Superior frontal sulcus: a non-eloquent corridor for cavernomas of the internal capsule

Introduction

Deep cavernomas of eloquent areas, located in the region of the basal nuclei and thalamus, account for 9 to 36% of these encephalic vascular malformations. Internal capsule cavernomas are particularly challenging, as they are surrounded by important projection fibers and their manipulation can lead to permanent deficits. To demonstrate through surgical cases that cavernomas of the internal capsule can be approached by frontal craniotomy, via the superior frontal sulcus, in a curative manner and with low morbidity.

Methods

We presented two cases of cavernomas of the internal capsule operated, whose treatment was microsurgical resection via frontal craniotomy and access to the lesion via the superior frontal sulcus, described step-by-step. To elucidate the rationale behind the decision, we used preoperative images with an emphasis on the patients' tractography and the importance of comparing these images with anatomical specimens dissected in the neuroanatomy and microsurgery laboratory.

Results

The two cases of internal capsule cavernomas, one in the anterior limb and the other in the posterior limb, were treated surgically via the superior frontal sulcus.

Discussion

Both patients showed radiological cure and clinical improvement in the post-operative segment. The patient consented to the procedure and to the publication of his/her image. Treatment of internal capsule cavernomas via the superior frontal sulcus has proven to be a safe and effective option.

Posterior Transtemporal Approach to a Thalamic Cavernous Malformation: 2-Dimensional Operative Video

Cavernous malformations (CMs) account for 10%-15% of all vascular malformations and represent the second most common type of cerebral vascular lesion.1 They typically occur in the cerebral subcortex or white matter.2 CMs located in the thalamus are rare.3 When we isolate the group of thalamic CMs, we find a bleeding risk of >5% per year, with a rebleeding rate exceeding 60%, often occurring within 1 year of the initial bleeding.1 The deep location and proximity to eloquent brain regions make thalamic CMs challenging for neurosurgeons.4,5 Surgeons can access the posterolateral thalamus through various surgical approaches, such as transcallosal transventricular, supracerebellar transtentorial, intraparietal sulcus, and transcortical methods. Selecting the best surgical approach requires considerable expertise, considering the patient's preoperative condition and the lesion's location.6-12 We discuss a complex case involving a 24-year-old patient with a right thalamic cavernoma and a history of 3 prior bleeding events. We present a step-by-step transcortical approach through the posterior portion of the superior temporal gyrus (Video 1). The patient consented to the procedure and publication of images. We demonstrate how the transtemporal posterior trajectory provides an optimal working corridor for safely removing this cavernous malformation without introducing new deficits.

Recurrent Artery of Heubner Guiding the Clip Application for Internal Carotid Artery Bifurcation Aneurysm: 2-Dimensional Operative Video

Aneurysms of the bifurcation of the internal carotid artery (ICA) represent approximately 5% of intracranial aneurysms and tend to occur in younger patients.1-3 They typically have a superior orientation, in close relationship with the medial (branches of the anterior cerebral artery, segment A1) and lateral (branches of the middle cerebral artery, segment M1) lenticulostriate arteries (LSA), including recurrent artery of Heubner (RAH). RAH commonly originates in the junction of A1 and A2, courses medially to laterally between LSA and anterior cerebral artery, ICA bifurcation, and middle cerebral artery before entering the lateral portion of the anterior perforated substance.4-7 Damage to these arteries are catastrophic. This complex vascular anatomy makes treatment challenging, either endovascular or microsurgical.8-13 We present a video case of microsurgical clipping for the left ICA bifurcation aneurysm. This study was approved by the ethics committee of our institution. The patient, a 46-year-old man, was diagnosed with an unruptured ICA bifurcation aneurysm during workup for intermittent headache. Morphological characteristics of the aneurysm supported intervention over conservative treatment. Digital subtraction angiography showed a prominent proximal RAH crossing between the aneurysm neck and LSA, providing anatomical protection for clip application. Microsurgical clipping was chosen, and the procedure went uneventfully. The patient consented to the procedure and to the publication of his/her image. We discussed and demonstrated throughout the video how we used this anatomic variation and trajectory of the RAH to prevent clipping of LSA unwittingly and achieve complete occlusion of the aneurysm neck.

Case report: Association between PTEN-gene variant and an aggressive case of multiple dAVFs

Introduction

Mutations of the phosphatase and tensin homolog (PTEN) gene have been associated with a spectrum of disorders called PTEN hamartoma tumor syndrome, which predisposes the individual to develop various types of tumors and vascular anomalies. Its phenotypic spectrum includes Cowden syndrome (CS), Bannayan-Riley-Ruvalcaba syndrome (BRRS), Proteus syndrome, autism spectrum disorders (ASD), some sporadic cancers, Lhermitte-Duclos disease (LDD), and various types of associated vascular anomalies.

Clinical presentation

A previously healthy 27-year-old woman was experiencing visual scintillating scotomas and mild chronic headaches for the past 2 years. The initial computed tomographic (CT) and magnetic resonance imaging (MRI) scans did not reveal any abnormalities, but the possibility of pseudotumor cerebri was considered. Furthermore, a cerebral angiogram showed a posterior fossa dural arteriovenous fistula (dAVF), which was initially treated through embolization. However, in spite of proper treatment, this patient experienced multiple recurrent dAVFs in different locations, requiring multiple embolizations and surgeries. Despite exhibiting altered cerebral perfusion and hemodynamics, the patient did not display any significant symptoms until she experienced a sudden stroke resulting from deep venous thrombosis, which was not associated with any medical procedures or medication use. A comprehensive analysis was performed due to the aggressive nature of the dAVFs. Surprisingly, exome sequencing of a blood sample revealed a PTEN gene variant in chromosome 10, indicative of Cowden syndrome. However, no tumors or other vascular lesions were detected in other systems that would constitute Cowden syndrome.

Conclusion

The rapid formation of multiple and complex dAVFs, coupled with not meeting the criteria for any other PTEN-related syndrome, unequivocally leads to the presentation of a novel phenotype of the PTEN germline variant.

