The use of free flaps in skull base reconstruction

Abstract

Skull base tumours are rare, comprising less than 1% of all tumours of the head and neck. Surgical treatment of these tumours involves the approach, the resection, and the reconstruction of the defect, which present a challenge due to the technical difficulty and anatomical complexity. A retrospective study of 17 patients with tumours involving the skull base, treated by resection and immediate reconstruction using microsurgical free flaps, is presented; 11 were men and six were women. The following types of flap were used: osteocutaneous fibula flaps, fasciocutaneous anterolateral thigh flaps, and myocutaneous latissimus dorsi flaps. The most common histology of the tumours was squamous cell carcinoma. The most frequent point of origin was the paranasal sinuses (58.8%). All of the free flaps used for reconstruction were viable. A cerebrospinal fluid fistula occurred in two patients, and in one of these cases, meningoencephalitis led to death. In conclusion, the reconstruction of large defects of the skull base after ablation requires a viable tissue that in many cases can be obtained only through the use of microvascular free flaps. The type of flap to be selected depends on the anatomical structures and size of the defect to be restored.

Skull base tumours are rare, comprising less than 1% of all tumours of the head and neck. The tumours that affect this region can originate in structures of the skull base, or more often, can proceed from adjacent structures, such as the paranasal sinuses, the orbital cavities, or the infratemporal fossa. The approach, the resection, and the reconstruction of the resulting defect present a challenge, due to the technical difficulty and anatomical complexity.

Craniofacial surgery techniques based on combined craniofacial approaches and reconstruction of the defect represent the standard treatment of tumoural pathologies of the anterior and medial cranial fossa. Since its initial use by Dandy in the resection of orbital tumours in 1941, and subsequently by Ketcham et al. in the surgical treatment of paranasal sinus tumours extending to the skull base, skull base surgery has evolved significantly, especially in recent years. Recent advances in radiology, microsurgical techniques, and reconstruction, as well as the development of multidisciplinary teams, have enabled skull base surgery to become a safe, effective treatment for this type of pathology. The introduction of endoscopic techniques has signified an advance in the diagnosis and treatment, most importantly of benign tumours of the skull base. In spite of the fact that the incidence of complications in the treatment of tumours in this region is decreasing, it still ranges from 24% to 56% according to the most recent figures, and cerebrospinal fluid (CSF) fistula and infections are the most frequent complications, presenting the highest morbidity and mortality.

Our experience with skull base surgery in a series of 17 patients with a tumour pathology invading the skull base is presented herein; special emphasis is placed on the use of free flaps in the reconstruction of the defect after ablation and on the postoperative complications.

Materials and methods

A retrospective study was conducted of 17 patients diagnosed with a tumour pathology infiltrating the skull base, who underwent surgery between 2005 and 2010. The tumour extension was evaluated in all of the cases via computed tomography and magnetic resonance imaging of the craniofacial region in axial, sagittal, and coronal projections. A preoperative ophthalmological study was performed on all of the patients presenting visual symptoms in their diagnosis. A preoperative biopsy was performed on all of the patients. After determining the tumour volume and extension, radical surgical treatment was planned, with the goal of achieving a tumour resection.

Selection of flaps

Five fibula free flaps were used for the craniofacial reconstructions of large defects, including those resulting from mandible or maxillary resection. The fibula flap has a long vascular pedicle and adds sufficient bone tissue for mandibular or midface reconstruction without a great volume of soft tissue. It is valuable for the reconstruction of bone defects of >12 cm in the mandible. The free anterolateral thigh (ALT) flap has a long pedicle and also allows direct closure of the donor site. This flap provides a large volume of soft tissue, like the rectus abdominis flap but without the risk of abdominal hernia. The ALT flap was used in two cases for soft tissue reconstruction of large defects in the craniofacial region, particularly after orbital exenterations. The free latissimus dorsi has a large pedicle flap and also adds a large volume of soft tissue including muscle. Ten of these flaps were used for the reconstruction of large defects of the skull base, filling dead spaces and sinuses.

Surgical technique

The technical details of the treatment of the various cases are shown in Table 1 according to the principles used in skull base surgery, in terms of the technique employed in the resection and reconstruction of each case, depending on the location and size of the tumour. A tracheostomy was performed in three of the patients (17.6%), all of whom had extensive tumoural lesions of the paranasal sinuses and a compromised airway, with the objective of facilitating the surgical approach and avoiding respiratory complications after surgery.

