Altered Signal Intensity Research Articles

Multidetector Computerized Tomography Versus Magnetic Resonance Imaging in Diagnosis of Basal Ganglia Signal Intensity Alteration

Multidetector Computerized Tomography Versus Magnetic Resonance Imaging in Diagnosis of Basal Ganglia Signal Intensity Alteration

Interesting MRI finding in SSPE – a case report

Introduction: 10% of the subacute sclerosing panencephalitis (SSPE) presents with atypical features. Aim: SSPE is rare chronic encephalitis caused by persistent infection with defective measles virus. Characteristic MRI findings include signal changes (T2W and FLAIR hyperintensities) in bilateral occipital and parietal regions involving both gray and white matter. Early involvement of cerebellum and brainstem is not common. Case study: A 17-year-old male presented with complaints of recurrent seizures, slow walking, and behavioral abnormality. Neurological examination revealed cogwheel rigidity in all four limbs. MRI of the brain revealed asymmetrical cortical and subcortical altered signal intensities (T2W and FLAIR hyperintensity and T1W hypointensity) involving temporal and occipital lobes bilaterally (left more than right) with diffuse atrophy of cerebrum and cerebellum. Results and discussion: Early onset extrapyramidal features, seizures without myoclonus with MRI finding of posterior predominant asymmetrical cortical and subcortical signal abnormality is uncommon in SSPE. Conclusions: A high index of clinical suspicion for SSPE has to be maintained in patients haling from endemic areas, unvaccinated individuals presenting with seizures, behavioral abnormality, and extrapyramidal features.

Quantitative Signal Intensity Alteration in Infrapatellar Fat Pad Predicts Incident Radiographic Osteoarthritis: The Osteoarthritis Initiative.

To determine whether infrapatellar fat pad (IPFP) signal intensity measures are predictive of incident radiographic osteoarthritis (ROA) over 4 years in the Osteoarthritis Initiative study. Case knees (n = 355), as defined by incident ROA, were matched 1:1 with control knees, according to sex, age, and radiographic status. T2-weighted magnetic resonance images were assessed at P0 (the visit when incident ROA was observed on a radiograph), P1 (1 year prior to P0), and baseline and used to assess IPFP signal intensity semiautomatically. Conditional logistic regression analyses were performed to assess the risk of incident ROA associated with IPFP signal intensity alteration, after adjustment for covariates. The mean age of the participants was 60.2 years, and most (66.7%) were female and overweight (mean body mass index 28.3 kg/m2 ). Baseline IPFP measures including the mean value and standard deviation of IPFP signal intensity, the mean value and standard deviation of IPFP high signal intensity, median and upper quartile values of IPFP high signal intensity, and the clustering effect of high signal intensity were associated with incident knee ROA over 4 years. All P1 IPFP measures were associated with incident ROA after 12 months. All P0 IPFP signal intensity measures were associated with ROA. The quantitative segmentation of high signal intensity in the IPFP observed in our study confirms the findings of previous work based on semiquantitative assessment, suggesting the predictive validity of semiquantitative assessment of IPFP high signal intensity. The IPFP high signal intensity alteration could be an important imaging biomarker to predict the occurrence of ROA.

45 Threshold dose for focal liver reaction

Purpose Patient who underwent liver stereotactic body radiation therapy (SBRT) show a signal intensity alteration in follow-up imaging known as focal liver reaction (FLR). This study aims at evaluating dose threshold for FLR after SBRT. Methods 22 patients (13 metastasis, 9 hepatocellular carcinomas [hcc]) underwent SBRT with 48 or 60 Gy in 3 fractions. After therapy patients had, according to clinical protocols, follow-up imaging studies (12 CT and 32 MRI) at 3, 6, 9, 12, 18, 24 and 30 months. For each follow-up the region of signal alteration, if present, was classified as FLR, residual or recurrent disease, and contoured. In case of FLR, the planning images were registered to the follow up using deformable registration, and planning dose was mapped to the follow up applying the registration matrix. The isodose that better fits the FLR (dose threshold) was found, and the conformality index between dose threshold and FLR computed. The figure shows the dose threshold as a function of cancer type and follow up time. Results Threshold dose is higher for metastasis than for hcc (8 Gy at 3–6 months, 12 Gy at 9–12 months), and shows an increase up to 9 months followed by a decrease at 12 month. Cases at 18 or more months are too few or broad to be significant. The table shows threshold doses with their uncertainties – cases with just one samples are excluded. Conclusions hcc’s show FLR for lower doses, which can be justified by pre-existing cirrhosis. Since higher isodoses are embedded in lower ones, follow-up lesion size has an inverse correlation with dose threshold; therefore, there is a decrease of the lesion in the first 9 months followed by an increase 3 months later. Threshold doses are consistent with literature data.

