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Background: Distal anterior cerebral artery (DACA) aneurysms, also known as pericallosal artery aneurysms, are present in 1.5%-9% of all intracranial aneurysms. Here we characterize the important microsurgical anatomy of DACAs; describe the surgical approach to treating these aneurysms with a minimally invasive surgical technique, the mini anterior interhemispheric approach (MAIA); and examine the nuances of aneurysm clipping in this region., Methods: This was a retrospective and descriptive analysis of a series of aneurysm surgeries performed at the National Institute of Neurology and Neurosurgery in Mexico City. Cadaveric dissections were used to demonstrate relevant cerebrovascular anatomy. We analyzed patient demographic data and aneurysm characteristics. Patients' neurologic grade was evaluated using the Hunt and Kosnik (H-K) scale, and surgical outcomes were evaluated using the Glasgow Outcome Scale (GOS). Other variables were analyzed using the χ 2 test., Results: We analyzed a total of 32 DACA aneurysms (10 nonruptured and 22 ruptured), representing 5.8% of all aneurysms. The study cohort was 64.3% females and 35.7% males. H-K grade II was the most frequent classification (32.4%); 42.8% of patients presented with a Fisher grade IV aneurysm. Aneurysm location was classified as supra-genu, genu, or infra-genu. Eight patients had multiple aneurysms, among which 50% were located at the bifurcation of the middle cerebral artery., Conclusions: Surgical clipping through a MAIA approach is an excellent treatment option for pericallosal artery aneurysms., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Foramen magnum meningiomas represent a challenge for neurosurgeons. These tumors require careful surgical manipulation as they are often located in proximity to critical neurovascular structures and the cranial nerves. The far lateral approach is considered the safest neurosurgical approach for excising foramen magnum lesions. It facilitates the access to the anterior foramen magnum and reduces the retraction of vital structures. We describe key historical, epidemiological, genetic, epigenetic, clinical, and neurosurgical aspects of foramen magnum meningiomas. We emphasize the far lateral approach for lesions arising in the foramen magnum, as well as the most appropriate patient positioning for such approach. Caring for these aspects will be rewarded with the best perioperative neurosurgical outcomes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: An extensive frontal resection is a frequently performed neurosurgical procedure, especially for treating brain tumor and refractory epilepsy. However, there is a paucity of reports available regarding its surgical anatomy and technique., Objectives: We sought to present the anatomic landmarks and surgical technique of the frontal lobe decortication (FLD) in epilepsy. The goals were to maximize the gray matter removal, spare primary and supplementary motor areas, and preserve the frontal horn., Material and Methods: The anatomic study was based on dissections performed in 15 formalin-fixed adult cadaveric heads. The clinical experience with 15 patients is summarized., Result: FLD consists of 5 steps: 1) coagulation and section of arterial branches of lateral surface; 2) paramedian subpial resection 3 cm ahead of the precentral sulcus to reach the genu of corpus callosum; 3) resection of gray matter of lateral surface, preserving the frontal horn; 4) removal of gray matter of basal surface preserving olfactory tract; 5) removal of gray matter of the medial surface under the rostrum of corpus callosum. The frontal horn was preserved in all 15 patients; 12 patients (80%) had no complications; 2 patients presented temporary hemiparesis; and 1 Rasmussen syndrome patient developed postoperative fever. The best seizure control was in cases with focal magnetic resonance imaging abnormalities limited to the frontal lobe., Conclusion: FLD is an anatomy-based surgical technique for extensive frontal lobe resection. It presents reliable anatomic landmarks, selective gray matter removal, preservation of frontal horn, and low complication rate in our series. It can be an alternative option to the classical frontal lobectomy., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: Fiber dissection studies of the cerebrum have focused on the lateral surface. No comparable detailed studies have been done on the medial and inferior surfaces. The object of this study was to examine the fiber tracts, cortical, and subcortical structures of the medial and inferior aspects of the brain important in planning operative approaches along the interhemispheric fissure, parafalcine area, and basal surfaces of the cerebrum., Methods: Twenty formalin-fixed human hemispheres (10 brains) were examined by fiber dissection technique under ×6-×40 magnifications., Results: The superior longitudinal fasciculus I, cingulum, inferior longitudinal fasciculus, uncinate fasciculus, optic radiations, tapetum, and callosal fibers were dissected step by step from medial to lateral, exposing the nucleus accumbens, subthalamic nucleus, red nucleus, and central midline structures (fornix, stria medullaris, and stria terminalis). Finally, the central core structures were dissected from medial to lateral., Conclusions: Understanding the fiber network underlying the medial and inferior aspects of the brain is important in surgical planning for approaches along the interhemispheric fissure, parafalcine area, and basal surfaces of the cerebrum., (Copyright © 2016. Published by Elsevier Inc.)

