Pediatric neuroimaging

Semiquantitative analysis of cerebral [18F]FDG-PET uptake in pediatric patients

BACKGROUND

Glycolytic metabolism in the brain of pediatric patients, imaged with [18F]  fluorodeoxyglucose-positron emission tomography (FDG-PET) is incompletely characterized.

OBJECTIVE

The purpose of the current study was to characterize [18F]FDG-PET brain uptake in a large sample of pediatric patients with non-central nervous system diseases as an alternative to healthy subjects to evaluate changes at different pediatric ages.

MATERIALS AND METHODS

Seven hundred ninety-five [18F]FDG-PET examinations from children < 18 years of age without central nervous system diseases were included. Each brain image was spatially normalized, and the standardized uptake value (SUV) was obtained. The SUV and the SUV relative to different pseudo-references were explored as a function of age.

RESULTS

At all evaluated ages, the occipital lobe showed the highest [18F]FDG uptake (0.27 ± 0.04 SUV/year), while the parietal lobe and brainstem had the lowest uptake (0.17 ± 0.02 SUV/year, for both regions). An increase [18F]FDG uptake was found for all brain regions until 12 years old, while no significant uptake differences were found between ages 13 (SUV = 5.39) to 17 years old (SUV = 5.52) (P < 0.0001 for the whole brain). A sex dependence was found in the SUVmean for the whole brain during adolescence (SUV 5.04-5.25 for males, 5.68-5.74 for females, P = 0.0264). Asymmetries in [18F]FDG uptake were found in the temporal and central regions during infancy.

CONCLUSIONS

Brain glycolytic metabolism of [18F]FDG, measured through the SUVmean, increased with age until early adolescence (< 13 years old), showing differences across brain regions. Age, sex, and brain region influence [18F]FDG uptake, with significant hemispheric asymmetries for temporal and central regions.

Basal Ganglia Germinoma in an Adolescent: A Case Report

Germ cell tumors are rare tumors and may pose a diagnostic dilemma. We present a 15-year-old boy with insidious onset right hemiparesis followed by polyuria and polydipsia. Later, he also developed cognitive decline and speech disturbances. Serial magnetic resonance images (MRIs) over a 2-year period showed progressive atrophy of the left caudate nucleus, along with Wallerian degeneration of the left internal capsule and crus of midbrain. Further in the course, imaging revealed an ill-defined signal intensity involving left ganglio-capsulo-thalamic region with increased perfusion which was suggestive of basal ganglia germinoma. Beta human chorionic gonadotropin levels were mildly elevated. This case illustrates an uncommon presentation of a central nervous system germinoma which is often misdiagnosed in the early stages because of its atypical symptomatology and MRI findings.

The Use of Rapid Sequence Magnetic Resonance Imaging of the Brain as a Screening Tool for the Detection of Gross Intracranial Pathology in Children Presenting to the Emergency Department With a Chief Complaint of Persistent or Recurrent Headaches

OBJECTIVE

The purpose of the study, was to assess the utility of rapid sequence brain magnetic resonance imaging (RS-MRI), as a screening tool to detect gross intracranial pathology in children that present to the emergency department, with a chief complaint of persistent or recurrent headaches. Rapid sequence MRI of the brain is a radiation-free technique that is used to evaluate ventricular size in children with shunted hydrocephalus, who present to the emergency department with symptomatology consistent with shunt malfunction.

METHODS

The study evaluated RS-MRI radiographic findings of 105 children that presented to a busy tertiary care pediatric emergency/trauma center between May 1, 2013, and May 31, 2015. The inclusion criteria for the study are as follows: (1) patient's age up to 12 years, (2) patient history of persistent or recurrent headaches, (3) no history of recent specialized intracranial imaging studies. The exclusion criteria are as follows: (1) a history of recent head injury or trauma, (2) known intracranial pathology, (3) clinical findings consistent with intracranial pathology, (4) patients that required intraprocedural sedation. A detailed explanation was given to the patient's parents/guardian, specifying that this was a "screening test" for detection of gross intracranial abnormalities and not a complete radiological evaluation that would rule out all pathology. Appropriate informed consent was obtained by the attending emergency medicine specialist, and was documented in the patient's medical record.

RESULTS

A total of 105 RS-MRI examinations were performed with an average imaging time of 75 seconds. None of the children required intraprocedural sedation, and there were no failed examinations. One patient was excluded from the study due to a pilocytic astrocytoma (not disclosed initially). There were 81 (77%) of 105 normal studies and 24 (23%) of 105 abnormal studies. One patient returned to the emergency department 2 times and was enrolled twice during the 2-year study. Of the 24 abnormal studies, 18 (75%) of 24 cases were diagnosed with sinusitis, and 1 (4.1%) of 24 cases was diagnosed with an abnormal brain mass with mild hydrocephalus due to obstruction of the caudal aspect of the fourth ventricle.

