Regional cerebral blood flow in childhood autism: a SPECT study

Regional Cerebral Glucose Metabolism and its Association with Phenotype and Cognitive Functioning in Patients with Autism

INTRODUCTION

In spite of three decades of neuroimaging, we are unable to find consistent and coherent anatomical or pathophysiological basis for autism as changes are subtle and there are no studies from India.

AIM

To study the regional cerebral glucose metabolism in children with autism using positron emission tomography (PET) scan and to study the behavior and cognitive functioning among them.

MATERIALS AND METHODS

Ten subjects (8-19 years) meeting Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for autism were evaluated on Childhood Autism Rating Scale (CARS), trail making test (TMT) A and B, Wisconsin card sorting test, Raven's progressive matrices, and PET scan. A control group of 15 matched subjects without any brain pathology or neurological disorder was similarly studied.

RESULTS

Four out of the ten patients with autism had abnormal PET scan findings, and in contrast, none of the patients in the control group had abnormal PET scan. Of the four patients with abnormality in the PET scan, two patients had findings suggestive of hypometabolism in cerebellum bilaterally; one patient showed bilateral hypometabolism in anterior temporal cortices and cerebellum, and the fourth patient had hypermetabolism in the bilateral frontal cortices and medial occipital cortices. Subjects with autism performed poorly on neuropsychological testing. Patients with abnormal PET scan findings had significantly higher scores on the "body use" domain of CARS indicating more stereotypy.

CONCLUSION

Findings of this study support the view of altered brain functioning in subjects with autism.

A systematic review of molecular imaging (PET and SPECT) in autism spectrum disorder: current state and future research opportunities

Non-invasive positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are techniques used to quantify molecular interactions, biological processes and protein concentration and distribution. In the central nervous system, these molecular imaging techniques can provide critical insights into neurotransmitter receptors and their occupancy by neurotransmitters or drugs. In recent years, there has been an increase in the number of studies that have investigated neurotransmitters in autism spectrum disorder (ASD), while earlier studies mostly focused on cerebral blood flow and glucose metabolism. The underlying and contributing mechanisms of ASD are largely undetermined and ASD diagnosis relies on the behavioral phenotype. Discovery of biochemical endophenotypes would represent a milestone in autism research that could potentially lead to ASD subtype stratification and the development of novel therapeutic drugs. This review characterizes the prior use of molecular imaging by PET and SPECT in ASD, addresses methodological challenges and highlights areas of future opportunity for contributions from molecular imaging to understand ASD pathophysiology.

Hyperbaric oxygen treatment in autism spectrum disorders

Traditionally, hyperbaric oxygen treatment (HBOT) is indicated in several clinical disorders include decompression sickness, healing of problem wounds and arterial gas embolism. However, some investigators have used HBOT to treat individuals with autism spectrum disorders (ASD). A number of individuals with ASD possess certain physiological abnormalities that HBOT might ameliorate, including cerebral hypoperfusion, inflammation, mitochondrial dysfunction and oxidative stress. Studies of children with ASD have found positive changes in physiology and/or behavior from HBOT. For example, several studies have reported that HBOT improved cerebral perfusion, decreased markers of inflammation and did not worsen oxidative stress markers in children with ASD. Most studies of HBOT in children with ASD examined changes in behaviors and reported improvements in several behavioral domains although many of these studies were not controlled. Although the two trials employing a control group reported conflicting results, a recent systematic review noted several important distinctions between these trials. In the reviewed studies, HBOT had minimal adverse effects and was well tolerated. Studies which used a higher frequency of HBOT sessions (e.g., 10 sessions per week as opposed to 5 sessions per week) generally reported more significant improvements. Many of the studies had limitations which may have contributed to inconsistent findings across studies, including the use of many different standardized and non-standardized instruments, making it difficult to directly compare the results of studies or to know if there are specific areas of behavior in which HBOT is most effective. The variability in results between studies could also have been due to certain subgroups of children with ASD responding differently to HBOT. Most of the reviewed studies relied on changes in behavioral measurements, which may lag behind physiological changes. Additional studies enrolling children with ASD who have certain physiological abnormalities (such as inflammation, cerebral hypoperfusion, and mitochondrial dysfunction) and which measure changes in these physiological parameters would be helpful in further defining the effects of HBOT in ASD.

Brief Report: alterations in cerebral blood flow as assessed by PET/CT in adults with autism spectrum disorder with normal IQ

Specific biological markers for autism spectrum disorder (ASD) have not yet been established. Functional studies have shown abnormalities in the anatomo-functional connectivity of the limbic-striatal "social" brain. This study aimed to investigate regional cerebral blood flow (rCBF) at rest. Thirteen patients with ASD of normal intelligence and ten IQ-, sex- and age-matched healthy controls (HC) underwent PET/CT using [1-(11)C]butanol, a perfusion tracer. As compared to HC, ASD showed significant CBF increases in the right parahippocampal, posterior cingulate, primary visual and temporal cortex, putamen, caudatus, substantia nigra and cerebellum. No statistically significant correlation between CBF and IQ was found. The limbic, posterior associative and cerebellar cortices showed increased blood flow in ASD, confirming previous findings about the neurobiology of ASD.

