Posterior Interhemispheric Approach Research Articles

Microsurgical anatomy and approaches to thalamic gliomas. Part 1: A cartography guide for navigating to the thalamus. Integrating 3D model rendering with anatomical dissections.

The selection of appropriate microsurgical approaches to treat thalamic pathologies is currently largely subjective. The objective of this study was to provide a structured cartography map for surgical navigation to treat gliomas involving different surfaces of the thalamus. Fifteen formalin-fixed, silicone-injected cadavers (30 sides) were dissected, and 10 adult brain specimens (20 sides) were used to illustrate thalamic microsurgical anatomy using the Klingler fiber dissection technique. Exposures and trajectories for the six most common microsurgical approaches were depicted using MR data from healthy subjects converted into surface-rendered 3D virtual brain models. Additionally, thalamic surfaces exposed with all six approaches were color mapped on the virtual 3D model and compared side-by-side in 360° views with previously reported microsurgical approaches. These 3D models were then used in conjunction with topographic data to guide cadaveric dissection steps. There are two general surgical routes to thalamic lesions: the subarachnoid transcisternal and transcortical routes. The transcisternal route consists of the following three approaches: 1) anterior interhemispheric transcallosal approach, which exposes the anterior and superior thalamus; 2) posterior interhemispheric transcallosal approach, which exposes the posterosuperior thalamus; and 3) supracerebellar infratentorial approach, which exposes the posteromedial cisternal thalamus and can be extended laterally to approach the posterolateral thalamus by cutting the tentorium. The three transcortical approaches are the 1) superior parietal lobule approach, which exposes the posterosuperior thalamus and is particularly advantageous in the setting of hydrocephalus; 2) transtemporal gyrus approach, which exposes the inferolateral thalamus; and 3) transsylvian transinsular approach, which exposes the lateral thalamus (slightly more superiorly and posteriorly) and is advantageous for pathologies extending laterally into the peduncle, lenticular nucleus, or insula. Microsurgical approaches to thalamic gliomas continue to be challenging. Nonetheless, safe and effective cisternal, ventricular, and cortical corridors can be developed with thoughtful planning, anatomical understanding, and knowledge of the advantages, risks, and limitations of each approach. In some cases, it is wise to combine these approaches with staged procedures, as the authors demonstrate in Part 2. In Part 1 of this two-part series, they discuss thalamic microsurgical anatomy and illustrate the trajectory and exposures of all six approaches to guide decision-making. Part 2 discusses their thalamic glioma microsurgical case series, which utilizes these microsurgical approaches.

Middle third falcine meningiomas-surgical nuances for cortical venous preservation.

To improve postoperative outcome in middle third falcine meningiomas by cortical venous preservation. Falcine meningiomas arise from the falx and do not involve the superior sagittal sinus (SSS). Their complete resection is often associated with the risk of venous infarction in the eloquent cortex due to overlying superficial cortical veins on the tumors. We report one case of middle third falcine meningioma, where we used the posterior interhemispheric corridor for tumor approach. Use of the posterior interhemispheric approach, carefully raised bone flap, along with sharp dissection and vein reinforcement using fibrin glue can help to preserve the cortical veins while resecting the falcine meningiomas.

A Novel Foley Catheter-Based Brain Retraction Method for the Interhemispheric Approach: Technical Considerations and an Illustrative Video

BACKGROUNDManagement of interhemispheric pathologies requires surgical intervention through a restricted anatomical corridor ensconced within critical cerebral structures. The use of retractors to facilitate operative access may cause damage to cerebral tissue. The development of an innovative retraction technique designed to alleviate cerebral damage in such cases is imperative. OBJECTIVEIn this study, we present a novel and gentle retraction method to facilitate the interhemispheric approach. METHODSWe retrospectively examined data of nine right-handed patients who underwent surgical resection of interhemispheric lesions between 2021 and 2022. All patients underwent surgery for the first time because of this pathology. All operative specimens were histologically confirmed. Clinical characteristics, operative details, and follow-up data were retrospectively analyzed. RESULTSThe new retraction technique was successfully applied to eight tumor patients and one patient with an aneurysm. Eight patients had an anterior interhemispheric approach, and one patient had a posterior interhemispheric approach. Complete surgical excision was achieved in all patients with no postoperative complications. Postoperative Gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) showed no signs of ischemia or contusion. All patients exhibited significant improvements in their symptoms. An illustrative video that elucidates the removal of an interhemispheric epidermoid tumor, employing the anterior ipsilateral interhemispheric approach, featuring the novel retraction method. CONCLUSIONSThe ideal retraction technique during the interhemispheric approach is still a challenge. Our novel retraction technique may help minimize brain parenchymal damage during surgical resection of interhemispheric lesions.

