Osteocutaneous Approaches and Free Tissue Transfers for Skull Base Tumours

Technical Summary: Osteocutaneous Approaches and Free Tissue Transfers for Skull Base Tumours

Problem Statement
The management of craniofacial tumors involving the skull base presents significant challenges regarding oncologic control, anatomical preservation, and reconstruction. The primary clinical problem is the necessity to achieve en bloc resection of malignant and benign pathologies to ensure negative surgical margins, as piecemeal resection or debulking is associated with worse prognoses and higher recurrence rates. Historically, deep exposure of the skull base was limited, often forcing surgeons to avoid surgery or perform incomplete resections. Furthermore, the reconstruction of extensive defects created by radical resection requires the separation of intracranial and extracranial spaces, the obliteration of dead space, and the restoration of function and cosmesis. Traditional regional flaps have often been insufficient in terms of size, vascularity, or bulk to prevent infectious complications such as meningitis in large defects.

Methodology
This study is a retrospective observational analysis of 32 patients treated by the senior authors at the Unidade Local de Saúde Gaia/Espinho between 1986 and 2025. The cohort was divided into two distinct groups based on tumor location and surgical complexity:

1. Posterior Cranial Fossa Group (n=19): Patients underwent surgical excision of vestibular schwannomas and meningiomas via a retromastoid suboccipital approach. Outcomes focused on resection extent, facial nerve preservation, and complication rates.
2. Anterior and Middle Cranial Fossa Group (n=13): Patients underwent radical en bloc tumor resection followed by immediate microsurgical reconstruction. This group involved complex osteotomies and free tissue transfers.

The study adhered to STROBE guidelines. Data collection included demographic information, tumor characteristics (histology, staging, location), operative details (specific osteotomies, flap types, recipient vessels), and postoperative outcomes (complications, functional deficits, recurrence, and survival). Selected cases were illustrated with pre- and postoperative imaging to demonstrate surgical planning and reconstruction techniques.

Key Contributions and Technical Approaches
The paper details specific surgical strategies derived from experience with congenital craniofacial deformities, adapted for oncologic resection:

• Exposure Osteotomies: The authors emphasize the utility of "exposure osteotomies" to facilitate en bloc resection. Techniques described include:
  • Supraorbital, Nasoglabelar, and Naso-orbitomaxillary osteotomies for central skull base lesions.
  • Orbitozygomatic and Orbitomaxillary osteotomies for posterolateral and middle cranial fossa lesions.
  • Combined transfacial intraoral double osteotomies of the mandible (Attia et al. technique) to access the pterygomaxillary fossa and parapharyngeal space while preserving the neurovascular bundle.
• Reconstruction Strategy: The study highlights the critical role of free tissue transfer in skull base reconstruction.
  • Flap Selection: The most frequently used flaps were the rectus abdominis myocutaneous flap (46.2%) and the osteomyocutaneous fibula flap (23.1%). Other flaps included anterolateral thigh, latissimus dorsi, and omental flaps.
  • Indications: Free flaps are presented as essential for extensive anterior and middle fossa defects to provide well-vascularized tissue, ensuring dural repair and preventing intracranial infection.
  • Adjuncts: The use of patient-specific PEEK implants for bony framework reconstruction and virtual surgical planning (CAD-CAM) is noted as a modern optimization for precision.
• Anatomical Classification: The authors advocate for the use of Ian Jackson's anatomo-surgical classification of the skull base (dividing the base into anterior and posterior regions with specific segments) to improve 3D conceptualization of defects and communication among multidisciplinary teams.

Results

• Posterior Fossa Outcomes: In the 19 patients with posterior fossa tumors, 78.9% experienced no major postoperative complications. Total resection of vestibular schwannomas was achieved in 64.7% of cases. Facial nerve preservation (House–Brackmann Grade I or II) was achieved in 63.1% of patients. One patient experienced tumor recurrence requiring radical mastoidectomy and radiotherapy.
• Anterior/Middle Fossa Outcomes: In the 13 patients requiring microsurgical reconstruction, there were no cases of total flap loss. However, local wound complications occurred, including dehiscence and prosthesis-associated infections. One patient died from uncontrolled postoperative hemorrhage and was excluded from outcome calculations.
  • Oncologic Margins: Microscopically positive margins (R1) were observed in 76.9% of cases, a statistic the authors note despite the goal of negative margins, likely reflecting the aggressive nature of the tumors treated.
  • Recurrence: One patient developed early local recurrence at three months; no other recurrences were observed during the mean follow-up of 36.7 months.
  • Functional Status: Despite significant deficits such as ocular loss (38.5%) and facial paralysis (23.1%), patients generally maintained acceptable functional status and quality of life.

Significance and Claims
The paper asserts that the successful management of skull base tumors relies on the parallel evolution of microvascular and craniomaxillofacial surgery. The authors claim that their experience demonstrates three primary advancements:

1. Expanded Surgical Access: The application of exposure osteotomies allows for safer, en bloc resections of complex tumors that were previously difficult to access.
2. Superior Reconstruction: Free tissue transfer is identified as the gold standard for extensive defects, offering reliable vascularity that regional flaps cannot match, thereby reducing morbidity and preventing infectious complications.
3. Multidisciplinary Planning: The integration of anatomical classification systems (Jackson) and 3D planning facilitates better communication and surgical outcomes.

The authors conclude that while the responsibility of the reconstructive surgeon is to restore three-dimensional anatomy, the ultimate goal is the separation of intracranial and extracranial spaces using well-vascularized tissue to ensure patient safety and long-term functional outcomes. The study modestly presents its data as an illustration of these techniques in practice, without claiming to establish new universal standards beyond the reported institutional experience.