Biomedical subjects

Leonardo Bonilha

Publications and source records attributed to Leonardo Bonilha.

At least 19 recordsLinked to original sources

PubMed2007

Structural white matter abnormalities in patients with idiopathic dystonia.

We investigated whether structural white matter abnormalities, in the form of disruption of axonal coherence and integrity as measured with diffusion tensor imaging (DTI), constitute an underlying pathological mechanism of idiopathic dystonia (ID), independent of genotype status. We studied seven subjects with ID: all had cervical dystonia as their main symptom (one patient also had spasmodic dysphonia and two patients had concurrent generalized dystonia, both DYT1-negative). We compared DTI MR images of patients with 10 controls, evaluating differences in mean diffusivity (MD) and fractional anisotropy (FA). ID was associated with increased FA values in the thalamus and adjacent white matter, and in the white matter underlying the middle frontal gyrus. ID was also associated with increase in MD in adjacent white matter to the pallidum and putamen bilaterally, left caudate, and in subcortical hemispheric regions, including the postcentral gyrus. Abnormal FA and MD in patients with ID indicate that abnormal axonal coherence and integrity contribute to the pathophysiology of dystonia. These findings suggest that ID is not only a functional disorder, but also associated with structural brain changes. Impaired connectivity and disrupted flow of information may contribute to the impairment of motor planning and regulation in dystonia.

Adult↗

PubMed2006

Longitudinal analysis of gray and white matter loss in patients with systemic lupus erythematosus.

Cerebral atrophy has been described to occur in systemic lupus erythematosus (SLE) with variable frequency. The aim of this study was to determine white and gray matter abnormalities in brain magnetic resonance imaging (MRI) of patients with SLE and to determine if these abnormalities progress over a one-year period. Seventy-five patients with SLE and 44 healthy age and sex-matched controls were enrolled in this study. T1-weighted volumetric images were used for voxel based morphometry (VBM) analyses. SLE patients exhibited a significant reduction in white matter and gray matter volume compared to controls (p=0.001). Follow-up images, after an average interval of 19 months, revealed a progressive white matter and gray matter atrophy (p=0.001). Reduced white and gray matter volume was associated with disease duration and the presence of antiphospholipid antibodies. Patients with severe cognitive impairment had a more pronounced white and gray matter reduction than patients with moderate cognitive impairment. Total corticosteroid dose was associated with gray matter reduction and not with white matter loss in SLE patients. We concluded that brain tissue loss associated with SLE is significant and progresses over a relatively short period of time. Disease duration, the presence of antiphospholipid antibodies and cognitive impairment were associated with white and gray matter loss. Corticosteroid was associated only with gray matter atrophy.

Adolescent↗

PubMed2006

Microstructural white matter abnormalities in nodular heterotopia with overlying polymicrogyria.

Nodular heterotopia (NH) with overlying polymicrogyria can result in medically uncontrolled seizures. Most patients also exhibit deficits of function related to the location of the abnormal cortex. However, functional imaging studies show that the abnormal cortex can retain some function, making surgical planning difficult. It is not known if the connectivity of the abnormal cortex is normal. In this article, we performed an evaluation of molecular diffusion within the white matter in a patient with refractory epilepsy due to NH with overlying polymicrogyria. We observed that the white matter underlying the polymicrogyric area shows signs of microstructural abnormalities. This result suggests that the deficit of function from polymicrogyria result from both the structurally abnormal cortex and from its impaired connectivity.

Adult↗

PubMed2006

Gray matter atrophy associated with duration of temporal lobe epilepsy.

Hippocampal sclerosis is the most common abnormality associated with medial temporal lobe epilepsy (MTLE). Converging evidence supports that hippocampal sclerosis progresses with time. However, it is unclear whether extrahippocampal atrophy in patients with MTLE, similarly to hippocampal sclerosis, is an unremitting progressive process. In this article, we investigate the relationship between duration of epilepsy and gray matter concentration reduction in patients with MTLE within and outside the hippocampus. We employed a voxel-based morphometry study of MRI of the entire brain of 36 patients with drug refractory MTLE and 49 neurologically healthy age-matched controls. We performed a voxel-based parametric and nonparametric investigation of the association between gray matter concentration, age and duration of epilepsy. We complemented the investigation by extracting the gray matter concentration of regions of interest (ROIs) within the limbic system, and we investigated the association between the gray matter concentration on the ROIs and duration of epilepsy. Patients with MTLE exhibited gray matter concentration reduction that is negatively correlated with the duration of epilepsy within the ipsilateral hippocampus, temporal lobes as well as extratemporal limbic structures that are closely connected with the hippocampus. In conclusion, longer duration of refractory epilepsy was associated with a more intense hippocampal and extrahippocampal atrophy in patients with MTLE. The mechanism of progressive neuronal damage in MTLE may be related to active seizure activity within a limbic network, and early seizure control may prevent further brain atrophy in patients with refractory MTLE.

