Non-invasive in-utero quantification of vascular reactivity in human placenta

OBJECTIVE

Placental vascular reactivity (PlVR) indicates the ability of the placental vasculature to match blood supply to fetal demand. Many pregnancy disorders alter the characteristics of PlVR, resulting in suboptimal oxygen delivery, although current understanding is limited by the lack of non-invasive, repeatable methods to measure PlVR in utero. Our objective was to quantify PlVR by measuring the placental response to transient changes in maternal carbon dioxide (CO2) using blood-oxygen-level-dependent (BOLD) magnetic resonance imaging (MRI). We hypothesized that PlVR will increase with gestational age to meet the changing demands of a growing fetus, and that PlVR will be driven by a maternal response to changes in CO2 concentration.

METHODS

This was a cross-sectional study of 35 women with a healthy singleton pregnancy, of whom 31 were included in the analysis. The median gestational age was 32.6 (range, 22.6-38.4) weeks. Pregnant women were instructed to follow audiovisual breathing cues during a MRI scan. Maternal end-tidal CO2 (EtCO2) was measured concurrently with resting placental BOLD MRI for a total of 7-8 min. Preprocessing of magnetic resonance images consisted of manual delineation of placental anatomy and motion correction. In each placental voxel, vascular reactivity was computed using a coherence-weighted general linear model between MRI signal and EtCO2 stimulus. Global PlVR was computed as the mean of voxel-wise PlVR values across the placenta.

RESULTS

PlVR, quantified by the placental response to induced, transient changes in maternal CO2, was consistently measured in utero using BOLD MRI. PlVR increased non-linearly with advancing gestational age (P < 0.001) and was higher on the fetal side of the placenta. PlVR was associated positively with fetal brain volume after accounting for gestational age. PlVR did not show any significant associations with maternal characteristics.

CONCLUSIONS

We present, for the first time, a non-invasive paradigm to quantify PlVR in ongoing human pregnancies without the use of exogenous gases or contrast agents. Our findings suggest that PlVR is driven by a fetal response to changes in maternal CO2. Ease of translation to the clinical setting makes PlVR a promising biomarker for the identification and management of high-risk pregnancies. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

ADC Histogram Analysis of Pediatric Low-Grade Glioma Treated with Selumetinib: A Report from the Pediatric Brain Tumor Consortium

BACKGROUND AND PURPOSE

Selumetinib is a promising MAP (mitogen-activated protein) kinase (MEK) 1/2 inhibitor treatment for pediatric low-grade gliomas. We hypothesized that MR imaging-derived ADC histogram metrics would be associated with survival and response to treatment with selumetinib.

MATERIALS AND METHODS

Children with recurrent, refractory, or progressive pediatric low-grade gliomas who had World Health Organization grade I pilocytic astrocytoma with KIAA1549-BRAF fusion or the BRAF V600E mutation (stratum 1), neurofibromatosis type 1-associated pediatric low-grade gliomas (stratum 3), or sporadic non-neurofibromatosis type 1 optic pathway and hypothalamic glioma (OPHG) (stratum 4) were treated with selumetinib for up to 2 years. Quantitative ADC histogram metrics were analyzed for total and enhancing tumor volumes at baseline and during treatment.

RESULTS

Each stratum comprised 25 patients. Stratum 1 responders showed lower values of SD of baseline ADC_total as well as a larger decrease with time on treatment in ADC_total mean, mode, and median compared with nonresponders. Stratum 3 responders showed a greater longitudinal decrease in ADC_total. In stratum 4, higher baseline ADC_total skewness and kurtosis were associated with shorter progression-free survival. When all 3 strata were combined, responders showed a greater decrease with time in ADC_total mode and median. Compared with sporadic OPHG, neurofibromatosis type 1-associated OPHG had lower values of ADC_total mean, mode, and median as well as ADC_enhancement mean and median and higher values of ADC_total skewness and kurtosis at baseline. The longitudinal decrease in ADC_total median during treatment was significantly greater in sporadic OPHG compared with neurofibromatosis type 1-associated OPHG.

CONCLUSIONS

ADC histogram metrics are associated with progression-free survival and response to treatment with selumetinib in pediatric low-grade gliomas.

Ventricular shape and relative position abnormalities in preterm neonates

Recent neuroimaging findings have highlighted the impact of premature birth on subcortical development and morphological changes in the deep grey nuclei and ventricular system. To help characterize subcortical microstructural changes in preterm neonates, we recently implemented a multivariate tensor-based method (mTBM). This method allows to precisely measure local surface deformation of brain structures in infants. Here, we investigated ventricular abnormalities and their spatial relationships with surrounding subcortical structures in preterm neonates. We performed regional group comparisons on the surface morphometry and relative position of the lateral ventricles between 19 full-term and 17 preterm born neonates at term-equivalent age. Furthermore, a relative pose analysis was used to detect individual differences in translation, rotation, and scale of a given brain structure with respect to an average. Our mTBM results revealed broad areas of alterations on the frontal horn and body of the left ventricle, and narrower areas of differences on the temporal horn of the right ventricle. A significant shift in the rotation of the left ventricle was also found in preterm neonates. Furthermore, we located significant correlations between morphology and pose parameters of the lateral ventricles and that of the putamen and thalamus. These results show that regional abnormalities on the surface and pose of the ventricles are also associated with alterations on the putamen and thalamus. The complementarity of the information provided by the surface and pose analysis may help to identify abnormal white and grey matter growth, hinting toward a pattern of neural and cellular dysmaturation.

