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Biomedical subjects

K R Maravilla

Publications and source records attributed to K R Maravilla.

At least 19 recordsLinked to original sources
PubMed2002

Brain structural abnormalities in young children with autism spectrum disorder.

OBJECTIVE: To explore the specific gross neuroanatomic substrates of this brain developmental disorder, the authors examine brain morphometric features in a large sample of carefully diagnosed 3- to 4-year-old children with autism spectrum disorder (ASD) compared with age-matched control groups of typically developing (TD) children and developmentally delayed (DD) children. METHODS: Volumes of the cerebrum, cerebellum, amygdala, and hippocampus were measured from three-dimensional coronal MR images acquired from 45 children with ASD, 26 TD children, and 14 DD children. The volumes were analyzed with respect to age, sex, volume of the cerebrum, and clinical status. RESULTS: Children with ASD were found to have significantly increased cerebral volumes compared with TD and DD children. Cerebellar volume for the ASD group was increased in comparison with the TD group, but this increase was proportional to overall increases in cerebral volume. The DD group had smaller cerebellar volumes compared with both of the other groups. Measurements of amygdalae and hippocampi in this group of young children with ASD revealed enlargement bilaterally that was proportional to overall increases in total cerebral volume. There were similar findings of cerebral enlargement for both girls and boys with ASD. For subregion analyses, structural abnormalities were observed primarily in boys, although this may reflect low statistical power issues because of the small sample (seven girls with ASD) studied. Among the ASD group, structural findings were independent of nonverbal IQ. In a subgroup of children with ASD with strictly defined autism, amygdalar enlargement was in excess of increased cerebral volume. CONCLUSIONS: These structural findings suggest abnormal brain developmental processes early in the clinical course of autism. Research currently is underway to better elucidate mechanisms underlying these structural abnormalities and their longitudinal progression.

Amygdala↗
PubMed2001

fMRI auditory language differences between dyslexic and able reading children.

During fMRI, dyslexic and control boys completed auditory language tasks (judging whether pairs of real and/or pseudo words rhymed or were real words) in 30 s 'on' conditions alternating with a 30 s 'off' condition (judging whether tone pairs were same). During phonological judgment, dyslexics had more activity than controls in right than left inferior temporal gyrus and in left precentral gyrus. During lexical judgment, dyslexics were less active than controls in bilateral middle frontal gyrus and more active than controls in left orbital frontal cortex. Individual dyslexics were reliably less active than controls in left insula and left inferior temporal gyrus. Dyslexic and control children differ in brain activation during auditory language processing skills that do not require reading.

Acoustic Stimulation↗
PubMed2001

Carotid atherosclerotic plaque: noninvasive MR characterization and identification of vulnerable lesions.

Measurement of vessel stenosis by using ultrasonography or angiography remains the principal method for determining the severity of carotid atherosclerosis and the need for endarterectomy. The ipsilateral stroke rate, however--even in patients with severely stenotic vessels--is relatively low, which suggests that the amount of luminal narrowing may not represent the optimal means of assessing clinical risk. As a result, some patients may undergo unnecessary surgery. Improved imaging techniques are, therefore, needed to enable reliable identification of high-risk plaques that lead to cerebrovascular events. High-spatial-resolution magnetic resonance (MR) imaging has been described as one promising modality for this purpose, because the technique allows direct visualization of diseased vessel wall and can be used to characterize the morphology of individual atherosclerotic carotid plaques. The purpose of this report is to review the current state of carotid plaque MR imaging and the use of carotid MR to evaluate plaque morphology and composition.

Carotid Artery Diseases↗
PubMed2001

Cerebrospinal fluid signal intensity increase on FLAIR MR images in patients under general anesthesia: the role of supplemental O2.

PURPOSE: To determine whether increased cerebrospinal fluid (CSF) signal intensity is seen on fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images in patients under general anesthesia and to investigate the cause of these changes. MATERIALS AND METHODS: MR images from nine examinations performed in eight patients under general anesthesia were reviewed retrospectively. In phantom experiments, T1 measurements obtained with several inhaled anesthetic agents and propofol dissolved in saline were compared with those obtained with either 100% O2 or room air. To confirm phantom experiment results, a healthy volunteer underwent sequential FLAIR imaging while breathing high-flow 100% O2. RESULTS: Of the nine examinations performed with patients under general anesthesia, eight had resultant images that showed increased CSF signal intensity within the basal cisterns and sulci over the cerebral convexities. Anesthetic phantom measurements showed T1 shortening only when the agent was administered with high concentrations of oxygen. In the healthy volunteer, images obtained before and during administration of 100% O2 demonstrated increased CSF signal intensity after O2 administration; this was identical to the changes observed in patients under anesthesia. CONCLUSION: The paramagnetic effects of supplemental O2 administration result in shortened CSF T1. Radiologists should be aware of this phenomenon to avoid attributing increased CSF signal intensity on FLAIR images to abnormal CSF properties such as hemorrhage or elevated protein content.