Feature selection and classification of imbalanced datasets: application to PET images of children with autistic spectrum disorders

Learning with discriminative methods is generally based on minimizing the misclassification of training samples, which may be unsuitable for imbalanced datasets where the recognition might be biased in favor of the most numerous class. This problem can be addressed with a generative approach, which typically requires more parameters to be determined leading to reduced performances in high dimension. In such situations, dimension reduction becomes a crucial issue. We propose a feature selection/classification algorithm based on generative methods in order to predict the clinical status of a highly imbalanced dataset made of PET scans of forty-five low-functioning children with autism spectrum disorders (ASD) and thirteen non-ASD low functioning children. ASDs are typically characterized by impaired social interaction, narrow interests, and repetitive behaviors, with a high variability in expression and severity. The numerous findings revealed by brain imaging studies suggest that ASD is associated with a complex and distributed pattern of abnormalities that makes the identification of a shared and common neuroimaging profile a difficult task. In this context, our goal is to identify the rest functional brain imaging abnormalities pattern associated with ASD and to validate its efficiency in individual classification. The proposed feature selection algorithm detected a characteristic pattern in the ASD group that included a hypoperfusion in the right Superior Temporal Sulcus (STS) and a hyperperfusion in the contralateral postcentral area. Our algorithm allowed for a significantly accurate (88%), sensitive (91%) and specific (77%) prediction of clinical category. For this imbalanced dataset, with only 13 control scans, the proposed generative algorithm outperformed other state-of-the-art discriminant methods. The high predictive power of the characteristic pattern, which has been automatically identified on whole brains without any priors, confirms previous findings concerning the role of STS in ASD. This work offers exciting possibilities for early autism detection and/or the evaluation of treatment response in individual patients.

Neurobehavioral profile and brain imaging study of the 22q13.3 deletion syndrome in childhood

OBJECTIVE

The 22q13.3 deletion syndrome (Online Mendelian Inheritance in Man No. 606232) is a neurodevelopmental disorder that includes hypotonia, severely impaired development of speech and language, autistic-like behavior, and minor dysmorphic features. Although the number of reported cases is increasing, the 22q13.3 deletion remains underdiagnosed because of failure in recognizing the clinical phenotype and detecting the 22qter deletion by routine chromosome analyses. Our goal is to contribute to the description of the neurobehavioral phenotype and brain abnormalities of this microdeletional syndrome.

METHODS

We assessed neuromotor, sensory, language, communication, and social development and performed cerebral MRI and study of regional cerebral blood flow measured by positron emission tomography in 8 children carrying the 22q13.3 deletion.

RESULTS

Despite variability in expression and severity, the children shared a common developmental profile characterized by hypotonia, sleep disorders, and poor response to their environment in early infancy; expressive language deficit contrasting with emergence of social reciprocity from ages approximately 3 to 5 years; sensory processing dysfunction; and neuromotor disorders. Brain MRI findings were normal or showed a thin or morphologically atypical corpus callosum. Positron emission tomography study detected a localized dysfunction of the left temporal polar lobe and amygdala hypoperfusion.

CONCLUSIONS

The developmental course of the 22q13.3 deletion syndrome belongs to pervasive developmental disorders but is distinct from autism. An improved description of the natural history of this syndrome should help in recognizing this largely underdiagnosed condition.

Technetium-99m HMPAO brain SPECT in autistic children and their families

The purpose of the study was to investigate perfusion patterns in autistic children (AC) and their families. Ten AC (9 boys, 1 girl; mean age: 6.9+/-1.7 years) with autistic disorder defined by DSM-III-R criteria, five age-matched children (3 boys, 2 girls) as a control group, and the immediate family members of eight AC (8 mothers, 8 fathers, 7 siblings; mean ages: 39+/-4 years, 36+/-5 years and 13+/-5 years, respectively) were included in the study. Age- and sex-matched control groups for both the parents and the siblings were also included in the study. Brain perfusion images were obtained 1 h after the intravenous injection of an adjusted dose of Tc-99m HMPAO to children and the adults. Visual and semiquantitative evaluations were performed. Hypoperfusion was seen in the right posterior parietal cortex in three AC, in bilateral parietal cortex in one AC, bilateral frontal cortex in two AC, left parietal and temporal cortex in one AC, and right parietal and temporal cortex in one AC. Asymmetric perfusion was observed in the caudate nucleus in four AC. In semiquantitative analyses, statistically significant hypoperfusion was found in the right inferior and superior frontal, left superior frontal, right parietal, right mesial temporal and right caudate nucleus. In parents of AC, significant hypoperfusion was noted in the right parietal and bilateral inferior frontal cortex. In siblings of AC, perfusion in the right frontal cortex, right nucleus caudate and left parietal cortex was significantly decreased. This preliminary study suggests the existence of regional brain perfusion alterations in frontal, temporal, and parietal cortex and in caudate nucleus in AC and in their first-degree family members.

