Anatomical Computerized Exploration to Excise Malignancies in Deep Facial Compartments: An Advanced Virtual Reality Protocol for a Tailored Surgical Approach

Abstract

Objective/hypothesis: This study describes the design and application of a novel advanced protocol for virtual three-dimensional anatomical reconstruction of the deep facial compartments, aiming to improve the preoperative understanding and the intraoperative assistance in complex resective surgeries performed for malignant diseases which extend in complex spaces, including the pterygomaxillopalatine fossa, the masticator space, and the infratemporal fossa.

Methods: This study is a non-profit, retrospective, and single-institution case series. The authors clearly describe in detail imaging acquisition protocols which are suitable to segment each target, and a multilayer reconstruction technique is presented to simulate anatomical structures, with particular focus on vascular networks. Virtual surgical planning techniques are individually designed for each case to provide the most effective access to the deep facial compartments. Intraoperative guidance systems, including navigation and virtual endoscopy, are presented, and their role is analyzed.

Results: The study included seven patients with malignant disease located in the deep facial compartments requiring radical resection, and all patients underwent successful application of the protocol. All lesions, except one, were subject to macroscopically radical resection. Vascular structures were identified with overall reconstruction rates superior to 90% for major caliber vessels. Prominent landmarks for virtual endoscopy were identified for each case.

Conclusions: Virtual surgical planning and multilayer anatomical reconstruction are valuable methods to implement for surgeries in deep facial compartments, providing the surgeon with improved understanding of the preoperative condition and intraoperative guidance in critical phases for both open and endoscopic phases. Such techniques allow to tailor each surgical access, limiting morbidity to strictly necessary approaches to reach the disease target.

Keywords: 3D vessels; deep facial compartments; navigation; virtual endoscopy; virtual surgical planning.

Figure 1

Example of multilayer anatomical reconstruction. (A) Skeletal and mucosal framework; (B) reconstruction of tumor (purple), arteries, and veins; (C) reconstruction of the parotid gland; and (D) reconstruction of masticatory muscles.

Figure 2

Virtual vascularization study conducted on three-dimensional models of arterial and venous vasculature, respectively derived from 3D TOF MR sequences and phase-contrast venography. IMA, internal maxillary artery; FA, facial artery; ICA, internal carotid artery; VA, vertebral artery; OA, occipital artery; ECA, external carotid artery; STA, superficial temporal artery; MMA, middle meningeal artery; PSAA, posterior superior alveolar artery; CS, cavernous sinus; M, maxillary vein; SS, sigmoid sinus; OV, occipital vein; RMV, retromandibular vein.

Figure 3

Preoperative definition of access portals for the PMPF: (A) anterior maxillectomy exposes the PMPF from a frontal sight, just behind the maxillary tuberosity; (B) transzygomatic approach raising a bone flap of zygomatic arch exposes the infratemporal fossa; (C) the transmandibular corridor achieved using a mandibular swing approach widens the corridor to the inferior aspect of the PMPF.

Figure 4

Multilayer anatomical reconstruction applied to endoscopic view. (A) Overview of real endoscopic scenario; (B) virtual endoscopy shows the mucosal lining and the tumor bulging around the tubaric orifice area; (C) selective hiding of the mucosa reveals the underlying tumor in relation with skeletal structures and underlying vessels; (D) tumor hiding reveals the proximity with dangerous structures, including IMA and ICA. T, tumor; Et, eustachian tube; C, choana; Pwr, posterior wall of the rhinopharynx; Cl, clivus; Ppl, pterygoid plate; LPM, lateral pterygoid muscle; IMA, internal maxillary artery; ICA, internal carotid artery; MV, maxillary vein; IJV, internal jugular vein.

Figure 5

Intraoperatively navigated sequences. STL files of virtual surgical planning are navigated during surgery, providing reference for each phase. Left, blue panel: navigation of transnasal endoscopy. Right, purple panel: navigation of transoral endoscopy.

Figure 6

Correlation between virtual endoscopy and real endoscopy using anatomical landmarks. Virtual endoscopy allows to anticipately examine the endoscopic view. pICA, paraclival internal carotid artery; SSo, sphenoid sinus opening; CS, cavernous sinus; ER, ethmoidal roof; V, vomer; Ppl, pterygoid plate; T, tumor; C, choana; IMA, internal maxillary artery.

Figure 7

Virtual surgical planning through the transmaxillary and transmandibular portal predicts the exposure of the tumor afforded by such approaches. T, tumor; LPM, lateral pterygoid muscle; Mo, maxillary opening.

Figure 8

Comparison between preoperative (A) and postoperative (B) MR shows the complete emptying of the PMPF and macroscopically radical excision of the tumor.