Transpetrosal Approach Research Articles

Complications of posterior cranial fossa surgery—an institutional experience of 500 patients

Background The complication of the posterior fossa surgery is seldom described in the literature. The purposes of this retrospective study are to draw attention to the potential complications associated with posterior fossa surgery and to critically review the predisposing factors that might influence the complication rate. Methods We undertook a 10-year (1992-2002) retrospective study of all posterior fossa surgery performed at LSUHSC. A total of 500 patients were obtained from the operation database, and they were categorized into 5 groups based on the surgical approaches: (1) cerebellopontine angle lesion, (2) microvascular decompression for facial pain and spasm, (3) cerebellar lesions, (4) Chiari I decompression, and (5) petroclival lesions. Data collected for analysis included patient demographics, pathological characteristics of the lesions, and the postoperative complications that occurred as unexpected and undesirable events that prolonged hospital stay and may require surgical/medical intervention. Results Of the 500 patients reviewed, 220 (44%) patients had tumor resections at the cerebellopontine angle; 110 (22%) patients had microvascular decompression for trigeminal neuralgia and hemifacial spasm; 86 (17.2%) patients had cerebellar lesions; 60 (12%) patients had Chiari I decompression; and 24 (4.8%) patients required transpetrosal approaches for petroclival lesions. The overall complication rate in our study was 31.8%, affecting 159 patients. Cerebrospinal fluid leaks were the most frequently encountered, presenting in 65 (13%) patients followed by meningitis in 46 (9.2%) patients, wound infection in 35 (7%) patients, and CN palsies in 24 (4.8%) patients. Other complications that were observed to develop almost exclusively in patients undergoing cerebellar parenchymal tumor resection included cerebellar edema in 25 (5%) patients, hydrocephalus in 23 (4.6%) patients, cerebellar hematoma in 15 (3%) patients, and cerebellar mutism in 6 (1.2%) patients. The overall mortality rate related to surgery was 2.6% occurring in 13 patients. Conclusion Posterior fossa surgery involves greater morbidity and mortality and has a wider variety of complications than surgery in the supratentorial compartment. These complications may be avoided by careful perioperative planning, strict adherence to aseptic technique, meticulous microsurgical dissection, proper wound closure, and the judicious use of prophylactic agent. A thorough understanding of the patient's history, neurological findings, imaging studies, operative anatomy, as well as all potential adverse events associated with the procedure is also essential to minimize complications.

Cavernomas pontinos extraventriculares. Parte II. Acesso pré-sigmoideo transpetroso a cavernoma pontino ventrolateral

Resumo Objetivo: Descrever a via pré-sigmoidea ampliada para acesso a lesões localizadas na região ventrolateral da ponte, exemplificado com a apresentação de um caso de cavernoma pontino nessa localização. Conclusão: Esse acesso, amplamente revisto pela literatura, é útil para remoção cirúrgica de cavernomas pontinos ventrolaterais.

Abducens nerve schwannoma mimicking intrinsic brainstem tumor

Schwannomas of the abducens nerve are extremely rare tumors affecting cavernous, cisternal or both segments of sixth cranial nerve. Clinical features and neuroradiological imagery are frequently insufficient to reach an accurate pre-operative diagnosis. We report a patient with a cystic tumor with ring-like contrast enhancement at the right anterior pontomesencephalic junction. Radical excision was performed via anterior transpetrosal approach and showed an extrinsic tumor originating from the sixth nerve. A postoperative sixth nerve palsy had disappeared completely 9 months after the surgery. The correct diagnosis of an abducens nerve schwannoma is established by the intraoperative finding of a tumor attachment to the sixth nerve and by histopathological analysis. The various differential diagnoses, the clinical and radiological features of this diagnosis and management are issues discussed in this illustrated review.

