Biomedical subjects

D Perani

Publications and source records attributed to D Perani.

At least 73 records · Page 4Linked to original sources

PubMed1993

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.

Aged↗

PubMed1993

[18F]FDG PET in fatal familial insomnia: the functional effects of thalamic lesions.

We used [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) to study regional cerebral glucose utilization (rCMRglc) in four patients with fatal familial insomnia (FFI), a prion disease with a mutation at codon 178 of the prion protein gene. Two patients, presenting only with insomnia and dysautonomia, had a prominent and, in one case, selective thalamic hypometabolism. The remaining two cases presented a more complex clinical picture with multiple neurologic deficits, with both thalamic and widespread brain hypometabolism involving the majority of cortical structures, basal ganglia, and the cerebellum. This widespread pattern was present in the early stage of the disease and showed significant worsening as the disease progressed in one patient examined twice. The thalamic hypometabolism, consistently found with PET in FFI patients, is in agreement with the neuropathologic findings and is a hallmark of the disease.

Adult↗

PubMed1993

Comparability of FDG PET studies in probable Alzheimer's disease.

Results of studies with positron emission tomography (PET) of 18F-2-fluoro-2-deoxy-D-glucose (FDG) in patients with probable Alzheimer's disease (AD) were compared among three European centers with different PET scanners (in-plane resolution ranging between 6.75 mm and 9.2 mm). A ratio of glucose metabolism in the most typically affected regions over the least typically affected regions was calculated to quantitatively analyze the characteristic pattern of AD. Diagnostic accuracy of this composite ratio was high (95.8%) and was superior to that of most ratios derived from single regions. Correspondingly, there was a consistent, highly significant difference between patients (mean ratio 0.77 +/- 0.11) and normals (mean 0.99 +/- 0.04) without significant differences among laboratories. Possible small effects of rate constant variation and region size were analyzed by computer simulation. The results demonstrate that a common investigation protocol may yield FDG PET data in different laboratories that are closely comparable in spite of differences between scanners and imaging equipment.

Aged↗

PubMed1992

Relationship between corpus callosum atrophy and cerebral metabolic asymmetries in multiple sclerosis.

Corpus callosum (CC) atrophy by magnetic resonance imaging (MRI) is a common finding in multiple sclerosis (MS). In order to examine the relationship between CC atrophy and cortical brain metabolism, we compared the cerebral metabolic rates for glucose (CMRglc), measured by positron emission tomography (PET), of 8 MS patients with evidence of CC atrophy on midsagittal MRI, 8 MS patients without CC atrophy and 10 healthy controls. Results showed no significant differences in supratentorial CMRglc absolute values between the three groups, although a slight metabolic reduction was observed in both MS groups compared with normal controls. By contrast, only patients with CC atrophy showed greater directional metabolic asymmetry than normals, the left frontal, temporal and parietal association cortices being significantly lower than the right. Predominant left hemispheric metabolic reductions were not accompanied by a corresponding left-sided predominance in the extent of MRI-detected demyelinating lesions. Therefore our data suggest that CC atrophy interfers more with left than with right metabolic function.

Adult↗

PubMed1992

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 Papez's 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.

Adult↗

PubMed1991

Sneddon syndrome: cerebral perfusion studies by Tc99m HM-PAO and SPECT.

Sneddon syndrome is a non-inflammatory, non-atherosclerotic disease involving small and medium-sized arteries of the brain and of the skin. The arteriographic examination is often negative despite progressive impairment of the neurological status. In 3 patients with Sneddon syndrome cerebral perfusion was assessed with single photon emission computerized tomography (SPECT) and technetium99 m-hexamethylpropylenamineoxime (Tc99 HM PAO). A correlation between clinical and SPECT finding was found, with significant focal reduction of regional cerebral blood flow (rCBF) in the two more severely affected patients.

Adult↗

PubMed1991

Chronic pain: a PET study of the central effects of percutaneous high cervical cordotomy.

