Spontaneous Cystic Arteriovenous Malformation-A Novel Treatment Alternative.

BACKGROUND: Brain arteriovenous malformation (BAVM) is a life-threatening vascular congenital malformation due to the risk of intracerebral hemorrhage. The formation of a spontaneous cyst within a BAVM, without history of hemorrhage or gamma knife surgery, is rare and has an unknown pathophysiology. We suggest a novel theory of spontaneous cystic BAVM formation, subsequently treated with endovascular embolization followed by surgery with a favorable long-term outcome. METHODS: Review of the literature using PUBMED database and comparison between clinical presentation, diagnostic imaging studies, and treatment options. RESULTS: The high flow causing a shear stress over the drainage vein may be responsible for venous ectasia and thus incrementing hydrostatic intranidal pressure causing a serous effusion that develops into a pseudocyst. We hypothesize that hemodynamic factors may be responsible for both origin and growth of such cystic lesions. CONCLUSIONS: Endovascular treatment allowed us to achieve cyst volume reduction by managing its unique flow characteristics. To our knowledge, this is the first case report of combined treatment with endovascular and surgical approach of a cystic BAVM.

Dorsal extensions of the fastigium cerebelli: an anatomical study using magnetic resonance imaging.

BACKGROUND AND PURPOSE: The fastigium cerebelli is an important topographical landmark for neurosurgeons and radiologists. However, few studies have characterized the morphology of the fastigium cerebelli. We aimed to investigate the fastigium cerebelli using postmortem specimens and magnetic resonance imaging (MRI) in vivo. MATERIALS AND METHODS: Three cadaveric brains were midsagittally sectioned for observing the fastigium cerebelli. Additionally, 66 outpatients underwent MRI, including sagittal T1-weighted imaging, axial T2-weighted imaging, and coronal constructive interference in steady-state (CISS) sequence. RESULTS: In the cadaveric specimens, the fastigium cerebelli was observed as a beak-like dorsal protrusion of the fourth ventricle. Its inner surface was observed as a small fovea. On serial CISS images, the fastigium cerebelli consistently possessed a pair of triangular-shaped, dorsal extensions lying parasagittally along the nodule. These extensions were classified as symmetrical, right-side dominant, or left-side dominant. The symmetrical type was the most predominant and comprised 60.6% of the extensions, while the right-side dominant and left-side dominant types comprised 13.6 and 25.8%, respectively. In 91% of the 66 patients, the number of slices covering the entirety of the dorsal extensions were the same on both sides. The fastigial angle (θ) formed by lines tangent to the superior and inferior medullary velums varied widely. CONCLUSIONS: The fastigium cerebelli has a pair of dorsal extensions lying parasagittally along the nodule. Coronal CISS sequence is useful in delineating the fastigium cerebelli in vivo.

The cisternal segments of the oculomotor nerve: a magnetic resonance imaging study.

PURPOSE: The cisternal segments of the oculomotor nerve (OMN), which courses through the interpeduncular and oculomotor cisterns (OMC) have not been well delineated on neuroimages. The present study aimed to explore the cisternal segments of the OMN using magnetic resonance (MR) imaging. METHODS: A total of 92 patients were enrolled in this study. A constructive interference in steady-state sequence was performed in coronal and axial sections. RESULTS: On coronal images, cisternal portions of the OMN were entirely delineated in 97 % on the right and in 98.5 % on the left. Most of the OMCs were of a round shape, with a centrally located OMN, while 9 % were ectatic with the OMN located eccentrically. In 5.3 % of cases, fetal-type posterior communicating arteries (PCoAs), which coursed adjacent to the superior surfaces of the OMNs at the oculomotor triangle (OMT), were observed. On axial images, cisternal portions of the OMN were identified in all cases. The OMN segment passing through the OMT showed medial, central, and lateral courses. The PCoAs and P2 segments of the posterior cerebral artery (PCA) were adjacent to the OMNs in 17 and 19 % of cases, respectively. CONCLUSIONS: The OMN most frequently courses in the medial part of the OMT and enters into the OMC. These findings indicate that OMN paresis can be caused by vascular compression at any site of the interpeduncular cistern and OMT.

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.

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.

Refining the Anatomy of Percutaneous Trigeminal Rhizotomy: A Cadaveric, Radiological, and Surgical Study.