Transpetrosal approach: an anatomical study of temporal bone

Resection of the petrous temporal bone to various degrees provides different levels of access to lesions of the posterior fossa. However, regarding the numerous variations, precise distances of petrosal bone are not still clearly described. This may lead to serious complications during transpetrosal surgeries. Our objective was to evaluate different distances of temporal bone landmarks in order to assess their variations and the possible correlations between them. This anatomical study was performed on 60 temporal bones from 60 human cadavers in the years 2006 and 2007. All the bones contained an adequate portion of the petrous apex and attached fossa dura. Twelve landmarks were defined and 27 different distances were measured for each temporal bone using two-point caliper. Less variation was observed in the superoinferior diameter of horizontal carotid canal with the less coefficient of variation (CV) of 9.29; whereas, the most variation was detected in the inferior (axial) plane of posterior semicircular canal to superior plane of jugular bulb (CV = 57.65). There was a significant correlation between vertical intratemporal diameter of carotid in pyramidal direction, and superior-inferior diameter of horizontal carotid canal (r (Pearson) = 0.500, P < 0.001). Other significant correlations were also found between other distances. The variations of different distances and landmarks were evaluated and many significant correlations were demonstrated between them which could potentially aid ENT specialists and neurosurgeons in order to approach anatomical landmarks and cranial fossas more safely during otologic and neurotologic surgeries. It could also help the design of middle ear prosthesis.

Applied anatomical study of the temporal base transtentorial transpetrosal approach

Objective To explore the resecting region of the petrosal bone and the extended exposed area in temporal base transpetrosal transtentorial approach(TBTTA).Method Ten adult cadaver heads for a total of 20 sides were performed by TBTTA and the resecting region of the petrosal bone was identified in this approach.The exposure at petroclivus and the angle of temporal base retraction was evaluated in TBTTA approach.Results The petrosal bone can be divided into three parties by the internal acoustic canal.In the medial part,the drilling area was 6.6 mm wide and 5 mm long above the internal acoustic foramen(2 mm long above the bottom of internal acoustic canal).In the intermediate part,the safe drilling area was 15 mm long and 9 mm wide.In the lateral part,the resecting area between the internal auditory canal and semicircular canals was 8.7 mm long and 5 mm wide:and in the area of semicircular canals,the drilling deep should be restricted within 3.7 mm.After resecting the petrosal bone which block the visual of the most part of the pefrosal posterior wall,the exposed area was obviously enlarged,and the temporal base retracting angle reduced.Conclusions TBTTA approach can significantly improve the visual field in the petroclival region and reduce the degree of the temporal base retraction by resecting petrosal ridge. Key words: Temporal base transtentorial transpetrosal approach(TBTTA); Petroclival region; Surgical procedures,operative

Trans-sylvian transtentorial approach for skull base lesions extending from the middle fossa to the upper petro-clival region

Various transpetrosal approaches have been described for excision of lesions extending into both the midlle fossa and the upper petroclival region. These approaches may be associated with significant morbidity. Six patients with lesions along the medial part of the middle fossa and the upper petroclival region were operated by the trans-sylvian transtentorial approach. The surgical corridor was along the tentorial edge with excision of the tentorium providing adequate access to the tumour without the need for petrosectomy. Three patients had a trigeminal schwanomma, one each had a petroclival meningioma, clival chordoma and an epidermoid tumour. In 5 patients a total/neartotal excision was achieved while in one patient with petroclival meningioma, a subtotal excision was possible. All patients improved clinically after the surgery. There was no procedure related morbidity. The transsylvian transtentorial approach provides adequate acces to upper petroclival lesions allowing the tumours in this region to be removed without the need for a petrosal resection.

