Surgical Outcomes of Extended Endoscopic Endonasal Approach for Skull Base Lesions.

The extended endoscopic endonasal approach (EEEA) has emerged as a transformative technique in the surgical management of skull base lesions [1-3]. By utilizing natural nasal corridors, this minimally invasive approach provides direct midline access to a wide range of anterior, middle, and posterior skull base lesions, including pituitary adenomas, craniopharyngiomas, meningiomas, and chordomas [1,6]. Compared to traditional transcranial approaches, EEEA offers several advantages such as improved visualization with angled endoscopes, reduced brain retraction, and potentially lower morbidity [2,4].

Despite these advantages, achieving gross total resection (GTR) remains challenging and is influenced by multiple factors. Lesion characteristics such as size, location, consistency, and degree of invasion into critical neurovascular structures-particularly the cavernous sinus and internal carotid artery-play a crucial role [7,8]. Additionally, surgical factors including the chosen approach, reconstruction technique, and surgeon experience significantly impact the extent of resection and postoperative outcomes [4,5].

Understanding the predictors that influence the extent of resection is essential for optimizing surgical planning, improving patient outcomes, and minimizing complications such as cerebrospinal fluid leakage and neurological deficits [7]. Therefore, evaluating surgical outcomes and identifying key predictive factors in EEEA for skull base lesions remains an important area of ongoing research.

Inclusion criteria

• 1. Adult patients aged 18 years or older. 2. Patients with radiologically confirmed skull base lesions (based on MRI ± CT) involving the anterior, middle, or posterior skull base.

• Patients undergoing lesion resection using the extended endoscopic endonasal approach (EEEA).

• Lesions amenable to endoscopic endonasal access, including: Pituitary adenomas with extrasellar extension Craniopharyngiomas Skull base meningiomas Chordomas and other midline skull base lesions 5. Availability of complete preoperative assessment, including: Clinical evaluation Neuro-ophthalmological assessment (when applicable) Radiological imaging 6. Availability of detailed intraoperative data, including surgical approach and intraoperative findings.

• Availability of early postoperative MRI (within 72 hours to 3 months) to assess the extent of resection.

• Patients with adequate postoperative follow-up (minimum 3 months) for evaluation of outcomes and complications.

Exclusion criteria

• 1. Patients aged less than 18 years. 2. Patients who underwent transcranial approaches. 3. Lesions not primarily involving the skull base or not suitable for endoscopic endonasal access.

• Patients with incomplete clinical, radiological, or operative data. 5. Absence of early postoperative MRI, making assessment of the extent of resection unreliable.

• Patients with insufficient follow-up (less than 3 months). 7. Cases managed by biopsy only without attempted lesion resection. 8. Patients with severe comorbidities significantly affecting surgical outcome (e.g., advanced systemic disease), if they introduce bias in outcome assessment.