Adolescent↗
PubMed2001

Clinically relevant rat model for testing BOLD functional MR imaging techniques by using single-shot echo-planar imaging at 1.5 T.

By using a 1.5-T whole-body magnetic resonance (MR) imager, a high-spatial-resolution single-shot echo-planar technique was developed to perform blood oxygen level dependent functional MR imaging of rat sensory cortex during forepaw stimulation. This technique produced cubic 1-mm(3) voxels. Signal-to-noise ratio was 140-160 (43-44 dB). Optimal effective echo time was 50 msec. This system should prove useful for developing new functional MR imaging techniques with rapid adaptation to human use.

Animals↗
PubMed2001

Effects of prolonged intensive lipid-lowering therapy on the characteristics of carotid atherosclerotic plaques in vivo by MRI: a case-control study.

High-resolution magnetic resonance imaging (MRI) with flow suppression not only provides useful information on luminal and wall areas of the carotid artery but also can identify the principal tissue components of the carotid atherosclerotic plaque. The effects of intensive lipid-lowering therapy on these MRI tissue characteristics were examined in patients with coronary disease (CAD). Eight CAD patients who have been receiving intensive lipid-lowering treatment (niacin 2.5 g/d, lovastatin 40 mg/d, and colestipol 20 g/d) for 10 years in the Familial Atherosclerosis Treatment Study (FATS) follow-up were randomly selected from among 60 such treated patients. Eight CAD patients who were matched to the treated patients for age (+/-3 years), baseline low density lipoprotein (+/-5 mg/dL), and triglycerides (+/-50 mg/dL) but who had never been treated with lipid-lowering drugs were selected as controls. For each of these 32 carotid arteries, luminal and plaque areas were measured by planimetry, in a blinded protocol, from the magnetic resonance image that showed most plaque. Fibrous tissue, calcium, and lipid deposits were identified on the basis of established criteria. Plaque composition was estimated as a fraction of total planimetered area. Patients treated with 10-year intensive lipid-lowering therapy, compared with control subjects, had significantly lower low density lipoprotein cholesterol levels (84 versus 158 mg/dL, respectively; P<0.001) and higher high density lipoprotein cholesterol levels (51 versus 37 mg/dL, respectively; P<0.001). As a group, treated patients, compared with untreated control subjects, had a smaller core lipid area (0.7 versus 10.2 mm(2), respectively; P=0.01) and lipid composition (1% versus 17%, respectively). Group differences in luminal area (55 [treated] versus 44 [control] mm(2), P=NS) and plaque area (58 [treated] versus 64 [control] mm(2), P=NS) tended to favor treatment. MRI appears useful for estimating carotid plaque size and composition. Hyperlipidemic CAD patients frequently (97%) have at least moderate (>/=40% area stenosis) carotid plaque. In this case-control study, prolonged intensive lipid-lowering therapy is associated with a markedly decreased lipid content, a characteristic of clinically stable plaques.

Calcinosis↗
PubMed2001

Magnetic resonance neurography: magnetic resonance imaging of peripheral nerves.

With advances in modern MR imaging, direct MR visualization of many peripheral nerves is now possible. MR nerve imaging can detect and delineate the extent of neural tumors, demonstrate nerve continuity in cases of traumatic injury, and demonstrate abnormal enlargement and abnormal signal in diseased peripheral nerves. This ability to image peripheral nerves has the potential to dramatically change the diagnosis and treatment of peripheral nerve disease. This article describes the techniques for peripheral nerve imaging and provides a brief overview of a broad spectrum of peripheral nerve abnormalities.

Humans↗
PubMed2001

Decreased diffusion in central pontine myelinolysis.

Two patients with central pontine myelinolysis (CPM) were studied with diffusion-weighted MR imaging 1 week after onset of tetraplegia. In both patients, affected white matter showed hyperintensity on diffusion-weighted images associated with a decrease in apparent diffusion coefficient (ADC) values. In one patient studied serially, ADC values normalized by 3 weeks after tetraplegia. Early in the clinical course, diagnosis of CPM can sometimes be difficult. Hyperintensity on diffusion-weighted images may therefore have diagnostic utility. Decreased lesional ADC values support the notion that CPM is a consequence of relative intracellular hypotonicity.

Adult↗
PubMed2000

Morphological plasticity in an infant monkey model of temporal lobe epilepsy.

