in 2024 were evaluated 2 months after operation, and no special side effects were observed.

Discussion

There are many regions of the skull base, but the skull base reconstruction is only required when the cribriform plate is destroyed and there is communication between the cranium and nasal cavity. The cribriform plate is where the olfactory bulb, responsible for the sense of smell, is located. The flap surgery can be considered when tumors originating in the cranium invade the nasal cavity or when tumors within the nasal cavity have moved up into the cranium. Sometimes, it expands and invades the orbit, but such cases require no special consideration in reconstruction [9,10,14].
Skull base tumors have a deep origin, and it is difficult to find a method to treat them. The skull base area has various cranial nerves, including the internal carotid artery, cavernous sinus, and optic nerve, which exist in a small space. Moreover, it is connected to the frontal sinus and sphenoid sinus, enabling communication between the outside cranium and the brain area after surgery. Therefore, the skull base is difficult to both remove and rebuild. Even after the reconstruction, the risk of ascending infection is considerably high [1,12,15].
The most important goal of skull base reconstruction is to prevent communication between the cranium and nasal cavity. It is also important to fill the space within the cranial cavity. Because the flap is within the cranial cavity and the vascular pedicle is outside the cranial cavity, the space between them must not be compressed to prevent the bone margin from being damaged. The flap should not be pressed when covered by the skull bone [7,16-18].
Although reverse temporalis muscle transposition is a possible surgical method [1,12], the blood flows in a reverse pattern, the results are difficult to predict, and secondary healing, infection, temporal hollowness, and skull bone absorption are likely to occur as a result. Additionally, because the temporalis muscle alone may be insufficient in size, the galeal flap must be used to reinforce it. Therefore, the superficial temporal pedicle and the galeal flap are used in a reverse pattern and must be prepared from the beginning before the defect removal. Otherwise, it may be damaged during bicoronal incision and craniotomy in NS. For these reasons, preoperative preparation required more effort than free flap reconstruction [19,20].
In reconstruction using a free flap, the bicoronal incision was designed and the superficial temporal artery previously determined by Doppler ultrasound was marked to avoid damage. The amount of tissue needed for reconstruction was approximately the size of a hand. The authors mainly used the ALT flap because it provided more volume of tissue bulk than the other flaps. The radial forearm flap could also be used, but the volume may be insufficient. Therefore, considering the volume control and vascular length, the ALT flap was the most appropriate for reconstruction.
The main components used in the ALT flap are the skin, fat, and fascia. Because the ALT flap harvest went medially, it was essential to perform deepithelization. The fat and fascia were included, and the part of the perforator muscle needed to keep preventing kinking. Therefore, the flap should not include muscles. Thus, reconstruction of that muscle volume is not necessary, and if atrophy occurs in the future, the reconstructed volume may sink significantly [3,4,12,21].
In addition, postoperative care is very important, and the L-tube must be placed before or during the surgery. After surgery, head elevation should be maintained at 30°. If the patient is in the flat supine position, the secretions may regurge and cause difficulty for the patient [12,22].
In the beginning of using flap surgery, the authors mainly used local flaps, but recently they have used free flaps as their first choice because the amount of tissue in the local flap is relatively limited. When more tissue bulk was required, a muscle flap could also be harvested from the free flap and the volume was sufficient. Over time, the local flap was also limited by inflammation due to atrophy and insufficient blood supply in the distal part. The patients also complained of bilateral temporal area hollowness. Therefore, the authors changed from local flap to free flap procedures to preserve the temporalis muscle. They also used a scalp flap even though they planned to use the free flap because the patient was too old or had poor lung conditions.
However, as all reconstruction surgeons will always face difficulties with free flaps, it cannot be said with certainty that free flaps are the best option for skull base reconstruction and provide the best results. Moreover, reconstruction using the reverse temporalis muscle was also quite good and less problematic than the surgical procedure. It is important to be fully aware of the advantages and disadvantages of each reconstruction method and to fully explain these significant factors and results to the patient so they can make the best choice for both the surgeon and the patient [1,3,6,12,23].
Depending on the location of the lesion, it is not uncommon for NS, otolaryngology, ophthalmology, and plastic surgery to perform surgery together. In the case of tumors invading the cribriform plate, tumors grew up from inside the nasal cavity; in other cases, the brain tumor grew down to the nasal cavity. Furthermore, the orbit was invaded in some cases, and surgery was accompanied by eye enucleation [24].
Due to the complexity of the surgical site, radiation therapy and chemotherapy are sometimes used as treatment after palliative surgery rather than complete resection. If the focus is only on the treatment of the tumor and reconstruction is not discussed during the collaborative treatment, problems with wound healing will occur as the tumor remains in the border area that needs to be reconstructed. Furthermore, if the wound does not heal, the possibility of ascending infection from the nasal cavity is very high and the patient’s mortality rate increases significantly. Therefore, all collaborating departments, including the plastic surgery department, which performs reconstruction, must attend conferences or meetings before performing the surgery. A simple call asking the plastic surgery team to perform reconstruction after the lesion ablation surgery has been performed will be of no help to either the department or the patient.
When discussing joint surgery, each department must understand the characteristics of the others and all the processes; for example, both the tumor removal team and the radiation treatment team must understand the reconstructive surgery, and the reconstructive surgery team must also understand the tumor removal team. In other words, everyone must be aware of the tumor type and stage, the patient’s previous surgery and radiation treatment range, the duration of the surgery, and the patient’s prognosis and postoperative treatment plan. Therefore, in collaborative surgery, no one side can push forward its own opinion; a process of including and understanding each other is necessary and significant for everyone to work as a team, and this is the shortcut to ensuring good patient outcomes.