Cavernous Malformations: What They Have Taught Us.

Cavernous Malformations: What They Have Taught Us.

Pediatric Pineal Region Tumors: Special Reference to Posterior Interhemispheric Trans-Tentorial Approach.

Pediatric pineal region tumors consist of tumors of pineal gland origin and parapineal origin. The former are comprised of germ cell tumor (GCT) and pineal parenchymal tumor. The latter originate from the surrounding neural structures, such as the midbrain and thalamus; thus, they are often benign gliomas during childhood. Pineal region tumors often cause obstructive hydrocephalus, which is the main cause of presenting symptoms. Advanced imaging discloses precise location and extension of the tumor and associated anomalies such as hydrocephalous, dissemination, hemorrhage, etc. Hydrocephalus has been managed with CSF diversion, mostly using an endoscopic third ventriculostomy. Because of different treatment paradigms for each tumor type, histological confirmation is needed either through biopsy, tumor markers for GCTs, and/or surgical resection sampling. Radical resection of these tumors remains a challenge due to their deep-seated location and involvement of delicate neural and vascular structures. Comparison of common craniotomy approaches, occipital transtentorial (OT) and infratentorial supracerebellar (ITSC), is reviewed for their advantages and disadvantages. Surgical area exposure and blind spots are important factors for successful tumor removal. The surgical techniques and nuances that the author employs for tumor resection via a posterior interhemispheric transtentorial approach are presented.

Pediatric pineal region tumors: institutional experience of surgical managements with posterior interhemispheric transtentorial approach.

Resecting pineal region tumors in children is often challenging. Several approaches have been proposed and practiced. A personal series of pediatric pineal region tumors resected through craniotomy with posterior interhemispheric occipital transtentorial (OT) approach are reviewed. We present the surgical techniques, pitfalls, and their results. Eighty patients ranging in age from 3months to 21years old, and treated over 3 decades were reviewed. Hydrocephalus caused the main presenting symptoms and was noted in 74 patients. It was treated prior to the craniotomy for tumor resection with endoscopic third ventriculostomy (ETV) in 33, external ventricular drainage in 26, and precraniotomy shunt in 15. Nine patients had ETV together with endoscopic biopsy. All patients had a parieto-occipital craniotomy in a prone position. Through a tentorial section, a gross total resection of the tumor was attempted except for germinomas. The tumor pathology showed 32 germ cell tumors (GCT), 22 benign astrocytomas, 13 pineal parenchymal tumors, 5 ATRTs, 3 papillary tumors, and 5 others. Of GCTs, 18 were teratomas. The extent of resection consisted of 55 gross total resections, 13 subtotal resections, 10 partial, and 2 biopsies with one postoperative death. Hemiparesis in 2, cerebellar ataxia in another 2, and hemiballismus in 1 were transient and improved over time. One had permanent hemisensory loss and another patient had bilateral oculomotor palsy. Postoperative homonymous hemianopia occurred in 2 patients but subsided over a short period of time. Parinaud's sign was noted in 24 patients, of which 16 were transient. The posterior interhemispheric OT approach provides a safe route and comfortable access to the pineal region inchildren. A great majority of postoperative neurological complications are the results of direct manipulations of the midbrain at tumor resection. Identification and preservation of the tumor-brain interface are of paramount importance. GCTs other than teratomas are treated with neoadjuvant chemotherapy and may eliminate the need for craniotomy. Exophytic midbrain JPAs are amenable to resection.

First documented case of intracranial falcine malignant peripheral nerve sheath tumor: illustrative case.