Adolescent↗

PubMed2006

Speech apraxia without oral apraxia: can normal brain function explain the physiopathology?

Apraxia of speech, usually associated with stroke, refers to the inability to perform speech motor movements typically with an intact ability to execute non-speech oral movements. It is uncertain whether apraxia of speech results from damage affecting the insula or the inferior frontal gyrus. The controversy started because of conflicting results from studies investigating patients with disrupted brain structure, when dysfunction of both sites can coexist. We conducted a functional magnetic resonance imaging study of individuals without neurological disorders comparing speech and non-speech movements. Speech movements did not recruit the insula, but activated the left inferior frontal gyrus, suggesting that Broca's area, but not the insula, is critical for speech articulation.

Adolescent↗

PubMed2006

Memory and language impairments and their relationships to hippocampal and perirhinal cortex damage in patients with medial temporal lobe epilepsy.

Chronic medial temporal lobe epilepsy (MTLE) is associated with memory loss due to damage in the hippocampal system. To investigate the relationship between volume of medial temporal lobe structures and performance on neuropsychological tests, we studied 39 consecutive patients with MTLE and unilateral hippocampal atrophy (HA) determined by volumetric magnetic resonance imaging (MRI). Structures of interest comprised hippocampus, amygdala, and entorhinal, perirhinal, parahippocampal, and temporopolar cortices. The findings indicated that (1) performance was significantly worse in the group with left HA as compared with the group with right HA on general memory, verbal memory, delayed recall, and verbal fluency tests and the Boston Naming Test (BNT), and (2) the volume of the left hippocampus and also the degree of asymmetry of perirhinal cortex volume were significant and independent predictors of performance on general memory, verbal memory, and verbal fluency tests and the BNT in patients with MTLE.

Adolescent↗

PubMed2006

Individual variation in the location of the parietal eye fields: a TMS study.

Transcranial magnetic stimulation (TMS) is a popular technique that can be used to investigate the functional role of specific cortical areas with reference to a particular behavioural task. Single-cell recording studies performed in non-human primates have demonstrated that a region of the parietal lobe known as the lateral intraparietal area is specialized in the planning and control of saccadic eye movements. The homologue of this area in humans is termed the parietal eye fields (PEF) and its role in relation to saccades has previously been examined using TMS. In this paper individual variability in the functional effect of parietal TMS on the latency, amplitude and angular direction of visually-guided saccades has been assessed. By examining individual variability in the spatial distribution of scalp-based localization and brain surface anatomy and stereotaxic localizations of the PEF it was shown that the distances between the sites determined by these three methods were not negligible, which raises problems regarding the most reliable anatomical localization technique to use. An assessment of the effect of TMS on saccade metrics (latency, amplitude error and angular error) at a grid of locations over parietal cortex demonstrated a large amount of intra-individual variability in the site where TMS had most affected saccades, leading to the conclusion that there is individual variability in the functional effects of parietal TMS on saccade planning and execution. This study confirms the idea that it may be problematic to use a fixed scalp location for every participant in a study. It may in fact be more appropriate to determine TMS sites functionally on an individual basis if possible. This finding may guide further studies using TMS and saccade planning in order to optimize their capability to investigate this area and to draw meaningful biological conclusions.

Adult↗

PubMed2006

Parietal updating of limb posture: an event-related fMRI study.

