Metabolic recovery in caudate nucleus of children following cerebral hemispherectomy

Review : Metabolic Imaging: A Window on Brain Development and Plasticity

Various biochemical and physiological processes that undergo maturational changes during human brain development can be now studied in vivo using PET. The distribution of local cerebral glucose utilization shows regional alterations in the first year of life in agreement with behavioral, neurophysiological, and anatomical changes known to occur during development of the infant. Measurement of the absolute rates of glucose utilization with PET reveals that during the major portion of the first decade, the human brain has a higher energy (glucose) demand compared with both the newborn and adult brains. With adolescence, glucose utilization rates decline to reach adult values by age 16-18 years. This nonlinear course of cerebral glucose 'metabolic' maturation is also seen in a number of animal models and coincides with the develop mental course of transient synaptic exuberance associated with enhanced brain plasticity and efficient learn ing. Evidence of brain reorganization detected with PET is discussed in children with unilateral brain injury and early sensory deprivation. NEUROSCIENTIST 5:29-40, 1999

Molecular imaging in neuroscience research with small-animal PET in rodents

Cognitive neuroscience, which studies the biological basis of mental processes, widely uses neuroimaging technologies like functional magnetic resonance imaging and positron emission tomography (PET) to study the human brain. Small laboratory animals, like rodents, are commonly used in brain research and provide abundant models of human brain diseases. The development of high-resolution small-animal PET and various radiotracers together with sophisticated methods for analyzing functional brain imaging data have accelerated research on brain function and neurotransmitter release during behavioral tasks in rodents. In this review, we first summarize advances in the methodology of cognitive research brought about by the development of sophisticated methods for whole-brain imaging analysis and improvements in neuroimaging protocols. Then, we discuss basic mechanisms related to metabolic changes and the expression of neurotransmitters in various brain areas during task-induced neural activity. In particular, we discuss glucose metabolism imaging and brain receptor imaging for various receptor systems. Finally, we discuss the current status and future perspectives. Mechanisms of neurotransmitter expression will probably become an increasingly important field of study in the future, leading to more collaboration between investigators in fields such as computational and theoretical neuroscience.

PET in the Assessment of Pediatric Brain Development and Developmental Disorders

This article discusses and reviews the role and contribution of PET in understanding the structural and functional changes that occur during brain development, and how these changes relate to behavioral and cognitive development in the infant and child. Data regarding various aspects of brain development, such as glucose metabolism, protein synthesis, and maturation and development of neurotransmitter systems will help in understanding the pathogenesis and neurologic basis of various developmental and neurologic disorders. This may help in following disease evolution and progression, planning and development of various therapeutic interventions, timing these interventions and monitoring their responses, and rendering long-term prognostication.

An animal model of central auditory pathway imaging in the rat brain by high resolution small animal positron emission tomography

CONCLUSIONS

Our study demonstrated that high resolution animal positron emission tomography (PET) can non-invasively assess the change in glucose metabolism of the central auditory pathway including the inferior colliculus and auditory cortex in the rat.

OBJECTIVES

The traditional in vitro approach with immunohistochemical staining or autoradiography to assess chronological changes or topographic arrangement of central auditory pathway required sacrificing a large number of animals. Inter-individual difference is also a major concern. Therefore, development of an in vivo animal model using PET imaging would be a rational method to overcome these shortcomings.

MATERIALS AND METHODS

Small animal PET scan using (18)F-fluorodeoxyglucose (FDG) as a functional marker was performed in rats. Each animal was serially scanned before and after unilateral cochlear ablation, with and without acoustic stimulation. The images were analyzed by the region of interest (ROI) method. Ratios of radioactivity at the inferior colliculus and auditory cortex and a referenced cerebral cortex between bilateral hemispheres were measured.

RESULTS

These scans demonstrated several brain structures including the inferior colliculus (IC) and cortex (B). Moreover, unilateral cochlear ablation decreased the radioactivity at contralateral IC and auditory cortex (C) areas. Differences may reach 33% in IC and 27% in C, and average radioactivity ratios were 1.24+/-0.08 and 1.18+/-0.07 in selected adjacent sections, respectively.

