Basar Sarikaya

Comparison of Test Performance Characteristics of MRI, MR Angiography, and CT Angiography in the Diagnosis of Carotid and Vertebral Artery Dissection: A Review of the Medical Literature

OBJECTIVE Initial assessment of patients with suspected dissection of the carotid or vertebral arteries typically is made by MRI, alone or in combination with MR angiography (MRA) or CT angiography (CTA). We reviewed the medical literature to determine, based on test performance characteristics such as sensitivity, specificity, positive predictive value, and negative predictive value, whether evidence could be found to support routine use of one imaging technique over the other for assessment of suspected dissection. CONCLUSION Test characteristics for MR techniques such as MRI and MRA were relatively similar to those for CTA in diagnosis of carotid and vertebral artery dissection.

Detection of Microhemorrhage in Posterior Reversible Encephalopathy Syndrome Using Susceptibility-Weighted Imaging

Hemorrhage in posterior reversible encephalopathy syndrome occurs in 15-17% of patients but can be underestimated by using conventional MRI. Thus, these authors used SWI to study 31 patients with PRES and found that microbleeds were present in nearly 65% and subarachnoid hemorrhage in 10%. In some patients, microhemorrhages persisted after PRES resolved and in others these developed after its onset. Although the clinical significance of these small bleeds is not known, they could be caused by endothelial cell damage. BACKGROUND AND PURPOSE: PRES-related vasogenic edema is potentially reversible while hemorrhage occurs in only 15.2%–17.3% of patients. However, the true incidence of hemorrhage could be higher when SWI is considered. Thus, we set out to determine the incidence of MH, SAH, and IPH in PRES by using SWI and to particularly evaluate whether such MHs are reversible. MATERIALS AND METHODS: Thirty-one patients with PRES and SWI were included, 17 having follow-up SWI. Two neuroradiologists reviewed SWI, FLAIR, DWI, and CE-T1WI. The presence and number of MHs (<5 mm) on SWI, SAH, and IPH (>5 mm) were recorded at presentation and follow-up. We evaluated associations between the presence of MH on SWI and DWI lesions, SAH, IPH, contrast enhancement, and MR imaging severity. RESULTS: Hemorrhage was present in 20/31 patients (64.5%), with MHs on SWI in 18/31 (58.1%) at presentation and in 11/17 (64.7%) at follow-up. SAH was present in 3/31 on SWI and 4/31 on FLAIR, while 2/31 had IPH. At follow-up, no patients had acquired new MHs; 2/5 MHs in 1 patient resolved. Four patients with available SWI before PRES developed MHs after PRES onset. No association was found between the presence of MHs on SWI and DWI, SAH, IPH, enhancement, and MR imaging severity (all P > .05). CONCLUSIONS: SWI showed a higher rate of MH than previously described, underscoring the potential of SWI in evaluating PRES. Such MHs typically persist and may develop after PRES onset. However, the clinical relevance of MHs in PRES is yet to be determined. We propose that MHs in PRES relate to endothelial cell dysfunction.

Acute Hepatic Encephalopathy: Diffusion-Weighted and Fluid-Attenuated Inversion Recovery Findings, and Correlation with Plasma Ammonia Level and Clinical Outcome

BACKGROUND AND PURPOSE: In acute hepatic encephalopathy, MR imaging abnormalities have been described in the PVWM, thalami, and corticospinal tracts. We sought to determine characteristic regions of involvement on FLAIR and DWI, to evaluate their reversibility, and to correlate MR imaging extent with clinical severity. MATERIALS AND METHODS: Twenty patients who presented clinically with acute hepatic encephalopathy and MR imaging <21 days after symptom onset were reviewed retrospectively. Two neuroradiologists recorded involved regions on FLAIR and DWI in each, measured ADC values in affected regions and NAWM, and scored the MR imaging severity/extent. The initial severity (West Haven grade), follow-up clinical severity (degree of improvement), and maximal PAL within ±8 days of MR imaging were recorded and correlated with the MR imaging severity. RESULTS: On FLAIR and DWI respectively, there were abnormalities in the thalami (85%, 70%), PLIC (75%, 80%), PVWM (80%, 85%), and DBS (70%, 35%) and diffuse cortical involvement (30%, 25%). There were relatively strong significant (P < .005) correlations of FLAIR (r = 0.680, P = .001) and DWI severity (r = 0.690, P = .001) with PAL, and of PAL with the clinical outcome (r = 0.691, P = .001). Both FLAIR (r = 0.592, P = .006) and DWI (r = 0.487, P = .029) severity correlated moderately with the clinical outcome but were not significant at the P < .005 level after Bonferroni correction. CONCLUSIONS: Patients with acute hepatic encephalopathy may exhibit characteristic regions of involvement on FLAIR with DWI findings that can be reversible. The MR imaging extent on FLAIR and DWI strongly correlates with the maximal PAL, and PAL correlates well with the clinical outcome. Diffuse cortical involvement has a higher potential for neurologic sequelae but can be reversible.