Enhancing the Microneurosurgical Training: Development of the Folded Placenta Model for Simulation of the Deep Operative Field Challenges of Cranial Procedures

BACKGROUND AND OBJECTIVE

Neurosurgery relies heavily on advanced manual skills, necessitating effective training models for skill development. While various models have been utilized, the human placenta has emerged as a promising candidate for microneurosurgical training due to its anatomical similarities with cerebral vasculature. However, existing placenta models have primarily focused on simulating superficial procedures, often neglecting the complexities encountered in deep operative fields during cranial surgeries.

METHODS

This study obtained ethical approval and implemented a modified placenta model to address the limitations of existing training models. The key modification involved folding the placenta and placing it within a rigid container, closely mimicking the structural challenges of cranial procedures. The placenta preparation followed a standardized protocol, including the use of specialized equipment for documentation.

RESULTS

The primary feature of the modified model is the folded placenta within the rigid container, which replicates cranial anatomy. This innovative approach enables trainees to engage in a comprehensive range of microsurgical exercises, encompassing vessel dissection, aneurysm clipping, tumor resection, and more. The model successfully mirrors the complexities of real cranial procedures, providing a realistic training experience.

CONCLUSIONS

The presented modified placenta model serves as an effective tool for simulating the conditions encountered in deep cranial surgeries. By accurately replicating the challenges of deep operative fields, the model significantly enhances the training of neurosurgical residents. It successfully prepares trainees to navigate the intricacies and difficulties inherent in real cranial surgeries, thus contributing to improved surgical skills and readiness for neurosurgical practice.

Resection of the quadrangular lobule of the cerebellum to increase exposure of the cerebellomesencephalic fissure: an anatomical study with clinical correlation

OBJECTIVE

The lateral aspect of the cerebellomesencephalic fissure frequently harbors vascular pathology and is a common surgical corridor used to access the pons tegmentum, as well as the cerebellum and its superior and middle peduncles. The quadrangular lobule of the cerebellum (QLC) represents an obstacle to reach these structures. The authors sought to analyze and compare exposure of the cerebellar interpeduncular region (CIPR) before and after QLC resection and provide a case series to evaluate its clinical applicability.

METHODS

Forty-two sides of human brainstems were prepared with Klingler's method and dissected. The exposure area before and after resection of the QLC was measured and statistically studied. A case series of 59 patients who underwent QLC resection for the treatment of CIPR lesions was presented and clinical outcomes were evaluated at 1-year follow-up.

RESULTS

The anteroposterior surgical corridor of the CIPR increased by 10.3 mm after resection of the QLC. The mean exposure areas were 42 mm2 before resection of the QLC and 159.6 mm2 after resection. In this series, ataxia, extrapyramidal syndrome, and akinetic mutism were found after surgery. However, all these cases resolved within 1 year of follow-up. Modified Rankin Scale score improved by 1 grade, on average.

CONCLUSIONS

QLC resection significantly increased the exposure area, mainly in the anteroposterior axis. This surgical strategy appears to be safe and may help the neurosurgeon when operating on the lateral aspect of the cerebellomesencephalic fissure.

The long-term effect on functional outcome of endoscopic brainwashing for intraventricular hemorrhage compared to external ventricular drainage alone: A retrospective single-center cohort study

Background

Intraventricular hemorrhage (IVH) is a complex condition with both mechanical and chemical effects, resulting in mortality rates of 50-80%. Recent reports advocate for neuroendoscopic treatment, particularly endoscopic brainwashing (EBW), but long-term functional outcomes remain insufficiently explored. This study aims to outline the step-by-step procedure of EBW as applied in our institution, providing results and comparing them with those of external ventricular drainage (EVD) alone.

Methods

We performed a retrospective analysis of adult patients with IVH who underwent EBW and patients submitted to EVD alone at our institution. All medical records were reviewed to describe clinical and radiological characteristics.

Results

Although both groups had similar baseline factors, EBW patients exhibited a larger hemoventricle (median Graeb score 25 vs. 23 in EVD, P = 0.03) and a higher prevalence of chronic kidney disease and diabetes. Short-term mortality was lower in EBW (52% and 60% at 1 and 6 months) compared to EVD (80% for both), though not statistically significant (P = 0.06). At one month, 16% of EBW patients achieved a good outcome (Modified Rankin scale < 3) versus none in the EVD group (P = 0.1). In the long term, favorable outcomes were observed in 32% of EBW patients and 11% of EVD patients (P = 0.03), with no significant difference in shunt dependency.

Conclusion

Comparing EBW and EVD, patients submitted to the former treatment have the highest modified Graeb scores and, at a long-term follow-up, have better outcomes, demonstrated by the improvement of the patients in the follow-up.

Microsurgical Resection for Cavernous Malformation of the Uncus: 3D-Operative Video

Cavernous malformations (CMs) are rare and often oligosymptomatic vascular lesions. The main symptoms include seizure and focal neurologic deficits.1-3 Depending on the symptomatology, location, size, and risk factors for bleeding, like the presence of a developmental venous anomaly, CMs can be highly morbid. Thus surgical resection may be considered. Deep-seated and eloquent CMs, like those in the uncus, can be challenging.4,5 In Video 1, we present a 23-year-old male adult who developed focal seizures (i.e., oral automatisms) after an episode of sudden intense headache 1 year ago. His neurologic examination was unremarkable. The patient consented to the procedure and publication of his image. Nevertheless, his magnetic resonance images showed an uncal 2-cm Zabramski type I CM. We exposed the insula and its limen through a right pterional craniotomy and transsylvian corridor. During the video, we discuss the surgical nuances to access and resect this CM lesion en bloc while preserving important vascular structures and white matter tracts. Postoperative neuroimaging demonstrated total resection. In postoperative day 1, the patient had 1 episode of generalized seizure and evolved with contralateral hemiparesis. The patient had a good recovery and was discharged on postoperative day 21. At the 6-month follow-up, the patient had no new epileptic events and presented complete weakness improvement. Through this minimally invasive and well-known surgical corridor, we preserve the mesial and lateral portion of the temporal lobe, reducing the risk of lesions to the Meyer loop and limbic association area.