Objective: We used microscopy to conduct qualitative and quantitative analysis of 4 surgical approaches commonly used in the surgery of the ambient cistern: infratentorial supracerebellar (SC), occipital interhemispheric, subtemporal (ST), and transchoroidal (TC). In addition, we performed a parahippocampal gyrus resection in the ST context., Methods: Each approach was performed in 3 cadaveric heads (6 sides). After the microscopic anatomic dissection, the parahippocampal gyrus was resected through an ST approach. The qualitative analysis was based on anatomic observation and the quantitative analysis was based on the linear exposure of vascular structures and the area of exposure of the ambient cistern region., Results: The ST approach provided good exposure of the inferior portion of the cistern and of the proximal segments of the posterior cerebral artery. After the resection of the parahippocampal gyrus, the area of exposure improved in all components, especially the superior area. A TC approach provided the best exposure of the superior area compared with the other approaches. The posterolateral approaches (SC/occipital interhemispheric) to the ambient cistern region provided similar exposure of anatomic structures. There was a significant difference (P < 0.05) in linear exposure of the posterior cerebral artery when comparing the ST/TC and ST/SC approaches., Conclusions: This study has demonstrated that surgical approaches expose dissimilarly the different regions of the ambient cistern and an approach should be selected based on the specific need of anatomic exposure., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: We used microscopy with endoscopic assistance to conduct an objective analysis of 4 surgical approaches commonly used in the surgery of the ambient cistern: infratentorial supracerebellar (SC), occipital interhemispheric (OI), subtemporal (ST), and transchoroideal (TC). In addition, we performed a parahippocampalis gyrus resection in the ST context., Methods: Each approach (SC, OI, ST, TC) was performed on 3 cadaveric heads (6 sides). After the microscopic anatomic dissection, the 30-degree endoscope was used to explore the exposure. The parahippocampalis gyrus was resected through an ST approach and the exposure was evaluated. The quantitative analysis was based on linear exposure of the vascular structures (linear exposure), such as the posterior choroidal artery (PChA), the P2 and P3 segments of the posterior cerebral artery (PCA) with their branches, the basal vein of Rosenthal, and the area of exposure of the ambient cistern region (area of exposure) limited by points on its superior, mesial, and anterior walls. In all cases, a P value of less than 0.05 was considered significant., Results: There was a significant difference (P < 0.05) in linear exposure of the PCA and medial PChA between microsurgery and endoscopic assistance using the ST approach. This approach also improved the medial, superior, and total exposure of the ambient cistern region., Conclusions: This study demonstrates that endoscope assistance improved exposure of the ambient cistern region when using the ST approach. Endoscopic assistance provided similar surgical exposure compared with ST associated with parahippocampalis resection., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: To examine the efficacy of the endoscope as an adjunct to the operating microscope in defining the surgical anatomy of the cerebellopontine angle (CPA)., Methods: The surgical anatomy of the CPA was examined in cadaveric CPAs through a retrosigmoid approach. The upper, middle, and lower neurovascular complexes and the individual segments of the cerebellar arteries in the CPA were examined with the surgical microscope and 0° and 45° rigid endoscopes., Results: The microscope provided satisfactory views of the posterior surface of the neural and vascular structures in the central part of the CPA cistern. The endoscope provided superior views of the nerves' junction with the brainstem, their dural exit, and their vascular relationships. The endoscope also provided superior views of the individual segments of the cerebellar arteries., Conclusion: The combination of endoscopic and microsurgical techniques aids in achieving optimal exposure in CPA surgery., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objectives: Deep brain stimulation (DBS) has been established as a safe, effective therapy for movement disorders (Parkinson's disease, essential tremor, etc.), and its application is expanding to the treatment of other intractable neuropsychiatric disorders including depression and obsessive-compulsive disorder (OCD). Several published studies have supported the efficacy of DBS for severely debilitating OCD. However, questions remain regarding the optimal anatomic target and the lack of a bedside programming paradigm for OCD DBS. Management of OCD DBS can be highly variable and is typically guided by each center's individual expertise. In this paper, we review the various approaches to targeting and programming for OCD DBS. We also review the clinical experience for each proposed target and discuss the relevant neuroanatomy., Materials and Methods: A PubMed review was performed searching for literature on OCD DBS and included all articles published before March 2012. We included all available studies with a clear description of the anatomic targets, programming details, and the outcomes., Results: Six different DBS approaches were identified. High-frequency stimulation with high voltage was applied in most cases, and predictive factors for favorable outcomes were discussed in the literature., Conclusion: DBS remains an experimental treatment for medication refractory OCD. Target selection and programming paradigms are not yet standardized, though an improved understanding of the relationship between the DBS lead and the surrounding neuroanatomic structures will aid in the selection of targets and the approach to programming. We propose to form a registry to track OCD DBS cases for future clinical study design., (© 2013 International Neuromodulation Society.)

