Surgical Treatment of Posterior Circulation Aneurysms ­ Anatomical Study and Surgical Technique

Posterior circulation aneurysms represent 10­15% of intracranial aneurysms. The diagnosis is usually secondary to subarachnoid hemorrhage due to its initial asymptomatic presentation and higher risk of rupture compared with aneurysms in the anterior circulation. The surgical treatment of posterior circulation aneurysms is complex and challenging for neurosurgeons because of the particular anatomy of the posterior circulation with its close relation to the brainstem and cranial nerves and also because of the depth and narrowness of the surgical approach. Aneurysms from different locations have specific anatomical relationships and surgical approaches for better visualization and dissection. Therefore, a detailed anatomy knowledge of the posterior circulation is mandatory for an individualized preoperative planning and good neurological and angiographic outcomes.We selected the main aneurysm sites on the posterior circulation, such as: posterior inferior cerebellar artery, basilar trunk, basilar bifurcation, posterior cerebral artery (PCA) and superior cerebellar artery for a detailed description of the relevant anatomy related to aneurysm, and the main surgical approaches for its surgical treatment. Furthermore, we performed a literature review with the most recent outcomes regarding to the surgical treatment of posterior circulation aneurysms.

Aneurismas de circulação posterior representam de 10­15% dos aneurismas intracranianos. O diagnóstico, frequentemente, é secundário a hemorragia subaracnoide devido à apresentação assintomática na maioria dos casos e ao alto risco de sangramento comparado com aneurismas da circulação anterior. O tratamento cirúrgico de aneurismas de circulação posterior é complexo e desafiador para os neurocirurgiões devido à anatomia particular da região, profundidade do acesso cirúrgico, e relação intima com o tronco encefálico e os nervos cranianos. Aneurismas de diferentes localizações têm diferentes relações anatômicas e, portanto, acessos cirúrgicos específicos para melhor dissecção e visibilização de estruturas. Logo, um conhecimento detalhado de anatomia é mandatório para planejamento operatório individualizado e bons resultados clinico-radiológicos. Foram selecionadas as principais localizações de aneurismas de circulação posterior: Artéria cerebelar póstero-inferior; tronco de artéria basilar, bifurcação de artéria basilar, artéria cerebral posterior, e artéria cerebelar superior para detalhamento anatômico da anatomia relevante. O estudo objetiva realizar uma revisão da literatura dos principais resultados sobre tratamento cirúrgico de aneurismas de circulação posterior, além de descrever os principais pontos anatômicos relevantes à técnica microcirúrgica.

T1-weighted gradient-echo imaging, with and without inversion recovery, in the identification of anatomical structures on the lateral surface of the brain / T1 GRE e T1 IR GRE na identificação das estruturas anatômicas da face lateral do cérebro

Abstract Objective: To compare brain structures using volumetric magnetic resonance imaging with isotropic resolution, in T1-weighted gradient-echo (GRE) acquisition, with and without inversion recovery (IR). Materials and methods: From 30 individuals, we evaluated 120 blocks of images of the left and right cerebral hemispheres being acquired by T1 GRE and by T1 IR GRE. On the basis of the Naidich et al. method for localization of anatomical landmarks, 27 anatomical structures were divided into two categories: identifiable and inconclusive. Those two categories were used in the analyses of repeatability (intraobserver agreement) and reproducibility (interobserver agreement). McNemar's test was used in order to compare the T1 GRE and T1 IR GRE techniques. Results: There was good agreement in the intraobserver and interobserver analyses (mean kappa > 0.60). McNemar's test showed that the frequency of identifiable anatomical landmarks was slightly higher when the T1 IR GRE technique was employed than when the T1 GRE technique was employed. The difference between the two techniques was statistically significant. Conclusion: In the identification of anatomical landmarks, the T1 IR GRE technique appears to perform slightly better than does the T1 GRE technique.