The posterior parietal cortex (PPC) is thought to integrate different kinds of sensory information (e.g., visual, auditory, somatosensory) to produce multiple representations of space that are each associated with different types or combinations of action; such as saccadic eye movements and reaching or grasping movements of the upper limb. Lesion studies in monkeys and in humans have shown that reaching movements to visually defined and to posturally defined targets can be dissociated from one another; indicating that different regions of the parietal cortex may code the same movement in either extrinsic (visual) or intrinsic (postural) coordinates. These studies also suggest that regions within the posterior parietal cortex play an important role in maintaining an accurate and up-to-date representation of the current postural state of the body (the body schema). We used event-related functional magnetic resonance imaging (fMRI) to investigate those brain areas involved in maintaining and updating postural (i.e., non-visual) representations of the upper limb that participate in the accurate control of reaching movements. We show that a change in the posture of the upper-limb is associated with a significant increase in BOLD activation in only one brain region--the superior parietal cortex, particularly the medial aspect (precuneus). We note that this finding is consistent with the suggestion, based upon human neurological investigations and monkey electrophysiology, that this region of the PPC may participate in the dynamic representation of the body schema, and is the most likely location for damage leading to errors in visually guided reaching to non-foveated target locations. We also note that this brain area corresponds to a region of PPC recently identified as the human homologue of the Parietal Reach Region (PRR) observed in the monkey brain that has been thought to represent reaching movements in eye-centred coordinates.

Adult↗

PubMed2006

Voxel-based morphometry reveals excess gray matter concentration in patients with focal cortical dysplasia.

PURPOSE: Many patients with focal cortical dysplasia (FCD) continue to have seizures after surgical treatment. The usual explanation for the poor surgical outcome is the presence of residual dysplastic tissue missed by the preoperative neuroimaging investigation and therefore not resected during surgery. We apply a voxel-based morphometry (VBM) analysis to the magnetic resonance imaging (MRI) scans from patients with epilepsy and visually detected FCD to investigate whether (a) VBM is able to detect gray-matter concentration (GMC) abnormalities in patients with FCD, and (b) whether the extent of GMC abnormalities in the brain of these patients differs from the regions observed by using visual inspection. METHODS: We studied 11 patients with visually detected FCD (eight of them with histologic confirmation of FCD). The GMC from each one of these patients was compared with the mean GMC from a control group of 96 normal healthy subjects by using an optimized VBM protocol. RESULTS: Ten of 11 patients showed statistically significant GMC excess, and among patients with GMC excess, only one showed GMC excess that was not exactly correspondent to the visually detected FCD. Seven patients exhibited excess in GMC extending beyond the area of visually detected FCD. CONCLUSIONS: This preliminary neuroimaging study suggests that (a) VBM can detect GMC excess in patients with FCD, and (b) GMC excess in these patients can extend to brain areas not visually defined as abnormal. Abnormal areas detected by VBM can possibly correspond to mild malformations of cortical development, supporting the notion that the surgical refractoriness observed in patients with FCD can be due to the incomplete resection of the dysplastic tissue.

Adolescent↗

PubMed2006

T2-weighted and T2 relaxometry images in patients with medial temporal lobe epilepsy.

PURPOSE: Quantification of increased T2-weighted MRI signal that is associated with hippocampal sclerosis (HS) can be performed through (1) mean of hippocampal signal in single-echo T2 MRI and (2) hippocampal T2 relaxometry. It is not clear whether these two techniques are equivalent. In this study, we compare the hippocampal signal, detected by single-echo T2 quantification and by T2 relaxometry, in patients with medial temporal lobe epilepsy (MTLE). METHODS: We studied magnetic resonance images from 50 MTLE patients and 15 healthy subjects. We compared the quantification of a T2 signal from single echo images to T2 relaxometry, both obtained from a manually traced region of interest (ROI) in coronal slices involving the whole hippocampus. Repeated measures ANOVA was used to evaluate the differences in the distribution of the Z-scores from single-echo T2 quantification and T2 relaxometry within subjects. RESULTS: We observed a significant difference between the measurements obtained from single-echo T2 quantification and T2 relaxometry (P < .001). Measurements from head, body, and tail of the hippocampus were different (P=.04), with a significant interaction between anatomic location and type of measurement used (P= .008). Post hoc paired comparisons revealed that T2 relaxometry yielded greater Z-scores for the body (P= .002) and tail (P < .0001). CONCLUSIONS: For each subject with MTLE, T2 relaxometry was able to detect a higher signal in the body and tail of the hippocampus compared to single-echo T2. This is a possible indicator that T2 relaxometry is more sensitive in detecting T2 abnormalities within the body and tail of the hippocampus in patients with MTLE.

