Arteriolar degeneration and stiffness in cerebral amyloid angiopathy are linked to ß-amyloid deposition and lysyl oxidase.

Cerebral amyloid angiopathy (CAA) is a vasculopathy characterized by vascular ß-amyloid (Aß) deposition on cerebral blood vessels. CAA is closely linked to Alzheimer's disease (AD) and intracerebral hemorrhage. CAA is associated with the loss of autoregulation in the brain, vascular rupture, and cognitive decline. To assess morphological and molecular changes associated with the degeneration of penetrating arterioles in CAA, we analyzed post-mortem human brain tissue from 26 patients with mild, moderate, and severe CAA end neurological controls. The tissue was optically cleared for three-dimensional light sheet microscopy, and morphological features were quantified using surface volume rendering. We stained Aß, vascular smooth muscle (VSM), lysyl oxidase (LOX), and vascular markers to visualize the relationship between degenerative morphological features, including vascular dilation, dolichoectasia (variability in lumenal diameter) and tortuosity, and the volumes of VSM, Aß, and LOX in arterioles. Atomic force microscopy (AFM) was used to assess arteriolar wall stiffness, and we identified a pattern of morphological features associated with degenerating arterioles in the cortex. The volume of VSM associated with the arteriole was reduced by around 80% in arterioles with severe CAA and around 60% in cases with mild/moderate CAA. This loss of VSM correlated with increased arteriolar diameter and variability of diameter, suggesting VSM loss contributes to arteriolar laxity. These vascular morphological features correlated strongly with Aß deposits. At sites of microhemorrhage, Aß was consistently present, although the morphology of the deposits changed from the typical organized ring shape to sharply contoured shards with marked dilation of the vessel. AFM showed that arteriolar walls with CAA were more than 400% stiffer than those without CAA. Finally, we characterized the association of vascular degeneration with LOX, finding strong associations with VSM loss and vascular degeneration. These results show an association between vascular Aß deposition, microvascular degeneration, and increased vascular stiffness, likely due to the combined effects of replacement of VSM by ß-amyloid, cross-linking of extracellular matrices (ECM) by LOX, and possibly fibrosis. This advanced microscopic imaging study clarifies the association between Aß deposition and vascular fragility. Restoration of physiologic ECM properties in penetrating arteries may yield a novel therapeutic strategy for CAA.

Fatal iatrogenic cerebral ß-amyloid-related arteritis in a woman treated with lecanemab for Alzheimer's disease.

We report the case of a 79-year-old woman with Alzheimer's disease who participated in a Phase III randomized controlled trial called CLARITY-AD testing the experimental drug lecanemab. She was randomized to the placebo group and subsequently enrolled in an open-label extension which guaranteed she received the active drug. After the third biweekly infusion, she suffered a seizure characterized by speech arrest and a generalized convulsion. Magnetic resonance imaging revealed she had multifocal swelling and a marked increase in the number of cerebral microhemorrhages. She was treated with an antiepileptic regimen and high-dose intravenous corticosteroids but continued to worsen and died after 5 days. Post-mortem MRI confirmed extensive microhemorrhages in the temporal, parietal and occipital lobes. The autopsy confirmed the presence of two copies of APOE4, a gene associated with a higher risk of Alzheimer's disease, and neuropathological features of moderate severity Alzheimer's disease and severe cerebral amyloid angiopathy with perivascular lymphocytic infiltrates, reactive macrophages and fibrinoid degeneration of vessel walls. There were deposits of ß-amyloid in meningeal vessels and penetrating arterioles with numerous microaneurysms. We conclude that the patient likely died as a result of severe cerebral amyloid-related inflammation.

Recurrent TRAK1::RAF1 Fusions in pediatric low-grade gliomas.

