Unilateral upper and lower subtotal maxillectomy approaches to the cranial base: Microsurgical anatomy

OBJECTIVE: The relationship of the maxilla, with its thin walls, to the nasal and oral cavities, the orbit, and the infratemporal and pterygopalatine fossae makes it a suitable route for accessing lesions involving both the central and lateral cranial base. In this study, we compared the surgical anatomy and exposure obtained by two unilateral transmaxillary approaches, one directed through an upper subtotal maxillectomy, and the other through a lower subtotal maxillectomy. METHODS: Cadaveric specimens examined, with 3 to 40x magnification, provided the material for this study. RESULTS: Both upper and lower maxillectomy approaches open a surgical field extending from the ipsilateral internal carotid artery to the contralateral Eustachian tube; however, they differ in the direction of the access and the areas exposed. The lower maxillectomy opens a combination of the transmaxillary, transnasal, and transoral routes to extra- and intradural lesions of the central cranial base. Performing additional osteotomies of the mandibular coronoid process and the sphenoid pterygoid process provides anterolateral access to the lateral cranial base, including the pterygopalatine and infratemporal fossae, and the parapharyngeal space. The upper maxillectomy opens the transmaxillary and transnasal routes to the central cranial base but not the transoral route. The structures exposed in the lateral cranial base, after removing the coronoid and pterygoid processes, include the pterygopalatine and infratemporal fossae and the parapharyngeal space. Exposure can be extended by a frontotemporal craniotomy, which provides access to the anterior and middle cranial fossae and the basal cisterns. CONCLUSION: The upper and lower subtotal maxillectomy approaches provide wide but differing access to large parts of the central and lateral cranial base depending on the site of the osteotomies.