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.

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.

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.

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.

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 6th 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.

Atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation: Case report. / Tumor teratoide/rabdoide atípico con diferenciación tipo ganglioglioma: reporte de caso.

BACKGROUND: Atypical teratoide/rhabdoid tumor is a very rare and aggressive disease that primarily presents in pediatric patients. To the best of our knowledge, the initial presentation of this type of tumor with ganglioglioma-like differentiation is rare in the literature. CASE REPORT: We present the case of a 9-month-old patient with left facial paralysis. An MRI revealed a lesion at the left cerebellopontine angle. Complete macroscopic surgical resection was performed. Histopathology and immunohistochemistry testing revealed an atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation. CONCLUSIONS: This case report presents an atypical teratoid/rhabdoid tumor with initial gangligioma-like differentiation. This study adds to the data in the literature and promotes the study of this type of histogenesis. It lays a foundation for encouraging further studies to determine whether changes should be made to existing management protocols and, at the same time, determine whether there would be any variation with regard to disease prognosis.

Interhemispheric transcallosal transforaminal approach for decompression of a giant superior cerebellar artery thrombosed aneurysm: Three-dimensional operative video.

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.

Interpeduncular Sulcus Approach to the Posterolateral Pons.

OBJECTIVE: In this article, we describe a new safe entry point for the posterolateral pons. METHODS: To show the adjacent anatomy and measure the part of the interpeduncular sulcus that can be safely accessed, we first performed a review of the literature regarding the pons anatomy and its surgical approaches. Thereafter, 1 human cadaveric head and 15 (30 sides) human brainstems with attached cerebellums were bilaterally dissected with the fiber microdissection technique. A clinical correlation was made with an illustrative case of a dorsolateral pontine World Health Organization grade I astrocytoma. RESULTS: The safe distance for accessing the interpeduncular sulcus was found to extend from the caudal end of the lateral mesencephalic sulcus to the point at which the intrapontine segment of the trigeminal nerve crosses the interpeduncular sulcus. The mean distance was 8.2 mm (range, 7.15-8.85 mm). Our interpeduncular sulcus safe entry zone can be exposed through a paramedian infratentorial supracerebellar approach. When additional exposure is required, the superior portion of the quadrangular lobule of the cerebellar hemispheric tentorial surface can be removed. In the presented case, surgical resection of the tumor was performed achieving a gross total resection, and the patient was discharged without neurologic deficit. CONCLUSIONS: The interpeduncular sulcus safe entry zone provides an alternative direct route for treating intrinsic pathologic entities situated in the posterolateral tegmen of the pons between the superior and middle cerebellar peduncles. The surgical corridor provided by this entry point avoids most eloquent neural structures, thereby preventing surgical complications.

Microsurgical Resection of a Left Supramarginal Gyrus AVM Causing Radionecrosis.

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.

Gelatin Paste as an Alternative Cost-Effective Hemostatic Agent in Cranial Surgery: Doing More with Less.

OBJECTIVE: To present an alternative cost-effective hemostatic agent (HA) for cranial surgery and to describe the technique to produce it. METHODS: This HA has been used in 3 reference centers over the last year during 230 procedures, including different types of pathology, such as skull base, oncology, vascular, and trauma, either for endoscopic or open approaches. This agent was made from a low-cost and worldwide-available gelatin foam which was mixed with saline solution in 2 syringes and connected by a 3-way stopcock, making a useful hemostatic paste. RESULTS: The cost was 16 and 28 times less than SURGIFLO and FLOSEAL, respectively. The mean time to prepare the mix was 4 minutes. It was very effective for venous and low-flow bleeding. CONCLUSIONS: The presented technique offers a reliable and cost-effective way of achieving hemostasis in cranial surgery, therefore allowing hospitals with limited resources to perform advanced procedures in a safer way.

Ablative stereotactic neurosurgery for irreducible neuroaggressive disorder in pediatric patients. / Neurocirugía estereotáctica ablativa para trastorno neuroagresivo irreductible en pediátricos.

INTRODUCTION AND OBJECTIVES: The irreducible neuroaggressive disorder (IND) is a well-described entity known to be associated with impulsive and aggressive behavior. While various studies have assessed available pharmacological and non-pharmacological treatment regimens, patients with IND continue to pose a major threat to themselves and society. While targeted stereotactic therapy for IND has gained traction in recent years, there is a paucity of information describing comparative effectiveness of different validated anatomic regions. In this paper, we discuss the surgical results for patients with IND following targeted lesional therapy with a special focus on selection criteria and operative methods. The objective is to analyze the efficacy and safety of the different described targets for this disorder in pediatric patients. MATERIALS AND METHODS: Eight pediatric patients met strict criteria for IND and were enrolled in this study. Electroencephalography (EEG), video electroencephalography (VEEG) and magnetic resonance imaging (MRI) were performed in all patients prior to surgery. Irreducible neuroagressive symptom was approached by lesional therapy based on most described targets for this disorder and assessed by The Overt Agressive Scale (OAS) pre-operatively and 6 months following surgery, using Wilcoxon test for statistical analysis. RESULTS AND CONCLUSIONS: The average patient age was 13 years 2 months. 7 of the 8 patients enrolled had intellectual disabilities, 1 patient suffered neurologic sequelae referable to Dandy Walker syndrome and 7 patients had no preoperative anatomical alterations. Following surgery, patients with IND noted improvement in their OAS. On average, the OAS improved by 39.29% (P=.0156), a figure similar in comparison to studies assessing treatment of IND in adult patients. The most satisfactory results were achieved in patients whose ablative therapy involved the Amygdala in their targets. There were no deaths or permanent neurological deficits attributable to procedure. To the author's knowledge, this is the largest series described in the literature for pediatric patients with IND treated with lesional stereotactic therapy.