Differences in the MRI Signature and ADC Values of Diffuse Midline Gliomas with H3 K27M Mutation Compared to Midline Glioblastomas.

We conducted a two-center retrospective survey on standard MRI features including apparent diffusion coefficient mapping (ADC) of diffuse midline gliomas H3 K27M-mutant (DMG) compared to midline glioblastomas H3 K27M-wildtype (midGBM-H3wt). We identified 39 intracranial DMG and 18 midGBM-H3wt tumors. Samples were microscopically re-evaluated for microvascular proliferations and necrosis. Image analysis focused on location, peritumoral edema, degree of contrast enhancement and DWI features. Within DMG, MRI features between tumors with or without histomorphological GBM features were compared. DMG occurred in 15/39 samples from the thalamus (38%), in 23/39 samples from the brainstem (59%) and in 1/39 tumors involving primarily the cerebellum (2%). Edema was present in 3/39 DMG cases (8%) versus 78% in the control (midGBM-H3wt) group (p < 0.001). Contrast enhancement at the tumor rim was detected in 17/39 DMG (44%) versus 67% in control (p = 0.155), and necrosis in 24/39 (62%) versus 89% in control (p = 0.060). Strong contrast enhancement was observed in 15/39 DMG (38%) versus 56% in control (p = 0.262). Apparent diffusion coefficient (ADC) histogram analysis showed significantly higher skewness and kurtosis values in the DMG group compared to the controls (p = 0.0016/p = 0.002). Minimum relative ADC (rADC) values, as well as the 10th and 25th rADC-percentiles, were lower in DMGs with GBM features within the DMG group (p < 0.001/p = 0.012/p = 0.027). In conclusion, DMG cases exhibited markedly less edema than midGBM-H3wt, even if histomorphological malignancy was present. Histologically malignant DMGs and midGBM-H3wt more often displayed strong enhancement, as well as rim enhancement, than DMGs without histomorphological malignancy. DMGs showed higher skewness and kurtosis values on ADC-histogram analysis compared to midGBM-H3wt. Lower minimum rADC values in DMGs indicated malignant histomorphological features, likely representing a more complex tissue microstructure.

Evolution of microneurosurgical anatomy with special reference to the history of anatomy, surgical anatomy, and microsurgery: historical overview.

This article reviews the evolution of microneurosurgical anatomy (MNA) with special reference to the development of anatomy, surgical anatomy, and microsurgery. Anatomy can be said to have started in the ancient Greek era with the work of Hippocrates, Galen, and others as part of the pursuit of natural science. In the sixteenth century, Vesalius made a great contribution in reviving Galenian knowledge while adding new knowledge of human anatomy. Also in the sixteenth century, Ambroise Paré can be said to have started modern surgery. As surgery developed, more detailed anatomical knowledge became necessary for treating complicated diseases. Many noted surgeons at the time were also anatomists eager to spread anatomical knowledge in order to enhance surgical practice. Thus, surgery and anatomy developed together, with advances in each benefiting the other. The concept of surgical anatomy evolved in the eighteenth century and became especially popular in the nineteenth century. In the twentieth century, microsurgery was introduced in various surgical fields, starting with Carl O. Nylen in otology. It flourished and became popularized in the second half of the century, especially in the field of neurosurgery, following Jacobson and Suarez's success in microvascular anastomosis in animals and subsequent clinical application as developed by M.G. Yasargil and others. Knowledge of surgical anatomy as seen under the operating microscope became important for surgeons to perform microneurosurgical procedures accurately and safely, which led to the fuller development of MNA as conducted by many neurosurgeons, among whom A.L. Rhoton, Jr. might be mentioned as representative.

Microsurgical management of midbrain cavernous malformations: does lesion depth influence the outcome?