Fusions involving CRAF (RAF1) are infrequent oncogenic drivers in pediatric low-grade gliomas, rarely identified in tumors bearing features of pilocytic astrocytoma, and involving a limited number of known fusion partners. We describe recurrent TRAK1::RAF1 fusions, previously unreported in brain tumors, in three pediatric patients with low-grade glial-glioneuronal tumors. We present the associated clinical, histopathologic and molecular features. Patients were all female, aged 8 years, 15 months, and 10 months at diagnosis. All tumors were located in the cerebral hemispheres and predominantly cortical, with leptomeningeal involvement in 2/3 patients. Similar to previously described activating RAF1 fusions, the breakpoints in RAF1 all occurred 5' of the kinase domain, while the breakpoints in the 3' partner preserved the N-terminal kinesin-interacting domain and coiled-coil motifs of TRAK1. Two of the three cases demonstrated methylation profiles (v12.5) compatible with desmoplastic infantile ganglioglioma (DIG)/desmoplastic infantile astrocytoma (DIA) and have remained clinically stable and without disease progression/recurrence after resection. The remaining tumor was non-classifiable; with focal recurrence 14 months after initial resection; the patient remains symptom free and without further recurrence/progression (5 months post re-resection and 19 months from initial diagnosis). Our report expands the landscape of oncogenic RAF1 fusions in pediatric gliomas, which will help to further refine tumor classification and guide management of patients with these alterations.

Detection, visualization and quantification of protein complexes in human Alzheimer's disease brains using proximity ligation assay.

Examination of healthy and diseased human brain is essential to translational neuroscience. Protein-protein interactions play a pivotal role in physiological and pathological processes, but their detection is difficult, especially in aged and fixed human brain tissue. We used the in-situ proximity ligation assay (PLA) to broaden the range of molecular interactions assessable in-situ in the human neuropathology. We adapted fluorescent in-situ PLA to detect ubiquitin-modified proteins in human brains with Alzheimer's disease (AD), including approaches for the management of autofluorescence and quantification using a high-content image analysis system. We confirmed that phosphorylated microtubule-associated protein tau (Serine202, Threonine205) aggregates were modified by ubiquitin and that phospho-tau-ubiquitin complexes were increased in hippocampal and frontal cortex regions in AD compared to non-AD brains. Overall, we refined PLA for use in human neuropathology, which has revealed a profound change in the distribution of ubiquitin in AD brain and its association with characteristic tau pathologies.

Detection, Visualization and Quantification of Protein Complexes in Human Alzheimer's Disease Brains using Proximity Ligation Assay.

Examination of healthy and diseased human brain is essential to translational neuroscience. Protein-protein interactions play a pivotal role in physiological and pathological processes, but their detection is difficult, especially in aged and fixed human brain tissue. We used the proximity ligation assay (PLA) to broaden the range of molecular interactions assessable in-situ in human neuropathology. We adapted fluorescent in-situ PLA to detect ubiquitin-modified proteins in human brains with Alzheimer's disease (AD), including approaches for the management of autofluorescence and quantification using a high-content image analysis system. We confirmed that hyperphosphorylated microtubule-associated protein tau (Serine202, Threonine205) aggregates were modified by ubiquitin and that phospho-tau-ubiquitin complexes were increased in hippocampal and frontal cortex regions in AD compared to non-AD brains. Overall, we refined PLA for use in human neuropathology, which has revealed a profound change in the distribution of ubiquitin in AD brain and its association with characteristic tau pathologies.

Pembrolizumab alters the tumor immune landscape in a patient with dMMR glioblastoma.

Congenital DNA mismatch repair defects (dMMR), such as Lynch Syndrome, predispose patients to a variety of cancers and account for approximately 1% of glioblastoma cases. While few therapeutic options exist for glioblastoma, checkpoint blockade therapy has proven effective in dMMR tumors. Here we present a case study of a male in their 30s diagnosed with dMMR glioblastoma treated with pembrolizumab who experienced a partial response to therapy. Using a multiplex IHC analysis pipeline on archived slide specimens from tumor resections at diagnosis and after therapeutic interventions, we quantified changes in the frequency and spatial distribution of key cell populations in the tumor tissue. Notably, proliferating (KI67+) macrophages and T cells increased in frequency as did other KI67+ cells within the tumor. Therapeutic intervention remodeled the cellular spatial distribution in the tumor leading to a greater frequency of macrophage/tumor cell interactions and T cell/T cell interactions, highlighting impacts of checkpoint blockade on tumor cytoarchitecture and revealing spatial patterns that may indicate advantageous immune interactions in glioma and other solid tumors treated with these agents.

