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Biomedical subjects

P Pantano

Publications and source records attributed to P Pantano.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cortical control of optokinetic nystagmus in humans: a positron emission tomography study.

Positron emission tomography (PET) was used to address the issue of physiological changes in the cerebral cortex associated to optokinetic nystagmus (OKN) in humans. We studied regional cerebral blood flow in eight volunteers during reflexive induction of OKN by a pattern of dots moving unidirectionally (toward the left side). We used two control conditions, with subjects passively viewing either stationary or incoherently moving dots. This paradigm was designed in order to differentiate the OKN-related activations from blood flow changes related to visual motion. When compared with the stationary condition, OKN activated a set of occipital areas known to be sensitive to visual motion. Bilateral activation was found in the striate cortex (V1) and the parieto-occipital fissure, while area V5, the intraparietal sulcus, and the pulvinar were activated only in the left hemisphere. When compared with incoherent motion, OKN activated the V1 and the parieto-occipital fissure bilaterally and the right lingual gyrus, while a signal decrease was observed in the V5 region in both hemispheres. No significant signal changes were found in areas implicated in saccades or in processing vestibular information. These results indicate that processing of OKN-related information is associated with neural activity in a specific set of visual motion areas and suggest that this network can be asymmetrically activated by a strictly unidirectional stimulation. Results are also discussed in terms of the specific kinds of OKN-related information processing subserved by each area in this network.

Adult↗
PubMed1999

The role of MRI in dementia.

Neuroimaging techniques aimed at studying structural changes of the brain may provide useful information for the diagnosis and the clinical management of patients with dementia. Magnetic resonance imaging (MRI) may show abnormalities amenable to surgical treatment in a significant percentage of patients with cognitive impairment. MRI may also assist the differential diagnosis in dementia associated with metabolic or inflammatory diseases.MRI has the potential to detect focal signal abnormalities which may assist the clinical differentiation between Alzheimer's disease (AD) and vascular dementia (VaD). Severe temporal atrophy, hyperintensities involving the hippocampal or insular cortex, and gyral hypointense bands are more frequently noted in AD. Basal ganglionic/thalamic hyperintense foci, thromboembolic infarctions, confluent white matter and irregular periventricular hyperintensities are more common in VaD. The high sensitivity of MRI in detecting T2 hyperintense lesions and the low specificity off white matter lesions have resulted in a poor correlation between MRI findings and both neuropathological and clinical manifestations. In particular, MRI has disclosed a series of white matter focal changes in the elderly population, which are not necessarily associated with cognitive dysfunction. The recent advent of a new MRI method sensitive to the microstructural changes of white matter, the so-called diffusion tensor imaging, may be helpful in correlating clinical manifestations with white matter abnormalities.

Alzheimer Disease↗
PubMed1999

Linguistic impairment after right cerebellar stroke: a case report.

Increasing evidence suggests the involvement of the cerebellum in non-motor functions. We describe a patient who presented speech deficits after a right cerebellar infarction without other cognitive impairments. 99mTc-HMPAO single-photon emission computed tomography showed a marked hypoperfusion in the right cerebellar hemisphere, but did not show crossed cerebellar- cerebral diaschisis. The absence of neuroradiological evidence of structural supratentorial lesions supports the cerebellar role in modulating not only the motor system, but also higher order functions.

Cerebellum↗
PubMed1999

Delayed increase in infarct volume after cerebral ischemia: correlations with thrombolytic treatment and clinical outcome.

BACKGROUND AND PURPOSE: Growing experimental evidence indicates that the development of cerebral ischemic damage is slower than previously believed. The aims of this work were (1) to study the evolution of CT hypoattenuation between 24 to 36 hours and 7 days in ischemic stroke patients; (2) to evaluate whether thrombolytic treatment given within 6 hours of stroke affects delayed infarction evolution; and (3) to investigate possible correlations between lesion volume changes over time and clinical outcome. METHODS: Of 620 patients included in the European Cooperative Acute Stroke Study 1 (ECASS1), we selected 450 patients whose control CT scans at day 1 (CT1) and day 7 (CT7) were available. They had been randomly divided into 2 groups: 206 patients had been treated with rtPA and 244 with placebo. CT1 and CT7 were classified according to the location of the infarct. The volume of CT hypoattenuation was measured using the formula AxBxC/2 for irregular volumes. The 95% confidence interval of inter- and intrarater variability was used to determine whether significant changes in lesion volume had occurred between CT1 and CT7. Clinical severity was evaluated by means of the Scandinavian Stroke Scale (SSS) at entry (SSS0) and at day 30 (SSS30). RESULTS: Mean lesion volumes were significantly (P<0.0001) higher at day 7 than at day 1 in all the subgroups of patients and particularly in patients with a subcortical lesion. Of the 450 patients studied, 287 (64%) did not show any significant change in lesion volume between CT1 and CT7, 143 (32%) showed a significant increase and the remaining 20 (4%) a significant decrease. No significant correlation was observed between treatment and lesion evolution between CT1 and CT7. Both clinical scores (SSS0 and SSS30) and degree of neurological recovery were significantly (P<0.05) lower in the subgroup of patients with a significant lesion volume increase than in the other 2 groups. CONCLUSIONS: In approximately two thirds of patients, infarct size is established 24 to 36 hours after stroke onset, whereas in the remaining one third, changes in lesion volume may occur later than the first 24 to 36 hours. Many factors may be responsible for delayed infarct enlargement and for a lower degree of clinical recovery, both of which may occur despite early recombinant tissue plasminogen activator treatment.