Resumo Objetivo: Comparar os resultados de identificação de estruturas cerebrais utilizando imagens volumétricas isotrópicas por ressonância magnética, nas aquisições T1 GRE e T1 IR GRE. Materiais e métodos: Foram avaliados 120 blocos de imagens, de 30 indivíduos, com imagens extraídas dos hemisférios cerebrais esquerdo e direito, pelos dois métodos de aquisição: T1 GRE e T1 IR GRE. Com base no método de Naidich et al. para localização dos referenciais anatômicos, 27 estruturas anatômicas foram classificadas em duas categorias - identificável versus deixam dúvidas quanto à identificação somadas às não identificáveis - para análises de repetitividade (intraobservador) e reprodutibilidade (interobservadores). Foi utilizado o teste de McNemar para a avaliação do desempenho entre os dois métodos. Resultados: Após confirmação de ter havido boa concordância na análise intraobservador e interobservadores (kappa médio > 0,60), a avaliação das imagens de cada referencial anatômico, testada entre T1 GRE e T1 IR GRE pelo teste de McNemar, indicou maior frequência de referenciais identificáveis pelo método T1 IR GRE do que pelo método T1 GRE. Conclusão: O método de imagem T1 IR GRE apresentou desempenho levemente superior, porém estatisticamente significante, em relação ao método T1 GRE, na identificação dos referenciais anatômicos cerebrais.

Brain neuroimaging of domestic cats: correlation between computed tomography and cross-sectional anatomy / Neuroimagem cerebral de gatos domésticos: correlação entre a tomografia computadorizada e a anatomia seccional

Computed tomography of the brain is necessary as part of the diagnosis of lesions of the central nervous system. In this study we used six domestic cats, male or female, aged between one and five years, evaluated by Computed Tomography (CT) examination without clinical signs of central nervous system disorders. Two euthanized animals stating a condition unrelated to the nervous system were incorporated into this study. The proposal consisted in establishing detailed anatomical description of tomographic images of normal brain of cats, using as reference anatomical images of cross sections of the stained brain and cranial part, with thicknesses similar to the planes of the CT images. CT examinations were performed with and without intravenous iodinated contrast media for live animals. With one euthanized animal, the brain was removed and immediately preserved in 10% formalin for later achievement in cross-sectional thickness of approximately 4mm and staining technique of Barnard, and Robert Brown. The head of another animal was disarticulated in the Atlanto-occipital region and frozen at -20ºC then sliced to a thickness of about 5mm. The description of visualized anatomical structures using tomography is useful as a guide and allows transcribing with relative accuracy the brain region affected by an injury, and thus correlating it with the clinical symptoms of the patient, providing additional information and consequent improvement to veterinarians during the course of surgical clinic in this species.(AU)

A tomografia computadorizada do cérebro é de suma importância como parte do diagnóstico de lesões do sistema nervoso central. Neste estudo, foram utilizados seis felinos domésticos, machos ou fêmeas, com idade entre um e cinco anos, avaliados pela tomografia computadorizada (TC), sem sinais clínicos de distúrbios do sistema nervoso central. Dois cadáveres indicando a condição relacionada com o sistema nervoso foram incorporados ao presente estudo. A proposta consistiu na criação da descrição anatômica detalhada das imagens tomográficas de cérebro normal de gatos, usando como referência a imagens anatômicas de secções transversais do cérebro coradas, realizadas com espessuras similares aos planos das imagens tomográficas. Exames de TC foram realizados com e sem contraste iodado intravenoso para os animais vivos. Em um dos cadáveres, o cérebro foi removido e imediatamente preservado em formalina a 10% para a realização posterior da técnica de coloração de Barnard e Robert Brown, além de cortes transversais com espessura de, aproximadamente, 4mm. O crânio do outro cadáver foi desarticulado na região atlanto-occipital e congelado a -20ºC. Em seguida, foi realizado corte com espessura de cerca de 5mm. A descrição das estruturas anatômicas visualizadas foi útil e serve como guia, permitindo descrever com relativa precisão a estrutura cerebral normal ou lesionada, e, portanto, correlacionando-a com os sintomas clínicos de um paciente, o que fornece informações adicionais e consequente aprimoramento de veterinários no curso de clínica cirúrgica para essa espécie.(AU)

Factors associated with morphometric brain changes in cognitively normal aging / Fatores associados às alterações morfométricas encefálicas durante o envelhecimento sem comprometimento cognitivo

