Jeevak Almast

Border Zone Infarcts: Pathophysiologic and Imaging Characteristics

Border zone or watershed infarcts are ischemic lesions that occur in characteristic locations at the junction between two main arterial territories. These lesions constitute approximately 10% of all brain infarcts and are well described in the literature. Their pathophysiology has not yet been fully elucidated, but a commonly accepted hypothesis holds that decreased perfusion in the distal regions of the vascular territories leaves them vulnerable to infarction. Two types of border zone infarcts are recognized: external (cortical) and internal (subcortical). To select the most appropriate methods for managing these infarcts, it is important to understand the underlying causal mechanisms. Internal border zone infarcts are caused mainly by hemodynamic compromise, whereas external border zone infarcts are believed to result from embolism but not always with associated hypoperfusion. Various imaging modalities have been used to determine the presence and extent of hemodynamic compromise or misery perfusion in association with border zone infarcts, and some findings (eg, multiple small internal infarcts) have proved to be independent predictors of subsequent ischemic stroke. A combination of several advanced techniques (eg, diffusion and perfusion magnetic resonance imaging and computed tomography, positron emission tomography, transcranial Doppler ultrasonography) can be useful for identifying the pathophysiologic process, making an early clinical diagnosis, guiding management, and predicting the outcome.

Percentage Signal Recovery Derived from MR Dynamic Susceptibility Contrast Imaging Is Useful to Differentiate Common Enhancing Malignant Lesions of the Brain

BACKGROUND AND PURPOSE: Differentiation of enhancing malignant lesions on conventional MR imaging can be difficult and various newer imaging techniques have been suggested. Our aim was to evaluate the role of PSR obtained from DSC perfusion measurements in differentiating lymphoma, GBM, and metastases. The effectiveness of PSR was compared with that of rCBV. We hypothesized that the newly defined parameter of PSR is more sensitive and specific in differentiating these lesions. MATERIALS AND METHODS: This retrospective study included 66 patients (39 men and 27 women; age range: 27–82 years) with a pathologically proved diagnosis of primary CNS lymphoma, GBM, or metastases (22 patients in each group). Mean PSR, min PSR, max PSR, and rCBV were calculated. The classification accuracy of these parameters was investigated by using ROC. RESULTS: Mean PSR was high (113.15 ± 41.59) in lymphoma, intermediate in GBM (78.22 ± 14.27), and low in metastases (53.46 ± 12.87) with a P value < .000. F values obtained from 1-way ANOVA analysis for mean, min, and max PSR ratios were 29.9, 39.4, and 23.4, respectively, which were better than those of rCBV (11.1) in differentiating the 3 groups. Max PSR yielded the best ROC characteristics with an Az of 0.934 (95% CI, 0.877–0.99) in differentiating lymphoma from metastases and GBM. The Az for mean and min PSR of 0.938 (95% CI, 0.0.884–0.990) and 0.938 (95% CI, 0.884–0.991), respectively, was better than rCBV (Az, 0.534; 95% CI, 0.391–0.676) in the differentiation of metastases from GBM and lymphoma (P ≤ .0001). CONCLUSIONS: PSR appears to be a parameter that helps in differentiating intracerebral malignant lesions such as GBM, metastases, and lymphoma.

Magnetic resonance imaging of neurosarcoidosis.

Neurosarcoidosis is an uncommon condition with protean manifestations. Magnetic resonance imaging (MRI) is often used in the diagnostic evaluation and follow-up of patients with neurosarcoidosis. Therefore, familiarity with the variety of MRI appearances is important. In this pictorial essay, the range of possible patterns of involvement in neurosarcoidosis are depicted and discussed. These include intracranial and spine leptomeningeal involvement, cortical and cerebral white matter lesions, corpus callosum involvement, sellar and suprasellar involvement, periventricular involvement, cranial nerve involvement, cavernous sinus involvement, hydrocephalus, dural involvement, ischemic lesions, perivascular involvement, orbit lesions, osseous involvement, nerve root involvement, and spinal cord intramedullary involvement. Differential diagnoses for each pattern of involvement of neurosarcoidosis are also provided.

Your Brain on Drugs: Imaging of Drug-related Changes in the Central Nervous System

Drug abuse is a substantial problem in society today and is associated with significant morbidity and mortality. Various drugs are associated with serious complications affecting the brain, and it is critical to recognize the imaging findings of these complications to provide prompt medical management. The central nervous system (CNS) is a target organ for drugs of abuse as well as specific prescribed medications. Drugs of abuse affecting the CNS include cocaine, heroin, alcohol, amphetamines, toluene, and cannabis. Prescribed medications or medical therapies that can affect the CNS include immunosuppressants, antiepileptics, nitrous oxide, and total parenteral nutrition. The CNS complications of these drugs include neurovascular complications, encephalopathy, atrophy, infection, changes in the corpus callosum, and other miscellaneous changes. Imaging abnormalities indicative of these complications can be appreciated at both magnetic resonance (MR) imaging and computed tomography (CT). It is critical for radiologists to recognize complications related to drugs of abuse as well as iatrogenic effects of various medications. Therefore, diagnostic imaging modalities such as MR imaging and CT can play a pivotal role in the recognition and timely management of drug-related complications in the CNS.

