Endoscopic transnasal approach to pterygopalatine fossa and infratemporal fossa: case series utilizing endoscopic modified medial maxillectomy (EMMM)/direct approach to the anterior and lateral part of the maxillary sinus (DALMA)

TL;DR

This paper presents a new endoscopic surgical technique combining EMMM and DALMA to safely access and treat lesions in hard-to-reach areas of the skull base.

Contribution

The study introduces a dual-portal endoscopic approach to improve access and resection of lesions in the pterygopalatine and infratemporal fossae.

Findings

Combining EMMM and DALMA allowed gross or subtotal resection in all five cases.

The dual-portal configuration improved instrument maneuverability and reduced interference.

Minimal postoperative complications were observed, with no major adverse events.

Abstract

Endoscopic transnasal surgery (ETS) has become an established treatment for skull base lesions; however, its lateral reach to the pterygopalatine fossa (PPF) and infratemporal fossa (ITF) remains limited due to restricted maneuverability within the nasal corridor. To address this limitation, the endoscopic modified medial maxillectomy (EMMM) and the direct approach to the anterior and lateral part of the maxillary sinus (DALMA) provides lateral access through the maxillary sinus. This study evaluated the technical feasibility and outcomes of ETS combining EMMM and DALMA.

A retrospective review was conducted on five patients (January 2021–April 2024) who underwent ETS involving EMMM and/or DALMA. Surgical trajectory, extent of resection, and postoperative outcomes were analyzed. EMMM preserved nasolacrimal duct and opened the medial maxillary wall for direct access to the PPF and ITF. In DALMA, submucosal dissection was extended laterally beyond the piriform aperture to remove the anterior maxillary wall creating as an additional port complementary to EMMM.

Two patients (trigeminal schwannoma, idiopathic cerebrospinal fluid leak) underwent EMMM alone, and three patients (meningiomas extending to the ITF/PPF) underwent combined EMMM and DALMA. The dual-portal configuration provided separate working corridors for the endoscope and instruments. This arrangement minimized mutual interference and improved surgical maneuverability, allowing exposure of the lateral skull base up to the medial border of the mandible. Gross or subtotal resection was achieved in all cases. Postoperative complications were minimal; one patient experienced slight worsening of facial numbness, and one experienced slight numbness in the upper lip, likely due to DALMA-induced injury of the anterior superior alveolar nerve.

Combining EMMM and DALMA approaches provides a safe and minimally invasive option for treating lesions extending laterally into the ITF and PPF. Dual-portal configuration appears to improve instrument maneuverability and facilitate more extensive resection, thereby potentially expanding the applicability of ETS.

The online version contains supplementary material available at 10.1007/s00701-026-06837-z.

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