Microsurgical anatomy of the isthmic cingulum: a new white matter crossroad and neurosurgical implications in the posteromedial interhemispheric approaches and the glioma invasion patterns.

ABTRACT: The dichotomy of the cingulum bundle into the dorsal supracallosal and ventral parahippocampal parts is widely accepted; however, the retrosplenial component with its multiple alternative connections has not been revealed. The aim of this study was to delineate the microsurgical anatomy of a connectionally transition zone, the isthmic cingulum, in relation to the posteromedial interhemispheric access to the atrium and discuss the relevant patterns of glioma invasion on the basis of its fiber connections. White matter (WM) fibers were dissected layer by layer in a medial-to-lateral, lateral-to-medial, and posterior-to-anterior fashion. All related tracts and their connections were generated using deterministic tractography. The magnetic resonance imaging (MRI) tractography findings were correlated with those of fiber dissection. A medial parieto-occipital approach to reach the atrium was performed with special emphasis on the cingulate isthmus and underlying WM connections. The isthmic cingulum, introduced as a retrosplenial connectional crossroad for the first time, displayed multiple connections to the splenium and the superior thalamic radiations. Another new finding was the demonstration of lateral hemispheric extension of the isthmic cingulum fibers through the base of the posterior part of the precuneus at the base of the parieto-occipital sulcus. The laterally crossing cingulum fibers were interconnected with three distinct association tracts: the middle longitudinal (MdLF), the inferior frontooccipital fasciculi (IFOF), and the claustro-cortical fibers (CCF). In the process of entry to the atrium during posterior interhemispheric approaches, the splenial and thalamic connections, as well as the laterally crossing fibers of the isthmic cingulum, were all in jeopardy. The connectional anatomy of the retrosplenial area is much more complicated than previously known. The isthmic cingulum connections may explain the concept of interhemispheric and medial to lateral cerebral hemisphere invasion patterns in medial parieto-occipital and posteromesial temporal gliomas. The isthmic cingulum is of key importance in posteromedial interhemispheric approaches to both: the atrium and the posterior mesial temporal lobe.

Microsurgical anatomy of the auditory radiations: revealing the enigmatic acoustic pathway from a surgical viewpoint.

OBJECTIVE: The thalamocortical projections of the auditory system have not been detailed via microanatomical fiber dissections from a surgical viewpoint. The aim of this study was to delineate the course of the auditory radiations (ARs) from the medial geniculate body to their final destination in the auditory cortex. The authors' additional purpose was to display the relevant neural structures in relation to their course en route to Heschl's gyrus. METHODS: White matter fibers were dissected layer by layer in a lateral-to-medial, inferolateral-to-superomedial, and inferior-to-superior fashion. RESULTS: The origin of ARs just distal to the medial geniculate body was revealed following the removal of the parahippocampal gyrus, cingulum bundle, and mesial temporal structures, in addition to the lateral geniculate body. Removing the fimbria, stria terminalis, and the tail of the caudate nucleus along the roof of the temporal horn in an inferior-to-superior direction exposed the lateral compartment of the sublenticular segment of the internal capsule as the predominant obstacle that prevents access to the ARs. The ARs were initially obscured by the inferolaterally located temporopulvinar tract of Arnold, and their initial course passed posterolateral to the temporopontine fascicle of Türck. The ARs subsequently traversed above the temporopulvinar fibers in a perpendicular manner and coursed in between the optic radiations at the sensory intersection region deep to the inferior limiting sulcus of insula. The distal part of the ARs intermingled with the fibers of the anterior commissure and inferior fronto-occipital fasciculus during its ascent toward Heschl's gyrus. The ARs finally projected to a large area over the superior temporal gyrus, extending well beyond the anteroposterior boundaries of the transverse temporal gyri. CONCLUSIONS: The ARs can be appreciated as a distinct fiber bundle ascending between the fibers of the sublenticular segment of the internal capsule and traversing superiorly along the roof of the temporal horn by spanning between the optic radiations. Our novel findings suggest potential disruption of the ARs' integrity during transsylvian and transtemporal approaches along the roof of the temporal horn toward the mesial temporal lobe. The detailed 3D understanding of the ARs' relations and awareness of their course may prove helpful to secure surgical interventions to the region.