Table 1
Craniofacial resection and reconstruction technique and complications. a
Resection No. of cases Free flap reconstruction Intracranial infiltration: macroscopic dural invasion Complications and prior RT
Radical maxillectomy + ethmoidal sphenoidectomy 10 1 Fibula
9 Latissimus dorsi
4 cases; reconstructed with galeo-pericranial flaps 2 cases, 1 with prior RT (both with intracranial infiltration): surgical site infection and CSF fistula (1 of these developed into meningoencephalitis and resulted in death)
Hemimandibulectomy + infratemporal fossa approach 4 4 Fibula 1 case; reconstruction with fascia lata and galeo-pericranial grafts 1 Postoperative bleeding
2 Surgical site infection (1 had prior RT)
Orbital exenteration + ethmoidal sphenoidectomy 3 2 ALT
1 Latissimus dorsi

RT, radiotherapy; CSF, cerebrospinal fluid; ALT, anterolateral thigh.

a A total of five cases of intracranial infiltration required combined treatment by maxillofacial surgeons and neurosurgeons.

In 12 cases, the resection was subcranial, while in five cases, in which there was macroscopic infiltration of the dura mater, a combined subcranial and intracranial craniotomy approach was performed by a multidisciplinary team composed of maxillofacial surgeons and neurosurgeons.

All of the patients were given a prophylactic course of antibiotics. Lumbar drainage was not performed in any of the patients.

The surgical technique was analysed, evaluating the onset and management of postoperative complications, as well as surgical mortality. The tumours were classified into three categories according to their origin: (1) Tumours originating in the paranasal sinuses (maxillary sinus with orbital, sphenoid, and ethmoid sinus invasion) ( n = 10 patients): the facial approach to the paranasal tumours was through a Weber–Ferguson incision. A hemicoronal approach was added in four cases exhibiting intracranial invasion. Radical maxillectomies and ethmoidal sphenoidectomies were performed. (2) Tumours of mandibular origin ( n = 4 patients): the facial approach was through a pre-auricular incision and a cervical extension in order to perform a hemimandibulectomy. In one patient who presented intracranial infiltration, a hemicoronal approach was added to approach the infratemporal fossa. (3) Tumours of orbital origin ( n = 3 patients): orbital exenteration was performed, along with ethmoidal sphenoidectomies.

In the 13 patients in whom orbital extension was present, radical maxillectomies and ethmoidal sphenoidectomies were performed in 10, and orbital exenteration and ethmoidal sphenoidectomies were carried out in three. A unilateral fronto-orbital craniotomy was performed in a single bone flap.

In the cases of intracranial invasion in which dural or parenchymal infiltration was exhibited both in imaging tests and macroscopically, a hemicoronal approach was performed, preserving the pericranium for its subsequent use in the skull base reconstruction. The skull base was resected by performing osteotomies on the cribriform plate, planum sphenoidale, and orbital roof, as well as the dura mater infiltrated by the tumour. Once the dural separation and resection was completed, the basal dural defect was covered with a galeo-pericranial pedicle flap with duraplasty, re-establishing the barrier between the frontobasal dura and the paranasal sinuses, nasal cavity, and nasopharynx.

After resection, immediate reconstruction using microsurgical free flaps to cover the bone and soft tissue deficits resulting from excision of the tumour was performed in all cases. The types of free flap used are given in Table 1 .

Patient follow-up

Seven out of nine patients undergoing a radical maxillectomy ( Fig. 1 ) were free of disease after 3–5 years of follow-up. One of them underwent upper arch fixed dental implant rehabilitation. Two died after 1.5 years of follow-up.

Fig. 1
Radical maxillectomy with extension to the temporal region.

Three out of four patients who underwent a hemimandibulectomy had dental implants placed 2 years after the surgery. The fourth patient was lost during follow-up.

One out of three patients undergoing orbital exenteration went on to wear an eye epithesis and has survived 6 years free of disease. One patient died after a relapse a few months after the intervention. The third patient is free of disease at 2 years after the intervention and is awaiting the placement of an epithesis.

A quality of life test was not performed in this retrospective study.

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Jan 16, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on The use of free flaps in skull base reconstruction
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