Magnetic resonance imaging of osteoarticular infections in children

Magnetic resonance imaging has become a common tool for the diagnosis and management of osteoarticular infections in children. We retrospectively review the MRI findings in 57 children (age range 4 months to 16 years; mean 6.3 years) diagnosed with osteoarticular infection. Thirty-eight cases were osteomyelitis, 4 were septic arthritis, 6 were spondylodiscitis, 7 were soft-tissue infections, 2 were pyomyositis, and 2 were chronic multifocal osteomyelitis. The pathogenesis and classification of osteoarticular infections are briefly discussed. Currently available imaging techniques are reviewed, and advantages and disadvantages are discussed. Magnetic resonance imaging indications and findings are shown. The most adequate magnetic resonance imaging sequences, as well as the usefulness of intravenous contrast material, are stressed.     

Pyomyositis mimicking osteomyelitis detected by SPET/CT

Pyomyositis is a relatively infrequent, sub-acute primary bacterial muscle infection, which due to its non specific clinical findings is unlikely to be early diagnosed especially in diabetic patients. This diagnostic delay may be fatal. Therefore, early diagnosis and prompt treatment are imperative. We present a poorly-controlled diabetic patient who was referred to our Nuclear Medicine department for a bone scan to evaluate osteomyelitis. Routine three-phase-planar-scintigraphy was falsely positive for osteomyelitis in the left fibula, however, single photon emission tomography (SPET/CT) images clearly showed abnormal uptake in the calf muscles rather than the bone with evidence of low-attenuation lesions in these muscles. SPET/CT and magnetic resonance imaging (MRI) provided essential information to the clinicians to consider other diagnoses rather than osteomyelitis. MRI showed inter and intra-muscular collections consistent with multiple abscesses. Based on medical history, SPET/CT and MRI findings, the diagnosis of pyomyositis was established. The patient underwent successfully multiple incision-drainage procedures with subsequent intravenous antibiotic treatment and was discharged after complete recovery. In conclusion we advocate the use of SPET/CT for the detection of pyomyositis.     

MR imaging findings of pyogenic bacterial myositis (pyomyositis) in patients with local muscle trauma: illustrative cases

Pyogenic myositis (pyomyositis) represents a bacterial infection of muscle, usually caused by Staphylococcus aureus that is endemic in tropical regions. Pyomyositis commonly affects patients who are immunocompromised or who have underlying chronic disorders. Lower extremity localization of infection is typical. The most common pattern of disease, however, appears to be a solitary abscess in the quadriceps musculature. Delay in accurate diagnosis is frequent and clinical deterioration can be precipitous. In view of the high associated morbidity, early imaging to detect, localize, and define disease extent is important. Magnetic resonance imaging (MRI) plays a key role in the definitive diagnosis of pyomyositis. This article provides a pictorial illustration of the spectrum of MRI findings associated with pyogenic myositis.     

MR imaging of urgent inflammatory and infectious conditions affecting the soft tissues of the musculoskeletal system

Soft tissue infections and inflammatory conditions of the musculoskeletal system are a group of disorders commonly seen by emergency room physicians and radiologists. Many of these entities can either be limb- or life-threatening. Magnetic resonance imaging is currently the best imaging modality to evaluate these conditions. In this review, the characteristic imaging findings of cellulitis, abscess formation, necrotizing fasciitis, pyomyositis, diabetic ischemic infarction, acute and exertional compartment syndromes, and rhabdomyolysis will be emphasized as well as imaging factors that can help to differentiate these disorders.     

Imaging of spine infection

This article reviews the imaging and relevant clinical details of infection of the extradural spine. Spine infections are increasing in incidence and in frequency of diagnosis. They are clinically important despite their relative rarity, because they may be life-threatening, and because early diagnosis leads to improved outcomes. The focus is on pyogenic spondylodiscitis. The also typically pyogenic conditions of epidural and subdural abscess, facet joint infection, and pyomyositis are discussed. Nonpyogenic, granulomatous infections are also addressed. Magnetic resonance imaging is emphasized. The radiologist's role in performing minimally invasive sampling procedures is highlighted.     