BACKGROUND: The purpose of this study was to clarify whether the intrinsic depth of midbrain cavernous malformations (MCMs) influenced the surgical outcome. METHODS: The authors conducted a retrospective study of 76 consecutive patients who underwent microsurgical resection of a MCM. The vascular lesions were categorized into 4 distinct groups based on how these lesions had altered the brainstem surface. Additionally, it was verified whether the actual aspect of the brainstem surface could be predicted only by evaluating the pertinent preoperative MRI slices. Clinical outcome was assessed by determining the modified Rankin Scale Score (mRS) before and after surgery. RESULTS: Twenty-three MCMs (30.3%) were located deeply within the midbrain. The overlying midbrain surface appeared to be normal (group nl). In 33 patients (43.4%), the midbrain surface showed only a yellowish discoloration (group yw). In another 14 individuals (18.4%), the midbrain surface was distorted by the underlying MCM and bulging out while the vascular lesion still remained covered by a thin parenchymal layer (group bg). In the smallest group comprising 6 patients (7.9%), the exophytic MCM had disrupted the midbrain surface and was clearly visible at microsurgical exposure (group ex). The mean mRS decreased in the group nl from 1.43 preoperatively to 0.61 at follow-up. CONCLUSION: This study demonstrates in a large patient population that a deep intrinsic MCM location is not necessarily associated with an unfavorable clinical outcome after microsurgical lesionectomy. Predicting the aspect of the midbrain surface by evaluating preoperative MR images alone was not sufficiently reliable.

Diffuse midline gliomas, H3 K27M-mutant are associated with less peritumoral edema and contrast enhancement in comparison to glioblastomas, H3 K27M-wildtype of midline structures.

PURPOSE: The entity 'diffuse midline glioma, H3 K27M-mutant (DMG)' was introduced in the revised 4th edition of the 2016 WHO classification of brain tumors. However, there are only a few reports on magnetic resonance imaging (MRI) of these tumors. Thus, we conducted a retrospective survey focused on MRI features of DMG compared to midline glioblastomas H3 K27M-wildtype (mGBM-H3wt). METHODS: We identified 24 DMG cases and 19 mGBM-H3wt patients as controls. After being retrospectively evaluated for microscopic evidence of microvascular proliferations (MVP) and tumor necrosis by two experienced neuropathologists to identify the defining histological criteria of mGBM-H3wt, the samples were further analyzed by two experienced readers regarding imaging features such as shape, peritumoral edema and contrast enhancement. RESULTS: The DMG were found in the thalamus in 37.5% of cases (controls 63%), in the brainstem in 50% (vs. 32%) and spinal cord in 12.5% (vs. 5%). In MRI and considering MVP, DMG were found to be by far less likely to develop peritumoral edema (OR: 0.13; 95%-CL: 0.02-0.62) (p = 0.010). They, similarly, were associated with a significantly lower probability of developing strong contrast enhancement compared to mGBM-H3wt (OR: 0.10; 95%-CL: 0.02-0.47) (P = 0.003). CONCLUSION: Despite having highly variable imaging features, DMG exhibited markedly less edema and lower contrast enhancement in MRI compared to mGBM-H3wt. Of these features, the enhancement level was associated with evidence of MVP.

Optimal access route for pontine cavernous malformation resection with preservation of abducens and facial nerve function.

OBJECTIVE: The aim of this study was to analyze the differences between posterolateral and posteromedial approaches to pontine cavernous malformations (PCMs) in order to verify the hypothesis that a posterolateral approach is more favorable with regard to preservation of abducens and facial nerve function. METHODS: The authors conducted a retrospective analysis of 135 consecutive patients who underwent microsurgical resection of a PCM. The vascular lesions were first classified in a blinded fashion into 4 categories according to the possible or only reasonable surgical access route. In a second step, the lesions were assessed according to which approach was performed and different patient groups and subgroups were determined. In a third step, the modified Rankin Scale score and the rates of permanent postoperative abducens and facial nerve palsies were assessed. RESULTS: The largest group in this series comprised 77 patients. Their pontine lesion was eligible for resection from either a posterolateral or posteromedial approach, in contrast to the remaining 3 patient groups in which the lesion location already had dictated a specific surgical approach. Fifty-four of these 77 individuals underwent surgery via a posterolateral approach and 23 via a posteromedial approach. When comparing these 2 patient subgroups, there was a statistically significant difference between postoperative rates of permanent abducens (3.7% vs 21.7%) and facial (1.9% vs 21.7%) nerve palsies. In the entire patient population, the abducens and facial nerve deficit rates were 5.9% and 5.2%, respectively, and the modified Rankin Scale score significantly decreased from 1.6 ± 1.1 preoperatively to 1.0 ± 1.1 at follow-up. CONCLUSIONS: The authors' results suggest favoring a posterolateral over a posteromedial access route to PCMs in patients in whom a lesion is encountered that can be removed via either surgical approach. In the present series, the authors have found such a constellation in 57% of all patients. This retrospective analysis confirms their hypothesis in a large patient cohort. Additionally, the authors demonstrated that 4 types of PCMs can be distinguished by preoperatively evaluating whether only one reasonable or two alternative surgical approaches are available to access a specific lesion. The rates of postoperative sixth and seventh nerve palsies in this series are substantially lower than those in the majority of other published reports.