Analysis of Variance↗

PubMed2005

Statistical voxel-wise analysis of ictal SPECT reveals pattern of abnormal perfusion in patients with temporal lobe epilepsy.

OBJECTIVE: To investigate the pattern of perfusion abnormalities in ictal and interictal brain perfusion SPECT images (BSI) from patients with temporal lobe epilepsy (TLE). METHOD: It was acquired interictal and ictal BSI from 24 patients with refractory TLE. BSIs were analyzed by visual inspection and statistical parametric mapping (SPM2). Statistical analysis compared the patients group to a control group of 50 volunteers. The images from patients with left-TLE were left-right flipped. RESULTS: It was not observed significant perfusional differences in interictal scans with SPM. Ictal BSI in SPM analysis revealed hyperperfusion within ipsilateral temporal lobe (epileptogenic focus) and also contralateral parieto-occipital region, ipsilateral posterior cingulate gyrus, occipital lobes and ipsilateral basal ganglia. Ictal BSI also showed areas of hypoperfusion. CONCLUSION: In a group analysis of ictal BSI of patients with TLE, voxel-wise analysis detects a network of distant regions of perfusional alteration which may play active role in seizure genesis and propagation.

Adolescent↗

PubMed2005

Central neurocytoma: report of two cases.

INTRODUCTION: Central neurocytomas are rare neuroectodermal tumors believed to arise from the subependymal matrix of the lateral ventricles. CASE REPORTS: A 26-year-old woman and a 33-year-old man each had a large, heterogeneous, contrast enhancing mass in the lateral ventricles at the foramen of Monro causing bilateral hydrocephalus. The woman died after surgery, but the man is asymptomatic after three years. HISTOPATHOLOGY: Both tumors were composed of isomorphic rounded cells positive for synaptophysin, chromogranin and NSE, while some reacted for GFAP, vimentin and S-100 protein. Electron microscopy revealed neuropil-like tissue between cells, but synapses were rare.

Adult↗

PubMed2005

Imaging features and treatment of an intradural lumbar cystic schwannoma.

Spinal schwannomas are frequently observed among patients treated in a reference neurosurgery center. Cystic spinal schwannomas, however, are very scantly found. Due to its indolent behavior and benign course, the diagnosis of schwannomas may pose a challenge to the care giver, and the imaging findings can be misleading. In this article, we illustrate an example of a pauci-symptomatic 55 year-old male patient whose complaint was solely a non specific lumbar pain. Investigation revealed a large cystic lesion comprising the lower lumbar intradural space. He was then treated with microneurosurgical technique involving complete removal of the tumor and reconstruction of the dura mater. Histological and immunohistochemical diagnosis were consistent with cystic schwannoma. The patient presented with complete recovery of his symptom. In this article we aim to emphasize the clinical presentation and treatment of lumbar spine schwannomas, and to illustrate the imaging findings within this uncommon case.

Diagnosis, Differential↗

PubMed2005

Voxel-based morphometry of the thalamus in patients with refractory medial temporal lobe epilepsy.

Previous research has suggested that patients with refractory medial temporal lobe epilepsy (MTLE) show gray matter atrophy both within the temporal lobes as well as in the thalamus. However, these studies have not distinguished between different nuclei within the thalamus. We examined whether thalamic atrophy correlates with the nuclei's connections to other regions in the limbic system. T1-weighted MRI scans were obtained from 49 neurologically healthy control subjects and 43 patients diagnosed with chronic refractory MTLE that was unilateral in origin (as measured by ictal EEG and hippocampal atrophy observed on MRI). Measurements of gray matter concentration (GMC) were made using automated segmentation algorithms. GMC was analyzed both voxel-by-voxel (preserving spatial precision) as well as using predefined regions of interest. Voxel-based morphometry revealed intense GMC reduction in the anterior portion relative to posterior thalami. Furthermore, thalamic atrophy was greater ipsilateral to the MTLE origin than on the contralateral side. Here we demonstrate that the thalamic atrophy is most intense in the thalamic nuclei that have strong connections with the limbic hippocampus. This finding suggests that thalamic atrophy reflects this region's anatomical and functional association with the limbic system rather than a general vulnerability to damage.

Adolescent↗

PubMed2005

Antiepileptic drugs: a study of 1028 cases registered by the Sao Paulo Intoxication Control Center.