Synchronous Aberrant Cerebellar and Opercular Development in Fetuses and Neonates with Congenital Heart Disease: Correlation with Early Communicative Neurodevelopmental Outcomes, Initial Experience

Patients with congenital heart disease (CHD) demonstrate multidomain cognitive delays. Cingulo-opercular and cerebellar brain networks are critical to language functions. This is a description of our initial experience aiming to identify an anatomic correlate for CHD patients with expressive language delays. Fetal CHD patients, prospectively enrolled, underwent serial fetal (1.5T), postnatal pre- and postoperative (3T) MRI. Non-CHD patients were enrolled retrospectively from the same epoch. Comparable fetal and neonatal T2 contrast was used for manual linear cross-sectional measurement. Multivariable analysis was used for adjustments and curve fitting. Neurodevelopment was assessed with Battelle Developmental Inventory, 2nd ed. between 9 and 36 months of age. This interim analysis included patients from our longitudinal CHD study who had fetal, postnatal imaging and neurodevelopmental data-yielding a total of 62 mothers (11 CHD fetuses and 51 non-CHD fetuses). Altered brain trajectories were seen in selected cerebellar and opercular measurements in CHD patients compared with the non-CHD group. Smaller inferior cerebellar vermis measurements were associated with multiple communication-related abnormalities. Altered early structural development of the cerebellum and operculum is present in patients with CHD, which correlates with specific neurodevelopmental abnormalities.

Parametric Response Mapping of Apparent Diffusion Coefficient as an Imaging Biomarker to Distinguish Pseudoprogression from True Tumor Progression in Peptide-Based Vaccine Therapy for Pediatric Diffuse Intrinsic Pontine Glioma

BACKGROUND AND PURPOSE

Immune response to cancer therapy may result in pseudoprogression, which can only be identified retrospectively and may disrupt an effective therapy. This study assesses whether serial parametric response mapping (a voxel-by-voxel method of image analysis also known as functional diffusion mapping) analysis of ADC measurements following peptide-based vaccination may help prospectively distinguish progression from pseudoprogression in pediatric patients with diffuse intrinsic pontine gliomas.

MATERIALS AND METHODS

From 2009 to 2012, 21 children, 4-18 years of age, with diffuse intrinsic pontine gliomas were enrolled in a serial peptide-based vaccination protocol following radiation therapy. DWI was acquired before immunotherapy and at 6-week intervals during vaccine treatment. Pseudoprogression was identified retrospectively on the basis of clinical and radiographic findings, excluding DWI. Parametric response mapping was used to analyze 96 scans, comparing ADC measures at multiple time points (from the first vaccine to up to 12 weeks after the vaccine was halted) with prevaccine baseline values. Log-transformed fractional increased ADC, fractional decreased ADC, and parametric response mapping ratio (fractional increased ADC/fractional decreased ADC) were compared between patients with and without pseudoprogression, by using generalized estimating equations with inverse weighting by cluster size.

RESULTS

Median survival was 13.1 months from diagnosis (range, 6.4-24.9 months). Four of 21 children (19%) were assessed as experiencing pseudoprogression. Patients with pseudoprogression had higher fitted average log-transformed parametric response mapping ratios (P = .01) and fractional decreased ADCs (P = .0004), compared with patients without pseudoprogression.

CONCLUSIONS

Serial parametric response mapping of ADC, performed at multiple time points of therapy, may distinguish pseudoprogression from true progression in patients with diffuse intrinsic pontine gliomas treated with peptide-based vaccination.

Regional brain injury on conventional and diffusion weighted MRI is associated with outcome after pediatric cardiac arrest

BACKGROUND

To assess regional brain injury on magnetic resonance imaging (MRI) after pediatric cardiac arrest (CA) and to associate regional injury with patient outcome and effects of hypothermia therapy for neuroprotection.

METHODS

We performed a retrospective chart review with prospective imaging analysis. Children between 1 week and 17 years of age who had a brain MRI in the first 2 weeks after CA without other acute brain injury between 2002 and 2008 were included. Brain MRI (1.5 T General Electric, Milwaukee, WI, USA) images were analyzed by 2 blinded neuroradiologists with adjudication; images were visually graded. Brain lobes, basal ganglia, thalamus, brain stem, and cerebellum were analyzed using T1, T2, and diffusion-weighted images (DWI).

RESULTS

We examined 28 subjects with median age 1.9 years (IQR 0.4-13.0) and 19 (68 %) males. Increased intensity on T2 in the basal ganglia and restricted diffusion in the brain lobes were associated with unfavorable outcome (all P < 0.05). Therapeutic hypothermia had no effect on regional brain injury. Repeat brain MRI was infrequently performed but demonstrated evolution of lesions.

CONCLUSION

Children with lesions in the basal ganglia on conventional MRI and brain lobes on DWI within the first 2 weeks after CA represent a group with increased risk of poor outcome. These findings may be important for developing neuroprotective strategies based on regional brain injury and for evaluating response to therapy in interventional clinical trials.

Abnormal cerebral microstructure in premature neonates with congenital heart disease

BACKGROUND AND PURPOSE

Abnormal cerebral microstructure has been documented in term neonates with congenital heart disease, portending risk for injury and poor neurodevelopmental outcome. Our hypothesis was that preterm neonates with congenital heart disease would demonstrate diffuse cerebral microstructural abnormalities when compared with critically ill neonates without congenital heart disease. A secondary aim was to identify any association between microstructural abnormalities, white matter injury (eg, punctate white matter lesions), and other clinical variables, including heart lesions.

MATERIALS AND METHODS

With the use of tract-based spatial statistics, an unbiased, voxelwise method for analyzing diffusion tensor imaging data, we compared 21 preterm neonates with congenital heart disease with 2 cohorts of neonates without congenital heart disease: 28 term and 27 preterm neonates, identified from the same neonatal intensive care unit.

RESULTS

Compared with term neonates without congenital heart disease, preterm neonates with congenital heart disease had microstructural abnormalities in widespread regions of the central white matter. However, 42% of the preterm neonates with congenital heart disease had punctate white matter lesions. When neonates with punctate white matter lesions were excluded, microstructural abnormalities remained only in the splenium. Preterm neonates with congenital heart disease had similar microstructure to preterm neonates without congenital heart disease.

CONCLUSIONS

Diffuse microstructural abnormalities were observed in preterm neonates with congenital heart disease, strongly associated with punctate white matter lesions. Independently, regional vulnerability of the splenium, a structure associated with visual spatial function, was observed in all preterm neonates with congenital heart disease.

