Expanding the endoscopic transpterygoid corridor to the petroclival region: anatomical study and volumetric comparative analysis

Abstract

OBJECTIVE The endoscopic endonasal transmaxillary transpterygoid (TMTP) approach has been the gateway for lateral skull base exposure. Removal of the cartilaginous eustachian tube (ET) and lateral mobilization of the internal carotid artery (ICA) are technically demanding adjunctive steps that are used to access the petroclival region. The gained expansion of the deep working corridor provided by these maneuvers has yet to be quantified. METHODS The TMTP approach with cartilaginous ET removal and ICA mobilization was performed in 5 adult cadaveric heads (10 sides). Accessible portions of the petrous apex were drilled during the following 3 stages: 1) before ET removal, 2) after ET removal but before ICA mobilization, and 3) after ET removal and ICA repositioning. Resection volumes were calculated using 3D reconstructions generated from thin-slice CT scans obtained before and after each step of the dissection. RESULTS The average petrous temporal bone resection volumes at each stage were 0.21 cm, 0.71 cm, and 1.32 cm (p < 0.05, paired t-test). Without ET removal, inferior and superior access to the petrous apex was limited. Furthermore, without ICA mobilization, drilling was confined to the inferior two-thirds of the petrous apex. After mobilization, the resection was extended superiorly through the upper extent of the petrous apex. CONCLUSIONS The transpterygoid corridor to the petroclival region is maximally expanded by the resection of the cartilaginous ET and mobilization of the paraclival ICA. These added maneuvers expanded the deep window almost 6 times and provided more lateral access to the petroclival region with a maximum volume of 1.5 cm. This may result in the ability to resect small-to-moderate sized intradural petroclival lesions up to that volume. Larger lesions may better be approached through an open transcranial approach.

Endoscopic endonasal transpterygoid transnasopharyngeal management of petroclival chondrosarcomas without medial extension

“…By using a limited endoscopic nasopharyngectomy by dissecting the eustachian tube, 2,9 the approach reported here provides a single-stage solution to directly accessing the entire petroclival synchondrosis, lateral cavernous sinus/Meckel's cave, posterior fossa, ventral soft tissue, and inferior aspect of Kawase's triangle. 5,6,8,9,11,15,22 As many patients present with or ultimately develop conductive hearing loss as a result of treatment (regardless of approach), this approach sacrifices the eustachian tube to maximize resection. Relative to the open and alternative endoscopic approaches, this avoids the need for facial nerve mobilization and provides direct access to bone disease without relying on medial disease extension.…”

Refining the anatomic boundaries of the endoscopic endonasal transpterygoid approach: the “VELPPHA area” concept

“…An endoscopic endonasal transpterygoid approach was performed as described in the pertinent literature. 2,6,7,9,[18][19][20][21] The surgical corridor was created by removing both middle turbinates and resecting the posterior nasal septum in order to create conditions that allow use of the endoscope and instruments through both nostrils. The medial wall of the maxillary sinus was removed to gain access to its posterior wall, which constitutes the anterior wall of the pterygopalatine fossa, and to the sphenopalatine foramen, through which the sphenopalatine artery reaches the nasal cavity; inferior turbinectomy and removal of the lateral nasal wall down to the level of the nasal floor were performed as well.…”

Acesso retrossigmoideo versus petroso posterior: análise comparativa anatomocirúrgica de duas abordagens assistidas por endoscopia à região petroclival

“…Em contrapartida aos acessos transcranianos citados anteriormente, publicações dos últimos anos atestam o esforço de se desenvolver a via transnasal endoscópica para a abordagem de lesões petroclivais (DE LARA et al, 2014;FREEMAN et al, 2018;ZWAGERMAN et al, 2016). Acessos endoscópicos estendidos, principalmente transclivais e transmaxilares, têm sido estudados para trabalhar nas três zonas petroclivais.…”

“…Outra ressalva é que, apesar do advento dos retalhos nasosseptais e do desenvolvimento de materiais sintéticos para fechamento das falhas durais decorrentes destes acessos, os índices de fístula liquórica pósoperatória ainda são consideráveis. Em investigação recente, Freeman e colaboradores postularam que lesões petroclivais com extensão lateral maior que 1,5cm 3 são melhor abordadas por vias transcranianas (FREEMAN et al, 2018).…”

“…Além da justificativa da prevalência usual, ambos permitem atingir, como enfatizado anteriormente, as três zonas petroclivais, salvaguardandose as já mencionadas restrições particulares cuja superação requer variações técnicas que, em troca da ampliação da exposição cirúrgica, exacerbam a morbidade relacionada às abordagens (ABDEL AZIZ et al, 2000;CHANG et al, 2009;GROSS et al, 2012). Desta maneira, seus alcances superam os dos demais acessos transcranianos isolados, além de superarem as óbvias limitações laterais dos acessos endoscópicos transnasais (FREEMAN et al, 2018). Embora haja argumentações arroladas por grupos que defendem prioritariamente um acesso em detrimento do outro, não há critérios claros que objetivem a escolha.…”