Evolution of Transmaxillary Approach to Tumors in Pterygopalatine Fossa and Infratemporal Fossa: Anatomic Simulation and Clinical Practice
Introduction
Tumors located in the pterygopalatine fossa (PPF) and infratemporal fossa (ITF) present significant challenges to neurosurgeons due to their deep-seated location and proximity to critical neurovascular structures. Lesions in these regions, such as meningiomas, schwannomas, and nasopharyngeal angiofibromas, are often benign but can be difficult to remove safely and completely. Traditional lateral approaches to these areas are hindered by obstacles such as the temporal muscle, mandible, and parapharyngeal tissue. In contrast, anterior approaches offer several advantages, including the avoidance of craniotomy, shorter surgical distance to the tumor, and an extradural approach that reduces the risk of infection and cerebrospinal fluid (CSF) leakage. With the advent of neuroendoscopy, surgeons can now perform these procedures with minimal incisions, further reducing patient trauma.
The PPF is a narrow, inverted pyramid-shaped space located posterior to the maxillary sinus (MS). It contains the pterygopalatine ganglion, vidian nerve, maxillary nerve (V2), and branches of the maxillary artery. The ITF, located below the middle cranial fossa, contains the lateral and medial pterygoid muscles, branches of the mandibular nerve (V3), and the pterygial segment of the maxillary artery. The lateral pterygoid plate serves as its medial border. Two primary approaches are used to access these regions: the anterior transmaxillary approach, which involves opening the anterior wall of the MS, and the transnasal approach, which opens the medial wall of the MS. This study compares these two approaches in terms of exposure area and operability, and applies the findings to clinical practice.
Methods
Ethical Approval
The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Beijing Tiantan Hospital. Written informed consent was obtained from all patients prior to their participation.
Specimens
Twenty adult cadaveric heads were used to simulate surgical approaches. The internal carotid artery (ICA) and internal jugular vein were injected with red and blue silicone, respectively, to standardize the specimens. Ten specimens were used to simulate the anterior transmaxillary approach with a microscope, while the remaining ten underwent a modified endoscopic transnasal transmaxillary approach using a rigid endoscope. High-speed drills were used in both approaches. The left sides of the specimens were dissected first.
Anterior Transmaxillary Approach
For the microscope group, the Weber-Fergusson incision was used to expose the anterior wall of the MS. The fossa canina was identified as the starting point for drilling into the MS cavity. A 2 cm x 2 cm bone window was created, preserving the infraorbital foramen. The infraorbital artery (IOA) and infraorbital nerve (ION) were dissected and measured. The posterior wall of the MS was drilled to expose the PPF, and the diameters of the maxillary artery, sphenopalatine artery, descending palatine artery, and Vidian artery were measured. The lateral posterior wall of the MS was removed to expose branches of V3, pterygoid muscles, and the venous plexus. The diameters of the middle meningeal artery, anterior deep temporal artery, and posterior deep temporal artery were also measured.
Modified Endoscopic Transnasal Transmaxillary Approach
For the endoscope group, an endonasal prelacrimal recess-maxillary sinus corridor was used. The mucous membrane near the inferior nasal concha was cut and peeled to expose the bony nasolacrimal duct. The MS was accessed through the medial wall, and the posterolateral wall of the MS was drilled to expose the PPF.
Area of Exposure
The exposure areas for both approaches were evaluated based on the visibility and operability of the main boundaries of the PPF and ITF. The superior line was defined by V2 in the PPF, the lateral line by the vertical margin of the temporal muscle, the medial line by the line between the vidian nerve and pterygopalatine ganglion, and the inferior point by the intersection of the medial wall, dorsal wall, and base of the MS.
Patients Selection and Clinical Protocol
Five patients with tumors in the PPF and ITF were enrolled in the study. Preoperative imaging included computed tomography (CT) and magnetic resonance imaging (MRI). The modified endoscopic transnasal transmaxillary approach was used for tumor resection. Postoperative CT and MRI scans were performed to assess the extent of tumor removal and any complications.
Results
Anatomic Findings
In the MS, the IOA and ION served as guides to the PPF. The mean length of the IOA was 4.41 ± 1.10 mm, and its diameter was 0.17 ± 0.33 mm. The maxillary artery in the PPF had a diameter of 3.77 ± 0.78 mm. The sphenopalatine artery, descending palatine artery, and Vidian artery had diameters of 2.84 ± 0.62 mm, 2.47 ± 0.58 mm, and 1.84 ± 0.52 mm, respectively. The V2 in the PPF had a mean length of 4.75 ± 0.89 mm. In the ITF, the middle meningeal artery had a diameter of 2.79 ± 0.61 mm, while the anterior and posterior deep temporal arteries had diameters of 1.71 ± 0.47 mm and 2.06 ± 0.44 mm, respectively.
Clinical Findings
Among the five patients, four had schwannomas and one had adenocystic carcinoma. Total removal was achieved in all schwannoma cases, while subtotal removal was performed for the adenocystic carcinoma. Postoperative complications included facial numbness and pericoronitis of the wisdom tooth, both of which resolved within three months.
Discussion
The modified endoscopic transnasal transmaxillary approach provided sufficient exposure and operability for tumors in the PPF and ITF, comparable to the anterior transmaxillary approach. The endoscopic approach offers several advantages, including reduced trauma, preservation of nasal function, and avoidance of external incisions. The study highlights the importance of understanding the anatomic relationships in the PPF and ITF for successful tumor resection. The endoscopic approach, with its minimal invasiveness and reduced complications, is a viable option for surgeons experienced in neuroendoscopy.
Conclusion
The modified endoscopic transnasal transmaxillary approach is a feasible and effective method for resecting tumors in the PPF and ITF. It offers significant advantages in terms of reduced patient trauma and complications. With proper training and understanding of the anatomic relationships, neurosurgeons can effectively utilize this technique for the treatment of deep-seated skull base tumors.
doi.org/10.1097/CM9.0000000000000142
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