Subtemporal Approach Research Articles

Subtemporal Transtentorial Petrosalapex Approach for Giant Petroclival Meningiomas: Analyzation and Evaluation of the Clinical Application

With the advent of microsurgery and surgical techniques, along with the improvement in neuroimaging techniques and the microanatomy in cadaver study, improvement in terms of surgical morbidity and mortality has been remarkable; however, controversy still exists regarding the optimal surgical strategies for giant petroclival meningiomas (GPMs). We report a study of clinical and radiological features as well as the surgical findings and outcomes for patients with GPM treated at our institution over the past 6 years. During a 6-year period (April 2004 to March 2010), 16 patients with GPM underwent surgery by subtemporal transtentorial petrosal apex approach during which electrophysiological monitoring of cranial nerves and brainstem function were reviewed. There were nine females and seven males with a mean age of 56.9 years (range from 32 to 78 years). The most frequent clinical manifestations were headache (93.7%) and dizziness (93.7%). Regions and directions of tumor extension include clivus, parasellar, and cavernous sinus, as well as compression of brainstem, and so on. The trochlear nerve was totally wrapped in nine cases (56.2%). The postoperative Karnofsky Performance Scale (KPS) score was 76.3 ± 13.1. Mean maximum diameter of the tumors on magnetic resonance imaging was 5.23 cm (range, 4.5 to 6.2 cm). Subtemporal transtentorial petrosalapex approach was performed in all 16 cases. Gross total resection was achieved in 14 cases (87.5%) and subtotal resection in 2 cases (12.5%) with no resultant mortality. Follow-up data were available for all 16 patients, with a mean follow-up period of 28.8 months (range from 4 to 69 months), of which 11 (68.75%) lived a normal life (KPS, 80-100). Our suggestion is that GPM could be completely resected by subtemporal transtentorial petrosalapex approach. The surgical strategy of GPM should be focused on survival and postoperative quality of life. Microneurosurgical technique plays a key role in tumor resection and preservation of nerve function. Intraoperative electrophysiological monitoring also contributes dramatically to the preservation of the nerve function. Complete resection of the tumor should be attempted at the first operation. Any remnant is treated by radiosurgery.

Intraparenchymal papillary meningioma of brainstem: case report and literature review

Both intraparenchymal papillary meningioma and papillary meningioma with cyst formation of brainstem have never been reported. The authors present an extremely rare case of patient with intraparenchymal papillary meningioma of brainstem. A 23-year-old Chinese male presented with a 4-month history of progressive left upper limb and facial nerve palsy. Magnetic resonance imaging revealed a cystic-solid, heterogeneously enhancing mass in pons and right cerebral peduncle with no dural attachment. The tumor was totally removed via subtemporal approach. During surgery, the lesion was found to be completely intraparenchymal. Histological and immunohistochemical examinations were compatible with the diagnosis of papillary meningioma. The lesion recurred nine months after primary surgery, a second surgery followed by radiotherapy was performed. Till to now (nearly 2 years after the treatment), the patient is tumor free survival. Intraparenchymal meningioma of brainstem with cystic formation is very rare, however, it should be considered as a differential diagnosis of a brainstem neoplasm. The present case strongly recommended that postoperative radiotherapy was essential for the patients with papillary meningiomas.

Trans-sylvian STA-SCA吻合術

We describe a technique of a trans-sylvian STA-SCA anastomosis for the vertebrobasilar insufficiency. The procedure utilizes the combined pterional/anterior temporal approach and tentorial edge resection, and anastomosis is performed at the anterior pontmesencephalic segment of the SCA just lateral to the oculomotor nerve. This can provide a wider and shallower microsurgical space than the standard STA-SCA anastomosis via subtemporal approach; however, validation of this procedure is mandatory for it to become an alternative to the routine STA-SCA anastomosis.