Atypical extraspinal musculoskeletal tuberculosis in immunocompetent patients: part II, tuberculous myositis, tuberculous bursitis, and tuberculous tenosynovites.

Tuberculosis involving the soft tissue from adjacent bone or joint is well recognized. However, primary tuberculous pyomyositis, tuberculous bursitis, and tuberculous tenosynovitis are rare entities constituting 1% of skeletal tuberculosis. Tuberculous tenosynovitis involves most commonly the tendon sheaths of the hand and wrist, and tuberculous bursitis occurs most commonly around the hip. The greater trochanteric bursa and the greater trochanter are the most frequent sites of tuberculous bursitis. Cases of primary tuberculous pyomyositis and tenosynovitis of the tendons of the ankle and foot are seldom reported in the radiology literature. All imaging modalities-plain radiography, bone scan, computed tomography, and magnetic resonance imaging (MRI)--provide information that is helpful in determining therapy. MRI in particular, with its multiplanar capabilities and superb contrast of soft tissue, can demonstrate the extent of the soft tissue mass and access the adjacent bones and joints. However, MRI has no diagnostic specificity in regard to tuberculosis, and in nonendemic areas, biopsy is strongly recommended. All patients in this review were permanent residents of North America or Western Europe and were immunocompetent. Examples of atypical presentations of the above entities are demonstrated.     

The role of imaging modalities in diagnosis and managment of pyomyositis

A case of tropical pyomyositis in a temperate climate is reported and 29 more cases are reviewed from the literature. Because of its rarity and deceiving clinical presentation, the disorder may go unrecognized for weeks in nontropical regions. The role of various imaging modalities in timely and accurate diagnosis and nonsurgical management of this disorder is discussed.     

Letale „nicht-tropische“ Pyomyositis – Falldarstellungen und Literaturübersicht

Pyomyositis is an acute bacterial infection with abscess formation in the skeletal muscles mostly due to Staphylococcus aureus. ¶The disease is found more often in males. Since the patients symptoms and the clinical and laboratory findings are relatively unspecific, the clinical diagnosis of pyomyositis can present difficulties. Furthermore, cases of ¶pyomyositis are rare in non-tropical countries and some physicians may not be familiar with it. If not diagnosed and treated properly, pyomyositis can lead to sepsis and death. Although the pathogenesis of the disease has not yet been clarified, some predisposing factors of forensic interest are well known: (trivial) trauma or vigorous exercise of the affected skeletal muscles, small potentially “septic” foci in other tissues or internal organs and a preexisting immunodeficiency, e. g. in diabetes mellitus, intravenous drug abusers or individuals suffering from HIV. Three cases of “non-tropical” pyomyositis with fatal outcome are presented and the literature on the subject is reviewed with special reference to epidemiological and etiological factors, taking forensic aspects, histomorphologic findings and the problems of post-mortem diagnosis of pyomyositis into consideration.     

Contribution of imaging to the evaluation of pyomyositis

PURPOSE: To analyse the fundamental features of each imaging modality with the aim of defining their contribution to the diagnosis of pyomyositis. MATERIALS AND METHODS: We retrospectively reviewed 10 observations collected between 1997 and 2004, 5 of paravertebral muscles and 5 of the muscles of the limbs. Imaging was carried out with US (8/10 observations) and/or CT (9/10 observations), and/or MRI (6/10 observations). The pathogen was isolated in 6/10 observations. RESULTS: The imaging criteria for the detection and characterization of pyomyositis are based on three pathological phases: an invasive phase characterized by inflammatory oedema, a suppurative phase characterised by abscess development, and a late phase featuring the distant spread of the infection. Based on these interpretation criteria, pyomyositis was correctly diagnosed with US in 5/8 observations, with CT in 9/9 observations and with MR in 5/6 observations. Four false-negative cases were found. CONCLUSIONS: Since the clinical symptoms of pyomyositis are often insidious and delayed, an integrated imaging approach may be very useful for diagnosing this condition.     