Extending the Indications of 5-Aminolevulinic Acid for Fluorescence-Guided Surgery for Different Central Nervous System Tumors: A Series of 255 Cases in Latin America

Introduction Fluorescence guidance with 5-aminolevulinic acid (5-ALA) is a safe and reliable tool in total gross resection of intracranial tumors, especially malignant gliomas and cases of metastasis. In the present retrospective study, we have analyzed 5-ALA-induced fluorescence findings in different central nervous system (CNS) lesions to expand the indications of its use in differential diagnoses. Objectives To describe the indications and results of 5-ALA fluorescence in a series of 255 cases. Methods In 255 consecutive cases, we recorded age, gender, intraoperative 5-ALA fluorescence tumor response, and 5-ALA postresection status, as well the complications related to the method. Postresection was classified as '5-ALA free' or '5-ALA residual'. The diagnosis of histopathological tumor was established according to the current classification of the World Health Organization (WHO). Results There were 195 (76.4%) 5-ALA positive cases, 124 (63.5%) of whom underwent the '5-ALA free' resection. The findings in the positive cases were: 135 gliomas of all grades; 19 meningiomas; 4 hemangioblastomas; 1 solitary fibrous tumor; 27 metastases; 2 diffuse large B cell lymphomas; 2 cases of radionecrosis; 1 inflammatory disease; 2 cases of gliosis; 1 cysticercosis; and 1 immunoglobulin G4-related disease.

Comparison of the Functional State and Motor Skills of Patients after Cerebral Hemisphere, Ventricular System, and Cerebellopontine Angle Tumor Surgery.

Brain tumor location is an important factor determining the functional state after brain tumor surgery. We assessed the functional state and course of rehabilitation of patients undergoing surgery for brain tumors and assessed the location-dependent risk of loss of basic motor skills and the time needed for improvement after surgery. There were 835 patients who underwent operations, and 139 (16.6%) required rehabilitation during the inpatient stay. Karnofsky Performance Scale, Barthel Index, and the modified Rankin scale were used to assess functional status, whereas Gait Index was used to assess gait efficiency. Motor skills, overall length of stay (LOS) in hospital, and LOS after surgery were recorded. Patients were classified into four groups: cerebral hemisphere (CH), ventricular system (VS), and cerebellopontine angle (CPA) tumors; and a control group not requiring rehabilitation. VS tumor patients had the lowest scores in all domains compared with the other groups before surgery (p < 0.001). Their performance further deteriorated after surgery and by the day of discharge. They most often required long-lasting postoperative rehabilitation and had the longest LOS (35 days). Operation was most often required for CH tumors (77.7%), and all metrics and LOS parameters were better in these patients (p < 0.001). Patients with CPA tumors had the best outcomes (p < 0.001). Most patients (83.4%) with brain tumors did not require specialized rehabilitation, and LOS after surgery in the control group was on average 5.1 days after surgery. VS tumor patients represent a rehabilitation challenge. Postoperative rehabilitation planning must take the tumor site and preoperative condition into account.

A Simple Method to Avoid Brain Shift during Neuronavigation: Technical Note

Introduction The precise identification of anatomical structures and lesions in the brain is the main objective of neuronavigation systems. Brain shift, displacement of the brain after opening the cisterns and draining cerebrospinal fluid, is one of the limitations of such systems. Objective To describe a simple method to avoid brain shift in craniotomies for subcortical lesions. Method We used the surgical technique hereby described in five patients with subcortical neoplasms. We performed the neuronavigation-guided craniotomies with the conventional technique. After opening the dura and exposing the cortical surface, we placed two or three arachnoid anchoring sutures to the dura mater, close to the edges of the exposed cortical surface. We placed these anchoring sutures under microscopy, using a 6­0 mononylon wire. With this technique, the cortex surface was kept close to the dura mater, minimizing its displacement during the approach to the subcortical lesion. In these five cases we operated, the cortical surface remained close to the dura, anchored by the arachnoid sutures. All the lesions were located with a good correlation between the handpiece tip inserted in the desired brain area and the display on the navigation system. Conclusion Arachnoid anchoring sutures to the duramater on the edges of the cortex area exposed by craniotomy constitute a simple method to minimize brain displacement (brain-shift) in craniotomies for subcortical injuries, optimizing the use of the neuronavigation system.