Cavernous Malformations: A Paradigm for Progress

Cavernous Malformations: A Paradigm for Progress

Subtemporal transtentorial resection of cavernous malformations involving the pyramidal tract in the upper pons and mesencephalon

Lateral approaches to the brain stem for the resection of the cavernous malformations are preferred in order to avoid the structures within the floor of the fourth ventricle. The entry behind the pyramidal tract (PT) is usually carried out through the posterolateral surface of the brain stem. The more straightforward lateral approach below the temporal lobe is used rarely because of potential risks. The outcome after resection of the cavernomas involving the PT in the mesencephalon and the upper pons via the subtemporal transtentorial approach in nine patients was analysed. Mapping of the PT by direct electrical stimulation was used in the last four patients. The subtemporal transtentorial approach enabled adequate exposure of the lateral and anterolateral surface of the midbrain and the upper pons. No adverse events from the elevation of the temporal lobe were encountered. Direct electrical stimulation using a bipolar electrode with the parameters of 100Hz, 1ms, and 3-9mA evoked motor responses in three of four patients. It allowed placing the incision in the lateral surface of the midbrain behind the PT or between the fibres of the upper and the lower extremity. No worsening of the PT functions was observed in the series. The subtemporal transtentorial approach enables adequate exposure of the lateral and the anterolateral surface of the mesencephalon and upper pons, allowing neurophysiological mapping of the PT and thus avoiding its damage during removal of the cavernoma.

Microsurgerical treatment of PCA aneurysms via subtemporal approach monitored by microvascular doppler(10 cases report)

Objective To summarize the clinical features of intracranial aneurysms of posterior cerebral artery (PCA), and the surgical approaches and operative skills to treat them. Method The aneurysms arose from the P1 segment in 3 patients, the P2 segment in 5 patients and the P3 segment in 2 patients. Aneurysms on P1 segment were surgically treated via subtemporal associated pterional approach. Aneurysms on P2 and P3 segment were surgically treated via subtemporal approach. 7 aneurysms were successfully treated by clipping the aneurysmal neck,2 aneurysms were shaped and 1 aneurysm was isolated. 3 giant aneurysms were resected. Microvascular Doppler was conducted to examine the blood flow of aneurysms and parent arteries. Results 6 of 10 patients had postoperative good recovery. Temporal oculomotor palsy occurred in 2 patients, syntropic hemiablepsia occurred in 1 patients,light hemiplegia in 1 patient. All these patients were recovery with treatment. 1 oculomotor palsy and 1 syntropic hemiablepsia preoperation recovered postoperation after three months. Conclusions The microsurgery is one of the major methods for treating aneurysm of PCA. The subtemporal approach in treating aneurysm of PCA is simple,safe and good exposure. Microvascular doppler is a feasible, safe, and very reliable technique in aneurysm surgery. Key words: Posterior cerebral artery; Intracranial aneurysm; Microsurgery; Microvascular doppler

Microsurgical anatomy of the subtemporal transdural approach to the petroclival region

Objective To explore the anatomical structure and identify the safe resecting region in the temporal base approach of transpetrosal subdura.To explore ways to grind petrous bone easily.Method The subtemporal approach was simulated in 10 （ 20 sides ） formalin - fixed cadaveric adult heads to observe the grinding of the bone.The results of observation were photographed and measured to provide the safe range of the grinding petrous bone.Results As a symbol of the auditory canal, bone was divided into the part of around the internal auditory canal and the petrous apex.The bone around the internal auditory canal was devided into the lateral internal auditory canal and upper part.Distance of about 5 mm to the internal auditory canal could be grinded.The yard of the inside petrous apex could be grinded safly.Grinding the subdural bone could increase the vertical angle up to 15°.Conclusions The subtemporal tentorial approach can increase the view on the structure of the posterior fossa.It gives the priority exposure for the base of posterior fossa tumors. Key words: Petroclival region; Dissection; Surgical approach

Tumors of the posterior third ventricular region in pediatric patients: The Indian perspective and a review of literature

