Comparison of two surgical approaches for petroclinic lesions

Objective:to compare the methods of petrous apical bone removal and to explore the applicable scope of Kawase approach and retrosigmoid sinus-internal auditory canal approach.Methods:one group of cadaveric head specimens simulated Kawase approach to measure the data of“Kawase triangle”,the other group simulated retrosigmoid sinus-internal auditory canal approach to measure the safety range of the grinding bone window.Then we explored the clinical indications of the two surgical approaches.Result:the grinding depth of Kawase triangle was 11.6±0.14 mm,and the range of clival exposed after grinding Kawase triangle was 22.4±1.22 mm,which could effectively expose the ventrolateral brainstem,the midline of clivus and the area above the facial acoustic nerve.The diameter of the anterior and posterior of the grinding bone window in the retrosigmoid sinus-internal auditory canal approach was 21.95±2.23 mm.In front of the exposure area were the internal carotid artery,the cavernous sinus,and the upper trigeminal nerve;the lower part was the connection between the facial acoustic nerve and the abducent nerve.Conclusion:Kawase approach is suitable for lesions of ventrolateral brainstem,middle superior clivus,with or without invasion of middle cranial fossa;the retrosigmoid sinus-superior internal auditory canal approach is suitable for lesions mainly in cerebellopontine angle area and only slightly invading Meckel’s cavity.

Endoscope-Assisted Cerebellopontine Angle Surgery

Objective To report experiences with use of otoendoscopy in cerebellopontine angle(CPA) surgeries.Methods Twenty five cases of CPA surgeries performed between November 2002 and December 2008 in which microscope enabled otoendoscopy was used were reviewed.The 25 cases included 19 cases of acoustic neuroma,3 cases of CPA facial nerve tumors,1 case of trigeminal neurinoma,a case of glossopharyngeal neuralgia and 1 case of hemifacial spasm.Endoscopy was used in all cases together with monitoring of brainstem auditory responses and facial electromyography.Postoperative hearing and facial nerve function were evaluated and compared to pre-operative levels.Results Endoscopy provided improved visualization of local anatomy,revealed hidden lesions and reduced unnecessary anatomical distortions.Total resection was achieved in 18 of the 19 acoustic neuroma cases,Facial nerve anatomical integrity was preserved in all 19 cases.One week postoperative House-Brackmann grading was I in 3 cases,Ⅱ in 10 cases and Ⅲ in 6 cases.Facial nerve function continued to improve in some cases at 3 months.Total tumor resection was achieved in all 3 patients with facial neurinoma.The facial nerve was sacrificed in 2 of the 3 cases with primary faciohypoglossal nerve anastomosis.Facial nerve function was Grade Ⅱ and Grade III one year after surgery,respectively.In the case with anatomically preserved facial nerve,postoperative facial nerve function was initially Grade Ⅲ and improved to Ⅱ at 3 months.The tumor was completely resected in the trigeminal neurinoma patient with a Grade Ⅲ postoperative facial nerve function which improved Grade II three months later.Seventeen of the 19 patients with acoustic neuroma retained hearing postoperatively,of these 12 maintained preoperative levels of hearing.Preoperative hearing capacity was preserved in 2 of the 3 patients with facial nerve tumors,but lost in patients with other tumor types.Glossopharyngeal neurotomy(n=1) and microvascular decompression(n=1) resulted in satisfactory symptom relief and no recurrence at 5-and 3-year follow up,respectively.Conclusions Otoendos aope-aided technique greatly helps surgical management of CPA and internal auditory canal lesions and other disorders.This minimally invasive technique overcomes many shortcomings inherent to the traditional retrosigmoid approach.

Keyhole approach surgery for petroclival meningioma

Background In China, the feasibility of keyhole approach in surgical treatment of petroclival meningioma has not been well evaluated. This report summarized our experience in 25 patients with petroclival meningioma who had been treated with keyhole approach surgery. Methods From July 2000 to July 2005, 25 patients with petroclival meningioma were subjected to resection via subtemporal, retrosigmoid or combined keyhole approaches. The extent of tumor resection was evaluated by MRI 3 months after surgery, and postoperative complications were investigated. Results The maximum diameter of tumors ranged from 2 to 7 cm （mean, 4.5 cm）. Gross total resection （GTR） was achieved in 14 patients, giving a GTR rate of 56%. Subtotal resection （STR） was carried out in 8 patients and partial resection in 3. Thirteen patients kept normal neurological status, whereas others suffered from cranial nerve deficits （Ⅶ, Ⅶ, Ⅲ and lower CN）. One patient died in the postoperative period. Conclusions Keyhole approach surgery, especially the combined keyhole approach is suitable for the treatment of petroclival meningioma. It provides easy and quick access to the supra- and infratentorial juxta-clival region without drilling of the petrous bone. Complications related to the approach can be minimized.