The use of adaptive statistical iterative reconstruction in pediatric head CT: a feasibility study

BACKGROUND AND PURPOSE

Iterative reconstruction techniques facilitate CT dose reduction; though to our knowledge, no group has explored using iterative reconstruction with pediatric head CT. Our purpose was to perform a feasibility study to assess the use of ASIR in a small group of pediatric patients undergoing head CT.

MATERIALS AND METHODS

An Alderson-Rando head phantom was scanned at decreasing 10% mA intervals relative to our standard protocol, and each study was then reconstructed at 10% ASIR intervals. An intracranial region of interest was consistently placed to estimate noise. Our ventriculoperitoneal shunt CT protocol was subsequently modified, and patients were scanned at 20% ASIR with approximately 20% mA reductions. ASIR studies were anonymously compared with older non-ASIR studies from the same patients by 2 attending pediatric neuroradiologists for diagnostic utility, sharpness, noise, and artifacts.

RESULTS

The phantom study demonstrated similar noise at 100% mA/0% ASIR (3.9) and 80% mA/20% ASIR (3.7). Twelve pediatric patients were scanned at reduced dose at 20% ASIR. The average CTDI(vol) and DLP values of the 20% ASIR studies were 22.4 mGy and 338.4 mGy-cm, and for the non-ASIR studies, they were 28.8 mGy and 444.5 mGy-cm, representing statistically significant decreases in the CTDI(vol) (22.1%, P = .00007) and DLP (23.9%, P = .0005) values. There were no significant differences between the ASIR studies and non-ASIR studies with respect to diagnostic acceptability, sharpness, noise, or artifacts.

CONCLUSIONS

Our findings suggest that 20% ASIR can provide approximately 22% dose reduction in pediatric head CT without affecting image quality.

Pituitary iron and volume imaging in healthy controls

BACKGROUND AND PURPOSE

Patients with transfusional iron overload develop iron deposits in the pituitary gland, which are associated with volume loss and HH. The purpose of this study was to characterize R2 and volumetric data in a healthy population for diagnostic use in patients with transfusional iron overload.

MATERIALS AND METHODS

One hundred healthy controls without iron overload between the ages of 2 and 48 were recruited to have MR imaging of the brain to assess their pituitary R2 and volume. Pituitary R2 was assessed with a 8-echo spin-echo sequence, and pituitary volumes, by a 3D spoiled gradient-echo sequence with 1-mm(3) resolution. A 2-component continuous piecewise linear approximation was used for creating volumetric and R2 nomograms. Equations were generated from regression relationships for convenient z-score calculation.

RESULTS

Pituitary R2 rose weakly with age (r(2) = 0.19, P < .0001). Anterior and total pituitary volumes increased steadily up to 18 years of age, after which volume slightly decreased. Females had larger pituitary glands, most likely representing their larger lactotroph population.

CONCLUSIONS

From these data, a clinician can calculate the z scores for R2 and pituitary volume in patients with iron overload. Normal ranges are well-differentiated from values previously associated with endocrine disease in transfusional siderosis; this finding suggests that preclinical iron overload can be recognized and appropriately treated.

Redefining the Guillain-Barré spectrum in children: neuroimaging findings of cranial nerve involvement

GBS and its MFS variant are acute polyneuropathies that are considered to represent a continuum rather than distinct entities, due to the overlap in their clinical features. Enhancement of the CE roots represents the neuroradiologic hallmark of GBS, while findings of neuroimaging studies in MFS are usually unremarkable. Our purpose was to evaluate the MR imaging findings of polyneuropathy in 17 children affected by GBS and its MFS variant. Fourteen of our 17 patients demonstrated CE enhancement, with predominant involvement of the anterior roots. Of 6 patients who underwent MR imaging of the brain, 5 had cranial nerve involvement. In children affected by GBS-MFS, involvement of the CE roots may be considered part of a more extensive autoimmune neuropathy, as demonstrated by enhancement of cranial nerves. Brain MR imaging should be considered in the routine evaluation in pediatric patients with GBS-MFS for the evaluation of the cranial nerves.

Abnormal microstructure of the atrophic thalamus in preterm survivors with periventricular leukomalacia

BACKGROUND AND PURPOSE

The neuroanatomic substrate of cognitive deficits in long-term survivors of prematurity with PVL is poorly understood. The thalamus is critically involved in cognition via extensive interconnections with the cerebral cortex. We hypothesized that the thalamus is atrophic (reduced in volume) in childhood survivors of prematurity with neuroimaging evidence of PVL and that the atrophy is associated with selective microstructural abnormalities within its subdivisions.

MATERIALS AND METHODS

We performed quantitative volumetric and DTI measurements of the thalamus in 17 children with neuroimaging evidence of PVL (mean postconceptional age, 5.6 ± 4.0 years) who were born prematurely and compared these with 74 term control children (5.7 ± 3.4 years).

RESULTS

The major findings were the following: 1) a significant reduction in the overall volume of the thalamus in patients with PVL compared with controls (P < .0001), which also correlated with the severity of PVL (P = .001); 2) significantly decreased FA (P = .003) and increased λ(⊥) (P = .02) in the thalamus overall and increased axial, radial, and mean diffusivities in the pulvinar (P < .03), suggesting injury to afferent and efferent myelinated axons; and 3) a positive correlation of pulvinar abnormalities with those of the parieto-occipital white matter in periventricular leukomalacia, suggesting that the pulvinar abnormalities reflect secondary effects of damaged interconnections between the pulvinar and parieto-occipital cortices in the cognitive visual network.

CONCLUSIONS

There are volumetric and microstructural abnormalities of the thalamus in preterm children with PVL, very likely reflecting neuronal loss and myelinated axonal injury. The selective microstructural damage in the pulvinar very likely contributes to abnormal cognitive visual processing known to occur in such survivors.

Apparent diffusion and fractional anisotropy of diffuse intrinsic brain stem gliomas

BACKGROUND AND PURPOSE

DIBSGs have the worst prognosis among pediatric brain tumors with no improvement of outcome for several decades. In this study, we determined whether diffusion imaging could improve patient stratification and our understanding of the impact of therapies.