Linfoma no Hodgkin tipo MALT cerebral / Cerebral type MALT non Hodgkin lymphoma

Introducción: Los linfomas no Hodgkin tienen su origen generalmente en el sistema linfoide, existe una gran diversidad de ellos, que hace difícil su clasificación y diagnóstico anatomopatológico definitivo. También hay localizaciones extranodales, como en el cerebro, lo que la hace aún más interesante. Objetivo: Presentar un caso con linfoma marginal cerebral, de diagnóstico muy infrecuente. Caso clínico: Paciente femenina de 67 años de edad con antecedentes patológicos personales de hipertensión arterial y epilepsia, que comenzó a sentirse rígida, con movimientos involuntarios generalizados en el cuerpo, hasta perder la conciencia. Al recuperarse se encontraba somnolienta y con cefalea de moderada intensidad. Se diagnostica un linfoma no Hodgkin tipo MALT cerebral; se realiza tratamiento con el que se revierten los síntomas y se controla la enfermedad. Conclusiones: Es necesario un diagnóstico histopatológico oportuno y certero, con la utilización de los estudios inmunohistoquímicos. Esto permite aplicar un tratamiento precoz y el control de la enfermedad(AU)

Introduction: Non-Hodgkin's lymphomas generally have their origin in the lymphoid system, there is a great diversity of them, which makes their classification and definitive pathological diagnosis difficult. There are also extranodal locations, such as in the brain, which makes it even more interesting. Objective: To present a patient with marginal cerebral lymphoma, of a very infrequent diagnosis. Clinical case: A 67-year-old female patient with a personal pathological history of arterial hypertension and epilepsy, who began to feel rigid, with involuntary movements that generalized to the whole body, until she lost consciousness, when she recovered she was drowsy and with headache of moderate intensity. Brain MALT non-Hodgkin lymphoma is diagnosed, treatment is performed to reverse symptoms, and the disease is controlled. Conclusions: A timely and accurate histopathological diagnosis is necessary, with the use of immunohistochemical studies. This allows for early treatment and disease control(AU)

The Interhemispheric Transgenual Approach for Microsurgical Removal of Third Ventricle Colloid Cysts. Technical Note.

BACKGROUND: Colloid cysts of the third ventricle are rare benign lesions, which amount to approximately 1% of all intracranial tumors. Because these lesions grow predominantly in the anterior aspect of the third ventricle, they may cause the occlusion of the foramina of Monro, generating obstructive hydrocephalus. Surgery is mandatory in cases of large cysts and/or in symptomatic patients. Among the different surgical strategies described in colloid cysts surgery, the microsurgical transcallosal approach still constitutes the procedure of choice in many centers. In this study, we describe a modified microsurgical transcallosal approach, the interhemispheric transgenual approach, in a series of 13 consecutive patients operated on for colloid cysts of the third ventricle. METHODS: All the procedures were performed by the senior author (V.E.) at Neuromed Institute of Pozzilli (Is, Italy). The operative procedure is described in its various steps, illustrating the differences and potential advantages compared with the traditional microsurgical transcallosal approach. RESULTS: No surgical complications or new-onset neurologic deficits were observed in the postoperative period. The postoperative magnetic resonance imaging confirmed in all cases complete lesion removal without any sign of parenchymal damage. No lesion recurrence or need for permanent cerebrospinal fluid diversion was detected in the patients of this series during the follow-up period. CONCLUSIONS: In our experience, the interhemispheric transgenual approach has been effective in providing complete colloid cyst removal with minimal risk of vascular and parenchymal damage. Further studies are required to confirm its efficacy in improving the overall outcome of the microsurgical transcallosal approach.

