Purely endoscopic subtemporal keyhole anterior transpetrosal approach to access the petrous apex region: surgical techniques and early results.

OBJECTIVE: The anterior transpetrosal approach using a microscope to provide wider access to the petrous apex region has been described for radical resection of lesions of the middle and posterior skull base. The microscopic anterior transpetrosal approach (mATPA) requires a wide craniotomy and meticulous epidural procedures to minimize temporal lobe retraction. Recently, the clinical application of transcranial endoscopic keyhole approaches for minimally invasive surgery has been steadily expanding. In this study, the details of the purely endoscopic subtemporal keyhole ATPA (eATPA) for petrous apex lesions are described and its initial results are reported. METHODS: Between May 2022 and May 2023, the authors performed eATPA in 10 patients with petrous apex lesions, of which 6 were meningiomas, 3 were trigeminal schwannomas, and 1 was epidermoid cyst. The surgical procedure of the purely eATPA is as follows. After a small temporal craniotomy, the endoscopic procedure is started. The anterior rim of the petrous bone and Meckel's cave are exposed via an intradural subtemporal approach. The lesion is removed with additional drilling of Kawase's triangle, cutting the superior petrosal sinus, opening Meckel's cave, and cutting the tentorium. The authors also compared the outcomes of mATPA versus eATPA for consecutive cases of petrous apex lesions. RESULTS: Gross-total resection was achieved in 8 of the 10 patients. The average operative time was 4 hours 13 minutes. There were 3 cases of transient abducens nerve palsy and 1 case of trochlear nerve palsy in the postoperative period. No new-onset motor deficits or CSF leakage was noted in any of these patients. Only 1 patient exhibited postoperative asymptomatic temporal lobe edema. The Karnofsky Performance Scale (KPS) scores remained unchanged or improved for all patients postoperatively. Compared with mATPA, eATPA achieved a similar extent of resection and comparable postoperative KPS scores with a significantly shorter mean operative time, much smaller temporal craniotomy, and thus less mean blood loss during surgery with lower rates of new-onset temporal lobe edema in the postoperative period. CONCLUSIONS: An eATPA allows a direct route to access Meckel's cave and posterior cranial fossa lesions similar to conventional mATPA, with shortening the operative time and reducing the risk of postoperative temporal lobe edema. This eATPA is considered one of the new surgical techniques that can be expected to develop in the future.

Usefulness of Opening the Diaphragma Sellae Before Transecting Interclinoidal Ligament for Endoscopic Endonasal Transoculomotor Triangle Approach: Technical Nuances and Surgical Outcomes.

OBJECTIVE: Opening the oculomotor triangle (OT) and removing the posterior fossa lesion by endoscopic endonasal approach (EEA) is challenging for even an experienced endoscopic neurosurgeon. We summarize the treatment experience and technical nuances with EEA for resection of pituitary neuroendocrine tumors and cavernous sinus (CS) meningiomas invading through the OT. METHODS: Between 2018 and 2022, 8 patients, comprising 5 with pituitary neuroendocrine tumors (3 with nonfunctioning and 2 with somatotroph tumors with increased levels of growth hormone) and 3 CS meningiomas, were treated using an endoscopic endonasal transoculomotor triangle approach. The critical surgical technique is continuously opening the diaphragma sellae from medial to lateral toward the interclinoidal ligament and transecting it to enlarge the OT. We evaluated preoperative tumor size, previous surgical history, preoperative symptoms, extent of tumor resection, histopathology, and postoperative complications for all patients. RESULTS: The gross total resection (defined as complete removal) in 3 patients (38%), near-total resection (defined as >95% removal) in 4 patients (50%), and subtotal resection (defined as ≤90% removal) in 1 patient (12%) and gross total resection of tumor invading through the OT was achieved in all patients through pure EEA. Two of 3 patients with visual deficits in nonfunctioning pituitary neuroendocrine tumors improved, and the other remained stable postoperatively. One patient showed transient oculomotor nerve palsy. The growth hormone level of the 2 patients with somatotroph tumors declined to normal. For 3 patients with CS meningiomas, cranial nerve palsy improved in 2 patients, whereas the other patient developed increased facial numbness after surgery. CONCLUSIONS: The endoscopic endonasal transoculomotor triangle approach is an efficient surgical option for tumors with CS invasion and OT penetration.

Angiographic Evaluation of the Feeding Artery in Skull Base Meningioma.