MATERIALS AND METHODS

Nine baseline and 24 follow-up DTI studies performed in 9 patients on a 1.5T clinical MR imaging scanner were reviewed. ADC and FA were measured for the whole lesion and at 5 anatomic levels: the rostral medulla, caudal pons, midpons, rostral pons, and caudal midbrain. Reference data were obtained from 8 controls with normal brain stem, 6 patients with medulloblastoma, and 7 patients with pilocytic astrocytoma.

RESULTS

ADC was higher in untreated DIBSG than in normal brain stem and medulloblastoma (1.14 ± 0.18 [×10⁻³ mm²/s] versus 0.75 ± 0.06 and 0.56 ± 0.05, both P < .001). FA was lower in DIBSG than in normal brain stem (0.24 ± 0.04 versus 0.43 ± 0.02, P < .001) but was higher than that in pilocytic astrocytoma (0.17 ± 0.05, P < .05). Lower baseline ADC and higher FA correlated with a worse clinical course. Correlations were more significant at the caudal midbrain than in other regions. ADC decreased and FA increased after RT. Changes of FA after RT at the caudal midbrain correlated with event-free survival.

CONCLUSIONS

Baseline ADC and FA of DIBSG revealed hypocellular tumors with extensive edema. Diffusion changes after therapy implied reduced edema but did not support a significant response to therapy. The significance of diffusion properties varied with anatomic locations, the caudal midbrain being particularly important.

In utero eye development documented by fetal MR imaging

BACKGROUND AND PURPOSE

To date, very limited attention has been given to ocular abnormalities or growth parameters detected by fetal MR imaging. Our objective was to retrospectively determine the relationship between different parameters of eye development and estimated gestational age in the human fetus by use of fetal MR imaging.

MATERIALS AND METHODS

A retrospective study was performed to measure the transverse diameter, interocular distance, and lens diameter of the globes of 127 fetuses who had a morphologically normal central nervous system. Multiple single-shot T2 fast spin-echo images were obtained with a 1.5T magnet by use of contiguous 3-mm intervals in at least 2 orthogonal planes. Loess curves were fitted to explore the relationship between gestational age and each of the 3 measurements of interest. Different models were compared statistically to determine the model of best fit.

RESULTS

For each variable of interest, the "best" model of eye growth was a quadratic function. Specifically, lens growth seems to plateau after 36 weeks of gestation, interocular distance plateaus after 36 weeks of gestation, and globe growth plateaus after 42 weeks of gestation.

CONCLUSIONS

The lens, orbit, and interocular distance growth of the fetus can be demonstrated on fetal MR imaging. All 3 measurements suggest a quadratic model of growth, which indicates slowing of growth toward the end of gestation.

Fetal microphthalmia diagnosed by magnetic resonance imaging

We report a case of fetal microphthalmia diagnosed midtrimester by ultrasound and fetal MRI. Included is a comparison of MRI measurements of normal fetuses at similar gestational age and a review of the literature.

Olfactory anomalies in CHARGE syndrome: imaging findings of a potential major diagnostic criterion

BACKGROUND AND PURPOSE

CHARGE syndrome is a genetic disorder resulting in the association of multiple congenital anomalies. Although a high prevalence of olfactory anomalies in CHARGE syndrome has been reported in autopsy and functional studies, to our knowledge, such anomalies have not been included among the diagnostic criteria, and their radiographic prevalence has not been assessed. The purpose of this research was to determine the radiographic prevalence of olfactory anomalies in a small sample of subjects with diagnosed CHARGE syndrome.

MATERIALS AND METHODS

The medical records and high-resolution MR images (section thickness < or =3 mm and in-plane resolution < or =1 mm) in 10 patients with clinically proved CHARGE syndrome were retrospectively reviewed by 3 neuroradiologists who consensually evaluated the status of the olfactory bulbs and sulci as either normal, hypoplastic, or absent. The prevalence (p) of congenital anomalies found in the medical records and of the olfactory structures was calculated with a 95% confidence interval (CI).

RESULTS

MR imaging demonstrated olfactory anomalies in all 10 patients, including either absence or hypoplasia of the olfactory bulbs and olfactory sulci (p, 100%; CI, 0.65-1.00).

CONCLUSION

These findings suggest that olfactory abnormalities detectable on high-resolution MR imaging are among the most prevalent features of CHARGE syndrome.

Citrate in pediatric CNS tumors?

BACKGROUND AND PURPOSE

In a subset of in vivo MR spectra acquired from pediatric brain tumors, we have observed an unassigned peak. The goal of this study was to determine the molecule of origin, and the prevalence and concentration of this chemical in various pediatric brain tumors.

MATERIALS AND METHODS

Single-voxel point-resolved spectroscopy (PRESS) spectra from 85 patients with brain tumors and 469 control subjects were analyzed. Citrate seemed to be a likely candidate, and model spectra of citrate were added to the basis set of metabolites for automated processing with use of LCModel software. Absolute "apparent" concentrations of citrate and the Cramer-Rao lower bounds (CRLB), indicators for the reliability of detection, were determined.

RESULTS

"Apparent" citrate was detected in 26 of 85 patients with CRLB of less than 25%. Diffuse intrinsic brain stem glioma (DIBSG) had the highest mean concentration (4.0 +/- 1.1 mmol/kg in all subjects), and 8 of 12 patients had CRLB less than 25%. A significant reduction of citrate (P < .01) was observed in 6 DIBSGs that had follow-up MR spectroscopy studies after radiation therapy. "Apparent" citrate with CRLB less than 25% was detected in 5 of 22 medulloblastomas (mean citrate, 2.9 +/- 2.2 mmol/kg), in 5 of 14 ependymomas (2.6 +/- 1.8 mmol/kg), 5 of 14 astrocytomas (1.9 +/- 1.2 mmol/kg), and 3 of 23 pilocytic astrocytomas (1.4 +/- 1.1 mmol/kg). In control subjects older than 6 months, CRLB less than 25% was not observed, whereas CRLB less than 25% was observed in 39 of 194 subjects younger than 6 months,.

CONCLUSION

MR signal consistent with citrate was observed in pediatric brain tumors and in the developing brain of infants younger than 6 months.

