Anterior Transpetrosal Approach Research Articles

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

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. 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. 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. 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.

Prevention of Cerebrospinal Fluid Leakage in the Anterior Transpetrosal Approach.

Background: The anterior transpetrosal approach (ATPA) is effective for reaching petroclival lesions, and it allows for complications such as impaired venous return and neuropathy to be resolved. However, there is still room for improvement regarding cerebrospinal fluid (CSF) leakage. Here, we aim to focus on describing specific preoperative, intraoperative, and postoperative countermeasures for preventing CSF leakage when using the ATPA. Methods: Eleven patients treated using the ATPA, who were treated at our hospital from June 2019 to February 2023, were included in this descriptive study. Preoperatively, we performed a 3D simulation of the opened air cells. Then, we classified patterns of dural closure into three types based on intradural manipulation and whether it involved opened air cells or not. Intraoperatively, we performed a dural closure that included the use of more-watertight sutures (DuraGen®) and an endoscope. Furthermore, temporal bone air cell volume measurements were performed to confirm the correlation between the volume and factors related to CSF leakage. Results: No postoperative CSF leakage was observed in any patient. The temporal bone air cell volumes significantly corelated with the air cells of the petrous apex, the high-risk tract in the petrous apex, and postoperative fluid collection in mastoid air cells. Conclusions: We have described countermeasures for preventing CSF leakage when using the ATPA. Preoperative simulations and the use of multiple-layered dural reconstructions with endoscopes could be considered more reliable methods for preventing CSF leakage when using the ATPA.

Clinical Efficacy of Neuroendoscope-assisted Microsurgery Through an Anterior Transpetrosal Approach in the Treatment of Meningiomas

Clinical Efficacy of Neuroendoscope-assisted Microsurgery Through an Anterior Transpetrosal Approach in the Treatment of Meningiomas

Anterior transpetrosal approach and the tumor removal rate, postoperative neurological changes, and complications: experience in 274 cases over 33 years.

The authors report on the anterior transpetrosal approach (ATPA) and the results of surgeries performed over a 33-year period for petroclival tumors, including meningioma, trigeminal schwannoma, chordoma, and epidermoid tumor. They analyze early postoperative neurological changes, surgical complications, and trends over the decades. A retrospective analysis of 274 surgical cases that had undergone the ATPA from January 1984 to March 2017 was conducted. Data were collected from charts, clinical summaries, operative records, and operative videos. The analyzed parameters included patient diagnosis, tumor size, disease location, operation date, tumor removal rate, pre- and postoperative neurological symptoms (consciousness level, motor and sensory deficits of the limbs, sensory aphasia, and cranial nerve III-VIII injuries), surgical deaths, and radiologically recognized brain injuries after the operation (contusion, infarction, hemorrhage). Gross-total resection (GTR) was achieved in 53.5% of the 243 tumors with available data. The GTR rate for meningiomas (148 cases) was 54.1%. Trigeminal schwannomas had a high GTR rate of 87.1%, whereas chordomas had a low GTR rate of 14.3%. The rate of early neurological deterioration immediately after the ATPA, referred to as "early neurological change," was as follows: consciousness disturbance in 1.9% of cases (5 cases), improvement of hemiparesis in 45.0% of cases but deterioration in 8.1% of cases, sensory aphasia in 2.3% of cases due to temporal lobe injury, improvement of cerebellar symptoms in 39.3% of cases with rare deterioration (1.9% of cases), worsening of preoperative diplopia in 49.4% of patients and rarely improving, improvement of trigeminal symptoms in 19.1% of cases (mostly trigeminal neuralgia) among the 43.7% of patients who had them preoperatively, and deterioration of facial hypesthesia and/or paresthesia in 27.4% of cases. Early neurological deterioration was monitored in 183 patients for 6 months to determine the surgical complications of ATPA. Consciousness disturbance recovered in half of the cases but persisted in 3 (1.5%). Hemiparesis fully recovered in 63.2% of cases, resulting in a complication rate of 3.0%. The most frequent complication was diplopia (36.4%), with a complete remission rate of 26.4%. The second most frequent complication was facial hypesthesia (24.0%), with a recovery rate of 16.1%. Facial nerve palsy improved in 63.0% of cases and had a complication rate of 4.9%. Cerebellar symptoms showed complete recovery in all cases. The ATPA allows the removal of petroclival tumors extending into Meckel's cave and the middle fossa, making it preferred for dumbbell trigeminal schwannomas and meningiomas. However, the ATPA's aggressive tumor removal can risk a lower recovery of cranial nerve IV-VI deficits. For benign meningiomas, initial observation with regular follow-up is recommended. Surgery is appropriate for high-growth cases aiming for total removal, accompanied by a thorough explanation of the risks. If the risks are not accepted, subtotal removal can be considered, and radiosurgery is suggested for residual tumor.

