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Biomedical subjects

P A Rizzo

Publications and source records attributed to P A Rizzo.

At least 19 recordsLinked to original sources
PubMed1992

Changes in central and peripheral nervous system function during hypoglycemia in man: an electro-physiological quantification.

We measured somatosensory evoked potentials (SEP) in normal subjects during acute (group A) and moderately prolonged (group B) hypoglycemia. We considered the following parameters: peripheral conduction velocity (wrist-Erb CV), conduction time (CT) between brachial plexus and the cervical cord (Erb-N13) and central CT from the cervical cord/lower brainstem lemniscal pathway to the cortex (N13-N20). In group A, the electrophysiological parameters did not change significantly throughout the study. In group B, mean N13-N20 CT increased from a basal values of 5.82 +/- 0.11 to 6.22 +/- 0.11 msec at 105 min (p less than 0.02) and 6.33 +/- 0.11 msec at 120 min (p less than 0.05). This study indicates that neither acute nor moderately prolonged hypoglycemia influence the peripheral nerve function in normal subjects and provides evidence that hypoglycemia as low as 2.4 mmol/L, lasting more than 60 min, can significantly increase the conduction time of central somatosensory pathways.

Adult↗
PubMed1992

Low contrast stimuli enhance PERG sensitivity to the visual dysfunction in Parkinson's disease.

The pattern electroretinogram (PERG) was recorded at different contrast levels (96%, 71%, 47%) in 10 Parkinson's disease patients before and during dopaminergic monotherapy. The data were compared to a control group of 8 normal subjects recorded with the same procedure. PERG P50 latency progressively increased as contrast was decreased both in normal subjects and patients; however, this trend was much more pronounced in PD patients without therapy; consequently in this group the difference between P50 latency obtained with 96% and 47% contrast was statistically significant (P = 0.01, analysis of variance corrected by post-hoc Tukey test). By contrast this was not seen in the control group. Statistical analysis (Bonferroni's t test) showed at the 47% contrast level a significant P50 latency increase (P less than 0.01) in PD patients without therapy if compared with the control group. Dopaminergic monotherapy induced a P50 latency recovery in PD patients. We conclude that low contrast stimuli enhance PERG sensitivity to the visual dysfunction of PD patients. Moreover, the effects observed after therapy confirm that abnormal contrast response functions in PD patients are linked to dopaminergic deficiency.

Aged↗
PubMed1992

Angiographically occult brainstem vascular malformation: a longitudinal comparison of magnetic resonance imaging (MRI) and multimodal evoked potential (EP) recordings.

Over a period of several years, a patient with angiographically occult vascular malformation (AOVM) involving the brainstem was longitudinally studied by means of serial Magnetic Resonance Imaging (MRI) and multimodal Evoked Potential (EP) recordings (visual-VEP, brainstem auditory-BAEP, somatosensory--SEP--by stimulating median and peroneal nerves). MRI did contribute to an accurate definition of AOVM features. In particular, it was able to follow over time the AOVM size, and to discriminate between recent and old bleedings. Multimodal EP recordings displayed different pathological BAEP and peroneal SEP values, which documented a transient segmental brainstem involvement (related to the presence of hemorrhage), along with persistent and probably irreversible signs of diffuse brainstem dysfunction. Thus, MRI and EP assessment is useful in monitoring the clinical course of brainstem occult vascular malformations.

Brain Neoplasms↗
PubMed1991

Transcranial Doppler sonography in familial hemiplegic migraine.

A patient affected by familial hemiplegic migraine underwent Transcranial Doppler Sonography twice: the first during a spontaneous attack with right hemiparesis and aphasia, the second during a headache-free period. During the attack the following haemodynamic changes were seen: (a) bilateral increase in the middle cerebral artery and anterior cerebral artery blood flow velocities (this increase was more pronounced on the left side), (b) decreased systo-diastolic ratio and pulsatility index on the right side, (c) increased systo-diastolic ratio and pulsatility index on the left side. Our results indicate that during the attack in this familial hemiplegic migraine patient a diffuse vasoconstriction of the basal cerebral arteries developed. Moreover, Transcranial Doppler Sonography data suggest that a prolonged vasoconstriction of the peripheral arterioles could play a role in determining the neurological symptoms in this syndrome.

