Age-specific cerebral perfusion in 4- to 15-year-old children: a high-resolution brain SPET study using 99mTc-ECD

Preseason Cerebrovascular Function in Adolescent Athletes

The purpose of this study was to investigate the effects of sport participation, concussion history, and age of first exposure to football on preseason cerebrovascular function in adolescent athletes. Athletes (n = 53, age = 15.8 ± 1.2 years) were examined based on three exposure groupings: (1) sport participation (football vs. non-collision), (2) concussion history (none vs. ≥ 1), and (3) age of first exposure (football participants only). Transcranial Doppler assessed cerebrovascular reactivity (CVR) and neurovascular coupling (NVC), and separate independent samples t-tests evaluated group differences in CVR and NVC outcomes. Separate univariate linear regressions determined how age of first exposure related to CVR and NVC outcomes. Linear mixed effects models assessed group differences in CVR and NVC relative response curves. Differential response to NVC visual task response was significantly greater in non-collision sport athletes (F_1,2946 = 38.69, p < 0.0001) and athletes without a concussion history (F_1,2946 = 25.23, p < 0.0001). Older age of first exposure significantly predicted reduced breath-holding CVR response (F_1,1560 = 2.92, p = 0.03). Healthy adolescent athletes have similar pre-season cerebrovascular function despite different sport participation and concussion history. However, age of first exposure may predict CVR in adolescent football athletes. Developmental literature identifies cerebrovascular function as dynamically changing throughout adolescence. Our study provides fundamental data informing the clinical meaningfulness of short- and long-term physiological function changes.

Quantitative evaluation of regional cerebral blood flow changes during childhood using 123I-N-isopropyl-iodoamphetamine single-photon emission computed tomography

OBJECTIVE

To quantitatively evaluate regional cerebral blood flow (rCBF) and regional developmental changes during childhood using ¹²³I-N-isopropyl-iodoamphetamine single-photon emission computed tomography (SPECT) and autoradiography.

METHODS

We retrospectively analyzed quantitative values of rCBF in 75 children (29 girls) aged between 16 days and 178 months (median: 12 months), whose brain images, including magnetic resonance imaging and SPECT data, were normal under visual inspection at Saitama Children's Medical Center between 2005 and 2015. The subjects had normal psychomotor development, no focal neurological abnormalities, and neither respiratory nor cardiac disease at the time of examination. Regions of interest were placed automatically using a three-dimensional stereotactic template.

RESULTS

rCBF was lowest in neonates, who had greater rCBF in the lenticular nucleus, thalamus, and cerebellum than the cerebral cortices. rCBF increased rapidly during the first year of life, reaching approximately twice the adult levels at 8 years, and then fell to approximately adult levels in the late teenage years. Cerebral cortex rCBF sequentially increased in the posterior, central, parietal, temporal, and callosomarginal regions during infancy and childhood.

CONCLUSIONS

rCBF changed dramatically throughout childhood and ranged from lower than adult values to approximately two times higher than adult values. It had different trajectories in each region during brain development. Understanding this dynamic developmental change is necessary for SPECT image evaluation in children.

Age-related differences in cerebral blood flow underlie the BOLD fMRI signal in childhood

Functional magnetic resonance imaging (fMRI) has become a premiere technique for studying the development and neural mediation of a wide range of typical and atypical behaviors in children. While the mechanism of the blood oxygen level-dependent (BOLD) fMRI signal has been a focus of investigation in the mature brain, it has been largely unexamined in the developing brain. One critical component of the BOLD signal that has been noted to change with age is cerebral blood flow (CBF). Reports of CBF in children based on clinical radioactive tracing methods have found elevated CBF in childhood relative to adulthood, which could affect the BOLD response. This study used non-invasive arterial spin labeling magnetic resonance imaging to study resting state and activity-driven CBF in conjunction with the functional BOLD response in healthy children 8 and 12 years of age and in adults. Participants performed a finger-tapping task to generate robust activation measured in the motor cortex. Quantification of resting state CBF demonstrated higher CBF in 8 year olds and in 12 year olds relative to adults. The absolute increase in CBF between baseline rest and peak response during the motor task was also higher in both child groups compared to adults. In contrast, the relative increase of CBF above baseline, expressed as percent of CBF change, was comparable across groups. The percent of BOLD signal change was also stable across age groups. This set of findings suggests that along with elevated CBF in childhood, other component processes of the BOLD response are also in an elevated state such that together they yield a net BOLD effect that resembles adults. These findings coincide with our previous examination of hemodynamics in primary sensory cortex. Although the magnitude of the BOLD response appears consistent between childhood and adulthood, the underlying physiology and cerebrovascular dynamics that give rise to the BOLD effect differ between immature and mature neural systems.

