The Styloid-Pterygoid Line: A Reproducible Anatomic Landmark for V3 Perineural Spread Biopsy

Perineural spread (PNS) along the mandibular division (V3) of the trigeminal nerve is an important prognostic finding in head and neck malignancies that leads to disease upstaging and treatment intensification. Histologic confirmation traditionally requires invasive open biopsy or challenging CT/fluoroscopically guided access through foramen ovale, which carries risks of hemorrhage, infection, and trigeminocardiac reflex activation. We describe a CT-guided transcondylar approach using the styloid-pterygoid line as an anatomic landmark to safely access the mandibular nerve within the infratemporal fossa. Six patients with head and neck malignancies demonstrating MRI findings suggestive of V3 PNS between 2015 and 2024 underwent CT-guided transcondylar needle biopsy targeting the abnormal mandibular nerve using the styloid-pterygoid line for anatomic localization. Technical success was achieved in all cases (100%). Histologic confirmation of malignant PNS was obtained in five patients (83%), directly leading to escalation of treatment, while one patient showed inflammatory changes without malignancy, with subsequent MRI demonstrating improvement in nerve imaging that validated the benign biopsy result. No procedural complications occurred. The CT-guided transcondylar approach using the styloid-pterygoid line provides a safe, effective, and reproducible method for tissue diagnosis of suspected V3 perineural spread. By targeting the mandibular nerve within the infratemporal fossa rather than at the skull base, this technique mitigates procedural risks while maintaining diagnostic yield. This technique should be considered when histologic confirmation of mandibular nerve involvement is required, and tissue diagnosis would alter clinical management. SUMMARY: CT-guided transcondylar approach utilizing the styloid-pterygoid line represents a safe, effective, and reproducible technique for obtaining tissue diagnosis of suspected mandibular nerve perineural spread. This method offers a minimally invasive alternative to foramen ovale puncture or open surgical biopsy, avoiding the risks associated with such interventions while maintaining high diagnostic yield. In patients with head and neck malignancy and imaging findings suggestive of V3 PNS, this approach should be considered as a diagnostic strategy to facilitate timely, accurate histologic confirmation and optimize therapeutic decision-making.