To identify the characteristics of feeding arteries in skull base meningioma including location and prevalence, we evaluated the distributions and types of feeding arteries in skull base meningioma by cerebral angiography and assessed relationships to tumor attachment. We enrolled patients with skull base meningioma who underwent MRI and cerebral digital subtraction angiography (DSA), from September 2015 to October 2022. Subjects comprised 115 patients (32 males, 83 females; mean age, 52.7) with 117 meningiomas, showing tumor attachments around the "cavernous sinus to the upper part of the clivus" (Area 1), "lower part of the clivus to foramen magnum" (Area 2), and "tentorium around the petrous bone" (Area 3). Frequent arteries, such as the dorsal meningeal artery (DMA), the ascending pharyngeal artery (APA), the tentorial artery (TA), and the petrosal branch (PB) of the middle meningeal artery (MMA) were analyzed in terms of their associations with tumor attachment to Areas 1-3. Meningiomas with the DMA as a feeding artery correlated with tumor attachment to Area 1 (p < 0.001). Meningiomas with the APA correlated with tumor attachment to Area 2 (p < 0.001). Meningiomas with the TA correlated with tumor attachment to Area 3 (p < 0.001). The PB correlated with Area 3 (p < 0.05). Our study founded that visualization of these arteries correlated well with specific areas. These arteries were also the main feeders in each type of skull base meningioma.

Surgical Strategy in Modification of the Transpetrosal Approach to Avoid Postoperative Venous Complications: A Report of 74 Consecutive Cases.

BACKGROUND: The transpetrosal approach is a complex skull base procedure with a high risk of complications, particularly caused by injury of the venous system. It is in part related to variability of blood outflow pathways and their distinctive patterns in each individual patient. OBJECTIVE: To evaluate outcomes and complications after skull base surgery with use of the petrosal approach modifications, which selection was based on the detailed preoperative assessment of venous drainage patterns. METHODS: Overall, 74 patients, who underwent surgery via the transpetrosal approach at our institution between 2000 and 2017, were included in this study. In all cases, the venous drainage pattern was assessed preoperatively and categorized according to the predominant blood outflow pathway into four types as previously suggested by Hacker: (1) sphenoparietal sinus (SpPrt), (2) sphenobasal vein (SpB), (3) sphenopetrosal sinus (SpPS), and (4) cortical. The blood outflow through the bridging petrosal vein and the vein of Labbé was also taken into consideration. In patients with SpPrt- and a cortical-type venous drainage, the transpetrosal approach was used in a standard way. In patients with SpB-type venous drainage, limited extradural anterior petrosectomy was combined with intradural anterior petrosectomy after dural opening, superior petrosal sinus transection, tentorial cutting, Meckel's cave opening, and trigeminal nerve mobilization. In patients with SpPS-type venous drainage, after standard petrosectomy, dural opening, and tentorial cutting, SpPS ligation was done followed by 2-week interval before staged definitive tumor resection. RESULTS: Gross total, near-total, and subtotal resection of the lesion (meningioma, 48 cases; retrochiasmatic craniopharyngioma, 11 cases; brain stem cavernoma, 7 cases; other tumors, 8 cases) was achieved in 30 (40.5%), 24 (32.4%), and 20 (27.0%) patients, respectively. Postoperative complications that were possibly related to venous compromise were noted in 18 patients (24.3%), but neither one was major. Of these 18 patients, 9 were symptomatic, but all symptoms-aphasia (4 cases), seizures (2 cases), and confusion (3 cases)-fully resolved after conservative treatment. Overall, 13 patients, including 4 symptomatic, had signal changes on T2-weighted brain MRI, which were permanent only in 3 cases (all asymptomatic). CONCLUSION: Our suggested surgical strategy can be applied to any type of the venous drainage pattern. Preoperative evaluation and intraoperative preservation of the blood outflow pathways are crucial means for safe and effective application of the transpetrosal approach.

Endoscopic endonasal approach to remove pediatric intraventricular tumors of the third ventricle.

