Differentiation and characterization of healthy versus pathological tau using chemical exchange saturation transfer.

Neurofibrillary tangles of tau constitute one of the key biological hallmarks of Alzheimer's disease. Currently, the assessment of regional tau accumulation requires intravenous administration of radioactive tracers for PET imaging. A noninvasive MRI-based solution would have significant clinical implications. Herein, we utilized an MRI technique known as chemical exchange saturation transfer (CEST) to determine the imaging signature of tau in both its monomeric and pathologic fibrillated conformations. Three sets of purified recombinant full-length (4R) tau protein were prepared for collection of CEST spectra using a 9.4 T NMR spectrometer at varying temperatures (25, 37, and 42 °C) and RF intensities (0.7, 1.0, 1.5, and 2.2 µT). Monomeric and fibrillated tau were readily distinguished based on their Z-spectrum profiles. Fibrillated tau demonstrated a less prominent peak at 3.5 ppm with additional peaks near 0.5 and 1.5 ppm. No significant differences were identified between fibrillated tau prepared using heparin versus seed-competent tau. In conclusion, monomeric and fibrillated tau can be readily detected and distinguished based on their CEST-derived Z-spectra, pointing to the potential utility of CEST-MRI as a noninvasive biomarker of regional pathologic tau accumulation in the brain. Further testing and validation in vitro and in vivo will be necessary before this can be applied clinically.

Imaging Guide to Inner Ear Malformations: An Illustrative Review.

Inner ear malformation (IEM) with associated sensoryneural hearing loss (SNHL) is a major cause of childhood disability. Computed tomography (CT) and magnetic resonance imaging (MRI) imaging play important and often complementary roles in diagnosing underlying structural abnormalities and surgical planning allows for direct visualization of the cochlear nerve and is the preferred imaging modality prior to cochlear implantation. CT is helpful to assess osseous anatomy and when evaluating children with mixed hearing loss or syndromic associations. When reviewing these cases, it is important for the radiologist to be familiar with the key imaging features. In this article, we will present the imaging findings associated with different inner ear malformations associated with congenital sensorineural hearing loss.

Brain on fire: an imaging-based review of autoimmune encephalitis.

Autoimmune encephalitis represents an increasingly recognized group of immune-mediated disorders the affect the central nervous system. The purpose of this article is to highlight the characteristic MR imaging findings associated with autoimmune encephalitis, describe the pathophysiology, review antibodies that have been identified and their patterns of CNS involvement, and discuss approaches to management. Familiarity with the imaging and clinical features of autoimmune encephalitis will prompt the radiologist to suggest the diagnosis which can facilitate appropriate management.

Rapid simultaneous acquisition of macromolecular tissue volume, susceptibility, and relaxometry maps.

PURPOSE: A major obstacle to the clinical implementation of quantitative MR is the lengthy acquisition time required to derive multi-contrast parametric maps. We sought to reduce the acquisition time for QSM and macromolecular tissue volume by acquiring both contrasts simultaneously by leveraging their redundancies. The joint virtual coil concept with GRAPPA (JVC-GRAPPA) was applied to reduce acquisition time further. METHODS: Three adult volunteers were imaged on a 3 Tesla scanner using a multi-echo 3D GRE sequence acquired at 3 head orientations. Macromolecular tissue volume, QSM, R2∗ , T1 , and proton density maps were reconstructed. The same sequence (GRAPPA R = 4) was performed in subject 1 with a single head orientation for comparison. Fully sampled data was acquired in subject 2, from which retrospective undersampling was performed (R = 6 GRAPPA and R = 9 JVC-GRAPPA). Prospective undersampling was performed in subject 3 (R = 6 GRAPPA and R = 9 JVC-GRAPPA) using gradient blips to shift k-space sampling in later echoes. RESULTS: Subject 1's multi-orientation and single-orientation macromolecular tissue volume maps were not significantly different based on RMSE. For subject 2, the retrospectively undersampled JVC-GRAPPA and GRAPPA generated similar results as fully sampled data. This approach was validated with the prospectively undersampled images in subject 3. Using QSM, R2∗ , and macromolecular tissue volume, the contributions of myelin and iron content to susceptibility were estimated. CONCLUSION: We have developed a novel strategy to simultaneously acquire data for the reconstruction of 5 intrinsically coregistered 1-mm isotropic resolution multi-parametric maps, with a scan time of 6 min using JVC-GRAPPA.