Background:Diverse tumors in the posterior third ventricular region (TPTVR) frequently occur in children. A decade's experience with pediatric TPTVR is presented, focusing on the Indian perspective.Materials and Methods:25 children (age range: 3-18 years; mean age: 13.32 years; presentation range: 7 days-2.5 years) had clinico-radiological assessment with contrast computed tomography (CT) and magnetic resonance imaging (MRI). The ventricular/lumbar cerebrospinal fluid (CSF) alpha feto protein (AFP)/beta human chorionic gonadotrophin (HCG) estimation was done when radiological suspicion of a germ cell tumor was present. Extent of resection was deemed partial when some tumor mass remained at the end of surgery, near total when <10% was retained over vital neurovascular structures, and total when complete resection was attained.Results:Operations included infratentorial supracerebellar approach (n = 12), occipito-transtentorial approach (n = 2), endoscopic biopsy and third ventriculostomy (n = 1), frontal parasagittal craniotomy, interhemispheric transcallosal subchoroidal approach (n = 2), middle temporal gyrus transcortical transventricular approach (n = 1), fronto-temporo-zygomatic combined transylvian and subtemporal approach (n = 1) and right ventriculoperitoneal shunt and stereotactic biopsy (n = 1). Only CSF diversion was performed for five patients with a small TPTVR. CSF diversion was required in 12 (48%) patients. Tumor pathology included pinealoblastoma (n = 4; one with pineocytic differentiation), nongerminomatous germ cell tumor (NGGCT; n = 3), germinoma (n = 3), pilocytic astrocytoma (n = 2), epidermoid (n = 3) and primitive neuroectodermal tumor (PNET), fibrillary astrocytoma, glioblastoma, teratoma, and meningioma (n = 1, respectively). A patient with neurocysticercosis was diagnosed solely on MRI (four did not undergo biopsy). Fractionated radiotherapy was administered in 13 patients with primary pineal tumors, PNET, NGGCT, fibrillary astrocytoma and glioblastoma. Extent of excision was total in 10 (40%), near total in 5 (20%), partial in 3 (12%) and a biopsy in 2 (8%) patients.Conclusions:Histopathologic characterization of TPTVR is essential prior to their further management. Benign lesions often have a good prognosis following gross total surgical resection. Pure germinomas are highly susceptible to radiotherapy. NGGCTs often have malignant components that require adjuvant therapy following surgery. The advancements in microsurgical techniques have led to gratifying perioperative results in these deep-seated lesions.

Tentorial Schwannoma in a 64-Year-Old Female -Case Report-

A 64-year-old woman presented with the history of transient global amnesia. Magnetic resonance imaging with contrast medium showed a lobulated heterogeneously enhanced cystic lesion attached to the superior surface of the right tentorium, indenting the right temporal lobe laterally and midbrain medially. A small part of the lesion was located under the right tentorium and did not involve the right trigeminal nerve. The lesion was subtotally resected via the subtemporal approach and did not affect the trochlear and trigeminal nerves. Histological examination showed that the lesion was schwannoma. Intracranial schwannomas usually arise from the cranial nerves. The present case of tentorial schwannoma not associated with the cranial nerves is extremely rare. Schwannoma should be included in the differential diagnosis of tumors arising from the tentorium.

Tentorial branch of the superior cerebellar artery

Background:The tentorial branch of the superior cerebellar artery (SCA) is not well known and is underreported in the literature. In the present study, the authors report and describe a dural branch arising from the SCA that was encountered during the surgical treatment of a tentorial dural arteriovenous fistula (DAVF). The clinical relevance of this branch is discussed.Case Description:A 53-year-old patient suffered a third recurrent right thalamic hemorrhage within 2 weeks rendering him comatose. Computed tomography scan revealed a right thalamic hematoma extending into the ventricles, producing acute hydrocephalus and midline shift. Cerebral angiography revealed a right-sided tentorial Borden type III DAVF fed primarily by the tentorial artery of Bernasconi and Cassinari and, to a lesser extent, the petrous branch of the middle meningeal artery. A small dural feeder originating from the SCA was suspected. Venous drainage was via the lateral mesencephalic vein, through an aneurysmal dilated basal vein of Rosenthal, to the straight sinus. The DAVF was approached surgically via a right subtemporal approach. Intraoperatively, after division of the tentorium, a tentorial branch originating from the SCA was identified. This artery was sectioned while preserving the SCA. The draining vein was ligated adjacent to the sinus. Postoperatively, the patient's neurological status improved and postoperative angiography demonstrated complete obliteration of the tentorial DAVF.Conclusion:Knowledge of the tentorial branch of the SCA is important as it may potentially be sectioned during division of the tentorium or avulsed from its origin in the SCA during surgical manipulation in the ambient cistern.

