Teaching Points:There are several characteristic features of meningiomas on MRI that allow an accurate diagnosisSome meningiomas may display atypical imaging characteristics that may be diagnostically challengingRoutine MRI sequences do not reliably distinguish between benign and malignant meningiomasSpectroscopy and diffusion tensor imaging may be useful in the diagnosis of malignant meningiomasA number of conditions may mimic meningiomas; however, they may have additional differentiating features

The role of dopamine D1 and D2 receptors in modulating object working memory in humans is poorly understood. The current study was designed to investigate the effects of D1 and D2 receptor modulation on object working memory. Twelve healthy subjects underwent testing under three conditions (0.05 mg pergolide (D1/D2 receptor agonist), 2.5 mg bromocriptine (D2 receptor agonist) and placebo] in a double-blind, placebo-controlled repeated measures design. Subjects performed the object working memory N-back task pre-drug and 1.5 h and 3 h post-drug administration. Neither pergolide nor bromocriptine had an effect on object working memory performance. These findings suggest that object working memory may not be modulated by D1 and D2 receptors in humans.

Neuroradiological functional imaging techniques demonstrate the patterns of hypoperfusion and hypometabolism that are thought to be useful in the differential diagnosis of Alzheimer's disease (AD) from other dementing disorders. Besides the distribution patterns of perfusion or energy metabolism, vascular transit time (VTT), vascular reactivity (VR), and oxygen extraction fraction (OEF), which can be measured with positron emission tomography (PET), provide hemodynamic aspects of brain pathophysiology. In order to evaluate the hemodynamic features of AD, PET studies were carried out in 20 patients with probable AD and 20 patients with vascular dementia (VaD). The PET findings were not included in their diagnostic process of AD. Using oxygen-15-labeled compounds, cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO(2)), OEF, cerebral blood volume, and VTT were measured quantitatively during resting state. To evaluate VR, CBF was also measured during CO(2) inhalation. There was a significant increase in OEF in and around the parietotemporal cortices, but both VTT and VR were well preserved in patients with AD. By contrast, VR was markedly depressed and VTT was mildly prolonged in patients with VaD. Thus, from the hemodynamic point of view, the preservation of vascular reserve may be a distinct difference between AD and VaD. Furthermore, this indicates a hemodynamic integrity of the vasculature in the level of arterioles in AD.

SummaryMagnetic resonance imaging (MRI) is the modality of choice for the investigation of intramedullary lesions of the spinal cord. A wide variety of conditions may result in similar imaging findings on MRI, and it is essential that the reporting radiologist have a detailed understanding of spinal cord anatomy, the pertinent imaging features of specific intramedullary lesions and the typical clinical presentation of those conditions to aid clinicians to make a prompt diagnosis. This pictorial essay discusses the clinical features and MRI appearance of a number of intramedullary conditions, which can be broadly categorised as congenital, demyelinating, vascular, neoplastic or infectious, and highlights their differentiating features.

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