Canadian Association of Radiologists Journal

The pterygopalatine fossa is an important anatomic crossroads that is connected with numerous intra- and extracranial spaces via foramina and fissures. Although this fossa is small, its central location in the skull base and its communications provide clinical, radiological, and anatomical significance. In this pictorial review, we aimed to describe the radiologic anatomy of the pterygopalatine fossa, as well as to give some pathologic examples to better understand this major conduit.

Diffusion-weighted imaging provides image contrast that is different from that provided by conventional magnetic resonance imaging techniques. It is highly sensitive for detection of cytotoxic oedema, and as such has gained favor in the detection of acute infarcts. However, diffusion-weighted imaging is underrepresented in the characterisation of many other disease processes. Our objective is to differentiate diseases that manifest with various neurological disorders, based on diffusion contrast and apparent diffusion coefficient values and review of hyper- and hypointense lesions on diffusion-weighted imaging.

Radiologists may be the first to suggest the diagnosis of posterior reversible encephalopathy syndrome (PRES). PRES is associated with many diverse clinical entities, the most common of which are eclampsia, hypertension, and immunosuppressive treatment. Radiologists should be aware of the spectrum of imaging findings in PRES. When promptly recognized and treated, the symptoms and radiological abnormalities can be completely reversed. When unrecognized, patients can progress to ischemia, massive infarction, and death. In this review, we present an overview of the unique signs observed on computed tomography and magnetic resonance images in PRES that can help in the early diagnosis and treatment that is highly effective in this syndrome.

Stroke is the second leading cause of mortality and the third leading cause of disability-adjusted life-years worldwide. For each minute of an ischemic stroke, an estimated 1.9 million brain cells die. The year 2015 saw the unprecedented publication of 5 multicentre, randomized, controlled trials. These studies showed that patients with acute ischemic stroke caused by large-vessel thrombus occlusion of the proximal anterior circulation had significantly reduced disability at 90 days when treated with endovascular thrombectomy and usual stroke care compared to usual stroke care alone. As a result, endovascular thrombectomy is now the new North American and European standard of care for suitable patients with acute ischemic stroke caused by large-vessel proximal anterior circulation occlusion. We review key take-home messages in this paradigm shift for radiologists, including the importance of time and workflow efficiency, what currently constitutes appropriate preimaging patient selection and imaging criteria, the use of newer generation thrombectomy devices, safety outcomes, as well as further areas still in need of elucidation.

The increasing prevalence of tuberculosis in both immunocompetent and immunocompromised individuals in recent years makes the disease a topic of universal concern. It has insidious onset and can affect virtually any organ system in the body, including the central nervous system (CNS). CNS tuberculosis (TB) is becoming more and more complex and atypical with onset of multidrug-resistant TB. Routine diagnostic techniques using serology and body tissue are time consuming and may delay the definitive management. Hence, it is important to be familiar with various radiologic features of CNS TB to ensure early and accurate diagnosis, thereby reducing high morbidity and mortality associated with the disease. The newer imaging techniques further help to improve the characterization and diagnosis of atypical CNS TB. The authors review the imaging characteristics of different forms of CNS tuberculosis involving the brain and spine and discuss the role of advanced imaging modalities in differentiating CNS TB from other disease process.

The management of low back pain should always start with a conservative approach; however, when it fails, intervention is required and at that moment the most appropriate choice remains unclear. Before invasive surgery, minimally invasive techniques can be adopted. In European trials and in a trans-Canadian clinical trial 03 ozone has been used successfully. In total over 50,000 patients have been treated safely. Ozone is a gas normally present in the atmosphere with potent oxidizing power; it has been used for percutaneous intradiscal injection combined with oxygen (O₂O₃) at very low concentrations for 15 years in Europe. The main indication is back pain with or without radicular pain but without motor deficits, which is refractory to 4-6 weeks of conservative therapies. Its mechanism of action on the disc is mechanical (volume reduction by subtle dehydration of the nucleus pulposis) and antinflammatory. The intradiscal ozone injection is performed with a thin needle (18-22 gauge) image guided by computed tomography or angiofluoroscopy and is usually complimented by periganglionic injection of corticosteroids and anesthetics. This combination gives immediate pain relief and allows time for the ozone to act. It is a cost-effective procedure that presents a very low complication rate (0.1%). The radicular pain is resolved before the back pain does, as is seen with microdiscectomy. Peer-reviewed publications of large randomized trials, case series, and meta analysis from large samples of patients have demonstrated the procedure to be safe and effective in the short and the long terms, with benefits recognized up to 10 years after treatment. We aim to review the principles of action of O₂O₃ and report the injection techniques, complications, and short- and long-term outcomes.

The interaction between fungi and the sinonasal tract results in a range of clinical presentations with a broad spectrum of clinical severity. The most commonly accepted classification system divides fungal rhinosinusitis into invasive and noninvasive subtypes based on histopathological evidence of tissue invasion by fungi. Invasive fungal rhinosinusitis is subdivided into acute invasive and chronic invasive categories. The chronic invasive category includes a subcategory of chronic granulomatous disease. Noninvasive fungal disease includes localized fungal colonization, fungal ball, and allergic fungal rhinosinusitis. Noninvasive disease is simply fungal material (or the products of the inflammatory reaction of the sinus mucosa) that fills the sinuses but does not invade tissue. Bone loss is related to expansion of the sinus(es). Invasive disease causes tissue destruction, such that it expands past the bony confines of the sinuses. It can rapidly spread, causing acute necrosis. Alternatively, there may be slow tissue invasion characterized by symptoms confused with normal sinusitis, but destruction of normal nasal and paranasal structures.

Imaging techniques frequently employ contrast agents to improve image resolution and enhance pathology detection. These gadolinium- and iodine-based media, although generally considered safe, are associated with a number of adverse effects ranging from mild to severe. Reactions are classified as either anaphylactoid (“anaphylaxis-like”) or nonanaphylactoid, depending on a number of elements that will be reviewed. Herein, we have summarized predisposing risk factors for adverse events resulting from the use of contrast, their associated pathophysiological mechanisms as well as known prophylaxis for the antitreatment of high-risk patients. In the unlikely event that a serious adverse reaction does occur, we have provided a comprehensive summary of treatment protocols. Our goal was to thoroughly evaluate the current literature regarding adverse reactions to radiocontrast agents and provide an up to date review for the health care provider.