Library Preparation for Small RNA Transcriptome Sequencing in Patients Affected by Cerebral Cavernous Malformations.

Small RNA sequencing by Illumina's Next Generation technology has revolutionized the transcriptome analysis by facilitating massive parallel sequencing of RNA molecules at low cost. Illumina's Next Generation RNA sequencing is ideal for profiling small RNA (microRNAs, snoRNAs, and piRNAs) libraries in the identification of novel biomarkers for better clinical diagnosis. This method offers significant advantages when compared to microarray analysis with the ability to identify novel transcripts, higher sensitivity, specificity, and detection of rare and low-abundance transcripts. Small RNAs, including microRNAs and snoRNAs, belong to the class of small non-coding RNAs with 50-200 nucleotides in length and are involved in post-transcriptional regulation of gene expression. Executing Illumina's Next Generation Sequencing technology, we have recently deciphered microRNAs and snoRNAs expressed in cerebral cavernous malformations (CCMs). Small RNA library preparation is a prerequisite step prior to RNA sequencing for the identification of microRNAs and snoRNAs. Here, we describe stepwise small RNA library preparation starting from total RNA isolated from CCMs patient until library validation using the Illumina® TruSeq® Small RNA Sample preparation kit. We believe this method will shed light into the functional identification of other novel small non-coding RNAs in CCMs that awaits discovery.

Transcriptome-wide Profiling of Cerebral Cavernous Malformations Patients Reveal Important Long noncoding RNA molecular signatures.

Cerebral cavernous malformations (CCMs) are low-flow vascular malformations in the brain associated with recurrent hemorrhage and seizures. The current treatment of CCMs relies solely on surgical intervention. Henceforth, alternative non-invasive therapies are urgently needed to help prevent subsequent hemorrhagic episodes. Long non-coding RNAs (lncRNAs) belong to the class of non-coding RNAs and are known to regulate gene transcription and involved in chromatin remodeling via various mechanism. Despite accumulating evidence demonstrating the role of lncRNAs in cerebrovascular disorders, their identification in CCMs pathology remains unknown. The objective of the current study was to identify lncRNAs associated with CCMs pathogenesis using patient cohorts having 10 CCM patients and 4 controls from brain. Executing next generation sequencing, we performed whole transcriptome sequencing (RNA-seq) analysis and identified 1,967 lncRNAs and 4,928 protein coding genes (PCGs) to be differentially expressed in CCMs patients. Among these, we selected top 6 differentially expressed lncRNAs each having significant correlative expression with more than 100 differentially expressed PCGs. The differential expression status of the top lncRNAs, SMIM25 and LBX2-AS1 in CCMs was further confirmed by qRT-PCR analysis. Additionally, gene set enrichment analysis of correlated PCGs revealed critical pathways related to vascular signaling and important biological processes relevant to CCMs pathophysiology. Here, by transcriptome-wide approach we demonstrate that lncRNAs are prevalent in CCMs disease and are likely to play critical roles in regulating important signaling pathways involved in the disease progression. We believe, that detailed future investigations on this set of identified lncRNAs can provide useful insights into the biology and, ultimately, contribute in preventing this debilitating disease.

