藤井 裕之

Acetabular fractures are usually caused by high-energy trauma, and seizure-induced cases resulting from strong muscle contractions are extremely rare. We report the case of a 90-year-old man with osteoporosis who incurred a nontraumatic acetabular fracture during a seizure. Computed tomography revealed an internal iliac artery injury, which was promptly treated with transcatheter arterial embolization. As such vascular injuries, though rare, require early diagnosis and treatment, radiologists must be aware of the associated imaging findings and management, particularly in cognitively impaired patients.

BACKGROUND AND PURPOSE: Bell's palsy (BP) is the most common cause of facial nerve (FN) palsy. This study aimed to investigate the diagnostic ability of the 3D Double-Echo Steady-State with Water Excitation (3D-DESS-WE) sequence to visualize pathological changes in the FN of BP patients. MATERIALS AND METHODS: We retrospectively analyzed 30 BP patients who underwent 3T MRI including 3D-DESS-WE within 30 days of onset and 60 sex-and age±2-matched controls. Qualitative evaluation of FN signal intensity (SIFN) and thickness (THFN) was performed using a 3-point scale. Quantitative metrics included SIFN and THFN measurements and affected-to-unaffected ratios (SRA/U and TRA/U) in the BP group, and right-to-left ratios in controls. Interobserver agreement, group comparisons, correlations with clinical severity (Yanagihara score), and diagnostic performance were assessed. In a subset of 17 matched pairs, the diagnostic performance of contrast-enhanced T1WI (CE-T1WI) was assessed, and its agreement with 3D-DESS-WE-based qualitative assessment was evaluated. RESULTS: Qualitative scores for SIFN and THFN were significantly higher in the BP group than in controls (P < .001), with high interobserver agreement (κ = 0.810, 0.788, respectively). When dichotomized (score 0 vs. 1-2), qualitative assessments showed good diagnostic performance with sensitivity and specificity of 0.87 and 0.82 for SIFN, and 0.90 and 0.80 for THFN, respectively. Neither qualitative score correlated significantly with clinical severity. Agreement between 3D-DESS-WE-based and CE-T1WI-based qualitative assessments was substantial to almost perfect (κ = 0.766-0.882). In quantitative analysis, both SIFN and THFN were significantly higher on the affected side in the BP group (P < .001), whereas no significant lateral differences were observed in controls. Although SIFN, THFN, and SRA/U did not correlate significantly with clinical severity, TRA/U was significantly inversely correlated with the Yanagihara score (r = -0.413, P = .02), which corresponds to a positive correlation with clinical severity. The Yanagihara score was the only independent predictor for TRA/U in multiple regression analysis (β = -0.425, P = .04). ROC analysis showed high diagnostic performance: AUC = 0.908 for SRA/U and 0.927 for TRA/U. CONCLUSIONS: 3D-DESS-WE may be a valuable tool for the routine clinical assessment of BP. ABBREVIATIONS: 3D-DESS-WE＝3D Double-Echo Steady-State with Water Excitation; 3D-PSIF＝3D reversed fast imaging in steady-state free precession.

We report a rare case of squamous cell carcinoma (SCC) arising from a subcutaneous epidermoid cyst in the buttock of an 80-year-old man who presented with a painful mass. MRI revealed a well-defined subcutaneous mass, measuring approximately 10 cm, in the medial aspect of the left buttock, which exhibited internal features typical of an epidermoid cyst. However, MRI also demonstrated a significant finding: a 45-mm solid mural component protruding into the cyst. This solid component exhibited mild high signal intensity on T2-weighted images and heterogeneous signal intensity on DWI, differing from the cystic portion. Color Doppler ultrasound demonstrated internal blood flow within this solid component. Crucially, this solid component was absent on a CT scan performed 2 years prior. Resection and subsequent pathological examination confirmed well-differentiated squamous cell carcinoma (SCC) arising from the epidermoid cyst. This case highlights the importance of considering malignant transformation in epidermoid cysts, especially when imaging findings such as interval development of a solid mural component and internal vascularity are observed.

PURPOSE: To examine magnetic resonance imaging (MRI) features of mesonephric-like adenocarcinoma (MLA) of the uterine corpus. METHOD: MRI features of 19 patients with pathologically proven MLA of the uterine corpus were retrospectively compared with those of 95 patients with endometrial endometrioid carcinoma (EEC). RESULTS: Most patients with MLA were postmenopausal. Advanced FIGO stages were more common in the MLA than in the EEC group (63.2 % vs. 18.9 %, p < 0.001). On MRI, endophytic growth into the myometrium were more frequent in the MLA than in the EEC group (68.4 % vs. 14.7 %, p = 0.005). The median maximum tumor diameter in the MLA group (52.4 mm) tended to be larger than that in the EEC group (38.9 mm), although the difference was not statistically significant (p = 0.374). The tumor-to-muscle signal intensity ratio (SIR) on fat-suppressed gadolinium-enhanced T1-weighted gradient-echo imaging was higher in the MLA group than in the EEC group. (1.67 vs. 1.36, p = 0.002). The SIR on diffusion-weighted imaging (DWI) was comparable between the two groups (8.35 vs. 6.72, p = 0.330). The apparent diffusion coefficient value was lower in the MLA than in the EEC group (0.69 10-3 mm2/s vs. 0.76 × 10-3 mm2/s, p = 0.003). Coexisting adenomyosis was more frequent in the MLA than in the EEC group (52.6 % vs. 21.1 %, p = 0.034). The concordance rate between MRI and pathology for adenomyosis coexistence was 84.2 % for MLA, 87.4 % for EEC, and 86.8 % overall. MLA of the uterine corpus was identified in two patients, characterized by development independent of and discontinuous from the endometrium, whereas EEC in all patients demonstrated continuity with the endometrium. CONCLUSIONS: MRI of MLA of the uterine corpus typically demonstrates large, diffuse, and endophytic growth into the myometrium, with strong contrast enhancement and more restricted diffusion compared to EEC, with coexisting adenomyosis present in over 50% of patients. Therefore, postmenopausal women with adenomyosis should be carefully evaluated for MLA on MRI, particularly using DWI.

We report a case of a man in his 60s with ROS1 fusion-positive lung adenocarcinoma who developed multiple cystic lesions in both the kidneys and liver during crizotinib treatment. The patient presented with fever, abdominal pain, and oliguria. Contrast-enhanced CT revealed new cystic lesions in both the kidneys and liver, with some showing thick walls, septa, and hyperdense contents. MRI demonstrated heterogeneous signal intensities on T2-weighted images and mixed low to high signal intensities on T1-weighted images. Some cysts displayed T2 hypointense and T1 hyperintense areas along the cyst walls, with diffusion restriction predominantly at the periphery of the masses. Percutaneous drainage of the cysts was performed, and cytology revealed an increase in the number of cells, including neutrophils. However, no malignant cells or microorganisms were detected. Based on these imaging findings and laboratory results, the patient was diagnosed with crizotinib-associated renal and hepatic cysts. Symptoms improved after crizotinib discontinuation, and follow-up imaging showed cyst regression. This is the first report describing MRI findings for crizotinib-associated hepatic cysts. Characteristic MRI findings, such as T2 hypointensity/T1 hyperintensity along the cyst walls and diffusion restriction predominantly at the periphery of the masses, suggesting hemorrhagic components, may help differentiate crizotinib-associated cysts from other lesions, including metastases and abscesses.