Tailoring Surgical Strategy for Advanced Lateral Skull Base Malignancies: Anatomical Constraints and Histological Limits in Margin Control.

BACKGROUND

Radical temporal bone resection (TBR) is indicated for advanced lateral skull base malignancies. We previously classified TBR osteotomies into Anterior, Medial, and Posterior segments. Evaluating anatomical constraints and histological limits in these resections is essential to optimize strategies and prevent recurrence.

METHODS

We retrospectively reviewed 38 patients undergoing en bloc radical TBR since 2014: subtotal TBR (STBR, n = 17) or lateral TBR (LTBR, n = 21). Concomitant superior margin (S-segment) dural resection was performed in 6 patients. We measured the Tumor-to-Medial Structure Distance (TMSD) on multi-planar imaging. Skull base recurrence-free survival (SBRFS) was analyzed.

RESULTS

Mean follow-up was 65 ± 39 months. Operative time was shorter in LTBR than in STBR (P = 0.0126). Skull base recurrences occurred in 6 patients. Overall SBRFS did not differ significantly between groups (P = 0.144). Five were Medial-segment recurrences, exclusively following LTBR. Coronal computed tomography (CT) exposed a critical blind spot: because the tympanic membrane is positioned obliquely, tumors in the hypotympanum had a TMSD < 3 mm in all 5 recurrent cases. Within LTBR, SBRFS was significantly poorer for patients with a TMSD < 3 mm versus ≥ 3 mm (P < 0.001). The remaining S-segment recurrence occurred despite dural resection in a squamous cell carcinoma (SCC), whereas no recurrences occurred in chondroblastomas.

CONCLUSIONS

Conscious coronal CT evaluation is mandatory. A TMSD < 3 mm anatomically contraindicates LTBR due to hypotympanic blind spots, mandating STBR. Furthermore, S-segment dural resection efficacy appears histology-dependent, highlighting biological limits in aggressive SCCs.