52. Image registration for focal liver reaction evaluation

Purpose Patient who underwent stereotactic body radiation therapy (SBRT) for liver cancer show a signal intensity alteration in follow-up imaging known as focal liver reaction (FLR). Accurate image registration between planning and follow-up imaging is crucial for estimating relationship between planned dose and radiation-induced FLR. This study aims to compare three different strategies of imaging for follow-up studies. Methods 22 patients (13 metastasis, 9 hepatocellular carcinomas [hcc]) underwent SBRT with an abdominal compressor. After therapy patients had follow-up studies at 3, 6, 9, 12, 18, 24 and 30 months. Imaging was performed using either CT (12 cases), MRI with a water-only Dixon sequence (34 cases) or MRI with a T1-weighted, fat-suppressed sequence (19 cases). For each follow-up the liver was contoured and the planning images were registered to the follow up using deformable registration. The registration quality was evaluated by computing the conformal index between the liver in the two image sets. Results the figure shows the computed conformal indices as a function if the follow-up imaging type. The overall average value is 90% (range 79–94%), and CT images have less variability compared to MRI’s. An ANOVA analysis does not show any statistically significant difference between the three imaging modalities (p = 0.06). Conclusions The average registration quality is not optimal, with any image type used. The main reason is the amount of distortion caused by the abdominal compressor used for immobilization in treatment planning and delivery. Beside this issue, the three different methods of follow-up imaging can be registered to the planning CT with similar results. Therefore, the imaging modality that allows better delineation of FLR can be safely chosen for follow-ups. Moreover, MRI can be chosen over CT to avoid unjustified use of ionizing radiation.

T1-weighted Grey Matter Signal Intensity Alterations After Multiple Administrations of Gadobutrol in Patients with Multiple Sclerosis, Referenced to White Matter

The aim of the study was to investigate the signal-intensity-(SI)-ratio changes in the basal ganglia, the pulvinar thalami (PN), and the dentate nucleus (DN) using frontal white matter (FWM) as reference area, in patients with multiple sclerosis after frequent administrations of gadobutrol. A control group (group I) was compared to three stratified patient groups (group II: mean applications of gadobutrol 3.7; group III: 7.5 applications; group IV: 13.8 applications). SI-ratios of the pallidum, putamen, caudate nucleus, and pulvinar thalami were calculated with: 1. FWM, and 2. PN. DN-to-pons and DN-to-FWM ratios were also calculated. The most significant SI-ratio-changes were found by comparing group I and IV for both reference values. However, by using FWM as reference an SI-ratio increase was observed, while an SI-ratio decrease was seen if referenced to the PN. DN-to-FWM showed an SI-ratio increase, too. The PN revealed a significant SI-ratio increase itself, correlating with the number of gadolinium applications, when referenced to FWM. Therefore, SI-ratio calculations using the thalamus as reference might be flawed. In addition, a minor gadolinium accumulation is possible, if FWM was used as reference area. Further studies are necessary to verify our results.