Positron emission tomography for neurologists

This short review focuses on practical, present day, clinical application of FDG PET, a technology available to practicing neurologists for managing their patients. Indications in the disease states of dementia, neuro-oncology, epilepsy, parkinsonism, and other less common settings are reviewed. Many third-party payers currently make reimbursements based on these indications. By measuring an aspect of brain function, PET provides information that often is unobtainable from other sources, thus facilitating more rationale and cost-effective management, which can only benefit the patient, the referring physician, and the health care system as a whole.

Increased striatal serotonin synthesis following cortical resection in children with intractable epilepsy

BACKGROUND AND PURPOSE

Serotonin is a major regulator of structural brain plasticity, which may occur following cortical resection in humans. In this study we used positron emission tomography (PET) with alpha[11C]methyl-l-tryptophan (AMT) to evaluate serotonergic alterations in subcortical structures following cortical resection in children with intractable epilepsy.

METHODS

AMT uptake in the thalamus and lentiform nucleus was evaluated postoperatively (1-89 months following resection) in 19 children (mean age: 8.7 years) with a previous cortical resection due to intractable epilepsy. Ten children with partial epilepsy but without resection and seven normal children served as controls.

RESULTS

There was an increased AMT uptake in the lentiform nucleus ipsilateral to the resection as compared to the contralateral side (mean asymmetry: 4.2+/-3.0%), and the asymmetries were significantly higher than those measured in the control groups (p<or=0.001). Post-resection asymmetry indices in the lentiform nucleus correlated inversely with postoperative time (r=-0.67; p=0.002), but not with age (p=0.29) or the extent of resection (p=0.77). In contrast, thalamic AMT uptake asymmetries were not different among the three groups (p=0.63).

CONCLUSIONS

Cortical resection results in a sustained increase of AMT uptake in the lentiform nucleus, suggesting increased serotonin synthesis. Serotonergic activation in the deafferented striatum may play a role in the functional reorganization of cortico-striatal projections in humans.

Visual functions without the occipital lobe or after cerebral hemispherectomy in infancy

This paper investigates whether and to what extent vision with awareness is still possible in the whole visual field after loss of the occipital lobe of one or both cerebral hemispheres or after hemispherectomy in childhood. The visual functions of four children who suffered from unilateral or bilateral loss of the occipital lobe or who had been hemispherectomized were examined. The results show that even after unilateral loss of the striate and prestriate cortex the extent of the visual field may still be in the normal range. The residual visual functions may be mediated by intact extrastriate areas such as V5 and LO of the damaged cerebral hemisphere. It is also shown that even after complete hemispherectomy in early life the visual field may have a normal extent and that conscious visual perception in the whole visual field may be preserved. In hemispherectomized children, the remaining cerebral hemisphere or neural structures in the midbrain, including the superior colliculi and the praetectum, may be able to mediate these visual functions.

Diffusion tensor imaging of the corticospinal tract following cerebral hemispherectomy

Following cerebral hemispherectomy, the corticospinal tract is believed to undergo reorganizational changes, which can induce enhanced function of the contralateral motor pathway and mediate partial recovery of motor function. The aim of this study was to use diffusion tensor imaging to investigate the effects of hemispherectomy on the corticospinal tract, with particular attention to the corticospinal tract contralateral to the resection. Diffusion tensor imaging would presumably detect microstructural abnormalities through quantitative measurements of the fiber tract integrity and orientation. Four patients with anatomic hemispherectomy and three patients with subtotal hemispherectomy were examined and compared with age-matched normal controls. Apparent diffusion coefficient and fractional anisotropy values were measured in regions along the corticospinal tract: internal capsule, cerebral peduncle, rostral pons, midpons, and caudal pons. None of the patients with anatomic hemispherectomy or subtotal hemispherectomy showed significant changes in either apparent diffusion coefficient or fractional anisotropy values in the corticospinal tract contralateral to the resected hemisphere, whereas increased apparent diffusion coefficient and decreased fractional anisotropy were observed in the ipsilateral rostral pons, midpons, and caudal pons of all patients with anatomic hemispherectomy, as well as in the ipsilateral cerebral peduncle of one patient with subtotal hemispherectomy. Increased apparent diffusion coefficient values were also noted in the ipsilateral internal capsule of the same patient. This study revealed no evidence of significant reinforcement of the contralateral corticospinal tract in patients with hemispherectomy, at least from diffusion tensor imaging measurements, but suggests that wallerian degeneration most likely occurs in the ipsilateral motor pathway.

