Biomedical subjects

Claudia C Leite

Publications and source records attributed to Claudia C Leite.

10 recordsLinked to original sources

PubMed2006

Performing functional magnetic resonance imaging in patients with Parkinson's disease treated with deep brain stimulation.

Deep brain stimulation (DBS) is a relatively novel treatment in advanced Parkinson's disease (PD). Functional magnetic resonance imaging (fMRI) is a useful technique for examining the effects of DBS both within the basal ganglia and its cortical connectivity. There are technical difficulties in imaging patients with PD, and the DBS itself can generate image artifacts. We describe aspects related to optimizing the fMRI acquisition parameters in patients with DBS and the results of sensorimotor activation tasks performed by four PD patients during hand, foot, and tongue movements, both before and after DBS implant. Provided that all safety conditions are followed, it is possible to perform fMRI in patients with PD and DBS. The standard DBS surgical procedure has to be slightly modified in order to reduce image artifacts. The event-related design provided increased power to detect sensorimotor cortex and basal ganglia activation.

Artifacts↗

PubMed2006

Pitfalls in the diagnosis of brain tumours.

Establishing the diagnosis of a brain tumour is not always a straightforward process. Many non-neoplastic neurological diseases can mimic brain neoplasms on neuroimaging or on histological examination, including multiple sclerosis, stroke, pyogenic abscess, toxoplasmosis, tuberculosis, cysticercosis, fungal infections, syphilis, sarcoidosis, Behçet disease, radiation necrosis, venous thrombosis, and others. Conversely, several types of brain neoplasms, such as glioblastomas, low-grade gliomas, CNS lymphomas, and brain metastases, can present in the absence of typical tumefactive lesions, posing significant diagnostic challenges. In this Review, we discuss the process of accurately establishing the diagnosis of brain tumours, focusing on pitfalls commonly encountered in clinical practice. We also discuss the rational use and limitations of new diagnostic techniques, such as diffusion-weighted MRI, perfusion-weighted MRI, magnetic resonance spectroscopy, single-photon emission tomography, and positron emission tomography, as well as new tools for histological examination, such as immunohistochemistry and molecular genetics analysis.

Brain Diseases↗

PubMed2005

Merosin-deficient congenital muscular dystrophy (CMD): a study of 25 Brazilian patients using MRI.

BACKGROUND: Merosin-deficient congenital muscular dystrophy (CMD) is characterized clinically by hypotonia and muscular weakness and, on imaging studies, by white matter (WM) abnormality. OBJECTIVE: To evaluate MRI findings in Brazilian patients with merosin-deficient CMD. MATERIALS AND METHODS: Twenty-five patients were evaluated using MRI. Three patients presented with partial merosin deficiency and 22 with total merosin deficiency. Follow-up examinations were done in 7 cases. T1- and T2-weighted images were performed in all examinations, and fluid-attenuated inversion recovery (FLAIR) was performed in 15. Enhanced images were done in 11 cases. The WM involvement was classified according to location and severity. RESULTS: From 1991 to 2004, 32 MRI examinations were performed. Severe involvement was found in 23 patients in the frontal and temporal lobes, in 18 patients in the parietal lobes, and in 7 patients in the occipital lobes. The brain stem (n=5), cerebellum (n=6), internal capsules (n=1), and external capsules (n=5) were also affected. One patient had occipital pachygyria, and one had cerebellar vermian hypoplasia. No gadolinium enhancement was noted. Follow-up MRI showed no interval change (n=4), progression (n=1), or improvement of the findings (n=2). CONCLUSION: This series of patients demonstrated that there was no correlation between the extent of WM abnormality on MRI and the clinical status and degree of merosin deficiency (partial or total). Bilateral WM involvement was seen to be more prominent in the parietal, frontal, and temporal regions of the brain. The brain stem and internal and external capsules were less affected. Cerebellar WM involvement is rare. Changes on follow-up imaging studies did not correlate with the clinical status of the patient.

Brain↗

PubMed2005

Congenital muscular dystrophy with merosin deficiency: 1H MR spectroscopy and diffusion-weighted MR imaging.