Rodent Model of Brain Radionecrosis Using Clinical LINAC-Based Stereotactic Radiosurgery.

Purpose: Our purpose was to develop a rodent model of brain radionecrosis using clinical linear accelerator based stereotactic radiosurgery. Methods and Materials: Single fraction maximum prescription points in the mouse's left hemisphere were irradiated using linear accelerator-based stereotactic radiosurgery with multiple arcs at 60 (n = 5), 100 (n = 5), and 140 (n = 5) Gy. Rats (n = 6) were similarly treated with 140 Gy. Gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) was used to track radiation injury in mice over weeks (100 and 140 Gy) or months (60 Gy). Target accuracy was measured by the distance from the prescription point to the center of the earliest Gd-MRI enhancement. Confirmation of necrosis via histology was performed at the subject endpoints. Results: Radiation injury as indicated by Gd-MRI was first identified at 2 weeks (140 Gy), 4 to 6 weeks (100 Gy), and 8 months (60 Gy). A volumetric time course showed rapid growth in the volume of Gd-MRI signal enhancement after the appearance of apparent necrosis. Histopathologic features were consistent with radionecrosis. Conclusions: The presented method uses a commonly available clinical linear accelerator to induce radiation necrosis in both mice and rats. The treatment is modeled after patient therapy for a more direct model of human tissue under a range of doses used in clinical neuro-ablation techniques. The short time to onset of apparent necrosis, accurate targeting of the prescription point, high incidence of necrosis, and similar pathologic features make this a suitable animal model for further research in radionecrosis.

Selective Cell Size MRI Differentiates Brain Tumors from Radiation Necrosis.

Brain metastasis is a common characteristic of late-stage lung cancers. High doses of targeted radiotherapy can control tumor growth in the brain but can also result in radiotherapy-induced necrosis. Current methods are limited for distinguishing whether new parenchymal lesions following radiotherapy are recurrent tumors or radiotherapy-induced necrosis, but the clinical management of these two classes of lesions differs significantly. Here, we developed, validated, and evaluated a new MRI technique termed selective size imaging using filters via diffusion times (SSIFT) to differentiate brain tumors from radiotherapy necrosis in the brain. This approach generates a signal filter that leverages diffusion time dependence to establish a cell size-weighted map. Computer simulations in silico, cultured cancer cells in vitro, and animals with brain tumors in vivo were used to comprehensively validate the specificity of SSIFT for detecting typical large cancer cells and the ability to differentiate brain tumors from radiotherapy necrosis. SSIFT was also implemented in patients with metastatic brain cancer and radiotherapy necrosis. SSIFT showed high correlation with mean cell sizes in the relevant range of less than 20 µm. The specificity of SSIFT for brain tumors and reduced contrast in other brain etiologies allowed SSIFT to differentiate brain tumors from peritumoral edema and radiotherapy necrosis. In conclusion, this new, cell size-based MRI method provides a unique contrast to differentiate brain tumors from other pathologies in the brain. SIGNIFICANCE: This work introduces and provides preclinical validation of a new diffusion MRI method that exploits intrinsic differences in cell sizes to distinguish brain tumors and radiotherapy necrosis.

Dural Marginal Zone Lymphoma in a Patient With a Hepatitis C Virus Infection.

