Introduction: Sinonasal malignancies demonstrate perineural tumor extension and can infiltrate the trigeminal nerve. We delineated the anatomy of the maxillary nerve (V2) and its specific segments with respect to the endonasal as well as transcranial landmarks. Surgical relevance of these segments was explored in relation to the need for their sacrifice to achieve tumor resection.
Methods: The endoscopic endonasal anatomy of V2 was studied in 4 fresh human head silicon-injected specimens. The endoscopic approach to V2 is illustrated in a patient who underwent resection of adenoid cystic carcinoma with perineural involvement of V2 to demonstrate surgical technique and limitations.
Results: Human head specimens underwent bilateral endoscopic endonasal transpterygoid approach (8 sides). V2 prominence and the maxillary strut (MS) were identified in the lateral recess along with the paraclival carotid protruberances. The regions superior and inferior to the V2 corresponding to the anteromedial and anterolateral triangles were exposed. V2 can be classified into three segments: interdural (from the Gasserian ganglion (GG) to the proximal part of the MS); intracanalicular (corresponding to the anteroposterior length of the MS) and pterygopalatine (distal to the MS). Endonasally the average length of the interdural and the intracanalicular segments were approximately 9 and 4.5 mm respectively. V2 following its division distal to the MS, was successfully dissected off the middle fossa dura and transected just distal to the GG through a purely endoscopic interdural approach.
Conclusions: Endonasally the interdural segment can be safely mobilized between the periosteal and meningeal dural layers while ensuring the integrity of the middle fossa dura. This allows transection of infiltrated V2 to facilitate tumor resection without entering the intradural/arachnoidal space. Posteriorly this is limited by the GG and superiorly and medially by the dural envelope surrounding the cavernous sinus and the paraclival carotid artery.
Patient Care: This new anatomical knowledge will guide the surgical approach to maxillary nerve segments as it relates to the need for their sacrifice to achieve maximal tumor resection while minimizing morbidity and allowing rapid initiation of adjuvant therapies.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Understand the anatomy of the maxillary nerve (V2) and its specific segments with respect to endonasal as well as transcranial landmarks.
2) Use this new anatomical knowledge to design and perform surgical approaches to V2 segments specific to the need for their sacrifice to achieve tumor resection.