PURPOSE: To prospectively use hydrogen 1 ((1)H) magnetic resonance (MR) spectroscopy and apparent diffusion coefficient (ADC) maps to try to explain the discrepancy between the extensive white matter (WM) abnormalities observed at MR imaging and the relatively mild neurocognitive decline in patients with merosin-deficient congenital muscular dystrophy (CMD). MATERIALS AND METHODS: The hospital ethics committee approved this study, and informed consent was obtained. Nine patients (five boys, four girls; age range, 3-9 years; mean, 6 years +/- 2 [standard deviation]) with merosin-deficient CMD underwent T1-weighted, T2-weighted, fluid-attenuated inversion recovery, and diffusion-weighted MR imaging and (1)H MR spectroscopy, which was performed in the parieto-occipital WM (POWM) and frontal WM (FWM) by using stimulated-echo acquisition mode. Metabolite (N-acetylaspartate [NAA], choline-containing compounds [Cho], and myo-inositol [mI]) ratios were calculated in relation to creatine/phosphocreatine (Cr) and water (H(2)O). NAA/Cho was also calculated. ADCs were calculated in approximately the same locations that were studied with spectroscopy. For comparison, (1)H MR spectroscopy (n = 10) and ADC mapping (n = 7) were also performed in 10 healthy age- and sex-matched control subjects (three boys, seven girls; age range, 4-9 years; mean, 6 years +/- 1). Statistical analysis involved the t test for comparison between different groups; correlation between ADC and spectroscopy results was studied with the Pearson test. RESULTS: MR imaging revealed evidence of bilateral WM involvement in all patients. Whereas their NAA/Cr and Cho/Cr were normal, their mI/Cr was slightly increased compared with that in control subjects (P = .03 in FWM and P = .07 in POWM), and their NAA/Cho was decreased in POWM (P = .03). NAA/H(2)O, Cr/H(2)O, Cho/H(2)O, and mI/H(2)O were considerably decreased (P < .05 for all) and ADC values were increased (P < .001) in WM in all patients versus these values in WM in control subjects. There was significant correlation between ADC values and metabolite/water ratios (r = -0.777 to -0.967, P < .05). CONCLUSION: ADC mapping and (1)H MR spectroscopy reveal abnormally high free-water concentrations in the WM of patients with merosin-deficient CMD.

Child↗

PubMed2005

Proton MR spectroscopy in Wilson disease: analysis of 36 cases.

BACKGROUND AND PURPOSE: Wilson disease (WD) is rare but one of the few metabolic disorders that can possibly benefit from effective available treatments. The literature regarding proton MR spectroscopy (MRS) in WD is scarce and controversial. The purpose of this study was to determine the brain metabolic changes due to WD by using MRS. To our knowledge, this is the first time that MRS was performed in such a large sample of patients with WD. METHODS: Thirty-six patients with WD and 37 healthy volunteers were examined with MRS in the parieto-occipital cortex, frontal white matter, and basal ganglia (BG). Ratios of the following metabolites were calculated in relation to creatine (Cr): N-acetylaspartate (NAA), choline (Cho), myo-inositol (mI), and glutamine/glutamate (Glx). The mean peak line width was measured on each spectrum. RESULTS: Compared with control subjects, patients with WD had significantly decreased NAA/Cr ratios in the three studied areas (P < .005) and an increased mI/Cr ratio in the BG (P < .001). Cho/Cr and Glx/Cr did not differ between the groups. The mean peak line in the BG was wider in patients than in control subjects. CONCLUSION: WD is unequivocally associated with MRS changes that could possibly be assigned to neuronal loss (in the three studied areas), to gliosis, and to iron and/or copper deposition in the BG.

Adolescent↗

PubMed2004

Detection of somatic TP53 splice site mutations in diffuse astrocytomas.

Alteration in TP53 is the most common genetic event reported for many tumors, including astrocytomas. The majority of studies, on analyzing TP53 mutations, have not included all splice junctions. Consequently, splice site mutations are thought to be relatively infrequent. TP53 were examined for mutations by polymerase chain reaction, single strand conformation polymorphism and direct sequencing in cases of diffuse astrocytomas. We found TP53 mutations in 17.8% (8 out of 45) of the tumors tested: 3 splicing, 3 missense and 2 silent mutations. We have shown that splice site mutations of TP53 are more frequent than previously reported. These findings emphasize the importance of thorough screening of TP53 mutations in gliomas.

Astrocytoma↗

PubMed2003

Diffusion imaging may predict reversible brain lesions in eclampsia and severe preeclampsia: initial experience.