Adult↗
PubMed1991

Blood leukotrienes in headache: correlation with platelet activity.

Platelet hyperactivity, one of the commonest findings associated with migraine, has been related to increased release of biologically active substances such as catecholamines and arachidonic acid metabolites, which seem to play a role in the pathogenesis of migraine. In this study, in vitro platelet aggregation tests were performed on samples from patients with different types of headache. The presence of platelet hyperactivity was clearly demonstrated in 11 patients with classical migraine between attacks, but not in 4 patients between attacks of common migraine. Nevertheless, the presence of a marked platelet hyporesponsivity was found during the attack phase of both classical and common migraine. No difference in platelet aggregability was found between attack and post-attack phases in 5 patients with cluster headache. Blood leukotrienes were analyzed in 8 patients with classical migraine and in the 5 patients with cluster headache. During the attack phase of classical migraine both LTC4 and LTB4 were present in the peripheral blood, while the post-attack phase was characterized by the disappearance of LTC4 and the presence of LTB4 and its transisomer delta 6-trans-LTB4. Blood leukotrienes were constantly absent during both phases of cluster headache. Incubation of normal platelets with LTC4 or delta 6-trans-LTB4 was followed by inhibition of platelet response to epinephrine. delta 6-trans-LTB4, at higher concentrations, induced the opposite effect. A possible role of blood leukotrienes in the changes occurring in platelet aggregability during the different phases of classical migraine, is discussed.

Adult↗
PubMed1991

Abnormalities of cognitive functions in IDDM revealed by P300 event-related potential analysis. Comparison with short-latency evoked potentials and psychometric tests.

The possible influence of diabetes on the higher mnestic and cognitive functions has been investigated. The P300 wave latency, an endogenous electrophysiological event, was explored and compared with the multimodal short-latency evoked potential (EP) recordings (visual [VEP], brainstem auditory [BAEP], and median and tibial nerve somatosensory EPs [mSEP and tSEP, respectively]) and psychometric test measures in 16 insulin-dependent diabetic (IDDM) patients, in 16 age- and (IDDM) sex-matched nondiabetic subjects, and in a large normal reference population. The age of subjects, the duration of IDDM, and the metabolic control of patients were taken into account. P300 values were significantly increased in IDDM versus matched control subjects (P less than 0.001), and 3 patients showed values above the reference value range. Abnormal VEP recordings were present in 1 of 16 patients, BAEP in 3 of 16, mSEP in 7 of 16, and tSEP in 6 of 16. Digit-span backward test results were significantly (P less than 0.02) modified in the diabetic cohort. There was no tendency for anomalies of P300, short-latency EPs, and psychometric test values to be contemporarily present, except in 1 patient. Electrophysiological or psychometric abnormalities were not clearly correlated with the duration of IDDM or the degree of short-term metabolic control. These findings give evidence that 1) higher cognitive functions may be affected in diabetes as documented by P300 analysis and short-term memory tests, 2) endogenous electrophysiological analysis highlights neuropsychological changes not detectable by psychometric tests, 3) an alteration of evoked potentials was present in half of the IDDM subjects studied, and 4) anomalies of the CNS are patchily distributed in diabetes.

Acoustic Stimulation↗
PubMed1991

Simultaneous recording of pattern electroretinogram (PERG) and visual evoked potential (VEP) in multiple sclerosis.

We studied 18 multiple sclerosis (MS) patients affected by retrobulbar neuritis (RBN). The patients were subdivided into two groups. Group 1: 14 patients with RBN. Group 2: 4 patients with optic atrophy. An ophthalmological examination (visual acuity, fundus oculi, visual field) was carried out in all the patients. A simultaneous visual evoked potential (VEP) and pattern electroretinogram (PERG) recording at two spatial frequencies (45' and 15') was performed. All the data obtained in Group 1 were compared (Student T-Test) with those of a control group of normal subjects matched for age and sex. Group 1. VEP: a comparison of the data in MS patients affected by RBN with the control group revealed a statistically significant P100 latency delay with both spatial frequencies (P less than 0.001). PERG: no "b" wave latency change at 45' and 15' spatial frequencies were seen. A "b" wave amplitude reduction was observed; this reduction reached significant values at 45' (P less than 0.001). Group 2. In optic atrophies the PERG was absent in 4 eyes at 45' and in 5 eyes at 15'.