CT perfusion in acute stroke: Know the mimics, potential pitfalls, artifacts, and technical errors

The CT perfusion (CTP) imaging of brain has been established as a clinically useful tool in multimodality imaging of acute stroke. All abnormalities seen on perfusion CT are not specifically related to acute infarct. There are many neurologic diseases causing symptoms simulating cerebrovascular disease produce an alteration of brain perfusion and thus can result in perfusion CT abnormalities. There are many pitfalls and artifacts in acquiring the data, calculation of maps and choosing arterial input function. We analyze and classify all these aspects, to allow the technician and the radiologist to know exactly what to avoid and what to choose, and we indicate the way to improve the quality of examination. The knowledge of mimics and pitfalls in acute stroke imaging can be helpful in accurate interpretation of these examinations.

Lesions masquerading as acute stroke

Rapid and accurate recognition of lesions masquerading as acute stroke is important. Any incorrect or delayed diagnosis of stroke mimics will not only increase the risk of being exposed to unnecessary and possibly dangerous interventional therapies, but will also delay proper treatment. In this article, written from a neuroradiologists perspective, we classified these lesions masquerading as acute stroke into three groups: lesions that may have “normal imaging,” lesions that are “symptom mimics” but on imaging clearly not a stroke, and lesions that are “symptom and imaging mimics” with imaging findings similar to stroke. We focused the review on neuroimaging findings of the latter two groups ending with a suggestion for a diagnostic approach in the form of an algorithm. J. Magn. Reson. Imaging 2013;37:15–34.

Toxins in Brain! Magnetic Resonance (MR) Imaging of Toxic Leukoencephalopathy – A Pictorial Essay

Summary Toxic leukoencephalopathy results from damage to the white matter caused by various toxins. It manifests itself as white matter signal abnormalities with or without the presence of restricted diffusion. These changes are often reversible if the insulting agent is removed early, with the exception of posthypoxic leukoencephalopathy that can manifest itself 1–2 weeks after the initial insult. However, many other potential causes of white matter signal abnormalities can mimic the changes of toxic leukoencephalopathy. Thus, familiarity with the causes, clinical presentation and particularly imaging findings of toxic leukoencephalopathy is critical for early treatment and improved prognosis. The purpose of this pictorial essay is to familiarize the reader with the various causes of toxic leukoencephalopathy along with its differential diagnoses and mimics.

Magnetic resonance imaging of sellar and juxtasellar abnormalities in the paediatric population: an imaging review

AbstractThe sellar and juxtasellar regions in the paediatric population are complex both anatomically and pathologically, with magnetic resonance imaging (MRI) being the “gold standard” imaging modality due to the high contrast of detail. Assessment requires a detailed understanding of the anatomy, embryology, pathophysiology and normal signal characteristics of the pituitary gland and surrounding structures in order to appropriately characterise abnormalities. This article aims to provide an overview of the imaging characteristics of developmental/congenital and acquired disease processes which affect the sellar and juxtasellar region in the paediatric population.n Main Messagesn • The sellar region is anatomically complex and covers a wide pathology spectrum.n • MRI is the key imaging modality to assess sellar and juxtasellar pathology.n • Numerous developmental anomalies may not be discovered until adulthood.n • Knowledge of pathology alerts and guides the clinician towards appropriate management.

The “pool sign” of metastatic adenocarcinoma

The differential of a newly discovered solitary intracranial mass is a primary intracranial neoplasm and metastatic disease. Differentiating between the two entities on imaging is difficult, though there are clues on conventional imaging that suggest one over the other. The purpose of this article is to describe a new imaging finding on T2-weighted imaging, the “pool sign,” that may be specific for metastatic adenocarcinomas and can help differentiate a solitary metastasis from a primary CNS neoplasm. We present a series of four patients with initial magnetic resonance imaging of a solitary intracranial mass demonstrating the “pool sign,” and therefore predicted to be metastatic adenocarcinoma. All of these cases were confirmed to be metastatic adenocarcinoma on pathology.

Beyond stroke—uncommon causes of diffusion restriction in the basal ganglia

In the emergency setting, a regional area of restricted diffusion involving the basal ganglia typically represents an acute infarct due to small vessel occlusion. However, it is important to consider additional differentials, specifically systemic causes. This article will review anatomy of the basal ganglia and pertinent associated vasculature, followed by other entities that can be a cause of restricted diffusion. These include hemolytic uremic syndrome, hypereosinophilic syndrome, fat embolism, meningitis, and hypoxic-ischemic injury. It is important to recognize presenting findings in these conditions, as the radiologist may be the first to give an accurate diagnosis or prompt additional testing.