Aged↗
PubMed1999

Imaging of autoimmune diseases.

Autoimmune diseases represent a heterogeneous group of pathologies with a wide range of immunological changes and clinical presentations. The clinical onset of the disease commonly occurs when signs and symptoms of target tissue hypofunction appear; complications can also be present. The aim of an imaging diagnostic technique in this context is to correctly evaluate the disease extent and severity for appropriate treatment and to follow up the efficacy of therapy. In addition, identification of subjects at risk and the preclinical diagnosis may allow disease prevention. Ultrasound (US), conventional radiology and computed tomography (CT) are often used for a detailed morphological study of tissues involved; magnetic resonance (MRI) may also demonstrate biochemical and structural tissue changes. Nuclear medicine techniques are known for their sensitivity and specificity and in recent years an expanding field is represented by the development of radiolabelled receptor ligands. New radiopharmaceuticals able to bind in vivo to specific receptors have been introduced allowing the non invasive detection of changes in affected tissues. The relevant criteria to choose different diagnostic approaches in several autoimmune diseases are discussed in this review. In particular the role and contribution of nuclear medicine for the study of autoimmune diseases have been described.

Antibodies, Monoclonal↗
PubMed1998

Radiological assessment of necrosis in glioblastoma: variability and prognostic value.

In a previous study, we found that the extent of necrosis was the only radiological feature which correlated significantly with survival in patients with glioblastoma. The aim of this paper was to evaluate the variability and prognostic value of the extent of the necrotic area as seen on contrast-enhanced MRI and CT in a larger series. We studied 72 patients who underwent surgical removal of supratentorial glioblastomas and had CT and/or MRI with contrast medium before surgery; 38, all undergoing the same treatment (surgery plus radiotherapy), were followed clinically. Necrosis within the tumour varied greatly, ranging from none (only 1 case) to involvement of 76% of the tumour. Survival data in the subgroup suggested that only patients with a small area of necrosis (less than 35% of the tumour) had a significantly longer survival time. When necrosis involved more than 35% of the mass, patients had a shorter survival time, without any further correlation with the extent of necrosis.

Brain↗
PubMed1997

In situ fluorescence imaging of localized corrosion with a pH-sensitive imaging fiber.

A fiber-optic pH-imaging sensor array capable of both visualizing remote corrosion sites and measuring local chemical concentrations at these sites was applied to realtime corrosion monitoring. The imaging fiber's distal face, containing an immobilized pH-sensitive fluorescent dye, was brought into contact with metal surfaces submerged in aqueous buffers and fluorescence images were acquired as a function of time. Heterogeneous fluorescence signals were observed due to both pH increases at cathodic surface sites and pH decreases at anodic surface sites. These fluorescence signals showed both localization and rates of corrosion activity. Three corrosion processes were investigated, galvanic corrosion at a copper/aluminum interface and crevice corrosion and pitting at a stainless steel surface. The spatial resolution of the technique was limited by proton/hydroxide diffusion and the diameter of the individually clad optical fibers comprising the imaging bundle.

Corrosion↗
PubMed1997

Supratentorial diffuse astrocytic tumours: proposal of an MRI classification.

The aim of this study was to obtain an MRI severity-related classification of diffuse astrocytic tumours able to integrate the histological data in the grading of such tumours. We studied presurgical MR images of 91 patients with a histological diagnosis of astrocytoma, anaplastic astrocytoma and glioblastoma. A score ranging from 1 to 3 was assigned by two independent readers to each of the following MR features: oedema, mass effect, contrast enhancement, borders, signal homogeneity, necrosis, haemorrhage and flow void. Statistical analysis showed significant differences in the mean MRI scores between the three histological grades. Contrast enhancement was found to be the best predictor of the histological grade followed by necrosis, signal homogeneity and border scores. This classification represents a simple and reproducible means of carefully evaluating some macroscopic characteristics of these tumours. It could be used to integrate histological data especially in cases in which tissue sampling defects may affect the validity of this examination.