Gadolinium Exposure in Multiple Sclerosis: Evaluation of Unenhanced-t1 Images Signal Intensity Alterations in the Dentate Nucleus and the Globus Pallidus

Gadolinium Exposure in Multiple Sclerosis: Evaluation of Unenhanced-t1 Images Signal Intensity Alterations in the Dentate Nucleus and the Globus Pallidus

Effusion-synovitis and infrapatellar fat pad signal intensity alteration differentiate accelerated knee osteoarthritis

To determine whether greater effusion-synovitis volume and infrapatellar fat pad (IFP) signal intensity alteration differentiate incident accelerated knee OA (KOA) from a gradual onset of KOA or no KOA. We classified three sex-matched groups of participants in the Osteoarthritis Initiative who had a knee with no radiographic KOA at baseline (recruited 2004-06; Kellgren-Lawrence <2; n = 125/group): accelerated KOA: ⩾1 knee progressed to Kellgren-Lawrence grade ⩾3 within 48 months; common KOA: ⩾1 knee increased in radiographic scoring within 48 months; and no KOA: both knees had the same Kellgren-Lawrence grade at baseline and 48 months. The observation period included up to 2 years before and after when the group criteria were met. Two musculoskeletal radiologists reported presence of IFP signal intensity alteration and independent readers used a semi-automated method to segment effusion-synovitis volume. We used generalized linear mixed models with group and time as independent variables, as well as testing a group-by-time interaction. Starting at 2 years before disease onset, adults who developed accelerated KOA had greater effusion-synovitis volume than their peers (accelerated KOA: 11.94 ± 0.90 cm3, KOA: 8.29 ± 1.19 cm3, no KOA: 8.14 ± 0.90 cm3) and have greater odds of having IFP signal intensity alteration than those with no KOA (odds ratio = 2.07, 95% CI = 1.14-3.78). Starting at 1 year prior to disease onset, those with accelerated KOA have greater than twice the odds of having IFP signal intensity alteration than those with common KOA. People with IFP signal intensity alteration and/or greater effusion-synovitis volume in the absence of radiographic KOA may be at high risk for accelerated KOA, which may be characterized by local inflammation.

Multimodal computational neocortical anatomy in pediatric hippocampal sclerosis.

ObjectiveIn contrast to adult cohorts, neocortical changes in epileptic children with hippocampal damage are not well characterized. Here, we mapped multimodal neocortical markers of epilepsy‐related structural compromise in a pediatric cohort of temporal lobe epilepsy and explored how they relate to clinical factors.MethodsWe measured cortical thickness, gray–white matter intensity contrast and intracortical FLAIR intensity in 22 patients with hippocampal sclerosis (HS) and 30 controls. Surface‐based linear models assessed between‐group differences in morphological and MR signal intensity markers. Structural integrity of the hippocampus was measured by quantifying atrophy and FLAIR patterns. Linear models were used to evaluate the relationships between hippocampal and neocortical MRI markers and clinical factors.ResultsIn the hippocampus, patients demonstrated ipsilateral atrophy and bilateral FLAIR hyperintensity. In the neocortex, patients showed FLAIR signal hyperintensities and gray–white matter boundary blurring in the ipsilesional mesial and lateral temporal neocortex. In contrast, cortical thinning was minimal and restricted to a small area of the ipsilesional temporal pole. Furthermore, patients with a history of febrile convulsions demonstrated more pronounced FLAIR hyperintensity in the ipsilesional temporal neocortex.InterpretationPediatric HS patients do not yet demonstrate the widespread cortical thinning present in adult cohorts, which may reflect consequences of a protracted disease process. However, pronounced temporal neocortical FLAIR hyperintensity and blurring of the gray–white matter boundary are already detectable, suggesting that alterations in MR signal intensities may reflect a different underlying pathophysiology that is detectable earlier in the disease and more pervasive in patients with a history of febrile convulsions.

Multimodal imaging in acute retinal ischemia: spectral domain OCT, OCT-angiography and fundus autofluorescence.