Microsurgical Management of Midbrain Cavernous Malformations: Predictors of Outcome and Lesion Classification in 72 Patients.

BACKGROUND: Due to the complex segmental organization of the brainstem, it is preferable to study midbrain cavernous malformations (MCMs) separately from pontine and medullary lesions. OBJECTIVE: To evaluate clinical results after microsurgical removal of MCMs, assess predictors for outcome and introduce a topographical classification of MCMs. METHODS: A retrospective study was conducted on consecutive patients who underwent MCM resection. Clinical parameters before and after surgery, morphological CM features, surgical approaches and outcomes were analyzed. MCMs were classified according to their exact location within the midbrain and their axial and sagittal extension. RESULTS: The authors reviewed 72 patients (35 male). Lesions varied in size between 4 and 55 mm. The vast majority of patients benefited from surgery. The mean modified Rankin Scale (mRS) decreased significantly from 1.6 at admission to 1.3 at discharge and to 0.7 at follow-up (6-247 mo postoperatively). Five patients (6.9%) suffered from delayed hypertrophic olivary degeneration as visualized on magnetic resonance imaging. One male suffered from early postoperative re-bleeding that required surgical hematoma evacuation. There were no severe long tract impairment or other disabling complications, no delayed re-bleedings, and no surgical mortality. CONCLUSION: We present a new topographic classification of MCMs that may be useful for predicting the occurrence of postoperative eye movement disorders. Other predictors of persistent oculomotor disturbances are time interval between onset of symptoms and surgery, and patient's age over 40 yr. Early surgery is recommendable in patients with oculomotor disturbances. MCM size over 18 mm, patient age over 40 yr, and poor mRS at admission are important predictors for the long-term outcome.

Microsurgical resection of medullary cavernoma via the olivary zone by the retrosigmoid supracondylar approach.

Microsurgical resection of the medullary cavernoma is rare, comprising less than 15% of more than 250 surgeries of brainstem cavernoma performed by the senior author (H.B.).1 This video demonstrates a case of a cavernous malformation inside the lateral part of the medulla, which was surgically treated via the olivary zone by the retrosigmoid supracondylar approach in a half-sitting position. Osseous drilling of the lateral foramen magnum provided wide exposure of the cerebellomedullary cistern around the olive.2,3 The lesion was completely dissected at the appropriate cleavage plane from the normal parenchyma. The patient developed no new neurological deficits and had no recurrence during 3 years of follow-up after the operation. The video can be found here: https://youtu.be/7i7SccS5HmU.

Resection of brainstem cavernous malformation via perifacial zone through retrosigmoid supracondylar approach.

Hemorrhagic brainstem cavernous malformations carry a high risk of progressive neurological deficits owing to recurrent hemorrhages and hence require complete surgical resection while minimizing damage to the dense concentration of nuclei and fibers inside the brainstem. To access lesions inside the lower pons, the senior author (H.B.) has preferred to approach the lesions via the "perifacial zone" through the pontomedullary sulcus from the inferior surface of the pontine bulge for more than 20 years.1,2 This video demonstrates a case of a cavernous malformation inside the lower pons, which was surgically treated via the pontomedullary junction through the retrosigmoid supracondylar approach in a half-sitting position. The lesion was completely removed in piecemeal fashion through a tiny incision on the sulcus, which did not cause any new neurological deficits. The modified Rankin Scale improved from 4 before the surgery to 1, and the patient had no recurrence during the 2 years of follow-up. The advantage of this access and the dissection techniques for this challenging lesion are introduced, based on our experience with more than 230 surgeries of brainstem cavernoma. The video can be found here: https://youtu.be/0H_XqkQgQ9I.

Improving results in patients with foramen magnum meningiomas by translating surgical experience into a classification system and complexity score.

