Sergio Bressi

Cross validation of the factor structure of the 20-item Toronto Alexithymia Scale: An Italian multicenter study

The 20-item Toronto Alexithymia Scale (TAS-20) has been shown in previous research to measure a general dimension of alexithymia with three intercorrelated factors. This study evaluated the reliability and factorial validity of an Italian translation of the TAS-20 in a group of normal adults (N = 206) and in a mixed group of medical and psychiatric outpatients (N = 642). Using confirmatory factor analyses, the previously established three-factor model of the TAS-20 was found to be replicable in both groups. In addition, the Italian TAS-20 demonstrated adequate estimates of internal reliability and test-retest reliability. Although evaluation of the convergent, discriminant, and concurrent validity of the TAS-20 is required in Italian populations, the present results support the use of the Italian translation of the scale for clinical and research purposes.

Different neural systems for the recognition of animals and man-made tools

Using positron emission tomography, we mapped brain activity in normal volunteers during the recognition of visual stimuli representing living (animals) and nonliving (artefacts) entities. The subjects had to decide whether pairs of visual stimuli were different representations of the same object, or different objects. Animal recognition was associated with activations in the inferior temporo-occipital areas, bilaterally, whereas artefact recognition engaged a predominantly left hemispheric network, involving the left dorsolateral frontal cortex. These findings, which concur with clinical observations in neurological patients, provide in vivo evidence for a fractionation of the neural substrates of semantic knowledge in man.

Metabolic Impairment in Human Amnesia: A PET Study of Memory Networks

Human amnesia is a clinical syndrome exhibiting the failure to recall past events and to learn new information. Its “pure” form, characterized by a selective impairment of long-term memory without any disorder of general intelligence or other cognitive functions, has been associated with lesions localized within Papezs circuit and some connected areas. Thus, amnesia could be due to a functional disconnection between components of this or other neural structures involved in long-term learning and retention. To test this hypothesis, we measured regional cerebral metabolism with 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) and positron emission tomography (PET) in 11 patients with “pure” amnesia. A significant bilateral reduction in metabolism in a number of interconnected cerebral regions (hippocampal formation, thalamus, cingulate gyrus, and frontal basal cortex) was found in the amnesic patients in comparison with normal controls. The metabolic impairment did not correspond to alterations in structural anatomy as assessed by magnetic resonance imaging (MRI). These results are the first in vivo evidence for the role of a functional network as a basis of human memory.

Influence of Clinical Variables on Neuropsychological Performance in Multiple Sclerosis

The effects of age, educational level, duration and course of the disease, physical disability and mood status on several cognitive functions (short- and long-term memory, frontal functions, attention, language and visuospatial skills) have been evaluated in 42 multiple sclerosis (MS) patients. The Hamilton Depression Rating Scale (HDRS) scores and a secondary progressive disease course significantly influenced neuropsychological performance. Factorial analysis revealed that indexes of (1) frontal function impairment, (2) long-term verbal memory and language function impairment, and (3) visuospatial short- and long-term memory and visuoperceptive function impairment accounted for 85% of the variance in neuropsychological performance. Only the first factor was significantly related to the presence of depressive symptomatology, as assessed by the HDRS. These results indicate that both the course of the disease and the presence of affective disorders must be taken into account when evaluating the natural history of cognitive impairment in MS and suggest that depressive symptomatology and cognitive dysfunction in MS are related to the involvement of at least partially overlapping anatomofunctional circuits.

Interscanner variation in brain MRI lesion load measurements in MS: Implications for clinical trials

We evaluated the effect of interscanner variation on brain MRI-measured lesion volumes and measurement reproducibility in MS. Twenty clinically definite MS patients were each scanned on two or three scanners (a total of 14 scanners were used). In addition, a formalin-fixed MS brain was studied on eight scanners from different manufacturers and with different field strengths. For the formalin-fixed MS brain, on each machine we obtained two scans with slice thicknesses of 5 and 3 mm. Only 5-mm-thick slices were obtained from patients. The lesion volume present on each scan was evaluated three times by a single observer in random order, using a local thresholding technique. In two groups of eight patients scanned on machines with different field strengths, the mean lesion volumes present on scans obtained at 1.5 T were significantly higher than those measured on scans obtained with machines operating at 0.5 and 1.0 T (p < 0.01). When a single observer repeatedly evaluated the same scan, a median intraobserver agreement of 98.7%(95% CI, 97.9 to 99.1) was achieved. However, when the observer evaluated the scans from different MRI scanners, the agreement (an interscanner agreement) fell to 91.1% (CI, 90.2 to 94.1). When only scanners operating at 1.5 T were considered, the median interscanner agreement was 96.7% (CI, 95 to 97.5). Also, for the formalin-fixed MS brain, the intraobserver agreements obtained with both slice thicknesses were significantly higher than the corresponding interscanner agreements. The interscanner agreement, but not the intraobserver agreement, obtained with a slice thickness of 3 mm was higher than that obtained with a slice thickness of 5 mm. Our results indicate that lesion volume measurements in MS are influenced significantly by the use of different MR scanners and that a patient included in a serial study should be always scanned with the same MR machine using 3-mm thick slices.