To describe retinal findings of various imaging modalities in acute retinal ischemia. Fluorescein angiography (FA), spectral domain optical coherence tomography (SD-OCT), OCT-angiography (OCT-A) and fundus autofluorescence (FAF) images of 13 patients (mean age 64y, range 28-86y) with acute retinal ischemia were evaluated. Six suffered from branch arterial occlusion, 2 had a central retinal artery occlusion, 2 had a combined arteriovenous occlusions, 1 patient had a retrobulbar arterial compression by an orbital haemangioma and 2 patients showed an ocular ischemic syndrome. All patients showed increased reflectivity and thickening of the ischemic retinal tissue. In 10 out of 13 patients SD-OCT revealed an additional highly reflective band located within or above the outer plexiform layer. Morphological characteristics were a decreasing intensity with distance from the fovea, partially segmental occurrence and manifestation limited in time. OCT-A showed a loss of flow signal in the superficial and deep capillary plexus at the affected areas. Reduced flow signal was detected underneath the regions with retinal edema. FAF showed areas of altered signal intensity at the posterior pole. The regions of decreased FAF signal corresponded to peri-venous regions. Multimodal imaging modalities in retinal ischemia yield characteristic findings and valuable diagnostic information. Conventional OCT identifies hyperreflectivity and thickening and a mid-retinal hyperreflective band is frequently observed. OCT-A examination reveals demarcation of the ischemic retinal area on the vascular level. FAF shows decreased fluorescence signal in areas of retinal edema often corresponding to peri-venous regions.

Global and Widespread Local White Matter Abnormalities in Juvenile Neuronal Ceroid Lipofuscinosis

Juvenile neuronal ceroid lipofuscinosis is a progressive neurodegenerative lysosomal storage disease of childhood. It manifests with loss of vision, seizures, and loss of cognitive and motor functions leading to premature death. Previous MR imaging studies have reported cerebral and cerebellar atrophy, progressive hippocampal atrophy, thalamic signal intensity alterations, and decreased white matter volume in the corona radiata. However, conventional MR imaging findings are usually normal at younger than 10 years of age. The purpose of our study was to investigate whether diffusion MR imaging could reveal changes in white matter microstructure already present at a younger age. We investigated global and local white matter abnormalities in 14 children with juvenile neuronal ceroid lipofuscinosis (mean age, 9.6 ± 3.4 years; 10 boys) and 14 control subjects (mean age, 11.2 ± 2.3 years; 7 boys). Twelve patients underwent follow-up MR imaging after 2 years (mean age, 11.4 ± 3.2 years; 8 boys). We performed a global analysis using 2 approaches: white matter tract skeleton and constrained spherical deconvolution-based whole-brain tractography. Then, we investigated local microstructural abnormalities using Tract-Based Spatial Statistics. We found globally decreased anisotropy (P = .000001) and increased diffusivity (P = .001) in patients with juvenile neuronal ceroid lipofuscinosis. In addition, we found widespread increased diffusivity and decreased anisotropy in, for example, the corona radiata (P < .001) and posterior thalamic radiation (P < .001). However, we found no differences between the first and second acquisitions. The patients with juvenile neuronal ceroid lipofuscinosis exhibited global and local abnormalities in white matter microstructure. Future studies could apply more specific microstructural models and study whether these abnormalities are already present at a younger age.

Signal intensity alteration within infrapatellar fat pad predicts knee replacement within 5 years: data from the Osteoarthritis Initiative

To investigate whether infrapatellar fat pad (IPFP) signal intensity (SI) alteration predicts the occurrence of knee replacement (KR) in knee osteoarthritis (OA) patients over 5years. The subjects were selected from Osteoarthritis Initiative (OAI) study. Case knees (n=127) were defined as those who received KR during 5years follow-up visit. They were matched by gender, age and radiographic status with control knees (n=127). We used T2-weighted MR images to measure IPFP SI alteration using a newly developed algorithm in MATLAB. The measurements were assessed at baseline (BL), T0 (the visit just before KR) and 1year before T0 (T-1). Conditional logistic regression was used to analyse the associations between IPFP SI alterations and the risk of KR. Participants were mostly female (57%), with an average age of 63.7 years old and a mean body mass index (BMI) of 29.5kg/m2. In multivariable analysis, the standard deviation (SD) of IPFP SI [sDev (IPFP)] and the ratio of high SI region volume to whole IPFP volume [Percentage (H)] measured at BL were significantly associated with increased risks of KR after adjustment for covariates. IPFP SI alterations measured at T-1 including sDev (IPFP), Percentage (H) and clustering effect of high SI [Clustering factor (H)] were significantly associated with higher risks of KR. All measurements were significantly associated with higher risks of KR at T0. IPFP SI is associated with the occurrence of KR suggesting it may play a role in end-stage knee OA.