Effects of using combined transpetrosal surgical approaches to treat petroclival meningiomas

Effects of using combined transpetrosal surgical approaches to treat petroclival meningiomas

Surgical and Histological Observations of Trochlear Neurinoma -Case Report-

A 47-year-old woman presented with an extremely rare case of trochlear nerve neurinoma manifesting as left hemiparesis. Magnetic resonance imaging demonstrated a cystic tumor, 4 cm in diameter, in the right ambient and cerebellopontine cisterns, compressing the midbrain and upper pons. The preoperative diagnosis was trigeminal neurinoma. However, the tumor was identified arising from the trochlear nerve, and was totally removed via the posterior transpetrosal approach. The histological diagnosis was neurinoma. The patient's hemiparesis improved postoperatively. Preoperative diagnosis of trochlear neurinoma must distinguish the neurological presentations of trochlear and trigeminal neurinomas and to analyze the microanatomy of the tumor and skull base structures on neuroimaging.

Transzygomatic extended middle fossa approach for upper petroclival skull base lesions

Central skull base lesions in the upper retroclival and petroclival regions can be challenging to access because of their location anterior to the brainstem. Several transpetrosal approaches have been developed to access the petroclival junction, including anterior petrosal (anterior petrosectomy), posterior petrosal (retrolabyrinthine, translabyrinthine, transcochlear), and combined petrosal approaches. The anterior petrosal approach is best suited for upper petroclival lesions located anterior and superior to the internal auditory canal and superior to the inferior petrosal sinus. This approach provides direct access to the anteromedial cerebellopontine angle, petrous apex, Meckel cave, and ventrolateral brainstem between the trigeminal root and the facial nerve. The authors describe their modification of an anterior petrosal approach, the so-called transzygomatic extended middle fossa approach, which incorporates a zygomatic osteotomy, anterior mobilization of the V3, and extensive middle fossa drilling. This exposure provides a wider surgical corridor for direct view of the clivus and ventral brainstem.

Modification of three-dimensional prototype temporal bone model for training in skull-base surgery

Experience with dissection of the temporal bone is essential for training in skull-base surgery, but only a limited number of neurosurgical residents have the opportunity of cadaver dissection. A modification of a commercially available prototype three-dimensional (3D) temporal bone model is proposed to include artificial dura mater, venous sinuses, and cranial nerves for such surgical training. The base 3D temporal bone model incorporates the surface details and the inner ear structures and air cells. Model dural sinuses and dura mater made from silicone, cranial nerves made from rubber fibers, and internal carotid artery made from rubber tubes were added to the model. Posterior petrosectomy (transpetrosal approach) and transcondylar approach were performed on this model using a high-speed drill and ultrasonic bone curette under an operating microscope. The modified 3D temporal bone model provided good experience with the complicated 3D anatomy. The model could be dissected, and the dural sinuses and dura mater preserved by the eggshell peeling technique in almost the same way as real temporal bone. The modified 3D temporal bone model provides a good educational tool for training in skull-base surgery.

Tumors Originating from Meckel's Cave

There has been little literature about tumors originating from Meckel's cave until now. Also, surgical opening strategies of Meckel's cave have not been well discussed. We analyze the cases of Meckel's cave tumors operated in Keio University Hospital since 1986.We have experienced 35 cases of Meckel's cave tumors, 22 cases of neurinoma, 9 cases of meningioma, 1 case of hemangiopericytoma, 2 cases of epidermoid, 1 case of dermoid. We classified Meckel's cave tumors according to Samii's classification. We experienced 3 cases of Type 1, 7 cases of Type 2, 9 cases of Type 3, 16 cases of Type 4. The tumors of Type 1 and Type 2 were operated by using the anterolateral approach (Dolenc's approach). Types 3 and 4 were treated by lateral approach (anterior transpetrosal approach). In cases of large tumors classified in Type 4, combined zygomatic osteotomy should be performed to reduce retraction damage. Benefits of those methods are that they open the Meckel's cave completely with minimal retraction damage to the bridging veins and cranial nerves, by epidural or interdural access to the tumors. The influential factor for total tumor removal was whether the tumors invaded the cavernous sinus.

