Skeletal muscle disease: patterns of MRI appearances.

Although the presumptive diagnosis of skeletal muscle disease (myopathy) may be made on the basis of clinical-radiological correlation in many cases, muscle biopsy remains the cornerstone of diagnosis. Myopathy is suspected when patients complain that the involved muscle is painful and tender, when they experience difficulty performing tasks that require muscle strength or when they develop various systemic manifestations. Because the cause of musculoskeletal pain may be difficult to determine clinically in many cases, MRI is increasingly utilised to assess the anatomical location, extent and severity of several pathological conditions affecting muscle. Infectious, inflammatory, traumatic, neurological, neoplastic and iatrogenic conditions can cause abnormal signal intensity on MRI. Although diverse, some diseases have similar MRI appearances, whereas others present distinct patterns of signal intensity abnormality. In general, alterations in muscle signal intensity fall into one of three cardinal patterns: muscle oedema, fatty infiltration and mass lesion. Because some of the muscular disorders may require medical or surgical treatment, correct diagnosis is essential. In this regard, MRI features, when correlated with clinical and laboratory findings as well as findings from other methods such as electromyography, may facilitate correct diagnosis. This article will review and illustrate the spectrum of MRI appearances in several primary and systemic disorders affecting muscle, both common and uncommon. The aim of this article is to provide radiologists and clinicians with a collective, yet succinct and useful, guide to a wide array of myopathies.

Wegener granulomatosis masquerading as pneumonia.

We report a case of an elderly patient with a limited form of Wegener granulomatosis, which simulated the clinical and imaging features of organizing pneumonia. Here we call attention to this atypical case presentation that eloquently illustrates the many faces of Wegener granulomatosis.

Intrahepatic venous continuation associated with inferior vena cava hypoplasia: evaluation with sonography, MR imaging and MR angiography.

A 17-year-old Asian girl was admitted to our hospital because of acute onset of abdominal pain. Abdominal imaging work-up revealed an unusual pattern of congenital vascular anomalies, including a hypoplastic IVC and large intrahepatic venous collaterals along with an atypical, accessory hepatic vein. Congenital or acquired abnormalities of the inferior vena cava (IVC) can lead to formation of collateral pathways that help bypass the blood flow obstacle.

Imaging findings in symptomatic patients with femoral diaphyseal stress injuries.

PURPOSE: To assess the imaging findings seen in symptomatic patients with stress injuries of the femoral diaphysis. MATERIAL AND METHODS: Seven patients (5 F, 2 M, age range 16 to 56 years, mean 38 years) underwent imaging evaluation of the symptomatic lower extremity due to an insidious onset of thigh or groin pain unrelated to trauma. Imaging studies included radiography and magnetic resonance imaging (MRI) in seven patients, bone scintigraphy in five, and computed tomography (CT) in three. RESULTS: Radiographs depicted three frank fractures in two patients, and revealed findings of stress injury in six patients. Available scintigraphic and CT findings were abnormal. On MR images, a solitary fracture was seen in two patients; two patients presented with bilateral stress fractures of the femoral diaphysis; and all seven patients had the imaging features of stress injury. Femoral diaphyseal stress fractures (n = 6) appeared as linear regions of T1- and T2-weighted low signal intensity, surrounded by diffuse bone marrow edema. Three of the six frank fractures, with an evident fracture line, were longitudinal and parallel to the cortical surface. CONCLUSION: Femoral diaphyseal stress fractures are often inconspicuous with conventional radiography. MRI depicts the changes of stress injury in the femoral diaphysis, and is particularly useful in documenting the presence, morphology, and extent of fracture(s), information valuable for definitive diagnosis and appropriate management.

Magnetic resonance imaging of para-acetabular insufficiency fractures in patients with malignancy.

AIM: To describe the characteristic magnetic resonance imaging (MRI) findings of para-acetabular insufficiency fractures in patients with malignancy, and compare the MRI appearance of these fractures with that of metastatic bone disease. MATERIALS AND METHODS: MRI examinations were reviewed in 16 patients with a known malignant tumour and severe hip pain that raised the possibility of local recurrence or metastatic disease. Six patients had received pelvic irradiation, and three patients were receiving steroid medication. RESULTS: The total number of fractures detected was 21: a solitary fracture was present in 11 patients and five patients had bilateral para-acetabular fractures. Two patients had associated sacral insufficiency fractures, and one of them had stress fractures involving both acetabular columns. Conventional radiography allowed the diagnosis of 14 (67%) fractures; six (28%) radiographic examinations were negative; and one (5%) examination was equivocal for fracture. Available scintigraphic and computed tomography (CT) studies revealed typical findings of fracture. Using MRI, insufficiency fractures appeared as linear regions of low signal intensity on T1- and T2-weighted images. Marked marrow oedema was evident in all cases. Fractures characteristically were parallel to the superior acetabulum in a curvilinear fashion in 18 (86%) instances, and were oblique in three (14%) instances. The fractures demonstrated considerable enhancement after intravenous gadolinium administration. No associated soft tissue masses were documented. CONCLUSION: Para-acetabular insufficiency fractures are a cause of hip pain, which may mimic skeletal metastasis in the patient with malignancy and pelvic irradiation. Recognition of the characteristic MRI findings of these fractures can preclude misdiagnosis and unnecessary bone biopsy.

