Intra-axial Lesions Research Articles

The frontal aslant tract: Anatomical description and case report

Background: Advances in surgical techniques, neuroimaging, and white matter fiber dissection have facilitated the identification of critical tracts like the frontal aslant tract (FAT) that have garnered attention, despite remaining poorly recognized within the neurosurgical community. Case Description: We report the case of a 37-year-old male right-handed patient presenting with headache and epilepsy, in whom neuroimaging revealed an intra-axial lesion in the left middle frontal gyrus closely associated with FAT. Successful navigation-guided resection of the lesion was achieved, resulting in a favorable neurological outcome attributable to the preservation of the tract. This case is complemented by a review of the literature and anatomical dissection of FAT in a human specimen. Conclusion: The FAT has emerged as a critical white matter structure in neurosurgery, given its involvement in speech and motor functions. This case demonstrates the importance of advanced imaging modalities and intraoperative technologies to ensure safe resection.

Experiences in Awake Craniotomy from Borneo: A Case Series from Sarawak General Hospital.

The indications for awake craniotomy now spans from resection of tumours at eloquent areas of the brain, deep brain stimulation and treatment of aneurysms to name a few. In the region of East Malaysia where patients have various ethnic backgrounds and native languages, planning and execution of these procedures can be somewhat challenging. This is a retrospective analysis of 11 awake surgeries conducted by the Department of Neurosurgery in Sarawak. The indications for awake craniotomy surgery in our sample population were intra-axial lesions in eloquent regions involving important cortical areas and subcortical tracts which were at risk of damage during tumour excision. Patients were assessed for intra-operative and post-operative neurological deficits. Eleven patients aged 20 years old-70 years old were included in this series. All patients were diagnosed with lesions in eloquent areas of the brain requiring surgical excision. Patients were of various ethnic backgrounds. The spoken language of these patients also varied based on their ethnicity. The histopathological diagnosis of nine patients were consistent with gliomas with three being of high grade. Three patients (27%) developed intra-operative deficits that were not present pre-operatively. This case series serve to demonstrate the feasibility of awake craniotomies even in centres without vast experiences in awake surgeries and ideal adjuncts which in comparison may be readily available in different centres. Although careful patient selection has been emphasised, it is a difficult feat in a region consisting of at least 30 different ethnic groups with distinct languages and cultures.

Diffusion-Weighted MRI for Intracranial Tumor Differentiation: Analyzing the Role of Apparent Diffusion Coefficient Values

Magnetic Resonance Imaging (MRI) has become a standard non-invasive method for evaluating brain lesions, offering highly detailed structural data. However, traditional MRI faces limitations in differentiating between various tumor components, peritumoral edema, and healthy brain tissue. Diffusion-Weighted Imaging (DWI), an advanced MRI modality, overcomes some of these challenges by measuring water molecule movement within tissues, providing additional insights for precise tumor evaluation. This study explores the diffusion characteristics of intracranial tumor components using DWI. Forty patients with intracranial tumors underwent both conventional MRI and DWI, utilizing an echo-planar diffusion imaging protocol to create apparent diffusion coefficient (ADC) maps. Absolute ADC values were calculated for tumor components, peritumoral edema, and normal brain tissue. Meningiomas emerged as the primary extra-axial lesions with higher ADC values than those of normal tissue, while gliomas—primarily astrocytomas—constituted the main intra-axial lesions with mean ADC values of 1.2 ± 0.69 x 10⁻³ mm²/s. This study concludes that DWI significantly enhances the diagnosis and characterization of intracranial neoplasms, improving differentiation between tumor components and surrounding tissues.

Symptomatic cerebral vasospasm after posterior fossa surgery in pediatric patients: single-center study and systematic literature review.