Adult↗
PubMed1997

Tonic pain: a SPET study in normal subjects and cluster headache patients.

Whether the pathogenesis of cluster headache (CH) is peripheral or central is still matter of debate. An involvement of central structures related to pain perception and modulation, which also causes an alteration of the physiological pattern of pain perception in CH, has been hypothesized. We investigated the pattern of brain response to pain in normal subjects and CH patients by evaluating the cerebral blood flow (CBF) changes using an experimental model of tonic aching pain stimulation, the cold water pressor test (CWPT). CBF was assessed quantitatively by the Xe-133 inhalation method and single photon emission tomography (SPET), at rest and during CWPT, as previously described (Di Piero et al., 1994). CWPT was performed in 12 volunteers and in seven patients with CH. All the CH patients had a left-sided headache and were studied in a headache-free phase out of the cluster period. During CWPT, volunteers showed a significant CBF increase in the contralateral primary sensorimotor (P < 0.001), frontal (P < 0.01) and temporal (P < 0.002) regions and thalamus (P < 0.01) and in the ipsilateral temporal (P < 0.005) and anterior cingulate (P < 0.01) regions. During left-hand stimulation (ipsilateral to the headache side) by CWPT in CH patients, CBF changes were significantly lower than those observed in volunteers in the contralateral primary sensorimotor region (P < 0.0005) and thalamus region (P < 0.01). There were no significant differences in the brain response observed during the stimulation of the hand contralateral to the headache side. In conclusion, in a headache-free phase out of the cluster period, the pattern of cerebral activation during tonic pain stimulation of the hand ipsilateral to the headache side is critically modified in CH patients in areas which are probably involved in the detection of the stimulus intensity. This modification may reflect a marker of a biological modification of the pain conveyance system. The fact that it is also present out of the active period of the disease, suggests a possible involvement of central tonic pain mechanisms in the pathogenesis of CH.

Adult↗
PubMed1997

Activation of the NADPH oxidase in human fibroblasts by mechanical intrusion of a single cell with an ultramicroelectrode.

We present here a real-time and single cell study of an oxidative stress mechanism in human fibroblasts. Hydrogen peroxide released by a single normal or SV40-transformed human fibroblast was detected at the surface of an ultramicroelectrode while puncturing the cell membrane with the ultramicroelectrode tip itself or with a micropipette. This mechanical intrusion induced the emission of large quantities (10(-15)-10(-14) mol) of H2O2 by the cell with a very short time delay (<0.5 s). We show that this H2O2 production was an active neo-production by fibroblasts when the membrane was stressed by the cellular puncture and is a model which could mimic similar effects as particle (virus, bacteria, etc.) intrusion into the cell. Cell incubations in the presence of some inhibitors of the different NADPH oxidase enzymes, using ultramicroelectrode measurements of the short time effects (<20 min) let us believe that an NADPH oxidase-like enzyme may be implicated in this induced-H2O2 generation. Phenylarsine oxide (PAO), a specific NADPH oxidase inhibitor, at concentrations between 0.5-50 microM seemed to quickly kill the transformed cells preferentially to the normal cells, pointing out for the future a possible anti-cancerous chemotherapic use.

Antioxidants↗
PubMed1996

Involvement of the limbic system in multiple sclerosis patients with depressive disorders.

This study investigates the relationship between depression and both anatomic and cerebral blood flow abnormalities in multiple sclerosis (MS) patients. Ten nondepressed MS patients were compared with 10 depressed MS patients matched for age, sex, and functional disability. Both groups were evaluated by means of neuropsychological tests, magnetic resonance imaging, and single-photon emission tomography imaging. There was no difference between the two groups with regard to the global cognitive score. Magnetic resonance imaging data showed no significant differences in the number, side, location, and area of the demyelinating lesions between the two groups; however, regional cerebral blood flow asymmetries in the limbic cortex did distinguish the two groups. Analysis of variance showed a significant effect of depression on the perfusion asymmetries in the limbic cortex. Finally, perfusion asymmetries in limbic cortex significantly correlated with depression test scores. Our findings suggest that depression in MS patients could be induced by a disconnection between subcortical and cortical areas involved in the function of the limbic system.

Adult↗
PubMed1996

Relationship between thallium-201 uptake by supratentorial glioblastomas and their morphological characteristics on magnetic resonance imaging.