Anterior Transpetrosal Approach to Petroclival Meningiomas

The best approach to petroclival meningiomas provides a wider exposure with decreased distance to the target and also minimizes brain retraction. For tumors located at the upper third of the clivus, a subtemporal approach with selective resection of the anterior part of the petrous pyramid offers a surgical field of the parasellar area, upper clivus, and the cerebellopontine angle. The extradural bone work serves to improve the exposure of the area in front of the upper brainstem from the intradural subtemporal route. Of the 87 cases of petroclival (premeatal) meningiomas operated in our institute from January 1990 until February 2008, 25 patients were operated through an anterolateral/lateral (subtemporal/anterior traspetrosal ) route with an operative mortality of 7%. While the tumor resection was carried out through a combined posterior subtemporal/pre- or transsigmoid (posterior petrosal) in 22 cases (26%), it was through a retrosigmoid supraparacerebellar route in 35 cases (40%). In three cases with extracranial extension to the infratemporal area, a modified Fisch approach was used. An operative video of the anterior transpetrosal approach will be presented and the technical details highlighted. The anterior transpetrosal approach provides an excellent approach for petroclival meningiomas with middle fossa and upper clival extension.

Four subtypes of petroclival meningiomas: differences in symptoms and operative findings using the anterior transpetrosal approach

Petroclival meningiomas are vaguely defined as tumours arising from the antero-medial zone to the internal auditory meatus. This report subclassifies petroclival meningiomas based on their origin determined by using radiological and intra-operative findings. Ninety-one patients with petroclival meningioma underwent surgery via the anterior transpetrosal approach. The Meckel's cave was routinely opened. Tumour origin was classified into four subtypes according to the main attachment and trigeminal nerve deviation into, upper clivus (UC), cavernous sinus (CS), tentorium (TE), and petrous apex (PA). Their characteristic clinical symptoms and anatomical features were investigated. The characteristic symptom was ataxia in the UC type (37.5%), abducens nerve palsy in the CS type (64.3%) and trigeminal neuropathy, mainly neuralgia in the PA type (80.0%) with a higher statistical difference from other subtypes. The rate of tumour invasion into Meckel's cave reached 70.3% in average, with the lowest rate in the PA type (25.0%). The rate of middle fossa extension was the highest in the TE type (59.5%). The middle fossa approach was considered to be ideal for UC and TE types because of easier access to the Meckel's cave. Radical dissection without complications was difficult in the CS type. Both the anterior transpetrosal approach and the lateral suboccipital approach could be indicated in the PA type due to the rare invasion of Meckel's cave and middle fossa, and frequent extension into the internal auditory meatus. This classification is useful to predict the relation between the tumour and the cranial nerves based on symptoms and images. The anterior transpetrosal approach could be used for all four subtypes and with an absolute indication in the UC and TE types showing middle fossa extension.

Quantification of the presigmoid transpetrosal keyhole approach to petroclival region

Despite the presigmoid transpetrosal approach has been used by different researchers in various ways, the surgical injury rate remains high. Applying a minimally invasive keyhole idea, we devised a presigmoid transpetrosal keyhole approach (PTKA), classified and quantitatively assessed their approach to the petroclival area on a cadaver model by using a neuronavigation system. The presigmoid transpetrosal keyhole approach was divided into four increasingly morbidity-producing steps: retrolabyrinthine, partial labyrinthectomy with petrous apicectomy, translabyrinthine and transcochlear keyhole approaches. Six latex-injected cadaveric heads (twelve sides) underwent dissection in which a neuronavigation system was used. An area of exposure 10 cm superficial to a central target (working area) was calculated. The area of clival exposure with each subsequent dissection was also calculated. The retrolabyrinthine keyhole approach (RLK) spares hearing and facial function in theory but provides for only a small window of upper clival exposure. The view afforded by partial labyrinthectomy with petrous apicectomy keyhole approach (PLPAK) provides for up to four times this exposure. The translabyrinthine keyhole approach (TLK) and transcochlear keyhole approach (TCK), although producing more morbidity, add little in terms of a larger petroclival window. However, with each step, the surgical freedom for manipulation of instruments increases. The presigmoid transpetrosal keyhole approach to the petroclival area is feasible and useful. The RLK has relatively limited utility. For lesions without bone invasion, the PLPAK provides a much more versatile exposure with an excellent chance of hearing and facial nerve preservation. The TLK provides for greater versatility in treating lesions but clival exposure is not greatly enhanced. The TCK adds little in terms of intradural exposure but should be reserved for cases in which access to the petrous carotid artery is necessary.