CONCLUSIONS

Rapid sequence MRI is a radiation-free useful alternative to computer tomography of the brain, when used as a screening tool for children with persistent or recurrent headaches presenting to the emergency department. This rapid imaging modality was particularly useful in identifying children with sinus disease, and contributed significantly to patient/family satisfaction with the care they receive during the emergency department visit. Additionally, RS-MRI screening was successful in detecting a serious neurosurgical emergency in one child with a cerebellar mass causing increased intracranial pressure. Further studies with large sample size are needed to corroborate our findings.

Neuroimaging at Term Equivalent Age: Is There Value for the Preterm Infant? A Narrative Summary

Advances in neuroimaging of the preterm infant have enhanced the ability to detect brain injury. This added information has been a blessing and a curse. Neuroimaging, particularly with magnetic resonance imaging, has provided greater insight into the patterns of injury and specific vulnerabilities. It has also provided a better understanding of the microscopic and functional impacts of subtle and significant injuries. While the ability to detect injury is important and irresistible, the evidence for how these injuries link to specific long-term outcomes is less clear. In addition, the impact on parents can be profound. This narrative summary will review the history and current state of brain imaging, focusing on magnetic resonance imaging in the preterm population and the current state of the evidence for how these patterns relate to long-term outcomes.

The role of computed tomography and magnetic resonance imaging for preoperative pediatric cochlear implantation work-up in academic institutions

OBJECTIVE

The goal of the study is to investigate the association of pertinent preoperative temporal bone computed tomography (CT) and brain magnetic resonance imaging (MRI) results and intraoperative surgical findings and complications of pediatric cochlear implantation reported in academic settings.

METHODS

This is a retrospective review of cochlear implant patients who received a pre-operative temporal bone CT and MRI of the brain between 2005 and 2012 at academic pediatric otolaryngology practices within children's hospitals in the United States and France. Scans were reviewed in a double-blind fashion and compared to intraoperative findings.

RESULTS

91 children were analyzed (mean age 5.54 +/- 0.58 years). A small facial recess identified on CT was associated with difficult insertion of electrodes (P = 0.0003). A prominent sigmoid sinus noted on CT was associated of difficult insertion of electrodes (P = 0.01), iatrogenic tegmen dehiscence (P = 0.005), as well as difficult round window access (P = 0.025). No specific CT finding was found to be associated with external auditory canal injury, perilymphatic gusher, or iatrogenic facial nerve injury. MRI brain and internal auditory canal findings were not predictive of surgical outcomes.

CONCLUSIONS

Preoperative CT and MRI remain an important planning tool for pediatric cochlear implantation, particularly in academic institutions. The findings of our study demonstrate that a detailed assessment of both preoperative CT and MRI are valuable for teaching and surgical planning.

Apparent Diffusion Coefficient Value Changes and Clinical Correlation in 90 Cases of Cytomegalovirus-Infected Fetuses with Unremarkable Fetal MRI Results

BACKGROUND AND PURPOSE

Cytomegalovirus is the leading intrauterine infection. Fetal MR imaging is an accepted tool for fetal brain evaluation, yet it still lacks the ability to accurately predict the extent of the neurodevelopmental impairment, especially in fetal MR imaging scans with unremarkable findings. Our hypothesis was that intrauterine cytomegalovirus infection causes diffusional changes in fetal brains and that those changes may correlate with the severity of neurodevelopmental deficiencies.

MATERIALS AND METHODS

A retrospective analysis was performed on 90 fetal MR imaging scans of cytomegalovirus-infected fetuses with unremarkable results and compared with a matched gestational age control group of 68 fetal head MR imaging scans. ADC values were measured and averaged in the frontal, parietal, occipital, and temporal lobes; basal ganglia; thalamus; and pons. For neurocognitive assessment, the Vineland Adaptive Behavior Scales, Second Edition (VABS-II) was used on 58 children in the cytomegalovirus-infected group.

RESULTS

ADC values were reduced for the cytomegalovirus-infected fetuses in most brain areas studied. The VABS-II showed no trend for the major domains or the composite score of the VABS-II for the cytomegalovirus-infected children compared with the healthy population distribution. Some subdomains showed an association between ADC values and VABS-II scores.