Causes of Misinterpretation of Cross-Sectional Imaging Studies for Dissection of the Craniocervical Arteries

OBJECTIVE This review presents some of the more common causes of false-positive and false-negative interpretations of cross-sectional imaging studies showing, or designed to show, dissection of the carotid or vertebral arteries. CONCLUSION Dissection of the craniocervical arteries is a diagnosis that can be very difficult on cross-sectional imaging studies such as CT angiography, MRI, and MR angiography.

Visualization of the biliary tract using gadobenate dimeglumine: preliminary findings.

Objective: To compare contrast-enhanced magnetic resonance (MR) cholangiography (CE-MRC) performed with gadobenate dimeglumine with T2-weighted MRC (T2-MRC) for visualization of the bile ducts in nondilated biliary systems. Materials and Methods: Twenty consecutive patients who underwent MR imaging (MRI) of the liver and pancreas with nondilated intrahepatic ducts were included in this retrospective study. T2-weighted MRC was performed using a multislice, high-resolution fat-suppressed half-Fourier acquisition turbo spin-echo sequence. Contrast-enhanced MR cholangiography was performed using a fat-suppressed 3-dimensional fast low-angle shot sequence acquired 1 to 1.5 hour after intravenous administration of gadobenate dimeglumine. For image interpretation, the biliary system was divided into 8 segments. Two readers graded visualization of each segment on T2-MRC and CE-MRC using a 5-point scale (0, nonvisualization; 4, excellent visualization). Final opinion for each sequence was rendered by consensus. Superiority of visualization was assessed using the McNemar test and comparing adequately (visualization scores 3 and 4) and inadequately (visualization scores 0, 1, and 2) visualized segments of the ducts on both sequences. Interobserver variability was assessed with &kgr; statistics. Results: Overall and segment-based evaluation revealed superior visualization of biliary segments with CE-MRC compared with T2-MRC. We also found a statistically significant difference between the 2 sequences for overall and for right hepatic duct and cystic channel visualization (P < 0.05). A high concordance between readers 1 and 2 both for T2-MRC and CE-MRC was achieved (85.8% and 89.4%, respectively). Conclusions: Gadobenate dimeglumine can be used as an alternative intrabiliary contrast agent for contrast-enhanced MR cholangiography in nondilated biliary systems in patients with normal excretory liver function tests.

Diffusion-Tensor Imaging Assessment of White Matter Maturation in Childhood and Adolescence