Modified Three-Dimensional Skull Base Model With Artificial Dura Mater, Cranial Nerves, and Venous Sinuses for Training in Skull Base Surgery -Technical Note-

Experience with dissection of the cavernous sinus and the temporal bone is essential for training in skull base surgery, but the opportunities for cadaver dissection are very limited. A modification of a commercially available prototype three-dimensional (3D) skull base model, made by a selective laser sintering method and incorporating surface details and inner bony structures such as the inner ear structures and air cells, is proposed to include artificial dura mater, cranial nerves, venous sinuses, and the internal carotid artery for such surgical training. The transpetrosal approach and epidural cavernous sinus surgery (Dolenc's technique) were performed on this modified model using a high speed drill or ultrasonic bone curette under an operating microscope. The model could be dissected in almost the same way as a real cadaver. The modified 3D skull base model provides a good educational tool for training in skull base surgery.

A Case of Giant Ecchordosis Physaliphora

To report a case of a giant ecchordosis physaliphora causing local bone remodelling. A 45 year old man, who presented with sudden sensorineural hearing loss. Transpetrosal approach to resect a midline prepontine mass. Radiological and histological findings. The distinction between giant ecchordosis physaliphora and intradural chordoma is questioned and exemplified by our case. It is possible they represent the same entity of disease, which must be distinguished from classical malignant osseous (extradural) chordoma.

Transpetrosal approaches for meningiomas of the posterior aspect of the petrous bone: Results in 43 consecutive patients

Objective To assess outcome following excision of meningiomas of the posterior aspect of the petrous bone through transpetrosal approaches. Material and method We carried out a retrospective case-series study in a multidisciplinary tertiary care center on all patients who underwent meningiomas removal from January 1989 to September 2005. Surgical approaches were transpetrosal: widened retrolabyrinthine, translabyrinthine, transotic and transcochlear, occasionally combined with a subtemporal transtentorial approach. Epidemiology, symptoms, preoperative evaluation, surgery, postoperative complications and facial and auditory results were analyzed using standardized grading systems. The Desgeorges and Sterkers classification was used to assess tumor size and location. Results Forty women and three men underwent surgery (mean age: 56.7). Medium-sized tumors stages 2 and 3 (84%) and AM and P localization (34% and 20.4%) predominated. In 65% of cases, the tumor extended beyond the CPA. Main presenting symptoms were balance disorders (72%) and sensorineural hearing loss (53.5%). Mortality was nil. A preoperative facial nerve paresis was present in 14% of patients. Tumor removal was complete in 79.1% of cases. At 1-year post-op, 73% of patients had a normal or subnormal facial function and 55% had serviceable hearing. A cerebrospinal fluid leakage occurred in 6.9%. Discussion Posteriorly attached meningiomas are less symptomatic and of better prognosis than medially inserted ones. Transpetrosal approaches are reliable for the removal for all types and sizes of such tumors, and can be easily combined in the same procedure with a subtemporal transtentorial approach to remove extensions to the clivus and tentorium. They offer low morbidity and a high proportion of facial nerve and hearing preservation.