The most common cause of cerebral vasospasm is subarachnoid hemorrhage, less frequently it occurs after trauma, infection, and tumor resection. Vasospasm in children is rare and has not been systematically investigated in posterior fossa surgery. The authors undertook a single-center retrospective study of all the pediatric patients who underwent surgery on the posterior fossa and presented with postoperative symptomatic vasospasm in the period from January 2018 to February 2024. Subsequently, a systematic literature review in accordance with the PRISMA guidelines was performed in the PubMed and Scopus databases to identify the published papers on symptomatic vasospasm after posterior fossa surgery in children. Of the 178 patients who underwent surgery on the posterior fossa, only one patient was diagnosed with symptomatic diffuse vasospasm on postoperative day 21. The systematic literature review provided further 9 children. The underlying pathology comprised 8 intra-axial lesions with 4 medulloblastomas, 1 schwannoma in the medulla oblongata, 1 pilocytic astrocytoma, 1 primitive neuroectodermal tumor, and 1 arteriovenous malformation. The extra-axial lesions were 1 hypoglossal schwannoma and 1 oculomotor nerve schwannoma. Iatrogenic symptomatic vasospasm after posterior fossa surgery in children is a rare complication with an outcome ranging from complete recovery to the death of the patient. It is important for all staff involved in the care of patients undergoing surgery on the posterior fossa to be aware of this rare postoperative complication. The small number of patients affected does not allow a substantiated conclusion to be drawn about predictive risk factors.

Permanent unilateral visual loss and orbital compartment syndrome following unilateral frontal craniotomy: illustrative case.

Vision loss following supine craniotomy is an unexpected and devastating complication for the patient and the operating team. Postoperative vision loss (POVL) is commonly associated with cardiac, spinal, neck, and prone head surgeries, as they share common risk factors, such as a prone position, intraoperative hypotension, a longer anesthesia duration, and the use of vasopressors. Herein, the authors report a case of irreversible vision loss following a frontal craniotomy in the supine position together with a review of the literature. All published cases in the literature since the first reported case in 1970 are summarized. Possible etiologies and proposed preventive measures are discussed. Different pathologies, such as vascular, intra-axial, and extra-axial lesions, are associated with POVL and have similar clinical courses and nonrecovery rates, which raises the question of whether POVL begins during the exposure part of these surgeries. Preventive measures could include avoiding direct ocular pressure during flap reflection, the use of elastic bands or fishhooks to avoid stretching the orbital contents and impairing venous outflow, and a careful review of the venous drainage of frontal tumors, which could help avoid unnecessary large venous thrombi or waxing. The role of intraoperative visual neurophysiological monitoring in predicting POVL requires further exploration. https://thejns.org/doi/10.3171/CASE2434.

Literature Review on Effective Use of Modern Modalities in Management of Intra-Axial Brain Lesions

The significant health burden caused by intra-axial brain lesions and the difficulties associated with their diagnosis and treatment have prompted a large number of researchers and practitioners to investigate various diagnostic and treatment modalities for their effectiveness and safety. This study focuses on evaluating different pre-, intra- and postoperative techniques and analyzes their advantages and limitations to ultimately improve the management of this type of brain lesion. Through a critical analysis of various scientific sources, this research aimed to synthesize existing knowledge on the topic. Magnetic resonance imaging plays a crucial role in diagnosing and managing brain tumors. Functional MRI identifies functional brain areas, but tumor-induced blood flow changes can affect its reliability. Connectome analysis provides information on functional localization and brain networks, which became possible using diffusion tensor imaging, that visualizes white matter pathways, aiding in tumor boundary delineation and surgical planning. Studies suggest this method can predict tumor histology and prognosis. Intraoperative MRI improves the extent of tumor resection and potentially patient survival. But due to its limitations it has alternative intraoperative techniques, like intraoperative ultrasound, fluorescence-guided surgery, direct electrical stimulation, deep brain stimulation, but evidence for most of these methods is limited for most brain tumors. Only ultrasound showed real-time tumor visualization and residual disease analysis offering high accuracy and is relatively inexpensive compared to ioMRI. This study can be useful to neurosurgeons, neuro-oncologists, neurologists, neuro-radiologists, and will demonstrate prospects for further research.

