Imaging of fungal, viral, and parasitic musculoskeletal and spinal diseases

Infection

Musculoskeletal infection can be an urgent or emergent clinical issue. Accurate imaging diagnosis is an essential part of the treatment algorithm. This review addresses advantages of available imaging modalities and radiologic appearance of the various manifestations of infection. Controversies are addressed, including the use of the term “osteitis.” Finally, the differential diagnosis of infection is reviewed, such as inflammatory arthropathies and tumors that can simulate infection on imaging exams.

Viral arthritides

Viral infections may manifest as acute or chronic arthritis. Joint involvement arises from either direct infection of the joint, through an immunological response directed towards the virus or autoimmunity. Epidemiological clues to the diagnosis include geographic location and exposure to vector-borne, blood-borne or sexually transmitted viruses. Although not always possible, it is important to diagnose the pathogenic virus, usually by serology, nucleic acid tests or rarely, viral culture. In general, viral arthritides are self-limiting and treatment is targeted at symptomatic relief. This article focuses on the causes, clinical features, diagnosis and treatment of viral arthritides.

Epidemiology of vertebral osteomyelitis (VO) in France: analysis of hospital-discharge data 2002-2003

Vertebral osteomyelitis (VO) is a rare event. To estimate the incidence of VO in France for 2002-2003, national hospital-discharge data were used. Hospital stays were categorized as definite, probable or possible VO. Unique patient identification numbers allowed the investigators to link patients with multiple hospital stays and to analyse data for individual patients. A sample of medical records was reviewed to assess the specificity of the VO case definition. In 2002-2003, 1977 and 2036 hospital stays corresponding to 1422 and 1425 patients (median age 59 years, male:female ratio 1.5) were classified as definite (64%), probable (24%) and possible (12%) VO. The overall incidence of VO was 2.4/100,000. Incidence increased with age: 0.3/100,000 (70 years). The main infectious agents reported were Staphylococcus spp. (38%) and Mycobacterium tuberculosis (31%). The most frequent comorbidities were septicaemia (27%) and endocarditis (9%). Three percent of patients died. A review of 90 medical records confirmed the diagnosis of VO in 94% of cases. Using a hospital database and a specific case definition, nationwide surveillance of VO is possible.

Magnetic Resonance Imaging of Appendicular Musculoskeletal Infection

Appendicular skeletal infection includes osseous and extraosseous infections. Skeletal infection needs early diagnosis and appropriate management to prevent long-term morbidity. Magnetic resonance imaging is the best imaging modality to diagnose skeletal infection early in most circumstances. This article describes the role of magnetic resonance imaging in relation to the other available imaging modalities in the diagnosis of skeletal infection. Special circumstances such as diabetic foot, postoperative infection, and chronic recurrent multifocal osteomyelitis are discussed separately.

A compartmental approach to the radiographic evaluation of soft-tissue calcifications

Musculoskeletal radiology, like most areas of diagnostic radiology, has seen a dramatic increase in the use of cross-sectional imaging techniques over the last decade. However, conventional radiography remains a vital role in the evaluation of disease involving the spine and extremities. Given its widespread availability and low cost, radiography should be the initial examination obtained when imaging is clinically indicated. Therefore it is essential that the practicing radiologists be able to maximize the diagnostic value of this common study to aid the clinicians with a focused differential diagnosis, if not a definitive diagnosis. While much emphasis has been placed on radiographic interpretation of osseous lesions, similar diagnostic yield can be often obtained about calcified or ossified soft-tissue lesions. Detailed evaluation of the distribution and morphology of the soft-tissue calcifications, combined with a thorough knowledge of the entities that may occur at the site of the noted abnormality, provides significant interpretive value to provide a definitive diagnosis or accurately recommend the next most effective management step. We provide a compartmental-based approach to the interpretation of soft-tissue calcifications.

Spinal infections

Spinal infections can be thought of as a spectrum of disease comprising spondylitis, discitis, spondylodiscitis, pyogenic facet arthropathy, epidural infections, meningitis, polyradiculopathy and myelitis. Radiological evaluations have gained importance in the diagnosis, treatment planning, treatment and treatment monitoring of the spinal infections. Conventional radiographs are usually the initial imaging study. The sensitivity and specificity of the plain radiographs are very low. The sensitivity of CT is higher while it lacks of specificity. Conventional CT has played minor role for the diagnosis of early spondylitis and disc space infection and for follow-up, researches are going on the value of MDCT. MRI is as sensitive, specific and accurate as combined nuclear medicine studies and the method of choice for the spondylitis. Low signal areas of the vertebral body, loss of definition of the end plates and interruption of the cortical continuity, destruction of the cortical margins are typical on T1WI whereas high signal of affected areas of the vertebral body and disc is typical on T2WI. Contrast is mandatory and increases conspicuity, specificity, and observer confidence in the diagnosis and facilitates the treatment planning. Contrast enhancement is the earliest sign and pathognomonic in the acute inflammatory episode and even in the subtle infection then persists to a varying degree for several weeks or months. The outcome of the treatment is influenced by the type of infection and by the degree of neurologic compromise before treatment. There is an increasing move away from surgical intervention towards conservative therapy, percutaneous drainage of abscess or both. It is therefore critical to monitor treatment response, particularly in the immuno-deficient population.

MR imaging of spinal infection: atypical features, interpretative pitfalls and potential mimickers

The wide variability of MR features in spinal infection reflects rare distribution of discovertebral involvement, unexpected soft-tissue and bone abnormalities, un-usual complications or uncommon pathogens. In addition, several de-generative and inflammatory entities can clinically and radiologically resemble spinal infection. In this pictorial review, we illustrate the various atypical features that may be found in MR imaging of spinal infection,with emphasis on interpretative pit-falls and common mimickers.