BACKGROUND: Percutaneous trigeminal rhizotomy (PTR) is a widely used procedure for trigeminal neuralgia. However, comprehensive analyses that combine anatomic, radiological, and surgical considerations are rare. OBJECTIVE: To present high-quality anatomic dissections and radiological studies that highlight the technical nuances of this procedure. METHODS: Six silicon-injected postmortem heads underwent PTR. The surgical corridors were dissected, and the neurovascular relationships were studied. In addition, 20 dried human skulls and 50 computed tomography angiography and MRI scans were collected to study the anatomic relationships for a customized puncture corridor. RESULTS: The PTR corridor was divided into 3 segments: the buccal segment (length, 34.76 ± 7.20 mm), the inferior temporal fossa segment (length, 42.06 ± 6.92 mm), and the Meckel cave segment (length, 24.75 ± 3.34 mm). The puncture sagittal (α) and axial (ß) angles measured in this study were 38.32° ± 4.62° and 19.13° ± 2.82°, respectively. The precondylar reference line coincided with the foramen ovale in 75% of the computed tomography angiography scans, and the postcondylar line coincided with the carotid canal in 70% of the computed tomography angiography scans; these lines serve as the intraoperative landmarks for PTR. The ovale-carotid-pterygoid triangle, delineated by drawing a line from the foramen ovale to the carotid canal and the lateral pterygoid plate, is a distinguished landmark to use for avoiding neurovascular injury during fluoroscopy. CONCLUSION: Knowledge of the anatomic and radiological features of PTR is essential for a successful surgery, and a customized technical flow is a safe and effective way to access the foramen ovale.

The expanding role of endoscopic skull base surgery.

The endoscopic endonasal approach (EEA) is a surgical technique where a small aperture, the nostrils, can give access to the whole ventral skull base. Its principles differ from the ones of traditional skull base approaches where a wide external opening is often accompanied by a relatively small working area. Most of the results of EEAs published in the literature come from retrospective case series and the follow-up is still limited, however the consensus is that this technique is safe and effective in selected cases and when performed within dedicated skull base centres. This article sets to give an overview of the current state of endoscopic skull base surgery, based on the recent evidence and our centre's experience with nearly 2000 EEAs. The team's experience with endoscopic as well as open approaches plays a critical role in achieving satisfactory results when treating pathologies of the skull base. Guided by the principle of least neural and vascular manipulation, the team should be able to select the least traumatic route (open or endoscopic) and be able to approach the skull base from all angles.

Ideal trajectory for frontal ventriculostomy: Radiological study and anatomical study.

OBJECTIVE: Several techniques have been described to improve the accuracy of the freehand procedure for frontal ventriculostomy and reduce complications due to suboptimal placement or misplacement of the catheter tip. To date, none of the available studies have found a reliable, low cost and consistent technique. We aimed to provide a standardized protocol for freehand frontal ventriculostomy. METHODS: In the first part of the radiological study, 125 CT scans were used to measure the length of the catheter using 2 right-sided entry points. In the second part, a grid of 24 entry points on the frontal bone was used in 50 CT scans to record the distance from the cranial surface to the Foramen of Monro (FM). Ventriculostomy was performed on six cadaveric heads using a grid of 9 entry points, comparing a 5 ml syringe with the freehand technique to reach the target. RESULTS: The first part of the radiological study showed a length from the cranial surface to the FM was overall 67,38 ± 1,03 mm. For the second part, the mean length of the 24 selected points was 68,54 ± 2,73 mm without statistical difference. In the anatomical study, the FM was reached 8 times (14.8%) with the syringe vs 31 times (57.4%) with the freehand technique, and the ventricles 43 (79.6%) vs 37 (68.5%). The mean lengths from the skull to the FM were 71.33 ± 4.21 mm. CONCLUSIONS: In this study, we showed the optimal length of a frontal ventricular catheter. We have also demonstrated that the portion of the frontal bone above the superior temporal lines matches a sphere in which the center is the FM.

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.

Update in Cushing disease: What the neurosurgeon has to KNOW, on behalf of the EANS skull base section.