HGG-43. DIFFUSE PEDIATRIC HIGH GRADE GLIOMA SUCCESSFULLY TREATED WITH MULTIMODAL THERAPY

Abstract BACKGROUND Pediatric high grade glioma (HGG) have a dismal prognosis despite aggressive treatment. In this report, we discuss a patient with HGG successfully treated with combination of resection, radiotherapy, chemotherapy, and biologic therapy. RESULTS An 8-year-old male presented with intermittent headaches, vomiting and fatigue. Imaging demonstrated four solid/cystic enhancing intra-axial lesions within the left cerebral hemisphere- two within the left frontotemporal region, one in the superior parietal region, and one in the temporal lobe, all with perilesional edema and resultant subfalcine herniation with midline shift. The patient underwent subtotal resection of the frontotemporal and parietal lesions. Histopathology was consistent with glioblastoma. Whole exome sequencing revealed alterations in TP53, ATRX, PTEN, TSC2 as well as subclonal mutation in NF1. The tumor was unable to be further classified by DNA methylation. However histopathologic and molecular findings support the diagnosis of diffuse pediatric-high grade glioma, H3-wildtype and IDH-wildtype. The patient received adjuvant 59.4 Gy focal proton therapy with concurrent temozolomide and maintenance chemotherapy with temozolomide and lomustine for 6 cycles. End of therapy imaging demonstrated complete resolution of all sites of disease. Due to high likelihood of recurrence, the patient was subsequently started on targeted therapy with everolimus and ribociclib which continue to be well tolerated without dose adjustments. The patient remains stable and without recurrence 2.5 years since diagnosis, and 15 months since initiation of biologic therapy. Additionally, the patient underwent testing for cancer predisposition which revealed presence of TP53 heterozygous mutation consistent with Li-Fraumeni syndrome. The patient remains without other malignancies on surveillance imaging per LFS guidelines. CONCLUSION Our case report illustrates the value of both chemotherapy and biologic therapy in treatment of HGG. In addition to this, it emphasizes the importance of germline testing for cancer predisposition in patients with high grade tumors.

Extra-skeletal intracranial mesenchymal chondrosarcoma: systematic-literature review.

Intracranial mesenchymal chondrosarcoma (IMC) is a rare malignant tumor in pediatric population. IMC can present as extra- or intra-axial lesion in pediatric patients, though the former is commoner causing raised intracranial pressure (ICP). Radiological diagnosis is a challenge in these cases, as is it difficult to differentiate these from other extra-axial neoplasms due to the wide differential diagnosis in pediatric population. We aim to systematically review the literature and present a rare case of extraskeletal intracranial mesenchymal chondrosarcoma treated with safe maximal resection. A systematic review of literature was conducted in accordance with PRISMA guidelines. PubMed and Scopus databases were queried using the search terms, "primary intracranial chondrosarcoma", "extraskeletal mesenchymal chondrosarcoma", "mesenchymal chondrosarcoma" and "pediatric". Presentation, surgical management and outcome of a 15-year-old male with an extraskeletal IMC are also described. The search yielded 25 articles which met the inclusion criteria. These published records consisted of 33 IMC cases with mean age at presentation of 9.81 ± 5.2years (range 2months to 18years). Frontal region was the commonest locations (11, 33.3%). Most common presentation was headache (14, 42.4%). All patients underwent surgical intervention: gross total resection (20, 60.6%), subtotal resection (9, 27.3%) and no extent mentioned (4, 12.1%). No adjuvant therapy was received in 15 patients (45.5%). On latest follow-up, 11 patients (33.3%) are on remission, 5 patients (15.2%) are symptom free, 3 patients (9.1%) had recurrence, 2 patients (6.1%) had metastasis and 9 patients (27.3%) expired. IMC is a rare entity in pediatric population with imaging findings which are non-characteristic leading to its diagnostic challenge. It can masquerade as other extra-axial intracranial neoplasm (meningioma or hemangiopericytoma). Combination of clinico-radiological and pathological examination can help in accurate diagnosis. SafeMaximal resection followed by radiotherapy is the preferred treatment strategy.

