43 Transmaxillary Approaches

43.1 Introduction

Lesions involving the clival area, the middle and posterior skull base, and the upper cervical spine represent a signifcant challenge for neurosurgeons, ENT surgeons, and maxillofacial surgeons, due to the troublesome exposure of the surgical site.

Neoplastic, degenerative or infammatory lesions can arise in this peculiar region, involving and compressing the cervi- co-medullary junction and inducing craniocervical instability.

Surgical decompression and subsequent craniocervical stabilization represent the gold standard of treatment. Although aggressive surgical resection has been advised for some of these local aggressive lesions, such as chordomas and chondrosarcomas, wide exposure of this region is difcult to obtain because of the surrounding anatomy and potential neurologic morbidity.

Multiple approaches have been described to gain adequate surgical exposure. The choice of the correct surgical approach depends on several factors, such as patient’s age and general health condition, tumor histopathology, extension and growth rate, and the exact location of the lesion.

Four diferent broad categories of surgical techniques have been proposed in literature: open-transfacial, microsurgical, endoscopic, and robotic techniques provide all good visualization of this hard-to-reach anatomical area, each one of them obviously showing defnite pros and cons.

In particular, the Le Fort I transmaxillary approach and the following downward displacement of the maxilla provides a wide exposure of the posterior nasopharynx, from the sphenoid sinus to the clivus and the anterior part of the foramen

magnum. This technique allows obtaining an acceptable cra- nio-caudal exposure of the clival and paraclival region, associated to a reduced lateral vision.

43.2 Indications

•Neoplastic, degenerative or infammatory lesions involving the clival area, the middle and posterior skull base and the upper cervical spine.

43.3 Patient Positioning

•Position: The patient is positioned supine with the head fxed on a horseshoe head holder.

•Body: The trunk and the head are slightly elevated to facilitate the venous backfow.

•Head: The head is placed in neutral position.

•Neck: The neck is slightly extended (about 20°), to facilitate further brain relaxation after dural opening.

•Intubation: Submental orotracheal intubation. (Fig. 43.1).

43.4 Mucosal Incision (Fig. 43.2)

•Mucoperiosteal incision is performed at the superior vestibular fornix of the oral cavity.

•Incision is carried out 1 cm above the gingival refection, along the upper alveolar margin between the bilateral frst molars.

Fig. 43.1 Submental orotracheal intubation.

Abbreviations: SMI = submental incision; VT = ventilation tube.

Fig. 43.2 Mucosal incision.

Abbreviations: C = chin; FT = frontal teeth; G = gingiva; T = tongue.

43.4.1 Critical Structures

• Branches of the superior alveolar artery.

43.5 Soft Tissue Dissection

•Pericranial layer

○A subperiosteal dissection of soft tissues is carried out using an elevator instrument.

•Bone exposure

○Bone exposure is accomplished through the exposure of the anterior wall of the maxilla, the piriform aperture, the infraorbital foramen and the infraorbital nerve at the exit of its canal.

○Then, the surgeon must detach the cartilaginous portion of the nasal septum from the nasal spine and the vomer

(Figs. 42.3, 43.4).

43.6 Osteotomy (Figs. 43.5, 43.6)

•Osteotomy has to be performed 1 cm above the teeth roots, using an oscillating saw or the piezosurgery.

•In order to avoid postoperative loss of individual occlusion, premodeling of 4 miniplates on both sides is accomplished.

At the end of surgery, exact position of the maxilla is guaranteed by replacing the premodeled plates by screws insertion in the previous driven holes.

Fig. 43.3 Cartilaginous portion of the nasal septum are detached from the nasal spine and the vomer. Abbreviations: ANS = anterior nasal spine; CF = canine fossa;

FT = frontal teeth; G = gingiva; NM = nasal mucosa; NP = nasal piriform aperture.

Fig. 43.4 Osteotomy, landmarks.

Abbreviations: ANS = anterior nasal spine; AP = alveolar processes; CF = canine fossa; IOF = infra-orbital foramen; MSAW = maxillary sinus anterior wall; NP = nasal piriform aperture.

Fig. 43.5 Osteotomy, step 1.

Abbreviations: AP = alveolar processes; FT = frontal teeth; G = gingiva; MSAW = maxillary sinus anterior wall; NM = nasal mucosa; NS = nasal septum.

•Once the osteotomy has been performed, the nasal septum can be separated from the maxilla and the pterygoidmaxillary junctions divided with a curved chisel.