Muscle compromise in diabetes

Muscle compromise associated with diabetes includes muscle infarction, myositis, pyomyositis, and abscess formation. These conditions may also be seen in various other conditions, such as trauma, alcoholism, neoplasia, vasculopathy, HIV infection, and other immunocompromised states and hemoglobinopathies. Due to recent advances in imaging technology, these entities are readily detected and treated at an earlier stage. Different diagnostic modalities may be used, particularly magnetic resonance imaging (MRI), which is best for soft-tissue pathologies. Muscle infarction appears with acute edema and inflammatory changes on T1- and T2-weighted images, enhancing peripherally postcontrast, and nonenhancing central areas suggestive of necrosis, lacking focal fluid collections. The latter feature may help to exclude abscesses, as these mostly present with fluid collections. Pyomyositis in its early period demonstrates ill-defined muscle enlargement with increased signal on T2-weighted images. Myositis shows no signal changes or mild hypointensity on T1-weighted images, but diffuse hyperintensity on T2-weighted images, with no or minimal enhancement following intravenous contrast media. Recognition of these pathologies is important, since management approaches vary depending on the etiology of the muscle involvement and overall status of the patient.     

Magnetic resonance imaging of intraspinal cystic lesions: a pictorial review

Magnetic resonance imaging is the imaging modality of choice for the evaluation of diseases of the spinal cord and its coverings primarily because of improved lesion detection and characterization. The differentiation of intramedullary pathologic conditions (arising within the spinal cord) from extramedullary lesions (lying either within the thecal sac (intradural) or outside it (extradural) is usually straightforward. Although many lesions may occur in more than one compartment or may extend to involve more than one compartment simultaneously, accurate positioning of a detected lesion within the spinal canal and the assessment of its signal characteristics may help differentiate many of the more commonly encountered lesions and aid preoperative diagnosis. This pictorial review discusses the imaging findings and distinguishing features of a variety of intramedullary and extramedullary intraspinal cystic lesions with the use of magnetic resonance imaging. The imaging appearances are correlated with histologic findings where available.     

Imaging findings of complications affecting the upper extremity in intravenous drug users: featured cases

Infections generally occur in intravenous drug abuse (IVDA) patients, most commonly affecting the spine and proximal joints. Numerous serious musculoskeletal complications of IVDA may involve the upper extremity, however. Soft-tissue complications in the upper extremity of IVDA patients include cellulitis, ulceration, abscess, pyomyositis, septic bursitis, tenosynovitis, and necrotizing fasciitis. Foreign bodies in soft tissue due to needle fragments are common findings. Primary bone and joint IVDA complications include osteomyelitis (acute and chronic) and septic arthritis. Other IVDA complications in the upper extremity affecting blood vessels and lymphatics include hematoma, arterial aneurysm and pseudoaneurysm, thrombosis, thrombophlebitis, "puffy hand" syndrome, and lymphadenopathy. These complications usually present as urgent issues requiring prompt and accurate evaluation in the acute setting. Diagnostic imaging not only aids in making the correct diagnosis but also permits precise definition of the location and extent of these abnormalities. We review the imaging findings and illustrate a wide range of disabling and even life-threatening complications affecting the upper extremity of IVDA patients that require early diagnosis for optimal outcome.     

Pediatric seizure imaging

The objective of this article was to show the spectrum of magnetic resonance and computed tomographic abnormalities in the pediatric seizure patient. Seizure is a common indication for pediatric neuroimaging. Characteristic imaging findings can lead to a specific pathologic diagnosis. Imaging findings may be subtle. Clinical correlation and optimization of magnetic resonance imaging protocols are important for seizure imaging.     