Cortical incisions and transcortical approaches for intra-axial and intraventricular lesions: A scoping review.

Transcortical approaches, encompassing various surgical corridors, have been employed to treat an array of intraparenchymal or intraventricular brain pathologies, including tumors, vascular malformations, infections, intracerebral hematomas, and epileptic surgery. Designing cortical incisions relies on the lesion location and characteristics, knowledge of eloquent functional anatomy, and advanced imaging such as tractography. Despite their widespread use in neurosurgery, there is a noticeable lack of systematic studies examining their common lobe access points, associated complications, and prevalent pathologies. This scoping review assesses current evidence to guide the selection of transcortical approaches for treating a variety of intracranial pathologies. A scoping review was conducted using the PRISMA-ScR guidelines, searching PubMed, EMBASE, Scopus, and Web of Science. Studies were included if ≥5 patients operated on using transcortical approaches, with reported data on clinical features, treatments, and outcomes. Data analysis and synthesis were performed. A total of 50 articles encompassing 2604 patients were included in the study. The most common primary pathology was brain tumors (60.6%), particularly gliomas (87.4%). The transcortical-transtemporal approach was the most frequently identified cortical approach (70.48%), and the temporal lobe was the most accessed brain lobe (55.68%). The postoperative course outcomes were reported as good (55.52%), poor (28.38%), and death (14.62%). Transcortical approaches are crucial techniques for managing a wide range of intracranial lesions, with the transcortical-transtemporal approach being the most common. According to the current literature, the selective choice of cortical incision and surgical corridor based on the lesion's pathology and anatomic-functional location correlates with acceptable functional outcomes.

Gastrointestinal bleeding following traumatic brain injury: A clinical study on predisposing factors and outcomes.

Traumatic brain injury (TBI) is one of the most common causes of death and disability worldwide. Stress ulcers are common in critically ill patients and can lead to life-threatening gastrointestinal bleeding (GIB). This study investigates the impact of predisposing factors on GIB and outcomes of TBI patients. This retrospective cohort study included TBI patients admitted between February 2019 and November 2021. Patients' demographic information and clinical characteristics were collected and divided into Post-TBI GIB and No-GIB groups. During clinical follow-up, the Glasgow Outcome Score (GOS) and mortality were assessed. The correlation between predisposing factors and GIB was investigated. Out of 164 eligible patients, 66.5% were males, and the mean age was 31.38 ± 13.44 years. There was a higher rate of severe TBIs (p<0.001), intra-axial lesions (P=0.014), hypotension at admission (p<0.001), and concurrent coagulopathies (p<0.001) in the Post-TBI GIB group compared to the No-GIB group. In contrast, the Glasgow Coma Scale (GCS) level upon admission and discharge (p<0.001) and serum hemoglobin level at admission (p<0.001) were lower in the Post-TBI GIB group than in the other group. Moreover, primary GCS (P=0.017) and hypotension at admission (P=0.009), spinal injury (P=0.028), and intra-axial brain injury (P=0.018) were independently associated with GIB in TBI patients. Primary GCS and hypotension at admission, spinal injury, and intra-axial brain injury are independent predictors for GIB in TBI patients. The presence of GIB in TBI patients is associated with worse neurological outcomes as assessed by GOS at approximately 18 months.

