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.

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.

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.

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.