•The maxilla will be displaced downward, preserving the palatine vessels and nerves.

Fig. 43.6 Osteotomy, step 2.

Abbreviations: AP = alveolar processes; FT = frontal teeth; G = gingiva; MS = maxillary sinus; MSAW = maxillary sinus anterior wall; NM = nasal mucosa; NS = nasal septum.

•The surgeon has now to expose and remove the nasal septum and vomer.

•Once the sphenoidal rostrum is reached, the sphenoid sinus is reached.

•Incision of the pharyngeal mucosa and dissection of the pharyngeal muscles allows exposure of the clivus from the sella to the anterior border of the foramen magnum (Fig. 43.7).

•Osteotomy landmarks

Anatomical landmarks which have to be take into consideration in designing the osteotomy are as follows:

○Superiorly: Piriform aperture, the infraorbital foramen and the infraorbital nerve at the exit of its canal.

○Inferiorly: Alveolar processes.

○Laterally: Maxillary tuberosity.

○Medially: Cartilaginous portion of the nasal septum from the nasal spine and the vomer.

43.7 Variants

43.7.1 Le Fort I Transmaxillary Approach with a Transantral and Transpterygoid Approach

(See Chapter 44)

•Following removal of the middle and inferior turbinates and opening of the maxillary antrum, the posterior wall of the maxillary sinus can be removed, reaching the pterygopalatine fossa, where noble neurovascular structures can be identifed and mobilized.

•A further lateral exposure can be obtained with the removal of the pterygoid plates and the dissection of pterygoid muscles.

Fig. 43.7 Microscopic view of clival exposure. Abbreviations: AP = alveolar process; C = clivus; G = gingiva; ICA = internal carotid artery; MPW = maxillary posterior wall;

OM = oral mucosa; PPF = pterygopalatine fossa; S = sella; SS = sphenoid sinus;

TT = torus tubarius; UL = upper lip.

43.7.2 Splitting of Soft Palate and/or Tongue

Le Fort I osteotomy can be coupled with splitting of soft palate and/or tongue in order to grant further specifc vertical widening of the surgical feld.

•The split of the soft palate allows accessing the lower clivus, the craniocervical junction, C1 and C2.

•It must be noted that the soft palate split requires a precise reconstruction of each layer in order to avoid velo-pharynge- al incompetence.

•Splitting the tongue allows further caudal extension of the surgical feld, down to C3 and C4.

•No movement alterations have been described in the literature, being the residual damage after healing even less than in cosmetic tongue splitting, the incision must be strictly kept on the median line in order to avoid peripheral neuropathies.

43.8 Pearls

•It is worth noting that submental orotracheal intubation, usually employed during cranio-maxillofacial traumas treatment, can be used as a safe technique for airway management during transfacial approaches to the cranial base.

•It avoids the complications associated with tracheostomy.

•It also permits considerable downward retraction of the maxilla after a Le Fort I osteotomy and is associated with good clival exposure.

•Furthermore, it does not interfere with maxillo-mandibular fxation at the end of the surgery.

43.9 Reconstruction

Transfacial approaches also have a distinct and useful role in the repair of large breaches of the cranial base, since they allow enough feld exposure to grant the use of local and pedicled faps.

Proactive repair of large cranial base defects directly improves patient survival and surgical success rate preventing infections, ocular functional issues and distortion of facial morphology. Since a complete coverage of cranial base defects goes beyond the scope of this book, detailed information can be found in other Thieme references.

References

1.Biglioli F, Mortini P, Goisis M, Bardazzi A, Boari N. Submental Orotracheal Intubation: An alternative to tracheotomy in transfacial cranial base surgery. Skull Base 2003; 13(4):189–195.

2.Boari N, Roberti F, Biglioli F, Caputy AJ, Mortini P. Quantifcation of clival and paraclival exposure in the Le Fort I transmaxillary transpterygoid approach: a microanatomical study. J Neurosurg 2010;113(5):1011–1018.

3.Hernández Altemir F. Transfacial access to the retromaxillary area. J Maxillofac Surg 1986;14(3):165–170.

4.Liu JK, Couldwell WT, Apfelbaum RI. Transoral approach and extended modifcations for lesions of the ventral foramen magnum and craniovertebral junction. Skull Base 2008;18(3):151–166.

5.Williams WG, Lo LJ, Chen YR. The Le Fort I-palatal split approach for skull base tumors: efcacy, complications, and outcome. Plast Reconstr Surg 1998;102(7):2310–2319.