EFFECTS OF USING COMBINED TRANSPETROSAL SURGICAL APPROACHES TO TREAT PETROCLIVAL MENINGIOMAS

Surgical treatment may be required for large petroclival meningiomas; however, surgery for these lesions is a major undertaking, and modern surgical approaches are still associated with considerable morbidity and recurrence rates. We analyzed our series of transpetrosally operated petroclival meningiomas to obtain detailed information regarding the surgery outcomes with respect to facial nerve effects, hearing changes, general neurological and psychosocial differences, and recurrence rates to identify opportunities for improvement. Between 1994 and 2004, we used transpetrosal approaches to operate on 29 patients for petroclival meningiomas larger than 30 mm. All patients were analyzed in detail regarding neurological outcomes and hearing abilities after surgery. Swedish-speaking patients were contacted for a psychosocial follow-up evaluation using the short-item 36 (SF-36) form. After surgery, the Glasgow Outcome Score improved in 14 patients, was unchanged in 11 patients, and worsened in four patients. Facial nerve function was found to be of House-Brackmann Grade 3 or worse in six patients (including three individuals with transcochlear surgery and facial nerve rerouting). Of the 23 patients who underwent hearing-preservation surgery, serviceable hearing was preserved in 17 individuals. Nineteen Swedish patients were contacted for psychosocial evaluation. Three patients could not participate for health reasons; of the remaining 16 patients, 12 reported physical health scores that were below mean values for the general population. For patients who did not experience very serious neurological compromise, we found that unexpected painful trigeminal neuropathy and unilateral swallowing difficulties conveyed a negative influence on health. Three years after surgery, the patients reported more normalized health scores. Generally, outcomes compared well with current reports. Outcomes can be improved, however by improving patients' psychosocial support; striving to decompress, preserve, and minimize dissection of ill-defined planes of cranial nerves; and using Simpson Grade 4 gamma knife approaches when radicality is precluded. Currently, the performance of transpetrosal surgery for petroclival meningiomas is a major undertaking that significantly affects a patient's health for several years; however, the approaches that we used allowed a high degree of tumor control with relatively little neurological morbidity.

Retrosigmoid Approach to Ventrolateral Pontine AVM

There are a number of different surgical approaches to pontine lesions, such as the anterior transpetrosal (Kawase's) approach, lateral (presigmoid) approach, and rhomboid fossa approach. The anterior transpetrosal approach is only suitable for exophytic lesions and the rhomboid fossa approach is problematic because of the possible damage to neural structures in its path. Yoshitusugu Oiwa et al reported on the removal of a pontine lesion through the presigmoid approach in which the lateral surface of the pons is approached through a small window without any additional neurologic deficit. The authors report on the successful removal of a pontine AVM (intra-axial) situated on the rostral part of the pons (lateral pontine surface) between the CN V and VII-VIII complex through a conventional retrosigmoid approach using a small lateral incision. The patient complained of sudden-onset headache and right-sided hemiparesis; brain CT showed hematoma on the left ventrolateral pons. There was sudden decreased consciousness on the fifth day of admission and follow-up showed rebleeding on the site. After transfemoral cerebral angiography and brain MRI, the hematoma and lesion were removed via a left-sided retrosigmoid approach. The lesion was confirmed as a pontine AVM. The patient recovered consciousness on the fifth postoperative day and showed signs of dense right-sided hemiparesis, diplopia, central-type facial palsy (left), and hearing loss. Exams at 15 months postoperatively showed full recovery of diplopia with near normal recovery of hemiparesis and facial palsy, but the hearing deficit was not improved. The important neural structures of the pons are (1) the corticospinal tract in the ventral pons, (2) reticular formation in the central pons, and (3) most of the nucleus in the dorsal part of the pons (rhomboid fossa). The middle cerebellar peduncle is in the lateral pons but a small incision on the peduncle results in only transient aggravation of cerebellar ataxia, so a surgical approach through the lateral pontine surface is feasible, which makes the conventional retrosigmoid approach a excellent choice in that area.

Localization of the Internal Auditory Canal in Anterolateral Transpetrosal Approaches—Cadaver and Radiological Analysis

Localization of the Internal Auditory Canal in Anterolateral Transpetrosal Approaches—Cadaver and Radiological Analysis