Regional cerebral blood flow in childhood autism: a SPET study with SPM evaluation

AIM

To establish a link between rCBF assessed with Tc-ECD SPET and the clinical manifestation of the disease.

METHODS

We performed the study on 11 patients (five girls and six boys; mean age 11.2 years) displaying autistic behaviour and we compared their data with that of an age-matched reference group of eight normal children. A quantitative analysis of rCBF was performed calculating a perfusion index (PI) and an asymmetry index (AI) in each lobe. Images were analysed with statistical parametric mapping software, following the spatial normalization of SPET images for a standard brain.

RESULTS

A statistically significant (P=0.003) global reduction of CBF was found in the group of autistic children (PI=1.07+/-0.07) when compared with the reference group (PI=1.25+/-0.12). Moreover, a significant difference was also observed for the right-to-left asymmetry of hemispheric perfusion between the control group and autistic patients (P=0.0085) with a right prevalence greater in autistic (2.90+/-1.68) with respect to normal children (1.12+/-0.49). Our data show a significant decrease of global cerebral perfusion in autistic children in comparison with their normal counterparts and the existence of left-hemispheric dysfunction, especially in the temporo-parietal areas devoted to language and the comprehension of music and sounds.

CONCLUSION

We suggest that these abnormal areas are related to the cognitive impairment observed in autistic children, such as language deficits, impairment of cognitive development and object representation, and abnormal perception and responses to sensory stimuli. Tc-ECD SPET seems to be sensitive in revealing brain blood flow alterations and left-to-right asymmetries, when neuroradiological patterns are normal.

[Autism: neuroimaging]

Autism is a neurodevelopmental disorder with a range of clinical presentations. These presentations vary from mild to severe and are referred to as autism spectrum disorders. The most common clinical sign of autism spectrum disorders is social interaction impairment, which is associated with verbal and non-verbal communication deficits and stereotyped and repetitive behaviors. Thanks to recent brain imaging studies, scientists are getting a better idea of the neural circuits involved in autism spectrum disorders. Indeed, functional brain imaging, such as positron emission tomography, single foton emission tomography and functional MRI have opened a new perspective to study normal and pathological brain functioning. Three independent studies have found anatomical and rest functional temporal lobe abnormalities in autistic patients. These alterations are localized in the superior temporal sulcus bilaterally, an area which is critical for perception of key social stimuli. In addition, functional studies have shown hypoactivation of most areas implicated in social perception (face and voice perception) and social cognition (theory of mind). These data suggest an abnormal functioning of the social brain network in autism. The understanding of the functional alterations of this important mechanism may drive the elaboration of new and more adequate social re-educative strategies for autistic patients.

Autism severity and temporal lobe functional abnormalities

Two independent studies have described bilateral temporal hypoperfusion in autistic children. Temporal regions are implicated in social perception, language, and "theory-of-mind," abilities that are impaired in autism. We investigated a putative relationship between cerebral blood flow (rCBF) measured at rest and clinical profile of 45 autistic children (Autism Diagnostic Interview-Revised [ADI-R] scores). A whole-brain covariance analysis was performed. Significant negative correlation was observed between rCBF and ADI-R score in the left superior temporal gyrus. The more severe the autistic syndrome, the more rCBF is low in this region, suggesting that left superior temporal hypoperfusion is related to autistic behavior severity.

Findings of brain 99mTc-ECD SPECT in high-functioning autism-3-dimensional stereotactic ROI template analysis of brain SPECT-

The aim of this study is confirmation of an abnormal regional cerebral blood flow (rCBF) pattern in high-functioning autism (HFA). Confirmation of an abnormal rCBF pattern in HFA may be useful for elucidate of its pathophysiology and a differential diagnosis, such as with attention-deficit/hyperactivity disorder (AD/HD). Brain 99mTc-ECD SPECT was performed in 16 cases of HFA. The HFA group consisted of 16 cases of HFA. They were all male, with an IQ of 76-126. They had normal brain MRI findings, and had an age of 9-14 years. We examined abnormal rCBF in HFA by comparing the results to those in the control group. The control group consisted of 1 male and 4 females cryptogenic epilepsy patients with normal intelligence. They have no problems in learning at school or mental or behavioral traits. They had normal brain MRI or SPECT findings, and had an age of 7-15 years. 3-dimensional stereotactic ROI template (3DSRT) was used to analyze SPECT data. We calculated the 'relative rCBF (%)' (RI count of each segment x 100/Sum of RI count of the corresponding hemisphere), and compared the values between the two groups. We found a significantly low 'relative rCBF (%)' in the left temporal region in the HFA group. We also calculated the 'L/R ratio' (the 'relative rCBF (%)' of a segment on the left side / the 'relative rCBF (%)' of the corresponding segment on the right side), and compared the value for each segment between the two groups. There were no significant differences in any segments between the two groups. We also checked for differences in the 'relative rCBF (%)' between segments on the right side and corresponding segments on the left side in both the HFA and control groups. We found significant right < left perfusion in the angular region and significant left < right perfusion in the pericallosal, thalamus, and hippocampus region in the HFA group. We also found significant right < left perfusion in the temporal region in the control group. Significant hypoperfusion in the left temporal region due to an unidentified underlying brain pathology and abnormal laterality in the angular, temporal (lack of right < left perfusion), pericallosal, thalamus, and hippocampus regions may influence the symptoms of autism.