Hemispherectomy: a schematic review of the current techniques

Anatomical hemispherectomy has been used for the treatment of seizures since 1938. However, it was almost abandoned in the 1960s after reports of postoperative fatalities caused by hydrocephalus, hemosiderosis, and trivial head traumas. Despite serious complications, the remarkable improvement of patients encouraged authors to carry out modifications on anatomical hemispherectomy in order to lessen its morbidity while preserving its efficacy. The effort to improve the technique generated several original procedures. This paper reviews current techniques of hemispherectomy and proposes a classification scheme based on their surgical characteristics. Techniques of hemispherectomy were sorted into two major groups: (1) those that remove completely the cortex from the hemisphere and (2) those that associate partial cortical removal and disconnection. Group 1 was subdivided into two subgroups based on the integrity of the ventricular cavity and group 2 was subdivided into three subgroups depending on the amount and location of the corticectomy. Grouping similar techniques may allow a better understanding of the distinctive features of each one and creates the possibility of comparing data from different authors.

Pathophysiology and functional consequences of human partial epilepsy: lessons from positron emission tomography studies

Positron emission tomography (PET) is a powerful clinical and research tool that, in the past two decades, has provided a great amount of novel data on the pathophysiology and functional consequences of human epilepsy. PET studies revealed cortical and subcortical brain dysfunction of a widespread brain circuitry, providing an unprecedented insight in the complex functional abnormalities of the epileptic brain. Correlation of metabolic and neuroreceptor PET abnormalities with electroclinical variables helped identify parts of this circuitry, some of which are directly related to primary epileptogenesis, while others, adjacent to or remote from the primary epileptic focus, may be secondary to longstanding epilepsy. PET studies have also provided detailed data on the functional anatomy of cognitive and behavioral abnormalities associated with epilepsy. PET, along with other neuroimaging modalities, can measure longitudinal changes in brain function attributed to chronic seizures as well as therapeutic interventions. This review demonstrates how development of more specific PET tracers and application of multimodality imaging by combining structural and functional neuroimaging with electrophysiological data can further improve our understanding of human partial epilepsy, and helps more effective application of PET in presurgical evaluation of patients with intractable seizures.

'Seeing' in the blind hemifield following hemispherectomy

Destruction of the striate cortex has traditionally been thought to lead to permanent blindness in the contralateral visual field and to the dogma that this region is indispensable for vision in primates. For over 25 years now, evidence has been accumulating that hemianopic human subjects and monkeys possess wide-ranging residual visual capacities or 'blindsight' in the blind part of their visual field. For some researchers, isolated islands of the striate cortex have been associated with patches of degraded vision and made responsible for blindisight. Artefacts such as light scatter, criterion effects, macular sparing, eccentric fixation and minute eye movements have also been linked with the residual vision. For others, the fact that certain aspects of the visual information can be processed without the geniculostriate pathway suggests mediation by the visual subsystems such as extrastriate visual cortical areas which receive visual information via subcortical pathways, that escaped the cortical damage. Subjects who have had a whole cerebral hemisphere removed or disconnected (for the treatment of uncontrollable epilepsy) and who show residual vision in their blind field offer a remarkable opportunity to help clear the controversy regarding the neural substrate of blindsight. Because it is certain that no functional striate or extrastriate cortex remains on the ablated side, these subjects have contributed significantly to identifying the critical pathways involved in blindsight.