Comparison Between Transcortical and Interhemispheric Approaches to the Atrium of Lateral Ventricle Using Combined White Matter Fiber Dissections and Magnetic Resonance Tractography.

OBJECTIVE: The objective of this study was to compare transcortical and posterior interhemispheric approaches to the atrium using a combined approach of white matter fiber dissections and magnetic resonance (MR) tractography. METHODS: Ten cerebral hemispheres were examined and dissected from the lateral-to-medial surface and from the medial-to-lateral surface, with special attention to the white matter tracts related to the atrium. MR tractography was used to show the relationship of three-dimensional white matter fibers with the atrium of the lateral ventricle and to compare with cadaveric dissection results. RESULTS: The atrium was related laterally to the superior longitudinal fasciculus II and III, middle longitudinal fasciculus, arcuate fasciculus, vertical occipital fasciculus, and sagittal stratum. Medially, it is related to the superior longitudinal fasciculus I, cingulum, sledge runner, and forceps major. CONCLUSIONS: A combined approach of cadaveric white matter fiber dissections and MR tractography were used to describe the main white matter tracts related to the posterior interhemispheric approach and the transcortical approach, providing an in-depth understanding of the three-dimensional anatomy of white matter fibers and the atrium. In the present study, among approaches examined, the posterior interhemispheric parasplenial transprecuneus approach placed fewer eloquent tracts at risk; however, traversing the sledge runner and the forceps major is unavoidable by this approach.

History and Evolution of Epilepsy Surgery

The surgical treatment for epilepsy has a worldwide historical relevance for centuries. There are archaeological reports that date it back to ancient Egypt; however, the year 1886 is considered a landmark in the surgical treatment for epilepsy in theModern Age, when the first surgery for the treatment of focal epileptic events was performed successfully. Since then, innumerable related articles have been published evoluonarily. Over the last centuries, new techniques and technologies provided better understanding, diagnosis and management for this disease. Thus, historical and evolutionary knowledge becomes important to let us better understand the current position of the surgery for epilepsy treatment and control.

Endoscopic Interhemispheric Disconnection for Intractable Multifocal Epilepsy: Surgical Technique and Functional Neuroanatomy.

BACKGROUND: Callosotomy represents a palliative procedure for intractable multifocal epilepsy. The extent of callosotomy and the benefits of adding anterior and posterior commissurotomy are debated. OBJECTIVE: To describe a new technique of a purely endoscopic procedure to disconnect the corpus callosum, the anterior, posterior, and habenular commissures through the use of a single burr hole via a transfrontal transventricular route. METHODS: Our surgical series was retrospectively reviewed in terms of seizure control (Engel's class) and complication rate. Five cadaveric specimens were used to demonstrate the surgical anatomy of commissural fibers and third ventricle. RESULTS: The procedure may be divided into 3 steps: (1) endoscopic transventricular transforaminal anterior commissure disconnection; (2) disconnection of posterior and habenular commissures; and (3) total callosotomy. Fifty-seven patients were included in the analysis. A favorable outcome in terms of epilepsy control (Engel class 1 to 3) was found in 71.4% of patients undergoing callosotomy coupled with anterior, posterior, and habenular commissure disconnection against 53% of patients with isolated callosotomy (P = .26). Patients with drop attacks had better epilepsy outcome independently from the surgical procedure used. CONCLUSION: The full endoscopic callosotomy coupled with disconnection of anterior, posterior and habenular commissures is a safe alternative to treat multifocal refractory epilepsy. A gain in seizure outcome might be present in this cohort of patients treated with total interhemispheric disconnection when compared with isolated callosotomy. Larger studies are required to confirm these findings.

Physical Growth of the Contralateral Cerebrum is Preserved After Hemispherotomy in Childhood.