Alterações anátomo-funcionais do sistema nervoso central no transtorno autístico: um estudo com RNM e SPECT

Apresentamos um estudo das alterações anátomo-funcionais do sistema nervoso central (SNC) de pacientes com transtorno autístico (TA), através da ressonância nuclear magnética (RNM) e da tomografia computadorizada por emissão de fóton único (SPECT). Foram estudados 24 pacientes, sendo 15 (62,5%) do sexo masculino e 9 (17,5%) do feminino, com idade média de 9 anos. Todos os pacientes foram submetidos à RNM e apenas em 19 foi realizado o SPECT. Dos pacientes que realizaram RNM, 75% apresentaram alterações anatômicas e dos que realizaram o SPECT todos apresentaram alterações funcionais. As alterações anatômicas estavam preferencialmente localizadas no corpo caloso (25%), septo pelúcido (15,63%), ventrículos cerebrais (12,55%), cerebelo (9,38%), lobo temporal (6,25%), lobo occipital (6,25%) e hipocampo (6,25%). As alterações funcionais predominaram no lobo frontal (53,13%), lobo temporal (28,13%) , lobo parietal (15,63%) e nos núcleos da base (3,13%). A presença de alterações anátomo-funcionais do SNC não são prioritárias para o diagnóstico, o qual deve ter sempre uma validação clínica.

The relationship between 99mTc-HMPAO brain SPECT and the scores of real life rating scale in autistic children

Childhood autism is a developmental disability of unknown origin with probable multiple etiologies. The purpose of this study was to compare the changes of regional cerebral blood flow (rCBF) in autistic and non-autistic controls, and to determine the relationship between rCBF on 99mTc-hexamethylpropylene amine oxime (HMPAO) brain SPECT and the scores of the Ritvo-Freeman Real Life Rating Scale (RLRS), IQ levels, and age of autistic children. Eighteen autistic children (four girls, 14 boys; mean age: 6.13 +/- 1.99 years) and 11 non-autistic controls (five girls, six boys, mean age: 6.5 +/- 3.39 years) were examined using 99mTc-HMPAO brain SPECT. All the children satisfying DSM-IV criteria for autistic disorder were taken into evaluation, and scored by the Ritvo-Freeman RLRS. IQ levels of these children were determined by Goodenough IQ test. Six cortical regions of interest (ROIs; frontal (F), parietal (P), frontotemporal (FT), temporal (T), temporo-occipital (TO), and occipital (O)) were obtained on transaxial slices for count data acquisition. The ratio of average counts in each ROI to whole-slice counts for the autistic children was correlated with the scores of Ritvo-Freeman RLRS. Hypoperfusion in rCBF in autistic children compared with the control group were identified in bilateral F, FT, T, and TO regions. We found no relationship between rCBF on 99mTc-HMPAO brain SPECT and the scores of the Ritvo-Freeman RLRS. There was a relationship between bilateral F regions perfusion on 99mTc-HMPAO brain SPECT and the age of autistic children. There was also a negative correlation between IQ levels and the scores of sensory responses, social relationship to people, and sensory-motor responses. Our results suggest that 99mTc-HMPAO brain SPECT is helpful to locate the perfusion abnormalities but no correlation is found between rCBF on 99mTc-HMPAO brain SPECT and the scores of Ritvo-Freeman RLRS.

Brain imaging in neurobehavioral disorders

Neuroimaging studies of neurobehavioral disorders are using new imaging modalities. In dyslexia, anatomic imaging studies demonstrate an abnormal symmetry of the planum temporale. Functional imaging supports the hypothesis that developmental dyslexia is frequently the result of deficits in phonologic processing and that normal reading requires a patent network organization of a number of anterior and posterior brain areas. In autism, anatomic imaging studies are conflicting. Functional imaging demonstrates temporal lobe abnormalities and abnormal interaction between frontal and parietal brain areas. In attention-deficit-hyperactivity disorder, imaging studies suggest an abnormality in the prefrontal and striatal regions. Neuroimaging studies are often contradictory, but trends, especially with functional imaging analysis, are evolving. Because neurobehavioral disorders seem to be a result of a dysfunction in brain circuits, no one region will be abnormal in all patients studied. Further studies with well-defined patient populations and appropriate activation paradigms will better elucidate the pathophysiology of these conditions.

