MR Findings of Infectious Myositis Caused by Vibrio vulnificus: Case Report

Vibrio vulnificus infection is a fatal disease occurring after the consumption of seafood in patients with underlying liver disease. Inflammation of the skin, subcutanous fat and fascia disseminates from the lower extremity to the trunk and upper extremity Infectious myositis caused by vibrio vulnificus is rare, and its MR imaging findings have not been reported. We report these in a case of infectious myositis caused by vibrio vulnificus involving both lower extremities.

MR Findings of Acute Rhabdomyolysis: Case Report

Rhabdomyolysis is an acute disorder resulting from skeletal muscle injury in which intracellular contents are released into extracellular space and plasma. The condition may result from drug or alcohol overdose, infection, crush injuries, collagen disease, or intensive exercise. We report two cases of acute rhabdomyolysis resulting from CO poisoning and alcohol overdose, and discuss the MRI and ultrasonographic findings.

Proliferative Myositis: A Case Report

We report a case of proliferative myositis arising in the pectoralis major muscle of a 59-year-old man who presented with palpable mass. The initial clinical impression was a malignant tumor. Ultrasonography revealed the lesion as a spindle-shaped hypoechoic mass, and MR imaging of the left pectoralis major muscle showed hypointensity at T1-weighted imaging, hyperintensity at T2-weighted imaging, and strong enhancement at contrast-enhanced T1-weighted imaging.

Anterior Interosseous Nerve Syndrome with Varient Nerve Innervation: A Case Report

Anterior interosseous nerve syndrome is characterized by weakness of the flexor pollicis longus, the flexor digitorum profundus and the pronator quadratus in the presence of normal sensation. Although MR imaging findings of anterior interosseous nerve syndrome has been reported in a few articles, we report herein a case of anterior interosseous nerve syndrome involving more than usual muscles innervated by anterior interosseous nerve, caused by varient nerve innervation.

MR Imaging of Skeletal Muscle Injury in Rabbit: Comparison bet ween Diffusion and T2-weighted MR Images

PURPOSE: The purpose of this study was to apply the diffusion-weighted MR imaging technique to the early detection of skeletal muscle injury and to evaluate the usefulness of this imaging sequence. MATERIALS AND METHODS: Thirty rabbits, divided into two groups, were included in this study. Skeletal muscle injury was experimentally induced in the right thigh muscles of each rabbit by clamping with a hemostat for one minute. Four-stage clamping was applied to the rabbits in group I, but for group II there was only one stage. Diffusion and T2-weighted MR images were obtained using a 1.5T MR unit. Serial 5-and 30-minute, and 2-, 24-, and 48- hour delayed images were obtained after injury. The initial time of signal intensity change was recorded and the signal intensities of the injured sites and corresponding normal sites were measured and compared. RESULTS: On 5-minute delayed images in group I, diffusion-weighted MR images showed signal intensity changes in injured muscle in all 15 cases, but on T2-weighted images, change was not detected in three cases. In group II, 5-minute delayed T2-weighted images failed to depict the lesion in six cases, but on diffusion-weighted images, all lesions were detected. In addition, one lesion was not detected on 30-minute delayed T2- weighted images. In group II, the sensitivity of lesion detection was significantly higher on diffusion-weighted than on T2-weighted images (p = 0.0169). CONCLUSION: Diffusion-weighted MR imaging was shown to be more sensitive than T2-weighted imaging for the detection of signal intensity changes immediately after artificial injury, especially when this was of a lesser degree. These results suggest that diffusion-weighted MR imaging may be useful for the detection of early stage skeletal muscle injury.

