MRI diagnosis of diabetic muscle infarction: report of two cases

 Diabetic muscle infarction (DMI) is a rare complication of diabetes mellitus occurring in patients with poorly controlled insulin-dependent diabetes. In previous reports, the diagnosis of this condition was based on the pathologic studies, although MRI examinations were performed in a few patients as part of the diagnostic work-up. In this report, we describe two additional cases of DMI where the diagnosis was based on the MRI findings in conjunction with the clinical picture and laboratory studies. The patients usually present with thigh or calf pain and swelling, are afebrile, and have normal white blood cell count. MRI examination typically shows diffuse swelling and increased signal intensity on T2-weighted images in the affected muscles, with no focal fluid collections. In the proper clinical setting, these findings are diagnostic of DMI and patients should be spared unnecessary invasive diagnostic examinations such as lower extremity venograms and biopsies.     

Diabetic muscle infarction: radiologic evaluation

 Objective. Diabetic muscle infarction (DMI) is frequently misdiagnosed clinically as abscess, neoplasm, or myositis, and is often biopsied. Clinical and radiologic findings are presented here to enable the radiologist to suggest the correct diagnosis. Design and patients. Four patients with severe diabetes mellitus presenting with acute thigh pain, tenderness, and swelling were evaluated by imaging techniques and biopsy. Results and conclusions. Edema in the affected muscles was seen in two patients with MRI studies. Femoral artery calcification and mild muscle swelling was present in one patient who underwent CT. Decreased echogenicity was seen in the involved muscle in a patient studied with ultrasound. Serum enzymes were normal or mildly elevated in three patients (not reported in one). Biopsy demonstrated necrosis and regenerative change in all cases. MRI, although nonspecific, is the best imaging technique to suggest the diagnosis of DMI in the appropriate clinical setting, thereby obviating biopsy.     

Subcutaneous granuloma annulare: MR imaging findings

We present a case of subcutaneous granuloma annulare evaluated with MR imaging. The mass was poorly defined and showed thickened interconnecting strands with low signal intensity on T1- and T2-weighted MR images. When a poorly defined subcutaneous mass with low signal intensity on both T1- and T2-weighted MR images is observed in an otherwise healthy child, subcutaneous granuloma annulare should receive serious consideration. Subcutaneous granuloma annulare should be added to the list of tumors with short T2.     

Characteristics of calcaneal bone infarction: an MR imaging investigation

Objective. Bone infarction (BI) of the calcaneus is an uncommon entity which has received little mention in the recent literature. In this paper, we review the MR images of six calcanei with BI, which demonstrate a pattern of presentation that may explain the etiology of BI at this unusual location. Design. A retrospective review was performed of the transcribed reports of the foot or ankle MR examinations at our institution. MR images of examinations with any marrow signal abnormality were reviewed for presence of BI and its distribution. Patients. Based on MRI criteria, four patients had calcaneal BI (none biopsy proven); they ranged in age from 37 to 51 years old. Two patients were diagnosed with systemic lupus erythematosus, one with fibrositis, and another with polymyositis. All were treated with corticosteroids. Results. Six calcanei (in four patients) contained a region of calcaneal BI. In five of the six, the lesions were entirely or predominantly located in the posterior half of the calcaneus. Conclusion. Two theories are proposed which may explain why BI predominantly occurs in the posterior half of the calcaneus. First, the convergence of the recurrent intraosseous calcaneal vessels may occasionally produce the equivalent of a single dominant vessel that is more prone to vascular accidents. Secondly, the region between the recurrent and the epiphyseal vessels may act as a watershed zone, increasing its susceptibility to ischemia.     

Muscle impingement: MR imaging of a painful complication of osteochondromas

 The purpose of this study was to describe the magnetic resonance (MR) appearance of a newly recognized complication of osteochondromas. Two patients presented with pain and swelling over known osteochondromas. Plain radiographic studies were unrevealing. MR examinations were obtained to characterize the exostoses further and evaluate areas of palpable fullness. Increased signal was present in the muscles on T2-weighted images, which correlated with physical findings and was believed to represent muscle injury due to the osteochondroma. Pain and fullness may result from a number of osteochondroma-related complications, the most worrisome of which is malignant degeneration. Muscular impingement and injury should be considered in the differential diagnosis of pain and swelling in the region of an exostosis. MR imaging allows distinction of this entity, which may be radiographically occult and confused clinically with fracture, bursitis, or malignant degeneration.     