We have studied 5 patients with unilateral, severe chronic pain due to cancer before and after percutaneous, ventrolateral cervical cordotomy to investigate the central effects of the procedure. The aim was to identify the functional anatomical correlates of abolishing unilateral nociceptive input to the brain. Patients were investigated by positron emission tomography using C15O2 to evaluate cerebral blood flow. Comparisons were made between the patients with unilateral pain before cordotomy and normal volunteers. These demonstrated significantly less blood flow in 3 out of 4 of the individual quadrants of the hemithalamus contralateral to the side of pain (P less than 0.01-0.05). These differences were abolished by cordotomy. Comparison of the patients before and after cordotomy showed a significant decrease in blood flow in the dorsal anterior quadrant of the thalamus contralateral to the side of pain (P less than 0.05) which was normalised after cordotomy. There were no significant changes in the prefrontal or primary somatosensory cortex. We conclude that chronic pain results in a decrease of synaptic activity at thalamic level either from decreased activity in neurones projecting to that region and/or attenuated local neuronal firing. We have demonstrated no secondary remote effects in cortex, indicating the importance of subcortical mechanisms in central responses to chronic pain.

Aged↗

PubMed1990

The nigrostriatal dopaminergic system assessed in vivo by positron emission tomography in healthy volunteer subjects and patients with Parkinson's disease.

A group of healthy control subjects and patients with Parkinson's disease were investigated using positron emission tomography and two tracers as indicators of different specific properties of the presynaptic dopaminergic system in caudate nucleus and putamen. The first tracer, 6-L-(18F)-fluorodopa, was used as an analog of levodopa to assess its regional brain uptake, conversion into, and retention as dopamine and further metabolites. The second tracer, (11C)-nomifensine was employed as an indicator of striatal monaminergic reuptake sites that are principally dopaminergic. We have used this tracer to assess dopaminergic nerve terminal density. In patients with Parkinson's disease, striatal uptake of both tracers was decreased, putamen being significantly more affected than caudate. Side-to-side differences of uptake in putamen, but not caudate, correlated with corresponding left-right differences of scored clinical motor performance. Both 6-L(18F)-fluorodopa and (11C)-nomifensine tracer uptake in putamen was decreased on average to 40% of normal values, suggesting that a substantial part of the cellular elements of the dopaminergic nigrostriatal system is still intact in living parkinsonian patients. This is in contrast to the generally extreme depletion of endogenous dopamine in the putamen of patients found at postmortem. Our results lend support to the search for drug treatments that protect against further nigrostriatal cell loss and that could be exhibited as soon as the disease manifests clinically. If successful, a sufficient striatal nerve terminal pool would remain so that the effectiveness of levodopa as a dopamine repletor could persist.

Aged↗

PubMed1990

In vivo metabolism and kinetics of 99mTc-HMPAO.

The cerebral distribution of 99mTc-labeled d, l, hexamethyl-propylene-amine-oxime (99mTc-HMPAO) as a function of rCBF and time was examined in rats and in man. The results of this study confirm that 99mTc-HMPAO is distributed in brain in proportion to rCBF. However, the rapid systemic breakdown of the tracer in blood results in considerable difficulties in the assessment of the arterial concentration of the parent compound; incomplete extraction of 99mTc-HMPAO from blood to brain and significant efflux from brain represent further limitations in the use of this tracer for quantification of rCFB. Despite these limitations 99mTc-HMPAO is of potential interest for a qualitative assessment of rCBF in specific clinical conditions.

Animals↗

PubMed1990

Cerebral blood flow, blood volume and oxygen utilization. Normal values and effect of age.