PURPOSE: Pediatric intraventricular tumors of the third ventricle are among the most difficult-to-treat brain tumors. Recently, endonasal endoscopic surgery for suprasellar, third ventricle, and median clivus lesions has become the common procedure, and its indications are expanding to pediatric cases. We describe our strategy for endonasal endoscopic surgery for pediatric third ventricle tumors. METHOD: We report on surgical anatomies and our surgical procedures in detail, including case presentations. RESULT: Endoscopic endonasal surgery has the advantage of providing a wider view of the tumor site, hypothalamus, optic chiasm, and other critical structures. Good indications for the endoscopic endonasal approach for intra-third ventricular tumors are those arising from the floor of the third ventricle. In particular, craniopharyngioma, a typical pediatric suprasellar tumor, sometimes extends into the third ventricle, causing great operative difficulty. However, aggressive removal for long-term control while preserving memory and visual function is important. We perform surgery with a strategy of radically removing tumors without causing damage to visual or brain function, and we adopt the "4-hands technique by two neurosurgeons" in full endoscopic surgery to remove tumors safely and aggressively. CONCLUSION: We describe our strategy for endonasal endoscopic surgery for pediatric third ventricle tumors, especially those extending from the suprasellar region into the third ventricle, and present a representative case.

Endoscopic Supraorbital Eyebrow Approach for Medium-Sized Tuberculum Sellae Meningiomas: A Cadaveric Stepwise Dissection, Technical Nuances, and Surgical Outcomes.

BACKGROUND: Tuberculum sellae meningiomas (TSMs) have traditionally been removed using a transcranial approach. In recent years, endoscopic surgery for TSMs has been reported with an expansion of indications. OBJECTIVE: We have performed a fully endoscopic supraorbital keyhole approach for small to medium-sized TSMs and performed radical tumor removal similar to conventional transcranial procedure. We report the details of this surgical procedure including cadaveric stepwise dissection and initial surgical results for small to medium-sized TSMs. METHODS: We used an endoscopic supraorbital eyebrow approach for 6 patients with TSMs between September 2020 and September 2022. Mean tumor diameter was 16.0 mm (range, 10-20 mm). The surgical approach included an eyebrow skin incision ipsilateral to the lesion, a small frontal craniotomy, subfrontal exposure of the lesion, removal of the tuberculum sellae, unroofing of the optic canal, and resection of the tumor. The extent of resection, preoperative and postoperative visual function, complications, and operative time were evaluated. RESULTS: Optic canal involvement was observed in all patients. Two patients (33%) showed visual dysfunction before surgery. Simpson grade 1 tumor resection was achieved in all cases. Visual function was improved in 2 cases, and remained unchanged in 4 cases. Postoperative pituitary function was preserved in all cases, with no decreases in olfaction. CONCLUSIONS: The endoscopic supraorbital eyebrow approach for TSMs allowed resection of the lesion, including tumor extending to the optic canal, with a good surgical view. This technique is minimally invasive for patients and may represent a good surgical option for medium-sized TSMs.

Endoscopic Endonasal Transpterygoid Approach for Resection of Carotid Sympathetic Plexus Schwannomas: A Cadaveric Stepwise Dissection, Technical Nuances and Surgical Outcomes.

OBJECTIVE: Carotid sympathetic plexus (CSP) schwannomas are rare brain tumors located in a complex site around the cavernous sinus and carotid canal in the petrous bone. This study describes 3 cases of CSP schwannomas that underwent surgical removal of the tumor through an endoscopic endonasal transpterygoid approach. METHODS: Between 2016 and 2021, 3 cases of CSP schwannomas were treated using an endoscopic endonasal transpterygoid approach. Preoperative tumor size, preoperative and postoperative symptoms, internal carotid artery (ICA) displacement, extent of tumor resection, intraoperative findings showing tumor origin, and surgical complications were evaluated in all patients. RESULTS: Two tumors were in the petrous region, and the other one was in both the petrous and cavernous regions. The median tumor diameter was 41.3 mm. In the 3 cases, the ICA was displaced to the superolateral side, the anterolateral side, and the posterior side, respectively. Near-total resection was achieved in all 3 cases via an endoscopic endonasal transpterygoid approach. There were no endonasal postoperative complications, and the cranial nerve disability improved in all 3 patients at 1-year follow-up. CONCLUSIONS: The surgical technique for CPS schwannoma using an endoscopic endonasal transpterygoid approach may be a viable option because endoscopy has been proven to offer better intraoperative visualization and reduce postoperative discomfort for patients. Tumors located medial and inferior to the ICA pars cavernous sinus or anterior, inferior, and medial to the paraclival ICA are ideal candidates for surgery using this endoscopic approach.

[Endoscopic Endonasal Surgery for Pediatric Suprasellar Tumors].