Functional imaging correlates of recovery after stroke in humans

The mechanisms that are responsible for the remarkable potential for functional recovery from stroke in humans remain unclear, and functional tomographic neuroimaging techniques increasingly are being used to investigate this issue. Such studies confirmed that recovery of function is related to the volume of penumbra tissue that escapes infarction. For language, reactivation of the primary functional areas in the dominant hemisphere is associated with the best prognosis. Evidence for functional plasticity in the immediate vicinity of infarcts, as demonstrated under experimental conditions with invasive methods, is still limited after stroke in humans, probably because of the limitations of spatial resolution of most currently available methods. Often, functional changes in the large-scale networks that support motor (for example, supplementary and premotor cortex) and language functions (for example, prefrontal cortex) have been found, more extensively after lesions acquired during childhood than at adult age. A frequent finding is an increase in the cerebral blood flow response in corresponding regions of the healthy hemisphere during unilateral motor activation or language activation. It is, however, not yet clear whether that is related to functional recovery, and there are several observations indicating that it is often inefficient. Further systematic follow-up studies and therapeutic intervention trials are needed to clarify these issues.

In vivo imaging of neuronal activation and plasticity in the rat brain by high resolution positron emission tomography (microPET)

The study of neural repair and neuroplasticity in rodents would be enhanced by the ability to assess neuronal function in vivo. Positron emission tomography (PET) is used to study brain plasticity in humans, but the limited resolution and sensitivity of conventional scanners have generally precluded the use of PET to study neuroplasticity in rodents. We now demonstrate that microPET, a PET scanner developed for use with small animals, can be used to assess metabolic activity in different regions of the conscious rodent brain using [18F]fluorodeoxyglucose (FDG) as the tracer, and to monitor changes in neuronal activity. Limbic seizures result in dramatically elevated metabolic activity in the hippocampus, whereas vibrissal stimulation results in more modest increases in FDG uptake in the contralateral neocortex. We also show that microPET can be used to study lesion-induced plasticity of the brain. Cerebral hemidecortication resulted in diminished relative glucose metabolism in the neostriatum and thalamus ipsilateral to the lesion, with subsequent, significant recovery of metabolic function. These studies demonstrate that microPET can be used for serial assessment of metabolic function of individual, awake rats with a minimal degree of invasiveness, and therefore, has the potential for use in the study of brain disorders and repair.

Evaluation of gross and fine motor functions in children with hemidecortication: predictors of outcomes and timing of surgery

The purpose of this study is three-fold: First, to determine the levels of gross and fine motor functions in children before and after hemidecortication, using standardized measurement tools; second, to investigate if predictors of these outcomes can be characterized; and third, to explore if both clinical measures and functional magnetic resonance imaging (MRI) potentially can identify optimal timing of surgery. The Gross Motor Function Measure and the Quality of Upper Extremity Skills Test are shown to be comprehensive, standardized outcome measures of movement performance in affected children. Age at surgery and interval between age at seizure onset and age at surgery could be the most reliable predictors of clinical outcomes. Functional MRI studies are valuable in exploring the potential of the cortical reorganization that sustains residual sensorimotor function. The combination of clinical measures with functional MRI is a promising method of inquiry into developmental and plasticity processes.

Application of positron emission tomography to determine cerebral glucose utilization in conscious infant monkeys

Cerebral glucose metabolism has been used as a marker of cerebral maturation and neuroplasticity. In studies addressing these issues in young non-human primates, investigators have used positron emission tomography (PET) and [18F]2-fluoro-2-deoxy-D-glucose (FDG) to calculate local cerebral metabolic rates of glucose (1CMRG1c). Unfortunately, these values were influenced by anesthesia. In order to avoid this confounding factor, we have established a method that permits reliable measurements in young conscious vervet monkeys using FDG-PET. Immature animals remained in a conscious, resting state during the initial 42 min of FDG uptake as they were allowed to cling to their anesthetized mothers. After FDG uptake, animals were anesthetized and placed in the PET scanner with data acquisition beginning at 60 min post-FDG injection. FDG image sets consisted of 30 planes separated by 1.69 mm, parameters sufficient to image the entire monkey brain. Our method of region-of-interest (ROI) analysis was assessed within and between raters and demonstrated high reliability (P < 0.001). To illustrate that our method was sensitive to developmental changes in cerebral glucose metabolism, quantitative studies of young conscious monkeys revealed that infant monkeys 6-8 months of age exhibited significantly higher 1CMRG1c values (P < 0.05) in all regions examined, except sensorimotor cortex and thalamus, compared to monkeys younger than 4 months of age. This method provided high resolution images and 1CMRG1c values that were reliable within age group. These results support the application of FDG-PET to investigate questions related to cerebral glucose metabolism in young conscious non-human primates.