PURPOSE: To illustrate the profile of the cases of intoxications by antiepileptic drugs (AEDs) registered within a large urban area during the period of 1 year. METHODS: A cross-sectional observational study was performed in the Intoxication Control Center of the Sao Paulo City Hospital. We evaluated 6535 medical consults of intoxication cases involving prescription and over-the-counter drugs in 2001. We selected and analyzed the cases involving AEDs. Statistical analysis was performed in order to evaluate the frequency of different drug types and the circumstance of drug exposure. RESULTS: The most frequently observed AEDs were phenobarbital, carbamazepine, diazepam, and clonazepam. The frequency of intoxication cases among different age groups did not significantly differ according to the drug type. The circumstances involving AEDs intoxication were analogous to the circumstances of the cases of intoxication involving all other medications (p>0.05). CONCLUSIONS: There are a large number of intoxications involving AEDs. Imposing a restriction access to AEDs can be deleterious to patients that depend on AEDs, however, a strict program of AEDs distribution should be considered to reduce the cases of AED intoxication.

Age Distribution↗

PubMed2004

Long term follow-up in a patient with papillary glioneuronal tumor.

We report a case of a young female patient with a rare and recently described form of brain tumor. This patient had a history of headache, hemiparesis and motor simple partial seizures. Her investigation revealed a brain tumor involving the left frontal and parietal lobes. The radiological images showed a cystic mass with multiple nodular masses and a rim of contrast enhancement extending from the right parietal cortex to the ipsilateral ventricle and corpus callosum. The patient underwent gross resection of the lesion and the histological analysis of the surgical specimen revealed a pseudopapillary structure formed by delicate vessels intermixed with a fibrillary pattern and bordered by intense astrocytic reaction with Rosenthal fibers. These features correspond to the recently described mixed neuronal-glial neoplasm, the papillary glioneuronal tumor. The patient has been followed for five years since the surgical treatment, without evidence of tumor recurrence, confirming the indolent behavior of this type of tumor.

Adolescent↗

PubMed2004

Value of extent of hippocampal resection in the surgical treatment of temporal lobe epilepsy.

OBJECTIVE: Unilateral hippocampal atrophy is indicator of good surgical prognosis in patients with temporal lobe epilepsy (TLE). Some patients however do not become seizure free after surgery. We assessed if the extent of hippocampal and amygdala resection is associated with outcome. METHODS: Thirty patients with TLE with unilateral or clearly asymmetric hippocampal atrophy who underwent surgical treatment were evaluated concerning preoperative clinical variables and interictal EEG abnormalities. Amygdala and hippocampal resection was evaluated by post-operative MRI. We compared seizure free versus non-seizure free patients, and patients with good outcome (Engel's classes I and II) versus patients with poor outcome. RESULTS: There was significant association between the extent of hippocampal resection and the outcome. Pre-operative variables and interictal EEG abnormalities did not show relationship with outcome as documented in previous studies. CONCLUSION: The extent of hippocampal resection is associated with outcome. Incomplete resection of atrophic hippocampus may explain most surgical failures in patients with TLE due to unilateral hippocampal sclerosis.

Adult↗

PubMed2004

The role of neuroimaging in the investigation of patients with single seizures, febrile seizures, or refractory partial seizures.

Seizures are a symptom of an underlying brain disorder. The accurate identification of the nature of the disease generating the seizures facilitates treatment and can prevent further brain damage. The understanding of the physiopathology underlying the seizures has been greatly enhanced by the possibility to examine these patients with advanced forms of neuroimaging. Among different forms of investigation, neuroimaging techniques play a major role in diagnosis and decision-making in the care of patients with epilepsy. We review the contributions of current methods of imaging in the investigation of patients with single seizures, febrile seizures or refractory seizures, assessing the practical aspects, benefits, and operational costs of various neuroimaging techniques. The focus is on MRI, which is the imaging modality of choice for outpatient investigation. We also assessed the benefits from CT scans, which remain the first option for emergency seizure assessment. The aim was to evaluate how the structural, functional and metabolic information provided by modern techniques of neuroimaging decreases the need for additional investigation and speeds the management of these epileptic disorders. This makes it possible to accurately define the location and the nature of the epileptogenic lesions related to seizures.

Brain↗