Pediatric suprasellar tumors are difficult to treat. Their sellar-suprasellar location frequently results in compression of the adjacent critical neurovascular structures, making them a challenging surgical entity. Our surgical strategy emphasizes on radical resection of the tumor without compromising visual or cognitive functions. In recent years, the endoscopic endonasal approach has been increasingly used for pediatric suprasellar tumors. We have adopted a "4-hand technique by two neurosurgeons" during endoscopic endonasal surgery to resect aggressive tumors safely. Posterior clinoidectomy and upper clivectomy are useful additional procedures to resect intra-3rd-ventricle and retrochiasmatic suprasellar tumors. Here, we present our surgical management strategy and tips for endonasal resection of pediatric suprasellar tumors.

Visualization of Resected Area in Endonasal Endoscopic Approach versus Transcranial Approach for Skull Base Meningiomas by Voxel-Based-Lesion Mapping.

BACKGROUND: We aimed to evaluate the resected area of endonasal endoscopic approach (EEA) and transcranial approach (TCA) for skull base meningiomas (SBMs) using voxel-based-lesion mapping and visualized the appropriate tumor location in each approach. METHODS: We retrospectively examined 182 patients with SBMs who underwent tumor resection in our hospital between 2014 and 2019. Pre- and post-operative SBMs were manually delineated on MRI to create the voxels-of-interest (VOIpre and VOIpost) and were registered onto the normalized brain (normalized VOIpre and normalized VOIpost). The resected map was created by subtracting normalized VOIpost from the normalized VOIpre divided by the number of cases. The resected maps of TCA and EEA were compared by subtracting them. RESULTS: Twenty patients underwent EEA and 135 patients underwent TCA. The tumor resected map demonstrated that the resected area of EEA frequently accumulated on the central skull base, while that of TCA accumulated near the central skull base. The border of both approaches matched the circle that connects neural foramens at the skull base. CONCLUSIONS: The resected area of SBMs by EEA and TCA was well visualized by voxel-based-lesion mapping. The circle connecting the neural foramens was the border of EEA and TCA.

Endoscopic Contralateral Interhemispheric Transfalcine Keyhole Approach for Large Falcine Meningiomas.

OBJECTIVE: Falcine meningioma is usually approached ipsilaterally, and the technique for tumor removal has traditionally been performed under microscopy. We report a surgical procedure for large falcine meningioma by an endoscopic contralateral interhemispheric transfalcine keyhole approach. METHODS: The study period was from September 2019 to March 2021. Study participants were patients with World Health Organization grade I meningioma showing falx attachment, excluding neurofibromatosis, who underwent initial surgery at our institution. The surgical procedure begins with a small contralateral craniotomy of about 3 cm, followed by insertion of an endoscope. The tumor attachment to the falx is excised, exposing the tumor. Internal decompression is performed, and the lesion is dissected from the surrounding brain before removal through the falx. RESULTS: An endoscopic contralateral interhemispheric transfalcine keyhole approach was used to resect 4 cases of large falcine meningioma. The mean operation time was 265 minutes (range: 216-294 minutes), achieving Simpson grade I removal in all cases. No evidence of cerebral infarction, cerebral edema, or new neurological complaints related to impaired venous return was seen using this surgical method. CONCLUSIONS: In the case of falcine meningioma, the endoscopic keyhole contralateral technique allows detachment of the tumor from the falx and safe manipulation in a minor field of view. In addition, because the craniotomy is smaller and the operation time is shorter, this procedure offers a less-invasive approach for the patient. This technique is thus, in our opinion, quite advantageous.

[How to Use a High-Speed Drill and an Ultrasonic Aspirator During Skull Base Surgery].

During surgery for skull base lesions, maximum efforts should be made to improve the removal rate of the lesion while avoiding complications, and it is necessary to expand the surgical field by selecting appropriate surgical instruments and equipment. In both microsurgery and endoscopic surgery, high-speed drills and ultrasonic aspirators contribute significantly to the safe and reliable removal of skull base lesions, and the surgeons need to be familiar with these characteristics. The specific vital points are as follows: (1) Preparation of the appropriate environment for using a high-speed drill or an ultrasonic aspirator with the understanding of the microsurgical anatomy, (2) Bone excision using a high-speed drill with the selection of an appropriate drill attachment or drill bar tip according to the site of use, (3) Internal decompression of lesions using an ultrasonic aspirator with appropriate settings, (4) Additional expansion of the surgical field by using an ultrasonic aspirator in the osteotomy mode, and so on. This section describes details of how to use a high-speed drill and an ultrasonic aspirator during skull base surgery.