Magnetic resonance imaging of pyomyositis in 43 cases

PURPOSE: To describe the magnetic resonance imaging (MRI) findings in pyomyositis. METHODS AND MATERIALS: Forty-three patients with proven muscle infection (30 males, 13 females) ranging in age from 14 to 86 years (mean 42 years) were studied with MRI. The initial clinical diagnose were soft tissue infection (n=27), neoplasm (n=12), thrombophlebitis (n=3), and lymphedema (n=1). Spin-echo T1- and T2-weighted images were obtained in all cases and STIR sequence in 6. Spin-echo T1-weighted images after Gd-DTPA injection were obtained in 16 cases. The signal intensity findings, the extent of the abnormalities in the soft tissue (muscle, fascial and subcutaneous involvement), the presence of fluid collections, and the involvement of neighbouring bone and joint were reviewed retrospectively. RESULTS: A hyperintense signal on T2-weighted and STIR images were detected in all patients. Fluid collections were seen in 21 cases as localized areas of hypointensity on the T1-weighted images, and highly hyperintense areas on the T2-weighted images. In four patients a rim of high signal intensity was seen around the fluid collection on the T1-weighted images. On contrast-enhanced T1-weighted images there was diffuse enhancement in the patients without fluid collections that was heterogeneous in seven and homogeneous in two. After Gd-DTPA all fluid collections showed a central area without enhancement and a well-defined enhancing peripheral rim. Involvement of adjacent structures included subcutaneous tissue (n=25), bone marrow (n=14), fascial planes (n=15) and joints (n=11). CONCLUSION: MRI is useful in the assessment of pyomyositis and in determining the location and extension. A hyperintense rim on unenhanced T1-weighted images and peripheral enhancement after Gd-DTPA are useful for identifying the number, size, and location of soft-tissue abscesses.     

Magnetic resonance imaging of septic arthritis

Septic arthritis is a disabling and life-threatening disease that requires early diagnosis for optimal outcome. Although traditionally a clinical and laboratory diagnosis, some patients may be misdiagnosed and referred for magnetic resonance (MR) imaging. Therefore, radiologists need to be aware of the MR imaging findings of septic arthritis, its complications, and diagnostic pitfalls.     

Solitary neurofibroma of the vagus nerve in the aortopulmonary window masquerading as a developmental cyst

A rare case of solitary neurofibroma of the vagus nerve in the aortopulmonary window masquerading as a developmental cyst is reported. Its computed tomographic characteristics and magnetic resonance imaging are described and correlated with pathologic findings. Although the features of such imaging modalities are quite characteristic for a neurofibroma, its differentiation from "atypical" developmental cysts may be difficult.     

Focal pyomyositis of the perisciatic muscles in children

OBJECTIVE: The purpose of this report is to describe the role of MR imaging in the diagnosis of focal pyomyositis surrounding the sciatic nerve in children. CONCLUSION: In the absence of joint effusion on sonography, MR imaging should be considered in pediatric patients who present with a febrile illness and incapacitating pelvic pain.     

Primary malignant melanoma of the anterior mediastinum: CT and MR findings

Malignant melanoma presenting in the mediastinum without an extrathoracic primary is extremely rare. To our knowledge, its imaging findings have not been described in the radiologic literature. We report a case of primary malignant melanoma of the anterior mediastinum and discuss its imaging findings on computed tomography and magnetic resonance imaging.     

Tuberculous arthritis of the knee joint mimicking pigmented villonodular synovitis

Tuberculous arthritis is difficult to diagnose early because of its atypical insidious clinical manifestations and non-specific imaging findings. Specifically, monoarticular tuberculosis of the knee may mimic pigmented villonodular synovitis (PVNS). The present report describes a young patient with tuberculous arthritis of the knee. Proper diagnosis was delayed due to magnetic resonance imaging findings, such as hemosiderin deposits and a nodular mass around the knee joint, suggesting the diffuse type of PVNS. These findings suggest that the first step in the diagnosis of tuberculous knee arthritis is to have a high index of suspicion.