Uremic Leontiasis Ossea.

While renal osteodystrophy is a common complication of chronic renal failure which is caused by secondary hyperparathyroidism, it is rare that the bony changes result in a severe progressive overgrowth of the bones of the face such that the patient is at risk for breathing and feeding difficulties. When this occurs, it is called uremic leontiasis ossea and patients who suffer from this rare, severe complication of renal osteodystrophy may go undiagnosed or be misdiagnosed resulting improper management due to its limited discussion in the literature. We report a case of a 42-year-old man with end-stage renal disease who was unable to receive dialysis consistently for many years who was found to have a large hard mass on the palate and palate ulcers.

Predicting Parkinson's disease trajectory using clinical and neuroimaging baseline measures.

INTRODUCTION: Predictive biomarkers of Parkinson's Disease progression are needed to expedite neuroprotective treatment development and facilitate prognoses for patients. This work uses measures derived from resting-state functional magnetic resonance imaging, including regional homogeneity (ReHo) and fractional amplitude of low frequency fluctuations (fALFF), to predict an individual's current and future severity over up to 4 years and to elucidate the most prognostic brain regions. METHODS: ReHo and fALFF are measured for 82 Parkinson's Disease subjects and used to train machine learning predictors of baseline clinical and future severity at 1 year, 2 years, and 4 years follow-up as measured by the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS). Predictive performance is measured with nested cross-validation, validated on an external dataset, and again validated through leave-one-site-out cross-validation. Important predictive features are identified. RESULTS: The models explain up to 30.4% of the variance in current MDS-UPDRS scores, 55.8% of the variance in year 1 scores, and 47.1% of the variance in year 2 scores (p < 0.0001). For distinguishing high and low-severity individuals at each timepoint (MDS-UPDRS score above or below the median, respectively), the models achieve positive predictive values up to 79% and negative predictive values up to 80%. Higher ReHo and fALFF in several regions, including components of the default motor network, predicted lower severity across current and future timepoints. CONCLUSION: These results identify an accurate prognostic neuroimaging biomarker which may be used to better inform enrollment in trials of neuroprotective treatments and enable physicians to counsel their patients.

A case of astroblastoma: Radiological and histopathological characteristics and a review of current treatment options.

BACKGROUND: Astroblastoma is a rare neuroepithelial tumor that often originates in the cerebral hemisphere of children and young adults. Diagnosis of this obscure neoplasm can be difficult because these tumors are so infrequently encountered and share common radiological and neuropathological features of other glial neoplasms. As such, it should be included in the differential diagnosis of astrocytoma and ependymoma if the clinical and radiographic features suggest it. Standardized treatment of astroblastomas remains under dispute because of the lack of knowledge regarding the tumor and a paucity of studies in the literature. CASE DESCRIPTION: We present a case of a low-grade astroblastoma diagnosed in a 30-year-old female with seizures, headache, and vision changes. She underwent gross total resection and, without evidence of high-grade features, adjuvant therapy was not planned postoperatively. Post-operative surveillance suggested early recurrence, warranting referral to radiation therapy. Patient ended up expiring despite adjuvant therapy secondary to extensive recurrence and tumor metastasis. CONCLUSIONS: Astroblastoma must be considered in the differential of supratentorial tumors in children and young adults. Treatment of such, as suggested by most recent literature, includes gross total resection and adjuvant radiotherapy for lesions exhibiting high-grade features.