Brain Perfusion Patterns Research Articles

Anormalidades de fluxo sangüíneo cerebral em indivíduos dependentes de cocaína

INTRODUÇÃO: Nos últimos anos, tem havido relatos de anormalidades do fluxo sanguíneo cerebral em indivíduos com o abuso de cocaína, detectadas por meio de tomografia computadorizada por emissão de fóton único (SPECT). Esse padrão anormal de perfusão cerebral tem sido associado a prejuízos cognitivos mas não a alterações observáveis por meio de exames de neuroimagem estrutural. Um problema envolvendo a maioria dos trabalhos publicados sobre esse tema é a inclusão de um grande número de usuários de heroína nas amostras estudadas. Essa outra droga também parece afetar o padrão de perfusão cerebral, particularmente durante estados de abstinência. MÉTODOS: Quatorze pacientes dependentes de cocaína (nenhum com uso de opióides) e 14 voluntários normais (grupo controle) foram submetidos a exames de SPECT com dímero de etil-cisteína marcado com tecnécio-99m. A análise dos exames de SPECT foi realizada por meio de análise visual qualitativa das imagens obtidas (procedimento padrão na prática clínica), realizada por um radiologista não informado sobre o diagnóstico dos indivíduos avaliados. RESULTADOS: A análise visual revelou um padrão sugestivo de irregularidades do fluxo sangüíneo cerebral em nove pacientes, mas em apenas dois controles (p = 0,018; teste exato de Fisher bicaudal). CONCLUSÕES: Anormalidades de circulação cerebral podem ter relação com prejuízos cognitivos relatados em populações de dependentes de cocaína. Embora déficits de perfusão cerebral associados ao uso de cocaína possam ser irreversíveis, têm surgido relatos na literatura de tratamentos para essas anormalidades de fluxo sangüíneo. Alterações de fluxo sangüíneo cerebral associadas à dependência de cocaína ocorrem mesmo na ausência de abuso ou dependência de opióides.

SPECT and Localized Proton MRS of Epilepsy in Children with Cortical Dysplasia

Purpose: Recently cortical dysplasia (CD) attracted attention because of its importance as a focus for epilepsy and a lesion for surgery. However, the clinical features of children with epilepsy with CD vary in the severity of their symptoms, depending on the type or extent of the CD. We performed single photon emission computed tomography (SPECT) and proton magnetic resonance spectroscopy (MRS) in children with epilepsy with CD to investigate the relation between their clinical and neuroimaging features. Methods: Ten children with epilepsy with distinct CD revealed by previous CT or MRI were studied. The ages examined were from 5 days to 13 years. The types of CD were lissencephaly in one case, diffuse pachygyria in two, schizencephaly in one (extensive CD), focal pachygyria in two, polymicrogyria in two, hemimegalencephaly in one, and nodular heterotopia in one (focal CD). Interictal SPECT using99Tc‐ECD was performed in all cases, and ictal SPECT in two cases. Proton MRS was performed in eight cases on a superconductive magnet with a main magnetic field of 1.5 Tesla (Magneton‐Siemens Co., Erlangen, Germany). In each case, the regions of interest (2×2×2 cm) were visually selected in the dysplastic cortex, and the contralateral normal or mildly dysplastic cortex. Results: The four cases with extensive CD showed severe mental and motor retardation. All of their epileptic seizures began within a year of life and were atypical and intractable tonic spasms with focal signs. On the other hand, the six cases with focal CD showed mild psychomotor handicaps. They had mainly localization‐related epilepsies originating from the region of CD, which tended to be relatively late in onset and have a good prognosis. On the brain perfusion (rCBF) obtained with SPECT, the area with CD exhibited plump and sausage‐like images in many cases. The rCBF in the dysplastic cortex varied in each case: hyperperfusion in four cases, hypoperfusion in three, and normoperfusion in three. In a case with hemimegalencephaly, the perfusion pattern showed dynamic changes during the course: diffuse hypoperfusion at 5 days of life, marked hyperperfusion in the dysplastic hemisphere at 15 days, and almost bilaterally symmetrical perfusion at 2 months. In our cases, the SPECT findings were not always related to the intensity of clinical symptoms or the EEG paroxysms. Many MRS findings, even for those cases with extensive CD, showed almost normal patterns for the three peaks (choline, creatine, and NAA). As to the ratio of NAA to choline in the CD cortex, only two cases showed significantly low values (<1.0), and the other two cases exhibited relatively lower values in the CD cortex compared with those in the contralateral cortex. Abnormal peaks, such as for free lipids, were not observed in all cases. There was no relation between the MRS findings and the rCBF with SPECT. Conclusions: In children with epilepsy due to CD, the severity of clinical symptoms, both psychomotor handicaps and epilepsy, is closely related to the extent of the CD. However, their SPECT findings suggest that their pattern of brain perfusion does not directly reflect their clinical features. Interestingly, the proton MRS findings for almost every patient with CD were the normal pattern. This result means that the cerebral lesions of CD have some neuronal activities. Much work needs to be done to establish the relation between the clinical and proton MRS features of children without epilepsy with CD.