BACKGROUNDThe authors reported the first documented case of intracranial extraaxial nonneurofibromatosis type 1–related nontriton malignant peripheral nerve sheath tumor (MPNST) originating from the falx cerebri.OBSERVATIONSA 34-year-old man with headache, short-term memory deficit, postural instability, and blurred vision presented with a large heterogenous contrast-enhanced intraventricular cystic lesion originating from the free margin of the falx cerebri. The patient received surgery using the right posterior interhemispheric approach. Gross total resection was performed, and the inferior border of the falx cerebri was resected. The postoperative course was uneventful. Histological examination revealed hypercellular foci of neoplastic spindle cells with hyperchromatic and wavy nuclei. Hence, a diagnosis of MPNST was made based on concomitant immunochemistry findings, including mouse double minute 2 homolog focal positivity and geographic loss of H3K27me3. The patient received adjuvant radiotherapy, and recurrence was not observed.LESSONSIntracranial MPNSTs are extremely rare tumors, typically originating from the cranial nerves in the posterior cranial fossa. An even rarer variant of these tumors, referred to as malignant intracerebral nerve sheath tumors, may directly arise from the brain parenchyma. The authors reported the first case of an intracranial MPNST originating from the dura mater of the falx cerebri, acting as an extraaxial lesion with prevalent expansion in the right ventricle.

Posterior interhemispheric occipital transtentorial approach for resection of a falcotentorial meningioma.

Falcotentorial meningiomas arise along the junction of the falx cerebri and the tentorium cerebelli. The authors present a woman in her 60s with an incidentally discovered falcotentorial meningioma, approximately 3 cm in diameter, resected with a torcular craniotomy and posterior interhemispheric approach. The galenic complex was dissected away from the tumor. In the final view, the bilateral internal cerebral veins and basal veins of Rosenthal were seen. A Simpson grade I resection was achieved. The patient experienced transient contralateral hemianopsia and was discharged home. At 1-year follow-up, her neurological examination findings were unremarkable, and there was no radiographic evidence of tumor.The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2125.

Posterior interhemispheric approach for surgical removal of a choroid plexus papilloma in the ventricular atrium.

A 12 year-old boy with headaches for 2 months. Magnetic resonance imaging of the brain found a small lesion in the atrium of the right lateral ventricle. We show a posterior interhemispheric approach to the ventricular atrium through a corticotomy in the pre-cuneus and the posterior cingulate gyrus. This approach has the advantage of avoiding lesion to the optic radiation. A complete resection of the lesion was performed without complications. Anatomopathological result showed choroid plexus papilloma. This benign tumor corresponds to less than 1% of brain tumors and typically presents with signs of intracranial hypertension with hydrocephalus.

Comparison Between Transcortical and Interhemispheric Approaches to the Atrium of Lateral Ventricle Using Combined White Matter Fiber Dissections and Magnetic Resonance Tractography

The objective of this study was to compare transcortical and posterior interhemispheric approaches to the atrium using a combined approach of white matter fiber dissections and magnetic resonance (MR) tractography. Ten cerebral hemispheres were examined and dissected from the lateral-to-medial surface and from the medial-to-lateral surface, with special attention to the white matter tracts related to the atrium. MR tractography was used to show the relationship of three-dimensional white matter fibers with the atrium of the lateral ventricle and to compare with cadaveric dissection results. The atrium was related laterally to the superior longitudinal fasciculus II and III, middle longitudinal fasciculus, arcuate fasciculus, vertical occipital fasciculus, and sagittal stratum. Medially, it is related to the superior longitudinal fasciculus I, cingulum, sledge runner, and forceps major. A combined approach of cadaveric white matter fiber dissections and MR tractography were used to describe the main white matter tracts related to the posterior interhemispheric approach and the transcortical approach, providing an in-depth understanding of the three-dimensional anatomy of white matter fibers and the atrium. In the present study, among approaches examined, the posterior interhemispheric parasplenial transprecuneus approach placed fewer eloquent tracts at risk; however, traversing the sledge runner and the forceps major is unavoidable by this approach.

Posterior transcallosal intervenous-interforniceal approach to a periaqueductal tumor.