Single-photon emission tomography (SPET) with thallium-201 is used in the assessment of patients with gliomas because the amount of 201Tl accumulated by the tumoral cells increases in proportion to the degree of tumour malignancy, thus making it possible to differentiate high-grade from low-grade gliomas or recurrences from radiation necrosis. However, in large areas of tissue such as those examined in 201Tl SPET studies, the uptake of 201Tl may vary considerably even in tumours with the same histological diagnosis, as occurs in glioblastomas (GBMs). In order to evaluate the possible influence of the macroscopic characteristics of tumours on 201Tl uptake, we studied a series of 13 patients with histologically proven GBMs, comparing magnetic resonance imaging (MRI) parameters such as tumour dimensions, perilesional oedema, intratumoral necrosis and contrast enhancement with the degree of 201Tl uptake. The patients underwent both 201Tl SPET and MRI before surgery. The 201Tl index (tumour/contralateral unaffected brain) was calculated using two different region of interest (ROI) methods: the first employed irregular large ROIs (3.2+/-13.9 cm2) including pixels with more than 50% maximum activity; the second employed regular square small ROIs (2.7 cm2) centered on the maximum activity of the lesion. Of the MRI morphological parameters studied, only necrosis significantly reduced the degree of 201Tl uptake in GBMs when larger ROIs were used. However, by using small regular ROIs the influence of necrosis on 201Tl uptake was found to be less relevant. Since necrosis is related to tumour proliferative activity and represents a negative prognostic factor in astrocytoma, a possible underestimation of 201Tl uptake due to intratumoral necrosis must be carefully evaluated.

Brain↗
PubMed1996

Supratentorial glioblastoma: neuroradiological findings and survival after surgery and radiotherapy.

Few studies have attempted to correlate neuroimaging with outcome in patients with glioblastoma. Our aim was to evaluate the relationship between neuroradiological findings and survival in these patients. We studied 18 consecutive patients with glioblastoma who had undergone surgery and radiotherapy. We assessed the following features, using preoperative CT and/or MRI: tumour size, extent of necrotic area within the mass, extent of perifocal oedema and contrast enhancement. The mean survival was 14.2 +/- 5 months (range 6-22). The extent of radiological evidence of necrosis within the mass correlated significantly with survival time, whereas tumour size, perifocal oedema and contrast enhancement did not.

Aged↗
PubMed1996

Motor recovery after stroke. Morphological and functional brain alterations.

The aim of this study was to evaluate the relationships of morphological and CBF patterns with both the severity and the evolution of the motor deficit in the late phase of stroke and, in particular, to identify morphological and/or functional brain alterations associated with a persistent severe motor deficit or a poor, delayed motor recovery. We analysed CT/MRI and single photon emission tomography (SPET) findings from 37 patients studied in the chronic phase of stroke (mean duration +/- SD = 3.6 +/- 1.6 months), whom we were able to follow clinically for a period of 3 months. The eventual degree of motor recovery correlated significantly (negatively) with the time since stroke at entry, but not with the severity of neurological impairment at entry. The volume, side and location (cortical or subcortical) of the infarct did not correlate with either the severity or the evolution of the motor deficit. Patients with a CT/MRI lesion of the parietal lobe (n = 8) showed a more severe motor deficit than those with other cortical locations. The severity of the motor deficit correlated significantly (negatively) with CBF values in the supplementary motor area (SMA) and parietal areas of the damaged hemisphere, and in the contralateral undamaged primary motor cortex. The degree of motor improvement correlated significantly (positively) with CBF values in the contralateral undamaged thalamus, lentiform and caudate nuclei, and premotor cortex. In the late phase of stroke, the severity of the motor deficit may be positively associated with the functional impairment of associative parietal and frontal areas of the damaged hemisphere. The functional impairment of the basal ganglia-frontal network in the undamaged hemisphere seems to be related to a poor, delayed motor recovery.

Aged↗
PubMed1995

Presurgical integrated MRI/SPECT localization of the sensorimotor cortex in a patient with a low-grade astrocytoma in the rolandic area.

We describe the case of a young man who, despite the presence of a tumour in the left sensorimotor cortex, exhibited no motor deficit. Integrated MRI/SPECT-CBF study during motor activation was aimed at determining which cerebral areas were involved in movement execution in this patient and their relationship with the tumour. CBF changes during motor activation were located in two motor areas: anteriorly and medially to the tumour in the left frontal lobe (+29%) and in the right medial frontal cortex (+43%). Integrated MRI/SPECT images provided both an anatomical and functional definition of the motor areas in a patient with a rolandic tumour and could prove useful in determining preoperatively an appropriate surgical strategy.

Adolescent↗