Single-photon emission computed tomography of the brain in autism: effect of the developmental level

Brain single-photon emission computed tomography was performed in 22 autistic and 10 nonautistic disabled patients. The regional cerebral blood flow in both laterotemporal and dorso-medio-lateral frontal areas decreased significantly in the autistic group compared with in nonautistic group. In the autistic group, the regional cerebral blood flow was significantly higher in the right temporal and right parietal lobes than that in the left ones. Inversely, the regional cerebral blood flow in the frontal and occipital lobes was significantly higher on the left side than on the right side. In the nonautistic group, except for in the dorso-medio-lateral frontal lobes (left > right), there was no difference in the regional cerebral blood flow in either cerebrum or cerebellum. A positive correlationship between regional cerebral flow and development quotient (intelligence quotient) was observed in the left laterotemporal and both dorso-medio-lateral frontal areas, and a negative one was observed in the cerebellar vermis area. These results suggest that the regional cerebral blood flow decrease in the temporal and frontal areas relates to not only the brain mechanism of autism reported previously but also intelligence levels.

Functional neuroimaging of autistic disorders

Functional neuroimaging methods hold promise for elucidating the neurobiology of autistic disorders, yet they present difficult practical and scientific challenges when applied to these complex and heterogeneous syndromes. Single-state studies of brain metabolism and blood flow thus far have failed to yield consistent findings, but suggest considerable variability in regional patterns of cerebral synaptic activity. Patients with idiopathic autism are less likely to show abnormalities than are patients with comorbid illness or epilepsy. Activation studies have begun to suggest alterations in brain organization for language and cognition. Neurotransmitter studies using positron emission tomography (PET) suggest abnormalities of serotonergic and dopaminergic function. Studies using magnetic resonance spectroscopy (MRS) have begun to document metabolic deficits in the frontal cortex and cerebellum. A single study using magnetoencephalography suggests a high incidence of epileptiform activity in children with autistic regression. Research needs include well-controlled developmental studies, particularly of young subjects and relatively homogeneous subgroups, which balance scientific rigor with ethical constraints. Investigations of the serotonergic and dopaminergic systems, limbic-based memory and emotional systems, and the role of epileptiform activity in autism represent priorities for future research.

Brain mapping of language and auditory perception in high-functioning autistic adults: a PET study

We examined the brain organization for language and auditory functions in five high-functioning autistic and five normal adults, using [15O]-water positron emission tomography (PET). Cerebral blood flow was studied for rest, listening to tones, and listening to, repeating, and generating sentences. The autism group (compared to the control group) showed (a) reversed hemispheric dominance during verbal auditory stimulation; (b) a trend towards reduced activation of auditory cortex during acoustic stimulation; and (c) reduced cerebellar activation during nonverbal auditory perception and possibly expressive language. These results are compatible with findings of cerebellar anomalies and may suggest a tendency towards atypical dominance for language in autism.

Functional brain imaging in neuropsychiatric disorders of childhood

This review article presents a summary of the current state-of-the-art of functional brain imaging, with a primary focus on childhood neuropsychiatric disorders. Coverage is emphasized for developments that appear to be of current or potential future importance for the child neurologist and related pediatric specialist, and also from the perspective of the developmental neuroscientist. Emphasis is placed on the modalities of single photon emission computed tomography (SPECT), positron emission tomography (PET), and both "conventional" and "functional" magnetic resonance imaging, (MRI) including reference to the major new radiopharmaceutical and magnetic resonance-based imaging agents and techniques. The fundamental physicochemical processes underlying such studies are outlined, with citation of sources of more detailed information for the interested reader. A variety of imaging studies are reviewed for selected groups of childhood neuropsychiatric disorders, designed to illustrate the achievements and future promise of these imaging modalities. Areas of concentration are suggested for future imaging research in the field of childhood behavioral disorders, where these methods seem critical to improved understanding of pathogenetic mechanisms, as well as development of more effective treatment strategies.

Proton magnetic resonance spectroscopy of the brain in three cases of Rett syndrome: comparison with autism and normal controls

Rett syndrome (RS) is a clinically defined disorder characterized by autistic behavior, and cognitive and motor skill loss early in life. We performed 1H-MRS of the brain in 3 cases of RS in comparison with in autism and controls. The older patient with RS demonstrated decreased N-acetylaspartate (NAA)/choline (Cho) and NAA/creatine (Cr) ratios when compared with the autism and control groups, whereas the younger patients did not demonstrate these decreased metabolite ratios. The Cho/Cr ratio did not differ among Rett syndrome, autism and controls. Since the clinical stage did not differ among the 3 cases of RS, it was suggested that NAA was decreased with increasing age and was not related with the clinical stage of RS. The NAA/Cho, NAA/Cr and Cho/Cr ratios did not differ between autism and controls. The present data suggest that there may be a secondary degenerative process of late onset in RS, which pathophysiologically differs from autism.