Neurocysticercosis with Classic Ring Enhancing Lesions in a Patient with AIDS: Case Report, Diagnostic Approach and Literature Review

Introduction: Human immunodeficiency virus (HIV) is a neurotrophic, neuroinvasive, and neurovirulent pathogen, which can cause direct infection of the central nervous system (CNS) but also predisposes to a variety of other neuroinfections through impaired T-cell mediated immunity. Among the imaging findings in HIV patient with CNS infection, the presence of ring-enhancing intracranial lesions are considered not rare but quite puzzling diagnostic dilemma. The differential diagnosis for theses lesions commonly includes metastasis, abscess, glioblastoma, infarct, contusion, demyelinating disease, radiation necrosis, resolving hematoma or infections. Many features need to be considered altogether to help narrow the differential. Case description: Male, 32 years old, with history of chronic smoking, pets: one cat dewormed and vaccinated, and positive diagnosis of HIV infection with a CD4 T lymphocyte count of 24 cells/mm3, without antiretroviral treatment. His main symptom was headache, associated with fever, nausea, and vomiting. Therefore, he was hospitalized for his diagnostic approach. Complete laboratory work was done, head CT, lumbar puncture, and MRI, finding rounded intra-axial lesions with well-defined and hyperintense edges in the parietal and occipital region with annular enhancement after the administration of contrast. After symptomatic treatment and anthelmintic therapy, a follow-up imaging study evidenced involution of these lesions. The patient met diagnostic criteria for definitive diagnosis of neurocysticercosis. Conclusion: Even though, Neurocysticercosis is not a rare disease, our group decided to publish this case report because its asocciation with an HIV positive patient, in which has not been yet linked to, in behalf of the lack of evidence and studies, considering the ethical issue of performing rutinary head CT scans in asymptomatic individuals.

Endoscopic transorbital resection of the temporal lobe: anatomic qualitative and quantitative study.

Starting from an anatomic study describing the possibility of reaching the temporal region through an endoscopic transorbital approach, many clinical reports have now demonstrated the applicability of this strategy when dealing with intra-axial lesions. The study aimed to provide both a qualitative anatomic description of the temporal region, as seen through a transorbital perspective, and a quantitative analysis of the amount of temporal lobe resection achievable via this route. A total of four cadaveric heads (eight sides) were dissected at the Laboratory of Surgical Neuroanatomy (LSNA) of the University of Barcelona, Spain. A stepwise description of the resection of the temporal lobe through a transorbital perspective is provided. Qualitative anatomical descriptions and quantitative analysis of the amount of the resection were evaluated by means of pre- and post-dissection CT and MRI scans, and three-dimensional reconstructions were made by means of BrainLab®Software. The transorbital route gives easy access to the temporal region, without the need for extensive bone removal. The resection of the temporal lobe proceeded in a subpial fashion, mimicking what happens in a surgical scenario. According to our quantitative analysis, the mean volume removed was 51.26%, with the most superior and lateral portion of the temporal lobe being the most difficult to reach. This anatomic study provides qualitative and quantitative details about the resection of the temporal lobe via an endoscopic transorbital approach. Our results showed that the resection of more than half of the temporal lobe is possible through this surgical corridor. While the anterior, inferior, and mesial portions of the temporal lobe were easily accessible, the most superior and lateral segment was more difficult to reach and resect. Our study serves as an integration to the current anatomic knowledge and clinical practice knowledge highlighting and also as a starting point for further anatomic studies addressing more selected segments of the temporal lobe, i.e., the mesial temporal region.

Intraoperative Neuromonitoring of the Visual Pathway in Asleep Neuro-Oncology Surgery.

Brain tumour surgery in visual eloquent areas poses significant challenges to neurosurgeons and has reported inconsistent results. This is a single-centre prospective cohort study of patients admitted for asleep surgery of intra-axial lesions in visual eloquent areas. Demographic and clinical information, data from tractography and visual evoked potentials (VEPs) monitoring were recorded and correlated with visual outcomes. Thirty-nine patients were included (20 females, 19 males; mean age 52.51 ± 14.08 years). Diffuse intrinsic glioma was noted in 61.54% of patients. There was even distribution between the temporal, occipital and parietal lobes, while 55.26% were right hemispheric lesions. Postoperatively, 74.4% remained stable in terms of visual function, 23.1% deteriorated and 2.6% improved. The tumour infiltration of the optic radiation on tractography was significantly related to the visual field deficit after surgery (p = 0.016). Higher N75 (p = 0.036) and P100 (p = 0.023) amplitudes at closure on direct cortical VEP recordings were associated with no new postoperative visual deficit. A threshold of 40% deterioration of the N75 (p = 0.035) and P100 (p = 0.020) amplitudes correlated with a risk of visual field deterioration. To conclude, direct cortical VEP recordings demonstrated a strong correlation with visual outcomes, contrary to transcranial recordings. Invasion of the optic radiation is related to worse visual field outcomes.