Case report: Mirror paraclinoid aneurysm associated with mirror clinoidal meningioma

Introduction

Clinoidal meningiomas and paraclinoid aneurysms are individually uncommon, with the coexistence of mirror paraclinoid aneurysms and clinoidal meningiomas presenting an even rarer scenario. While the association between meningiomas and aneurysms is documented, the simultaneous presence of mirror lesions for both pathologies is not reported in the literature.

Clinical presentation

We report a 62-year-old female with a three-month history of moderate bifrontal headaches. Magnetic Resonance Angiography (MRA) revealed mirror paraclinoid aneurysms, prompting surgical intervention. During the procedure, mirror clinoidal meningiomas were incidentally discovered. The left aneurysm was addressed first due to higher rupture risk, followed by the right aneurysm 3 months later. Both meningiomas were confirmed as Transitional Meningiomas (Grade 1; OMS, 2021). The aneurysms were successfully clipped, and the patient had an excellent postoperative outcome.

Conclusion

This case represents a unique occurrence of mirror ophthalmic segment internal carotid artery aneurysms associated with mirror clinoidal meningiomas, a combination not previously reported. Despite the limitations of MRA in detecting small meningiomas, it remains a valuable non-invasive screening tool for neurovascular diseases. The case underscores the need for further research to elucidate the association between cerebral aneurysms and meningiomas.

Topographical Systematization of Human Placenta Model for Training in Microneurosurgery

BACKGROUND

Neurosurgical training continuously seeks innovative methods to enhance the acquisition of essential technical skills for neurosurgeons worldwide. While various training models have been employed, few truly replicate real-life conditions optimally. Human placenta is a good model for neurosurgical microsurgery training due to its anatomic similarities to neurovascular structures. Placental vessels exhibit a branching pattern and caliber comparable with intracranial vessels, making them suitable for practicing microsurgical techniques. The study aims to delineate the anatomic zones of the placenta and propose a segmented training model, resulting in a reproducible, cost-effective, and realistic neurosurgical microsurgery training environment.

METHODS

Twenty human placentas were meticulously prepared, injected with dyes, and categorized into zones on the basis of anatomic features. Measurements of placental vessels were recorded and compared with cerebral vessels. The placenta was divided into 4 quadrants to facilitate specific training techniques.

RESULTS

Our results revealed varying vessel diameters across placental zones, closely resembling cerebral vessels. Different microsurgical techniques were applied to specific placental zones, thereby optimizing training scenarios. The applicability section described exercises such as membrane dissection, vessel skeletonization, aneurysm creation, vascular bypass, and tumor dissection within the placental model, providing detailed guidance on the zones suitable for each exercise.

CONCLUSIONS

Human placenta serves as an effective microsurgical training model for neurosurgery, enhancing neurosurgeons' skills through anatomic segmentation. Integrating this model into training programs can significantly contribute to skill acquisition and improved surgical outcomes. Further research is warranted to refine and expand its utilization, complemented by clinical experiences and other simulation tools.

The Technique for Transorbital Ventricular Puncture: An Anatomic Approach

BACKGROUND AND OBJECTIVES

Transorbital ventricular puncture is a minimally invasive described procedure with poor landmarks and anatomic references. This approach can be easily performed to save patients with intracranial hypertension, especially when it is secondary to an acute decompensated hydrocephalus. This study aims to describe anatomic structures and landmarks to facilitate the execution of transorbital puncture in emergency cases.

METHODS

We analyzed 120 head computed tomographies to show the best area to perform the procedure in the orbital roof. Two adult cadavers (4 sides) were punctured in the predetermined area. Angles, distances, landmarks, and anatomic structures were registered. This approach to the ventricular system may be performed at bedside to relieve intracranial hypertension only in specific cases.

RESULTS

The perforation point is 2.5 cm (female) or 3.0 cm (male) lateral to the midline and immediately inferior to the superciliary arch. A vertical line, parallel to midline, was drawn on the outer edge of the patient's forehead, the needle was 45° inferiorly and 20° medially and then progressed 2.0 cm backwards to reach the bone perforation point. After that, it was advanced another 4.5cm approximately until it reached the anterior horn of the lateral ventricle.

CONCLUSION

Based on statistical and experimental evidences, we were able to establish reliable anatomic reference points to access the anterior horn of the lateral ventricle through transorbital puncture.

Orbitozygomatic Transsylvian Resection of a Craniopharyngioma: A Step-by-Step Guide

Adamantinomatous craniopharyngioma (ACP) is a rare sellar region tumor seen in 0.5-2 cases per million persons each year,1 presenting a bimodal distribution that peaks at 5-15 years in children and 45-60 years in adults.2 Arising from embryonic remnants of the Rathke pouch epithelium, ACPs are associated with calcifications in 90% of cases and grow cranially toward the floor of the diencephalon.1 Craniopharyngiomas are benign but locally aggressive tumors, with microsurgery being the best chance of cure.3 The natural history is to compress the optic apparatus and hypothalamic-pituitary axis as they expand, with a propensity to encase the carotids. Endoscopic transbasal approaches have gained wide acceptance in the management of these tumors.4-6 However, open microsurgical approaches via pterional and orbitozygomatic craniotomies afford wider visualization of different corridors that help mitigate the surgical risks.7-9 The orbitozygomatic craniotomy allows lesions that extend above the optic chiasm to be safely approached from an inferior-to-superior corridor.9 The wide exposure of the basal arachnoid cisterns allows protection of the lenticulostriate perforators during resection.8-11 We demonstrate a step-by-step orbitozygomatic approach with dissection of the sylvian, carotid, carotid-oculomotor, chiasmatic, and lamina terminalis cisterns that allowed safe resection of a third ventricular ACP. The patient was a male in his 70s, who presented with progressive headaches and visual impairment. Magnetic resonance imaging showed a multicystic suprasellar lesion extending through the third ventricle. The surgery was performed with no complication (Video 1). Postoperative vision stabilized, and magnetic resonance imaging showed complete resection.

