TREM2 analysis and increased risk of Alzheimer's disease.

Important insights into the pathogenic mechanism of Alzheimer's disease (AD) have arisen from the identification of genetic risk factors. Recently, a variant in the TREM2 gene (rs75932628), causing a C-to-T base-pair change that results in the substitution of histidine for arginine at amino acid position 47 (R47H) in the TREM2 protein, has been associated with an increased risk of AD. We, therefore, genotyped samples from a cohort of 474 AD patients and 608 healthy controls, from the northwest region of the UK, using allelic discrimination assays, to replicate the results of the previous studies.

Dermoid cyst of the pancreas: a case report with literature review.

Pancreatic dermoid cysts represent a rare entity with 35 cases described in the world literature, including the present one. Pre-operative diagnosis is difficult, with definitive diagnosis usually taking place intra-operatively. We report the case of a 63 year old male with a symptomatic, 6 cm cystic mass in the body of the pancreas.

Phospholipase C-η2 is required for retinoic acid-stimulated neurite growth.

Phospholipase C-η2 is a recently identified phospholipase C (PLC) implicated in the regulation of neuronal differentiation/maturation. PLCη2 activity is triggered by intracellular calcium mobilization and likely serves to amplify Ca²⁺ signals by stimulating further Ca²⁺ release from Ins(1,4,5)P₃-sensitive stores. The role of PLCη2 in neuritogenesis was assessed during retinoic acid (RA)-induced Neuro2A cell differentiation.

MR imaging-related heating of deep brain stimulation electrodes: in vitro study.

Background And Purpose: Recent work has shown a potential for excessive heating of deep brain stimulation electrodes during MR imaging. This in vitro study investigates the relationship between electrode heating and the specific absorption rate (SAR) of several MR images.

Methods: In vitro testing was performed by using a 1.

Neurostimulation systems for deep brain stimulation: in vitro evaluation of magnetic resonance imaging-related heating at 1.5 tesla.

Purpose: To assess magnetic resonance imaging (MRI)-related heating for a neurostimulation system (Activa Tremor Control System, Medtronic, Minneapolis, MN) used for chronic deep brain stimulation (DBS).

Materials And Methods: Different configurations were evaluated for bilateral neurostimulators (Soletra Model 7426), extensions, and leads to assess worst-case and clinically relevant positioning scenarios. In vitro testing was performed using a 1.

MR imaging of intrinsic inflammatory myelopathies.

The neuroimaging evaluation of patients with suspected inflammatory myelopathy is one of the more technically and interpretatively challenging MR examinations. This article reviews several recent MR imaging sequencing developments that have significantly improved spinal cord imaging. The clinical, pathologic, and MR imaging features of several of the more common inflammatory myelopathic-producing diseases also are discussed.

Multifocal varicella-zoster virus leukoencephalitis in a patient with AIDS: MR findings.

We describe a patient with AIDS who presented with an acute encephalitis caused by infection with varicella-zoster virus. The hemorrhagic, necrotizing encephalitis had an unusual MR appearance, with innumerable discrete, small, targetlike lesions in the right cerebral hemisphere, which were coalescent in the posterior temporal, parietal, and occipital regions. Of the several known disease patterns of varicella-zoster viral infection in the CNS, this histopathologic pattern of multifocal leukoencephalitis is rare.

Flip angle dependence of experimentally determined T1sat and apparent magnetization transfer rate constants.

The purpose of this work was to develop a method for determining the T1sat and magnetization transfer (MT) rate constants by analyzing the slice-select flip angle dependent MT behavior of normal white and gray matter. The technique uses a high MT power, three-dimensional (3D) gradient-recalled echo (GRE) sequence, with a well chosen MT pulse frequency offset, such that the experimental conditions closely satisfy requisite assumptions for invoking a first order rate process for MT. Integral to this method is that the T1sat and MT ratio values are obtained under explicitly identical MT saturation conditions.

Magnetization transfer in neuroimaging.

Magnetization transfer (MT) imaging has become a focus of recent basic science and clinical investigations because of its unique physical basis of contrast, and the potential to quantify aspects of the biochemical structure and composition of tissues. In this article, basic theories of MT are discussed, and several practical MT pulse and sequence considerations are addressed. The clinical utility of MT techniques in MR angiography, postgadolinium T1-weighted scanning, and spine scanning are discussed.

T1-weighted three-dimensional magnetization transfer MR of the brain: improved lesion contrast enhancement.

Purpose: We developed and evaluated clinically T1-weighted three-dimensional gradient-echo magnetization transfer (MT) sequences for contrast-enhanced MR imaging of the brain.

Methods: A short-repetition-time, radio frequency-spoiled, 3-D sequence was developed with a 10-millisecond MT pulse at high MT power and narrow MT pulse-frequency offset, and the enhancing lesion-to-normal white matter background (L/B) and the contrast-to-noise (C/N) ratios on these images were compared with those on T1-weighted spin-echo images and on non-MT 3-D gradient-echo images in a prospective study of 45 patients with 62 enhancing lesions. In the 24 patients who had intracranial metastatic disease, the number of lesions was counted and compared on the three types of images.

Ectopic extraspinal meningioma: CT and MR appearance.