PURPOSE/METHODS: Seizures in early life are thought to contribute to the development of human temporal lobe epilepsy. To examine the consequences of early seizures, we elicited status epilepticus in immature, 5.5- to 7.0-month-old pigtailed macaques by unilateral microinfusion of bicuculline methiodide into the entorhinal cortex. RESULTS: This report focuses on neuropathological changes in the hippocampus. Bicuculline infusion consistently elicited limbic-like seizures with prolonged, relatively localized electrographic activity. Magnetic resonance imaging revealed enhanced signal intensity in the ipsilateral hippocampus after seizures; in some cases, there was also progressive hippocampal atrophy. Histological changes were variable; in two of five monkeys, there was significant hippocampal neuron loss, gliosis, granule cell dispersion, and mossy fiber reorganization. CONCLUSIONS: The histopathological findings and associated magnetic resonance imaging abnormalities after bicuculline-induced status epilepticus in infant monkeys mimic common aspects of human temporal lobe epilepsy.

Animals↗
PubMed2000

Preoperative embolization of cerebral arteriovenous malformations with silk sutures: analysis and clinical correlation of complications revealed on computerized tomography scanning.

OBJECT: The aim of this study was to determine the incidence and clinical significance of complications related to preoperative embolization of cerebral arteriovenous malformations (AVMs) with silk sutures as documented on postprocedure computerized tomography (CT) scans. METHODS: The CT scans were obtained within 12 to 24 hours after 221 (96%) of 230 consecutive embolizations in 70 patients. These CT scans were evaluated for the presence of ischemia, infarction, hemorrhage, or contrast agent extravasation. Adverse patient outcomes were determined after each embolization and were correlated with CT findings. New abnormalities demonstrated on CT scans were also correlated with the Spetzler-Martin AVM grade, degree of arteriovenous shunting, and location. New abnormalities, the majority of them infarcts, resulted from 29 (13%) of 221 embolization procedures. In 11 (38%) of 29 cases of new CT findings, patients were asymptomatic, including 10 with new infarcts on CT scans. New neurological deficits occurred in 20 (8.7%) of 230 total embolization procedures in 19 patients, including one death. Permanent deficits occurred in nine patients (3.9% per embolization procedure, 12.8% per patient). Of the patients with new neurological deficits, 18 (90%) of 20 embolization procedures resulted in new abnormalities on CT scans. Two patients with new transient neurological deficits had no new findings on CT scans. Spetzler-Martin grade, AVM location, degree of arteriovenous shunting, and higher numbers of procedures were not statistically associated with a higher incidence of abnormalities on CT scans or new permanent neurological deficits. CONCLUSIONS: Silk sutures are an effective and relatively safe embolic agent. After brain AVM embolization with silk sutures, new abnormalities were found on CT scans obtained in one of eight procedures. When a new CT finding occurred, the patient had roughly equal chances of having no new symptoms, having new transient neurological deficits, or having new permanent neurological deficits.

Adult↗
PubMed2000

MR nerve imaging of the wrist and hand.

Peripheral nerve imaging is still in a relatively early phase of development. This article explains a few of the important technical aspects of peripheral nerve imaging and reviews the results of animal experiments that form the foundation for interpreting image results. The clinical discussion focuses on the use of MR imaging for patients with carpal tunnel syndrome, keeping in mind that many aspects of the imaging technique may be applied to other areas. The reliability, diagnostic accuracy, and potential indications for peripheral nerve imaging are discussed.

Animals↗
PubMed2000

Effects of a phonologically driven treatment for dyslexia on lactate levels measured by proton MR spectroscopic imaging.

BACKGROUND AND PURPOSE: Dyslexia is a language disorder in which reading ability is compromised because of poor phonologic skills. The purpose of this study was to measure the effect of a phonologically driven treatment for dyslexia on brain lactate response to language stimulation as measured by proton MR spectroscopic imaging. METHODS: Brain lactate metabolism was measured at two different time points (1 year apart) during four different cognitive tasks (three language tasks and one nonlanguage task) in dyslexic participants (n = 8) and in control participants (n = 7) by using a fast MR spectroscopic imaging technique called proton echo-planar spectroscopic imaging (1 cm3 voxel resolution). The age range for both dyslexic and control participants was 10 to 13 years. Between the first and second imaging sessions, the dyslexic boys participated in an instructional intervention, which was a reading/science workshop. RESULTS: Before treatment, the dyslexic boys showed significantly greater lactate elevation compared with a control group in the left anterior quadrant (analysis of variance, P = .05) of the brain during a phonologic task. After treatment, however, brain lactate elevation was not significantly different from that of the control group in the left anterior quadrant during the same phonologic task. Behaviorally, the dyslexic participants improved in the phonologic aspects of reading. CONCLUSION: Instructional intervention that improved phonologic performance in dyslexic boys was associated with changes in brain lactate levels as measured by proton echo-planar spectroscopic imaging.

