Myung Kwan Lim

Can Necrotizing Infectious Fasciitis Be Differentiated from Nonnecrotizing Infectious Fasciitis with MR Imaging

PURPOSE To retrospectively evaluate whether magnetic resonance (MR) imaging findings can be used to differentiate necrotizing infectious fasciitis (NIF) from nonnecrotizing infectious fasciitis (non-NIF). MATERIALS AND METHODS Institutional review board approval was obtained, but patient consent was not required for this retrospective review of records and images because patient anonymity was preserved. Thirty patients (seven with NIF, 23 with non-NIF) were included in the study. The following imaging findings were analyzed on fat-suppressed T2-weighted MR images: (a) signal intensity in the deep fascia (low, high, or mixed high and low), (b) thickness of abnormal signal intensity in the deep fascia (≥3 mm or <3 mm), (c) pattern of abnormal signal intensity in muscle (no abnormality, peripheral bandlike signal intensity, or patchy high signal intensity), (d) degree of deep fascia involvement (partial or extensive), and (e) degree of compartment involvement (fewer than three compartments or three or more compartments). On contrast material-enhanced fat-suppressed T1-weighted images, the contrast enhancement patterns of the abnormal deep fascia (no enhancement, enhancement, or enhancement with nonenhancing portion) and the muscle (no abnormality, peripheral bandlike signal intensity, or patchy high signal intensity) were evaluated. The presence of abscesses in the subcutaneous fat layer was evaluated with all sequences. RESULTS The patients with NIF had a significantly greater frequency of (a) thick (≥3 mm) abnormal signal intensity on fat-suppressed T2-weighted images, (b) low signal intensity in the deep fascia on fat-suppressed T2-weighted images, (c) a focal or diffuse nonenhancing portion in the area of abnormal signal intensity in the deep fascia, (d) extensive involvement of the deep fascia, and (e) involvement of three or more compartments in one extremity (P < .05). CONCLUSION MR imaging is potentially helpful for differentiating NIF from non-NIF. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101164/-/DC1.

Acute necrotizing encephalopathy in Korean infants and children: imaging findings and diverse clinical outcome.

Objective The purpose of our study was to describe acute necrotizing encephalopathy in Korean infants and children, and we sought to evaluate the prognostic factors. Materials and Methods Acute necrotizing encephalopathy was diagnosed in 14 Korean infants and children. We retrospectively analyzed the neuroimaging findings including the follow-up changes. The clinical course of the disease was graded, and we evaluated prognostic factors including age, serum level of the aminotransferase, hemorrhage, and localized atrophy of the brain. Results This encephalopathy predominantly affected the bilateral thalami (n=14), pons (n=12), and midbrain (n=10) in a symmetrical pattern. Hemorrhage was observed in eight patients (57%). On the follow-up images (n=12), the brain lesions were reduced in extent for all patients, and generalized atrophy was seen in six patients. Localized tissue loss was observed in five patients and a complete resolution occurred for one patient. All the patients survived and two recovered completely; mild (n=6) to severe (n=6) neurological deficits persisted in the remaining 12 patients. The significant prognostic factors identified in this study were the presence of hemorrhage (p = 0.009) and localized atrophy (p = 0.015). Conclusion Acute necrotizing encephalopathy in Korean patients showed the characteristic patterns of the post-infectious encephalopathy as described in the literature. The high survival rate and the relatively favorable clinical course observed for the present study suggest a more diverse spectrum of disease severity than was previously described. The presence of hemorrhage and localized tissue loss on MR images may suggest a poor prognosis.

