Enrico Tedeschi

Dopamine D1 and D2 receptors mediate opposite functions in seizures induced by lithium-pilocarpine

The effect of selective dopamine receptor blockade on epileptic activity was tested in rats, using the lithium-pilocarpine seizure model. One day after lithium pretreatment, systemic administration of the dopamine D1 antagonist, SCH 23390, prevented the convulsive activity induced by either 10 or 15 mg/kg of pilocarpine in a dose-dependent manner as revealed by behavioral and electroencephalographic alterations. No anticonvulsant effect was observed when SCH 23390 was injected at the same time as lithium and 24 h prior to pilocarpine. Furthermore, the D2 antagonists, raclopride and haloperidol, potently reduced the threshold for convulsions induced by 10 mg/kg of pilocarpine, following lithium pretreatment. Neither dopamine D1 nor D2 antagonists altered the limbic stereotypies induced by pilocarpine, supporting the view that the dopamine system is primarily involved in the mechanisms of convulsion generation and seizure spreading. These results indicate that dopamine receptor subtypes exert opposite functions on the regulation of convulsive activity.

Stereotaxy-Based Regional Brain Volumetry Applied to Segmented MRI: Validation and Results in Deficit and Nondeficit Schizophrenia

A method for postprocessing of segmented routine brain MRI studies providing automated definition of major structures (frontal, parietal, occipital, and temporal lobes; cerebellar hemispheres; and lateral ventricles) according to the Talairach atlas is presented. The method was applied to MRI studies from 25 normal subjects (NV), 14 patients with deficit schizophrenia (DS), and 14 with nondeficit schizophrenia (NDS), to evaluate their gray matter and CSF regional volumes. The two patient groups did not differ in mean age at illness onset, duration of illness, severity of psychotic symptoms, or disorganization; DS had more severe avolition and worse social functioning than NDS. For validation purposes, brain structures were manually outlined on original MR images in 10 studies, thus obtaining reference measures. Manual and automated measures were repeated 1 month apart to measure reproducibilities of both methods. The automated method required less than 1 min/operator per study vs more than 30 min for manual assessment. Mean absolute difference per structure between the two techniques was 4.8 ml. Overall reproducibility did not significantly differ between the two methods. In subjects with schizophrenia, a significant decrease in GM and increase in CSF were found. GM loss was confined to frontal and temporal lobes. Lateral ventricles were significantly larger bilaterally in NDS compared to NV and only on the right in NDS compared to DS. The finding of greater structural brain abnormalities in NDS adds to the evidence that deficit schizophrenia does not represent just the more severe end of the schizophrenia continuum.

In vivo dentate nucleus MRI relaxometry correlates with previous administration of Gadolinium-based contrast agents

AbstractObjectivesTo evaluate changes in T1 and T2* relaxometry of dentate nuclei (DN) with respect to the number of previous administrations of Gadolinium-based contrast agents (GBCA).MethodsIn 74 relapsing-remitting multiple sclerosis (RR-MS) patients with variable disease duration (9.8±6.8 years) and severity (Expanded Disability Status Scale scores:3.1±0.9), the DN R1 (1/T1) and R2* (1/T2*) relaxation rates were measured using two unenhanced 3D Dual-Echo spoiled Gradient-Echo sequences with different flip angles. Correlations of the number of previous GBCA administrations with DN R1 and R2* relaxation rates were tested, including gender and age effect, in a multivariate regression analysis.ResultsThe DN R1 (normalized by brainstem) significantly correlated with the number of GBCA administrations (p<0.001), maintaining the same significance even when including MS-related factors. Instead, the DN R2* values correlated only with age (p=0.003), and not with GBCA administrations (p=0.67). In a subgroup of 35 patients for whom the administered GBCA subtype was known, the effect of GBCA on DN R1 appeared mainly related to linear GBCA.ConclusionsIn RR-MS patients, the number of previous GBCA administrations correlates with R1 relaxation rates of DN, while R2* values remain unaffected, suggesting that T1-shortening in these patients is related to the amount of Gadolinium given.Key Points• In multiple sclerosis, previous Gadolinium administrations correlate with dentate nuclei T1 relaxometry. • Such correlation is linked to linear Gadolinium chelates and unrelated to disease duration or severity. • Dentate nuclei T2* relaxometry is age-related and independent of previous Gadolinium administrations. • Changes in dentate nuclei T1 relaxometry are not determined by iron accumulation. • MR relaxometry can quantitatively assess Gadolinium accumulation in dentate nuclei.