The complete anterior petrosectomy: an expanded extended-middle fossa approach with removal of the infratrigeminal petrous apex and drilling of the lateral clivus.

Intradural exposure in the extended middle fossa anterior transpetrosal approach is traditionally limited to the inferior petrosal sinus inferomedially. Expanding bone removal of the petrous apex around the petrous internal carotid artery (ICA), underneath the trigeminal ganglion/mandibular nerve, and into the lateral component of the clivus can significantly expand the limits of this approach beyond the inferior petrosal sinus and allows for exposure of the midline structures, aspects of the contralateral inferior clival region, and, when high riding, the vertebrobasilar junction. To date, no descriptive techniques for drilling into the lateral clivus in this approach have been published. The authors provide a detailed stepwise description of their complete anterior petrosectomy, in use at their institution, that involves skeletonization of the posteromedial petrous ICA, gentle elevation of the trigeminal ganglion/mandibular nerve, removal of the infratrigeminal petrous apex, and two techniques for drilling into the lateral clivus along the petroclival fissure. These techniques provide a direct and unobstructed corridor to the midpetroclival region and ventral brainstem with greater maneuverability and enhanced control of the midline structures, which is especially useful for resection of petroclival meningiomas, chondrosarcomas, and giant vascular lesions of the mid- and upper basilar artery and its proximal branches.

Trigeminal neuralgia secondary to osteoma and vascular compression: illustrative case.

Trigeminal neuralgia (TN) is a common neurosurgical issue that has a detrimental impact on patients' quality of life. Osteoma at the petrous apex is a rare etiology of TN. Here, the authors present a case involving the co-occurrence of petrous osteoma and a vascular loop around the trigeminal nerve. Both exerted pressure or compression on the exit of the trigeminal nerve. A 46-year-old male presented with a 3-year history of persistent severe pain in the right side of his face. Magnetic resonance tomographic angiography of the trigeminal nerve revealed an abnormal signal in the right prepontine cistern, along with a vascular loop accompanying the right trigeminal nerve. A computed tomography scan of the skull indicated a nodular calcified density. The combined anterior transpetrosal approach for petrous osteoma and microvascular decompression (MVD) for the offending vessel were successfully performed. The patient was discharged without any complications or facial pain. Although extremely rare, TN simultaneously secondary to petrous osteoma and offending vessels should be considered in the diagnosis. In this case, the combined surgical removal of petrous osteoma and MVD for the offending vessels proved to be an effective treatment for TN secondary to osteoma and vascular compression.

10159-STMO-7 INTRAOPERATIVE MRI SURGERY FOR POSTERIOR FOSSA LESIONS

Abstract Background: Intraoperative MRI (iMRI) is an important modality in brain tumor surgery to identify residual tumors, however, it is problematic due to patient positional limitations. In this study, we investigated the usefulness of iMRI for posterior fossa lesions. Materials and Methods: Of 320 cases of brain tumors removed using iMRI from June 2016 to April 2023, 24 cases of posterior fossa lesions were included. Tumor type, approach method, imaging availability, tumor removal rate, and complications were examined retrospectively. Results: Tumor types included 8 gliomas, 5 epidermoid cysts, 4 meningiomas, 3 metastatic brain tumors, 1 schwannoma, and 3 others. Eleven patients underwent midline suboccipital approach in the supine position, 8 patients underwent lateral suboccipital approach, 2 patients underwent occipital transtentorial approach, and 2 patients underwent anterior transpetrosal approach in the supine position. transpetrosal approach in 2 cases and subtemporal approach in 1 case. iMRI showed residual lesion in 14 of 24 patients. More than half of the gliomas and epidermoid cysts had intraoperative residual disease, whereas only one meningioma did. Total resection was achieved except for one case of intentional residual schwannoma and two cases of glioma. Discussion: iMRI requires the upper body to fit within a gantry, and it is difficult to image in the park bench position. However, various approaches is possible by using a supine-lateral or semi-prone position. In the concorde position, where the fourth ventricle and upper cerebellum are approached, it is useful to insert a mat in the anterior thoracic and raise the upper body. For tumors in the dorsal brainstem and upper cerebellum, the occipital transtentorial approach was used. iMRI is effective in the removal of all tumors, including gliomas in intramedullary tumors and epidermoid cysts in extramedullary tumors. Conclusion: iMRI can be used in posterior cranial fossa lesions.