Decibel Decisions: The Concept of Intracranial Aneurysm Surgery With a Decibel Meter on Two Surgical Cases

The present cases were used to investigate the reliability of the intraoperative decibel meter as an objective method of clipping efficiency in cerebral aneurysm surgery and to assess the impact of this method on the surgical procedure itself. Different methodologies have been developed and applied to directly or indirectly evaluate the placement of a clip, for example, intraoperative digital subtraction angiography (DSA), intraoperative micro-Doppler ultrasonography, and, more recently, indocyanine green (ICG). We included two patients with a previously non-treated unruptured brain aneurysm. In both patients, intraoperative micro-Doppler was used in combination with a decibel meter app. Here, we present the cases of two patients. In patient one, the pre-clipping average sound level/equivalent continuous sound pressure level (Avg/Leq) was 96.7 dB, while the post-clipping Avg/Leq was 94.4 dB, indicating a reduction in sound level after clipping. Similarly, the pre-clipping time-weighted average noise level (TWA) was 1.2%, while the post-clipping TWA was 0.5%, indicating a decrease in exposure dose after clipping. In patient two, the average sound level for the post-clipping measurement (94.2 dB) was higher than the pre-clipping measurement (93.5 dB), but the difference was not statistically significant. These cases indicate the potential for using sound measurements as a reliable indicator of adequate aneurysm occlusion during clipping procedures. Further research is needed to confirm these findings.

Unusual Spinal Foraminal Hemangioblastoma With Prominent Arteriovenous Shunt

Von Hippel-Lindau (VHL) disease is a rare neurocutaneous disorder characterized by multiple benign and malignant tumors involving different organs (renal, adrenal, pancreas, liver, urogenital system, central nervous system, and head and neck region) due to mutations in the VHL tumor suppressor gene. Here, we describe a patient with unknown VHL disease who has complained of hypoesthesia of the right lower limb for about six years. A lumbar MRI was performed and revealed an expansive foraminal lesion at the right L3-L4 level and multiple serpiginous intradural and extramedullary flow voids involving the dorsal aspect of the spinal cord. The patient underwent digital subtraction angiography to exclude a spinal dural arteriovenous fistula, which revealed imaging features suggestive of spinal hemangioblastoma. In the presence of a spinal hemangioblastoma, a brain MRI was performed for further evaluation to rule out the possible diagnosis of VHL disease, and a solitary hemangioblastoma on the right cerebellar hemisphere was found. The patient underwent lumbar spine surgery, confirming the suspicious diagnosis of hemangioblastomas related to VHL disease.

Risks for Oculomotor Nerve Palsy and Time to Recovery After Surgical Clipping of Posterior Communicating Artery Aneurysms: A Multicenter Retrospective Cohort Study

BACKGROUND

Aneurysms of the posterior communicating segment of carotid artery (PcomA) have a high risk of rupture; when these nonruptured aneurysms are associated with oculomotor nerve palsy (ONP), the risk of rupture increases compared with asymptomatic nonruptured PcomA.

OBJECTIVE

To retrospectively analyze the risk factors involved in ONP secondary to PcomA aneurysm and to study the factors involved in the recovery time of ONP once it is established.

METHODS

This was a retrospective study of patients from 10 neurosurgery centers from October 2008 to December 2020. We analyzed age at diagnosis, presence of compressive neuropathy of the oculomotor nerve, presence of aneurysm rupture, largest aneurysm diameter, aneurysm projection, smoking, hypertension, diabetes, time between diagnosis and surgical treatment, as well as the outcome.

RESULTS

Approximately 1 in 5 patients (119/511 23.3%) with a PcomA presented with ONP. We found that patients with aneurysms measuring greater than or equal to 7.5 mm were 1.6 times more likely to have ONP than those with aneurysms smaller than 7.5 mm. In our study, the prevalence of smoking in the PcomA + ONP group was 57.76%, and we also found that smokers were 2.51 times more likely to develop ONP. A total of 80.7% showed some degree of improvement, and 45.4% showed complete improvement with a median recovery time of 90 days.

CONCLUSION

This study showed that 80.7% of patients with PcomA aneurysms undergoing surgical treatment with aneurysm clipping showed some degree of improvement of the ONP, with a median time to recovery between 90 and 120 days.

Cadaveric Sheep Head Model for Anterior Clinoidectomy in Neurosurgical Training

BACKGROUND

Anterior clinoidectomy is an important procedure used in treatment of a range of pathologies of frontotemporal region, both vascular and tumoral. Mastering of this technique requires high level of manual skills training. The objective of the study is to describe easily accessible and cheap alternative model of anterior clinoidectomy, with a principal focus on the significance of mastering technical skills and training tactile feedback.

METHODS

Five cadaveric sheep heads (10 sides) fixed in formalin and alcohol silicone injected, were used to simulate extra dural (5 sides) and intradural (5 sides) and one head was used to prepare anatomical specimen for better demonstration of anatomy of the paraclinoid region.

RESULTS

Comparative anatomical analysis between ovine and human anterior clinoid process was performed. Using cadaveric sheep models all principal steps of the procedure, both in extradural and intradural route, were imitated.

CONCLUSIONS

Cadaveric sheep head model serves a good model of anterior clinoidectomy first in regard of manual skills training which can serve a good alternative to human cadaveric training.

Case report: Delayed outflow obstruction of a DVA: A rare complication of brainstem cavernoma surgery

Introduction

Developmental venous anomalies (DVAs) are considered variants of normal transmedullary veins. Their association with cavernous malformations is reported to increase the risk of hemorrhage. Expert consensus recommends meticulous planning with MR imaging, use of anatomical “safe zones”, intraoperative monitoring of long tracts and cranial nerve nuclei, and preservation of the DVA as key to avoiding complications in brainstem cavernoma microsurgery. Symptomatic outflow restriction of DVA is rare, with the few reported cases in the literature restricted to DVAs in the supratentorial compartment.

Case

We present a case report of the resection of a pontine cavernoma complicated by delayed outflow obstruction of the associated DVA. A female patient in her 20's presented with progressive left-sided hemisensory disturbance and mild hemiparesis. MRI revealed two pontine cavernomas associated with interconnected DVA and hematoma. The symptomatic cavernoma was resected via the infrafacial corridor. Despite the preservation of the DVA, the patient developed delayed deterioration secondary to venous hemorrhagic infarction. We discuss the imaging and surgical anatomy pertinent to brainstem cavernoma surgery, as well as the literature exploring the management of symptomatic infratentorial DVA occlusion.