Correlations between cognitive impairment, middle cerebral artery flow velocity and cortical glucose metabolism in the early phase of Alzheimer's disease

In a previous transcranial Doppler (TCD) study, we demonstrated a decrease in blood flow velocity in the proximal tract of the middle cerebral artery (MCA) in patients with Alzheimers disease (AD). In these patients there was also an asymmetry in blood flow velocity which positively correlated with the cognitive asymmetry often seen in the early phase of AD. In this study we found a correlation between the absolute values and asymmetry indexes of MCA blood flow velocity with adjusted metabolic values and asymmetry indexes of the relative cortical frontotemporoparietal (FTP) areas, evaluated by FDG-PET, and with neuropsychological asymmetry indexes. Patients with prevalent visuospatial deficits (right hemisphere dysfunction) showed significant decreases in right MCA blood flow velocity and right FTP cortical glucose hypometabolism, whereas in patients with prevalent language deficits (left hemisphere dysfunction), these signs were observed on the other side. In AD patients, the decrease of blood flow velocity in MCA might be due to reduced metabolic demands in the temporoparietal cortical areas primarily affected by AD.

Crossed aphasia: a PET follow up study of two cases.

Two cases of aphasia after right hemispheric stroke in right handed patients are described. The first patient had a severe mixed transcortical aphasia, apraxia and neglect after a lesion involving the right lenticular nucleus and periventricular white matter; aphasia was still present after three months. The second patient had a mild, transient fluent aphasia after a small right hemispheric periventricular lesion. Studies with [18F]FDG and positron emission tomography (PET) showed functional depression extending to the structurally unaffected left hemisphere in both patients in the acute stage. After three months, in the patient with persistent aphasia, metabolism was still reduced in the right hemisphere, with some recovery of hypometabolism on the left, while metabolic values had returned to normal in the patient with full language recovery. A close parallelism between glucose metabolism and clinical course in crossed aphasia is shown, as well as the presence of a functional involvement of the structurally unaffected left hemisphere in the acute stage.

Inter-rater variability in reporting enhancing lesions present on standard and triple dose gadolinium scans of patients with multiple sclerosis

In this study we evaluated and compared the inter-rater variabilities in detecting enhancing lesions in patients with MS after injection of a standard dose (s.d.) and a triple dose (TD) of gadolinium (Gd). Enhanced magnetic resonance imaging (MRI) were obtained in 15 patients, consisting of T1weighted images 5 to 7 min after the injection of the s.d. (0. I mmol/kg) of Gd and, after an interval of 6 to 24 h, 5 to 7 min after the injection of the TD (0.3 mmol/kg). An additional scan I h after the TD injection (delayed scanning - DS) was obtained in 11 patients. The scans were independently evaluated in a random order by four observers. Lesions were counted and scored according to size and location. The level of inter-observer concordance was very high for reporting the total numbers of enhancing lesions, their sizes and sites for the three experimental conditions. No significant differences were found in inter-observer variability in reporting the total number of enhancing lesions and their location in different brain sites in the three conditions. Our data indicate that the gain in sensitivity in detecting enhancing lesions in MS with the TD is not counteracted by a loss in reproducibility. This is important in planning clinical trials in which the number of enhancing lesions is used as a measure of outcome.

Pattern Visual Evoked Potential Mapping in Alzheimers Disease Correlations with Visuospatial Impairment

We evaluated pattern visual evoked potentials (PVEPs) in patients with Alzheimers disease (AD) and correlated the neurophysiological results with visuospatial performances in order to understand better the underlying causes of visual disturbances. Latencies and topographical distribution of PVEP components were evaluated in 20 AD patients who underwent an extensive battery of neuropsychological tests. Mean latencies of N70 and P100 were normal in AD patients, while mean latencies of N140 and P200 were significantly increased in comparison with age-matched healthy controls. The topographical distribution of PVEP components did not show any significant difference between the two groups. Visuospatial impairment was detected in 8 patients (40%). Statistically significant positive correlations were observed between P200 amplitude (posterior right hemisphere mean z score) and performance in visuospatial tests. Our data are consistent with a sparing of foveal retinocortical pathways and with the selective dysfunction of either corticocortical connections between the striate cortex and the visual associative structures or of right temporo-parieto-occipital visual analyzers.