Foramen magnum meningiomas (FMMs) are challenging lesions and controversy still exists regarding their optimal management. In the present paper, we propose some principles of surgical treatment of FMMs. We analyzed our series of 39 patients: the average maximum diameter was 31.1 mm (sd, 10.7). In two cases, there was extradural extension. We operated all anterior lesions through dorsolateral approach to craniovertebral junction and all posterior lesions through midline suboccipital approach and C1 laminectomy, following the prevalence of side of the tumor. There were no complications except for one case of post-operative hypoglossus paresis. We translated our experience with surgery of foramen magnum meningiomas into a classification system and a complexity score, in order to assign a score to each individual case and plan the surgical strategy. When the complexity score is 5 or more, we propose subtotal removal, in consideration of the benign nature.

Surgical Treatment for Primary Brainstem Hemorrhage to Improve Postoperative Functional Outcomes.

BACKGROUND: It remains controversial whether primary brainstem hemorrhage (PBH) should be managed conservatively or treated promptly by surgical evacuation of the hematoma. In the present study, we discuss 5 cases of PBH that were treated surgically and the ability of surgical management to improve postoperative functional outcomes. METHODS: The 4 patients with pontine and medullary hemorrhage underwent surgery via the lateral or midline suboccipital and trans-rhomboid fossa approach in the half-sitting position. The patient with a midbrain hemorrhage underwent surgery via the subtemporal approach in the supine lateral position. We analyzed the postoperative functional outcomes 1 week after surgery and the modified Rankin scale scores 6 months after discharge. RESULTS: Three patients with disturbance of consciousness experienced improvement in their level of consciousness. Four patients with hemiparesis improved in motor function. Oculomotor nerve function improved in 2 of 3 cases. Facial nerve function improved in 2 of 2 cases. Spontaneous respiration improved in 1 patient. The postoperative modified Rankin scale scores improved in all 5 cases. CONCLUSIONS: Because of the good results with these 5 patients with PBH, this surgical strategy could be encouraged with exclusion criteria for early initiation of rehabilitation strategies. We hope to increase our number of patients to accumulate further evidence.

Genome-Wide Sequencing Reveals Small Nucleolar RNAs Downregulated in Cerebral Cavernous Malformations.

Cerebral cavernous malformations (CCM) are vascular malformations associated with abnormally dilated blood vessels and leaky capillaries that often result in hemorrhages. Despite recent advances, precise understanding of the cellular and molecular mechanism leading to the pathogenesis of CCM remains elusive. Emerging evidence indicates that small nucleolar RNAs (snoRNAs), belonging to the class of non-coding RNAs, may play a significant role as diagnostic markers in human diseases. However, there is no report till date that studied the role of snoRNAs in CCM biology. The objective of the current study was to identify snoRNAs associated with CCM pathogenesis. Using genome-wide small RNA sequencing, we identified a total of 271 snoRNAs reliably expressed in CCM. By applying additional statistical stringency, three snoRNAs (SNORD115-32, SNORD114-22, and SNORD113-3) were found to be significantly downregulated in CCM patient tissue samples (n = 3) as compared to healthy brains (n = 3). Deregulation of the selected snoRNAs was further validated by qRT-PCR. Further, cellular localization via in situ hybridization also confirmed robust reduction in the expression of SNORD115-32 and SNORD114-22 in CCM tissues as compared to the healthy controls. By applying high-throughput sequencing and cellular localization analyses, we report here for the first time the genome-wide expression profile of snoRNAs in CCM tissues and a robust downregulation of candidate snoRNAs in CCM conditions. Future studies should warrant the screening in large CCM patient cohorts and will be helpful in the development of potential biomarkers and improved clinical diagnosis.

Improvement of Respiratory Depression in a Patient with Primary Medullary Hemorrhage Following Removal of Hematoma in the Half-sitting Position.

Primary medullary hemorrhage is a rare event that may result in ataxic respiration. Although it remains controversial whether primary medullary hemorrhage should be managed conservatively or surgically, recent advancements in neuroimaging and microsurgical techniques have shown promise for improving outcomes and prognosis following surgery. The present report discusses the case of a 70-year-old woman admitted to our institution due to sudden-onset nausea and vomiting. The patient underwent surgical removal of a right medullary hematoma for the treatment of daytime respiratory depression and nocturnal apnea while in the half-sitting position. Following surgery, her spontaneous respiration improved, and she was discharged with independent gait. Despite the risk of venous air embolism, accumulating evidence suggests that the half-sitting position is suitable for brainstem surgery because gravity-assisted blood and irrigation drainage from the surgical field allows for cleaner dissection and reduces the need for bipolar coagulation.