Diffusion and Perfusion Characteristics of MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-Like Episode) in Thirteen Patients

Objective We analyzed the diffusion and perfusion characteristics of acute MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode) lesions in a large series to investigate the controversial changes of the apparent diffusion coefficient (ADC) that were reported in prior studies. Materials and Methods We analyzed 44 newly appearing lesions during 28 stroke-like episodes in 13 patients with MELAS. We performed a visual assessment of the MR images including the ADC and perfusion maps, comparison of the ADC between the normal and abnormal areas, comparison of % ADC between the 44 MELAS lesions and the 30 acute ischemic infarcts. In addition, the patterns of evolution on follow-up MR images were analyzed. Results Decreased, increased, and normal ADCs were noted in 16 (36%), 16 (36%), and 12 (27%) lesions, respectively. The mean % ADC was 102 ± 40.9% in the MELAS and 64 ± 17.8% in the acute vascular infarcts (p < 0.001), while perfusion imaging demonstrated hyper-perfusion in six acute MELAS lesions. On follow-up images, resolution, progression, and tissue loss were noted in 10, 4, and 17 lesions, respectively. Conclusion The cytotoxic edema gradually evolves following an acute stroke-like episode in patients with MELAS, and this may overlap with hyper-perfusion and vasogenic edema. The edematous swelling may be reversible or it may evolve to encephalomalacia, suggesting irreversible damage.

Abnormal thalamic volume in treatment‐naïve boys with Tourette syndrome

Objective:  Thalamic abnormality has been implicated in the pathophysiology of Tourettes syndrome (TS). We examined the presence of aberrant thalamic volume from the treatment‐naïve boys with TS using magnetic resonance imaging (MRI).

Granulocytic Sarcoma in the Head and Neck: CT and MR Imaging Findings

Objectives To evaluate characteristic computed tomography (CT) and magnetic resonance (MR) imaging findings of granulocytic sarcomas of the head and neck. Methods The CT (n=11) and MR (n=1) images obtained from 11 patients (7 males and 4 females; mean age, 23.5 yr; age range, 1 to 69 yr) with histologically-proven granulocytic sarcomas of the head and neck were retrospectively reviewed. Histological confirmation was done by bone marrow biopsy in 9 patients, and/or local biopsy in 4 patients. The imaging findings were analyzed with particular attention to location, size, shape, margin, bone destruction, internal architecture, pattern and degree of enhancement, and multiplicity of the lesions. Results The masses were most commonly located in the orbital cavity (n=8); other locations included lymph nodes (n=5) and palatine/pharyngeal/lingual tonsils (n=3). The mass sizes varied from a mean diameter of 1.3 to 5.8 cm (average, 2.6 cm). Multiple lesions were found in 6 patients. The shapes of the tumors were ovoid in 12 patients and irregular in 4 patients. Most lesions had poorly-defined margins (13/16) and invaded adjacent bony structures (5/16). On the pre-contrast CT images, the masses were iso- (5/8) or low-density (3/8) in comparison with muscle. The MRI, which was obtained in one patient in this study, showed that the mass was iso-signal intensity on T1-weighted images and iso-signal intensity on T2-weighted images compared to the gray matter of the brain. On the post-contrast CT images, there was homogenesous (n=12) or heterogeneous (n=4) enhancement, with mild (n=10), moderate (n=4), and marked (n=2) enhancement in the solid portions of the lesions. Conclusion Although rare, granulocytic sarcomas arise in various locations in the head and neck area (most commonly in the orbit) in the form of well-demarcated, and mildly- and homogenously-enhancing masses with adjacent bony invasion.

MR Imaging in a Child with Scurvy: a Case Report

Scurvy is very rare disease in industrialized societies. Nevertheless, it still exists in higher risk groups including economically disadvantaged populations with poor nutrition, such as the elderly and chronic alcoholics. The incidence of scurvy in the pediatric population is very low. This study reports a case of scurvy in a 5-year-old girl with cerebral palsy and developmental delay based on MRI findings.

In-vivo Proton Magnetic Resonance Spectroscopy in Adnexal Lesions

Objective To explore the in-vivo 1H- MR spectral features of adnexal lesions and to characterize the spectral patterns of various pathologic entities. Materials and Methods Thirty-one patients with surgically and histopathologically confirmed adnexal lesions underwent short echo-time STEAM (stimulated echo acquisition method) 1H- MR spectroscopy, and the results obtained were analysed. Results The methylene present in fatty acid chains gave rise to a lipid peak of 1.3 ppm in the 1H- MR spectra of most malignant tumors and benign teratomas. This same peak was not observed, however, in the spectra of benign ovarian epithelial tumors: in a number of these, a peak of 5.2 ppm, due to the presence of the olefine group (-CH=CH-) was noted. The ratios of lipid peak at 1.3 ppm to water peak (lipid/water ratios) varied between disease groups, and in some benign teratomas was characteristically high. Conclusion An intense lipid peak at 1.3 ppm is observed in malignant ovarian tumors but not in benign epithelial tumors. 1H- MRS may therefore be helpful in the differential diagnosis of adnexal lesions.