Cerebral and cerebellar activation in correlation to the action-induced dystonia in writer's cramp.

The pattern of brain perfusion of four patients with writer's cramp and four control subjects were examined using positron emission tomography scans after [(15)O] butanol injections. Each subject was scanned 12 times to cover three repetitions of four different motor tasks with the right hand. Drawing of horizontal lines and variable durations of the writing of a prelearned text were performed in a pseudorandom order, the latter task commencing either simultaneously with or 30 sec or 120 sec before the tracer injection. The perceived difficulty and signs of dystonia progressed in correlation to the duration of writing. Statistical parametric maps were calculated to test hypotheses of regional specific effects dependent on the performed motor tasks. The patients with writer's cramp had progressively increased activity in the left primary sensorimotor and premotor cortices, the left thalamus, and the cerebellum with a right-side predominance in correlation to the duration of writing. The regions with activity increases thus corresponded to a cerebrocerebellar motor circuit. The duration of writing correlated to a progressive reduction of activity in the patients' left supramarginal and angular gyri (Brodmann areas 40 and 39) and an inferior part of the left temporal lobe (area 20). The control subjects had neither a significant increase or decrease of activity in correlation to the duration of writing. Group-specific differences were confirmed statistically in split-plot interaction analyses.

Subcortical type cognitive impairment in herpes zoster encephalitis.

Nine immunocompetent patients with acute herpes zoster encephalitis (HZE) were studied with the help of neurological investigations. All patients were treated with acyclovir. Neuropsychological performance was compared with that of a group of 16 healthy controls. Computed tomography of the head showed infarct-like hypodense lesions in two patients, involving the internal capsule in one case and the temporoparietal cortex and white matter in another. Hypoperfusion shown by single photon emission computed tomography, mostly involving the frontal areas bilaterally, was seen in six of the seven patients examined. Hyperperfusion as seen in herpes simplex encephalitis was not encountered. One patient remained mildly demented, but all the other patients recovered relatively well. Neuropsychological examination after acyclovir treatment showed a decline in memory and speed of cognitive processes, without circumscribed neuropsychological deficits. Six of the nine patients showed behavioural disinhibition, and mood changes were also observed. Memory impairment in HZE was not as global or as severe as is described after encephalitis due to herpes simplex virus. In HZE both the brain perfusion pattern and the neuropsychological test profile showed features compatible with subcortical dysfunction.

