The Anatomical And Clinical Study Of Posterior Petrous Meningiomas

PartⅠ:The Anatomical Study of the Presigmoid Transpetrosal ApproachBackgroundSurgical resection of the petroclival tumors is extremely difficult because of their deep site and complicated neurovascular structures that surrounds them. How to achieve the total resection and decrease mortality and disability rate is still one of the difficulties of neurosurgery.Recently,the presigmoid transpetrosal approach has received considerable attention,and believed as one of the basic approaches to the petroclival region.The presigmoid transpetrosal approach is invented by Hakuba in 1977 and developed by AL-Mefty,Samii. According to the amount of the petrous bone resected,the presigmoid transpetrosal approach can be typically divided into three variations,including the retrolabyrinthine approach,the translabyrinthine approach and the transcochlear approach.Comparied with the retrosigmoid approach,there are some advantages such as shortening the distance to the tumor,enlarging the visible and operating space,dealing with the middle and posterior fossor tumor directly and stopping the blood supply of the tumor base earlier.ObjectiveThe goal of the anatomic study was to expore the anatomical features and technique of the presigmoid transpetrosal approach,to compare the two variations(the retrolabyrinthine approach and the translabyrinthine approach) typically used in the presigmoid transpetrosal approach.Study its anatomy and supply anatomical basis for its clinical application.MethodsTen adult cadaver skulls were drilled out both the surface bone of the mastoid and the mastoid cells according the presigmoid transpetrosal approach.Then outline the bone labyrinthine.Measure the distance between relevant bone marks and function structures such as the PSC to the sinodural angle,the top point of SSC to the superior margin of sigmoid sinus,the inferior margin of the external auditory canal to the jugular bulb and the width of the three semicircular canals.All the data were analyzed statistically and expressed as mean.Three 10%formaldehyde fixed cadaveric adult heads whose arterieshad been injected with red latex for artery and blue for vein.Three typically using variations of presigmoid transpetrosal approach were stimulated on both sides of each cadaver heads with microscope.Study the local anatomic structure and the exposed scope.Results1.The distance between posterior margin of the PSC and the sinodural angle was 19.73±3.38 mm(left side) and 17.98±2.45 mm(right side).The distance between posterior margin of the PSC and the suprameatal spine was 18.65±2.24 mm(left side) and 17.36±1.86 mm(right side).The distance between posterior margin of the PSC and the surface of the mastoid was 15.27±2.15 mm(left side) and 14.22±2.65 mm(right side).The distance between posterior margin of the PSC and the posterior margin of the internal acoustic pore was 1086±1.86 mm(left side) and 11.56±2.15 mm(right side).The distance between top point of SSC and the superior margin of sigmoid sinus was 24.62±2.22 mm(left side) and 23.80±2.30 mm(right side). The width of the SSC was 11.01±0.80mm(left) and 10.25±0.78mm(right). The width of the PSC was 10.61±1.69 mm(left) and 10.27±1.65 mm(right). The width of HSC was 11.27±0.89 mm(left) and 10.65±0.90 mm(right). The length of mastoid segment of the facial canal was 12.64±2.11 mm(left) and 13.12±1.35 mm(right).2.It can be exposuredⅤ,Ⅶ,Ⅷ,Ⅸ,Ⅹ,Ⅺcranial nerves,superior cerebellar artery,the cerebellopontine angle region and jugular foramen through the retrolabyrinthine approach.The ports and the lateral part of the medulla and the initial segment ofⅤ,Ⅶ,Ⅷ,Ⅸcranial nerves can be exposured according to the the translabyrinthine approach.It can be reached the whole part of the posterior petrous bone and the middle clivus.Conclusions1.Drilling out the petrous bone is the key point of the PTA.Localizing PSC and facial canal tube precisely might prevent them from being damaged and assist our surgeons in operating.The distance between relevant bone marks according to the presigmoid approach can give a guideline of drilling out the petrous bone and protecting the important structures.2.The retrolabyrinthine approach with the advantage of preserve hearing provided a limited exposure of petroclivus.It should drill out the bone as much as possible to enlarge the exposure below the premise of protection of the bone labyrinthine and the facial canal.The translabyrinthine approach can directly reach the whole posterior surface of the petrous bone and the middle clivus except the petrous apex.We can get a satisfied exposure with this approach but must destroy the hearing. PartⅡ:Diagnosis and Microneurosurgery for Petrous MeningiomasBackground:Posterior fossa meningioma,with the incidence of 9%intracranial meningiomas,can be divided into five types by Castellano