Conclusion

Delayed symptomatic pontine venous congestive edema is extremely rare following cavernoma surgery. DVA outflow restriction from a post-operative cavity, intraoperative manipulation, and intrinsic hypercoagulability from COVID-10 infection are potential pathophysiological factors. Improved knowledge of DVAs, brainstem venous anatomy, and “safe entry zones” will further elucidate the etiology of and the efficacious treatment for this complication.

The posterior-transcallosal approach to a choroidal fissure AVM: a video case of how to adapt a “bridging vein free” corridor to this complex region

Choroidal fissure arteriovenous malformations (ChFis-AVMs) are uncommon and challenging to treat due to their deep location and pattern of supply.¹ The choroidal fissure lies between the thalamus and fornix, from the foramen of Monroe to the inferior choroidal point.² AVMs in this location receive their supply from the anterior, lateral posterior choroidal artery and medial posterior choroidal arteries and drain to the deep venous system.³ The anterior-transcallosal corridor to the ChFis is favored due to the ease in opening the taenia fornicis from the foramen Monroe, and it increases in length for lesions located more posteriorly.^4-7 We present a case of a posterior ChFis-AVM. The patient, a previously healthy woman in her 20s, presented with a sudden severe headache. She was diagnosed with intraventricular hemorrhage. This was managed conservatively with subsequent magnetic resonance imaging and digital subtraction angiography revealing a ChFis-AVM at the body of the left lateral ventricle, between the fornix and superior layer of the tela choroidae. It received its supply from the left lateral posterior choroidal artery and medial posterior choroidal artery and drained directly into the internal cerebral vein, classified as Spetzler-Martin grade II.⁸ A posterior-transcallosal approach to the ChFis was chosen to reduce the working distance and afford a wider corridor by avoiding cortical bridging veins (Video 1). Complete resection of the AVM was achieved with no additional morbidity. Microsurgery in experienced hands offers the best chance of cure for AVMs.⁹ In this case we demonstrate how to adapt the transcallosal corridor to the choroidal fissures for safe AVM surgery in this complex location.

Microsurgical resection of tonsillar arteriovenous malformation: an Operative video

Cerebellar arteriovenous malformation (AVM) comprises 10%-15% of intracranial AVMs.¹ Rupture often leads to devastating brainstem compression, with mortality reported as high as 67%.² AVM can be a challenging disease, especially when large in size.³ AVMs can be treated by 1 or a combination of treatment modalities, namely embolization, radiosurgery, or microsurgical resection.^4,5 Arterial adhesions to tonsilobulbar and telovelonsilar segments of posterior inferior cerebellar artery (PICA) can be a challenge, increasing bleeding and ischemic risk.⁶ We present a 2-dimensional video case of a tonsillar AVM. The patient, a previously healthy female in her 20s, presented with a chronic headache. She had no medical history. Initial magnetic resonance imaging revealed a tonsillar AVM classified as Spetzler-Martin grade II. It received its supply from the tonsilobulbar and telovelotonsilar segments of the PICA and drained directly into the precentral vein, transverse sinus, and sigmoid sinus. An angiogram revealed severe venous engorgement-the source of the patient's headache. The AVM was partially embolized 1 month preoperatively. A medial suboccipital telovelar approach was chosen to reduce the working distance and afford a wider corridor to expose the suboccipital surface of the cerebellum.^7,8 Complete resection of the AVM was achieved with no additional morbidity. Microsurgery in experienced hands offers the best chance of cure for AVMs. In Video 1, we demonstrate the relationships among the tonsila, biventral lobule, vallecula cerebelli, PICA, and cerebellomedullary fissure as an important anatomic landmark in a safe total resection of a tonsillar AVM.

Importance of Arachnoid Dissection in Arteriovenous Malformation Microsurgery: A Technical Note

Intracranial arteriovenous malformations (AVMs) are congenital anomalies where arteries and veins connect without a capillary bed. AVMs are the leading cause of nontraumatic intracerebral hemorrhages in people younger than 35 years old.¹ The leptomeninges (arachnoid and pia) form from the meninx primitiva.^2,3 Endothelial channels produce a vascular plexus in the meninx connected by primitive arachnoid. Remodeling of the plexus in response to changing metabolic demands results in a recognizable pattern of arteries and veins.^2,3 Defects at the level of capillaries during arteriovenous specification are most likely responsible for arteriovenous fistula formation.^4-6 Interplay between the congenital dysfunction and flow-related maturation in adulthood, when vasculogenesis has stopped, produces the AVM.^6,7 The relationship between the primitive arachnoid and aberrant AVM vessels is preserved and forms the basis of microsurgical disconnection discussed in Video 1. Several authors have described dissecting these natural planes to delineate the abnormal AVM vessels, relax the brain, and avoid morbidity during AVM surgery.^8-10 We recommend sharp arachnoid dissection with a scalpel or microscissors, occasionally helped by blunt dissection with patties or bipolar forceps. We present a 2-dimensional video of the microsurgical resection of a right parietal AVM. The patient, a healthy 30-year-old female, presented with intermittent headaches and mild impairment of arithmetic and visuospatial ability. Magnetic resonance imaging and digital subtraction angiography showed a compact 3.5-cm supramarginal gyrus AVM supplied by the middle cerebral artery, with superficial drainage. Complete microsurgical resection was performed without morbidity. We demonstrate the principles of arachnoid dissection requisite to disentanglement of the nidus and safe resection of the AVM.

The art of combining neuroanatomy and microsurgical skills in modern neurosurgery

Neurosurgical training outside the operating room has become a priority for all neurosurgeons around the world. The exponential increase in the number of publications on training in neurosurgery reflects changes in the environment that future neurosurgeons are expected to work in. In modern practice, patients and medicolegal experts demand objective measures of competence and proficiency in the growing list of techniques available to treat complex neurosurgical conditions. It is important to ensure the myriad of training models available lead to tangible improvements in the operating room. While neuroanatomy textbooks and atlases are continually revised to teach the aspiring surgeon anatomy with a three-dimensional perspective, developing technical skills are integral to the pursuit of excellence in neurosurgery. Parapharsing William Osler, one of the fathers of neurosurgical training, without anatomical knowledge we are lost, but without the experience and skills from practice our journey is yet to begin. It is important to constantly aspire beyond competence to mastery, as we aim to deliver good outcomes for patients in an era of declining case volumes. In this article, we discuss, based on the literature, the most commonly used training models and how they are integrated into the treatment of some surgical brain conditions.