Adult↗
PubMed1989

Multimodal evoked potentials in neuro-Behçet: a longitudinal study of two cases.

Two neuro-Behçet patients have been studied, over a period of several months, by means of peroneal and median somatosensory- (SEP), brainstem auditory- (BAEP), and visual- (VEP) evoked potentials. In both patients, peroneal SEP showed evidence of a pathological reduction in the central conduction velocity without a related deep sensation impairment, while VEP changes were consistent with the visual disorders. Conversely, BAEP and median SEP findings did not show disease-related abnormalities. The observed anomalies were detectable irrespective of the clinical phase of the disease. Thus, evoked potential assessment is useful in providing objective evidence for evaluating and monitoring CNS damage in neuro-Behçet's syndrome.

Adult↗
PubMed1989

A longitudinal study of multimodal evoked potentials in diabetes mellitus.

Abnormal findings in visual (VEP), brainstem auditory (BAEP) and somatosensory (SEP) evoked potentials at early stages of Type 1 and Type 2 diabetes have recently been reported by our group. Our aim here was to perform a longitudinal study in diabetic patients at an early stage of the disease using a combined evoked potential analysis in order to evaluate the variation of neurological abnormalities over time. Nine Type 1 and 12 Type 2 diabetic patients were examined and a second recording was carried out after a mean interval of 15.7 months +/- 6.2 SD. VEP, BAEP and SEP were measured in all patients. At the first recording electrophysiological abnormalities, present in both Type 1 and Type 2 diabetes were more evident when a multimodal evaluation was used (44.4% and 66.7% respectively). The follow-up study showed that overall neurological abnormalities persisted in all those patients who had previously presented pathological values. Whereas the number of patients with pathological values remained unmodified, a tendency to progression, namely the number of nervous levels with electrophysiological abnormalities, was observed. Thus, our study confirms the appearance of anatomofunctional disorders in the central nervous system in short-term diabetes, shows the persistence of neurological impairment in such patients and reveals a progressive segmental involvement at different nervous levels.

Acoustic Stimulation↗
PubMed1988

Early detection of neurological involvement in IDDM and NIDDM. Multimodal evoked potentials versus metabolic control.

Clarification of the extent and mechanisms of damage to the central nervous system in diabetes is a frontier of current neurological research. Our aim was to obtain ample electrophysiological documentation of possible neurological abnormalities in both insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetic patients with a short duration of disease and without overt complications, taking into account metabolic control. Group 1 comprised 11 IDDM patients, and group 2 included 14 NIDDM patients treated with diet alone; the duration of disease was less than 4 yr, and no concomitant clinical complications were present. Age- and sex-matched normal subjects formed groups 3 and 4. Pattern visual evoked potentials (VEP), brain stem auditory evoked potentials (BAEP), and somatosensory evoked potentials (SEP; after the stimulation of both median and tibial nerves) were recorded in all subjects, and metabolic control was evaluated in terms of glycemia and glycosylated hemoglobin. In group 1, significant abnormalities were found in the latency values of VEP, median SEP, and tibial SEP compared with control subjects. Similar latency abnormalities were shown in group 2 for VEP, median SEP, and tibial SEP values and for wave I latency of BAEP. Glycosylated hemoglobin values were correlated with BAEP and SEP abnormalities in many patients in both groups. Furthermore, in group 2, glycemic values correlated with SEP abnormalities. We therefore conclude that neurophysiological abnormalities are present at different levels in IDDM and NIDDM patients only a few years after clinical diagnosis and before the appearance of overt complications, and these abnormalities seem to be correlated with metabolic control status.

Adult↗
PubMed1987

Prognostic value of early somatosensory evoked potentials during carotid surgery: relationship with electroencephalogram, stump pressure and clinical outcome.