Associations between knee structural measures, circulating inflammatory factors and MMP13 in patients with knee osteoarthritis

To investigate cross-sectional associations between serum level of Matrix metalloproteinase (MMP)13 and knee structural measures and circulating inflammatory factors in patients with symptomatic knee osteoarthritis (OA). A total of 149 subjects with symptomatic knee OA were included. Magnetic resonance imaging was used to measure infrapatellar fat pad (IPFP) volume, IPFP signal intensity alternation, cartilage volume and cartilage defects. Knee radiography was used to assess radiographic OA using the Kellgren-Lawrence (K-L) grading system. Enzyme-linked immunosorbent assay was used to measure the serum levels of inflammatory factors and MMP13. In multivariable analyses, serum MMP13 was negatively associated with cartilage volume at patellar site (β:-32.94mm3 per 10ng/ml, P<0.05), and positively associated with cartilage defect at medial femoral site (OR: 1.13 per 10ng/ml, P<0.05). Also, MMP13 was positively associated with K-L grading and IPFP signal intensity alteration (OR: 1.14 and 1.15 per 10ng/ml, respectively, both P<0.05), and negatively associated with IPFP volume (β:-0.34cm3 per 10ng/ml, P<0.05). Furthermore, serum level of adiponectin was negatively associated serum MMP13 quartiles (OR: 0.66 per 10μg/ml, P<0.05), and serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-8 and IL-18 were positively associated with serum MMP13 quartiles (ORs: 1.01-1.18 per 10pg/ml, all P<0.05). Serum level of MMP13 was associated with knee structural abnormalities as well as serum inflammatory factors. These suggest that systemic MMP13 may play a role in knee OA, and could be regulated by inflammatory factors.

Use of black-bone MRI in the diagnosis of the patients with posterior plagiocephaly.

Ionising radiation exposure is especially harmful to brain development. The purpose of this study was to evaluate whether black-bone (BB) magnetic resonance imaging (MRI), a non-ionising imaging method, offers an alternative to ionising imaging methods such as computed tomography (CT) in the examination of cranial deformities. From 2012 to 2014, a total of 408 children were referred to the Craniofacial Centre at the Helsinki University Hospital for further examination due to flatness of the posterior skull. Fifteen of these patients required further diagnostic imaging. To avoid ionising radiation, we used an MRI protocol that included sequences for evaluation of both brain anatomy and skull bone and sutures by BB-MRI. A semi-automatic skull segmentation algorithm was developed to facilitate the visualisation. Two patients with scaphocephaly were included in the study to confirm the ability to differentiate synostosis with BB-MRI. We obtained informative 3D images using BB-MRI. Seven patients (7/15, 46.7%) had plagiocephaly on the right side and seven on the left side (7/15, 46.7%). One patient (1/15, 6.7%) had symmetric posterior flatness affecting both sides. Neither structural nor signal-intensity alterations of the brain were detected in visual analysis. BB-MRI provides an alternative to CT when imaging craniofacial deformities. BB-MRI provides not only high-quality 3D-reconstructed imaging of the bony structures and sutures but also information on brain structure in one imaging session. With further development, this method could replace ionising radiation-based methods in analysing deformities of the skull.