Described by Dandy in 1921, the posterior interhemispheric transcallosal approach provides an operative corridor to the pineal region, posterior third ventricle, and upper midbrain. Intervenous-interforniceal and paravenous-interforniceal variants have been utilized for midline and paramidline pathology, respectively. The intervenous-interforniceal variant capitalizes on the natural separation of the internal cerebral veins, which are found medial to the forniceal crura at this level, to provide a safe corridor to the tumor while minimizing the risk of injury to the fornices. Here, the authors describe a posterior interhemispheric transcallosal approach using the intervenous-interforniceal variant for resection of a periaqueductal pilocytic astrocytoma.The video can be found here: https://youtu.be/mtQKEXEveTg.

Early Feasibility Study of a Neurostimulator to Create Artificial Vision

Abstract INTRODUCTION Stimulation of human visual cortex is known to elicit visual perceptions that could potentially be used for creating artificial vision. The Orion Visual Cortical Prosthesis is a new device that is intended to restore some functional vision to blind patients. METHODS The device comprises an implant (consisting of an electronics package, receiving antenna, and an electrode array with 60 electrodes); glasses with a video camera; and a video processing unit (VPU). The camera collects real-time visual information, which is then processed by the VPU and converted to stimulation patterns sent to electrode array. The electronics are skull mounted with the subdural array implanted through a posterior interhemispheric approach. This is a 5-yr study of subjects who are bilaterally blind with bare light or no light perception due to non-cortical etiology. RESULTS A total of 6 subjects have been implanted in 2 centers. As of May 1, 2019, average implant duration was 11.1 mo (range 3.4-15.0 mo). Average age at time of implant was 50.3 yr. Cause of blindness included trauma (2), pediatric glaucoma (2), optic neuropathy (1), and endophthalmitis (1). One serious adverse device event (seizure) has been reported. Average thresholds ranged from 1.6 to 3.7 mA across the 6 subjects. At 6 mo postimplant, 3 of 5 subjects performed significantly better with the system on than off on a light localization task; 2 subjects performed better on a direction of motion task, and no subjects had measurable visual acuity. All 5 subjects were rated as receiving “positive” or “mild positive” benefit on a functional vision assessment. One-year adverse event and visual performance data for the first 5 subjects will be presented and compared to results from a commercially-available retinal prosthesis. CONCLUSION Safety and performance results of the first 5 subjects as of 6 mo postimplantation appear encouraging.

Posterior Interhemispheric Precuneal Approach: Fundamental Principles and Case Illustration: 3-Dimensional Operative Video

Peritrigonal lesions are deeply seated and are surrounded by critical neurovascular structures. Traditional transcortical approaches carry the risk of damage to important surrounding white matter tracts. In this regard, a posterior interhemispheric approach gives a more direct and less invasive route and therefore is a reasonable alternative to transcortical approaches. The 3-dimensional video includes illustrations and animations showing the anatomy of the white matter tracts around the trigone and explains the physiological basis of posterior interhemispheric precuneal approach to this complex region. This also includes a 3-dimensional operative video of the same approach in a 50-yr-old male patient with left periatrial lesion describing surgical techniques and nuances. An informed written consent has been obtained from the patient.

The interhemispheric approach in children: our experience and review of the literature.

The interhemispheric approach (IA) has been extensively described for treating pathologies located at the lateral or third ventricle, pineal region, and periventricular locations. While these anatomical locations are the target of many pediatric pathologies, very few series have analyzed the morbidity and outcome of the IA in children. The aim of this study is to describe our experience using the IA in children, emphasizing the approach-related morbidity. Twenty-six patients underwent 28 procedures using the IA between the years 2012 and 2016. Data for these patients was retrospectively analyzed. Surgical and approach-related morbidity were collected and analyzed. The mean age of the cohort was 10.1 ± 4.2years and included 15 females (57.7%). Approach-related morbidity occurred following eight surgeries (28.6%; seven with anterior IA and one with posterior IA), including two pseudomeningoceles (7.1%), three persistent subdural effusions (10.7%), of which two were locally drained and one required subduro-peritoneal shunting, one epidural bleed (3.6%) which resolved spontaneously, and two infections (3.6%) treated with antibiotics. Cerebrospinal fluid leaks, supplementary motor area syndrome, seizures, and subdural hematomas did not occur in any of the patients. None of the approach-related complications led to permanent morbidity or to mortality. The IA for lesions in and around the ventricular system is feasible and associated with a low permanent complication rate. When choosing this approach, the morbidity, although rarely permanent, should be considered.