OBJECTIVE: The purpose of this study was to validate diffusion-weighted magnetic resonance imaging in the prediction of the evolutive course of brain edema and to establish its pathophysiologic presence in patients with eclampsia/severe preeclampsia. STUDY DESIGN: Seventeen patients with a clinical diagnosis of severe eclampsia/preeclampsia and T2 hyperintense brain lesions on routine magnetic resonance imaging were evaluated at hospital admission and 8 weeks later. RESULTS: Brain edema was reversible in 13 patients and irreversible in 4 patients, as indicated on follow-up magnetic resonance imaging. Sixteen of 17 patients were differentiated accurately into reversible and irreversible groups on the basis of diffusion imaging on hospital admission. Diffusion-weighted magnetic resonance imaging demonstrated a significant increase in water mobility in abnormal regions compared with normal-appearing brains in patients in the reversible group (1.34+/-0.10 mm(2) vs 0.79+/-0.08 mm(2)/s x 10(-3), P<.001). In the irreversible group, restricted water diffusion was present, which was consistent with cytotoxic edema and early brain infarction in 3 of 4 patients. CONCLUSION: Diffusion-weighted magnetic resonance imaging can predict successfully the evolutive course of brain edema in an acute setting in these patients. Our findings indicate that brain edema is vasogenic, although ischemic/cytotoxic edema was observed less commonly.

Adolescent↗

PubMed2002

Language plasticity revealed by electroencephalogram mapping.

Reasoning is the result of the computations made by intelligent systems, for instance those in the brain. It is not an abstract concept because calculations performed by computations are very concrete transactions among the different central processing unit components. Entropy measurements are proposed here to disclose the plasticity of the cerebral processing associated with language comprehension in video game playing. It is also assumed that entropy may be evaluated from the correlation coefficients obtained for the game event-related activity calculated for the different electroencephalogram derivations in the 10/20 system. The brain mapping derived from these entropy measurements clearly demonstrates the reallocation of speech functions to right brain areas when the classic left language circuits are damaged during prenatal life.

Brain Damage, Chronic↗

PubMed2002

Pituitary magnetic resonance imaging and function in patients with growth hormone deficiency with and without mutations in GHRH-R, GH-1, or PROP-1 genes.

Pituitary stalk interruption and ectopic posterior lobe on magnetic resonance imaging (MRI) are frequently observed in patients with GH deficiency (GHD), but their pathogenesis remains controversial. We performed pituitary stimulation tests, MRI, and studied GH-1, GHRH receptor (GHRH-R), and Prophet of Pit-1 (PROP-1) genes in 76 patients with GHD. Of 33 patients with isolated GHD, 4 had GH-1 deletions and 4 had GHRH-R mutations; of 43 patients with combined pituitary hormone deficiency, 1 had PIT-1 and 5 had PROP-1 mutations. Compared with the 62 patients without mutations, 14 patients with mutations had higher frequency of consanguinity (57 vs. 2%, P < 0.001), familial cases (21 vs. 3%, P < 0.05), and lower frequency of breech delivery or hypoxemia at birth (0 vs. 39%, P < 0.005). On MRI, all patients with mutations had an intact stalk, whereas it was interrupted or thin in 74% without mutations (P < 0.001). The posterior pituitary lobe was in normal position in 92% of patients with mutations against 13% without mutations (P < 0.001). Among patients with combined pituitary hormone deficiency, hormonal deficiencies were of pituitary origin in all with PROP-1 and PIT-1 mutations and suggestive of hypothalamic origin in 81% without mutations. Perinatal insults were associated with thin/interrupted pituitary stalk, ectopic posterior lobe, and hypothalamic origin of hormonal deficiencies. In contrast, GH-1, GHRH-R, and PROP-1 mutations were associated with consanguineous parents, intact pituitary stalk, normal posterior lobe, and pituitary origin of hormonal deficiencies. We conclude that pituitary MRI and hormonal response to stimulation tests are useful in selection of patients and candidate genes to elucidate the etiological diagnosis of GHD.

Adolescent↗

PubMedDate not supplied

Gadolinium-enhanced three-dimensional MR angiography of Takayasu arteritis.

Takayasu arteritis is a form of large vessel vasculitis with a possible autoimmune origin that may cause stenosis of the aorta and its major branches. Six types of Takayasu arteritis are recognized; the type depends on whether the ascending aorta, descending thoracic aorta, abdominal aorta, aortic cervicobrachial branches, or renal arteries are affected. The coronary and pulmonary arteries are also sometimes involved. Clinical features of the disease include diminished or absent pulses, claudication, hypertension, and mesenteric angina. Conventional angiography has been the standard imaging tool for diagnosis and evaluation of Takayasu arteritis, although it demonstrates only the lumen of the vessel. Less invasive cross-sectional methods such as computed tomographic angiography and, more recently, three-dimensional magnetic resonance (MR) angiography can effectively demonstrate thickening of the vessel wall, which may be the earliest manifestation of the disease, occurring before stenosis and dilatation. MR imaging in particular allows better soft-tissue differentiation and can show other signs of inflammation, including mural edema and increased mural vascularity. Other advantages of MR imaging are the lack of iodinated contrast material or ionizing radiation.

Adolescent↗