Arterial Spin Labeling: Techniques, Clinical Applications, and Interpretation.

Arterial spin labeling (ASL) is an emerging noninvasive MRI technique for assessing cerebral perfusion. An important advantage of ASL perfusion is the lack of a requirement for an exogenous tracer. ASL uses magnetically labeled water protons from arterial blood as an endogenous diffusible tracer. For this reason, ASL is an attractive perfusion imaging modality for children and for patients with contraindications or adverse reactions to gadolinium, patients with renal failure, and those who need repeated follow-up imaging. Another advantage of ASL is the possibility of quantifying cerebral blood flow, which provides an opportunity for comparative analysis among multiple longitudinal studies, unlike other MR perfusion techniques, which are semiquantitative and yield relative perfusion parameters. Advances in MRI technology and pulse sequence design have translated ASL beyond the research arena to successful clinical implementation. However, ASL is still underused in routine clinical practice. Some disadvantages of ASL include a lower signal-to-noise ratio and a longer acquisition time than those with dynamic susceptibility contrast-enhanced MRI. Additional factors limiting the use of ASL include variations in existing techniques and pulse sequence design, the complexity of implementation and postprocessing, insufficient experience with and/or knowledge of the potential clinical applications, and the absence of interpretation guidelines. The authors review the technical and physiologic basis of ASL perfusion, as well as artifacts, pitfalls, and its current clinical applications. A practical approach for interpreting ASL findings is also suggested.

Case Report: Evolutionary Clinical-Radiological Features of a Diffuse Hemispheric Glioma, H3 G34 Mutant with Over 5 Years of Survival.

Diffuse hemispheric glioma (DHG), H3 G34 mutant was included in the 5th edition of the World Health Organization Classification of Tumors of the Central Nervous System recently published. Given the recent inclusion in the current classification and its rarity in adult patients, there are scarce data on clinical-radiological characteristics, survival, and outcome. The authors report the case of a 35-year-old female with DHG, H3 G34-mutant characteristics and outcomes with an unusual presentation, recurrence, and prolonged survival. In conclusion, our case report demonstrates relevant details that should be observed in patients with suspicion or confirmation of the diagnosis of DHG, H3 G34 mutant, not only in the initial presentation but also in the evolution to ensure more personalized treatment.

Intracranial vessel wall magnetic resonance imaging features of infectious vasculitis.

Vasculitis is a complication of several infectious diseases affecting the central nervous system, which may result in ischemic and/or hemorrhagic stroke, transient ischemic attack, and aneurysm formation. The infectious agent may directly infect the endothelium, causing vasculitis, or indirectly affect the vessel wall through an immunological mechanism. The clinical manifestations of these complications usually overlap with those of non-infectious vascular diseases, making diagnosis challenging. Intracranial vessel wall magnetic resonance imaging (VWI) enables the evaluation of the vessel wall and the diseases that affect it, providing diagnostic data beyond luminal changes and enabling the identification of inflammatory changes in cerebral vasculitis. This technique demonstrates concentric vessel wall thickening and gadolinium enhancement, associated or not with adjacent brain parenchymal enhancement, in patients with vasculitis of any origin. It permits the detection of early alterations, even before a stenosis occurs. In this article, we review the intracranial vessel wall imaging features of infectious vasculitis of bacterial, viral, and fungal etiologies.

Cervical solitary fibrous tumor: case report and literature review.

Solitary fibrous tumors (SFTs) are rare neoplasms in the spinal canal. There are few studies addressing SFT/hemangiopericytomas with no distinctive clinical characteristics, no conclusive radiological findings or even a well-defined best treatment strategy. We described a rare case of cervical SFT/hemangiopericytomas in a young patient with spinal cord compression. There are many differential diagnoses for spinal dural-based masses of which meningiomas are the most common. Surgeons and oncologists should be aware of differentials of dural-based masses in the spinal cord for surgical decision making and to guide treatment.

Myxoid glioneuronal tumour - report of three cases of a new tumour in a typical location and review of literature.

Formerly called dysembryoplastic neuroepithelial tumour (DNET) of the septum pellucidum, myxoid glioneuronal tumour (MGT) was recently recognized as a distinct entity. We report three cases of presumed MGT with typical location and image features.

Temporal horns subependymomas: A report of two cases of an intraventricular neoplasm in an atypical location.

Slow-growing intraventricular masses are sometimes imaging findings in asymptomatic patients. The neuroimaging characteristics frequently help making the correct diagnosis and the treatment decision. Subependymomas usually present as single lesions poorly vascularized, without invasion into adjacent brain parenchyma or cerebrospinal fluid dissemination. Ependymoma is considered the main differential diagnosis. We report two cases of this tumour who share the unusual location: The temporal horns. The lack of enhancement (or heterogeneous when present) and advanced neuroimaging techniques can be very useful in differentiating them from other lesions.

Neurocysticercosis: evaluation with advanced magnetic resonance techniques and atypical forms.

Neurocysticercosis (NCC) is the most common helminthic infection of the central nervous system, but its diagnosis remains difficult. The purpose of this article is to perform a critical analysis of the literature and show our experience in the evaluation of NCC. We discuss the advanced MR technique applications such as diffusion and perfusion-weighted imaging, spectroscopy, cisternography with FLAIR, and supplemental O2 and 3D-CISS. The typical manifestations of NCC are described; emphasis is given to the unusual presentations. The atypical forms of neurocysticercosis were divided into: intraventricular, subarachnoid, spinal, orbital, and intraparenchymatous. Special attention was also given to reactivation of previously calcified lesions and neurocysticercosis associated with mesial temporal sclerosis.

Imaging aspects of pyogenic infections of the central nervous system.

Although pyogenic infections of the central nervous system are not a frequent group of diseases, their morbidity and mortally are very high. For this reason they require prompt diagnosis and treatment to avoid several complications that can lead to an undesired outcome. In this article, we review the imaging findings of these infections according to the anatomic site, their complications, and their differential diagnosis. Special attention is given to the different techniques of magnetic resonance imaging like perfusion, spectroscopy, and diffusion, for each specific situation such as meningitis, abscess, ventriculitis, purulent extra axial collections, and vascular complications.

Granulomatous diseases of the central nervous system.

Infectious diseases of the central nervous system (CNS), particularly those accompanied by the formation of granulomas, are a constant diagnostic challenge in some specific regions of the world, above all in developing countries. The pattern of image seen on CT or MR scan is the result of the inter-relations between the individual characteristics of the infectious agent and the capacity of each host to mount an appropriate inflammatory response to that specific type of aggression, inside one particular compartment of the CNS. Taking these parameters into account we will discuss the several patterns of image found in parasitic, bacterial, and fungal granulomatous infections.

Parasitic and rare spinal infections.

The imaging features of spinal parasitic diseases and other rare infections are herein discussed. These diseases are distributed worldwide, with increased prevalence in areas with poor sanitary conditions and in developing countries. In nonendemic areas, sporadic cases may occur, consequent to increased international travel and immunocompromising conditions. Infectious diseases are usually treatable, and early detection is often crucial. A thorough comprehension of the imaging patterns associated with the clinical features, epidemiology, and laboratory results allows the radiologist to narrow down the options for differential diagnosis and facilitates the timely implementation of appropriate therapies.