Conclusion

The authors performed skull base reconstruction in cases of large cranial-nasal communication defects using diverse flap methods. The defects could not be covered and filled up using only the galeal flap, mucosal flap, fat graft, or bone substitute. If the flap volume is large enough, the local flap can be used. But the free flap is more advantageous in terms of volume. Reconstructive surgeons choose the flap considering the defect area, the volume, and the patient’s condition. In addition, it will be better to plan before performing skull base reconstruction by considering the surgeons’ capacity and challenges to minimize postoperative complications and the mortality rate.

Conflicts of interest

Jong Won Hong is the Deputy Editor of Archives of Hand and Microsurgery and was not involved in the review process of this article. There are no other conflicts of interest to declare.

Notes

Funding

None.

Fig. 1.
Reverse temporalis muscle flap for skull base reconstruction in a 41-year-old woman. (A) T2-weighted magnetic resonance imaging (MRI) showing an angiofibroma extending into the cranium, orbit, and nasal cavity. (B) A large cranial-nasal communication after tumor ablation. (C) A galeal flap for the baselining. (D) Bilateral reverse temporalis muscle flap in-setting. (E) T2-weighted MRI showing the reverse temporalis muscle flap blocking and filling the defect site 3 weeks after surgery.
ahm-24-0017f1.jpg
Fig. 2.
Anterolateral thigh (ALT) free flap for skull base reconstruction in a 67-year-old man. (A) T2-weighted magnetic resonance imaging (MRI) showing metastatic renal cell carcinoma in the cranium, orbit, and nasal cavity. (B) The superficial temporal artery and vein were identified and prepared. (C) A large cranial-nasal communication after tumor ablation. (D) An ALT flap was harvested. The epidermis had to be removed. (E) The ALT free flap blocked and filled the defect site. (F) T2-weighted MRI 3 weeks after surgery.
ahm-24-0017f2.jpg
Table 1.
Skull base reconstruction methods over time
Year Local flap Free flap Total
2015 1 0 1
2016 1 0 1
2017 3 0 3
2018 2 1 3
2019 1 0 1
2020 2 0 2
2021 0 4 4
2022 0 2 2
2023 0 3 3
2024 1 1 2
Total 11 11 22
Table 2.
Flap methods for skull base reconstruction
Flap method No. of cases 
Local flap
 Reverse temporalis muscle flap, bilateral 7
 Reverse temporalis muscle flap, unilateral 1
 Temporalis muscle flap, unilateral 1
 Temporalis muscle flap c extended galea, bilateral 1
 Scalp flap 1
Free flap
 Anterolateral thigh flap 10
 Rectus myocutaneous flap 1

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