Temporal lobe dysfunction and correlation of regional cerebral blood flow abnormalities with psychopathology in schizophrenia and major depression — A study with single photon emission computed tomography

Studies of regional cerebral bood flow in both schizophrenic and depressed patients have yielded contradictory findings. Single photon emission computed tomography (SPECT) was used to compare brain-perfusion patterns in 17 patients with schizophrenia and 12 patients with major depression and to evaluate the relationship of the findings to psychopathology. The images were analyzed both visually and quantitatively. Twelve of the 17 schizophrenic patients and 8 of the 12 depresse patients showed a pathological blood flow pattern. Hypoperfusion of the left temporal lobe was observed in seven of the schizophrenic and five of the depressed patients. Five of the schizophrenic patients also had a hypoperfusion of the left frontal lobe. Separation of both diagnostic cohorts in two subgroups with pathological and normal cerebral blood flow patterns revealed significantly higher levels of symptomatology in the group with hypoperfusion in the SPECT image. The analysis of different cerebral regions revealed statistically significant correlations in schizophrenic patients between left frontal hypoperfusion and negative symptoms. In contrast, left temporal hypoperfusion was significantly related to positive symptoms in schizophrenia. Our data suggest that left-sided temporal lobe dysfunction is related both to schizophrenia and major depression. The localization of hypoperfusion seems to be associated with the type of psychopathology (positive vs. negative symptoms in schizophrenia). Thus, the results support the model of paralimbic and prefrontal dysfunction in both diseases.

Simple visual analysis of brain perfusion on HMPAO SPECT predicts early outcome in acute stroke.

Single-photon emission computed tomography (SPECT) is used in patients with acute stroke but as yet is of controversial value. We investigated an association of brain perfusion changes in stroke patients with stroke severity, volume of brain damage, and recovery. Consecutive patients with hemispheric stroke were studied prospectively with serial neurological examinations using the Canadian Neurological Scale (CNS), CT. and 99mTc-hexamethylpropyleneamine oxime (HMPAO) SPECT. Visual SPECT patterns of brain perfusion (normal, high, mixed, low, and absent) were correlated with the severity of stroke, lesion volume, and short-term outcome. SPECT studies were performed in a total of 458 consecutive acute stroke patients within 2 weeks after the onset (mean time, 5 days; range, 1 to 12 days). SPECT perfusion patterns correlated with stroke severity (CNS score) during the first 2 weeks (P < .001). Focal absence of brain perfusion on SPECT was associated with the largest volume of brain damage: 104 +/- 84 mL (P < .0001). SPECT perfusion patterns predicted the shortterm outcome: 97% of patients with normal and increased HMPAO uptake made good recovery, 52% of those with decreased perfusion had moderate stroke, and 62% of patients with absent patterns fared badly. In a multiple logistic regression model, admission CNS scores had the strongest predictive value (P = .0001). SPECT had its own prognostic value independent of clinical judgment (P = .03). SPECT statistically improved predictive power of the CNS score (+1% receiver operating characteristic curve area, [X2]2 = 20, P < .001) because of distinction between focal decrease or absence of brain perfusion in patients studied within the first 72 hours of stroke. Visual brain perfusion patterns correlate with the extent, severity, and short-term outcome of hemispheric stroke. HMPAO SPECT may improve the prognostic value of clinical examination if performed during the first 72 hours of stroke.

Sleep Apnea Syndrome and Cerebral Hemodynamics

The dynamics of cerebral blood flow velocity (CBFV) during sleep were investigated in the right middle cerebral artery of 10 patients with sleep apnea syndrome (SAS) (mean age, 37 years) and 10 healthy control subjects (mean age, 32 years) throughout the entire sleep period. A computer-assisted pulsed (2 MHz) transcranial Doppler ultrasonography system was modified for continuous long-term and on-line recording of cerebral hemodynamics. Concurrently, simultaneous polysomnography, continuous BP recordings, and measurement of the end-expiratory carbon dioxide were undertaken. CBFV showed comparable nocturnal profiles in both groups with decreases during non-rapid eye movement (NREM) sleep and increases during rapid eye movement (REM) sleep, indicating that the general pattern of brain perfusion during normal sleep is maintained in SAS. Sleep stage changes were not regularly accompanied by corresponding changes in CBFV. This reflected a quantitative uncoupling between cerebral electrical activity and cerebral perfusion during sleep and indicated a dissociation in the activity of central regulatory mechanisms. Sleep stage-related analysis showed slightly reduced CBFV in patients with SAS compared with healthy control subjects during wakefulness and the first NREM sleep period, suggesting depressed brain activity in the patient group. The higher CBFV values observed in patients with SAS compared with control subjects during REM sleep and sleep stage 2, both preceding and following REM sleep, underline the influence of dynamically changing sleep patterns on cerebral perfusion in these patients. Reproducible rapid decreases in CBFV were related to EEG arousals. Since apneas are terminated by arousals, these results showed that direct neuronal influences on brain perfusion during apnea are evident.