Introduction: Cushing's disease is a state of chronic and excessive cortisol levels caused by a pituitary adenoma. Research question: CD is a complex entity and often entails difficulties in its diagnosis and management. For that reason, there are still controversial points to that respect. The aim of this consensus paper of the skull base section of the EANS is to review the main aspects of the disease a neurosurgeon has to know and also to offer updated recommendations on the controversial aspects of its management. Material and methods: PUBMED database was used to search the most pertinent articles published on the last 5 years related with the management of CD. A summary of literature evidence was proposed for discussion within the EANS skull base section and other international experts. Results: This article represents the consensual opinion of the task force regarding optimal management and surgical strategy in CD. Discussion and conclusion: After discussion in the group several recommendations and suggestions were elaborated. Patients should be treated by an experienced multidisciplinary team. Accurate clinical, biochemical and radiological diagnosis is mandatory. The goal of treatment is the complete adenoma resection to achieve permanent remission. If this is not possible, the treatment aims to achieving eucortisolism. Radiation therapy is recommended to patients with CD when surgical options have been exhausted. All patients in remission should be tested all life-long.

The transclival endoscopic endonasal approach (EEA) for prepontine neuroenteric cysts: report of two cases.

INTRODUCTION: The transclival endoscopic endonasal approach was used to completely remove a prepontine neuroenteric cyst in two different patients. CASE REPORTS: Full clinical improvement without postoperative complication was achieved in both cases. The postoperative hospital stay was limited to 2 and 3 days. DISCUSSION: In comparison to posterolateral skull base approaches, the transclival endoscopic endonasal approach allows direct access to the prepontine cistern without unnecessary manipulation of neurovascular structures at the cerebellopontine angle. In contrast to transoral surgery, patients may have decreased risk of infection and can be fed orally immediately without the risks of palatal and oropharyngeal dehiscence. CONCLUSION: Neuronavigation technology, strict adherence to microsurgical principles, and significant endoneurosurgical experience are strongly recommended when approaching these challenging lesions.

Contralateral Interhemispheric Transfalcine Transprecuneus Approach: Advancing Operative Angles to Deep-Seated Lesions.

The reach to expose the peritrigonal/atrial territories poses special challenges. The highly functional overlying cortices and white matter tracts, such as the optic radiations lateral to the ventricle, postcentral gyrus laterally and more superficially, and the thalamus anteroinferiorly, constrain the surgical corridors to the atrium. Standard interhemispheric or transcortical approaches involve significant retraction and resection of the normal parenchyma. In this offering, the authors describe the contralateral posterior interhemispheric transfalcine transprecuneus approach (PITTA), which provides flexible working angles while protecting the functional brain tissues. In summary, the PITTA is founded on the concept of using a contralateral operative trajectory to augment a more tangential working angle to the more difficult-to-reach lateral target through a midline route. The PITTA emphasizes the importance of operative working angles (versus necessary operative space) through less disruptive exposures as a more viable parameter for achieving desirable results.

The Smith-Robinson Approach to the Subaxial Cervical Spine: A Stepwise Microsurgical Technique Using Volumetric Models From Anatomic Dissections.

BACKGROUND: The Smith-Robinson1 approach (SRA) is the most widely used route to access the anterior cervical spine. Although several authors have described this approach, there is a lack of the stepwise anatomic description of this operative technique. With the advent of new technologies in neuroanatomy education, such as volumetric models (VMs), the understanding of the spatial relation of the different neurovascular structures can be simplified. OBJECTIVE: To describe the anatomy of the SRA through the creation of VMs of anatomic dissections. METHODS: A total of 4 postmortem heads and a cervical replica were used to perform and record the SRA approach to the C4-C5 level. The most relevant steps and anatomy of the SRA were recorded using photogrammetry to construct VM. RESULTS: The SRA was divided into 6 major steps: positioning, incision of the skin, platysma, and muscle dissection with and without submandibular gland eversion and after microdiscectomy with cage positioning. Anatomic model of the cervical spine and anterior neck multilayer dissection was also integrated to improve the spatial relation of the different structures. CONCLUSION: In this study, we review the different steps of the classic SRA and its variations to different cervical levels. The VMs presented allow clear visualization of the 360-degree anatomy of this approach. This new way of representing surgical anatomy can be valuable resources for education and surgical planning.

Infrasellar Endoscopic Endonasal Approach for a Pituitary Adenoma Extending into the Third Ventricle, with Anterior Displacement of the Pituitary Gland.