Objective: The study compared the endoscopic anatomy of the transnasal and transoral approaches to the craniovertebral junction (CVJ)., Methods: Structures examined and compared with both the straight and angled telescopes in 10 cadaveric specimens included the pharyngeal walls and adjacent musculature, resected anterior arch of the axis and odontoid, cruciform, axial, and apical ligaments, clival and dural openings, and the intradural exposure., Results: There is considerable overlap at the pharyngeal level in the structures that can be viewed by the transoral and transnasal routes. The transoral approach provides a wider corridor with less restricted manipulation of instruments than the transnasal approach, but the transnasal approach provides a better view of the clivus, upper part of the CVJ, and the structures posterior to the removed odontoid and anterior arch of C1. Combining the two approaches provides significantly better access to the midline anterior CVJ than either approach alone, allows the scopes to be advanced in one cavity and the surgical instruments in the other cavity, and reduces the need to split the palate, tongue, or mandible in order to reach the target area. The transnasal approach also allows access to the superior part of the occipital condyles, paraclival areas, and hypoglossal canals without removal of the condyles, but these structures can be exposed by the transoral route only after at least partial removal of the condyles., Conclusion: The endoscopic transoral and transnasal approaches to the CVJ should be viewed as complementary routes as opposed to strict alternatives., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The use of lateral mass atlas screws is an important technique to achieve fusion and stability at the craniocervical region affected by different pathologies (degenerative, traumatic, inflammatory, neoplastic, or congenital). This paper describes the anatomy and techniques necessary for proper insertion of posterior C1 lateral mass screws, using anatomic dissection and intraoperative pictures. Knowledge of the anatomy and the surgical technique of insertion of C1 lateral mass screws are of paramount importance to have good surgical results., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Background: The lateral approach to the craniocervical junction is directed along the atlantal and occipital condyles to the dens. The advantages of the lateral approach compared with the anterior transoral and transnasal approaches are that it provides a sterile field, and anterior decompression and postdecompression fixation can be performed in one procedure., Objective: To examine the usefulness of endoscopy as an auxiliary tool during lateral transatlantal odontoidectomy., Methods: Six cadaver heads, in which the vessels were injected with colored silicone, were dissected using a surgical microscope and 0- and 30-degree endoscopes. A flap incision was chosen to accomplish exposure of the area of the decompression, the occipital squama and adjacent laminae for fixation, and the vertebral artery from C2 to its dural entrance for its stabilization., Results: Study findings revealed that endoscopy adds several advantages to microscopy in the lateral transatlantal approach to the craniovertebral junction in cases of craniovertebral malformation by providing magnification and illumination not limited by corners, thus helping to avert substandard decompression and complications such as dural tears and cerebrospinal fluid leaks; flexibility in surgical positioning of patients; and improved ergonomics that enable the surgeon to complete the procedure in a more efficient, comfortable, and safe manner., Conclusion: Endoscopy is a useful adjunct to microscopy in completing lateral approaches to the craniovertebral junction., (Copyright © 2010 Elsevier Inc. All rights reserved.)