Quantitative short echo time 1H-MR spectroscopy of untreated pediatric brain tumors: preoperative diagnosis and characterization

PURPOSE

Our aims were to evaluate the metabolic profiles of pediatric brain tumors with short echo time (TE) MR spectroscopy and absolute quantitation of metabolite concentrations (in mmol/kg of tissue) and to describe metabolic features that distinguish individual tumor types and that may help to improve preoperative diagnosis of specific tumors.

METHODS

MR imaging examinations of 60 patients with untreated brain tumors (14 medulloblastomas, 5 anaplastic astrocytomas, 3 low-grade astrocytomas, 17 pilocytic astrocytomas, 4 anaplastic ependymomas, 5 ependymomas, 3 choroid plexus papillomas, 3 choroid plexus carcinomas, and 6 pineal germinomas) were reviewed. Single-voxel proton MR spectroscopy with a TE of 35 ms was performed and absolute metabolite concentrations were determined by using fully automated quantitation.

RESULTS

Taurine (Tau) was significantly elevated in medulloblastomas (P < .00001) compared with all other tumors pooled (All Other). Tau was also observed consistently, at lower concentration, in pineal germinomas. Creatine (Cr) was significantly reduced in pilocytic astrocytomas, distinguishing them from All Other (P < .000001). The MR spectra of choroid plexus papillomas exhibited low Cr (P < .01) concentrations; however, myoinositol was elevated (P < .01) and total choline (tCho) (P < .0001) was reduced relative to All Other. Choroid plexus carcinomas had low Cr (P < .01 versus All Other) and the lowest Cr/tCho ratio (P < .0001 versus All Other) among all tumors studied. Guanidinoacetate was reduced in low-grade astrocytomas and anaplastic astrocytomas (P < .00001) versus All Other, whereas ependymoma and anaplastic ependymomas exhibited particularly low N-acetylaspartate (P < .00001 versus All Other).

CONCLUSION

Quantitative proton MR spectroscopy reveals features of pediatric brain tumors that are likely to improve preoperative diagnoses.

Volumetric brain differences in children with periventricular T2-signal hyperintensities: a grouping by gestational age at birth

OBJECTIVE

The purpose of this study was to compare both the volumes of the lateral ventricles and the cerebral white matter with gestational age at birth of children with periventricular white matter (PVWM) T2-signal hyperintensities on MR images. The spectrum of neuromotor abnormalities associated with these hyperintensities was also determined.

MATERIALS AND METHODS

We retrospectively reviewed the MR images of 70 patients who were between the ages of 1 and 5 years and whose images showed PVWM T2-signal hyperintensities. The patients were divided into premature (n = 35 children) and term (n = 35) groups depending on their gestational age at birth. Volumetric analysis was performed on four standardized axial sections using T2-weighted images. Volumes of interest were digitized on the basis of gray-scale densities of signal intensities to define the hemispheric cerebral white matter and lateral ventricles. Age-adjusted comparisons of volumetric measurements between the premature and term groups were performed using analysis of covariance.

RESULTS

The volume of the cerebral white matter was smaller in the premature group (54 +/- 2 cm(3)) than in the term group (79 +/- 3 cm(3), p < 0.0001). The volume of the lateral ventricles was greater among the patients in the premature group (30 +/- 2 cm(3)) than among those in the term group (13 +/- 1 cm(3), p < 0.0001). Fifty percent of all the premature children had spastic diplegia or quadriplegia. Thirty-two percent of all the term children had hypotonia. There were patients in both groups whose PVWM T2-signal hyperintensities did not correlate with any neuromotor abnormalities but were associated with seizures or developmental delays.

CONCLUSION

The differences in volumetric measurements of cerebral white matter and lateral ventricles in children with PVWM T2-signal hyperintensities are related to their gestational age at birth. Several neurologic motor abnormalities are found in children with such hyperintensities.

Distribution of alpha 2-adrenergic receptor binding in the developing human brain stem

Rapid and dramatic changes occur in cardiorespiratory function during early human life. Catecholamines within select brain stem nuclei are implicated in the control of autonomic and respiratory function, including in the nucleus of the solitary tract and the dorsal motor nucleus of X. Animal and adult human studies have shown high binding to alpha 2-adrenergic receptors in these regions. To determine the developmental profile of brainstem alpha 2-adrenergic binding across early human life, we studied brain stems from five fetuses at midgestation, three newborns (37-38 postconceptional weeks), and six infants (44-61 postconceptional weeks). We used quantitative tissue receptor autoradiography with [3H]para-aminoclonidine as the radioligand and phentolamine as the displacer. In the fetal group, binding was high (63-93 fmol/mg tissue) in the nucleus of the solitary tract, dorsal motor nucleus of X, locus coeruleus, and reticular formation; it was low (< 32 fmol/mg tissue) in the principal inferior olive and basis pontis. Binding decreased in all regions with age: in infancy, the highest binding was in the intermediate range (32-62 fmol/mg tissue) and was localized to the nucleus of the solitary tract and dorsal motor nucleus of X. The most substantial decrease in binding (75%-85%) between the fetal and infant periods occurred in the pontine and medullary reticular formation and hypoglossal nucleus. Binding remained low in the principal inferior olive and basis pontis. The decreases in binding with age remained significant after quench correction. These data suggest that rapid and dramatic changes occur in early human life in the brain stem catecholaminergic system in regions related to cardiorespiratory control.

Alpha2 receptor binding in the medulla oblongata in the sudden infant death syndrome

The sudden infant death syndrome (SIDS) is the leading cause of postnatal infant mortality in the United States. Its etiology remains unknown. We propose that SIDS, or a subset of SIDS, is due to a failure of autoresuscitation, a protective brainstem response to asphyxia or hypoxia, in a vulnerable infant during a critical developmental period. Gasping is an important component of autoresuscitation that is thought to be mediated by the "gasping center" in the lateral tegmentum of the medulla, a region homologous in its cytoarchitecture and chemical anatomy to the intermediate reticular zone (IRZ) in the human. Since we found that [3H]para-aminoclonidine ([3H]PAC) binding to alpha2-adrenergic receptors localizes to this region in human infants and, thereby provides a neurochemical marker for it, we tested the hypothesis that [3H]PAC binding to alpha2-adrenergic receptors is decreased in the IRZ in SIDS victims. Using quantitative tissue autoradiography with [3H]PAC as the radioligand and phentolamine as the displacer, we analyzed alpha2-receptor binding density in the IRZ, as well as in 7 additional sites for comparison, in 10 SIDS and 10 control medullae. There were no significant differences in alpha2 receptor binding in the IRZ, vagal nuclei, or other medullary sites examined between SIDS and control cases. These results suggest that the putative gasping defect in the IRZ in SIDS victims is not related to [3H]PAC binding to alpha2-adrenergic receptors.