A rare case of greater petrosal nerve schwannoma

Background:Facial nerve schwannomas include only 0.8% of all intrapetrous mass lesions, and schwannomas originating exclusively from the greater petrosal nerve (GPN) are extremely rare. To date, only 13 reports have been described. In this case, the tumor was thought to originate from the GPN on the basis of clinical, radiological, and operative findings.Case Description:A 23-year-old girl presented an acute left facial palsy, a disturbance in tear secretion of the ipsilateral eye, and a left-sided conductive hypoacusia. Computed tomography (CT) scan and magnetic resonance imaging (MRI) showed an extradural mass in the left middle fossa. A subtemporal approach was performed and the lesion, originating from the proximal portion of the GPN, was excised. The post-operative course was satisfactory, except for a xerophtalmia, which was treated with artificial teardrops.Conclusion:GPN schwannomas can originate anywhere alongside the course of the nerve, from its proximal segment near the facial hiatus to its distal segment near the foramen lacerum. For these reasons, it requires differential diagnosis with trigeminal nerve schwannomas or with injuries arising from the geniculate ganglion, because it can be easily confused with those lesions. However, in less severe cases, an early diagnosis can be able to preserve the function of the facial nerve by reducing iatrogenic injuries caused by surgical maneuvers.

Dumbbell-shaped primitive neuroectodermal tumor mimicking trigeminal schwannoma: a case report and review of literature

Primitive neuroectodermal tumor (PNET) is presumably of neural crest origin, and cases of supratentorial PNET in adult are extremely rare. We reported a case of PNET presenting as a dumbbell-shaped tumor at the middle cranial fossa of skull base mimicking trigeminal schwannoma both clinically and radiologically. The patient underwent surgery on July 13, 2010, using a combination of subtemporal, pterional and retrosigmoid approaches, to achieve decompression and obtain a histological diagnosis. The patient worsened neurologically two weeks after surgery. Her consciousness level became comatose due to tumor bleeding with compression of the brain stem and her precarious physical condition prevented receiving further treatment with adjuvant radiation therapy and chemotherapy. The correct diagnosis of PNET is important because its management differs dramatically from that for trigeminal schwannoma.

Early and long-term results of the treatment of jugular paragangliomas using different ranges of surgical approach

Background and purposeThe applied approach to the jugular foramen is a combination of the juxtacondylar approach with the subtemporal fossa approach type A. The purpose of this study is to present our results of treatment of jugular paragangliomas using the aforementioned approach. Material and methodsTwenty-one patients (15 women, 6 men) with jugular paragangliomas were included in the study. The neurological status of the patients was assessed before and after surgery as well as at the conclusion of treatment. The approximate volume of the tumour, its relation to large blood vessels, cranial nerves and brainstem, as well as consistency and vascularity were also assessed. ResultsThe duration of symptoms ranged from 3 to 74 months. In 86% of patients hearing loss was the predominant symptom. The less frequent symptoms included pulsatile tinnitus in the head, dysphagia and dizziness. Approximate volume of the tumours ranged from 2 to 109 cm3. A gross total resection was achieved in 71.5% of patients. The postoperative performance status improved in 38% of patients, did not change in 38% and deteriorated in 24% of patients. ConclusionsA proper selection of the range of the approach to jugular foramen paragangliomas based on their topography and volume reduces perioperative injury without negative consequences for the radicality of the resection.

Successful third surgery for a case of status gelasticus: Lessons learned after nearly 200 cases of hypothalamic hamartoma surgical resection

We report the case of a 3-year-old boy with status gelasticus symptomatic to a giant hypothalamic hamartoma despite two previous hypothalamic hamartoma surgeries using pterional approaches from each side. Following his third resection employing an endoscopic, transventricular approach, he has been seizure free for 6 months with significant cognitive, behavioral, and electroencephalographic improvement. This case reinforces the importance of surgery for a form of status epilepticus and in addition that repeat (three) surgeries can be successful, indeed life changing. The optimal surgical approaches and management plan for hypothalamic hamartoma surgery-including subtemporal, subfrontal, transcallosal, and endoscopic approaches-are discussed, including how these treatment decisions have evolved as a result of our large series experience.