Developmental changes in resting and functional cerebral blood flow and their relationship to the BOLD response

Our understanding of cerebral blood flow (CBF) in the healthy developing brain has been limited due to the invasiveness of methods historically available for CBF measurement. Clinically based studies using radioactive tracers with children have focused on resting state CBF. Yet potential age-related changes in flow during stimulation may affect the blood oxygenation level dependent (BOLD) response used to investigate cognitive neurodevelopment. This study used noninvasive arterial spin labeling magnetic resonance imaging to compare resting state and stimulus-driven CBF between typically developing children 8 years of age, 12 years of age, and adults. Further, we acquired functional CBF and BOLD images simultaneously to examine their relationship during sensory stimulation. Analyses revealed age-related CBF differences during rest; the youngest group showed greater CBF than 12-year-olds or adults. During stimulation of the auditory cortex, younger children also showed a greater absolute increase in CBF than adults. However, the magnitude of CBF response above baseline was comparable between groups. Similarly, the amplitude of the BOLD response was stable across age. The combination of the 8 year olds' elevated CBF, both at rest and in response to stimulation, without elevation in the BOLD response suggests that additional physiological factors that also play a role in the BOLD effect, such as metabolic processes that are also elevated in this period, may offset the increased CBF in these children. Thus, CBF measurements reveal maturational differences in the hemodynamics underlying the BOLD effect in children despite the resemblance of the BOLD response between children and adults.

Switching to sulphonylureas in children with iDEND syndrome caused by KCNJ11 mutations results in improved cerebellar perfusion

OBJECTIVE

Activating mutations in the KCNJ11 gene, encoding the Kir6.2 subunit of the KATP channel, result in permanent neonatal diabetes mellitus. They also may cause neurologic symptoms such as mental retardation and motor problems (iDEND syndrome) and epilepsy (DEND syndrome). Sulphonylurea (SU) treatment is reported to alleviate both the neurologic symptoms and diabetes in such cases. The study aimed to establish the magnitude and functional basis of the effect of SUs on the neurologic phenotype in children with iDEND using neuroimaging before and after insulin replacement with glibenclamide.

RESEARCH DESIGN AND METHODS

To localize and quantify the effect of glibenclamide administration, we performed single-photon emission computed tomography in seven patients with different mutations in KCNJ11. In five patients, measurements before and after initiation of SU treatment were performed. RESULTS Significant changes in single-photon emission computed tomography signal intensity after transfer to SU therapy were restricted to the cerebellum, consistent with previous data showing high Kir6.2 expression in this brain region. Cerebellar perfusion improved for both left (P = 0.006) and right (P = 0.01) hemispheres, with the mean improvement being 26.7 ± 7.1% (n = 5). No patients showed deterioration of cerebellar perfusion on SU therapy. Electrophysiological studies revealed a good correlation between the magnitude of KATP channel dysfunction and the clinical phenotype; mutant channels with the greatest reduction in adenosine 5'-triphosphate inhibition were associated with the most severe neurologic symptoms.

CONCLUSIONS

We conclude it is likely that at least some of the beneficial effects of SU treatment on neurodevelopment in iDEND patients result from improved cerebellar perfusion.

The effects of propofol on cerebral perfusion MRI in children

INTRODUCTION

The effects of anesthesia are infrequently considered when interpreting pediatric perfusion magnetic resonance imaging (MRI). The objectives of this study were to test for measurable differences in MR measures of cerebral blood flow (CBF) and cerebral blood volume (CBV) between non-sedated and propofol-sedated children, and to identify influential factors.