Differential expression of glutamate receptor subtypes in human brainstem sites involved in perinatal hypoxia-ischemia

This study delineates the development of N-methyl-D-aspartate (NMDA) and non-NMDA receptor binding in the human brainstem, particularly as it relates to issues of the trophic effects of glutamate, the glutamate-mediated ventilatory response to hypoxia, and regional excitotoxic vulnerability to perinatal hypoxia-ischemia. We used tissue autoradiography to map the development of binding to NMDA, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-proprionate (AMPA), and kainate receptors in brainstem sites involved in the glutamate ventilatory response to hypoxia, as well as recognized sites vulnerable to perinatal hypoxia-ischemia. NMDA receptor/channel binding was virtually undetectable in all regions of the human fetal brainstem at midgestation, an unexpected finding given the trophic role for NMDA receptors in early central nervous system maturation in experimental animals. In contrast, non-NMDA (AMPA and kainate) receptor binding was markedly elevated in multiple nuclei at midgestation. Although NMDA binding increased between midgestation and early infancy to moderately high adult levels, AMPA binding dramatically fell over the same time period to low adult levels. High levels of kainate binding did not change significantly between midgestation and infancy, except for an elevation in the infant compared with fetal inferior olive; after infancy, kainate binding decreased to negligible adult levels. Our data further suggest a differential development of components of the NMDA receptor/channel complex. This baseline information is critical in considering glutaminergic mechanisms in human brainstem development, physiology, and pathology.

Decreased serotonergic receptor binding in rhombic lip-derived regions of the medulla oblongata in the sudden infant death syndrome

The sudden infant death syndrome (SIDS) is postulated to result from a failure of homeostatic responses to life-threatening challenges (e.g. asphyxia, hypercapnia) during sleep. The ventral medulla participates in sleep-related homeostatic responses, including chemoreception, arousal, airway reflex control, thermoregulation, respiratory drive, and blood pressure regulation, in part via serotonin and its receptors. The ventral medulla in humans contains the arcuate nucleus, in which we have shown isolated defects in muscarinic and kainate receptor binding in SIDS victims. We also have demonstrated that the arcuate nucleus is anatomically linked to the nucleus raphé obscurus, a medullary region with serotonergic neurons. We tested the hypothesis that serotonergic receptor binding is decreased in both the arcuate nucleus and nucleus raphé obscurus in SIDS victims. Using quantitative autoradiography, 3H-lysergic acid diethylamide (3H-LSD binding) to serotonergic receptors (5-HT1A-D and 5-HT2 subtypes) was measured blinded in 19 brainstem nuclei. Cases were classified as SIDS (n = 52), acute controls (infants who died suddenly and in whom a complete autopsy established a cause of death) (n = 15), or chronic cases with oxygenation disorders (n = 17). Serotonergic binding was significantly lowered in the SIDS victims compared with controls in the arcuate nucleus (SIDS, 6 +/- 1 fmol/mg tissue; acutes, 19 +/- 1; and chronics, 16 +/- 1; p = 0.0001) and n. raphé obscurus (SIDS, 28 +/- 3 fmol/mg tissue; acutes, 66 +/- 6; and chronics, 59 +/- 1; p = 0.0001). Binding, however, was also significantly lower (p < 0.05) in 4 other regions that are integral parts of the medullary raphé/serotonergic system, and/or are derived, like the arcuate nucleus and nucleus raphé obscurus, from the same embryonic anlage (rhombic lip). These data suggest that a larger neuronal network than the arcuate nucleus alone is involved in the pathogenesis of SIDS, that is, a network composed of inter-related serotonergic nuclei of the ventral medulla that are involved in homeostatic mechanisms, and/or are derived from a common embryonic anlage.

Registration of three-dimensional MR and CT studies of the cervical spine

A three-dimensional image registration technique for CT and MR studies of the cervical spine was evaluated for feasibility and efficacy. Registration by means of external fiducial markers was slightly more accurate than registration by anatomic landmarks. The interrelationships between bony (eg, neural foramina) and soft tissue structures (eg, nerve roots) in the cervical spine were more conspicuous on registered images than on conventional displays. Registration of CT and MR images may be used to examine more precisely the relationships between bony and soft tissue structures of the cervical spine.

Brainstem 3H-nicotine receptor binding in the sudden infant death syndrome

Maternal cigarette smoking during pregnancy has been shown to be a major risk factor for the sudden infant death syndrome (SIDS). We hypothesized that SIDS is associated with altered 3H-nicotine binding to nicotinic receptors in brainstem nuclei related to cardiorespiratory control and/or arousal. We analyzed 3H-nicotine binding in 14 regions in SIDS and control brainstems using quantitative tissue receptor autoradiography. Three groups were analyzed: SIDS (n = 42), acute controls (n = 15), and a chronic group with oxygenation disorders (n = 18). The arcuate nucleus, postulated to be important in cardiorespiratory control and abnormal in at least some SIDS victims, contained binding below the assay detection limits in all (SIDS and control) cases. We found no significant differences among the 3 groups in mean 3H-nicotine binding in the 14 brainstem sites analyzed. When a subset of the cases were stratified by the history of the presence or absence of maternal cigarette smoking during pregnancy, however, we found that there was no expected increase (upregulation) of nicotinic receptor binding in SIDS cases exposed to cigarette smoke in utero in 3 nuclei related to arousal or cardiorespiratory control. This finding raises the possibility that altered development of nicotinic receptors in brainstem cardiorespiratory and/or arousal circuits put at least some infants, i.e. those exposed to cigarette smoke in utero, at risk for SIDS, and underscores the need for further research into brainstem nicotinic receptors in SIDS in which detailed correlations with smoking history can be made.