One burr-hole craniotomy: Posterior interhemispheric approach in Helsinki Neurosurgery.

Background:In this video abstract, we present a one burr-hole craniotomy for the posterior interhemispheric approach developed in Helsinki Neurosurgery to access posteriorly the medial surface of cerebral hemispheres, falx cerebri, and deep midline cerebrovascular structures. Therefore, preoperative imaging is essential to achieve an optimal operative corridor for a safest and more effcient approach.Case Description:The patient with a papillary tumor of the pineal region is placed in sitting position. A midline single-layer skin incision is made in front of the superior sagittal sinus. Strong retraction maintains a clean space for craniotomy. Aiming to reduce the risk of sinus transgression or cortical veins damaging in the eloquent frontal–parietal area, a burr-hole is made over the superior sagittal sinus at the anterior border of the bone flap and the bone is detached from the dura posteriorly with blunt dissectors. Thus, proximal detachment of the dura under some visual control remains safe. A long blunt flexible dissector is used during this stage in case of elderly patients with an adherent dura. Craniotomy around the superior sagittal sinus is performed to expose 2–3 cm of the dura lateral to the sagittal sinus according to the exact location of the lesion. Moreover, craniotomy extends slightly over the contralateral side to allow some retraction of the sagittal sinus. Two cuts, from both sites of the burr-hole, are joined along the posterior midline. A few drill holes are made for tack-up sutures. Finally, a hemostatic agent covers the sagittal sinus and a sinus-based dura opening is performed under the microscope.Conclusion:The described one burr-hole craniotomy may represent a more efficient manner for performing a posterior interhemispheric approach.Videolink:http://surgicalneurologyint.com/videogallery/posterior-interhemispheric-approach

Microsurgical Resection After Failed Gamma Knife Radiosurgery of Papillary Tumor of the Pineal Gland.

Abstract Primary papillary tumors of the pineal region (PTPR) are rare entities with distinct histopathological characteristics. Most common surgical approaches include the supra-cerebellar infratentorial corridor or the occipital interhemispheric approach. Gamma knife radiosurgery (GKRS) is an acceptable treatment modality for parenchymal tumors of the pineal gland, and often used as a primary treatment modality for asymptomatic and indolent lesions, and as an adjunct to surgical resection. In this presentation, we describe the surgical nuances of posterior interhemispheric approach in an elderly male with a previously failed empirical GKRS. Intraoperatively, the tumor was mostly avascular, presumed to be due to prior GKRS; however, a good tumor-brain interface allowed a gross total resection of the mass. Histopathological examination of the mass was consistent with PTPR. Post-operative course was uneventful and long-term follow up showed no signs of tumor recurrence. The video discusses radiological findings, clinic-pathological correlates, and emphasizes on key microsurgical techniques including the significance of patient positioning and incision type for meticulous resection of pineal tumors.

Chapter 29 - Thalamic cavernous malformations

Cavernous malformations of the thalamus represent a particularly complex subset of cavernous malformations because of the highly eloquent nature of the involved tissue and their deep location. The decision about whether to operate on any individual lesion depends on the specific location of the lesion within the thalamus, the nature of the patient's symptoms, and the patient's history. When surgery is recommended, the approach must be chosen carefully. Each part of the thalamus is reached by a different surgical approach. These approaches include the orbitozygomatic approach to the anteroinferior thalamus, the anterior interhemispheric transcallosal approach to the medial thalamus, the anterior contralateral interhemispheric transcallosal approach to the lateral thalamus, the posterior interhemispheric transcallosal approach to the posterosuperior thalamus, the parieto-occipital transventricular approach to the lateral posteroinferior thalamus, and the suboccipital supracerebellar infratentorial/transtentorial approach to the medial posteroinferior thalamus. Careful attention to safe entry zones and image guidance can allow safe removal of these lesions when necessary.