Capillary hemangioma of the sphenoid sinus with intrasellar and parasellar extensions.

Capillary hemangiomas are benign vascular tumors usually diagnosed in infancy and involving skin and soft tissues. We report a rare case of an adult capillary hemangioma of the left sphenoid sinus extending into the intrasellar and parasellar regions. A 71-year-old woman presented with complaints of headaches and diplopia. Magnetic resonance imaging revealed a T2-hyperintense mass-like lesion involving the left posterior ethmoid and sphenoid sinuses and left cavernous sinus, that had extended into the intrasellar and parasellar regions. Dynamic contrast-enhanced computed tomography revealed enhancing vessel-like structures within the lesion during the arterial phase, which were observed to expand further in the late phase of the examination. This characteristic feature indicated increased vascularity, suggesting the presence of a capillary hemangioma. The patient underwent endoscopic resection via the endonasal transpterygoid approach, and the lesion was diagnosed histopathologically as a capillary hemangioma. To aid diagnosis and clinical management, radiologists should be aware of the imaging findings related to capillary hemangiomas.

Osaka Sliding Knot Seals Dural Defect Simply in Extended Endoscopic Endonasal Approach.

An extended endoscopic endonasal approach (EEA) has become standard for parasellar and midline skull base lesions. However, postoperative leakage of cerebrospinal fluid (CSF) can result from dural defects after lesion removal. We present a simple and effective technique, the Osaka sliding knot, to prevent CSF leakage. Between November 2018 and March 2021, a total of 41 patients underwent reconstruction of skull base defects with intraoperative high-flow CSF leaks after extended EEA by using this closure technique, of whom only 1 patient experienced postoperative CSF leakage. This technically simple and efficient method seals the dural defect to prevent CSF leakage after surgeries using an extended EEA.

Ectopic thyroid tissue at the skull base: a case report.

Ectopic thyroid tissue is a rare entity, resulting from developmental abnormality during the migration of the embryonic thyroid germ from the floor of the primitive foregut to its final pre-tracheal position. Although ectopic thyroid tissue may be located anywhere, its location at the skull base is extremely rare. We report a case of ectopic thyroid tissue at the skull base in a 19-year-old man with multimodality imaging findings.

Pediatric giant cell reparative granuloma of the lower clivus: A case report and review of the literature.

Giant cell reparative granuloma (GCRG) is a benign nonneoplastic granulomatous lesion and is rare in the cranial bone. We present a pediatric case of this lesion arising from the condyle and lower clivus. A 9-year-old girl presented with slowly progressive hoarseness and dysphagia. She showed left glossopharyngeal, vagus, and hypoglossal nerve palsy. An osteolytic lesion around the lower clivus and condyle joint was accompanied by deformation of the craniovertebral junction. An endoscopic endonasal approach was used to decompress the cranial nerve and confirm the pathological finding. The lesion around the condyle was not resected to preserve occipito-cervical stability. The residual lesion has been observed carefully for 6 months, and regrowth has not occurred. GCRG is a rare granulomatous lesion in the cranial bone. This case is the first report of a pediatric clival GCRG. Treating pediatric GCRG may be helpful.

Minimal anterior and posterior combined transpetrosal approach for large petroclival meningiomas.

OBJECTIVE: Petroclival meningiomas (PCMs) remain difficult to remove, and radical tumor resection continues to pose a relatively high risk of neurological morbidity in patients with these lesions because of the proximity of the tumor to neurovascular structures. The anterior and posterior combined (APC) transpetrosal approach allows resection of a large petroclival lesion with minimal retraction of the temporal lobe. However, this approach is thought to be complex and time-consuming. The authors simplified this approach by minimizing the petrosectomy and used this method for large PCMs. This retrospective study describes the surgical technique and surgical outcomes of large PCMs. METHODS: Between 2014 and 2019, 23 patients (19 women and 4 men) with benign (WHO grade I) PCMs were treated using the minimal APC (MAPC) transpetrosal approach. The mean age at surgery was 54.0 years (range 37-74 years). The mean tumor diameter was 40.3 mm (range 30-74 mm). The surgical technique consisted of a temporo-suboccipital craniotomy and minimal drilling of the petrous ridge. After opening Meckel's cave and removing the lesion at the prepontine cistern, drilling of the petrous apex with superior mobilization of the trigeminal nerve was performed through the subdural space for further tumor resection around the petrous apex. Finally, the tumor was removed as much as possible. RESULTS: The mean preoperative and postoperative tumor volumes were 26.8 and 1.3 cm3, respectively. The mean extent of resection was 95.4% (range 62%-100%). Postoperative impairments included facial numbness in 7 patients, trochlear nerve palsy in 3 patients, mild oculomotor nerve palsy in 2 patients, and transient abducens nerve palsy in 1 patient. Preoperative Karnofsky Performance Status was improved in 13 patients, remained stable in 9 patients, and deteriorated in 1 patient. CONCLUSIONS: The MAPC transpetrosal approach provides sufficiently wide exposure of petroclival lesions. Maximal resection via the MAPC transpetrosal approach is a suitable surgical option for the treatment of large PCMs.

