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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.

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One of the most popular treatment strategies for complex cerebral aneurysms with wide necks is stent-assisted coiling.1 Although it is a minimally invasive technique, it is associated with higher recurrence rates (approximately 20%) compared with surgical clipping.2 Recanalization is more common principally in ruptured aneurysms as well as in giant aneurysms, aneurysms located in the posterior circulation, aneurysms with a relatively wide neck morphology, and aneurysms followed for >1 year.2-6 Tirakotai et al. classified the indications for surgical treatment after coiling into 3 groups: 1) surgery of incompletely coiled aneurysms; 2) surgery for mass effects on neural structures; 3) surgery for vascular complications.7 Recanalization, if significant, often requires retreatment. Retreating with additional coils fails in perhaps 50% of cases.3 On the other hand, surgical clipping is complicated and difficult to perform. Recanalized aneurysms are categorized into 3 types: type I, coils are compressed; type II, coils are migrated; type III, coils are migrated, and multiple coils fill its neck or the parent artery. Direct clipping can be applied to types I and II, whereas trapping, wrapping, or auxiliary revascularization is required in type III.2 Coil extraction should not be attempted regularly because it is associated with high morbidity.8 In this three-dimensional video, we present the microsurgical treatment of a type I recanalized anterior communicating artery aneurysm, which in serial digital subtraction angiography control scans showed residual patency, progressive growth, and changes in its hemodynamic behavior (Video).

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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.

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Cerebral arteriovenous malformations (AVMs) are dynamic neurovascular disorders that occur mainly in young adults, presenting an annual risk of rupture of 2% - 4% per year.1 They can be asymptomatic, representing an incidental radiologic finding, or present with neurologic deficits according to their brain location, size, and presence or absence of bleeding.2,3 AVMs located in eloquent areas4 represent a great challenge for neurosurgeons, sometimes directed to alternatives therapies (e.g., embolization, radiotherapy) due to the difficulty in planning and surgical technique. Despite the complexity, we consider that there is benefit to removing these lesions; this can be done safely, as with the adequate microsurgical strategy and neuroanatomic knowledge. In Video 1, we show the case of a 55-year-old male patient with an AVM positioned over the right central sulcus. He presented with intermittent left-hand paresthesia followed by an episode of involuntary movements in the left arm without loss of consciousness and with spontaneous resolution. Angiography showed an AVM feed by branches of the middle cerebral artery and multiple venous drainage for the Trolard complex and superficial middle cerebral vein, with a 4-cm nidus, making it grade III in the Spetzler-Martin classification.4 The patient underwent surgery with total resection of the lesion without any complication or new neurologic deficits.

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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.

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Arteriovenous malformations (AVMs) are congenital neurovascular disorders frequently manifested in young adults. The clinical presentation is variable and depends on its location, size, and ability to steal flow from adjacent areas, but it depends mainly on the occurrence of bleeding.1 The treatment of these lesions when located in eloquent areas, especially around the central sulcus, is controversial. Surgical resection of an AVM in the central lobe may cause postoperative sensorimotor deficits because this anatomic region includes the precentral and postcentral gyri on the lateral surface and paracentral lobule on the medial surface.2 AVMs can be successfully treated by surgery, but this treatment may pose unacceptable risks to the patient if the AVM involves an eloquent cortex. We consider that surgical removal of many of these lesions is feasible when preoperative planning is performed,3 when it is based on deep anatomic knowledge, and particularly when using a refined microsurgical technique.1 In this 3-dimensional Video 1, we present a case of a cerebral AVM of the central sulcus in which we achieved complete resection with microsurgical treatment without any neurologic sequelae for the patient. The patient consented to publication of images.

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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.

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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.