Measurement of global brain atrophy in Alzheimer's disease with unsupervised segmentation of spin-echo MRI studies.

In 16 patients with probable Alzheimers disease (AD; NINDS criteria, age range 56–78 years), gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) absolute and fractional volumes were measured with an unsupervised multiparametric post‐processing segmentation method based on estimates of relaxation rates R1, R2 (R1 = 1/T1; R2 = 1/T2) and proton density [N(H)] from conventional spin‐echo studies (Alfano et al. Magn. Reson. Med. 1997;37:84–93). Global brain atrophy, and GM and WM fractions significantly correlated with Mini‐Mental Status Examination and Blessed Dementia Scale scores. Compared with normals, brain compartments in AD patients showed decreased GM (−6.84 ± 1.58%) and WM fractions (−9.79 ± 2.47%) and increased CSF fractions (+58.80 ± 10.37%). Changes were more evident in early‐onset AD patients. In AD, measurement of global brain atrophy obtained by a computerized procedure based on routine magnetic resonance studies could complement the information provided by neuropsychological tests for the assessment of disease severity. J. Magn. Reson. Imaging 2000;11:260–266.

Functional characterization of brain tumors: An overview of the potential clinical value

Early detection and characterization are still challenging issues in the diagnostic approach to brain tumors. Among functional imaging techniques, a clinical role for positron emission tomography studies with [18F]-fluorodeoxyglucose and for single photon emission computed tomography studies with [201Tl]-thallium-chloride has emerged. The clinical role of magnetic resonance spectroscopy is still being defined, whereas functional magnetic resonance imaging seems able to provide useful data for presurgical localization of critical cortical areas. Integration of morphostructural information provided by computed tomography and magnetic resonance imaging, with functional characterization and cyto-histologic evaluation of biologic markers, may assist in answering the open diagnostic questions concerning brain tumors.

Magnetic resonance features of pyogenic brain abscesses and differential diagnosis using morphological and functional imaging studies: a pictorial essay.

The aim of this paper is to illustrate the potential of magnetic resonance imaging (MRI) in diagnosis, differential diagnosis, treatment planning and evaluation of therapy effectiveness of pyogenic brain abscesses, through the use of morphological (or conventional) and functional (or advanced) sequences. Conventional MRI study is useful for the identification of lesions, to determine the location and morphology and allows a correct hypothesis of nature in the most typical cases. However, the differential diagnosis from other brain lesions, such as non-pyogenic abscesses or necrotic tumors (high-grade gliomas and metastases) is often only possible through the use of functional sequences, as the measurement of diffusion with apparent diffusion coefficient (DWI-ADC), proton magnetic resonance spectroscopy ((1)H-MRS) and perfusion weighted imaging (PWI), which complement the morphological sequences and provide essential information on structural, metabolic and hemodynamic characteristics allowing greater neuroradiological confidence. Modern diagnostic MRI of pyogenic brain abscesses cannot be separated from knowledge, integration and proper use of the morphological and functional sequences.

Congenital Agenesis/Aplasia of the Internal Carotid Arteries: MRA and SPECT Findings

Single photon emission CT (SPECT) and MRI and MR angiography studies were performed in a patient with right internal carotid artery (ICA) agenesis, left ICA aplasia, and multiple associated vascular abnormalities identified with digital subtraction angiography. Magnetic resonance angiography provided an excellent depiction of the extra- and intracranial vascular abnormalities. No evidence of brain lesions or perfusion defects was demonstrated with MRI and SPECT, despite the markedly altered vascular anatomy.