Primary dural marginal zone lymphomas (MZLs) are exceptionally rare, with fewer than 100 cases reported to date. While the association between hepatitis C virus (HCV) infection and lymphoma is well established, it is unclear if this association extends to all anatomic sites. Here we report a case of dural MZL in a 61-year-old woman with an HCV infection. To our knowledge, this is the first report of a dural MZL associated with an HCV infection in an immunocompetent patient and was successfully treated with radiotherapy and rituximab. As such, future cases of primary MZL found in the dura should prompt consideration of co-infection with microbials such as HCV and upfront treatment with anti-virals should be considered.

Cerebral aquaporin-4 expression is independent of seizures in tuberous sclerosis complex.

Astrocytes serve many functions in the human brain, many of which focus on maintenance of homeostasis. Astrocyte dysfunction in Tuberous Sclerosis Complex (TSC) has long been appreciated with activation of the mTORC1 signaling pathway resulting in gliosis and possibly contributing to the very frequent phenotype of epilepsy. We hypothesized that aberrant expression of the astrocyte protein aquaporin-4 (AQP4) may be present in TSC and contribute to disease pathology. Characterization of AQP4 expression in epileptic cortex from TSC patients demonstrated a diffuse increase in AQP4. To determine if this was due to exposure to seizures, we examined Aqp4 expression in mouse models of TSC in which Tsc1 or Tsc2 inactivation was targeted to astrocytes or glial progenitors, respectively. Loss of either Tsc1 or Tsc2 from astrocytes resulted in a marked increase in Aqp4 expression which was sensitive to mTORC1 inhibition with rapamycin. Our findings in both TSC epileptogenic cortex and in a variety of astrocyte culture models demonstrate for the first time that AQP4 expression is dysregulated in TSC. The extent to which AQP4 contributes to epilepsy in TSC is not known, though the similarities in AQP4 expression between TSC and temporal lobe epilepsy supports further studies targeting AQP4 in TSC.

Angiocentric glioma mimicking encephalomalacia.

Angiocentric glioma is a rare low-grade neoplasm of the central nervous system which typically presents with medication-refractory seizures in children and young adults. On magnetic resonance imaging, angiocentric glioma is classically T1 hypointense and T2/FLAIR hyperintense. We present the case of a 40-year-old male who had been followed by our institution for 17 years for management of epilepsy. Initial and repeat brain imaging showed an apparent region of cystic encephalomalacia in the right frontal lobe. In an attempt to control his seizures, the lesion was resected. Grossly, the cut surface of the specimen was characterized by multiple small cystic spaces. Microscopically, the lesion was composed of an infiltrative population of glial cells variably arranged in perivascular "pseudorosettes," nodules, and subpial "palisades." The final diagnosis was angiocentric glioma. This is the second reported case of an angiocentric glioma mistaken for encephalomalacia.

A Case of Cushing's Syndrome due to Ectopic Adrenocorticotropic Hormone Secretion from Esthesioneuroblastoma with Long Term Follow-Up after Resection.

We present a case of a 52-year-old male who developed Cushing's Syndrome due to ectopic adrenocorticotrophic hormone (ACTH) secretion from a large esthesioneuroblastoma (ENB) of the nasal sinuses. The patient initially presented with polyuria, polydipsia, weakness, and confusion. Computed tomography scan of the head and magnetic resonance imaging showed a 7 cm skull base mass centered in the right cribriform plate without sella involvement. Work-up revealed ACTH-dependent hypercortisolemia, which did not suppress appropriately after high-dose dexamethasone. Subsequent imaging of the chest, abdomen, and pelvis did not reveal other possible ectopic sources of ACTH secretion besides the ENB. His hospital course was complicated by severe hypokalemia and hyperglycemia before successful surgical resection of the tumor, the biopsy of which showed ENB. Postoperatively, his ACTH level dropped below the limit of detection. In the ensuing 4 months, he underwent adjuvant chemoradiation with carboplatin and docetaxel with good response and resolution of hypokalemia and hyperglycemia, with no sign of recurrence as of 30 months postoperatively. His endogenous cortisol production is rising but has not completely recovered.