MR appearance of parasymphyseal insufficiency fractures of the os pubis

 Objective. To clarify the MRI features of parasymphyseal insufficiency fractures of the os pubis. Design and patients. MRI was performed in four postmenopausal women with parasymphyseal insufficiency fractures. The diagnosis was confirmed with plain films in every patient. T1-weighted and T2-weighted images were obtained in four patients using a 1.5-T unit. Postcontrast T1-weighted imaging was also done in three patients. Results and conclusions. MRI of pubic parasymphyseal insufficiency fracture characteristically demonstrates a hyperintense mass lesion with a hypointense rim on T2-weighted imaging, showing peripheral and septal enhancement after contrast administration. It is important to have this entity in mind in patients with osteoporosis, especially in patients with a history of pelvic irradiation for malignant disease, so as not to misinterpret it as a chondroid tumor or bone metastasis.     

Sclerosing epithelioid fiberosarcoma: short T2 on MR imaging

A case of sclerosing epithelioid fibrosarcoma and its appearance on MRI is presented. The tumor showed a zonal architecture on MRI with a large central core of very low signal intensity and a peripheral rim of intermediate to high signal intensity on T1- and T2-weighted spin echo pulse sequences. The core showed decreased cellularity with dense collagen deposition on histologic examination, and the peripheral zone increased cellularity with increased nuclear atypia. The presence of a prominent region of very low signal intensity on T1- and T2-weighted images can be seen with neural tumors, giant cell tumor of the tendon sheath, aggressive fibromatosis, and, in rare instances, with soft tissue sarcomas rich in collagen.     

Phalangeal microgeodic syndrome: MR appearance

The authors describe the MR features of a case of microgeodic phalangeal syndrome in a 9-year-old boy. Roentgenograms showed multiple small areas of osteolysis in the middle phalanx of the right index finger. T1-weighted MR images showed lesions with diffuse low signal intensity not only in this phalanx but also in other phalanges. These lesions exhibited high signal intensity on T2-weighted images. Contrast- enhanced T1-weighted images showed a wide non-enhancing area in the middle phalanx of the index finger. Received: 26 September 2000 Revision requested: 2 November 2000 Revision received: 25 November 2000 Accepted: 27 November 2000     

Littoral cell angioma of the spleen: CT and MR imaging appearance

We report a case of littoral cell angioma (LCA) of the spleen, a recently described splenic pathology, which imaging characteristics and pathologic morphology have been discussed only by a few authors. The imaging findings in unenhanced and contrast-enhanced MRI and CT as well as histologic specimen are presented. Diagnosis was made after elective splenectomy. Differential diagnosis of splenic tumors as well as the imaging findings in this particular case are discussed. Received: 7 July 1999; Revised: 18 January 2000; Accepted: 19 January 2000     

Fracture of the lateral process of the talus: appearance at MR imaging and clinical significance

The case of a 59-year-old man with chronic lateral ankle pain following an inversion injury is presented. MR imaging performed to evaluate for soft tissue injury revealed an unsuspected fracture of the lateral process of the talus. The patient underwent surgical exploration of the fracture with debridement of adjacent loose bodies and is currently undergoing aggressive physical rehabilitation. Received: 23 November 1998 Revision requested: 18 December 1998 Revision received: 4 January 1999 Accepted: 4 January 1999     

Metastatic bone tumor mimicking spontaneous osteonecrosis of the medial condyle of the femur: misleading appearance on MR imaging

We report a case of a metastatic bone tumor that mimicked spontaneous osteonecrosis of the medial condyle of the femur on magnetic resonance imaging. Received: 5 October 1999 Revision requested: 11 November 1999 Revision received: 10 January 2000 Accepted: 17 January 2000     

Imaging of muscle injuries

 Although skeletal muscle is the single largest tissue in the body, there is little written about it in the radiologic literature. Indirect muscle injuries, also called strains or tears, are common in athletics, and knowing the morphology and physiology of the muscle-tendon unit is the key to the understanding of these injuries. Eccentric muscle activation produces more tension within the muscle than when it is activated concentrically, making it more susceptible to tearing. Injuries involving the muscle belly tend to occur near the myotendinous junction. In adolescents, the weakest link in the muscle-tendon-bone complex is the apophysis. Traditionally, plain radiography has been the main diagnostic modality for evaluation of these injuries; however, with the advent of MRI it has become much easier to diagnose injuries primarily affecting the soft tissues. This article reviews the anatomy and physiology of the muscle-tendon unit as they relate to indirect muscle injuries. Examples of common muscle injuries are illustrated.     

Hemorrhagic prepatellar bursitis

 Simple prepatellar bursitis is easily diagnosed both clinically and by MRI. MRI shows the typical T1 and T2 lengthening of fluid within the bursa. However, because of complex MRI appearance of hemorrhage, chronic hemorrhagic bursitis and the size of the prepatellar mass the clinical and MRI appearance can be very different.     