A novel mutation in SLC39A14 causing hypermanganesemia associated with infantile onset dystonia

Mutations in SLC39A14 cause a recessive disorder of manganese (Mn) metabolism that manifests as childhood onset progressive neurodegeneration characterized by parkinsonism and dystonia. The present study genetically investigated a case of hypermanganesemia. We describe a family where an affected child with a history of progressive neurodegeneration showed symptoms of dystonia with increased levels of blood Mn and altered signal intensities in globus pallidus and dentate nucleus. Whole exome sequencing was conducted to genetically investigate the pathology in the child, which allowed us to identify a novel homozygous causal mutation in SLC39A14. Insilico modeling of the novel homozygous causal mutation in SLC39A14 predicted that it was deleterious, affecting Mn binding and transportation of metal by transmembrane instability of the protein structure. The clinical features of other reported mutations in SLC39A14 were also reviewed and the clinical spectrum in our case conforms to the described neurological abnormalities. We conclude that the mutation identified in SLC39A14 in our case is a novel variation linked to recessive disorders of hypermaganesemia and dystonia.

MR Imaging of Atraumatic Muscle Disorders.

Atraumatic disorders of skeletal muscles include congenital variants; inherited myopathies; acquired inflammatory, infectious, or ischemic disorders; neoplastic diseases; and conditions leading to muscle atrophy. These have overlapping appearances at magnetic resonance (MR) imaging and are challenging for the radiologist to differentiate. The authors organize muscle disorders into four MR imaging patterns: (a) abnormal anatomy with normal signal intensity, (b) edema/inflammation, (c) mass, and (d) atrophy, highlighting each of their key clinical and imaging findings. Anatomic muscle variants, while common, do not produce signal intensity alterations and therefore are easily overlooked. Muscle edema is the most common pattern but is nonspecific, with a broad differential diagnosis. Autoimmune, paraneoplastic, and drug-induced myositis tend to be symmetric, whereas infection, radiation-induced injury, and myonecrosis are focal asymmetric processes. Architectural distortion in the setting of muscle edema suggests one of these latter processes. Intramuscular masses include primary neoplasms, metastases, and several benign masslike lesions that simulate malignancy. Some lesions, such as lipomas, low-flow vascular malformations, fibromatoses, and subacute hematomas, are distinctive, but many intramuscular masses ultimately require a biopsy for definitive diagnosis. Atrophy is the irreversible end result of any muscle disease of sufficient severity and is the dominant finding in disorders such as the muscular dystrophies, denervation myopathy, and sarcopenia. This imaging-based classification, in correlation with clinical and laboratory data, will aid the radiologist in interpreting MR imaging findings in patients with atraumatic muscle disorders. ©RSNA, 2018.

A patient with features of both Neurofibromatosis I and Neurofibromatosis II on MR imaging

Neurofibromatosis (NF) type II is a neurocutaneous disease with an autosomal dominant pattern of inheritance with its gene locus on chromosome 22q 12 with bilateral acoustic schwannoma being the hallmark of this disease. NF II is considered central neurofibromatosis while NF I is the peripheral neurofibromatosis. This case report presents a case of a 15 year old female who came with complaint of bilateral tinnitus, hearing loss, low grade fever and weakness in bilateral lower limbs , which on imaging work up showed bilateral acoustic schwannoma, meningioma and small cord ependymoma giving the classical features of neurofibromatosis II along with unique features of cafe au lait spots, cutaneous neurofibromas, plexiform neurofibromas, and focus of altered signal intensity in white matter tracts of left frontal lobe which are unique to NF1. To our knowledge no such previous case report with overlapping features of both NF-1 and NF-2 has been described before.

Validity of Radiograph-Based Infrapatellar Fat Pad Opacity Grading for Assessing Knee Synovitis: Correlation With Contrast-Enhanced MRI.