Combination of p53 and Ki67 as a Promising Predictor of Postoperative Recurrence of Meningioma.

BACKGROUND: Meningioma is a common intracranial tumor originating from arachnoid cap cells. Meningiomas are generally benign tumors curable by one-time resection. However, some meningiomas regrow and invade into the dura mater, and thus frequently require additional treatment. A useful marker to predict the regrowth of meningioma is desired. This study aimed to clarify the significance of p53 and Ki67 for postoperative recurrence of meningioma. MATERIALS AND METHODS: The expression of p53 and Ki67 in 215 intracranial or intraspinal meningiomas was investigated by immunohistochemistry. RESULTS: Of the 215 meningiomas, 35 cases (16.3%) were p53-positive and 49 cases (22.8%) were Ki67-positive. Multivariate analysis revealed Ki67 and p53 status as being significantly correlated with recurrence. Positivity for either Ki67- or p53 was significantly associated with poor recurrence-free survival. CONCLUSION: Combined p53 and Ki67 status might represent a useful independent predictive marker for recurrence of meningioma.

Changes in cognitive function after resection of lesions in the anterior part of the lateral ventricle via an interhemispheric transcallosal approach.

Anterior callosotomy to about 20 mm has been considered relatively safe empirically. The present study aimed to compare cognitive function before and after resection of tumors in the anterior part of the lateral ventricle. We analyzed 6 patients with intraventricular tumors located in the anterior horn or body of the lateral ventricle who underwent surgical excision via interhemispheric transcallosal approach at Osaka City University Hospital between March 2015 and August 2018. And clinical and imaging studies, neuropsychological function using MMSE, WAIS-III and WMS-R and surgical complications were retrospectively reviewed based on the medical records at our institution. As a result, 4 patients achieved gross total resection of the tumor and 2 patients achieved subtotal resection. 4 patients showed hydrocephalus, which disappeared in each case within 6 months after tumor resection. Mean length of callosotomy was 16.9 mm (range, 15.5-26.1 mm). One patient showed postoperative transient deficits including aphasia, microphonia, ballism in all extremities and hemiplegia, and another patient experienced subjective difficulty when talking. These symptoms disappeared within 3 months after tumor resection. Scores from the MMSE and WAIS-III showed no significant postoperative deterioration. Performance intelligence quotient (P = 0.04), full intelligence quotient (P = 0.04) and perceptual organization (P = 0.03) of WAIS-III were significantly improved after surgery compared with preoperatively. In conclusion, anterior corpus callosotomy of about 20 mm for intraventricular tumor in the anterior horn or body of the lateral ventricle might have little effect on cognitive function in the chronic phase, although the influence of hydrocephalus cannot be ignored.

Surgical implementation and efficacy of endoscopic endonasal extradural posterior clinoidectomy.

OBJECTIVEThe endoscopic endonasal approach (EEA) for skull base tumors has become an important topic in recent years, but its use, merits, and demerits are still being debated. Herein, the authors describe the nuances and efficacy of the endoscopic endonasal extradural posterior clinoidectomy for maximal tumor exposure.METHODSThe surgical technique included extradural posterior clinoidectomy following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate extradural exposure. Forty-four consecutive patients, in whom this technique was performed between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging.RESULTSExtradural posterior clinoidectomies were successfully applied in all patients without permanent neurovascular injury and with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and 1 patient experienced transient postoperative oculomotor nerve paresis; however, the patients with deficits recovered within 3 months. On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomy than in cases without posterior clinoidectomy.CONCLUSIONSThe extended EEA with extradural posterior clinoidectomy creates an extra working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.