Anatomic Study of Petrous Bone and Its Surrounding Structures in the Extended Anterior Transpetrosal Approach.

Extended anterior transpetrosal approach (ATPA) includes drilling the petrous bone to achieve maximal exposure of the petroclival region. Injuring of surrounding neurovascular structures, such as the internal carotid artery (ICA), during the procedure may result in severe complications. In this study, we aimed to use computer topographic images to provide comprehensive anatomic information on the petrous bone and surrounding structures to help surgeons during the extended ATPA. Computer topographic angiography images of 110 individuals were reviewed, and measurements were performed on coronal, sagittal, and axial planes following multiplanar reformation. The petrous apex and sagittal midline were used to locate the anterior, middle, and posterior parts of the petrous bone and petrosal segment of the ICA during the ATPA. The thicknesses of the petrous bone were 3.28±0.71, 3.53±0.88, and 7.02±1.11mm at the petrous apex, trigeminal impression, and internal opening of internal auditory canal (IAC) positions, respectively. The distances between the petrous apex to the trigeminal impression, internal opening of the IAC, auris interna, and labyrinth were 7.39±1.62, 15.95±2.48, 17.39±2.39, and 29.00±3.18mm, respectively. Furthermore, the petrosal segment of the ICA was located at the above landmarks on the petrous bone. Our findings provide anatomic information on the petrous bone and surrounding structures during the extended ATPA procedure based on fixed anatomic landmarks so as to achieve maximal exposure and reduce the number of complications.

How I do it: intradural anterior petrosectomy.

The anterior transpetrosal approach (ATPA) is a cranial base approach for addressing upper petroclival or lateral pontine lesions. It is fundamentally an epidural procedure involving the drilling of the petrous apex. However, this approach has significant procedure-related morbidity, and the surgeon must perform a complete petrosectomy, as the intradural structures are not in view during the drilling. For selected cases, a rationale exists for choosing a tailor-made intradural anterior petrosectomy (IAP). This article describes the relevant surgical anatomy and the different surgical steps of the IAP. IAP represents a feasible alternative to the standard ATPA with the advantage of minimizing the extent of petrous bone removal to the individual need.

Cerebrospinal fluid leakage prevention using the anterior transpetrosal approach with versus without postoperative spinal drainage: an institutional cohort study.

The efficacy of spinal drain (SD) placement for cerebrospinal fluid (CSF) leakage prevention after the anterior transpetrosal approach (ATPA) remains unclear. Thus, we aimed to assess whether postoperative SD placement improved postoperative CSF leakage after a skull base reconstruction procedure using a small abdominal fat and pericranial flap and clarify whether bed rest with postoperative SD placement increased the length of hospital stay. This retrospective cohort study included 48 patients who underwent primary surgery using ATPA between August 2011 and February 2022. All cases underwent SD placement preoperatively. First, we evaluated the necessity of SD placement for CSF leakage prevention by comparing the postoperative routine continuous SD placement period to a period in which the SD was removed immediately after surgery. Second, the effects of different SD placement durations were evaluated to understand the adverse effects of SD placement requiring bed rest. No patient with or without postoperative continuous SD placement developed CSF leakage. The median postoperative time to first ambulation was 3days shorter (P < 0.05), and the length of hospital stay was 7days shorter (P < 0.05) for patients who underwent SD removal immediately after surgery (2 and 12days, respectively) than for those who underwent SD removal on postoperative day 1 (5 and 19days, respectively). This skull base reconstruction technique was effective in preventing CSF leakage in patients undergoing ATPA, and postoperative SD placement was not necessary. Removing the SD immediately after surgery can lead to earlier postoperative ambulation and shorter hospital stay by reducing medical complications and improving functional capacity.

Simplified anterior transpetrosal approach without superior petrosal sinus and tentorial incision for lesions centered in Meckel's cave.