Brain↗
PubMed1999

Pharmacokinetics, safety, and tolerability of gadoversetamide injection (OptiMARK) in subjects with central nervous system or liver pathology and varying degrees of renal function.

The pharmacokinetic parameters, safety, and tolerability of OptiMARK (gadoversetamide injection), a gadolinium-based magnetic resonance imaging (MRI) contrast agent, were evaluated in 163 subjects with either central nervous system (CNS) or liver pathology with and without renal insufficiency, for which a contrast-enhanced MRI was indicated. A multicenter, double-blind, randomized, placebo-controlled, parallel-group design was used in which subjects received 0.1, 0.3, or 0.5 mmol/kg of OptiMARK or placebo intravenously. Samples were analyzed for total gadolinium by inductively coupled plasma/mass spectrometry. Gadolinium pharmacokinetics were affected by renal impairment: area under the curve, half-life, and steady-state distribution volume significantly increased with declining renal function, while total body clearance decreased. In subjects with normal renal function, neither age, gender, nor liver versus CNS pathology altered gadolinium pharmacokinetics. No clinically significant changes from baseline were noted in vital signs, laboratory measures, electrocardiograms, or physical examinations. OptiMARK is safe and well-tolerated following a single intravenous injection in subjects with either liver or CNS pathology despite a prolonged elimination half-life in subjects with renal impairment.

Adult↗
PubMed1999

Comparison of clinical and magnetic resonance imaging diagnosis in patients with disk displacement in the temporomandibular joint.

OBJECTIVE: The purpose of this study was to validate the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) for the diagnostic subgroup of disk displacement with reduction, with magnetic resonance imaging used as a gold standard. STUDY DESIGN: The diagnoses from the clinical examination of 78 joints in 39 patients, each with disk displacement with reduction in at least one TMJ, were compared with magnetic resonance imaging diagnoses. The readers of the magnetic resonance images were blinded to the clinical diagnoses. The data analysis included kappa statistics and calculation of predictive values. RESULTS: The predictive value of the RDC/TMD for disk displacement with reduction was 0.65. For disk displacement alone-the movement of the disk on opening not being considered-the predictive value was 0.92. The diagnostic agreement between RDC/TMD and magnetic resonance imaging diagnoses for all joints examined was 53.8%. Most of the disagreement was due to false negative clinical diagnoses for asymptomatic joints. CONCLUSIONS: A positive RDC/TMD examination is predictive for internal derangement but not reliable with regard to the type of disk displacement; such examination is therefore of limited value in determining the true disk position and its functional movements.

Adult↗
PubMed1999

Value of combined FDG PET and MR imaging in the evaluation of suspected recurrent local-regional breast cancer: preliminary experience.

PURPOSE: To assess the performance and potential clinical effects of combined 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) and magnetic resonance (MR) imaging of the axilla and brachial plexus in patients suspected of having local-regional breast cancer metastases. MATERIALS AND METHODS: Upper-body FDG PET and axillary and supraclavicular MR imaging were performed in 10 patients (age range, 45-71 years) with clinical findings suggestive of breast cancer metastases. Medical records were reviewed retrospectively. Imaging findings were correlated with clinical data and follow-up findings in all patients. Surgical findings were available in four patients. RESULTS: Nine patients had local-regional breast cancer metastases. MR imaging was diagnostic for tumor in five patients and was indeterminate in four patients with axillary or chest wall metastases. With FDG PET, metastatic tumor was positively identified in all nine patients. MR imaging was useful for determining the relationship of metastatic tumor to axillary and supraclavicular neurovascular structures. FDG PET helped confirm metastases in patients with indeterminate MR imaging findings and depicted unsuspected metastases outside the axilla. CONCLUSION: MR imaging and FDG PET are complementary in detecting and characterizing local-regional breast cancer metastases. Combined FDG PET and MR imaging provide useful treatment-planning data for patients clinically suspected of having recurrent axillary or supraclavicular breast cancer.

Aged↗
PubMed1999

Development of a model of status epilepticus in pigtailed macaque infant monkeys.

Seizures, particularly multiple episodes and/or status epilepticus (SE) are prevalent in pediatric patients. Pediatric SE is associated with brain changes that have been hypothesized to contribute to the onset of temporal lobe epilepsy (TLE). In order to gain insight into the effects of seizures on the immature brain and the risk for later TLE, we have developed a model of limbic SE in the pigtailed macaque monkey. In separate studies, bicuculline methiodide or a bicuculline 'cocktail' was infused into three regions of the brain (area tempestas, hippocampus, entorhinal cortex) to induce seizures. Measures included MRI, electrophysiology, behavior and morphology. Our results suggest that monkey models of SE may provide useful tools for understanding the effects of prolonged seizures during infancy and the origins of TLE in humans.

Animals↗