BACKGROUND: Hemispherotomy can be an effective treatment for refractory childhood epilepsy. However, the extent of postoperative brain development after hemispherotomy remains incompletely understood. This study aims to provide an anatomic foundation in assessing development of the contralateral hemisphere, by measuring volumetric growth after hemispherotomy. METHODS: Eleven patients with hemimegalencephaly, Rasmussen's encephalitis, and cerebral infarction who underwent hemispherotomy before age 12 years, an immediate preoperative magnetic resonance imaging, and at least three years of follow-up magnetic resonance imagings were retrospectively analyzed. The volume of the contralateral hemisphere was measured before and after surgery. Growth curves were compared with those of healthy individuals from an open database. The growth rate relative to the healthy individuals ("catch-up rate") was calculated. RESULTS: A positive volumetric growth of the contralateral hemisphere was observed across all pathologies. The hemimegalencephaly subgroup underwent hemispherotomy at the earliest time and had the largest postoperative growth rate, which exceeded that of healthy individuals. The Rasmussen subgroup underwent surgery at the second earliest time and had an intermediate growth rate, which was similar to that of healthy individuals. The infarction subgroup underwent surgery at the latest time and had the slowest growth rate, which was less than that of healthy individuals. CONCLUSIONS: The contralateral hemisphere continues to increase in volume after hemispherotomy in childhood. Further studies with a larger sample size and correlation with cognitive outcomes may aid in characterizing the prognosis after hemispherotomy.

Morphology of the lateral fossa of the brain (sylvian valley): anatomo-radiological aspects and surgical application.

INTRODUCTION: The knowledge acquired on the lateral fossa of the brain (LFB) is heterogeneous and incomplete. Our goal was to provide a morphological description of the LFB and analyze the impact of these descriptions on the surgical approach of the region. METHODS: The morphology of LFB was studied on 40 cerebral hemispheres of 20 right-handed subjects aged 18-55 years with an MRI of 1.5 T. The anatomo-radiological identification of the two section levels preceded the description of the shapes of the LFB. From these landmarks, the forms presented by the LFB were identified and described on each of the transverse, sagittal and frontal planes. The comparison of the proportion of shapes made it possible to identify the typical shapes at each section level and on each section plane. RESULTS: The average age of the subjects was 33 years with extremes of 19 and 54 years including 7 women and 13 right-handed men. According to the plane and the level of section, 6 typical morphologies of the LFB have been described, 2 of which were identical. The forms did not vary according to the cerebral hemisphere or the sex of the subject. The set of typical morphologies made it possible to determine a reference subject called NSK which presented the greatest number of typical morphological characteristics. CONCLUSION: Knowledge of LFB anatomical imaging is of paramount importance in the pre-surgical evaluation of pathologies in this region. The reference subject will be used for our future biometric and three-dimensional manual reconstruction work in this region.

Meningiomas quísticos: correlación radiológica y patológica con implicaciones quirúrgicas / Cystic meningiomas: Radiological and pathological correlation with surgical implications

Introducción: Los meningiomas que asocian cambios quísticos prominentes (MQ) han representado un reto diagnóstico y terapéutico desde los orígenes de la neurocirugía moderna. Presentamos la experiencia en el manejo clínico y quirúrgico de esta entidad en nuestro Servicio. Material y métodos: En este estudio descriptivo se incluyen los MQ intervenidos en nuestro Servicio en los últimos 15 años, evaluando las variables clínicas, diagnósticas y terapéuticas de este subgrupo de meningiomas, con especial énfasis en la correlación de los hallazgos radiológicos y patológicos. Los tumores se clasificaron siguiendo el esquema propuesto por Nauta y sus colaboradores. Resultados: Se identificaron 11 casos, lo que supone un 1,8% de los meningiomas intervenidos en ese periodo. Todos los pacientes eran adultos y 8 de ellos, mujeres. Entre los síntomas, destacó la alta frecuencia de crisis epilépticas, mientras que solo un caso desarrolló hipertensión intracraneal aguda. La morfología predominante fue el tipo 2, seguida de los tipos 1, 3 y 4. En 5 casos pudo establecerse un diagnóstico radiológico inequívoco de meningioma. Todos los pacientes fueron tratados mediante cirugía, sin evidenciarse casos de recurrencia durante un seguimiento medio de 52,8 meses. Aunque la mayoría de las neoplasias correspondieron al grado i de la OMS, incluyendo subtipos variados, 4 de ellas fueron diagnosticadas como meningiomas atípicos. Conclusiones: De forma excepcional, los meningiomas pueden desarrollar cambios quísticos, intra- o extratumorales, en número y tamaño variable. Estos constituyen hallazgos poco típicos que pueden dificultar seriamente su diagnóstico diferencial radiológico. Los meningiomas con quistes periféricos de cápsula fina (tipos 2 y 3) suponen el escenario quirúrgico más complejo, pues el realce capsular en las pruebas de imagen no traduce necesariamente infiltración tumoral, mientras que el quiste puede contener células neoplásicas. Por lo tanto, recomendamos realizar al menos biopsia de la cápsula o seudocápsula, y lavado minucioso de la cavidad quirúrgica especialmente en estos subtipos