The anterior transpetrosal approach (ATPA) is an effective method to reach lesions in the petroclival region. This approach involves many steps, including superior petrosal sinus (SPS) ligation and tentorial cutting. It is sometimes unnecessary to perform all procedures in the ATPA for certain lesions, especially those centered in the Meckel's cave. Here, we present a simplified anterior transpetrosal approach (SATPA) without superior petrosal sinus and tentorial incision for lesions centered in the Meckel's cave as a modified ATPA. This study included 13 patients treated with SATPA. The initial steps of SATPA are similar to ATPA, excluding a middle cranial fossa dural incision, SPS dissection, or tentorial incision. Histological examination was performed to understand the membrane structure of the trigeminal nerve, which runs through the Meckel's cave. Pathology revealed trigeminal schwannoma (n=11), extraventricular central neurocytoma (n=1), and a metastatic tumor (n=1). The average tumor size was 2.4 cm. The total removal rate was 76.9% (10/13). Permanent complications included trigeminal neuropathy in four cases and cerebrospinal fluid leakage in one case. Histological examination revealed the trigeminal nerve traverses the subarachnoid space from the posterior fossa subdural space to the Meckel's cave and is covered with the epineurium in the inner reticular layer. We used SATPA for lesions located in the Meckel's cave identified using histological examination. This approach may be considered for small- to medium-sized lesions centered in the Meckel space. None.

The Evolution of Anterior Transpetrosal Approach for the Treatment of Petroclival Meningiomas: A Single-Center 128-Case Experience

The profound understanding of anterior transpetrosal approach (ATPA) is increasingly used to treat petroclival meningiomas (PCMs). We introduce the evolution of ATPA and the outcomes of PCMs treatment. Between January 2013 and December 2019, 128 patients with PCMs underwent surgery. According to tumor extension, we classified the 128 patients into five types (I-V), introduced key technologies of ATPA into different types for the first time, and achieved a supreme surgical technology. Clinical data, radiological findings, surgical treatments, complications, and patient outcomes were retrospectively analyzed. A total of 22 (17.2%), 44 (34.4%), 25 (19.5%), 29 (22.7%), and 8 (6.3%) patients had type I, II, III, IV, and V disease, respectively. Tumours were gross totally removed (GTR; Simpson I and II) in 100 patients (78.1%), sub-totally removed (STR; Simpson III) in 20 patients (15.6%), and partially removed (PR; Simpson IV) in 8 patients (6.3%). The progression or recurrence rates were 5% (5/100) for GTR, 22.3% (6/20) for STR, and 62.5% (5/8; 1 died) for PR. According to the Karnofsky Performance Scale and Glasgow Outcome Scale, 108 patients had good recovery (84.4%, 108/128) and 115 were independent (89.8%, 115/128) at the end of follow up. Because some key technologies were used in ATPA, the application of ATPA was extended, and greater tumor resection and nerve function protection could be achieved in the treatment of PCMs.

Anatomical variations and flow alterations of the uncal vein and its clinical implications in petroclival meningiomas.

The Uncal vein (UV), downstream of the deep middle cerebral vein (DMCV), has a similar drainage pattern to the superficial middle cerebral vein (SMCV) and may be involved in venous complications during the anterior transpetrosal approach (ATPA). However, in petroclival meningioma (PCM), where the ATPA is frequently used, there are no reports evaluating drainage patterns of the UV and the risk of venous complications associated with the UV during the ATPA. Forty-three patients with petroclival meningioma (PCM) and 20 with unruptured intracranial aneurysm (control group) were included. Preoperative digital subtraction angiography was used to evaluate UV and DMCV drainage patterns on the side of the tumor and bilaterally in patients with PCM and the control group, respectively. In the control group, the DMCV drained to the UV, UV and BVR, and BVR in 24 (60.0%), eight (20.0%), and eight (20.0%) hemispheres, respectively. Conversely, the DMCV in the patients with PCM drained to the UV, UV and BVR, and BVR in 12 (27.9%), 19 (44.2%), and 12 (27.9%) patients, respectively. The DMCV was more likely to be drained to the BVR in the PCM group (p < 0.01). In three patients with PCM (7.0%), the DMCV drained only to the UV, and furthermore, the UV drained to the pterygoid plexus via the foramen ovale, posing a risk for venous complications during the ATPA. In the patients with PCM, the BVR functioned as a collateral venous pathway of the UV. Preoperative evaluation of the UV drainage patterns is recommended to reduce venous complications during the ATPA.