Transanterior Limiting Sulcus of the Insula Approach: Novel Surgical Approach to the Ventral Striatum Region

BACKGROUND

Lesions in the ventral striatum region (above the anterior perforated substance) are a challenge for neurosurgeons due to their direct relationship with the lenticulostriate arteries, which difficult the surgical access. The standard approaches for this region include the following: 1) transfrontal approach, 2) transanterior perforating substance approach, 3) transcallosal transventricular approach, and 4) pterional transsylvian-transinsular route. In this study, we aimed to describe a novel anatomical approach through the anterior limiting sulcus of the insula in order to access the ventral striatum.

METHODS

We reviewed the literature and performed a detailed dissection of this region by using Klingler's technique with brain specimens injected with silicone, paying special attention to the white fibers and lenticulostriate arteries, and provided a description of an illustrative case of a cavernous malformation.

RESULTS

Neuroanatomical dissections showed that the lenticulostriate arteries had an inverted C-shaped anterior concavity, leaving less significant vascular relationships in the depth of the anterior limiting sulcus of the insula. In the case we described, the cavernous malformation was completely resected and the patient was discharged without any neurological deficits.

CONCLUSIONS

The transanterior limiting sulcus of the insula approach to the ventral striatum offers a safe access route for selected cases and can be performed on the basis of anatomical references. Three-dimensional understanding of the intrinsic brain architecture and its relationships with vascular structures in this specific area is important and can be acquired mainly through laboratory training.

Microsurgical Anatomy of the Cerebellar Interpeduncular Entry Zones

OBJECTIVE

The cerebellar interpeduncular region, particularly the middle cerebellar peduncle (MCP) and interpeduncular sulcus (IPS) are significant surgical relevance areas due to the high prevalence of vascular and tumoral pathologies, such as cavernomas, arteriovenous malformations, and gliomas. We defined safer access areas of the MCP and the IPS, according to the surface anatomy, involved vessels, and fiber tracts of the cerebellar interpeduncular region.

METHODS

Fifteen formalin-fixed and silicone-injected cadaveric heads and 23 human brainstems with attached cerebellums prepared with the Klingler's technique were bilaterally dissected to study the vascular and intrinsic anatomy.

RESULTS

Surface anatomy: The mean length of the IPS was 12.73 mm (standard deviation [SD],2.15 mm), and the average measured angle formed by the IPS and the lateral mesencephalic sulcus was 144.53°. The mean distance from the uppermost point of the IPS to cranial nerve IV was 2.63 mm (SD, 2.84 mm). Vascular anatomy: The perforating branches of the superior cerebellar peduncle, IPS, and MCP originated predominantly from the caudal trunk of the superior cerebellar artery. The inferior third of the superior cerebellar peduncle and IPS was the third most pierced by perforating arteries, and for the MCP, was its superior third. Crossing vessels: The branches of the pontotrigeminal vein and the caudal trunk of the superior cerebellar artery crossed the IPS mostly. The superior third of the IPS was the most crossed by arteries and veins.

CONCLUSIONS

The middle thirds of the IPS and MCP as entry zones might be safer than their superior and inferior thirds due to fewer perforating branches, arterial trunks, and veins crossing the sulcus as fewer eloquent tracts.

Cerebral arteriovenous malformation and foreign accent syndrome: a case report

OBJECTIVE

This case study aims to present the Foreign Accent Syndrome (FAS) in a patient with Cerebral Arteriovenous Malformation (cAVM), considering neuropsychological, radiological and microsurgical aspects.

METHODS

The patient underwent preoperative neuropsychological assessment and MRI and Tractography were performed to identify fibers close to the lesion site. In the surgical procedure, a craniotomy was performed for excision of the cAVM. After surgery and 6 months after the surgical procedure, the patient underwent further and neuropsychological evaluations.

RESULTS

The presence of AVM located in the posterior part of the medial surface of the left superior frontal gyrus was identified and the neuropsychological evaluation found cognitive deficits and symptoms characteristic of FAS, which disappeared after resection.

CONCLUSION

This report presented a case of cAVM in which symptoms were found even without rupture, which was no longer observed after the surgical procedure, demonstrating the relationship of cAVM with the symptoms and neuroanatomical bases of FAS.

Awake Microsurgical Resection for a Precentral Gyrus Arteriovenous Malformation-Three-Dimensional Video and Anatomic Landmarks

Arteriovenous malformations (AVMs) are complex, heterogeneous, and uncommon neurovascular disorders that frequently manifest in young adults. Parenchymal AVMs are thought to be congenital, but this has been recently questioned in the literature.^1,2 AVMs can change over time and cause focal neurological signs or neurocognitive deficits.³ The clinical presentation of an AVM is variable and depends mainly on the occurrence of bleeding as well as its location, size, and ability to take flow from adjacent areas.⁴ AVMs can be treated by a single modality or a combination of different modalities. According to the Expert Consensus on the Management of Brain Arteriovenous Malformations, neurosurgery may be the best option for Spetzler-Martin grade 2 AVMs.⁵ However, the treatment of these lesions when located in eloquent areas, especially in the central lobe, is controversial. Awake craniotomy allows identification of eloquent gyrus and can potentially facilitate resection with functional preservation. An alternative is stereotactic radiosurgery, but a qualitative comparative analysis revealed higher obliteration rate with awake AVM excision compared with stereotactic radiosurgery.⁶ Awake craniotomy was the earliest surgical procedure known, and it has become fashionable again. It was used in the past for surgical management of intractable epilepsy, but its indications are increasing, and it is a widely recognized technique for resection of mass lesions involving the eloquent cortex and for deep brain stimulation.⁷ Its application for resection of vascular lesions, including AVMs, is still limited. In the Video, we present a case of a cerebral AVM of the precentral gyrus in which we achieved complete resection with awake microsurgical treatment without any neurological sequelae for the patient.