METHODS

Supratentorial cortical CBF and CBV measured by dynamic susceptibility contrast perfusion MRI in 37 children (1.8-18 years) treated for infratentorial brain tumors receiving propofol (IV, n = 19) or no sedation (NS, n = 18) were compared between groups and correlated with age, hematocrit (Hct), end-tidal CO₂ (ETCO₂), dose, weight, and history of radiation therapy (RT). The model most predictive of CBF and CBV was identified by multiple linear regression.

RESULTS

Anterior cerebral artery (ACA) and middle cerebral artery (MCA) territory CBF were significantly lower, and MCA territory CBV greater (p = 0.03), in IV than NS patients (p = 0.01, 0.04). The usual trend of decreasing CBF with age was reversed with propofol in ACA and MCA territories (r = 0.53, r = 0.47; p < 0.05). ACA and MCA CBF (r = 0.59, 0.49; p < 0.05) and CBV in ACA, MCA, and posterior cerebral artery territories (r = 0.73, 0.80, 0.52; p < 0.05) increased with weight in propofol-sedated children, with no significant additional influence from age, ETCO₂, hematocrit, or RT.

CONCLUSION

In propofol-sedated children, usual age-related decreases in CBF were reversed, and increases in CBF and CBV were weight-dependent, not previously described. Weight-dependent increases in propofol clearance may diminish suppression of CBF and CBV. Prospective study is required to establish anesthetic-specific models of CBF and CBV in children.

Serotonin and dopamine transporter binding in children with autism determined by SPECT

Disturbances in the serotonergic system have been recognized in autism. To investigate the association between serotonin and dopamine transporters and autism, we studied 15 children (14 males, one female; mean age 8 y 8 mo [SD 3 y 10 mo]) with autism and 10 non-autistic comparison children (five males, five females; mean age 9 y 10 mo [SD 2 y 8 mo]) using single-photon emission computed tomography (SPECT) with [123 I] nor-beta-CIT. The children, with autism were studied during light sedation. They showed reduced serotonin transporter (SERT) binding capacity in the medial frontal cortex, midbrain, and temporal lobe areas. However, after correction due to the estimated effect of sedation, the difference remained significant only in the medial frontal cortex area (p=0.002). In the individuals with autism dopamine transporter (DAT) binding did not differ from that of the comparison group. The results indicate that SERT binding capacity is disturbed in autism. The reduction is more evident in adolescence than in earlier childhood. The low SERT binding reported here and the low serotonin synthesis capacity shown elsewhere may indicate maturation of a lesser number of serotonergic nerve terminals in individuals with autism.

Maturation of speech and language functional neuroanatomy in pediatric normal controls

PURPOSE

This study explores the relationship between age and resting-state regional cerebral blood flow (rCBF) in regions associated with higher order language skills using a population of normal children, adolescents, and young adults.

METHOD

rCBF was measured in 33 normal participants between the ages of 7 and 19 years using single photon emission computed tomography. Participants' ages were regressed on rCBF values (normalized to whole-brain CBF) in 2 ways: (a) within anatomically defined, language-related regions of interest (ROIs) including Wernicke's area, Broca's area, angular gyrus, planum temporale, and Heschl's gyrus and (b) within clusters of voxels found to be significantly related to age in voxel-wise analyses.

RESULTS

rCBF in all anatomically defined ROIs except Heschl's gyrus declined as a function of age. Additionally, voxel-wise analyses revealed clusters where rCBF declined with age in left inferior parietal, left superior temporal, and right middle temporal regions-areas often implicated in higher order language functions.

CONCLUSIONS

These data suggest that ongoing maturation (e.g., dendritic pruning) in higher order cognitive areas (e.g., angular gyrus) continues into adolescence, as reflected by declining rCBF, while the primary auditory area (Heschl's gyrus) has become a stable neuronal population by age 7 years.