Transpetrosal Routes to the Skull Base-Anterior and Posterior Transpetrosal Approaches.

The extended middle fossa approach with anterior petrosectomy, or anterior transpetrosal approach, is a highly effective and direct approach to difficult-to-access petroclival tumors and basilar artery aneurysms. This surgical approach exposes a significant window of the posterior fossa dura between the mandibular nerve, internal auditory canal, and petrous internal carotid artery, below the level of the petrous ridge, and provides an unobstructed view of the middle fossa floor to the upper half of the clivus and petrous apex, without requiring removal of the zygoma. The posterior transpetrosal approaches, including the perilabyrinthine, translabyrinthine, and transcochlear approaches, provide direct and wide exposure of the cerebellopontine angle and posterior petroclival region. The translabyrinthine approach is commonly used for the removal of acoustic neuromas and other lesions of the cerebellopontine angle. We provide a stepwise description of how we perform these approaches and how to combine and extend them in order to achieve transtentorial exposure.

Partial Clipping and Multilayered Wrapping Using Collagen Matrix for Partially Thrombosed Basilar Trunk Aneurysm: A Technical Case Report

Treatment of basilar artery trunk aneurysms is still challenging today, although numerous approaches and modalities of treatment exist. The authors present a case of a patient with a partially thrombosed, ruptured basilar trunk artery aneurysm successfully treated by clipping occlusion of the rupture point and multilayered wrapping of the aneurysmal dome. A 49-year-old man presented to our emergency room with a chief complaint of altered mental status. The patient was diagnosed with subarachnoid hemorrhage (SAH). No apparent bleeding point was identified on initial 3-dimension computerized tomography (CT) angiography and digital subtraction angiography (DSA). Follow-up DSA revealed a partially thrombosed saccular aneurysm emerging from the basilar trunk. We decided to treat the aneurysm surgically with partial clipping including the bleb and wrapping via the anterior transpetrosal approach. The surgery was performed successfully without any complications, and the residual blood flow within the aneurysm diminished remarkably over time. Although direct clipping and wrapping for basilar trunk artery aneurysms is one of the most challenging operations, it is a highly effective treatment for complex aneurysms, especially if other treatments are not available.

Anterior transpetrosal approach for microvascular decompression associated with the dolichoectatic vertebrobasilar artery in two patients with refractory trigeminal neuralgia: Technical note.

Trigeminal neuralgia (TN) due to compression from the dolichoectatic vertebrobasilar artery (DVBA) is extremely rare and difficult to treat due to its morphological characteristics. We report two cases of good transposition of DVBA and postoperative course obtained using the anterior petrosal approach and a new vasoculopexy method. We describe two cases of microvascular decompression (MVD) for refractory TN associated with DVBA. In both cases, MVD was performed through the anterior petrosal approach. The DVBA was decompressed using a GORE-TEX sling and WECK clip in an inferomedial direction. Complete pain relief without new neurological deterioration was achieved immediately in both patients. We experienced a rare condition of TN due to exclusion by the DVBA. The anterior transpetrosal approach was extremely effective in this case. This approach secured the surgical field, allowed transposition of the DVBA, and caused no perioperative complications.

[The Anterior Transpetrosal Approach].

The Anterior transpetrosal approach is a skull base surgical procedure that can provide a wide operative view of the petroclival and the prepontine region. This approach requires one to accurately understand the anatomy of the anterior part of the temporal bone and the histological structure of the dura mater. In addition, it is necessary to learn operative techniques for venous preservation, accurate hemostasis at each step, and prevention of cerebrospinal fluid leakage. In this article, the anatomy and surgical techniques that are required for a beginner to master the anterior transpetrosal approach are explained step by step.

Resection of petroclival clear cell meningioma by the anterior transpetrosal approach: diagnosis of rare pathology and improvement of preoperative hearing disturbance.