Computed tomography and magnetic resonance imaging findings of nasal cavity hemangiomas according to histological type.

Objective To compare computed tomography (CT) and magnetic resonance imaging (MRI) findings between two histological types of nasal hemangiomas (cavernous hemangioma and capillary or lobular capillary hemangioma). Materials and Methods CT (n = 20; six pre-contrast; 20 post-enhancement) and MRI (n = 7) images from 23 patients (16 men and seven women; mean age, 43 years; range, 13-73 years) with a pathologically diagnosed nasal cavity hemangioma (17 capillary and lobular capillary hemangiomas and six cavernous hemangiomas) were reviewed, focusing on lesion location, size, origin, contour, enhancement pattern, attenuation or signal intensity (SI), and bony changes. Results The 17 capillary and lobular hemangiomas averaged 13 mm (range, 4-37 mm) in size, and most (n = 13) were round. Fourteen capillary hemangiomas had marked or moderate early phase enhancement on CT, which dissipated during the delayed phase. Four capillary hemangiomas on MRI showed marked enhancement. Bony changes were usually not seen on CT or MRI (seen on five cases, 29.4%). Half of the lesions (2/4) had low SI on T1-weighted MRI images and heterogeneously high SI with signal voids on T2-weighted images. The six cavernous hemangiomas were larger than the capillary type (mean, 20.5 mm; range, 10-39 mm) and most had lobulating contours (n = 4), with characteristic enhancement patterns (three centripetal and three multifocal nodular), bony remodeling (n = 4, 66.7%), and mild to moderate heterogeneous enhancement during the early and delayed phases. Conclusion CT and MRI findings are different between the two histological types of nasal hemangiomas, particularly in the enhancement pattern and size, which can assist in preoperative diagnosis and planning of surgical tumor excision.

Repeat Fine-Needle Aspiration Biopsy within a Short Interval Does Not Increase the Atypical Cytologic Results for Thyroid Nodules with Previously Nondiagnostic Results.

Objective: The purpose of this study was to determine whether the recommended waiting period of 3 months is necessary for repeat fine-needle aspiration biopsy (FNAB). Study Design: A retrospective review of 128 nodules from 126 patients with initial nondiagnostic (ND) results was performed for the period between January 2009 and December 2012. Demographic and clinical factors were recorded including age, sex, time interval between FNABs, and ultrasound (US) factors, i.e. nodule size, location, consistency, suspicious malignant findings and thyroiditis. The time interval was subdivided into </≥5, 10, 15 and 20 weeks after the initial FNAB. The effects on the nuclear atypia were analyzed using the Fisher exact test and the Mann-Whitney U test. Results: None of the demographic, clinical or US variables was significantly related to the atypical diagnosis of repeat FNAB. The time interval until repeat FNAB was also not related to the atypical diagnosis (p = 0.63, 0.57, 0.23 and 0.48 for 5, 10, 15 and 20 weeks, respectively). Conclusion: The timing of repeat FNAB for thyroid nodules with previous ND results did not increase the nuclear atypia on repeat FNAB.

Brain stem hypoplasia associated with Cri-du-Chat syndrome.

Cri-du-Chat syndrome, also called the 5p-syndrome, is a rare genetic abnormality, and only few cases have been reported on its brain MRI findings. We describe the magnetic resonance imaging findings of a 1-year-old girl with Cri-du-Chat syndrome who showed brain stem hypoplasia, particularly in the pons, with normal cerebellum and diffuse hypoplasia of the cerebral hemispheres. We suggest that Cri-du-Chat syndrome chould be suspected in children with brain stem hypoplasia, particularly for those with high-pitched cries.