Endoscopic endonasal dissection of the infratemporal fossa: Anatomic relationships and importance of eustachian tube in the endoscopic skull base surgery.

OBJECTIVES: Endoscopic endonasal approaches to the pterygopalatine and infratemporal fossae are technically challenging due to the complex anatomy of these areas. This project attempts to develop an anatomic and surgical model to enhance the understanding of these spaces from the endonasal endoscopic perspective.
METHODS: Eight pterygopalatine and infratemporal fossae were dissected in four adult human specimens in accordance with institutional protocols. All specimens were prepared with vascular injections using colored latex. Both the pterygopalatine and infratemporal fossae were accessed using a transpterygoid approach, which included a medial maxillectomy. Rod lens endoscopes (with 0°, 30°, and 45° lenses), surgical microscope, microsurgical and endoscopic instruments were used to complete the dissections.
RESULTS: Endoscopic endonasal approaches provided adequate access to the pterygopalatine and infratemporal fossae. Dissection of the internal maxillary artery and its terminal branches, and detachment of the medial and lateral pterygoid muscles were critical steps to access deeper structures of the infratemporal fossa. The lateral pterygoid plate was the most useful landmark to locate foramen ovale, and the mandibular branch of the trigeminal nerve. The Eustachian tube, medial pterygoid plate, and styloid process were the most useful landmarks to locate parapharyngeal poststyloid structures (parapharyngeal segment of the internal carotid artery, internal jugular vein, cranial nerves IX and X).
CONCLUSIONS: A medial maxillectomy coupled with a transpterygoid endoscopic approach, provides adequate access to the pterygopalatine and infratemporal fossae. The complex anatomy of the infratemporal fossa requires precise identification of surgical landmarks to assure preservation of neurovascular structures.