Clear cell meningioma is a rare histological variant of meningioma, which often recurs aggressively. This video demonstrates a patient with a petroclival clear cell meningioma, which was resected completely through the anterior transpetrosal approach. The absence of intratumoral spotty signal voids on preoperative susceptibility-weighted imaging (SWI) suggested that the tumor was a meningioma rather than a schwannoma, although typical imaging features of meningioma were not observed. After surgery, the patient’s preoperative hearing disturbance improved from class D to class A, which the authors had sometimes experienced in cerebellopontine angle meningioma surgeries. Careful observation over a 2.5-year period revealed no tumor recurrence, without additional treatment.The video can be found here: https://stream.cadmore.media/r10.3171/2022.1.FOCVID21219

Drilling off the Petrosal Apex and Opening the Upper Wall of Meckel's Cave Are the Key Elements of Good Outcomes in the Treatment of Trigeminal Neuralgia Secondary to Petrous Apex Meningioma.

ObjectiveThe surgical management of trigeminal neuralgia (TN) caused by petrous apex meningioma (PAM) is still a challenge because of the lesion’s deep location and the surrounding complex structures. The authors describe the intradural anterior transpetrosal approach (ATPA) and its effect on the treatment of TN secondary to PAM. MethodsA retrospective analysis of 15 patients with TN secondary to PAM who underwent surgery via the intradural ATPA was conducted. The key techniques, which included drilling off the petrosal apex (PA) and opening the upper wall of Meckel’s cave (MC), are described in detail. ResultsTotal removal of the tumor and complete pain relief (Barrow Neurological Institute I) were achieved in all 15 patients without significant morbidity. Five patients developed new facial numbness postoperatively, which disappeared within three months after surgery. The postoperative magnetic resonance imaging showed temporal lobe swelling in three patients, but no clinical symptoms. One patient had cerebrospinal fluid leakage and was managed with bed rest and temporary lumbar drainage. One patient had an intracranial infection and was treated with antibiotics. By the last follow up, no patients had pain relapse or/and tumor recurrence. It is worth noting that the vascular compression at the root of the trigeminal nerve was found in one patient during the operation. ConclusionOur experience suggests that drilling off the PA and opening the upper wall of the MC are key elements for a good outcome of the treatment of TN secondary to PAM. The intradural ATPA has the advantages for both tumor resection and pain relief.

Anterior transpetrosal approach: experiences in 274 cases over 33 years. Technical variations, operated patients, and approach-related complications.

The anterior transpetrosal approach (ATPA) was initially reported in 1985. The authors' institution has 274 case records of surgery performed with the ATPA during the period from 1984 to 2017. Although many technical advances and modifications in the ATPA have occurred over those 33 years, to the authors' knowledge no articles to date have reported a detailed analysis of variations and complications of the ATPA. In this study, the authors analyzed their patient series to elucidate improvements over time in ATPA methodology while highlighting unresolved problems and evaluating how to avoid surgical complications. All surgical cases (274 patients) using the ATPA at the authors' institution during the period from 1984 to 2017 were analyzed retrospectively using charts, clinical summaries, operative records, and operative videos. Obtained parameters were patient age and sex, diagnosis, size of tumors, location of disease, operative date, neurological symptoms before and after surgery, radiographically identified brain injury, and other surgical complications. The most common diagnosis was petroclival meningioma (n = 158), followed by trigeminal schwannoma (n = 32), chordoma (n = 25), epidermoid tumor (n = 21), other tumor (n = 27), aneurysm (n = 6), and other (n = 5). The original ATPA was performed in 239 cases. In an additional 35 cases, a modified ATPA was performed. Zygomatic osteotomy with ATPA was a common modification that was used in 19 of the 35 cases to decrease retraction damage to the temporal lobe for high-positioned tumors. Brain injury by temporal lobe retraction without venous hemorrhage still occurred in 8 of the 19 cases (3.1%) with surgical death in 1 of these cases (0.4%) of reoperation with sacrifice of the petrosal vein. Symptomatic CSF leak was the most frequent complication noted and was observed in 35 cases (13.5%). In most of these cases the patients were cured by observation or lumbar drain, but in 6 cases (17.1%) reoperation was needed. Facial nerve damage related to surgical approach decreased from 6.2% to 3.5% after 2010; however, the incidence of CSF leaks (13.5%) has not improved. There have been several modifications and advancements made in the ATPA to increase tumor removal and decrease surgical complications. However, complications related to surgical approach occurred, such as venous occlusion-related brain injury and facial nerve damage at pyramid resection. CSF leak remained an unsolved problem related to the ATPA procedures. Preoperative assessment of venous variation of the middle fossa, pneumatization of the temporal bone, and intraoperative monitoring of cranial nerves are important procedures to decrease these complications.