Genome-Wide Sequencing Reveals MicroRNAs Downregulated in Cerebral Cavernous Malformations.

Cerebral cavernous malformations (CCM) are vascular lesions associated with loss-of-function mutations in one of the three genes encoding KRIT1 (CCM1), CCM2, and PDCD10. Recent understanding of the molecular mechanisms that lead to CCM development is limited. The role of microRNAs (miRNAs) has been demonstrated in vascular pathologies resulting in loss of tight junction proteins, increased vascular permeability and endothelial cell dysfunction. Since the relevance of miRNAs in CCM pathophysiology has not been elucidated, the primary aim of the study was to identify the miRNA-mRNA expression network associated with CCM. Using small RNA sequencing, we identified a total of 764 matured miRNAs expressed in CCM patients compared to the healthy brains. The expression of the selected miRNAs was validated by qRT-PCR, and the results were found to be consistent with the sequencing data. Upon application of additional statistical stringency, five miRNAs (let-7b-5p, miR-361-5p, miR-370-3p, miR-181a-2-3p, and miR-95-3p) were prioritized to be top CCM-relevant miRNAs. Further in silico analyses revealed that the prioritized miRNAs have a direct functional relation with mRNAs, such as MIB1, HIF1A, PDCD10, TJP1, OCLN, HES1, MAPK1, VEGFA, EGFL7, NF1, and ENG, which are previously characterized as key regulators of CCM pathology. To date, this is the first study to investigate the role of miRNAs in CCM pathology. By employing cutting edge molecular and in silico analyses on clinical samples, the current study reports global miRNA expression changes in CCM patients and provides a rich source of data set to understand detailed molecular machinery involved in CCM pathophysiology.

Pediatric intracranial primary anaplastic ganglioglioma.

BACKGROUND: Primary intracranial anaplastic gangliogliomas are rare tumors in the pediatric patient group. Most of them present with symptoms of elevated pressure or symptomatic epilepsy. Extraaxial location is far more common than axial location. On MRI examination, they mimic pilocytic astrocytomas. The outcome after surgery depends mainly on the possible amount of surgical resection, and oncological therapy is necessary to prevent recurrence of the disease. CASE REPORT: An 11-year-old boy presented with headache and double vision due to obstructive hydrocephalus. MRI of the brain revealed an axial partially contrast enhancing lesion in the quadrigeminal plate extending from the cerebellum to the pineal gland and causing hydrocephalus. Subtotal removal of the lesion was performed, and the diagnosis of an anaplastic ganglioglioma was established and confirmed by the reference center. At the latest follow up (3 months), the boy is without any neurological symptoms and scheduled for radiation therapy as well as chemotherapy.

Orbitozygomatic Craniotomy with Modified Zabramski's Technique: A Technical Note and Anatomic and Clinical Findings.

BACKGROUND: The surgical technique of orbitozygomatic craniotomy reported by Zabramski et al. is an excellent procedure, facilitating wide surgical exposure, easy orbital reconstruction, and a satisfactory postsurgical aesthetic outcome; however, it is anatomically complicated and technically difficult. We introduce a simplified technique of Zabramski's orbitozygomatic craniotomy and present the anatomic and clinical findings with cadaveric photos, illustrations, and a video. METHODS: The orbitozygomatic craniotomy was performed on 20 sides of 11 cadaveric heads, in which the cut between the inferior orbital fissure and superior orbital fissure was modified and simplified, and the shortest distance between them was measured. This technique was applied to 13 clinical cases, and craniotomy-associated aesthetic and functional complications were evaluated. RESULTS: The average of the shortest distance from the inferior orbital fissure to superior orbital fissure was 21.3 mm (range, 19-23 mm) on the 20 sides of the 11 cadaveric heads. In all 13 clinical cases, orbitozygomatic craniotomy could be achieved in a short time, while preserving the structure of the orbital wall. A hollow at the temple was noted in 1 patient, cerebrospinal fluid leak occurred in 2 patients, and transient facial pain occurred in 1 patient; however, no other craniotomy-associated aesthetic or functional complications, including enophthalmos, were found in any of the 13 patients. CONCLUSIONS: With this modified technique, Zabramski's ideal orbitozygomatic craniotomy could be achieved easily with only minimal complications, while realizing all advantages of the technique.