Posterolateral complex knee injuries: magnetic resonance imaging with surgical correlation.

PURPOSE: To describe the magnetic resonance imaging (MRI) findings of injuries of the posterolateral aspect of the knee and to evaluate the diagnostic capabilities of MRI in the assessment of these injuries. MATERIAL AND METHODS: The MRI studies of 14 patients (mean age 33 years) with trauma to the posterolateral aspect of the knee were retrospectively reviewed, and the imaging findings were correlated with those of surgery. RESULTS: In all patients, MRI showed an intact iliotibial (ITB) band. MRI showed injury to the biceps tendon in 11 (79%), the gastrocnemius tendon in 1 (7%)), the popliteus tendon in 5 (36%), and the lateral collateral ligament (LCL) in 14 (100%) patients. Tear of the anterior cruciate ligament (ACL) was seen in 11 (79%) patients and tear of the posterior cruciate ligament (PCL) in 4 (29%) patients. With routine MRI, visualization of the popliteofibular or fabellofibular ligaments was incomplete. On MRI, the lateral meniscus and the medial meniscus were torn with equal frequency (n = 4; 29%). Osteochondral defects were seen in 5 (36%) cases and joint effusion in all 14 (100%) cases on MRI. Using surgical findings as the standard for diagnosis, MRI proved 86% accurate in the detection of injury to the ITB band, the biceps tendon (93%), the gastrocnemius tendon (100%), the popliteus tendon (86%), the LCL (100%), the ACL (79%), the PCL (86%), the lateral meniscus (90%), the medial meniscus (82%), and the osteochondral structures (79%). Surgical correlation confirmed the MRI findings of joint effusion in all cases. CONCLUSION: MRI is well suited for demonstrating the presence and extent of injuries of the major structures of the posterolateral complex of the knee, allowing characterization of the severity of injury.

Avulsion fractures of the medial and lateral malleoli of the ankle in cadavers: new radiographic projections for improved diagnosis.

The malleolar attachment sites of the tibionavicular (TN), tibiocalcaneal (TC), posterior tibiotalar (PTT), anterior talofibular (ATF), and calcaneofibular (CF) ligaments of 3 cadaveric ankles were dissected. Standard and new radiographic projections of the ankle were obtained with the foot in different positions and various degrees of beam angulation. Simulated avulsion injuries related to these ligaments were created, and the visibility of these structures was assessed. Avulsion injuries of the TN ligament were better assessed in the plantar-flexed radiographs with lateral beam angulation. Standard projections were found to adequately depict avulsion fractures related to the TC and CF ligaments. Radiographs in external ankle rotation were best for evaluating injuries of the PTT ligament. Avulsion injuries related to the ATF ligament were best visualized in the plantar-flexed views with medial beam angulation. Modified radiographic projections of the ankle improve visualization of ligamentous structures of the malleoli and avulsion injuries related to those.

MR imaging of uncommon recurrence of fibrolipomatous hamartoma of the ulnar nerve.

We present the MR and histopathologic findings of fibrolipomatous hamartoma (FLH) of the ulnar nerve in a 54-year-old woman, a lipomatous process that rarely affects the ulnar nerve. The case illustrated is further unusual as a local soft tissue recurrent mass developed over a remarkably long course of the disease.

MR imaging of the midfoot: normal anatomy with cadaveric correlation.

MR imaging has an invaluable role in the diagnosis of foot and ankle pathology. Analyzing abnormalities on MR images depends upon a thorough understanding of the normal anatomy. This article reviews the MR anatomy of the midfoot with cadaveric correlation.

Osteonecrosis of the patella: imaging features.

Osteonecrosis of the patella, although uncommon, has become important to recognize because it can be a cause of pain in the knee. We describe the imaging manifestations of nontraumatic osteonecrosis of the patella in seven clinical cases. The lesions uniformly involved the superior aspect of the patella. Conventional radiography displayed increased radiodensity, subchondral radiolucent areas, and typical demarcation line surrounding the ischemic region. MR imaging and bone scintigraphy demonstrated the characteristic features of osteonecrosis. Recognition of the imaging findings of osteonecrosis involving the patella can preclude misdiagnosis and may obviate unproductive invasive diagnostic procedures.

MRI of the medial and lateral plantar nerves.

PURPOSE: The purpose of this work was to demonstrate nerve anatomy of the medial plantar (MP) and lateral plantar (LP) nerves and the first branch of the lateral plantar (FBLP) nerve as depicted with MRI. METHOD: High resolution MRI of the heel was performed with a standard transmit-receive extremity coil in six human cadaveric specimens using sagittal, axial, and coronal T1-weighted spin echo images. The specimens were then sectioned in the axial and coronal planes. RESULTS: MRI depicted the MP and LP nerves arising from the posterior tibial (PT) nerve. Assessment of the anatomic course and trifurcation of the PT nerve into the plantar nerves and the FBLP nerve was best seen in the sagittal plane. Various portions of these nerves were visualized also in the axial and coronal imaging planes. CONCLUSION: MRI may demonstrate the origin, course, and branching of nerves in the heel and can provide a means for assessment of the patient presenting with chronic heel pain and suspected entrapment neuropathy.