Regional cerebral blood flow in children with ADHD: changes with age

The aim of this study was to investigate the changes in regional cerebral blood flow (rCBF) with age in patients with attention deficit hyperactivity disorder (ADHD). Twenty-nine drug-naive ADHD subjects (24 boys, 5 girls; age 7-13; mean+/-SD=age 9.2+/-2.1) and 12 subjects with epilepsy (all diagnosed as having complex partial seizure, 6 boys, 6 girls; age 7-14; mean+/-SD=8.5+/-2.1) were included in the study. All cases of ADHD were diagnosed according to DSM-IV criteria. Cerebral blood flow was evaluated with Tc-99m-hexamethylpropyleneamine oxime (Tc99m HMPAO) brain single photon emission tomography (SPECT) during standard resting condition in all of the cases. Asymmetry indices for each region of interest were calculated. Absolute rCBF values were normalized as the absolute rCBF values divided by the whole brain absolute value. The prefrontal lobe asymmetry indices were significantly negatively correlated with age in ADHD cases (r=-0.408, P=0.025), which indicated the increased prefrontal rCBF lateralization from the right to the left side with age. When ADHD cases older than 7 years of age were compared with those with epilepsy, the ADHD cases had lower right prefrontal and frontal rCBF and higher left parietal rCBF. The epilepsy group showed no significant correlations between age and asymmetry indices and showed a different developmental trajectory for prefrontal asymmetry and right prefrontal rCBF values. The results indicated that the left hemisphere dominance in the prefrontal cortex significantly increases with age in ADHD cases.

The influence of cortical maturation on the BOLD response: an fMRI study of visual cortex in children

We performed blood oxygenation level-dependent (BOLD) functional MR imaging in 11 children younger than 5 y of age and 10 children older than 5 y of age. All but five of the children in the older age group were tested under light anesthesia. We examined the cerebral oxidative metabolism (CMRO(2)) associated with the processing of a flashed and a reversing checkerboard stimulus. These stimuli had been shown in a previous study to induce identical vascular responses. The reversing checkerboard activated twice the neuronal population of the flashed checkerboard, doubling the CMRO(2) associated with it. We compared the extent of activation for the positive BOLD response and found that it did not differ between the different age groups. We estimated the oxidative metabolism by examining the change in the local deoxyhemoglobin (HbR) concentration using Delta R2*. Because both stimuli induced the same vascular response, any increase in oxygen requirement would have to be met by the identical blood volume. Increasing CMRO(2) will therefore result in an increase in the oxygen extraction fraction (OEF), which raises the local HbR concentration. In the younger children, both checkerboard stimuli produced identical, high HbR concentrations. In the older children, the HbR concentration to the flashed stimulus was significantly lower than to the reversing stimulus. We conclude that, for identical stimuli, the oxidative energy requirement associated with the cortical processing is higher in young children than in older children because the presence of superfluous synaptic connections in the immature visual system activates a larger neuronal population.

Age-associated changes of cerebral glucose metabolic activity in both male and female deaf children: parametric analysis using objective volume of interest and voxel-based mapping

Quantitative analysis of brain activity in the brains of children requires the establishment of age-associated norms. We investigated regional differences in age-associated changes in fluorodeoxyglucose (FDG) uptake in the developmental brains. From 87 (44 male and 43 female) deaf children from the age of 1 to 15, brain FDG positron emission tomography (PET) images were examined after spatial normalization, smoothing, and global normalization to identify brain regions showing a correlation between FDG uptake and age. Using population-based probabilistic volume of interests (VOIs), an objective VOI analysis was performed where normalized relative FDG uptake was measured and their correlations with age were examined in both genders. For the voxel-based analyses, the correlations with age were examined in a general linear model using statistical parametric mapping (SPM99). Both methods revealed that FDG uptake linearly increases with age both in the bilateral inferior prefrontal/orbitofrontal gyri and the right dorsomedial frontal gyrus and decreases in the inferior temporal gyrus and internal capsule white matter. Male children showed age-associated increases of FDG uptake in the right dorsomedial frontal gyrus, and female children in the left dorsolateral prefrontal cortex and thalamus. These changes in FDG uptake in various brain regions may suggest changes in synaptic density or regional activity resulting from normal maturation or deaf-induced adaptation. Caution should be exercised in interpreting the differences in the brain of child patients when compared with adult control's or with a different gender. Further research will be needed to examine if gender difference is manifested in the development rate of behavioral/cognitive functions in association with the age-associated changes of the right medial frontal (male) or the left dorsolateral prefrontal cortices.