Introduction: Meningiomas associating prominent cystic changes (CM) have challenged neurosurgeons since the beginning of this surgical discipline. We present the experience in the diagnostic and therapeutic management of this entity in our institution. Material and methods: A review of our patient database was carried out, searching for those CM that were operated on in the last 15 years. Relevant clinical data were recorded and analyzed for each case, with special emphasis in the correlation of radiological and pathological findings. Cystic changes were classified according to the scheme proposed by Nauta et al. Results: A total of 11 patients were gathered, which represents 1.8% of the meningiomas operated on in our department during the period studied. All were adults, predominantly female patients (8 cases). Among the clinical symptoms a high rate of epileptic seizures was observed while only one patient developed acute intracranial hypertension. Morphologically, most tumors corresponded to type 2 CMs, followed by types 1, 3 and 4. In only five patients an unequivocal radiological diagnosis of meningioma could be made. All neoplasms were surgically removed and there were no records of recurrence (mean follow-up: 52.8 months). Microscopic findings were consistent with the pathological diagnosis of atypical meningioma in 4 cases, while the remaining tumors corresponded to OMS grade I neoplasms with variable microscopic patterns. Conclusions: Meningiomas can exceptionally associate cystic changes, both intra and/or extratumoral, in variable number and size. When cystic changes become too prominent (a large number or big-sized cysts), a serious preoperative diagnostic dilemma may arise. The surgical management of those CMs displaying a peripheral, thin-walled cyst (types 2 and 3) is especially complex, as contrast enhancement of the tumor wall did not correlate strictly with neoplastic invasion; even in the absence of this feature free floating islands of meningothelial cells intermixed with cyst fluid can be found. Consequently both surgical biopsy of every suspicious tissue and copious irrigation of the surgical cavity are strongly recommended for these CM types

Validação de manual de cuidados de idosos após cirurgia cerebral / Validation of elderly care manual after brain surgery

Objetivo: validar a tecnologia educacional "Manual de cuidados familiares com a pessoa idosa submetida à cirurgia cerebral". Método: trata-se de um estudo metodológico realizado em duas etapas: validação de conteúdo com 11 juízes especialistas e validação semântica com oito representantes do público-alvo. Aplicou-se, em cada etapa, um questionário validado do tipo Likert. Utilizou-se a estatística descritiva para a obtenção do índice de validade de conteúdo e índice de validade semântica. Resultados: revela-se que o índice de validade de conteúdo entre os juízes especialistas foi de 0,80 e o índice da validade semântica entre o público-alvo foi de 0,98. Conclusão: validou-se o manual em conteúdo e aparência como tecnologia educacional para apoiar familiares de pessoas idosas submetidas à cirurgia cerebral e mediar o trabalho educativo da equipe multidisciplinar, principalmente o enfermeiro, podendo repercutir positivamente no cuidado pós-alta hospitalar. (AU)

Objective: to validate the educational technology "Manual of family care for the elderly subjected to brain surgery". Method: this is a methodological study conducted in two stages: content validation with 11 expert judges and semantic validation with eight representatives of the target audience. At each stage, a validated Likert questionnaire was applied. Descriptive statistics was used to obtain the content validity index and semantic validity index. Results: it is revealed that the content validity index among expert judges was 0.80 and the semantic validity index among the target audience was 0.98. Conclusion: the manual was validated in content and appearance as educational technology to support relatives of elderly people undergoing brain surgery and mediate the educational work of the multidisciplinary team, especially the nurse, and can positively impact post-discharge care.(AU)