Regionalized sensorimotor plasticity after hemispherectomy fMRI evaluation

This study demonstrates the transfer of both motor and sensory functions from one hemisphere to the other in children who had an entire cortical hemisphere surgically removed. The areas of the cortex responsible for these new functions in the remaining hemisphere are associative motor and sensory areas and do not include the typical primary motor and somatosensory regions, thus suggesting the regionalization of brain plasticity. This regionalization can be evaluated with functional magnetic resonance imaging, supporting this technique as an effective tool in the study of brain plasticity.

Brain organization of language after early unilateral lesion: a PET study

Neuropsychological studies suggest that good long-term language outcome is possible following extensive early left-hemisphere damage. We explored the brain organization for language in children with early unilateral lesion, using [15O]-water PET. In 12 patients with left lesion (LL) and 9 patients with right lesion (RL), cerebral blood flow changes during listening to sentences and repetition were studied. A rightward shift of language activations in the LL group was found in perisylvian areas and multiple other, mostly temporo-parietal, regions. The hypothesis of intrahemispheric reorganization in the LL group found only limited support. The number of activated regions was overall greater in the RL group. Unexpected findings included a stronger subcortical and cerebellar language involvement in the RL group. We suggest that (a) early left lesion is associated with enhanced language participation of the right hemisphere in and beyond the classical language areas, and (b) postlesional effects are in part additive (recruitment of noncanonical areas), in part subtractive (functional depression in areas normally involved in language).

Differences in D2 dopamine receptor binding in the neostriatum between cats hemidecorticated neonatally or in adulthood

In order to study differences in response to neocortical injury sustained at different ages at the neurotransmitter level, we examined the density in D2 dopamine receptors in the neostriatum of cats hemidecorticated neonatally (N = 4) or in adulthood (N = 4), as well as in intact brains (N = 6). Receptor densities were measured using quantitative autoradiography and [3H]-spiperone binding in 12 regions of the neostriatum and nucleus accumbens septi. We found that the anterior lateral caudate nucleus on both sides of the brain contained a higher D2 receptor density in neonatal-lesioned as compared to adult-lesioned brains. Ipsilateral to the lesion, the increase was 101% (P < 0.05) and contralaterally it amounted to 77% (P < 0.05). Moreover, this region of the ipsilateral caudate nucleus of neonatal-lesioned cats tended to be more densely labeled than that of intact brain by 58% (P < 0.1). D2 receptor densities in adult-lesioned cats did not differ from that of intact controls. Comparison of these data with those of a former morphological study using the same animals suggested that this bilateral elevation of D2 receptor density in neonatally lesioned brains represents a higher mean density of binding sites per neuron. The elevation in the neonatal-lesioned cats might be a response of the striatum to neuroplastic changes in the striatal neuropil, including the corticostriatal afferents, since such changes are different in neonatal- as compared to adult-lesioned cats.

Cavum septi pellucidi and cavum vergae in normal and developmentally delayed populations

Recent studies have shown that the persistence of the cavum septi pellucidi beyond the neonatal period is a marker of cerebral dysgenesis. It has been suggested that the finding of a persistent cavum vergae is also a marker of disturbed brain development. In order to investigate this hypothesis we reviewed 161 brain magnetic resonance imaging scans from normal individuals for the presence of cavum septi pellucidi or cavum vergae, or both. In the 34 prospectively obtained normal adults, there were no individuals with either a cavum septi pellucidi or cavum vergae. In the "defined" normal subjects 3 of 127 individuals (2.4%) had a cavum septi pellucidi whereas a cavum vergae was noted in 26 of 127 (20.5%). We next reviewed the neuroimaging studies of 249 children and adults evaluated for mental retardation or developmental delay. A cavum septi pellucidi was found in 38 of 249 (15.3%) and a cavum vergae in 48 of 249 (19.3%) of these patients. A cavum septi pellucidi and cavum vergae were found together in 19 of 249 (7.6%). We interpret these data as showing that the cavum septi pellucidi is rarely seen in normal individuals although the cavum vergae is seen with the same frequency in normal and retarded populations. Thus we conclude that the cavum septi pellucidi serves as a significant marker of cerebral dysfunction manifested by neurodevelopmental abnormalities while the cavum vergae alone does not identify individuals at risk for cognitive delays.