ABSTRACT. OBJECTIVE: Cognitive impairment is associated with reductions in brain weight and volume. The factors related to morphometric brain changes in cognitively normal aging remain unknown. We aimed to identify which clinical factors are associated with morphometric brain changes in cognitively normal aging. METHODS: A cross-sectional study of 414 subjects, ≥50 years old submitted to clinical assessment and brain autopsy, after informed consent, was carried out at the São Paulo Autopsy Service, Brazil. Data on cognitive and functional evaluations were collected through structured interview applied to the next-of-kin. Brain weight (g) and volume (mL) measurements were obtained and adjusted for head circumference (cm). Associations between brain weight/volume and related factors were obtained through univariate and multivariate analysis. RESULTS: Participants were predominantly male (60.4%), Caucasian (69%), with mean age of 67.1 ± 10.9 years. Mean brain weight was 1219.2 ± 140.9 g, and mean brain volume was 1217.1 ± 152.3 mL. Head circumference was independently associated with low brain weight (p<0.001) and volume (p<0.001). Total and adjusted brain weight and volume decreased in some conditions. Female gender (p<0.001), hypertension (p<0.009), coronary artery disease (p<0.013) and walking assistance (p<0.011) were associated with lower adjusted brain weight while schooling was associated with higher adjusted brain weight (p<0.003). Female gender (p<0.001), age (p<0.001) and hypertension (p<0.011) were associated with low adjusted brain volume. CONCLUSION: Morphometric brain changes occur despite the absence of cognitive impairment and were predominantly associated with age, female gender, mobility impairment and cardiovascular conditions. Schooling may be a protective factor.

RESUMO. OBJETIVO: O comprometimento cognitivo está associado à redução de massa e volume encefálicos. Fatores associados às alterações morfométricas crânio-encefálicas durante o envelhecimento cerebral normal são escassos. Nosso objetivo foi identificar quais os fatores clínicos associados às alterações morfométricas encefálicas em indivíduos sem comprometimento cognitivo. MÉTODOS: Estudo transversal, realizado no Serviço de Verificação de óbitos da Capital, em São Paulo - Brasil, em que 414 indivíduos, com idade ≥50 anos, foram submetidos à avaliação clínica e autópsia encefálica, após consentimento informado. A avaliação cognitiva e funcional foi obtida por meio da entrevista com familiares. Massa (g) e de volume (mL) encefálicos foram obtidos e ajustados para o perímetro cefálico (cm). A associação entre massa/volume encefálicos e os fatores relacionados (preditores) foi obtida por meio de análise univariada e multivariada. O p-valor foi fixado em 0,05. RESULTADOS: Participantes era em sua maioria homens (60,4%), com idade média de 67,1 ± 10,9 anos, e caucasianos (69%). A média de massa encefálica da amostra foi de 1219,2 ± 140,9 g, e a média do volume foi 1217,1 ± 152,3 mL. Perímetro cefálico esteve independentemente associado à redução de massa (p<0,001) e volume (p<0,001). Massa e volume (total e corrigido) reduziu em algumas condições. Gênero feminino (p<0,001), hipertensão (p<0,009), doença arterial coronariana (p<0,013) e auxílio para deambulação (p<0,011) foram fatores associados à redução da massa encefálica corrigida, enquanto a escolaridade esteve associada com seu aumento (p<0,003). A idade (p<0,001), o gênero feminino (p<0,001) e a hipertensão (p<0,011) estiveram associados à redução no volume encefálico corrigido. CONCLUSÃO: As alterações morfométricas encefálicas ocorrem apesar da inexistência de comprometimento cognitivo e são associadas à idade, ao gênero feminino, às alterações de mobilidade e às doenças cardiovasculares. A escolaridade parece ser um fator protetor.

Dimorfismo sexual no sistema nervoso central na espécie humana / Sexual dimorphism in the central nervous system in the human species

O estudo dos gêneros masculino e feminino, suas diferenças e seus comportamentos, tem sido fonte de incontáveis questionamentos em várias áreas do conhecimento humano ao longo de toda a história da Humanidade. Diversas especialidades têm estudado o tópico das diferenças entre homens e mulheres, porém esses estudos têm ocorrido de forma dissociada, dificultando a sua compreensão global e suas inter-relações. Partindo desse princípio, esta revisão teve como objetivo estudar a existência da relação entre as estruturas anatômicas do cérebro de pessoas com desenvolvimento normal e suas funcionalidades e os processos de diferenças comportamentais entre os gêneros masculino e feminino. A maioria dos trabalhos publicados entre 1990 e 2004 e aqui analisados é recorrente em suas conclusões ao apontarem diferenças em estruturas anatômicas e funcionais, em várias áreas dos cérebros de homens e mulheres.