Objetivo: validar la tecnología educativa "Manual de cuidados familiares para ancianos sometidos a cirugía cerebral". Método: este es un estudio metodológico realizado en dos etapas: validación de contenido con 11 jueces expertos y validación semántica con ocho representantes del público objetivo. En cada etapa, se aplicó un cuestionario de Likert validado. Se utilizó la estadística descriptiva para obtener el índice de validez de contenido y el índice de validez semántica. Resultados: se revela que el índice de validez de contenido entre los jueces expertos fue de 0,80 y el índice de validez semántica entre el público objetivo fue de 0,98. Conclusión: el manual fue validado en contenido y apariencia como tecnología educativa para apoyar a los familiares de personas mayores que se someten a cirugía cerebral y mediar en el trabajo educativo del equipo multidisciplinario, especialmente el enfermero, y puede tener un impacto positivo en la atención posterior al alta.(AU)

Right Hemisphere Cognitive Functions: From Clinical and Anatomical Bases to Brain Mapping During Awake Craniotomy. Part II: Neuropsychological Tasks and Brain Mapping.

The nondominant hemisphere (usually right) is determinant for main cognitive functions such as visuospatial and social cognitions. Awake surgery using direct electrical stimulation for right cerebral tumor removal remains challenging due to the complexity of the functional anatomy and the difficulties in adapting the classical bedside tasks for awake surgery conditions. An understanding of semiology, anatomical bases, and an analysis of the available cognitive tasks for visuospatial and social cognition per operative mapping will allow neurosurgeons to better appreciate the functional anatomy of the right hemisphere and its application to tumor surgery. In this second review of 2 parts, we discuss the pertinence of the neuropsychological tests available for the study of nondominant hemisphere functions for the surgery on right-sided tumors in awake surgery conditions. In conjunction with part I of the review, which focuses primarily on the anatomical, functional, and semiological basis of the right hemisphere function, this article provides a comprehensive review of current knowledge supporting the awake surgery in the right hemisphere.

CO2 Laser in Neurosurgery: A Hands-on Experience.

Since its first use in 1963 by Engr. Kumar Naranbhai Patel, carbon dioxide (CO2) laser has evolved to attain a vital role in surgical neurology. The utilisation of laser is increasing in neurosurgery, especially minimally invasive and functional procedures. The laser serves three important functions in surgical procedures: photo-coagulation, photo-vaporisation, and photo-activation. Due to its favorable properties, CO2 laser is now recommended for many neurosurgical procedures. The development of low profile, and flexible transfer media has facilitated the use of laser in micro-neurosurgical procedures. CO2 laser has gained popularity as a unique cutting tool. The characteristic features of CO2 laser cause photo-vaporisation more than photo-coagulation. This allows to achieve a contact-free, relatively bloodless excision of many highly vascular lesions, especially helpful in critical anatomical areas. In this report, we share our first hands-on experience with flexible CO2 laser at Prince Sultan Military Medical City, Riyadh. The CO2 laser was utilised to achieve intracranial resection of a huge, markedly vascular glomus jugulare lesion. There was a significant reduction in blood loss with laser use, when compared with surgical resection utilising bipolar cautery, suction and cavitron ultrasonic aspirator. Postoperative recovery was also rapid and uneventful due to relatively less edema at surgical bed. We would like to favour the use of CO2 laser, especially when dealing with complex lesions with increased vascularity located in close relationship with vital neural and vascular structures in an attempt to minimise damage to intact tissue.

Right Hemisphere Cognitive Functions: From Clinical and Anatomic Bases to Brain Mapping During Awake Craniotomy Part I: Clinical and Functional Anatomy.