くも膜下出血をきたしたｃａｒｏｔｉｄ ｒｅｔｅ ｍｉｒａｂｉｌｅに合併した後交通動脈動脈瘤の１例

We report a case of true posterior communicating artery (Pcom) aneurysm associated with carotid rete mirabile presenting subarachnoid hemorrhage. A 77-year-old woman was admitted to our hospital because of disturbance of consciousness. Computed tomography showed subarachnoid hemorrhage. Cerebral angiography demonstrated 2 aneurysms arising from the left Pcom and left posterior cerebral artery (P1–P2 junction). The right carotid angiography demonstrated an abnormal vascular network around the cavernous portion of internal carotid artery (ICA), so-called “carotid rete mirabile.” The right ICA was aplastic and the left ICA was hypoplasic. Two days after onset, coil embolization was performed. As a result, the left P1–P2 junctional aneurysm was almost completely occluded, but it was impossible to occlude the left Pcom aneurysm. Twenty-four days after onset, neck clipping of the responsible left Pcom aneurysm was carried out through the left subtemporal approach. Postoperatively, the patient experienced temporary left oculomotor nerve palsy but improved. Follow-up angiography revealed disappearance of the left Pcom aneurysm and almost complete obliteration of the left P1–P2 junction aneurysm.

Subarachnoid Hemorrhage Due to Ruptured Posterior Cerebral Artery Aneurysm Simultaneously Associated With Multiple Remote Intracerebral Hemorrhages -Case Report-

A 61-year-old woman presented with aneurysmal subarachnoid hemorrhage (SAH) associated with multiple remote intracerebral hemorrhages (ICHs). She had undergone microsurgical neck clipping for ruptured right middle cerebral artery aneurysm and ventriculo-peritoneal shunting 16 years previously. Computed tomography revealed SAH predominantly in the basal cistern and ambient cistern, in association with multiple ICHs in the bilateral tegmentum of the brain stem and right caudate nucleus. Digital subtraction angiography revealed an aneurysm at the P(1) segment of the left posterior cerebral artery. The ruptured aneurysm was microsurgically clipped via a left subtemporal approach without complications. Simultaneous occurrence of aneurysmal SAH and multiple remote ICHs is rare. The spatial pattern of the ICHs in the present case is apparently unique.

Anatomy classifications of the superior petrosal venous and relations for surgical approaches

Objective The purpose of this study was to dissect these structure existed in petrous portions of the temporal bones and the posterior fossa nearby,to measure the distence of those important stuctures around the superior petrosal venous (SPV), to propose the patterns of drainage of the SPV along the petrous ridge in relation to the Meckel cave and internal acoustic meatus (IAM) and to delineate its effect on the surgical exposures obtained in subtemporal transtentorial and retrosigmoid suprameatal approaches. Methods Ten adult cadaveric heads (20 hemispheres) were studied, and data of SPV and the structures around were measured. The patterns of drainage of the SPV along the petrous ridge were characterized according to their relation to the Meckel cave and the IAM based on an examination of 20 hemispheres. Subtemporal trans-tentorial and retrosigmoid suprameatal approaches were performed in two additional cadavers to demonstrate the effect of the drainage pattern on the surgical exposures. Result The SPV originated from the cerebellopontine angle cistern, and were multibranch. According to SPV relationship with the Meckel cave and internal acoustic meatus (IAM), the patterns of drainage of the SPV were classified into three groups. Type Ⅰ emptied into the SPS above or medial to the Meckel cave. The most common type-Type Ⅱ, emptied between the lateral limit of the trigeminal nerve at the Meckel cave and the medial limit of the facial nerve at the IAM. Type Ⅲ emptied into the SPS above and lateral to the boundaries of the IAM Conclusions The site which the SPV emptied into the superior petrosal sinus (SPS) was relationship tightly with the Meckel cave and IAM. According to SPV relationship with the Meckel cave and internal acoustic meatus (IAM). The proposed modified classification system and its effect on the surgical exposure may aid in planning the approach directed along the petrous apex and may reduce the probability of venous complications. Key words: Superior petrosal vein; Superior petrosal sinus; Retrosigmoid approach; Subtemporal approach