according to basal part of the tumor:convex cerebellar meningioma,tentorium meningiomas, meningioma of the posterior petrous bone,petroclival meningiomas and the foramen magnum meningiomas.During the past years,all tumors which locating at cerebellopontine angle region were named cerebellopontine angle meningioma regardless of the meningiomas basement and this can not describe basal part of the tumor accurately.Basement of meningioma of the posterior petrous bone locates at the petrous bone dural surface with the incidence of 42% in the cerebellopontine angle meningioma,which is characterized mainly by the cranial nerve injury and cerebellar symptoms.In this report we described 42 patients with meningioma of the posterior petrous bone confirmed by surgery and pathology in department of neurosurgery,Qilu Hospital,Shandong University.Posterior petrous meningiomas was the tumors which arising from the posterior surface of the petrous bone and excluding the other original tumor of the CPA,such as the tentorium meningiomas,transverse sinus meningiomas and jugular foramen meningiomas et al..Posterior surface of the petrous bone was the region which like a ring that surrounding by superior petrosal sinus, inferior petrosal sinus and sigmoid sinus.In the past,posterior petrous meningiomas were reported just as a part of the CPA meningiomas.As the development of the neurosurgery,more details are needed for the surgeons.So it is necessary to study the posterior petrous meningiomas systemically and we can get more information about the most important part of the CPA meningiomas.ObjectiveTo improve the diagnosis and treatment of posterior petrous meningiomas,the characteristics of epidemiology,clinical manifestation,radiological features, diagnosis and differential diagnosis,surgical skills,postoperative complications and final outcome of patients with posterior petrous meningiomas are described.Methods:42 patients with posterior petrous meningiomas which were hospitalization and treatment in Department of Neurosurgery,Qilu Hospital of Shandong University combining with the literature.According to the clinical manifestations and radiological images,posterior petrous meningiomas were classified into three types:Cerebella type,the tumor involved with and compressed cerebellum;Cranial nerve type,the tumor involved with the cranial nerves;Combined type,the tumor involved more than one structure such as the cerebellum,cranial nerves,brain stem et al.Results:42 patients,of which seven are male,35 are female,aging from 34 to 70 with the average 51 years old were involved in our study.All patients have been present meningioma of the posterior petrous bone for from 10 days to 10 years, in which 18 occurred on the left side and 24 right side.Common clinical symptoms were headache,hearing loss,tinnitus,unsteadiness and facial numbness.All the meningiomas were resected with microsurgical techinique.As a result,total removal of tumour was achieved in 38 cases and subtotal in 4 cases.No death occurred perioperatively.Postoperatively,the rate of anatomical preservation of facial nerve was 90%and function preservation was 86%; hearing preservation achieved 76%.All cerebella type tumors were completely resected via the suboccipital retrosigmoid approach.The rate of anatomical and functional preservation of facial nerve was 100%and hearing preservation rate achieved 100%.Among these cases,one had a transient decrease in hearing.In patients with cranial nerve type tumors,13 cases underwent resection via the suboccipital retrosigmoid approach and 3 cases via the presigmoid approach. Patients in 14 cases underwent total resection,and in two subtotal resection. Three cases experienced seventh nerve paralysis,whereas six patients suffered hearing decrease.The rate of anatomical preservation of facial nerve was 87.5% and functional preservation was 81%.In patients with the combined type tumors, 13 cases underwent resection via the suboccipital retrosigmoid approach and one case via the presigmoid approach.Patients in 12 cases underwent total resection,and in two cases subtotal resection.Three cases experienced seventh nerve paralysis,whereas four patients suffered hearing decrease.The rate of anatomical preservation of facial nerve was 86%and functional preservation was 78%.Conclusions:1.The main location of the posterior petrous meningiomas is the CPA.The most common presenting symptoms were caused by the damages of cerebellum and cranial nerves.The clinical manifestations vary with the different types and the structures involved by tumors.2.It is more difficult for cranial nerve type and combined type tumors to be resected than cerebella type lesions and the postoperative functional outcomes are significantly worse.3.Microsurgical techniques and skills are critical to increase total resection rate of tumor and decrease mortality and disability rate.