Laboratory and diagnostic testing in child and adolescent psychiatry: a review of the past 10 years

OBJECTIVE

To review in a critical fashion the literature of the past decade covering diagnostic and laboratory testing in the field of child and adolescent psychiatry.

METHOD

A computerized search of articles published during the past decade was made, and selected articles are presented. Because of the paucity of articles specifically relating to minors, selected articles from adult psychiatry are cited.

RESULTS

With a few notable exceptions, few controlled studies on the specificity and sensitivity of any laboratory test for any specific disorder of behavior presenting in children have been conducted in children and adolescents. A high index of suspicion will remain the clinician's best ally in utilizing laboratory measures in the assessment of psychopathology. Nonetheless, studies have appeared that will guide the clinician as to what tests are not clinically useful.

CONCLUSION

Indications and the lack of indications for specific laboratory studies are an integral part of the knowledge base that child psychiatrists must have. Much more empirical data will need to be collected prospectively to inform the field and to move the judicious use of the laboratory from an art to a science.

Differences in brain metabolites between patients with autism and mental retardation as detected by in vivo localized proton magnetic resonance spectroscopy

We performed volume-selective proton magnetic resonance spectroscopy (1H-MRS) of the brain with a 1.5 T magnet in 28 patients with autism, and compared the results with those from 28 age-matched patients with unclassified mental retardation and 25 age-matched healthy children. Peaks for N-acetylaspartate, choline and creatine, but not lactate, were observed in each group on 1H-MRS. The N-acetylaspartate/choline ratio was lower in patients with mental retardation than in patients with autism and controls (P = .05, respectively). However, there were no differences in the N-acetylaspartate/ choline ratios between patients with autism and controls, and the N-acetylaspartate/creatine and choline/creatine ratios did not differ among the three groups. These results suggest that N-acetylaspartate is decreased in patients with mental retardation and that a disorder or dysfunction of neurons in the brain exists. There also appear to be differences in the brain lesions or dysfunctions found in patients with autism and mental retardation.

Brain perfusion SPECT and EEG findings in Rett syndrome

Thirteen patients (mean age 8.4 + 5.3 years) with Rett syndrome (RS) were studied with EEG and 99mTc-HMPAO SPECT. Eleven patients had background abnormalities and 10 patients paroxysmal activity in EEG. Hypoperfusion of varying severity was detected in 11 patients, 7 patients having multiple lesions. Bifrontal hypoperfusion, observed in 6 patients, was the most distinctive finding. Hypoperfusion was observed also in other cortical regions, except for the occipital lobes. There was no correlation between severity of the background abnormality or presence of paroxysmal activity in EEG and grade of hypoperfusion. There was, however, an association between the severity of hypoperfusion and early manifestation of symptoms in patients with RS. Whether this early-onset group of patients represents a different disease entity or only reflects disease variability the basic pathology being the same, is a possibility that deserves further clarification.

Infantile spasms: III. Prognostic implications of bitemporal hypometabolism on positron emission tomography

Positron emission tomography (PET) of brain glucose utilization is highly sensitive in detecting focal cortical abnormalities in patients with infantile spasms even when the computed tomographic (CT) and magnetic resonance imaging (MRI) scans are normal. Of 110 infants with spasms evaluated for potential surgical intervention during an 8-year period, we encountered 18 infants (7 males, 11 females; age range, 10 mo to 5 yr) with a common metabolic pattern on positron emission tomography (PET) consisting of bilateral hypometabolism in the temporal lobes. CT and MRI scans did not reveal any focal abnormalities in the 18 infants. Video-electroencephalographic monitoring indicated either bilateral or multifocal epileptogenicity, or failed to show any epileptic focus, so that none of the 18 infants were considered candidates for resective surgery. These patients were then enrolled in a prospective study aimed at determining long-term outcome in the presence of bilateral temporal PET hypometabolism. Analysis of outcome in 14 of the 18 subjects (follow-up period, 10 mo to 10 yr 5 mo; mean, 3 yr 11 mo +/- 2 yr 4 mo [SD]) revealed the following: (1) all had severe developmental delay and had failed to gain significant milestones; (2) language development had been minimal or absent; (3) 10 of the 14 met the DSM-IV criteria for autistic disorder. Our findings indicate that patients with infantile spasms and bitemporal glucose hypometabolism on PET comprise a relatively homogeneous group and are typically not candidates for cortical resection. The long-term outcome of these infants is particularly poor and the majority are autistic.

