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We report 3 cases of intracerebral cyst revealed by an unusual evolution of extrapyramidal symptoms. Diagnosis was based on MRI and the patients were treated by a cystoperitoneal or a cysto-atrial shunt. The surgical procedure was successful in the 3 cases, resulting in the rapid disappearance of symptoms., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

The goal of this study was to find a registration technique to improve the alignment of ultrasound images taken before and after brain tumor resection. Validation was performed on 16 tumor cases in 2 ways: (1) manually selected tags on pre- and postresection ultrasounds were used to compute the mean Euclidean distance between corresponding points in the 2 volumes before and after registration; and (2) the surgeon was asked to rank and rate the quality of the alignment before and after registration. The mean distance was 2.7 mm after a rigid registration and 1.7 mm after a nonlinear registration. Of 16 cases, the surgeon determined that initially only 2 were satisfactorily aligned; after the rigid registration, 5 were satisfactory, and after the nonlinear registration, 13 were satisfactory. According to both the distance and the ranking metrics, the nonlinear registration approach significantly improved the alignment of the ultrasound images., (Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Purpose: One of the important challenges in the field of medical imaging is finding real clinical images with which to validate new image processing algorithms. This is particularly true for tracked 3D ultrasound images of the brain., Methods: In 2010, pre- and postoperative magnetic resonance and intraoperative ultrasound images were acquired from brain tumor patients involved in the authors' imaging study at the Montreal Neurological Institute., Results: These data are available online at the Montreal Neurological Institute's Brain Images of Tumors for Evaluation database, termed here the MNI BITE database. It contains ultrasound and magnetic resonance images from 14 patients. Each patient underwent a preoperative and a postoperative T1-weighted magnetic resonance scan with gadolinium enhancement, and multiple intraoperative B-mode images were acquired before and after resection. Corresponding features were manually selected in some image pairs for validation. All images are in MINC format, the file format used at the authors' institute for image processing. The MINC tools are available for free download at packages.bic.mni.mcgill.ca., Conclusions: This is the first online database of its kind. These images can be used by image processing scientists as well as clinicians wishing to compare findings from magnetic resonance and ultrasound imaging., (© 2012 American Association of Physicists in Medicine.)

Purpose: We present a new technique for registering magnetic resonance (MR) and ultrasound images in the context of neurosurgery. It involves generating a pseudo-ultrasound (pseudo-US) from a segmented MR image and uses cross-correlation as the cost function to register the pseudo-US to the real ultrasound data. The algorithm's performance is compared with that of a state-of-the-art technique that uses a median-filtered MR image to register to a Gaussian-blurred ultrasound using a normalized mutual information (NMI) objective function., Methods: The two methods were tested on data from 15 patients with brain tumor, including low-and high-grade gliomas, in both first operations and reoperations. Two metrics were used to evaluate registration accuracy: (1) the mean distance between corresponding points, identified on both MR and ultrasound images by two experts, and (2) ratings based on visual comparison by one neurosurgeon., Results: The mean residual distance of the pseudo-US technique, 2.97 mm, is significantly more accurate (p = .0011) than that of the NMI approach, 4.86 mm. The visual assessment shows that only 4 of the 15 cases had a satisfactory initial alignment based on homologous skin-point registration. There is a significant correlation between the quantitative distance measures and the qualitative ratings (rho = 0.785)., Conclusion: The results show that the pseudo-US rigid registration technique robustly improves the MRI-ultrasound alignment when compared with the initial alignment, even when applied to highly distorted brains and a large range of tumor sizes and appearances.

Background and Purpose: Biopsies of brain stem lesions are useful for histopathological analysis, which guide appropriate treatment. The frame-based stereotactic procedure is the gold standard technique for biopsies of the brain stem. For the past few years, a frameless stereotactic robot, the NeuroMate robot (Renishaw, UK) has also been used for brain biopsies. We report a retrospective study of 15 patients who underwent NeuroMate robot-guided biopsies of brain stem lesions to evaluate the efficiency and safety of the system., Methods: From January 2004 to March 2006, 15 patients (five children and ten adults) underwent 17 biopsies of brain stem lesions. The lesions were located in the mesencephalon in two cases, in the pons in seven cases, in the pons and the medulla oblongata in five cases, and in the whole midbrain in one case. The biopsy procedure comprised four stages: image acquisition, preoperative planning, patient-to-image registration, and operative procedure. A transcerebellar approach was used in 12 cases and a double oblique anterior frontal approach in five cases., Results: Two adults underwent a second procedure because the first biopsy was not contributive. There was no operative mortality. We observed two cases of transient morbidity and one case of permanent morbidity., Conclusions: The frameless NeuroMate robot is an efficient and safe instrument for biopsies of brain stem lesions. We believe that the use of frameless stereotactic techniques for brain stem biopsies could increase the number of biopsies and therefore improve the diagnostic yield and accuracy of the technique., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

The aim of this report is to illustrate the successful surgical management of five patients with suprasellar retrochiasmatic and diencephalo-mesencephalic tumours, using a trans-amygdala extension of the trans-temporal/trans-choroidal fissure approach. The procedure is described for five surgically treated patients with such lesions that includes three retrochiasmatic craniopharyngiomas, one hypothalamic hamartoma, and one pilocytic astrocytoma in the left crus cerebri. The management procedure included computed tomography scan (CT scan) and magnetic resonance imaging (MRI). The trans-temporal/trans-choroidal fissure approach enabled us to perform total tumour resection in four patients and a subtotal resection in one. Some technical aspects and pitfalls of the procedure are discussed. This method creates optimum conditions for a radical excision of various suprasellar retrochiasmatic and diencephalo-mesencephalic tumours without mortality and only minimum morbidity. However, no single surgical approach can provide access to the entire variety of tumours located in the suprasellar retrochiasmatic and diencephalo-mesencepalic region. Surgical approaches must be tailored to the site, type of lesion, and its extensions. This method is only another surgical option. Its successful use requires a familiarity with the anatomy of these regions and an understanding of its specificity for a radical excision of some selected tumours, as well as its limitations to access others types of lesions. Although, it seems effective, this approach needs to be evaluated by further experience, owing to the small number of patients reported in this series.

The authors present the case of a 33-year-old woman presenting with a 4-week history of vertigo and headaches. Physical examination revealed an isolated static cerebellar syndrome. Magnetic resonance imaging showed a homogeneously enhancing tumor located in the fourth ventricle. Complete surgical removal was performed and microscopic examination revealed a high-grade B-cell lymphoma. Postoperative investigations confirmed it to be primary. Only one case of primary isolated lymphoma of the fourth ventricle has been briefly reported in the medical literature. The authors suggest that primary lymphoma must be considered in the list of fourth ventricle tumors.