The authors have reported on the prognostic value of continuous monitoring of somatosensory evoked potentials (SEP) in a survey of 25 patients who underwent carotid surgery. SEP recordings were correlated with the EEG, stump pressure (SP) values and clinical outcome. A non-cephalic reference was used for SEP recordings to allow the analysis of both subcortical and cortical components. During surgery the conduction time between SEP peaks relating to the subcortical components remained stable or showed minimum variations in all patients. During carotid clamping, SEP variations were observed in 9 out of 25 cases (36%). The application of an intraluminal shunt was accompanied by the return to normal values in 7 out of 9 patients. In the remaining two cases SEP abnormalities continued post-operatively and were accompanied by new neurological deficits. EEG changes during carotid clamping were associated with SEP modifications in 6 out of 7 cases, although they were not always correlated. Results confirm that SEP recordings provide useful data concerning the function of the CNS in anaesthetized patients and that, being sensitive to CBF changes, SEP monitoring acts as an indicator of cerebral ischaemia.

Adult↗
PubMed1987

A multiparametric index of platelet in vitro aggregation in cerebrovascular disease.

148 patients with various forms of cerebrovascular disease (CVD) were studied by means of a multiparametric analysis of in vitro platelet aggregation, based on the following six parameters: ADP and epinephrine primary and secondary aggregation thresholds and percent maximum aggregation induced by optimal concentrations of ADP and epinephrine. These patients were assigned to four study groups, according to clinical diagnosis supported by CT scan, of transient ischemic attack and reversible neurological deficit (TIA-RIND), or completed stroke, in the presence or absence respectively of antiplatelet medical treatment at the time of the study. A statistically significant increase of the in vitro platelet aggregation was found in 44.4% of the untreated TIA-RIND patients and in 33.9% of the untreated stroke patients. However this last group showed a higher percentage of very marked hyperaggregation. Differences between the two treated study groups and controls were not significant. No difference was found in collagen- and ristocetin-induced aggregation between the patient groups and the controls.

Adult↗
PubMed1987

Subacute necrotizing encephalomyelopathy (Leigh's disease): clinical correlations with computerized tomography in the diagnosis of the juvenile and adult forms.

A computerized tomography (CT) scan was performed on 6 surviving patients with a suspected diagnosis of subacute necrotizing encephalomyelopathy of the juvenile and adult forms. Bilateral low density areas were observed in the putamina in all cases. This CT pattern conformed with the characteristic pathological changes of the disease. Once the possibility of Wilson's disease or an earlier episode of acute cerebral hypoxia, syndromes which both display a similar appearance in CT, is excluded, a diagnosis of subacute necrotizing encephalomyelopathy may be considered in cases showing bilateral low density areas in the basal ganglia, especially in the putamina, and with a consistent clinical history.

Adolescent↗
PubMed1987

Event-related potentials as a tool in the evaluation of cognitive functions in young subjects through the execution of a simple task.

Event-related potentials (ERPs) were recorded in 20 student volunteers. Three recordings were performed using aural stimuli of 4,000 (rare tones) and 250 Hz. In the target recording subjects were asked to count the rare tones. Endogenous and exogenous components of ERP recordings were analyzed. During the target recording N2 and P3 components were observed at 200 ms and approximately 300 ms, respectively, in addition to N1 (100 ms) and P2 (180 ms). The N2 and P3 waves are indicative of analysis at a higher cognitive level and have been termed the 'response set'. The P3 wave appeared to be stable in all subjects and may represent a useful electrophysiological method to explore mnemonic and cognitive functions in man.

Adolescent↗
PubMed1986

Parkinson disease: electrophysiological (CNV) analysis related to pharmacological treatment.

The contingent negative variation (CNV) was studied in a group of patients with Parkinson's disease. Testing was carried out 3 times: after a pharmacological wash-out period and at 15 and 30 days after the start of treatment with L-DOPA and bromocriptine. Peak and area CNV increased significantly after each treatment. The post-imperative negative variation (PINV) was observed in 6 out of 10 patients. The correlation found between electrophysiological functioning (CNV) measures and pharmacological treatment supports the view that dopaminergic brain activity mediates the generation of the slow negative event-related brain potentials.

Bromocriptine↗