Developmental changes in heterogeneous patterns of neurotransmitter receptor binding in the human interpeduncular nucleus

The interpeduncular nucleus (IPN) exhibits many complex features, including multiple subnuclei, widespread projections with the forebrain and brainstem, and neurotransmitter heterogeneity. Despite the putative importance of this nucleus, very little is known about its neurochemical development in the human. The human IPN is cytoarchitectonically simple, unlike the rat IPN, which displays considerable heterogeneity. In the following study, we hypothesized that the developing human IPN is neurochemically heterogeneous despite its cytological simplicity. The chemoarchitecture in this study was defined by neurotransmitter receptor binding patterns by using quantitative tissue autoradiography for the muscarinic, nicotinic, serotoninergic, opioid, and kainate receptors. We examined neurotransmitter receptor binding in the developing human IPN in a total of 15 cases. The midbrains of five midgestational fetuses (19-26 gestational weeks) and six infants (38-74 postconceptional weeks) were examined. The midbrain of one child (4 years) and three adults (20-68 years) were analyzed as indices of maturity. At all ages examined, high muscarinic binding was localized to the lateral subdivision of the IPN, high serotoninergic binding was localized to the dorsal IPN, and high opioid receptor binding was localized to the medial IPN. The developmental profile was unique for each radioligand. We report a heterogenous distribution of neurotransmitter receptor binding in the developing human IPN, which supports a complex role for it in human brain function.

Decreased kainate receptor binding in the arcuate nucleus of the sudden infant death syndrome

The human arcuate nucleus is postulated to be homologous to ventral medullary surface cells in animals that participate in ventilatory and blood pressure responses to hypercarbia and asphyxia. Recently, we reported a significant decrease in muscarinic cholinergic receptor binding in the arcuate nucleus in victims of the sudden infant death syndrome compared with control patients that died of acute causes. To test the specificity of the deficit to muscarinic cholinergic binding, we examined kainate binding in the arcuate nucleus in the same database. We assessed 3H-kainate binding to kainate receptors with tissue receptor autoradiography in 17 brainstem nuclei. Analysis of covariance was used to examine differences in binding by diagnosis, adjusted for postconceptional age (the covariate). Cases were classified as SIDS, 47; acute control, 15; and chronic group with oxygenation disorder, 17. (Acute controls are infants who died suddenly and unexpectedly and in whom a complete autopsy established a cause of death). The arcuate nucleus was the only region in which there was a significant difference in the age-adjusted mean kainate binding between the SIDS group (37+/-2 fmol/mg tissue) and both the acute controls (77+/-4 fmol/mg tissue) (p < 0.0001) and the chronic group (69+/-4 fmol/mg tissue) (p < 0.0001). There was a positive correlation between the density of muscarinic cholinergic and kainate binding in the SIDS cases only (R = 0.460; p = 0.003). The neurotransmitter deficit in the arcuate nucleus in SIDS victims involves more than one receptor type relevant to carbon dioxide and blood pressure responses at the ventral medullary surface.

Developmental changes in neurotransmitter receptor binding in the human periaqueductal gray

The periaqueductal gray (PAG) plays a central role in the integration of defense responses to threatening or stressful stimuli. Little is known about the neurochemical development of the human PAG around the time of birth, when the fetus makes the transition to extrauterine life and independent defense responses are needed. We analyzed receptor binding to selected neurotransmitters implicated in PAG function in 7 fetuses (19 to 26 gestational weeks), 9 infants (38 to 74 postconceptional weeks), 1 child (4 years), and 3 adults (20 to 68 years). Tissue autoradiography was used with radioligands for opioid, nicotinic, muscarinic, kainate, and serotoninergic receptors. By midgestation, binding to nicotinic, muscarinic, serotoninergic, opioid, and kainate receptors is already localized to the human PAG. The subsequent developmental profiles are unique for each radioligand. Binding to nicotinic and serotoninergic receptors decreases significantly from the fetal to mature periods, but at different tempos. In contrast, there is no significant change from midgestation to infancy for muscarinic, kainate, and opioid binding: between infancy and the mature period there is a downward trend in binding for muscarinic and kainate receptors and an upward trend for opioid receptors. This study provides baseline information about the neurochemical development of the human PAG in early life. This information is of value in considering the neurochemical substrate of the maturation of defense responses in human infancy, and in evaluating potential neurochemical disorders of the developing human PAG.

Developmental changes in [3H]lysergic acid diethylamide ([3H]LSD) binding to serotonin receptors in the human brainstem

The ontogeny of serotonin receptors in the human brainstem is largely unknown, despite the putative roles of serotonin in neural development, synaptic transmission, brainstem modulation of vegetative functions, and clinical disorders of serotonergic function. This study provides baseline information about the quantitative distribution of [3H]LSD binding to serotonergic receptors (5-HT1A-1D, 5-HT2) in the human brainstem, from midgestation through maturity, with a focus upon early infancy. Brainstems were analyzed from 5 fetuses (19-25.5 weeks postconception), 5 infants (42-55.5 weeks postconception), and 3 mature individuals (4, 20, and 52 years). Tissue autoradiography was used with [3H]LSD for total serotonergic receptor binding and [3H]LSD and serotonin for nonspecific binding; computer-based quantitation was applied. The highest levels of [3H]LSD binding occurred prenatally throughout the brainstem. At all ages, the highest relative binding localized to the rostral raphe. A marked decline in [3H]LSD binding occurred between the midgestation and infancy in brainstem regions involved in control of cardiovascular function, respiration, and pain. The fetal peak in [3H]LSD binding to 5-HT receptors is consistent with a trophic role of serotonin in immature human brainstem, and a decrease, between midgestation and infancy, in serotonergic modulation of vegetative functions controlled by the brainstem.