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OBJECTIVE: Anterior clinoidectomy is an important and essential skill for skull base and cerebrovascular neurosurgeons. We present a 1-piece intradural anterior clinoidectomy, providing a step-by-step description of the technique, independently of anatomic variations. METHODS: Between 2014 and 2020, 128 patients (119 women and 9 men; average age, 54.6 years) underwent intradural anterior clinoidectomy during microsurgical clipping of carotid-ophthalmic aneurysms. RESULTS: The anterior clinoid process continues medially with the planum sphenoidale, over the optic nerve, laterally with the lesser wing of the sphenoid bone, and inferiorly with the optic strut, which is always found anteriorly to the clinoid segment of the internal carotid artery, and separates the optic canal from the superior orbital fissure. The proposed anterior clinoidectomy followed, one after the other, these 3 fixation points for the detachment of the anterior clinoid process. The main indication for intradural anterior clinoidectomy was the management of vascular lesions around paraclinoid (clinoidal and ophthalmic) segments of the internal carotid artery. Complications of the procedure included injury to the internal carotid artery or the ophthalmic artery, thermal damage to the optic nerve, and invasion of the sphenoid sinus or a pneumatized anterior clinoid process, which could lead to postoperative cerebrospinal fluid leakage. CONCLUSIONS: The anterior clinoidectomy technique described here minimizes the drilling surface for detachment of the anterior clinoid process and reduces operative time as well as the amount of bone dust produced by drilling. It also precisely delineates the localization of the optic strut, preventing carotid or optic nerve damage.

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BACKGROUND: Giant brain aneurysms account for approximately 5% of all intracranial aneurysms, often presenting with intraluminal thrombosis that causes a mass effect in surrounding neural structures. Although its exact growing mechanism remains unknown, they have to be treated. Despite the most recent advances in neurosurgical fields, the best treatment modality remains unknown and surgery of giant superior cerebellar artery (SCA) aneurysms still is a challenge even for the most experienced neurosurgeons, due to their deep location, surrounding perforating vessels, and intraluminal thrombosis. CASE DESCRIPTION: In this video, we present the case of a 65-year-old woman with progressive hemiparesis and paresis of low cranial nerves. The symptoms were caused by a giant aneurysm located in the origin of the SCA. Despite endovascular embolization of the aneurysm and placement of a flow diverter stent, the aneurysm increased in size causing symptoms progression. In that scenario, we decided to perform a microsurgical decompression of the aneurysm thrombus and coagulation of the vasa vasorum, to reduce the mass effect and prevent the aneurysm from keep growing. CONCLUSION: Through an extensive description of the surgical anatomy, we illustrate an interhemispheric transcallosal transforaminal approach, with the removal of anterior thalamic tubercle to widely expose the aneurysm dome. The surgery was successfully performed, and the patient symptoms improved. The patient signed the Institutional Consent Form, which allows the use of her images and videos for any type of medical publications in conferences and/or scientific articles.

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Late radiation necrosis is a rare entity presenting in 2.2% to 9% of radiation-treated arteriovenous malformations (AVMs). It occurs by a mean of 3 years following treatment. There are few reports in the literature of radionecrosis and solid lesions treated with surgery.1-4 To the authors' knowledge, this case has the longest interval between radiosurgery and the presentation of cerebral necrosis. In this surgical video, we present the case of a 51-year-old female with a left supramarginal gyrus AVM that received radiosurgery with gamma knife; after 20 years, she began having seizures and aphasia. The magnetic resonance imaging scan revealed a lesion simulating an intra-axial tumor causing important edema and mass effect. Medical treatment was given including high-dose steroids without success, therefore microsurgery was performed. The surgery was presented in a step-by-step basis and correlation was performed with the involved adjacent anatomy, to illustrate the anatomy of the approach and surgical landmarks. The patient's symptoms resolved completely, and the postoperative magnetic resonance imaging scan showed complete resection and resolution of the edema. The histopathological findings were consistent with a radionecrosis and AVM. The patient signed the Institutional Consent Form, which states that she accepts the procedure and allows the use of her images and videos for any type of medical publications in conferences and/or scientific articles.

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