We report a case of an ectopic, extraspinal meningioma that appeared as a midline interscapular mass in a 13-year-old girl. The tumor involved the T-2 and T-3 spinous processes, but was dorsal to the lamina and was entirely extrinsic to the spinal canal. Large amounts of tumoral calcification and reactive hyperostosis were present, radiologically mimicking an osteogenic sarcoma.

Analysis of magnetization transfer effects on T1-weighted spin-echo scans using a simple tissue phantom simulating gadolinium-enhanced brain lesions.

The purpose of this study was to analyze the effect of several magnetization transfer (MT) pulse and T1-weighted spin-echo (SE) sequence parameters on lesion-to-background contrast, using a simple tissue phantom emulating the T1 relaxation and MT properties of gadolinium-enhanced brain lesions. Eggbeaters (Nabisco Inc., East Hanover, NJ) liquid egg product was doped with gadolinium in six concentrations from .

Magnetization transfer effects on T1-weighted three-dimensional gradient-echo MR images of a phantom simulating enhancing brain lesions.

Purpose: To develop a simple tissue phantom to study the effects of various imaging parameters and gadolinium concentrations on magnetization transfer (MT) and lesion-to-background ratios.

Methods: A commercial egg product was doped with gadolinium in concentrations of 0.0 to 1.

Cerebral white matter: technical development and clinical applications of effective magnetization transfer (MT) power concepts for high-power, thin-section, quantitative MT examinations.

Purpose: To evaluate white matter disorders with magnetization transfer (MT) techniques.

Materials And Methods: In 46 healthy volunteers and 46 clinical patients, MT Z spectra were obtained with various continuous-wave-equivalent MT powers (B1CW) and frequency offsets.

Results: With B1CW of 270 Hz and 4,000-Hz frequency offset, the MT ratio of normal callosal white matter was 59.

Leptomeningeal and calvarial sarcoidosis: CT and MR appearance.

We report an unusual case of biopsy-proven combined leptomeningeal and calvarial sarcoidosis, as seen on CT and MRI. A solitary large thick plaque was present in the left hemisphere, with overlying bony infiltration and erosion and associated abundant vasogenic edema in the brain. The lytic lesion was visible on Scout digital radiography for CT slice positioning.

Trilateral retinoblastoma: two variations.

Two cases of trilateral retinoblastoma (a syndrome of midline, undifferentiated, intracranial tumor in a child with hereditary, bilateral ocular retinoblastoma) are described, one with a unique location of the intracranial tumor, and the other with an unusual temporal course of disease.

Use of magnetization transfer for improved contrast on gradient-echo MR images of the cervical spine.

Purpose: To evaluate whether magnetization transfer (MT) can improve image contrast on gradient-recalled echo (GRE) magnetic resonance (MR) images of the cervical spine.

Materials And Methods: Sagittal and axial two-dimensional conventional GRE and MT GRE images were obtained in 103 patients with degenerative disk disease or intrinsic cord lesions. The contrast-to-noise ratios (C/Ns) for the cervical spinal cord and cerebrospinal fluid (CSF) were compared for images obtained at various MT power level and section-select flip angle combinations.

Experimental confirmation of phase encoding of instantaneous derivatives of position.

Previous theoretical reports described the dependence of interpretation of the observed phase of the NMR signal on the time origin(s) of moment calculations and position's Taylor series expansion. This work provides experimental confirmation of predictions derived from that theory. For accelerative motion, experimental phase-encoded velocity measurements give instantaneous values at a time corresponding to the origin used for waveform moment calculations.

Improved contrast of enhancing brain lesions on postgadolinium, T1-weighted spin-echo images with use of magnetization transfer.

Purpose: To prove that the contrast of enhancing brain lesions on post-gadolinium T1-weighted spin-echo (SE) images can be statistically significantly improved with magnetization-transfer (MT) indirect saturation.

Materials And Methods: The contrast-to-noise ratios (C/Ns) of 201 enhancing brain lesions in 110 patients were compared on conventional and MT T1-weighted SE images obtained at 1.5 T after injection of 0.

Deceptively normal MR in early infantile Krabbe disease.

The authors present two cases of 5-month-old children with early infantile Krabbe disease studied by CT and MR. Both infants had characteristic CT scans for the disease consisting of symmetric hyperdensity involving the cerebellum, thalami, caudate, corona radiata, and brain stem. One of the infants had a deceptively normal initial MR examination, with dramatic progression of the white-matter disease over the following 4 months.

Varied microcirculation of pituitary adenomas at rapid, dynamic, contrast-enhanced MR imaging.

Purpose: Rapid, dynamic, contrast material-enhanced magnetic resonance imaging was performed to evaluate the early enhancement patterns of normal pituitary structures, macroadenomas, and microadenomas.

Materials And Methods: A 1.5-T imager with a circularly polarized head coil was used on 40 patients referred for investigation of endocrinopathy, of neurologic deficit, or for follow-up of a previously documented pituitary tumor.

Menkes kinky hair disease: characteristic MR angiographic findings.

We report two cases of Menkes kinky hair disease in which MR and MR angiography were performed. The clinical and imaging features are reviewed. MR demonstrated characteristic cerebrovascular tortuousity and thus may be a valuable aid in diagnosis and follow-up.