Three-dimensional distribution of [3H]quinuclidinyl benzilate binding to muscarinic cholinergic receptors in the developing human brainstem

Acetylcholine has been implicated in brainstem mechanisms of cardiac and ventilatory control, arousal, rapid eye movement (REM) sleep, and cranial nerve motor activity. Virtually nothing is known about the developmental profiles of cholinergic perikarya, fibers, terminals, and/or receptors in the brainstems of human fetuses and infants. This study provides baseline information about the quantitative distribution of muscarinic cholinergic receptors in fetal and infant brainstems. Brainstem sections were analyzed from 6 fetuses (median age: 21.5 postconceptional weeks), 4 premature infants (median age: 26 postconceptional weeks), and 11 infants (median age: 53 postconceptional weeks). One child and three adult brainstems were examined as indices of maturity for comparison. The postmortem interval in all cases was less than or equal to 24 hours (median: 10 hours). Muscarinic receptors were localized by autoradiographic methods with the radiolabeled antagonist [3H]quinuclidinyl benzilate ([3H]QNB). Computer-based methods permitted quantitation of [3H]QNB binding in specific nuclei and three-dimensional reconstructions of binding patterns. By midgestation, muscarinic cholinergic receptor binding is already present and regionally distributed, with the highest binding levels in the interpeduncular nucleus, inferior colliculus, griseum pontis, nucleus of the solitary tract, motor cranial nerve nuclei, and reticular formation. During the last half of gestation, [3H]QNB binding decreases in most, but not all of the nuclei sampled. The most substantial decline occurs in the reticular formation of the medulla and pons, a change that is not fully explained by progressive myelination and lipid quenching. Binding levels remain essentially constant in the inferior olive and griseum pontis. Around the time of birth or shortly thereafter, the relative distribution of binding becomes similar to that in the adult, with the highest levels in the interpeduncular nucleus and griseum pontis, although binding levels are higher overall in the infant. In the rostral pontine reticular formation, paramedian bands of high muscarinic binding are present which do not correspond to a cytoarchitectonically defined nucleus. By analogy to animal studies, these bands may comprise a major cholinoreceptive region of the human rostral pontine reticular formation involved in REM sleep. In the human interpeduncular nucleus in all age periods examined, muscarinic binding localizes to the lateral portions bilaterally, indicative of a heterogeneous chemoarchitecture. Muscarinic binding is high in the arcuate nucleus, a component of the putative respiratory chemosensitive fields along the ventral surface of the infant medulla. This observation is consistent with the known effects of muscarinic agents on chemosensitivity and ventilatory responses applied to the ventral medullary surface in animal models. The nonuniform distribution of muscarinic binding in the caudorostral plane in individual brainstem nuclei, as illustrated by three-dimensional reconstructions, underscores the need for rigorous sampling at precisely matched levels in quantitative studies. This study provides basic information toward understanding the neurochemical basis of brainstem disorders involving dysfunction of autonomic and ventilatory control, arousal, and REM sleep in preterm and full-term newborns and infants and for developing cholinergic drugs for such disorders in the pediatric population.

Developmental changes in [3H]kainate binding in human brainstem sites vulnerable to perinatal hypoxia-ischemia

The human brainstem is especially susceptible to hypoxia-ischemia in early life. To test the hypothesis that the period of vulnerability of the developing human brainstem to hypoxia-ischemia correlates with a transient elevation in kainate receptor binding, we compared the quantitative distribution of [3H]kainate binding in brainstem nuclei between four fetuses (19-26 gestational weeks), four infants (one to nine months), and three "mature" individuals (one child and two adults) without neurological disease. Quantitative tissues autoradiography was used. [3H]Kainate binding decreased in all brainstem regions from early life to maturity with the most significant decreases occurring in nuclei thought to be especially vulnerable to perinatal hypoxia-ischemia (e.g. principal inferior olive, griseum pontis, inferior colliculus and reticular core). The highest binding in the fetal and infant period was found primarily in the major cerebellar-relay nuclei. In the inferior olive and arcuate nucleus, binding increased from the fetal to the infant period, and then fell 50-61% to low mature levels. In the griseum pontis, binding decreased 60% between the fetal and mature periods. In the reticular formation, binding fell 67-78% from the fetal to mature period. These data support a correlation between the period of brainstem vulnerability to hypoxia-ischemia in early life to transient elevation in kainate binding, and are particularly relevant to the topographic brainstem patterns in perinatal hypoxia-ischemia of infantile olivary gliosis, pontosubicular necrosis and reticular core damage. Striking localization of [3H]kainate binding to rhombic lip derivatives further suggests that kainate receptors may be involved in the development and function of human brainstem-cerebellar circuitry.

Neuropathological findings in the brain of Karen Ann Quinlan. The role of the thalamus in the persistent vegetative state

BACKGROUND

Karen Ann Quinlan had a cardiopulmonary arrest in 1975 and died 10 years later, having never regained consciousness. Her story prompted a national debate about the appropriateness of life-sustaining treatment in patients who are in a persistent vegetative state and led to the development of medicolegal guidelines for the care of such patients. This report describes the neuropathologic features of Quinlan's brain.

METHODS

The entire brain and spinal cord were systematically sampled for histologic examination. The brain stem and central cerebrum were embedded en bloc and serially sectioned. Three-dimensional computer reconstructions helped visualize the topographic features of the lesions.

RESULTS

Contrary to expectation, the most severe damage was not in the cerebral cortex but in the thalamus, and the brain stem was relatively intact. The neuropathological findings included extensive bilateral thalamic scarring, bilateral cortical scars primarily in the occipital pole and parasagittal parieto-occipital region, and bilateral damage to cerebellar and focal-basal-ganglia regions. The brain stem and basal forebrain and the hypothalamic components of the ascending arousal systems and brainstem regions critical to cardiac and respiratory control were undamaged. The lesions were consistent with hypoxia-ischemia after the cardiopulmonary arrest.

CONCLUSIONS

Although the neuropathological findings in the case of Karen Ann Quinlan were complex, the disproportionately severe damage in the thalamus as compared with the cerebral cortex supports the hypothesis that the thalamus is critical for cognition and awareness and may be less essential for arousal.