The Posterior Transcallosal Approach to the Pineal Region and Posterior Third Ventricle: Intervenous and Paravenous Variants

There are a number of surgical approaches to the posterior third ventricle and pineal region, each with its associated advantages and disadvantages. To present our experience with the posterior interhemispheric transcallosal approach and to analyze the indications, technique, and outcomes. A retrospective study was conducted to identify and analyze all children and young adults who underwent the posterior transcallosal approach from July 2010 to March 2015. Perioperative data included patient demographics, signs and symptoms on presentation, tumor characteristics (type, origin, and size), complications, and clinical and radiographic outcome at final follow-up. Twenty-two patients (9 female, 13 male) were identified in 24 cases with a mean age of 10.5years (range, 3-32years). The most common tumor type was pineoblastoma (n = 6). Eleven patients underwent gross total resections; 11 underwent subtotal resections; and 2 tumors were biopsied. The intervenous operative corridor was used in 15 cases; the paravenous was used in 9. Of the 22 patients, 19 experienced 31 total postoperative events. There were 12 instances of contralateral weakness. Retraction-related hemiparesis was usually temporary; resection-related hemiparesis lasted longer. There were no complications related to occlusion of one or more bridging cortical veins or from thrombosis of 1 internal cerebral vein. Eight patients have died of tumor progression, and of the remaining 14 patients, only 1 patient to date has developed local progression. The posterior interhemispheric transcallosal approach allows resection of tumors located within the pineal region, posterior third ventricle, and thalamus. New postoperative neurological deficits can occur; however, many will improve significantly or resolve completely over time.

Bypass Revascularization Applied to the Posterior Cerebral Artery

The application of bypass procedures to the posterior cerebral artery (PCA) in combination with proximal clipping or trapping is a useful option for the treatment of complex posterior circulation aneurysms, especially those of the PCA. Because of its course around the midbrain through various cisterns, different approaches are required to access the PCA. The presented study analyzes a retrospective case series of bypass procedures to the PCA to investigate the relevant treatment strategies and their outcomes. Seven patients with bypass procedures to the PCA bypass were analyzed. The location of the aneurysms, approaches, site of anastomosis, bypass patency, pre- and postoperative modified Rankin Scale scores, and transient and permanent morbidity were assessed. Analyzed patients were treated for intracranial aneurysm located on the P2 (n= 3) or P3 (n= 2) of the PCA, bilateral vertebral artery dissecting aneurysm (n= 1) or internal carotid artery-posterior communicating artery aneurysm (n= 1). The following approaches were used: anterior temporal approach (n= 2), anterior temporal approach combined with subtemporal approach (n= 2), combined transpetrosal approach (n= 1), posterior interhemispheric approach (n= 1), and posterior interhemispheric approach with subtemporal approach (n= 1). All bypasses were patent. Permanent morbidity occurred in 2 patients via cognitive dysfunction (n= 1) and hemiparesis (n= 1). Bypass revascularization of the PCA territory is effective for the treatment of complex vascular lesions affecting the posterior circulation. To address the various surgical segments of the PCA, different approaches are required. Combined approaches allow access to the PCA proximal and distal from the lesion.

Choroid Plexus Carcinoma: A Rare Tumor in Adult

Background: Choroid plexus carcinoma is a highly aggressive malignant, infrequent tumor with poor prognosis. About 80% of choroid plexus carcinoma occurs in children, but it is uncommon in adults. Because of the rarity of the choroid plexus carcinoma, there is no established treatment protocol for this malignancy. Case Description: A 21-year-old man with past medical history of asthma presented to us with the chief complaint of morning headache for one month. His brain magnetic resonance imaging (MRI) showed a mass in the trigone and occipital horn of the left lateral ventricle. He had undergone a left occipitoparietal craniotomy, posterior interhemispheric precuneus approach with grossly total removal of the tumor. The histology examination of the tumor proved to be choroid plexus carcinoma. This patient achieved a favorable outcome after having a grossly complete surgical resection followed by postoperative adjuvant radiotherapy and chemotherapy. Conclusions: Choroid plexus carcinoma is aggressive and is associated with dismal prognosis. The 5-year survival rates for choroid plexus carcinoma vary between 10% and 50%. Currently, there is no established treatment protocol for choroid plexus carcinoma. Complete resection of this malignant tumor is the primary goal of treatment since it allows best chance of survival and improves the overall prognosis.