Different thallium-201 single-photon emission tomographic patterns in benign and aggressive meningiomas

To evaluate the possibility of preoperatively obtaining an index of aggressiveness for intracranial meningiomas, we prospectively studied 22 patients with computed tomography or magnetic resonance imaging evidence of meningeal tumour, using single-photon emission tomography (SPET) of the brain and thallium-201 (201Tl). On a brain-dedicated SPET scanner, a rapid acquisition protocol with early, short scans was started simultaneously with the intravenous administration of 111 MBq201Tl, covering the initial intratumoral distribution of the tracer. Twenty minutes post injection, a delayed SPET scan was also obtained. On the reconstructed and attenuation-corrected images we calculated the201Tl concentration in tumour and normal contralateral brain tissue, and compared intratumoral tracer concentration in the initial and the final part of the rapid acquisition protocol. Benign and malignant meningiomas were classified as such based on histological examination. In malignant lesions, the ratio of the201Tl concentration at 2–4 min post injection to that at 14–16 min was found to be significantly higher than in non-aggressive neoplasms (mean±1 SD: 1.14±0.31 and 0.56±0.13, respectively,P <0.01). Conversely, in the delayed scan, most lesions showed high tracer concentration, and the two groups could not be distinguished. In addition, three recurrent meningiomas displayed the same imaging behaviour as the malignant group, i.e. had similar201Tl concentration values at 2–4 and at 14–16 min. Our findings suggest that the comparative assessment of intratumoral201T1 concentration at 2–4 and at 14–16 min post injection could provide a fast, simple method to differentiate preoperatively intracranial meningiomas with different biological behaviour.

Endovascular treatment of vertebro-vertebral arteriovenous fistula. A report of three cases and literature review.

This report describes endovascular approaches for occlusion of vertebro-vertebral arteriovenous fistula (W-AVF) in a series of three cases and a review of the literature. Complete neuroimaging assessment, including CT, MR and DSA was performed in three patients (two female, one male) with W-AVF. Based on DSA findings, the W-AVF were occluded by endovascular positioning of detachable balloons (case 1), coils (case 2), or a combination of both (case 3) with parent artery patency in two out of three cases. In this small series, endovascular techniques for occlusion of W-AVF were safe and effective methods of treatment. To date, there are no guidelines on the best treatment for W-AVF. Detachable balloons, endovascular coiling, combined embolization procedures could all be considered well-tolerated treatments.

Improving signal-to-noise ratio in susceptibility weighted imaging: A novel multicomponent non-local approach

In susceptibility-weighted imaging (SWI), the high resolution required to obtain a proper contrast generation leads to a reduced signal-to-noise ratio (SNR). The application of a denoising filter to produce images with higher SNR and still preserve small structures from excessive blurring is therefore extremely desirable. However, as the distributions of magnitude and phase noise may introduce biases during image restoration, the application of a denoising filter is non-trivial. Taking advantage of the potential multispectral nature of MR images, a multicomponent approach using a Non-Local Means (MNLM) denoising filter may perform better than a component-by-component image restoration method. Here we present a new MNLM-based method (Multicomponent-Imaginary-Real-SWI, hereafter MIR-SWI) to produce SWI images with high SNR and improved conspicuity. Both qualitative and quantitative comparisons of MIR-SWI with the original SWI scheme and previously proposed SWI restoring pipelines showed that MIR-SWI fared consistently better than the other approaches. Noise removal with MIR-SWI also provided improvement in contrast-to-noise ratio (CNR) and vessel conspicuity at higher factors of phase mask multiplications than the one suggested in the literature for SWI vessel imaging. We conclude that a proper handling of noise in the complex MR dataset may lead to improved image quality for SWI data.