Detailed molecular and pathological analyses of primary intracranial embryonal rhabdomyosarcoma with a BRAF mutation: illustrative case.

The etiological significance of the RAS and PI3K pathways has been reported in systemic embryonal rhabdomyosarcoma (ERMS) but not in primary intracranial ERMS (PIERMS). Herein, the authors present a unique case of PIERMS with a BRAF mutation. A 12-year-old girl with progressive headache and nausea was diagnosed with a tumor in the right parietal lobe. Semi-emergency surgery revealed an intra-axial lesion that was histopathologically identical to an ERMS. Next-generation sequencing indicated a BRAF mutation as a pathogenic variation, but the RAS and PI3K pathways showed no alteration. Although there is no established reference class for PIERMS, the DNA methylation prediction was closest to that of ERMS, indicating the possibility of PIERMS. The final diagnosis was PIERMS. The patient underwent local radiotherapy (50.4 Gy) and multiagent chemotherapy, with no recurrence for 12 months after surgery. This may be the first case demonstrating the molecular features of PIERMS, especially the intra-axial type. The results showed a mutation in BRAF but not in the RAS and PI3K pathways, which is different from the existing ERMS features. This molecular difference may cause differences in DNA methylation profiles. Accumulation of the molecular features of PIERMS is necessary before any conclusions can be drawn.

Meningioma and glioma as the first collision brain tumour reported in small animals

We describe the clinical and pathological features of a brain collision tumour consisting of a fibrous meningioma and an anaplastic oligoastrocytoma in a 14-year-old male neutered French Bulldog. Computed tomography of the brain revealed a poorly defined, intra-axial lesion affecting the left frontal lobe. Following euthanasia, histological examination showed an anaplastic oligoastrocytoma invading the brain parenchyma and an adjacent fibrous meningioma. As synchronous intracranial tumours are rare in animals, the aims of this report are to describe the clinical, imaging and histopathological features of an intracranial collision tumour in a dog and highlight the importance of a complete histopathological study despite the imaging findings.

Imaging findings in carcinomatous encephalitis secondary to malignant melanoma

BackgroundThe case of disseminated cancer cell spreading throughout the brain is called “miliary metastases” or “carcinomatous encephalitis”, a very rare and critical condition (primarily associated with lung and breast cancer) in which there are multiple plaque with a perivascular distribution, made of punctate lesions spread in all the brain. To our knowledge this represents the fourth case of melanotic miliary brain metastases described in the literature, also associated with melanin content of the lesions that is already evident on unenhanced T1-weighted images.Case presentationA 75-year-old patient with history of metastatic cutaneous melanoma (BRAF V600E mutate, PD-L1 negative) in treatment with dabrafenib and trametinib after 9 years from the diagnosis developed severe cognitive-motor slowing. Contrast-enhanced brain MRI showed miliary enhancing intra-axial brain lesions involving supra- and sub-tentorial regions and also the perivascular spaces, characterized by a bright appearance on unenhanced T1-weighted images without signal hypointensity in T2*-weighted images, as for melanotic pattern. Thus, the radiological diagnosis of “carcinomatous encephalitis” was made. Neurological examination showed an alert and cooperative subject with increased reaction time in verbal and motor responses. No ocular motility disturbances were found, and there were no motor or sensory deficits in the four limbs. The finger-to-nose test was normal, and no coordination deficit was found bilaterally. Blood tests and body temperature demonstrated no signs of ongoing infection. Electroencephalography showed slow and punctate abnormalities in bilateral fronto-temporal regions, with left prevalence. Corticosteroid therapy was started during hospitalization, improving the clinical picture. The patient was then discharged after 4 days in good clinical conditions with the indication to start second-line treatment with ipilimumab and nivolumab and to perform a whole-brain irradiation.ConclusionsBrain MRI plays a crucial role for the non-invasive diagnosis of carcinomatous encephalitis and for the differential diagnosis with other pathologies. Awareness of the existence of this disorder even in patients with melanoma is necessary to avoid diagnostic delays. Miliary brain metastases should be suspected in all melanoma patients with new neurological findings and contrast-enhanced MRI should be performed to assess the real burden of the disease.