Objectives The current video presents the nuances of the infrasellar endoscopic endonasal approach for a pituitary adenoma extending into the third ventricle, with anterior displacement of the pituitary gland. Design The video analyzes the presentation, preoperative workup and imaging, surgical steps and technical nuances of the surgery, the clinical outcome, and follow-up imaging. Setting The patient was treated by a skull base team consisting of a neurosurgeon and an ENT surgeon at a teaching academic institution. Participants The case refers to 73-year-old female patient who was found to have a sellar mass after failure of vision to improve with cataract surgery. She also reported a several-month history of progressive loss of vision along with daily retro-orbital headaches. The adenoma extended into the clivus as well as in the retrosellar and suprasellar regions, eroding into the floor of the third ventricle. The normal gland was displaced anteriorly. Main Outcome Measures The main outcome measures consisted of reversal of patient symptoms (headaches and visual disturbance), recurrence-free survival based on imaging, as well as absence of any complications. Results The patient's headaches and visual fields improved. There was no evidence of recurrence. Conclusion The infrasellar endoscopic endonasal approach is safe and effective for pituitary adenomas extending into the third ventricle, with anterior displacement of the pituitary gland. The link to the video can be found at: https://youtu.be/zp_06mEyRvY .

The epitrigeminal approach to the brainstem.

OBJECTIVE Surgical approaches to the ventrolateral pons pose a significant challenge. In this report, the authors describe a safe entry zone to the brainstem located just above the trigeminal entry zone which they refer to as the "epitrigeminal entry zone." METHODS The approach is presented in the context of an illustrative case of a cavernous malformation and is compared with the other commonly described approaches to the ventrolateral pons. The anatomical nuances were analyzed in detail with the aid of surgical images and video, anatomical dissections, and high-definition fiber tractography (HDFT). In addition, using the HDFT maps obtained in 77 normal subjects (154 sides), the authors performed a detailed anatomical study of the surgically relevant distances between the trigeminal entry zone and the corticospinal tracts. RESULTS The patient treated with this approach had a complete resection of his cavernous malformation, and improvement of his symptoms. With regard to the HDFT anatomical study, the average direct distance of the corticospinal tracts from the trigeminal entry zone was 12.6 mm (range 8.7-17 mm). The average vertical distance was 3.6 mm (range -2.3 to 8.7 mm). The mean distances did not differ significantly from side to side, or across any of the groups studied (right-handed, left-handed, and ambidextrous). CONCLUSIONS The epitrigeminal entry zone to the brainstem appears to be safe and effective for treating intrinsic ventrolateral pontine pathological entities. A possible advantage of this approach is increased versatility in the rostrocaudal axis, providing access both above and below the trigeminal nerve. Familiarity with the subtemporal transtentorial approach, and the reliable surgical landmark of the trigeminal entry zone, should make this a straightforward approach.

Paratrigeminal, Paraclival, Precavernous, or All of the Above? A Circumferential Anatomical Study of the C3-C4 Transitional Segment of the Internal Carotid Artery.

BACKGROUND: Although the term paraclival carotid pervades recent skull base literature, no clear consensus exists regarding boundaries or anatomical segments. OBJECTIVE: To reconcile various internal carotid artery (ICA) nomenclatures for transcranial and endoscopic-endonasal perspectives, we reexamined the transition between lacerum (C3) and cavernous (C4) segments using a C1-C7 segments schema. In this cadaveric study, we obtained a 360°-circumferential view integrating histological, microsurgical, endoscopic, and neuroradiological analyses of this C3-C4 region and identified a distinct transitional segment. METHODS: In 13 adult, silicone-injected, formalin-fixed cadaveric heads (26 sides), transcranial-extradural-subtemporal and endoscopic-endonasal CT-guided dissections were performed. A quadrilateral area was noted medial to Meckel's cave between cranial nerve VI, anterolateral and posterolateral borders of the lateral-paratrigeminal aspect of the precavernous ICA, and posterior longitudinal ligament. Endoscopically, a medial-paraclival aspect was defined. Anatomical correlations were made with histological and neuroradiological slides. RESULTS: We identified a distinct precavernous C3-C4 transitional segment. In 18 (69%) specimens, venous channels were absent at the quadrilateral area, on the paratrigeminal border of the precavernous ICA. A trigeminal membrane, seen consistently on the superior border of V2, defined the lateral aspect of the cavernous sinus floor. The medial aspect of the precavernous ICA corresponded with the paraclival ICA. CONCLUSION: Our study revealing the juncture of 2 complementary borders of the ICA, endoscopic endonasal (paraclival) and transcranial (paratrigeminal), reconciles various nomenclature. A precavernous segment may clarify controversies about the paraclival ICA and support the concept of a "safe door" for lesions involving Meckel's cave, cavernous sinus, and petrous apex.