Retrosigmoid approach assisted by high-resolution computed tomography: a cost-effective technique to identify the transverse and sigmoid sinus transition

Background:When utilizing the retrosigmoid approach(RA),accurately identifying the transverse and sigmoid sinus transition(TSST)is a key procedure for neurosurgeons,especially in developing countries restricted by the lack of expensive devices,such as the neural navigation system and the three-dimensional volumetric image-rendered system.Before operations,a computed tomography scan is a common and cost-effective method of checking patients who suffer lesions located at the cerebellopontine angle.Therefore,we present a technique using only high-resolution computed tomography to identify the transverse and sigmoid sinus transition.Methods:This retrospective study included 35 patients who underwent retrosigmoid approach operations to resect an acoustic neurinoma with the assistance of our technique.In brief,our technique contains 4 steps:(1)All patients’1-mm,consecutive,high-resolution computed tomographic images that clearly displayed landmarks,such as the inion,lambdoid suture,occipitomastoid suture,and the mastoid emissary foramen,were investigated initially.(2)We selected two particular slices(A and B)among all of these high-resolution computed tomographic images in which scanning planes were parallel with the line drawn from the root of the zygoma to the inion(LZI).Slice A contained both the root of the zygoma and the inion simultaneously,and slice B displayed the mastoid emissary foramen.(3)Four points(α,β,γ,δ)were arranged on slices A and B,and pointαwas located at the inner surface of the skull,which represents the posterior part of the sulci of the sigmoid sinus.Pointβwas located at the outer surface of the skull,and the line connecting them was perpendicular to the bone.Similarly,on slice B,we labeled pointγas the point that represents the posterior part of the sulci of the sigmoid sinus at the inner surface and pointδas the point located at the outer surface of the skull,and the line connecting them was also perpendicular to the bone.The distances between pointβand the lambdoid suture/occipitomastoid suture and between pointδand the mastoid emissary foramen were calculated for slices A and B,respectively.(4)During the operation,a line indicating the LZI was drawn on the bone with ink when the superficial soft tissue was pushed away,and this line would cross the lambdoid suture/occipitomastoid suture.With both the crosspoint and the distance obtained from the high-resolution CT images,we could locate pointβ.We also used the same method to locate pointδafter revealing the mastoid emissary foramen.The line connecting pointβand pointδindicated the posterior border of the sigmoid sinus,and the intersection between the line and LZI indicated the inferior knee of the transverse and sigmoid sinus transition(TSST).Results:All 35 patients underwent the RA craniectomies that were safely assisted by our technique,and neither the sigmoid sinus nor the transverse sinus was lacerated during the operations.Conclusion:Our cost-effective technique is reliable and convenient for identifying the transverse and sigmoid sinus transition(TSST)which could be widely performed to guarantee the safety of RA craniectomy.

Original article： Removal of vestibular schwannoma and facial nerve preservation using small suboccipital retrosigmoid craniotomy

Background Vestibular schwannoma, the commonest form of intracranial schwannoma, arises from the Schwann cells investing the vestibular nerve. At present, the surgery for vestibular schwannoma remains one of the most complicated operations demanding for surgical skills in neurosurgery. And the trend of minimal invasion should also be the major influence on the management of patients with vestibular schwannomas. We summarized the microsurgical removal experience in a recent series of vestibular schwannomas and presented the operative technique and cranial nerve preservation in order to improve the rates of total tumor removal and facial nerve preservation. Methods A retrospective analysis was performed in 145 patients over a 7-year period who suffered from vestibular schwannomas that had been microsurgically removed by suboccipital retrosigmoid transmeatus approach with small craniotomy. CT thinner scans revealed the tumor size in the internal auditory meatus and the relationship of the posterior wall of the internal acoustic meatus to the bone labyrinths preoperatively. Brain stem evoked potential was monitored intraoperatively. The posterior wall of the internal acoustic meatus was designedly drilled off. Patient records and operative reports, including data from the^electrophysiological monitoring, follow-up audiometric examinations, and neuroradiological findings were analyzed. Results Total tumor resection was achieved in 140 cases （96.6%） and subtotal resection in 5 cases. The anatomical integrity of the facial nerve was preserved in 91.0% （132/145） of the cases. Intracranial end-to-end anastomosis of the facial nerve was performed in 7 cases. Functional preservation of the facial nerve was achieved in 115 patients （Grade ! and Grade ]I, 79.3%）. No patient died in this series. Preservation of nerves and vessels were as important as tumor removal during the operation. CT thinner scan could show the relationship between the posterior wall of the internal acoustic meatus and bone labyrinths, that is helpful for a safe drilling of the posterior wall of the internal acoustic meatus. Conclusions The goal of every surgery should be the preservation of function of all cranial nerves. Using the retrosigmoid approach with small craniotomy is possible even for large schwannomas. Knowing the microanatomy of the cerebellopontine angle and internal auditory meatus, intraoperating neurophysiological monitoring of the facial nerve function, and the microsurgical techniques of the surgeons are all important factors for improving total tumor removal and preserving facial nerve function.