Brain perfusion in children: evolution with age assessed by quantitative perfusion computed tomography

OBJECTIVE

The objective of this study was to assess the age-related variations of brain perfusion through quantitative cerebral perfusion computed tomography (CT) results in children without brain abnormality.

METHODS

Brain perfusion CT examinations were performed in 77 children, aged 7 days to 18 years. These patients were admitted at our institution for both noncontrast and contrast-enhanced cerebral CT. Only children whose conventional cerebral CT and clinical/radiologic follow-up, including additional investigations, were normal were taken into account for this study (53 of 77).

RESULTS

The average regional rCBF amounts to 40 (mL/100 g per minute) for the first 6 months of life, peaks at approximately 130 (mL/100 g per minute) at approximately 2 to 4 years of age, and finally stabilizes at approximately 50 (mL/100 g per minute) at approximately 7 to 8 years of age, with a small increase of rCBF values at approximately 12 years of age. The rCBF in the gray matter averages 3 times that in the white matter, except for the first 6 months of life. The global CBF represents 10% to 20% of the global cardiac output for the first 6 months of life, peaks at approximately 55% by 2 to 4 years of age, and finally stabilizes at approximately 15% by 7 to 8 years of age. Specific age-related evolution patterns were identified in the different anatomic areas of the cerebral parenchyma, which could be related to the development of neuroanatomic structures and to the emergence of corresponding cognitive functions.

CONCLUSIONS

Quantitative perfusion CT characterization of brain perfusion shows specific age variations. Brain perfusion of each cortical area evolves according to a specific time course, in close correlation with the psychomotor development.

Pediatric perfusion imaging using pulsed arterial spin labeling

PURPOSE

To test the feasibility of pediatric perfusion imaging using a pulsed arterial spin labeling (ASL) technique at 1.5 T.

MATERIALS AND METHODS

ASL perfusion imaging was carried out on seven neurologically normal children and five healthy adults. The signal-to-noise ratio (SNR) of the perfusion images along with T1, M(0), arterial transit time, and the temporal fluctuation of the ASL image series were measured and compared between the two age groups. In addition, ASL perfusion magnetic resonance (MR) was performed on three children with neurologic disorder.

RESULTS

In the cohort of neurologically normal children, a 70% increase in the SNR of the ASL perfusion images and a 30% increase in the absolute cerebral blood flow compared to the adult data were observed. The measures of ASL SNR, T1, and M(0) were found to decrease linearly with age. Transit time and temporal fluctuation of the ASL perfusion image series were not significantly different between the two age groups. The feasibility of ASL in the diagnosis of pediatric neurologic disease was also illustrated.

CONCLUSION

ASL is a promising tool for pediatric perfusion imaging given the unique and reciprocal benefits in terms of safety and image quality.

Prospective value of perfusion and X-ray attenuation imaging with single-photon emission and transmission computed tomography in acute cerebral ischemia

BACKGROUND AND PURPOSE

The aim of the present study was to test the hypothesis that perfusion single-photon emission computed tomography (SPECT), carried out in addition to transmission computed tomography (TCT), improves the predictive value of brain imaging within the therapeutically relevant time window after acute cerebral ischemia.

METHODS

Using TCT and [(99m)Tc]ethyl cysteinate dimer (ECD)-SPECT within 6 hours after symptom onset, we examined 108 patients (44 women, 64 men; mean age 65+/-13 years) with acute ischemic stroke attributed to the territory of the middle cerebral artery (MCA). In each case, 3 experts prospectively evaluated the early SPECT and TCT images. We correlated these ratings with follow-up TCT findings for the final infarction as well as with clinical outcome (Scandinavian Stroke Scale, Barthel Index, Modified Rankin Scale) after 30 and 90 days.