The study of the genders, its differences and its behaviors, have been sources of countless questionings in some areas of the human knowledge throughout all the history of the Humanity. Various specialties have studied the topic of the differences between men and women; however these studies have occurred in unassociated ways, rendering difficulty for the global understanding and its relationships. The purpose of this review was to study the existence of relation between the anatomical structures of the brain among people with normal development and functionalities and the different behavior processes between male and female genders. Most of the analyzed papers published between 1990 and 2004 shows the existence of differences in anatomical and functional structures, in several areas of men's and women’s brains.

Somatotopic Mapping of the Supplementary Motor Area

PURPOSE: The purpose of this study was to assess supplementary motor area (SMA) activation during motor, sensory, word generation, listening comprehension, and working memory tasks using functional magnetic resonance imaging (fMRI). MATERIALS AND METHODS: Sixteen healthy right-handed subjects (9M, 7F) were imaged on a Siemens 1.5T scanner. Whole brain functional maps were acquired using BOLD EPI sequences in the axial plane. Each paradigm consisted of five epochs of activation vs. the control condition. The activation tasks consisted of left finger complex movement, hot sensory stimulation of the left hand, word generation, listening comprehension, and working memory. The reference function was a boxcar waveform. Activation maps were thresholded at an uncorrected p=0.0001. The thresholded activation maps were placed into MNI space and the anatomic localization of activation within the SMA was compared across tasks. RESULTS: SMA activation was observed in 16 volunteers for the motor task, 11 for the sensory task, 15 for the word generation task, 5 for the listening comprehension task, and 15 for the working memory task. The rostral aspects of the SMA showed activity during the word generation and working memory tasks, and the caudal aspects of the SMA showed activity during the motor and sensory tasks. Right (contralateral) SMA activation was observed during the motor and sensory tasks, and left SMA activation during the word generation and memory tasks. CONCLUSION: Our results suggest that SMA is involved in a variety of functional tasks including motor, sensory, word generation, and working memory. The results obtained also support the notion that functionally specific subregions exist within the region classically defined as the SMA.

Neuroradiology in the Ocular Motility Disorders: II. Nuclear and Infranuclear Pathway

The nuclear and infranuclear pathway of eye movement begins from the ocular mo-tor nuclei situated in thebrain stem, where the axons originate and form three ocular motor nerve s. Although each of the ocular motornerves follows a distinct route to reach the end organ, the extraocular muscles, they also have common housings inthe cavernous sinus and at the orbital apex, where part or all of them are frequently and simultaneously affectedby a common disease process. Since the fine details of normal and diseased structures can frequently be seen onradiologic imaging, especially mag-netic resonance (MR) imaging, a knowledge of the basic anatomy invo l ved innuclear and infranuclear eye movement is important. In this description, in addition to the normal nuclear andinfranuclear pathway of eye movement, we have noted the radio-logic findings of typical diseases involving eachsegment of the nuclear and infranu-clear pathway, particularly as seen on magnetic resonance images. Briefcomments on ocular motor pseudopalsy, which mimics ocular motor palsy, are also included.

Neuroradiology in the Ocular Motility Disorders: I. Supranuclear Pathway

The supranuclear control of eye movement invo l ves the pathway extending from the cerebral cortex to theocular motor nuclei located in the brain stem. This paper de-scribes the normal supranuclear pathway, whichcontrols eye movement. We also include magnetic resonance imaging findings of the typical ocular manifestationscaused by disorders involving the supranuclear pathway, providing the anatomic ex-planations for certain clinicalsigns.

Brain MR Imagings Finding in Patients with Central Vertigo

PURPOSE: To investigate brain lesions and their locations in patients with central vertigo, as seen on MRimaging. MATERIALS AND METHODS: We retrospectively reviewed MR images of 85 patients with central type vertigodiagnosed on the basis of clinical symptoms and vestibular function test (VFT), and analyzed lesions and theirlocations. Those located along the known central vestibular pathway were included in our study. RESULTS: In 29 of85 patients (34%), lesions considered to be associated with central vertigo were detected on MR imaging. Theseincluded infarction (18 patients), hemorrhage (5), tumor (2), cavernous angioma(1), cerebellopontine anglecyst(1), tuberous sclerosis(1) and olivopontocerebellar atrophy(1) ; they were located in the parietal lobe(6patients), the lateral medulla(5), the pons(5), the middle cerebellar peduncle(4), the corona radiata(3), and thecerebellar vermis(3). Thirty-eight cases showed high signal intensity lesions in deep cerebral matter, the basalganglia, and pons but these were considered to be unrelated to central vertigo. CONCLUSIONS: MR imaging could bea useful tool for the evaluation of patients with central vertigo.