Microsurgery for a medial left giant lesser sphenoid wing meningioma complicated by postoperative vasospasm of the ipsilateral supraclinoid carotid artery

Background:

Sphenoid wing meningiomas present close contact with intracranial arteries and have great potential for vascular complications. Here, we describe the case of a patient who presented a medial left giant lesser sphenoid wing meningioma involving the supraclinoid carotid artery. One week after surgery, she developed vasospasm whose treatment using milrinone achieved excellent results.

Case Description:

This is the case of a 23-year-old female with a large meningioma of the middle third of the lesser wing of the left sphenoid. Furthermore, the patient had symptoms of headache, diplopia, and left amaurosis (Video 1). The lesion involved the supraclinoid left carotid artery, causing significant stenosis of the vessel. The patient underwent surgical treatment without complications. One week after the procedure, she evolved with lowered level of consciousness, complete, and proportionate right hemiparesis and right Babinski’s sign. Angiographic study demonstrated significant stenosis of the left supraclinoid artery. After endovascular treatment with milrinone, the patient evolved with immediate improvement of signs and symptoms.

Conclusion:

Giant meningiomas with vascular involvement involve a higher risk of postoperative vascular complications. Other studies should be carried out to predict these complications and thus develop preventive measures.

Building a microneurosurgical laboratory in Latin America: challenges and possibilities

Background

Training in microsurgical neuroanatomy is a priority for neurosurgical education. During the 20^th century, microsurgical laboratories arose and provided a way to develop surgical skills. Few reports addressed the assembly, construction, and details of a training laboratory.

Methods

We have conducted a literature review and searched legislation on the need to plan the structure of the laboratory.

Results

We projected and built a laboratory through a public-private partnership. High-tech workstations and instruments were planned to meet the needs of residents, fellows, and student. All steps and materials were in accordance with the Brazilian legislation and articles previously selected.

Conclusion

We described our experience and demonstrated the implementation of a micro neurosurgical skills laboratory.

Microsurgical Treatment for a Ruptured Posterior Inferior Cerebellar Artery Aneurysm: A 3-Dimensional Surgical Video and Anatomic Landmarks Review

Aneurysms are the most frequent issue for the posterior inferior cerebellar artery (PICA). PICA aneurysms account for 1.4% to 4.5% of all intracranial aneurysms.^1-3 Although the majority of PICA aneurysms arise from their junction with the vertebral artery, they can be found in any of 5 segments.^4,5 Although PICA is more prone to form nonsaccular aneurysms than other intracranial arteries, ruptured aneurysms are usually saccular.⁶ Nearly all PICA aneurysms are located intracranially, above the foramen magnum. Extracranial PICA aneurysms are rare, with few reports in literature.⁷ Microsurgical clipping remains a good treatment alternative for these aneurysms. Higher risk of rerupture has even been reported with embolization of the distal PICA aneurysm with parent artery preservation.⁸ Here we present the case of a 64-year-old male patient who presented right after a thunderclap headache, followed by a temporary loss of consciousness and disorientation. He was diagnosed with a modified Fisher 4 and Hunt and Hess 2 subarachnoid hemorrhage and found to have a partially thrombosed left PICA saccular aneurysm of the caudal loop just below the foramen magnum. The lesion was approached via a midline suboccipital craniotomy with C1 laminectomy. Microsurgical clipping of the aneurysm was performed without any complications (Video 1). Postoperatively, the patient was discharged without neurologic deficits. We present the first surgical video of the necessary steps in order to perform a microsurgical clipping of an extracranially located caudal loop PICA aneurysm through a midline suboccipital craniotomy with C1 laminectomy.

Three-Dimensional Quantitative Analysis of the Brainstem Safe Entry Zones Based on Internal Structures

OBJECTIVE

Brainstem safe entry zones (EZs) are gates to access the intrinsic pathology of the brainstem. We performed a quantitative analysis of the intrinsic surgical corridor limits of the most commonly used EZs and illustrated these through an inside perspective using 2-dimensional photographs, 3-dimensional photographs, and interactive 3-dimensional model reconstructions.

METHODS

A total of 26 human brainstems (52 sides) with the cerebellum attached were prepared using the Klingler method and dissected. The safe working areas and distances for each EZ were defined according to the eloquent fiber tracts and nuclei.

RESULTS

The largest safe distance corresponded to the depth for the lateral mesencephalic sulcus (4.8 mm), supratrigeminal (10 mm), epitrigeminal (13.2 mm), peritrigeminal (13.3 mm), lateral transpeduncular (22.3 mm), and infracollicular (4.6 mm); the rostrocaudal axis for the perioculomotor (11.7 mm), suprafacial (12.6 mm), and transolivary (12.8 mm); and the mediolateral axis for the supracollicular (9.1 mm) and infracollicular (7 mm) EZs. The safe working areas were 46.7 mm² for the perioculomotor, 21.3 mm² for the supracollicular, 14.8 mm² for the infracollicular, 33.1 mm² for the supratrigeminal, 34.3 mm² for the suprafacial, 21.9 mm² for the infrafacial, and 51.7 mm² for the transolivary EZs.

CONCLUSIONS

The largest safe distance in most EZs corresponded to the depth, followed by the rostrocaudal axis and, finally, the mediolateral axis. The transolivary had the largest safe working area of all EZs. The supracollicular EZ had the largest safe area to access the midbrain tectum and the suprafacial EZ for the floor of the fourth ventricle.

Microsurgical approaches to the cerebellar interpeduncular region: qualitative and quantitative analysis

OBJECTIVE

The cerebellar interpeduncular region (CIPR) is a gate for dorsolateral pontine and cerebellar lesions accessed through the supracerebellar infratentorial approach (SCITa), the occipital transtentorial approach (OTa), or the subtemporal transtentorial approach (STa). The authors sought to compare the exposures of the CIPR region that each of these approaches provided.

METHODS

Three approaches were performed bilaterally in eight silicone-injected cadaveric heads. The working area, area of exposure, depth of the surgical corridor, length of the interpeduncular sulcus (IPS) exposed, and bridging veins were statistically studied and compared based on each approach.