RESULTS

Severe activity deficits on SPECT, not caused by local atrophy on TCT, were the best predictors (positive predictive value [PPV ]94%, 95% CI 89% to 99%; negative predictive value [NPV] 90%, 95% CI 78% to 100%; P<0.001) for evolving cerebral infarction. Complete MCA infarctions were predicted with significantly higher accuracy with early SPECT (area under receiver operating characteristic curve [AUC] index 0.91) compared with early TCT (AUC index 0.77) and clinical parameters (AUC index 0.73, P<0.05). Logistic regression analysis revealed 1 independent predictor for completed MCA territory infarction: SPECT activity deficits in the corresponding areas (PPV 88%, 95% CI 65% to 100%; NPV 96%, 95% CI 92% to 100%; P<0.001). Furthermore, death after stroke was optimally predicted by [(99m)Tc]ECD-SPECT. Clinical outcome up to 90 days after the stroke event best correlated with the degree of activity deficits in early SPECT (r=0.53, P<0.001).

CONCLUSIONS

[(99m)Tc]ECD brain perfusion SPECT that completes TCT definitely improves the predictive value of brain imaging after acute cerebral ischemia. Thus, the combined imaging of brain edema and of cerebral perfusion early after stroke is recommended for clinical use.

Stages of increased cerebral blood flow accompany stages of rapid brain growth

Stages of increased cerebral blood flow accompany stages of rapid brain growth The existence of stages of rapid brain growth implies the existence of associated stages of increased cerebral blood flow (CBF) to supply the substances and energy needed for the added brain weight. Studies in the literature give developmental data for CBF in humans which show stages of increased cerebral blood flow at ages starting just preceding and/or coincident with the ages of the rapid brain growth stages. Confirmation of the implication for one of the earliest stages is also found in PET data. Additionally, data for rodents show a similar association of stages of increasing CBF and their brain growth stages. Thus, to the accuracy of the data, the implication is confirmed. Finding stages in cerebral blood flow predicts the existence of stages of brain growth. In addition; finding correlated blood flow stages also supports the age spans of the stages of rapid brain growth in both species. Such correlations also suggest that measurements of blood flow anywhere in the body might serve to reveal rapid growth stages in particular localities or organs if the blood flow shows significant stages. The ratio of energy consumed in brain to that in total body decreases from close to 100% at birth to the adult value of about 20% by age 18 years.

Cerebral blood flow and glucose metabolism in long-term survivors of childhood acute lymphoblastic leukaemia

Central nervous system treatment for childhood acute lymphoblastic leukaemia (ALL) has been reported to cause changes in cerebral blood flow and glucose metabolism. Little is known about the association of these functional changes with neuropsychological defects and structural changes. The aim of the present study was to assess the relationship between changes in regional cerebral blood flow and glucose utilisation in long-term survivors of ALL, and the association of these functional abnormalities with neurocognitive and structural defects. 8 survivors of childhood ALL were studied with single photon emission tomography (SPECT) using Tc99m-ethyl cysteinate dimer (ECD) as tracer and with positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) as tracer. 8 healthy controls also underwent FDG-PET. All subjects also underwent magnetic resonance imaging and neuropsychological assessment 5 years after cessation of the therapy. Focal cerebral blood flow abnormalities were found in ECD-SPECT in 5 of the 8 survivors. Glucose utilisation appeared normal in the corresponding regions. However, glucose utilisation was decreased in thalamus and cerebellum in the survivors of ALL as compared with healthy controls. 3 patients had severe and 5 patients mild neurocognitive difficulties. The changes in cerebral blood flow and FDG uptake did not correspond neuroanatomically with the neurocognitive defects. Focal defects in cerebral blood flow in long-term survivors of ALL are not associated with changes in local cerebral glucose utilisation. Neurocognitive difficulties are not consistently associated with either changes in cerebral blood flow or with decreased glucose utilisation. Therefore, based on the present set of studies FDG-PET and ECD-SPECT cannot yet be recommended for the evaluation of long-term neurocognitive defects associated with treatment of ALL.