Anatomical Study And Clinical Application Of The Temporal Base Transpetrosal Transtentorial Approach To Petroclival Region

Part I Microsurgical Anatomy of Petroclival RegionObjective: To explore the way to locate the important anatomical structures of temporal bone and petroclival region to gain the orientation regarding with temporal base transpetrosal transtentorial approach.Materials and methods: Ten dried skulls for a total of 20 sides were used to explore the morphometric relationships with ×2 to ×16 magnification. The anatomical relationships and the distance among the external auditory foramen, foramen lacerum, hiatus canalis facialis, internal auditory foramen, internal carotid canal, cochlea, semicircular canal and the adjacent bone structures were studied and measured.Results: The distance between the anterior border of the external auditory foramen and the root of zygoma, superior border and the bone tuberositas above external auditory foramen, posterior border and the anterior angle of parietomastoid sutures, were 13.80±1.33mm, 6.18±1.20 mm , and 26.18±3.90mm; the distance between the foramen lacerum and the zenith of arcuate eminence, or the petrous apex impression by trigeminal nerve were 32.74±1.79mm and 6.62±1.66 mm; the distance between the hiatus canalis facialis and petrous ridge was 11.79±1.00 mm; the distance between posterior border of the internal auditory foramen and the zenith of the arcuate eminence was 14.56±3.48 mm. The location of the internal auditory canal was on theangular bisector of the angle form by the arcuate eminence and the nervus petrosus superficialis major. The gap from the common crus to posterior border of the internal auditory foramen was 9.30±0.58mm; from cochlea to petrous ridge was 8.00± 1.07mm; from the posterior semicircular canal to the petrous ridge was 4.30±0.60 mm; and from the internal carotid canal to the petrous ridge was 10.47±1.34 mm.Conclusions: The external auditory foramen can be located by the root of zygoma, the bone tuberositas above external auditory foramen and the anterior angle of parietomastoid sutures. To avoid injurying of the geniculater ganglion and the genu of facial nerve, the dura of the front petrous bone should be dissect within the boundary formed by the hiatus canalis facialis,which is about 11.79±1.00 mm from the petrosal ridge. When resectting the petrous bone above the internal carotid canal, the cochlea and the semicircular canal in the temporal base transpetrosal transtentorial approach to the petroclival region, the depth should be less than 10mm, 8mm and 4mm respectively. Part II Microsurgical Anatomy of the vein of Labbé and Locating vein of Labbé by CTVObjective: The anatomical shape and location of the the vein of Labbé were investigated to protect this vein during temporal base transpetrosal transtentorial approach, and the CTvenography (CTV) was used to identify and locate the the vein of Labbé preoperation for the apply of the temporal base transpetrosal transtentorial approach.Materials and methods: Ten cadaver heads for a total of 20 sides wereexamined, using ×2 to ×16 magnification after perfusing the arteries and veins with colored latex. The anatomical shape of the the vein of Labbé and the distance between the endpoint of the the vein of Labbé and STP (the conjunction of the transverse sinus, sigmoid sinus and superior petrosal sinus) were noted. 5 volunteer and 7 patients with tumor in petroclival region received CTV examination to investigate the shape and locating of the vein of Labbé before operation. The outcome of the CTV examination for the vein of Labbé was checked by the operation.Results: The vein of Labbé can be divided into three configurations, including single independent type 40%(8 sides), double indepentend type 35%(7 sides) and multiple indepentend type 20%(4 sides). The distance between the terminations of the the vein of Labbé and STP was 22.91±8.09mm, with less than 10mm in 10%. The shape of the vein of Labbé displayed by CTV was clear and same as the shape displayed in operation, and the distance between the terminations of the vein of Labbé and STP measured by CTV was also same with the value measured in the operation.Conclusions: The vein of Labbé is believed to be the most important vein in the temporal base transpetrosal transtentorial approach, for the location of the vein of Labbé can greatly effect the degree of the temporal base retraction. "Anterior drainage of the vein of Labbé" is a special type of the vein of Labbé, which will significantly limited the temporal base retraction or operative exposure, and the temporal base transpetrosal transtentorial approach is not suitable to be applied in this situation. Comparing with MRV and DSA, CTV examination can locate the vein of Labbé more easily and exactly preoperation, and it should be performed and scrutinized carefully before planning the temporal base transpetrosal transtentorial approach.Part III Applied Anatomical Study of the Temporal Base Transpetrosal Transtentorial ApproachObjective: To explore the anatomical structure and identify the "safe resecting region" in the temporal base transpetrosal transtentorial approach, and compare the extended exposed area in the temporal base transpetrosal transtentorial approach