Intraoperative magnetic resonance imaging in pediatric neurosurgery: safety and utility.

OBJECTIVE The use of high-field intraoperative MRI has been largely studied for the treatment of intracranial tumors in adult patients. In this study, the authors investigated the safety, advantages, and limitations of high-field iMRI for cranial neurosurgical procedures in pediatric patients, with particular attention to craniopharyngiomas and gliomas. METHODS The authors performed 82 surgical procedures in patients under 16 years of age (range 0.8-15 years) over an 8-year period (2007-2014) using iMRI. The population was divided into 3 groups based on the condition treated: sellar region tumors (Group 1), gliomas (Group 2), and other pathological entities (Group 3). The patients' pre- and postoperative neurological status, the presence of residual tumor, the number of intraoperative scans, and complications were evaluated. RESULTS In Group 1, gross-total resection (GTR) was performed in 22 (88%) of the procedures and subtotal resection (STR) in 3 (12%). In Group 2, GTR, STR, and partial resection (PR) were performed, respectively, in 15 (56%), 7 (26%), and 5 (18%) of the procedures. In Group 3, GTR was performed in 28 (93%) and STR in 2 (7%) of the procedures. In cases of craniopharyngioma (Group 1) and glioma (Group 2) in which a complete removal was planned, iMRI allowed localization of residual lesions and attainment of the surgical goal through further resection, respectively, in 18% and 27% of the procedures. Moreover, in gliomas the resection could be extended from partial to subtotal in 50% of the cases. In 17% of the patients in Group 3, iMRI enabled the identification and further removal of tumor remnants. There was no intra- or postoperative complication related to the use of iMRI despite special technical difficulties in smaller children. CONCLUSIONS In this study, the use of iMRI in children proved to be safe. It was most effective in increasing the extent of tumor resection, especially in patients with low-grade gliomas and craniopharyngiomas. The most prominent disadvantage of high-field iMRI was the limitation with respect to operative positioning due to the configuration of the surgical table.

Predicting the necessity of anterior communicating artery division in the bifrontal basal interhemispheric approach.

BACKGROUND: The anterior communicating artery (ACoA) often limits surgical exposure in the anterior interhemispheric approach. Although division of the ACoA has been proposed occasionally, it is rarely practiced, and criteria for such a surgical maneuver remain unknown. Our purpose was to identify key factors that allow for predicting the necessity of controlled ACoA division in the bifrontal basal interhemispheric approach. METHOD: Twenty-two consecutive patients who underwent surgery via the bifrontal basal interhemispheric approach for removal of various pathologic brain lesions were examined. First, tumors were dichotomized into central and lateral lesions. Next, three tumor parameters were compared between cases with and without ACoA division in each, the central and lateral lesion groups, respectively: tumor volume, tumor depth (defined as distance between the ACoA and posterior tumor margin) and tumor laterality angle (defined as the geometric angle between the lateral tumor margin and sagittal midline). RESULTS: Tumor volume was not related in a statistically significant manner to ACoA division in both the central (P = 0.06) and lateral (P = 0.13) lesion groups, respectively. However, tumor depth was significantly correlated with ACoA division in the central lesion group (P = 0.01), whereas in the lateral lesion group, the tumor laterality angle showed a significant correlation with ACoA division (P = 0.04). CONCLUSIONS: Our results suggest that controlled ACoA division may be required in central lesions with a depth of 38 mm or more and in lateral lesions with an angle of 23 degrees or more as defined in this study. Two key factors were thus identified that may predict the necessity of controlled ACoA division before surgery.