Skeletal muscle lymphoma: observations at MR imaging

 We present the MR appearances of three patients with biopsy-proven primary lymphoma of skeletal muscle. In each case lymphoma resulted in bulky expansion of the involved muscle, homogeneously isointense to skeletal muscle on T1-weighted images, homogeneously hyperintense to skeletal muscle on T2-weighted images and diffusely enhancing following intravenous administration of gadopentate dimeglumine.     

MRI appearance of clear cell hidradenoma

We present the first reported MR imaging findings of a histologically proven clear cell hidradenoma. A fluid level was noted on all pulse sequences in this lesion, which demonstrated a prominent hemorrhagic component on sectioning. The presence of an enhancing nodule was also noted, differentiating this lesion from a post-traumatic hematoma. Fluid levels in a well-defined subcutaneous soft tissue mass should suggest the possibility of a hidradenoma. Received: 19 June 1998; Revision requested: 29 July 1998; Revision received: 28 October 1998; Accepted: 29 October 1998     

Extraosseous manifestation of Gaucher's disease type I: MR and histological appearance

Gaucher's disease type I is the most prevalent lysosomal storage disorder caused by an autosomal-recessive inherited deficiency of glucocerebrosidase activity with secondary accumulation of glucocerebrosides within the lysosomes of macrophages. The storage disorder produces a multisystem disease characterized by progressive visceral enlargement and gradual replacement of bone marrow with lipid-laden macrophages. Skeletal disease is a major source of disability in Gaucher's disease. Extraosseous extension of Gaucher cells is an extremely rare manifestation of skeletal Gaucher's disease. This is a report on the MRI and histopathological findings of an extraosseous Gaucher-cell extension into the midface in a patient with Gaucher's disease. Received: 27 January 2000; Revised: 15 March 2000; Accepted: 16 March 2000     

Collagenous fibroma of the arm: a report of two cases

A recently proposed addition to fibrous tumors in soft tissue was first described as desmoplastic fibroblastoma and later renamed collagenous fibroma. This tumor is clinically and morphologically distinct and benign. However, only a few series have been reported, and the clinicopathologic features are not widely recognized. We present two cases of collagenous fibroma of the arm. Both patients presented with an enlarging, well-circumscribed and mobile soft tissue mass. Magnetic resonance imaging showed areas of low signal intensity on both T1- and T2-weighted sequences. Needle aspiration cytology revealed nondiagnostic samples because of the low cellularity of the tumors. Each of the resected tumors was composed of low-cellular spindle- to stellate-shaped cells in a fibrous matrix with clear margination. After the marginal excisions, no recurrences were observed. Clinicians should be aware of this entity to prevent overtreatment, because imaging findings and cytologic features are similar to those of desmoid tumor. Received: 15 December 1999 Revision requested: 12 January 2000 Revision received: 31 March 2000 Accepted: 17 March 2000     

Primary hemangiopericytoma of the tibia: MR and angiographic correlation

The Magnetic Resonance Imaging (MRI) appearances of primary osseous hemangiopericytoma (HPC) have been rarely described. We report on a 46-year-old Chinese man with primary osseous HPC of the right tibia. The characteristic vascular distribution of this tumor, presenting with a ”spoke-wheel” appearance on MR images and with angiographic correlation, is described. Although not pathognomonic, this MR appearance may be an important finding in suggesting the diagnosis of osseous HPC. Received: 3 March 1999 Revision requested: 26 April 1999 Revision received: 13 September 1999 Accepted: 15 September 1999     

Indirect wrist MR arthrography: the effects of passive motion versus active exercise

Purpose.In the wrist, to determine whether passive motion or active exercise yields a better indirect MR arthrographic effect following intravenous gadolinium administration. Design and patients. Twenty-six consecutive patients were studied by indirect wrist MR arthrography. In half active exercise and in half passive motion was performed. Four regions of interest were studied including the distal radioulnar joint, the radiocarpal joint, the midcarpal joint, and the triangular fibrocartilage. Ranges and means of signal intensity were calculated. Surgical follow-up was performed in 22 patients. Results. The joint fluid intensity was greatest in the distal radioulnar joint. Fluid signal intensity was greater and more consistent in the passive motion group although the results did not achieve statistical significance. Imaging accuracy appeared similar in the two groups and was excellent for the triangular fibrocartilage (100%) and scapholunate ligaments (96%). Conclusion. Active exercise and passive motion yield similar degrees of wrist arthrographic effect, but the effect of passive motion is somewhat more consistent. Preliminary data show good accuracy for internal derangements. Received: 4 June 1999 Revision requested: 6 August 1999 Revision received: 14 September 1999 Accepted: 20 September 1999