with that in the temporal base transtentorial approach.Materials and methods: Ten adult cadaver heads for a total of 20 sides were firstly performed by the temporal base transtentorial approach, and the microsurgical anatomy and the exposed field of this approach were examined. Then the temporal base transpetrosal transtentorial approach was simulated and identify the "safe resecting region" in this approach. The area which cann't be observed in the temporal base transtentorial approach was evaluated in the temporal base transpetrosal transtentorial approach. All specimens received ultrathin-slice CT scan when the temporal base transpetrosal transtentorial approach were completed in one side to compare the angle of temporal base retraction when exposing the same structure of petroclival region in the two approaches.Results: To resect the petrosal bone safely, the petrosal bone can be divided into three parties by the internal acoustic canal including the medial, intermediate and lateral part in the temporal base transpetrosal transtentorial approach. In the medial part, after resecting 5mm deep petrosal bone above the internal acoustic canal, the roof of the internal acoustic canal will be exposed; and after resecting 8mm wide petrosal bone, the bottom of the internal acoustic canal can be nearly reached. In the intermediate part, the distance between the internal carotid artery in the petrosal bone and petrosal ridge was 10.47 ± 1. 34mm, the cochlea and petrous ridge was 8.00±1.07mm. In the lateral part, the distance between the common crus and petrosal ridge and posterior border of the internal auditory foramen were 4.30 ± 0. 60mm and 9.30±0.58mm. By resecting the petrosal bone which hinder the visual field of the most part of thethe petrosal bone's posterior surface, the part of CNVI entering doller's hole, the part of CNVII-VIII and anterior inferior cerebellar artery entering the internal acoustic canal, the region near the petroclival fissure and the internal acoustic canal can be totally exposed in the temporal base transpetrosal transtentorial approach. Further more, after deleted the hindrance of the petrosal bone in this new approach, the angle which the temporal base need to be retracted to for exposing the inferior area of the internal acoustic foramen and the middle area of the mesencephal were about 24.5±4.59° and 0°, while in the temporal base transtentorial approach these were 66.5±6.53° and 10° respectively.Conclusions: There still exists blind area of the posterior surface of the petrosal bone which is dodged by the petrosal ridge in the temporal base transtentorial approach. The temporal base transpetrosal transtentorial approach can significantly improve the visual field above-mentioned and reduce the degree of the temporal base retraction. The safe area when resecting petrosal ridge can be divided into three parts: the medial part is about 15mm(length) × 8-10mm(width), the intermediate part is about 8mm(length) × 5mm(width) × 2-5mm(depth), and lateral part is about 9mm(length) × 5mm(width). Part IV Temporal Base Transpetrosal Transtentorial Approach to the Meningioma in Petroclival regionOBJECTIVE: To investigate temporal base transpetrosal transtentorial approach for the meningioma in petroclival region.METHODS: The clinical data of 21 consecutive patients with the tumors, including 14 meningioma and 7 trigeminal neurinoma in petroclival region (bestriding middle and posterior fossae), operated with the temporal basetranspetrosal transtentorial approach or the temporal base transtentorial approach from March 2002 to February 2006, were reviewed.RESULTS: To the trigeminal neurinoma, gross total resection (GTR) were achieved in all 7 patients (100%). To the meningioma, SimpsonI resection were achieved in all 4 patients in the temporal base transpetrosal transtentorial approach; in the temporal base transtentorial approach, SimpsonII resection were achieved in 6 patients (66.7%) and subtotal total resection (STR) in 3 patients (33.3%), but no patients get SimpsonI resection in this approach. Patients have been followed up for 2-48 months (mean 21.1 months). The postoperation neurological deficits in the patients with petroclival meningioma consisted of two patients facial numbness (16.6%), two patients diplopia (16.6%). All 4 patients who received the temporal base transpetrosal transtentorial approach recover well postoperatively, they have lived independent and resumed their occupation now. In the patients who received the temporal base transtentorial approach, 3 patients postoperative neurologic status deteriorated, 2 of them improved after theraphy, and 1 patient died 13 months after operation for the reason of the deadly pneumonia, and the mortality was 8.3%. To the tumor received SimpsonII resection, following-up MR imaging revealed no evidence of tumor recurrence till now, and to the tumor received STR, the residual tumor didn't get larger in the most recent follow-up visit.CONCLUSION: The temporal base transtentorial approach can eliminate the visual hindrance by the petrosal redge, and resect the base of the petroclival meningioma to achieve the SimpsonI resection. This new approach is effective and can get the satisfied therapy outcome for the petroclival meningioma...