Glucose metabolism in the human cerebellum: an analysis of crossed cerebellar diaschisis in children with unilateral cerebral injury

Using high-resolution positron emission tomography (PET), we have recently described the normal pattern of glucose utilization in 11 anatomical regions of the human cerebellum. In the present study, we evaluated the phenomenon of crossed cerebellar diaschisis in 40 patients (mostly children) with unilateral cerebral injury sustained at various periods of brain development. Diaschisis refers to a functional impairment at a remote site following injury to an anatomically connected area of brain and, presumably due to a loss of afferent input to the remote site. Of the 40 patients, 11 had sustained their cerebral injury prenatally, 7 in the perinatal period (+/- 24 hours of birth), and 22 postnatally (1 day to 15 years). Crossed cerebellar hypometabolism was seen in 22 patients; symmetric cerebellar metabolism was found in 16 subjects. The presence of crossed cerebellar hypometabolism was typically associated (75% of cases) with a postnatal injury, while symmetric cerebellar metabolism was seen only in patients with injury occurring prior to 4 weeks of age (13 of the 16 had prenatal or perinatal insults). A third pattern of cerebellar metabolism, consisting of paradoxical crossed cerebellar hypermetabolism, was seen in two patients; both had sustained their cerebral injury at 4 months of age. These findings suggest the presence of considerable plasticity, which is dependent on age at injury, in the cerebrocerebellar pathway of developing brain.

Functional brain reorganization in children

Developmental brain plasticity in association with focal brain injury is dependent on a number of factors, including age of the individual at the time of injury, size and topography of the brain lesion, maturational state of the brain system injured, integrity of brain areas surrounding and contralateral to the lesion, presence and duration of epilepsy, and medication effects. Recently developed functional neuroimaging tools now make it possible to study non-invasively several aspects of human brain functional reorganization in response to injury. Clinical models which are suitable for the study of developmental brain plasticity include patients who have undergone cortical resections for the alleviation of intractable epilepsy, patients who have sustained unilateral cerebrovascular insults at various periods of development, patients with chronic progressive unilateral brain injury such as in the Sturge-Weber syndrome, and patients with early sensory deprivation such as blind or deaf subjects. Although evidence of functional brain reorganization can be demonstrated in these models, it is emphasized that the neurobiological rules that govern intrahemispheric versus interhemispheric reorganization of function in the brain are, at present, poorly understood.

Hemispherectomy: a hemidecortication approach and review of 52 cases

Between 1975 and 1994, 52 hemispherectomies, of which two were anatomical and 50 hemidecortications, were performed at Johns Hopkins Medical Institutions. Eighteen patients were 2 years old or less. There were three perioperative mortalities and one patient died 9 months later from causes not related to surgery. One patient developed hydrocephalus 6 years postsurgery and has been treated effectively. Seizure control and the functional status of each patient were measured as outcome variables. Forty-six (96%) of the surviving patients were seizure free or had reduced seizures as of their last follow-up examination. Twenty-one individuals (44%) were participating in age-appropriate classes or working independently, 18 were classified as semiindependent, and nine children will likely depend on a lifetime of assisted living. The relationships between the outcome variables and the patient's age at surgery, the interval to surgery, and the etiology of the disease were compared. The authors' clinical experiences strongly suggest the importance of a multidisciplinary approach to patient selection and follow-up care. Moreover, anesthetic management of infant surgery is a major component of success.

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.

Where are we with nuclear medicine in pediatrics?

The practice of nuclear medicine in children is different from that in adults. Technical considerations including immobilization, dosing of radiopharmaceuticals, and instrumentation are of major importance. Image magnification and the capability to perform single-photon emission tomography are essential to performing state of the art pediatric nuclear medicine. New advances in instrumentation with multiple detector imaging, the possibility of clinical positron emission tomography imaging in children, and new radiopharmaceuticals will further enhance pediatric scintigraphic imaging. This review highlights advances in pediatric nuclear medicine and discusses selected clinical problems.