Regional cerebral blood flow (CBF), oxygen extraction ratio (OER), oxygen utilization (CMRO2) and blood volume (CBV) were measured in a group of 34 healthy volunteers (age range 22-82 yrs) using the 15O steady-state inhalation method and positron emission tomography. Between subjects CBF correlated positively with CMRO2, although the interindividual variability of the measured values was large. OER was not dependent on CMRO2, but highly negatively correlated with CBF. CBV correlated positively with CBF. When considering the values of all the regions of interest within a single subject, a strict coupling between CMRO2 and CBF, and between CBF and CBV was found, while OER was constant and independent of CBF and CMRO2. In 'pure' grey and white matter regions CMRO2, CBF and CBV decreased with age approximately 0.50% per year. In other regions the decline was less evident, most likely due to partial volume effects. OER did not change or showed a slight increase with age (maximum in the grey matter region 0.35%/yr). The results suggest diminished neuronal firing or decreased dendritic synaptic density with age.

Adult↗

PubMed1989

Cortical pathophysiology and clinical neurologic abnormalities in acute cerebral ischemia. A serial study with single photon emission computed tomography.

We studied brain cortical radioactive tracer activity in a consecutive series of nine patients with acute hemispheric ischemic stroke at their first cerebral ischemic stroke at their first cerebral ischemic episode. Results from N,N,N'-trimethyl-N'- (2-hydroxy-3-methyl-5-[123-I]-iodobenzyl)-1,3 propanediamine-2HCl (four patients) and technetium Tc 99m hexamethylpropyleneamine oxime (five patients) single photon emission computed tomographic studies were compared with x-ray computed tomography (CT) and clinical findings within the first 48 hours, on day 10, and on day 30 after the clinical ictus. Cortical hypoactivity agreeing with the clinical findings was found on all initial scans but not in the follow-up studies. Cortical activity on the affected side in patients with stroke was significantly lower when compared with cortical activity in sex- and age-matched controls (n = 21). Computed tomography (with contrast) was less sensitive in detecting the ischemic lesions. These studies demonstrate that in the acute phase of stroke there is a single photon emission computed tomographic cortical disturbance that agrees with clinical findings, even when computed tomography scan infarction is limited to subcortical structures.

Adult↗

PubMed1988

Crossed aphasia: functional studies with single photon emission computerized tomography.

The correlation between clinical picture, CT scan and regional cerebral blood flow (rCBF) assessed by single photon emission computerized tomography (SPECT) was investigated in two patients with crossed aphasia. The presence and degree or right hemisphere dysfunction, beyond the areas affected by CT, closely paralleled the time course of language disturbances in both patients: transient aphasia in case 1 was associated with temporary reduction of perfusion in the right hemisphere, while in case 2 persistent aphasia and apraxia were found along with severe right hemisphere hypoperfusion three year after the onset of stroke.

Aged↗

PubMed1988

Remote effects of subcortical cerebrovascular lesions: a SPECT cerebral perfusion study.

The remote effects of small unilateral cerebrovascular lesions confined to subcortical structures were evaluated by single photon emission computerized tomography (SPECT) and a CBF tracer, I-123 HIPDM. A CBF study was performed in 34 patients presenting with subcortical stroke either in the acute or in the chronic stages. Twenty-one of the 34 patients showed areas of cortical hypoperfusion ipsilateral to the subcortical lesion. In 14 patients, asymmetry of perfusion was also observed at the cerebellar level, perfusion being significantly reduced in the cerebellar hemisphere contralateral to the lesion. There was no correlation between the degree and extension of these remote effects and the type of stroke (ischemic or hemorrhagic), the patency of cerebral arteries, or the size and site of the lesion by transmissive computerized tomography (TCT). Subcortical hematomas showed a correlation between occurrence of remote effects and time interval from the onset of stroke, occurring more frequently in the acute phase. A correlation was observed between cortical and cerebellar remote effects and the severity of clinical presentation. The causes of remote effects are still unclear and have been extensively debated. Our data indicate that there is a relationship of remote effect to the neurological status. It is possible to show, by noninvasive, low-cost methods, remote CBF effects after stroke that may contribute to the assessment of brain functional impairment.