The T2-FLAIR mismatch sign as an imaging biomarker for oligodendrogliomas in dogs.

In humans, the T2-weighted (T2W)-fluid-attenuated inversion recovery (FLAIR) mismatch sign (T2FMM) is a specific imaging biomarker for the isocitrate dehydrogenase 1 (IDH1)-mutated, 1p/19q non-codeleted low-grade astrocytomas (LGA). The T2FMM is characterized by a homogeneous hyperintense T2W signal and a hypointense signal with a hyperintense peripheral rim on FLAIR sequences. In gliomas in dogs, the T2FMM has not been described. In dogs with focal intra-axial brain lesions, T2FMM will discriminate gliomas from other lesions. The T2FMM will be associated with the LGA phenotype and presence of microcysts on histopathology. Interobserver agreement for T2FMM magnetic resonance imaging (MRI) features will be high. One hundred eighty-six dogs with histopathologically diagnosed focal intra-axial lesions on brain MRI including oligodendrogliomas (n = 90), astrocytomas (n = 47), undefined gliomas (n = 9), cerebrovascular accidents (n = 33), and inflammatory lesions (n = 7). Two blinded raters evaluated the 186 MRI studies and identified cases with the T2FMM. Histopathologic and immunohistochemical slides of T2FMM cases were evaluated for morphologic features and IDH1-mutations and compared to cases without the T2FMM. Gene expression analyses were performed on a subset of oligodendrogliomas (n = 10) with and without T2FMM. The T2FMM was identified in 14/186 (8%) of MRI studies, and all dogs with T2FMM had oligodendrogliomas (n = 12 low-grade [LGO], n = 2 high-grade [HGO]; P < .001). Microcystic change was significantly associated with the T2FMM (P < .00001). In oligodendrogliomas with T2FMM, IDH1-mutations or specific differentially expressed genes were not identified. The T2FMM can be readily identified on routinely obtained MRI sequences. It is a specific biomarker for oligodendroglioma in dogs, and was significantly associated with non-enhancing LGO.

Dural Tail Sign and Middle Meningeal Artery Hypertrophy in Glioblastoma: A Rarity?

Dural tail sign and increased caliber of branches of the external carotid artery (ECA) are common findings in meningioma and they have been rarely reported in intra-axial lesions. Anyway, some cases of glioblastoma (GBM) are reported in the literature, mostly superficially localized, characterized by these 2 findings and therefore, misdiagnosed with meningioma. The aim of this study is to verify the prevalence of dural tail sign and hypertrophy of middle meningeal artery (MMA) in a large cohort of GBMs. 180 GBM patients were retrospectively evaluated. Deep or superficial localization of GBM was established and the presence of dural tail sign and hypertrophy of the ipsilateral MMA were assessed. The rate of tumor necrosis and the incidence of dural metastases during the radiological follow-up were also evaluated. Inter-rater reliability was calculated using Cohen's K-test. Dural tail sign and enlarged MMA were evident in 30% and 19% of 96 superficial GBM, respectively. Deep GBM did not present those signs. Only one patient developed dural metastasis at follow-up and no differences in terms of tumor necrosis and hypoxic biomarkers expression were evident among GBMs with and without dural and vessel signs. Dural tail sign and hypertrophy of the MMA in superficial GBM are more common than expected. They probably represent reactive rather than a neoplastic infiltration. Knowing these radiological signs may be important in terms of neurosurgery planning and avoiding excessive bleeding. Anyway, this hypothesis should be confirmed by a prospective neurosurgery studio.