A brain single photon-emission computed tomography (SPECT) study of generalized social phobia

Social phobia is an anxiety disorder whose neurobiology has been little studied (Tancer et al 1995). In contrast to the rich literature on regional cerebral blood flow and/or glucose metabolism in other anxiety disorders such as panic (Reiman et al 1989; Nordahl et al 1990) and obsessive-compulsive disorder (OCD) (Baxter et al 1988; Nordahl et al 1989; Machlin et al 1991; Rubin et al 1992; Adams et al 1993; McGuire et al 1994; Rauch et al 1994), to the best of our knowledge, there have been no such studies to date in social phobia. To investigate brain regions that might be involved in the pathophysiology of social phobia, we examined brain perfusion patterns in a group of these patients and psychiatrically healthy controls using technetium-99m-hexamethyl-proplyenamine oxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT). We included only patients who met diagnostic criteria for the generalized subtype of social phobia (Mannuzza et al 1995), to limit syndromal heterogeneity. Studies in OCD using HMPAO-SPECT have found increased regional cerebral blood flow in medial-frontal cortex (Machlin et al 1991), reduced neostriatal blood flow (Rubin et ai 1992), and/or assymetric basal ganglia perfusion (Adams et al 1993). Given the high comorbidity between social phobia and other anxiety disorders such as OCD, we elected to a priori focus our analyses

Tc-99m HMPAO SPECT Analysis of Neuroleptic Effects on Regional Brain Function

This report describes a new approach to the evaluation of neuroleptic effects on regional brain function. Using Tc-99m HMPAO SPECT imaging, consecutive brain perfusion studies before and after acute haloperidol administration were performed on three schizophrenic patients and two normal volunteers. The antipsychotic drug ameliorated the hypoactivity in the frontal lobe and suppressed the hyperactivity in the temporo-occipito-parietal lobe selectively in the dominant hemisphere in the schizophrenic patients. It did not exert a significant influence on the brain perfusion pattern in normal volunteers. This nuclear medicine technique seems to be useful for the evaluation of drug effects in psychiatric diseases.

SPECT Evaluation of Brain Perfusion Reserve by the Acetazolamide Test Using Tc-99m HMPAO

This report describes a new approach to the evaluation of brain perfusion reserve using Tc-99m HMPAO SPECT. Consecutive brain Tc-99m HMPAO SPECT studies before and after acetazolamide (Diamox) administration were performed within 30 minutes on 19 patients with significant vascular occlusive lesions. Thirteen patients showed decreased perfusion reserve and four patients maintained perfusion reserve in the affected vascular territories after Diamox administration, providing additional information to baseline Tc-99m HMPAO SPECT in 17 (89%) patients. Although flow augmentation post-Diamox was underestimated, possibly due to the nonproportionality of Tc-99m HMPAO activity to true blood flow, significant changes in the brain perfusion pattern were both visually and quantitatively determined using an image subtraction technique. This consecutive Tc-99m HMPAO SPECT technique seems to be of practical use for the evaluation of brain perfusion reserve and for the improvement of the sensitivity of detecting pathologic areas.

Patterns of Brain Perfusion

A representation of cerebral perfusion is obtained using cranial computed tomography following the rapid bolus injection of iodinated intravenous contrast medium. This technique permits the definition of four gross patterns of perfusion (normal, circulatory arrest, hypoperfusion, and hyperperfusion). This classification is affirmed in an experimental model of cerebral infarction in the baboon. The limitations of dynamic imaging using computed tomography are reviewed.