The purpose of this study was to determine the validity of infrapatellar fat pad (IPFP) opacity grading based on lateral knee radiography for assessing knee synovitis using correlation with contrast-enhanced (CE) MRI. Retrospective reviews of radiographs and CE knee MR images from 79 patients were independently performed by two radiologists. They evaluated IPFP opacity alteration (IPFPCR) and joint effusion grades on lateral knee conventional radiographs, IPFP signal intensity alteration (IPFPMR) and joint effusion grades on CE MR images, and synovitis (SYNMR) grade in nine divided regions, three compartments (parapatellar, periligamentous, perimeniscal), and the whole knee on CE MR images. Correlations between radiographic grades and MRI assessments were evaluated using Spearman correlation tests, and the correlation coefficients (ρ) were compared. Interobserver agreement was evaluated using weighted kappa values. The IPFPCR grade was very highly correlated with the IPFPMR grade (ρ = 0.906, p < 0.001) and highly correlated with SYNMR grades from four regions (suprapatellar, infrapatellar, intercondylar, lateral parapatellar recess), the parapatellar compartment, and the whole knee (ρ = 0.614-0.740, all p < 0.001). The IPFPCR grade was moderately correlated with the SYNMR grades of the remaining five regions and two compartments (ρ = 0.457-0.547, all p < 0.001). The differences between correlation coefficients for SYNMR grades and the IPFPCR and IPFPMR grades were not statistically significant (p = 0.290-1.0). Interobserver reliabilities were excellent or good for IPFPCR, IPFPMR, and SYNMR grades (κ = 0.661-1.000). IPFPCR grade assessment enables valid evaluation and reporting of knee synovitis, especially in the parapatellar compartment and the whole knee.

Does Diagnostic Analgesia in the Distal Aspect of the Limb of Horses Performed in a Clinical Situation Less Than 12 or 36 Hours Before Magnetic Resonance Imaging Result in Artifacts?

The potential effect of diagnostic analgesia performed <24 hours before magnetic resonance imaging (MRI) has not been assessed. It is not known whether perineural or intrasynovial analgesia performed in a clinical setting in unsedated horses might result in more tissue trauma and consequently artifacts than in sedated horses in an experimental setting. The aims of this study were to assess whether diagnostic analgesia (using mepivacaine) in the distal aspect of the limb in a clinical setting in unsedated horses, performed on the day of (<12 hours) or the day before (<36 hours) high-field and low-field MRI, results in artifacts that could confound image interpretation. Cases were limbs which had undergone diagnostic analgesia in the distal aspect of the limb <36 hours before high-field (n = 17) or low-field (n = 55) MRI. Controls had MRI of the same region as cases but had not undergone diagnostic analgesia in the distal aspect of the limb <36 hours before MRI. The regions of possible injection sites were assessed for alteration in signal intensity and/or in the contour of the limb, altered tissue architecture, or a needle tract. Distension of the dorsal pouch of the distal interphalangeal joint and of the digital flexor tendon sheath was measured. There were no artifacts resulting from diagnostic analgesia performed within 12 or 36 hours preceding low-field or high-field MRI that could confound image interpretation. Results suggest that it is reasonable and safe (from an imaging point of view) to perform diagnostic analgesia in the distal aspect of the limb shortly before MRI.

Spectrum of findings on magnetic resonance imaging of the brain in patients with neurological manifestations of dengue fever.

ObjectiveTo describe the spectrum of magnetic resonance imaging (MRI) findings in patients with neurological manifestations of dengue.Materials and MethodsWe included nine patients with dengue fever (three females and six males; age range, 9–30 years), all of whom presented with neurological manifestations. The MRI examinations, performed in 1.5 T or 3 T scanners, included T1-weighted, T2-weighted, and fluid-attenuated inversion recovery (FLAIR) sequences. Diffusion-weighted imaging with apparent diffusion coefficient mapping was also employed. Fast low-angle shot and susceptibility-weighted gradient-recalled echo sequences, as well as contrast-enhanced T1-weighted scans, were also obtained in order to assess parenchymal enhancement. MRI scans were analyzed for lesion distribution and imaging features.ResultsAll patients showed areas of altered signal intensity that appeared as hyperintensity on T2-weighted and FLAIR sequences. The most commonly affected site was the basal ganglia-thalamus complex. Other affected sites were the cerebellum, cerebral cortex, white matter, and brainstem. In all cases, we observed patchy areas of restricted diffusion and focal areas of hemorrhage.ConclusionDengue encephalitis commonly affects the basal ganglia, thalamus, cerebellum, cerebral cortex, and white matter. Therefore, MRI should be an indispensable part of the evaluation of patients with neurological complications of dengue fever.