Trigeminal schwannomas: experience with 57 cases and a review of the literature

Trigeminal schwannoma is a mostly benign tumor that can be cured by complete resection. Over the last few decades, several pioneers have developed surgical approaches enabling the total removal of such tumors. We analyzed 57 patients who underwent radical surgery, including 45 patients who underwent skull base surgery as their initial treatment, for removal of trigeminal schwannomas. Here, we report the surgical management of these cases. Since 1990, all such patients have been treated using three main types of middle fossa skull base approaches, which minimize the exposure of the brain: the anterior transpetrosal approach, subtemporal interdural approach (Dolenc), or a combination of these approaches. Before 1990, total tumor removal was achieved in only three of eight patients (38%). After 1990, the tumors were totally removed in 43 patients (90%) and were nearly completely removed in an additional three patients (6%). Among the patients who underwent skull base surgery as their initial treatment, a complete resection was achieved in 93% (42/45 patients) of the cases. However, total surgical removal after surgery and Gamma knife surgery was very difficult because of dense adhesions to the brain stem and cranial nerves. No surgery-related mortalities occurred in this series, and the individual KPS scores were more than 90% among the patients who underwent skull base surgery. No recurrences requiring additional surgery have occurred after an average follow-up period of 4.9 years. Most of the trigeminal schwannomas could be removed totally and safely during a single operation after the introduction of skull base surgery. Therefore, radiosurgery should not be applied as the treatment of first choice for younger patients. A correct anatomical knowledge is critical for minimizing brain exposure and avoiding surgical complications.

The posterior subtemporal keyhole approach combined with the transchoroidal approach to the ambient cistern: microsurgical anatomy and image-guided quantitative analysis

The aim of this study is to describe microsurgical anatomy and to quantitatively analyze exposure using the posterior subtemporal keyhole (PSK) approach combined with the transchoroidal keyhole (TCK) approach to the ambient cistern. We determined the proper location of craniotomy of such combined keyhole approach on 16 sides of cadaver heads. The PSK approach and the TCK approach were performed in the same minicraniotomy to observe microanatomic features and to quantitatively measure exposure limits of the ambient cistern and related structures using image-guided system. Some superficial and bone landmarks could be used to find the proper location of such combined minicraniotomy. In the PSK approach, the exposure distances of the trigeminal nerve and the anterior portion of the P2 segment (P2a) were 10.02 ± 0.76mm and 16.32 ± 2.02mm, respectively. The superior, inferior, anterior, and posterior exposure limit of brainstem from the intersection point of the lateral mesencephalic sulcus and pontomesencephalic sulcus was 7.5 ± 0.19mm, 11.04 ± 0.27mm, 15.72 ± 0.52mm, and 10.16 ± 0.38mm, respectively. In the TCK approach, the vertical distances between the taenia fimbriae and the lateral geniculate body without and with mild caudal retraction of the hippocampus were 5.28 ± 0.46mm and 11.18 ± 0.57mm, respectively. The linear exposure distances of the posterior portion of the P2 segment (P2p) or P3 segment were 12.14 ± 1.88mm. Except of one case, the P2p could be exposed using the TCK approach. The midpoint of the medial edge of the parahippocampal gyrus on the coronal magnetic resonance images provides landmark to choose the appropriate approach. The PSK combined with the TCK approach can simultaneously expose the lower and upper ambient cistern in a proper minicraniotomy.

Endoscopic Assistance in the Epidural Subtemporal Approach and Kawase Approach

Few reports exist in the literature about the use of endoscope assistance in the identification of structures in the posterior fossa. To asses the advantage of endoscopic assistance in the epidural subtemporal and Kawase approaches by studying anatomic exposure and surgical freedom in the posterior cranial fossa. Twelve epidural subtemporal approaches were performed on 6 adult cadaveric heads. On the same specimens, 6 endoscope-assisted subtemporal approaches and 6 Kawase approaches were then performed. At the end of each Kawase approach, endoscope assistance was used. The microsurgical observations were performed with a surgical microscope with magnification ranging from 4 x to 40 x. Endoscopic observations were made with a 0 degrees , 4-mm rod-lens endoscope. Anatomic exposure and surgical freedom were analyzed. Endoscopic assistance during the epidural subtemporal approach increased the anatomic exposure 3 mm superiorly, 20 mm inferiorly, and 10 mm medially from the trigeminal nerve. Surgical freedom was limited in the temporal lobe, the petrous apex, and the trigeminal nerve. The amount of increased anatomic exposure obtained with endoscopic assistance during the Kawase approach was 26 mm inferiorly and medially from the trigeminal nerve. Surgical freedom was limited by the brainstem and the depth of the posterior cranial fossa. The endoscope-assisted subtemporal approach can be useful in visualizing tumor in the posterior fossa. It can help the surgeon in planning further surgical steps through consideration of the size, extension, and adherence of the tumor to surrounding structures. The endoscope-assisted Kawase approach permits maximum anatomic exposure of the posterior cranial fossa, although the deepest neurovascular structures could be better addressed with more direct approaches.