Acute Disease↗

PubMed1988

Recovery from aphasia and neglect after subcortical stroke: neuropsychological and cerebral perfusion study.

Cortical regional cerebral perfusion was assessed by N, N, N1-trimethyl-N1-(2)-hydroxy-3-methyl-5-(I-123) iodobenzyl-1, 3-propanediamine 2 HCl I-123 (HIPDM) and single photon emission computerised tomography (SPECT) in six aphasic and two neglect patients with unilateral subcortical vascular lesions. Assessments were carried out both in the acute phase and after a period ranging from 1 to 6 months after stroke onset. In all patients an almost complete spontaneous recovery occurred and was associated with a significant improvement of cortical perfusion. A relationship between severity of aphasia and degree of cortical hypoperfusion was found, in both the acute and the follow up assessments, in the aphasic subgroup.

Adult↗

PubMed1988

Technetium-99m HM-PAO-SPECT study of regional cerebral perfusion in early Alzheimer's disease.

Regional cerebral perfusion was evaluated by single photon emission computed tomography (SPECT) using technetium-99m hexamethylpropyleneamine oxime ([99mTc]HM-PAO) in sixteen patients with Alzheimer's disease (AD) in early clinical phase and in 16 healthy elderly controls. In all patients transmission computed tomography (TCT) and/or magnetic resonance imaging (MRI) did not show focal brain abnormalities. Relative to normal subjects, AD patients showed significant reductions in cortical/cerebellar activity ratio: cortical perfusion was globally depressed with the largest reductions in frontal and posterior temporo-parietal cortices. Asymmetries of relative perfusion between cerebral hemispheres were also demonstrated when language was affected or visuospatial functions were unevenly impaired. In patients with early AD, SPECT provides functional information to be compared with clinical and psychometric data.

Aged↗

PubMed1987

Cerebellar diaschisis in pontine ischemia. A case report with single-photon emission computerized tomography.

Regional cerebral and cerebellar blood flows were studied by N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-[123I]iodobenzyl)-1,3- propanediamine 2 HCl (I-123 HIPDM) and single-photon emission computerized tomography (SPECT) in a patient with an ischemic lesion of the pons. An asymmetry of perfusion of the cerebellar hemispheres, normal on transmission computerized tomography scan, was demonstrated by SPECT studies in the early acute phase and confirmed 15 days after. This finding may be related to the interruption of the corticopontocerebellar pathways.

Aged↗

PubMed1987

Cerebral hemispheric and contralateral cerebellar hypoperfusion during a transient ischemic attack.

We studied a 79-year-old woman within 3 h of the onset of a motor aphasia and a right hemiparesis. Single photon emission computed tomography (SPECT) showed a 24% decrease in the perfusion of the left middle cerebral artery territory and a 16% reduction in the perfusion of the right cerebellum. A mild naming difficulty was the neurological deficit at the end of the SPECT examination, and complete recovery was achieved within 24 h. Repeated SPECT study 10 days later was normal. This is the first report of focal hemispheric and contralateral cerebellar hypoperfusion in transient cerebral ischemia.

Aged↗

PubMed1987

Aphasia and neglect after subcortical stroke. A clinical/cerebral perfusion correlation study.

Sixteen patients with unilateral subcortical haemorrhagic or ischaemic stroke, confirmed by CT, were evaluated for the presence of aphasia and neglect. Compared with patients without neuropsychological deficits, left brain-damaged aphasic and right brain-damaged neglect patients showed a significantly greater reduction of cortical perfusion on N,N,N1-trimethyl-N1-(2)-hydroxy-3-methyl-5-(I-123) iodobenzyl-1,3-propanediamine 2 HCl I-123 (HIPDM) and single photon emission computerized tomography (SPECT). These results suggest that major cortical derangement is the crucial factor for the appearance of aphasia or neglect after a subcortical stroke. These remote effects, which are related to the size of the subcortical lesion, are interpreted in terms of interruption of neural connections (diaschisis).

Adult↗