Psychophysiological aspects of autistic disorders: overview

The neurological, neurochemical, and neurotransmitter level differences as well as genetic influences associated with autism have been studied extensively in the last two decades. The varied findings from research offer hope for better understanding, effective treatment, and, perhaps, cure of this pervasive developmental disorder.

Neuroimaging in child and adolescent neuropsychiatric disorders

OBJECTIVE

To review the major findings and pathophysiological implications of imaging studies of neuropsychiatric disorders that onset in childhood or adolescence.

METHOD

More than 200 neuroimaging studies were selected for review from Medline searches if the studies concerned developmental neuropsychiatric disorders such as autism, fragile X syndrome, Down syndrome, schizophrenia, obsessive-compulsive disorder, Tourette's syndrome, attention-deficit hyperactivity disorder, and dyslexia.

RESULTS

Disordered central nervous system development may produce evidence of cortical neuronal migration abnormalities in autism, smaller cortical structures in Down syndrome, frontal lobe deficits and larger basal ganglia in schizophrenia, hypoplastic basal ganglia in Tourette's syndrome, aberrancies of the planum temporale in dyslexia, and hypoplastic cerebellar structures in numerous developmental disorders. Normal cerebral asymmetries appear to be disrupted in a number of disorders, including schizophrenia, Tourette's syndrome, attention deficit disorder, and dyslexia.

CONCLUSIONS

Neuroimaging data regarding pathological central nervous system development in childhood are still sparse, and many of the findings in developmental disorders of childhood onset concern the study of adult subjects with those disorders. Nevertheless, imaging modalities previously used only in adults are with increasing frequency being applied to the study of children, which will likely continue to contribute to the understanding of pathological brain structure and function throughout childhood and to the improved treatment of these disorders.

SPECT of the brain in childhood autism: evidence for a lack of normal hemispheric asymmetry

Autism is thought to be associated with abnormal hemispheric specialization and left-hemispheric dysfunction. Brain functional imaging using 133Xe-SPECT (single photon emission computed tomography) was used to measure left/right asymmetry and absolute values of regional cerebral blood flow (rCBF) in 18 children with autism aged from four to 17 years and 10 age-matched controls. All controls but only 10 children with autism were right-handed. The left-to-right indices, both hemispheric and regional, were positive in controls, indicating higher left than right rCBF values, but were negative in patients with autism. This inversion was statically significant for total hemispheres, sensorimotor and language-related cortex and was explained by a significant decrease of the left absolute rCBF values in these regions in the patients with autism. The inversion was independent of handedness, sex and age. These results confirm the existence of left-hemispheric dysfunction in childhood autism, especially in the cortical areas devoted to language and handedness, leading to anomalous hemispheric specialization.

Association study with two markers of a human homeogene in infantile autism

Epidemiological data and family studies in autism show that there is a genetic susceptibility factor in the aetiology of this syndrome. We carried out an association study in infantile autism. Two markers of the homeogene EN2 involved in cerebellar development were tested in a population of 100 autistic children and in a population of 100 control children. With the MP4 probe showing a PvuII polymorphism, significant differences in the allele frequencies between the two populations were found (chi 2 = 7.99, df = 1, p < 0.01). With the MP5 probe showing an SstI polymorphism, no difference appeared (chi 2 = 1.17, not significant). Several clinical examinations allowed us to characterise the autistic children. Most of them had high scores for autistic behaviour and language disorders but low scores for neurological syndromes. Two children had a significant family history and six children had confirmed syndromes or diseases of genetic origin. Discriminant analysis between clinical and molecular data did not give significant results. These preliminary results must be supported by further analyses of this gene and by studies of its potential involvement in the pathophysiology of the autistic syndrome.

Childhood autism: An appeal for an integrative and psychobiological approach

The difficulty that a person with autism has in establishing relationships, maintaining them (communicating and responding appropriately) is a common experience of those close to them., That impaired perceptual and cognitive processing can underlie this difficulty and the interactions of people with autism with the material environment has been established in the laboratory. The consequences at a psychological level of analysis may converge in the inadequacy of second-order representations of the world. An attenuation of such endogenous monitoring processes could also indirectly account for features of withdrawal and the stereotypies often observed. At another level of analysis there are delays in neurotransmission, in the CNS and a lack of flexibility of physiological response shown by evoked potential recordings. Tomographic studies of blood flow and metabolism illustrate a lack of correlation between information processing centres in the brain that may sometimes arise from diffuse gray matter atrophy. A "stop-go" form of modulation of central processing is mediated by anomalous ascending serotonergic and dopaminergic function (transmitters with inhibitory and switching functions). On these bases it is no wonder that representations are not formed and inappropriate and repetitive behaviors follow, although the link remains somewhat speculative. Both levels of analysis are useful for an explanation. As behavioral and pharmacotherapy, though helpful, are severely limited in their efficacy, more effort is required to synthesize the different levels of analysis into a psycho-biological approach, to remedial programs and new forms of therapy.