The nondominant hemisphere (usually the right) is responsible for primary cognitive functions such as visuospatial and social cognition. Awake surgery using direct electric stimulation for right cerebral tumor removal remains challenging because of the complexity of the functional anatomy and difficulties in adapting standard bedside tasks to awake surgery conditions. An understanding of semiology and anatomic bases, along with an analysis of the available cognitive tasks for visuospatial and social cognition per operative mapping allow neurosurgeons to better appreciate the functional anatomy of the right hemisphere and its relevance to tumor surgery. In this article, the first of a 2-part review, we discuss the anatomic and functional basis of right hemisphere function. Whereas part II of the review focuses primarily on semiology and surgical management of right-sided tumors under awake conditions, this article provides a comprehensive review of knowledge underpinning awake surgery on the right hemisphere.

Microsurgical anatomy of the central core of the brain.

OBJECTIVE The purpose of this study was to describe in detail the cortical and subcortical anatomy of the central core of the brain, defining its limits, with particular attention to the topography and relationships of the thalamus, basal ganglia, and related white matter pathways and vessels. METHODS The authors studied 19 cerebral hemispheres. The vascular systems of all of the specimens were injected with colored silicone, and the specimens were then frozen for at least 1 month to facilitate identification of individual fiber tracts. The dissections were performed in a stepwise manner, locating each gray matter nucleus and white matter pathway at different depths inside the central core. The course of fiber pathways was also noted in relation to the insular limiting sulci. RESULTS The insular surface is the most superficial aspect of the central core and is divided by a central sulcus into an anterior portion, usually containing 3 short gyri, and a posterior portion, with 2 long gyri. It is bounded by the anterior limiting sulcus, the superior limiting sulcus, and the inferior limiting sulcus. The extreme capsule is directly underneath the insular surface and is composed of short association fibers that extend toward all the opercula. The claustrum lies deep to the extreme capsule, and the external capsule is found medial to it. Three fiber pathways contribute to form both the extreme and external capsules, and they lie in a sequential anteroposterior disposition: the uncinate fascicle, the inferior fronto-occipital fascicle, and claustrocortical fibers. The putamen and the globus pallidus are between the external capsule, laterally, and the internal capsule, medially. The internal capsule is present medial to almost all insular limiting sulci and most of the insular surface, but not to their most anteroinferior portions. This anteroinferior portion of the central core has a more complex anatomy and is distinguished in this paper as the "anterior perforated substance region." The caudate nucleus and thalamus lie medial to the internal capsule, as the most medial structures of the central core. While the anterior half of the central core is related to the head of the caudate nucleus, the posterior half is related to the thalamus, and hence to each associated portion of the internal capsule between these structures and the insular surface. The central core stands on top of the brainstem. The brainstem and central core are connected by several white matter pathways and are not separated from each other by any natural division. The authors propose a subdivision of the central core into quadrants and describe each in detail. The functional importance of each structure is highlighted, and surgical approaches are suggested for each quadrant of the central core. CONCLUSIONS As a general rule, the internal capsule and its vascularization should be seen as a parasagittal barrier with great functional importance. This is of particular importance in choosing surgical approaches within this region.

Damage of the right dorsal superior longitudinal fascicle by awake surgery for glioma causes persistent visuospatial dysfunction.

Patients with glioma frequently present with neuropsychological deficits preoperatively and/or postoperatively, and these deficits may remain after the chronic phase. However, little is known about postoperative recovery course of right hemispheric function. We therefore studied the characteristics and causes of persistent cognitive dysfunction in right cerebral hemispheric glioma. Eighteen patients who underwent awake surgery participated in this study. All patients who received preoperative neuropsychological examinations were assigned to two groups according to their test results: preoperative deficit and normal. They were reassessed 1 week and 3 months after surgery. The rates of remaining deficits in the deficit group at chronic phase were higher than those of the normal group for all functions. Despite preoperative normal function, the remaining rate for visuospatial cognitive deficits was the highest among all functions. The voxel-based lesion-symptom mapping analysis for visuospatial cognition revealed that a part of the medial superior and middle frontal gyri were resected with high probability in patients with low visuospatial cognitive accuracy. Our study indicates that in patients with preoperative neuropsychological deficits, these deficits tend to remain until the chronic phase. Visuospatial dysfunction frequently persists until the chronic phase, which might reflect damage to the superior longitudinal fasciclus I and II.