Deep learning referral suggestion and tumour discrimination using explainable artificial intelligence applied to multiparametric MRI.

An appropriate and fast clinical referral suggestion is important for intra-axial mass-like lesions (IMLLs) in the emergency setting. We aimed to apply an interpretable deep learning (DL) system to multiparametric MRI to obtain clinical referral suggestion for IMLLs, and to validate it in the setting of nontraumatic emergency neuroradiology. A DL system was developed in 747 patients with IMLLs ranging 30 diseases who underwent pre- and post-contrast T1-weighted (T1CE), FLAIR, and diffusion-weighted imaging (DWI). A DL system that segments IMLLs, classifies tumourous conditions, and suggests clinical referral among surgery, systematic work-up, medical treatment, and conservative treatment, was developed. The system was validated in an independent cohort of 130 emergency patients, and performance in referral suggestion and tumour discrimination was compared with that of radiologists using receiver operating characteristics curve, precision-recall curve analysis, and confusion matrices. Multiparametric interpretable visualisation of high-relevance regions from layer-wise relevance propagation overlaid on contrast-enhanced T1WI and DWI was analysed. The DL system provided correct referral suggestions in 94 of 130 patients (72.3%) and performed comparably to radiologists (accuracy 72.6%, McNemar test; p = .942). For distinguishing tumours from non-tumourous conditions, the DL system (AUC, 0.90 and AUPRC, 0.94) performed similarly to human readers (AUC, 0.81~0.92, and AUPRC, 0.88~0.95). Solid portions of tumours showed a high overlap of relevance, but non-tumours did not (Dice coefficient 0.77 vs. 0.33, p < .001), demonstrating the DL's decision. Our DL system could appropriately triage patients using multiparametric MRI and provide interpretability through multiparametric heatmaps, and may thereby aid neuroradiologic diagnoses in emergency settings. Our AI triages patients with raw MRI images to clinical referral pathways in brain intra-axial mass-like lesions. We demonstrate that the decision is based on the relative relevance between contrast-enhanced T1-weighted and diffusion-weighted images, providing explainability across multiparametric MRI data. • A deep learning (DL) system using multiparametric MRI suggested clinical referral to patients with intra-axial mass-like lesions (IMLLs) similar to radiologists (accuracy 72.3% vs. 72.6%). • In the differentiation of tumourousand non-tumourousconditions, the DL system (AUC, 0.90) performed similar with radiologists (AUC, 0.81-0.92). • The DL's decision basis for differentiating tumours from non-tumours can be quantified using multiparametric heatmaps obtained via the layer-wise relevance propagation method.

Pituitary cryptococcoma in an immunocompetent patient with panhypopituitarism: illustrative case.

Cryptococcosis is the most common mycosis of the central nervous system. It may develop in immunocompetent and immunocompromised patients, the latter representing most cases. The most common presentation of the disease is meningitis, whereas intra-axial lesions in the form of cryptococcoma are less frequent with a greater tendency to present in immunocompetent patients. The presentation of pituitary cryptococcoma is exceptional. To the best of the authors' knowledge, there is only one case published in the medical literature. The authors present the case of a 30-year-old male without a relevant medical history. He was referred to our center with a pituitary mass on magnetic resonance imaging and panhypopituitarism. The patient underwent endonasal endoscopic transsphenoidal tumor resection, and a histopathological diagnosis of pituitary cryptococcoma was made. Medical management included fluconazole and intravenous amphotericin. This case underscores the neurosurgical and medical management of an exceptional clinical presentation of pituitary cryptococcoma in an immunocompetent patient. To the best of the authors' knowledge, there is only one case published in the medical literature. This case provides an invaluable review of the clinical, imaging, and therapeutic considerations regarding this exceptional clinical entity.