Muscular involvement by Malignant Lymphoma: CT and MR Findings

PURPOSE: To investigate the CT and MR findings of muscular involvement by malignant lymphoma. MATERIALS AND METHODS: Thirteen patients with biopsy-proved muscular involvement by malignant lymphoma were included in this study. Two patients were primary muscle lymphoma and 11 patients were muscle lymphoma by secondary involvement of malignant lymphoma. CT of 10 patients (6 pre-contrast CT and 9 post-contrast CT) and MRI of 6 patients (all with pre- and post-contrast studies) were retrospectively analyzed. RESULTS: In the majority of patients (84.6%, 11/13), the appearance of muscular involvement was the diffuse enlargement of several muscles as like as a group. The muscles involved by malignant lymphoma showed isoattenuation (5/6) and homogeneity (6/6) on pre-contrast CT scan, and high attenuation (5/9) or iso-attenuation (4/9) and homogeneity (7/9) on post-contrast CT scan. The signal intensity of involved muscle showed slightly hyper- (4/6) or iso-intense (2/6) and homogeneous (6/6) on T1-weighted images, and hyper-intense (6/6) and homogeneous (4/6) on T2- and Gadolinium-enhanced T1-weighted images. Adjacent bone change was demonstrated in 69.2% (9/13), subcutaneous fat change in 61.5% (8/13), and neurovascular encasement within involved muscle in 53.8% (7/13). CONCLUSION: The CT and MR findings of muscular involvement by malignant lymphoma were diffuse enlargement of several muscles with homogeneous attenuation or signal intensity, and frequent changes in adjacent bones and subcutaneous fat, or neurovascular encasement.

Nodular Type of Muscular Sarcoidosis: A Case Report

Muscular involvement of sarcoidosis is rare and occurs in two forms: nodular and myopathic. In the nodular variety, lesions are long and extend along muscle fibers. Axial MR imaging reveals a star-shaped central structure of decreased signal intensity. Sagittal and coronal MR images show three stripes: an inner stripe of decreased signal intensity and outer stripes of increased signal intensity. Longitudinal sonography shows an echogenic inner stripe and hypoechoic outer stripes. We report a case of nodulartype muscular sarcoidosis in a 53-year-old man, describing the findings of MRI and ultrasonography.

MR Findings of Polymyositis/Dermatomyositis

PURPOSE: The purpose of this study was to evaluate the MR findings and useful sequences inPolymyositis/Dermatomyositis, and to correlate MR findings with disease activity. MATERIALS AND METHODS: The studyincluded nine clinically proven cases of Polymyositis/Dermatomyositis, eight involving the thigh and one, theshoulder (2 cases, 1 follow-up). The contrast between affected and normal muscles and difference in signalintensity ratio in the muscle groups were retrospectively evaluated on Gd-enhanced T1WI and T2WI. We alsoevaluated the magnitude of involvement of muscle groups, fatty replacement of muscle and change of subcutaneousfat layer, and correlated signal intensity ratio with serum level of muscle enzymes. Differences in signalintensity ratio and the frequency of chemical shift artifact were evaluated on T2WI as active and inactive groupsclassified according to clinical findings, and the chemicalshift artifact was correlated with the finding ofGd-enhanced T1WI. Exvept in the case of one shoulder, statistical analysis was assessed by the Anova test andt-test. RESULT: On Gd-enhanced T1WI and T2WI contrast was 0.54and 0.82, respectively and p value was 0.02. Withregard to difference in signal intensity ratios of muscle groups, as seen on Gd-enhanced T1WI and T2WI, p valveswere 0.07 and < 0.01, respectively. Muscle involvement was thus clearly visualized on T2WI. The order of frequencyof involved muscle groups was vastus muscles, gluteus maximus, sartorius muscles, adductor muscles, gracilismuscle, and hamstring muscles. Fatty replacement and subcutaneous fatty change were visualized in five cases andone, respectively. The correlation coefficient between the signal intensity seen on T2WI and muscle enzymes was0.59 (CPK) and 0.52 (LDH). The chemical-shift artifact was detected in both clinical groups (four active twoinactive) and corresponded to one case of muscle involvement and five of perimuscular edema, as seen onGd-enhanced T1WI. CONCLUSION: T2WI is useful for the evaluation of muscle involvement and correlated closely withdisease activity; signal intensity ratio could not be substituted for the serum level of muscle enzymes. The groupof thigh muscles most affected was the vastus muscles, while the hamstring muscles were least affected. Thechemical-shift artifact corresponded mainly to perimuscular edema and did not correlate with disease activity.