OBJECTIVE The purpose of this study was to test a first hypothesis that fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values continue to change in late childhood and adolescence and a second hypothesis that less mature white matter (WM) regions have a higher rate of change than WM regions that are relatively more mature. SUBJECTS AND METHODS Eighty-seven healthy children (50 girls, 37 boys; mean age, 11.2 ± 3.6 years; range, 4.2-17.7 years) underwent six-direction diffusion-tensor imaging with a 3-T MRI system. Three neuroradiologists independently drew regions of interest in 10 WM regions and measured FA and ADC values. To test the first hypothesis, we correlated these values with subject age by linear regression analysis (p < 0.05). To test the second hypothesis, we determined whether regions with lower FA and higher ADC in the 4- to 7-year old group had a higher slope of FA increase and ADC decrease over the entire age range. For this assessment, we used linear regression analysis (p < 0.05) and curve fitting. RESULTS In the test of the first hypothesis, increases in FA with age were noted in all WM regions and were statistically significant in six regions. Decreases in ADC values with age were noted in all brain regions except the genu of the corpus callosum. In all other regions except the splenium of the corpus callosum, the decreases were statistically significant. In the test of the second hypothesis, the relation between FA in the 4- to 7-year-old subjects and the FA increase in the entire sample was best described with a linear equation. The rate of age-related FA increase tended to be greater with lower initial FA (r = -0.384, p = 0.271). The relation between ADC in the 4- to 7-year-old subjects and ADC decrease in the entire population was best described with a second-order equation. The rate of age-related ADC decrease tended to be greater with higher initial ADC (r = 0.846, p = 0.001). For ADC values of 100 or less at age 4-7 years, the rate of ADC change with age tended to be decrease as initial ADC increased. CONCLUSION In general, both hypotheses were verified. Overall, FA values continue to increase and ADC values continue to decrease during childhood and adolescence. The most rapid changes were found in WM regions that were least mature in the first few years of the study period.

Acute Hepatic (or Hyperammonemic) Encephalopathy: Diffuse Cortical Injury and the Significance of Ammonia

We read with great interest the description by U-King-Im et al[1][1] in the February issue of the American Journal of Neuroradiology ( AJNR ) of 4 patients with “acute hyperammonemic encephalopathy” on diffusion-weighted imaging (DWI). In the September 2010 issue of AJNR , we used a similar term

Not the typical Tornwaldt's cyst this time? A nasopharyngeal cyst associated with canalis basilaris medianus

We report a patient with a cystic structure in the nasopharynx mimicking a Tornwaldts cyst, which was felt to represent a different entity owing to the lack of the distinct features of a typical Tornwaldts cyst. It was associated with a bony cleft in the basiocciput that was considered to be a canalis basilaris medianus (CBM), thought to represent an embryological vestige of the cephalic end of the notochord along its course within the basiocciput.

MR Imaging of Vogt-Koyanagi-Harada Syndrome with Leptomeningeal Enhancement

SUMMARY: We describe a 28-year-old man with presumed VKH syndrome, whose presenting symptoms were bilateral impaired vision and headaches. Orbital MR imaging findings included bilateral choroidal and retrobulbar contrast enhancement, while brain findings included white matter abnormalities on FLAIR and leptomeningeal enhancement. Pachymeningeal enhancement has been described previously; herein, we report a patient with VKH syndrome presenting solely with leptomeningeal enhancement. Thus, MR imaging may detect early CNS involvement by VKH disease before the onset of neurologic symptoms.

The role of the resistive index in Hashimoto's thyroiditis: a Sonographic pilot study in children

OBJECTIVE: The role of Doppler ultrasonography in the diagnosis of diffuse thyroid diseases is not well established. In particular, Doppler ultrasonography findings in children with Hashimotos thyroiditis are very limited. We examined gray-scale and Doppler ultrasound findings in Hashimotos thyroiditis in children in an attempt to understand the feasibility of future prospective controlled studies. MATERIALS AND METHODS: Twenty-one children with newly diagnosed Hashimotos thyroiditis were recruited in the study. The patients were euthyroid or had subclinical hypothyroidism at the time of the ultrasonography examination. According to the color Doppler scale developed by Schulz et al., thyroid glands were classified into four patterns based on visual scoring and the mean resistive index (RI), which was calculated via measurements from both lobes, and these results were compared with gray-scale findings. RESULTS: The mean RI value, calculated as the mean of the RI values of both lobes obtained from each patient, was found to be 0.57±0.05 (range 0.48-0.67) cm/sn. The distribution of thyroid classifications was as follows: Pattern 0, n = 7; Pattern I, n = 6; Pattern II, n = 4; and Pattern III (“thyroid inferno”), n = 4. The mean RI values in patients with normal or near-normal gray-scale findings (n = 10) and patients with more substantial gray-scale changes (n = 11) were not significantly different and were lower than the values in normal children previously presented in the literature. CONCLUSION: The results indicated that the RI may be more sensitive than other ultrasound parameters for the diagnosis of Hashimotos thyroiditis.