RESULTS

The OTa provided the largest working area (1421 mm2; p < 0.0001) and the longest surgical corridor (6.75 cm; p = 0.0006). Compared with the SCITa, the STa provided a larger exposure area (249.3 mm2; p = 0.0148) and exposed more of the length of the IPS (1.15 cm; p = 0.0484). The most bridging veins were encountered with the SCITa; however, no significant differences were found between this approach and the other approaches (p > 0.05).

CONCLUSIONS

To reach the CIPR, the STa provided a more extensive exposure area and more linear exposure than did the SCITa. The OTa offered a larger working area than the SCIT and the STa; however, the OTa had the most extensive surgical corridor. These data may help neurosurgeons select the most appropriate approach for lesions of the CIPR.

Awake Microsurgical Resection for Optochiasmatic Cavernous Malformation

Cavernous malformations (CM) affect approximately 0.5% of the population, with only a limited portion being located in the optic nerve and chiasma. The clinical presentation is determined by their locations. In the optochiasmatic CM, the acute visual disturbance is the most common presentation. Chronically, many show a progressive visual loss, chronic headache, and pituitary disturbances. The differential diagnosis includes optic glioma, arteriovenous malformations, aneurysm, craniopharyngioma, pituitary apoplexy, and inflammatory conditions. In Video 1, we present the case of a 39-year-old woman with a history of a hemorrhagic optochiasmatic cavernoma in 2016, who started using propranolol to reduce the lesion and symptoms of visual loss. Moreover, the first microsurgical resection of the cavernoma and evacuation of the hematoma were performed in the same year. Owing to evolvement from a partial to a total vision loss in the left eye and presentation of new symptoms in the right eye, the patient underwent microsurgical resection. The surgery was performed sequentially. An awake craniotomy was performed to monitor the chiasma and right optic nerve. The postoperative magnetic resonance imaging showed complete resection of the CM, and the patient fully recovered. The patient signed the institutional consent form, stating that he or she accepts the procedure and allows the use of his or her images and videos for any type of medical publications in conferences and/or scientific articles.

Microsurgical Treatment for Posthemorrhagic Cavernoma of Frontal Lobe Coexisting with Unruptured Ipsilateral Middle Cerebral Artery Aneurysm

Cerebral cavernous malformations, also known as cavernomas, are vascular abnormalities of the brain that are clinically associated with a variety of neurologic symptoms that may include hemorrhagic strokes. They are the most common vascular abnormality, representing 10%-25% of all vascular malformations.¹ Lesions associated with cavernomas include developmental venous anomalies, capillary telangiectasias, and other vascular malformations² but not intracranial aneurysms. The latter association is extremely rare; in fact, there is only 1 case reported in the literature, in which the cavernoma was obscured by the presence of a cerebral hemorrhage and an unruptured aneurysm, which was presumed to be the primary cause of the bleeding, thereby misleading the surgeons to treat only the aneurysm.² There are different alternatives for the management of different types of lesions.^3-5 In this 3-dimensional operative video (Video 1), we present a case of a cavernoma associated with hemorrhage coexisting with an unruptured aneurysm in which we achieved complete resolution of both with microsurgical treatment through a pterional approach.⁶ The patient consented to publication of images.

Microsurgical treatment for cerebellomesencephalic fissure arteriovenous malformations after multiple sessions of endovascular treatment

Background:

Arteriovenous malformations (AVMs) are relatively uncommon congenital vascular anomalies, and only 7–15% of AVMs occur in the posterior fossa. Most posterior fossa AVMs clinically present with hemorrhage and are associated with a high risk of neurological deficits and mortality. These malformations are associated with a high incidence of flow-related aneurysms. Endovascular treatment of infratentorial AVMs is challenging in pediatric patients.

Case Description:

We describe an 11-year-old female adolescent with cerebellar syndrome [Video 1], who was diagnosed with a cerebellomesencephalic fissure AVM. We observed a sequential increase in the size of the AVM after multiple sessions of endovascular treatment and performed successful microsurgical resection of the lesion.

Conclusion:

This illustrative video highlights the role of microsurgery as a feasible therapeutic strategy for complete resection of cerebellar AVMs after endovascular embolization.

Combined treatment for a hemispheric cerebellar AVM

Posterior fossa arteriovenous malformations (AVMs) can be a challenging disease, especially those large in size. AVMs can be treated with a combination of endovascular treatment and microsurgery. Here, the authors present the case of a 16-year-old female patient with progressive dizziness and episodic syncope. The workup of the patient showed a hemispheric cerebellar AVM, Spetzler-Martin grade IV. She underwent combined treatment (endovascular and microsurgery) with no complications and cure of the malformation.

The video can be found here: https://youtu.be/rNw_Kyd76Mg

Endoscopic brainwash after clipping a ruptured aneurysm of the communicating segment of the intracranial carotid artery

Background:

Intracranial aneurysms are common vascular malformation occurring in 1-2% of the population and accounting for 80–85% of nontraumatic subarachnoid hemorrhages. About 10% of the ruptured aneurysm causing subarachnoid hemorrhage (SHA) develop intraventricular hemorrhage (IVH). In this scenario, the external ventricular drain (EVD) is a usual treatment for IVH. To reduce the time for the clot absorption, the neuroendoscopy with clot removal and ventricular irrigation is a feasible option, although not routinely used.

Case Description:

This 2D video shows a case of a 60-year-old female, with sudden headache associated with nausea and vomit. The brain angiotomography revealed aneurysm in the communicating segment of the left internal carotid artery, with 10.5 mm of diameter; also showed intraparenchymal, subarachnoid, and IVH, with a Fisher Modified Grade of 4 and a prompt aneurysm clipping and EVD were performed. Two days after the first surgical procedure, a neuroendoscopy was performed to remove the ventricular clots and improve the patient outcomes.

Conclusion:

In the presented case, at the 6^th postoperative month, the patient was Grade 1 in the Rankin Modified Scale and without hydrocephalus. This procedure can be used routinely as an additional tool to microsurgical clipping to improve patients outcome.