Multimodal imaging quantitation of the lesion size in osteonecrosis of the femoral head.

Early diagnosis of osteonecrosis of the femoral head is important for initiating early treatment, which is associated with a more favorable outcome for patients. Confusion in evaluating the severity of the disease, and the clinical outcome after treatment partially is attributed to the use of various staging systems that are based on qualitative rather than quantitative criteria. At the authors' institution, 45 patients (77 hips) with osteonecrosis of the femoral head were evaluated using a multimodal imaging approach that included conventional radiography, bone scintigraphy, and magnetic resonance imaging. A computerized image analysis program that allowed quantification of the lesion size on radiographs and magnetic resonance images was used. Measurements of the extent of involvement on radiographs and selected serial magnetic resonance images were compared in 33 hips (42.9%) before collapse versus 44 hips (57.1%) after collapse. The size of the necrotic lesion varied significantly according to the specific stage of disease. Quantification of the lesion during the course of the disease provided a record of the progression of osteonecrosis, despite a spurious stability in staging. In general, conventional radiography closely approximated measurements of the lesion size obtained by magnetic resonance imaging. Bone scintigraphy and magnetic resonance imaging were well suited for detection of osteonecrosis at an early stage. Finally, precise quantification of the lesion size was an optimal preoperative means for evaluating the extent of involvement of the femoral head in the early and advanced stages of osteonecrosis.

Mesenchymal chondrosarcoma of soft tissues of the calf.

Mesenchymal chondrosarcomas are distinct from conventional and dedifferentiated chondrosarcomas and are quite rare, making up less than 2% of all chondrosarcomas. We describe a mesenchymal chondrosarcoma of the soft tissues of the calf and review the differential diagnosis of this poorly understood entity.

Tarsal sinus: arthrographic, MR imaging, MR arthrographic, and pathologic findings in cadavers and retrospective study data in patients with sinus tarsi syndrome.

PURPOSE: To evaluate the tarsal sinus by using different imaging techniques and specialized planes. MATERIALS AND METHODS: Magnetic resonance (MR) imaging of the tarsal sinus was performed in 10 cadavers. Conventional arthrography of the anterior and posterior subtalar joints was then performed. Tarsal sinus ligaments were evaluated further on initial and reconstructed MR arthrograms along and perpendicular to their axes. Pathologic correlation was performed in five specimens suspected of having tarsal sinus lesions on the basis of initial imaging findings. In 37 patients with a clinical diagnosis of sinus tarsi syndrome, MR images of the ankle were obtained before and after intravenous gadolinium-based contrast material administration and were reviewed to verify the integrity of the tarsal sinus ligaments. RESULTS: Two complete and three partial cervical ligament (CL) tears and one complete interosseous talocalcaneal ligament (ITCL) tear were diagnosed with MR imaging. Only one complete and one partial CL tear were seen after evaluation of both initial and reconstructed MR arthrograms and confirmed with pathologic correlation. In 18 patients, the diagnosis was confirmed at MR imaging, which depicted ITCL and CL tears in 11 patients, isolated CL tears in three patients, ganglia in three patients, and pigmented villonodular synovitis in one patient. CONCLUSION: Cadaveric study results indicate that initial and reconstructed MR arthrograms along and perpendicular to the ligament axes are potentially useful for further evaluation of individual tarsal sinus structures.

Quantitative computed tomography of spine: comparison of three-dimensional and two-dimensional imaging approaches in clinical practice.

Quantitative computed tomography (QCT), a widely utilized technique for determining bone mineral density (BMD) at various skeletal sites, may yield less precise measurements if there are operator measurement errors and other technical variables. Two-dimensional (2D)and three-dimensional (3D)QCT scans of the lumbar spine of 21 women were compared in order to investigate the effects of potential operator variability on the precision of BMD measurements and to examine resulting differences of these imaging approaches in clinical practice. No significant difference was found (p > 0.05) in precision between the 2D and 3D QCT BMD measurements owing to operator measurement errors on the CT scans. The variability in BMD values within numerous small regions of interest (ROIs)( approximately 75 mm (2) ) of cancellous bone within a single vertebra was 10.1%, larger than the 2D or 3D BMD variability measured in typical regions ( approximately 250 mm (2)) by an order of magnitude. 3D BMD values in this population, which represented a wide range of clinical values, were found to be significantly greater than 2D BMD values by an average of 5.6% (p = 0.00024) relative to the 2D QCT values. Our findings suggest technical measurement error does not have a significant effect on precision of BMD measurements obtained with either QCT method. Several factors, however, including the incorporation of focal regions of higher density bone mass within the 3D QCT ROI may account for the higher BMD values compared with those for 2D QCT.