Regional cerebral blood flow estimation by neural network-based parametric regression analysis

An artificial neural network (ANN) model was proposed for real-time estimation of regional cerebral blood flow (rCBF), by given head and expired air curves obtained through 133Xe inhalation. The network was constructed according to a regression model described by a linear differential equation. Experimental results compare well with those obtained by conventional curve fitting strategies, but the parameter estimation process is much simplified. A systematic procedure in developing ANN for parametric regression analysis was introduced; networks are constructed according to the selected regression model so that the obtained weights of a trained network directly represent parameters of the regression model which best fits the observed data set. Such a design-oriented methodology extends the classification-based applications of ANN to parametric regression analysis, and therefore may have more generalized applications besides rCBF estimation.

Brain single-photon emission computed tomography for behavior disorders in children

Single-photon emission computed tomography (SPECT) of the brain has been used to define functional abnormalities in two groups of childhood behavior disorders: (1) a "primary" category in which there is exclusive or predominant presentation with cognitive and/or behavioral dysfunction and (2) encephalopathies, often defined etiologically at the biochemical or molecular level, in which clinical expression includes, but is not confined to, neural dysfunction. Radiopharmaceuticals available for such studies are manifold, but those used to date have been predominantly perfusion agents, eg, Xenon-133 (133Xe) and technetium-99m (99mTc) hexamethylpropylene amine oxime, and studies with [99mTc]bicisate are eagerly awaited. Xenon-133 studies require that the patient be in the field of view of the detector while the tracer is administered. This renders it difficult for a subject to perform cognitive and other exercises while being imaged, because the environment is quite foreign. On the other hand, the 99mTc-labeled perfusion agents permit a scintigraphic "snapshot" of regional cerebral blood flow during a behavioral event without having to have the patient under the imaging instrument. Thus, one can separate the administration of the radiotracer, which can be done under more controlled and physiological conditions, from the actual imaging. In addition, greater spatial resolution is achieved with the technetium-based agents. Currently, multidetector or dedicated annular crystal-type cameras are the preferred brain SPECT devices, and they are essential to applications such as cortical "activation mapping" or tomographic detection of receptor systems. Close attention to technical detail and standardization of the child's behavioral environment during the investigation are critical to a successful study. The relative advantages and disadvantages of qualitative versus semiquantitative analysis of imaging date are reviewed. Among primary behavioral disorders, 133Xe SPECT studies in attention deficit disorder-hyperactivity (ADHD) have suggested a pattern of hypoperfusion of striatal and periventricular structures with sensorimotor cortical hyperperfusion. This pattern is consistent with some neurophysiological models of the disorder. In cerebral palsy, perfusional abnormalities have paralleled clinical deficits and may offer information to help predict outcome. The important field of childhood affective disorders (schizophrenia, juvenile autism, depression, etc) remains largely unstudied with SPECT. Finally, representative examples of the use of SPECT to study perfusion in encephalopathies with behavioral expression (phenylketonuria, MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) syndrome, Wilson's disease, etc) are given.

SPECT (Single Photon Emission Computed Tomography) in 31 children and adolescents with autism and autistic-like conditions

SPECT with Tc-99m-HM-PAO was used in examining 31 patients with autism and autistic-like conditions. Sixteen of these had autistic disorder/autistic-like conditions with associated epilepsy. The autistic disorder group without epilepsy was relatively high functioning. All 31 patients showed reduction of regional cerebral blood flow in the temporal lobes. There was no clear difference between the groups with and without epilepsy, suggesting that seizure disorder per se could not account for the findings.

Blood flow response to auditory stimulations in normal, mentally retarded, and autistic children: a preliminary transcranial Doppler ultrasonographic study of the middle cerebral arteries

Using the noninvasive transcranial ultrasonic Doppler method, flow dynamics of the middle cerebral arteries were investigated in relation to auditory stimulations in 12 children with autistic behavior compared with 12 normal controls and 10 mentally retarded children. In normal children, auditory stimulation evoked lateralized modifications: blood flow increased and resistance index decreased on the left side; such modifications were not recorded on the right side. This pattern should indicate vasodilatation mechanisms induced by changes in the metabolism of the brain areas supplied by the left middle cerebral arteries (MCA). Although less asymmetrical, this pattern was also found in the mentally retarded children. Autistic children significantly differed from these two groups. They displayed a symmetric pattern of responses with a blood flow decrease and resistance-index increase on both sides; this could suggest abnormal metabolic mechanisms induced by auditory stimulation in autistic children and could be related to the previous hypothesis of impairment in the development of cerebral lateralization in autism. These preliminary results show that transcranial Doppler ultrasonography may be a valuable and practicable tool for the noninvasive study of evoked blood flow responses in psychopathology.