Persistent Carotid-Vertebrobasilar Anastomosis: Radiologic Findings

PURPOSE: To evaluate the radiologic findings of carotid-vertebrobasilar anastomosis and associated anomalies. MATERIALS AND METHODS: Thirteen patients with fourteen cases of carotid-vertebrobasilar anastomosis collectedfrom January 1992 to December 1997 were reviewed. Clinical diagnosis refered for cerebral angiography werecerebral infarction(n=3), intracranial hemorrhage(n=2), subarachnoid hemorrhage(n=1), brain tumor(n=3),arteriovenous malformation(n=3) and trigeminal neuralgia(n=1). Cerebral angiograms and clinical symptoms wereretrospectively analyzed. RESULTS: The fourteen carotid-vertebrobasilar anastomsis consisted of eleven cases ofpersistent trigeminal artery and three cases of type I proatantal intersegmental artery. Persistent trigeminalarteries were associated with anterior communicating artery aneurysm(n=1), posterior fossa arteriovenousmalformation(n=2) and persistent trigeminal artery variant(n=5). Type I proatantal intersegmental arteries wereassociated with hypoplastic vertebral arteries(n=2) : only proximal segment in one, and proximal and distalsegments in one case. Only one patient had clinical symptom related to the carotid-vertebrobasilar anastomosiswhich was trigeminal neuralgia. CONCLUSION: Knowledge of the anatomical and radiologic findings ofcarotid-vertebrobasilar anastomosis and associated anomalies will aid in the accurate diagnosis of neurovasculardisease and prevent possible complications during surgical and interventional procedures.

Cerebellar Arteries Originating from the Internal Carotid Artery: Angiographic evaluation and Embryologic Explanations

PURPOSE: To find and describe the cerebellar arteries arising from the internal carotid artery, explain them embryologically, and evaluate their clinical implication. MATERIALS AND METHODS: To determine the point in the internal carotid artery from which the cereballar artery arose anomalously, consecutive angiographic studies performed in the last three years were reviewed. The distribution of such anomalous cerebellar arteries, the point in the internal carotid artery from which the anomalous vessels originated, and associated findings were analyzed. RESULTS: Five anomalous origins of cerebellar arteries arising arising directly from the internal carotid artery were found in five patients. Three anterior inferior cerebellar arteries (AICA) and one common trunk of an AICA and a posterior inferior cerebellar artery (PICA) were found to originate from the internal carotid artery at a point close to the origin of the primitive trigeminal artery. A PICA arose from an artery presenting a course similar to the proatlantal intersegmental artery. Intracranial aneurysms in two patients, Moyamoya disease in one, and facial arteriovenous malformation in one. CONCLUSION: In our series, AICAs supplied from the arteries considered to be persistent trigeminal artery variants were the most common type. A correlation between type of anomalous cerebellar artery and type of carotid-vertebrobasilar anastomosis may exist. Cerebellar arteries originating anomalously from the internal carotid artery seem to occur as a result of the persistence of carotid-vertebrobasilar anastomoses associated with incomplete fusion of the longitudinal neural arteries. An understanding of these anomalous cerebellar arteries may help prevent accidents during therapeutic embolization and surgical treatment, as well as misinterpretation.

Normal Position of the Cerebellar Tonsils in Korean

PURPOSE: To evaluate normal tonsillar position at different ages, using MR images. MATERIAL AND METHODS: We measured the position of the cerebellar tonsils with respect to the inferior aspect of the foramen magnum on middle sagittal MR T1 weight images in 210 patients(9 days to 83 years) who were not considered to have any disorder that would affect tonsillar position. RESULTS: The mean distance between tonsillar tip and inferior aspect of the foramen magnum was 0.0 +/-1.9mm in the first decade of life, 0.7 +/-2.8mm in the fourth decade, and3.4 +/-2.3 mm in the eighth and ninth decades. The tonsillar position is significantly lower in youth(first and second decades) than in old age(seventh to ninth decades). CONCLUSION: We believe that a single reference standard that indicates the normal distance of the cerebellar tonsils from the foramen magnum is inappropriate unless age is considered. We suggest that the following distance below the foramen magnum(more than 2 standard deviations out of the normal range) be used as criteria for ectopia of the cerebellar tonsils in koreans : firstand second decades, 5mm ; third to sixth decades, 4mm ; seventh and eighth decades, 3mm.