Magnetic Resonance Imaging of Infectious Myositis

PURPOSE: To describe the findings of magnetic resonance imaging in infectious myositis and to determine theirvalue for differentiation between tuberculous and bacterial myositis. MATERIALS AND METHODS: Magnetic resonanceimages of ten proven cases of infectious myositis, (five tuberculous and five bacterial) were retrospectivelyreviewed in the light of clinical and laboratory findings. On the basis of magnetic resonance images, signalintensity of the mass, the presence or absence of an abscess, signal intensity of the peripheral wall, patterns ofcontrast enhancement, and associated findings were evaluated. RESULTS: Compared with those of bacterial myositis,the symptoms of tuberculous myositis lasted longer but there were no definite local inflammatory signs. In threeof five cases of bacterial myositis there were specific medical records ; trauma in two cases and systemic lupuserythematosus in one. All tuberculous myositis cases involved a single muscle, but bacterial myositis affectedmultiple muscles in three cases(60%). All but one case showed a mass in the involved muscles. In one bacterialcase, there was diffuse swelling in the involved muscle. On T1-weighted images, eight infectious cases showed lowsignal intensity ; two, of the bacterial type, showed subtle increased signal intensity. All cases demonstratedhigh signal intensity on T2-weighted images. The signal intensity of peripheral wall was slightly increased onT1-weighted images, but low on T2-weighted. In four cases there was associated cellulitis, and in one case each,adjacent joint effusion and deep vein thrombosis were seen. After gadolinium infusion, peripheral rim enhancementwas noted in nine cases and heterogeneous enhancement in one. CONCLUSION: After magnetic resonance imaging ofinfectious myositis, the characteristic finding was an abscessed lesion, with the peripheral wall showing highsignal intensity on T1-weighted images and low signal intensity on T2 weighted. Although we found it difficult todifferentiate bacterial from tuberculous myositis, magnetic resonance imaging findings and clinical manifestationsmay help in this respect.

Myositis Ossificans Progressiva: A Report of Two Cases

Myositis ossificans progressiva is rare hereditable disorder characterized progressive heterotopic bone formation in connective tissue and muscles in association with congenital skeletal anomalies. We report the plain radiologic and MR findings of myositis ossificans progressiva in two children. One case showed discrete ossification in the right buttock, neck, and both chest walls on plain radiographs, while the other showed diffuse swelling of the left posterior neck, back, and buttock muscles, which was demonstrated on MR images. Both cases showed associated anomalies in the hands and feet.

MR Imaging of the Denvervated Skeletal Muscles in Rabbits

PURPOSE: To determine the time of magnetic resonance(MR) signal intensity changes in denervated skeletal muscle and to compare MR imaging with electromyography(EMG) in the evaluation of peripheral nerve injury. MATERIALS AND METHODS: We evaluated MR imagings of denervated muscles after experimental transection of the sciatic nerve in five rabbits using 1.0T MR unit. MR imaging and EMG were performed 3 days and 1, 2 and 3 weeks after denervation. T1-weighted images(T1-WI), T2-WI and Short Tau Inversion Recovery(STIR) images were obtained. The signal intensity (SI) of muscles in the denervated and normal sides were visually and quantitatively compared. After measuring the SI of the normal and abnormal areas, the time of SI change was determined when there was significant difference (P<0.05) of SI between the normal and denervated sides. RESULTS: On STIR images, two of the five rabbits showed significant SI changes at the third day(P<0.05) and all showed significant changes(P<0.05)at the first week. On T2-WI, one rabbit showed significant SI changes at the third day, and all showed significant SI changes at the first week. On T1-WI, significant SI changes were seen in one rabbit at the second week and in one at the third. One week after denervation, all showed denervation potential on EMG. CONCLUSION: This study suggests that MR imaging using STIR images is a useful method in the evaluation of denervated muscle, and that MR signal changes of denervated muscle may precede EMG changes after denervation. To localize and to determine the severity of the peripheral nerve injury, future analysis of the distribution of abnormal MR SI in denervated muscles would be helpful.