CONCLUSIONS

Cytomegalovirus infection causes diffuse reduction in ADC values in the fetal brain even in unremarkable fetal MR imaging scans. Cytomegalovirus-infected children with unremarkable fetal MR imaging scans do not deviate from the healthy population in the VABS-II neurocognitive assessment. ADC values were not correlated with VABS-II scores. However, the lack of clinical findings, as seen in most cytomegalovirus-infected fetuses, does not eliminate the possibility of future neurodevelopmental pathology.

Use of T2 signal intensity of cerebellar neoplasms in pediatric patients to guide preoperative staging of the neuraxis

OBJECT

The question of whether to obtain routine or selective preoperative imaging of the neuraxis in pediatric patients with cerebellar neoplasms remains a controversial topic. Staging of the neuraxis is generally considered beneficial in patients with neoplasms associated with an elevated risk of leptomeningeal dissemination (LD). When these studies are obtained preoperatively, there is a decrease in the number of false-positive images related to debris in the immediate postoperative period. Additionally, knowledge of the extent of spread has the potential to affect the risk/benefit analysis of aggressive resection. Although the majority of pediatric neurosurgeons surveyed choose to obtain selective preoperative imaging of the neuraxis in cases of cerebellar neoplasms "with findings suggestive of high-grade pathology," an evidence-based protocol in the literature is lacking. The goal of this study was to assess radiological characteristics of tumors with an elevated risk of LD and identify a method to help guide preoperative imaging of the neuraxis.

METHODS

The authors first reviewed the literature to gain an appreciation of the risk of LD of pediatric cerebellar neoplasms based on underlying histopathology and/or grade. Available evidence indicates preoperative imaging of the neuraxis in patients with Grade I tumors to be of questionable utility. In contrast, evidence suggested that preoperative imaging of the neuraxis in patients with Grades II-IV neoplasms was clinically warranted. The authors then evaluated an extensive base of neuroradiological literature to identify possible MR imaging and/or CT findings with the potential to differentiate Grade I from higher-grade neoplasms in pediatric patients. They analyzed the preoperative radiological findings in 50 pediatric patients who had undergone craniotomy for resection of cerebellar neoplasms at Vanderbilt Children's Hospital since 2003 with reference to 7 chosen radiological criteria. Logistic regression models were fit using radiological features to determine the best predictors of Grades II-IV tumors. Receiver operating characteristic methods were used to identify diagnostic properties of the best predictors.

RESULTS

The relative T2 signal intensity (RT2SI), an indirect measure of the water content of the solid component of the tumor, was best able to identify neoplasms with an elevated risk of LD. An RT2SI value of 0.71 was selected by the authors as the best operating point on the curve. Of the 31 neoplasms retrospectively designated as hypointense T2-weighted lesions (RT2SI ≤ 0.71), 30 (97%) were Grade II or higher. All medulloblastomas, ependymomas, and high-grade (Grades III and IV) neoplasms were hypointense T2-weighted lesions. Of the 19 T2-weighted hyperintense neoplasms (RT2SI > 0.71), 16 (84%) were Grade I and 3 were Grade II.

CONCLUSIONS

Measurement of the RT2SI can help predict Grade II-IV tumors at an elevated risk of leptomeningeal spread and guide staging of the neuraxis. Pediatric patients with cerebellar neoplasms found to have an RT2SI of less than or equal to 0.71 are recommended for neuraxis imaging prior to surgery.

Findings on preoperative brain MRI predict histopathology in children with cerebellar neoplasms

BACKGROUND/AIMS

The majority of pediatric patients with cerebellar neoplasms harbor pilocytic astrocytomas (PAs), medulloblastomas, or ependymomas. Knowledge of a preoperative likelihood of histopathology in this group of patients has the potential to influence many aspects of care. Previous studies have demonstrated hyperintensity on diffusion-weighted imaging to correlate with medulloblastomas. Recently, measurement of T(2)-weighted signal intensity (T2SI) was shown to be useful in identification of low-grade cerebellar neoplasms. The goal of this study was to assess whether objective findings on these MRI sequences reliably correlated with the underlying histopathology.

METHODS

We reviewed the radiologic findings of 50 pediatric patients who underwent resection of a cerebellar neoplasm since 2003 at our institution. Region of interest placement was used to calculate the relative diffusion-weighted signal intensity (rDWSI) and relative T2SI (rT2SI) of each neoplasm.

RESULTS

Tukey's multiple comparison test demonstrated medulloblastomas to have significantly higher rDWSIs than PAs/ependymomas, and PAs to have significantly higher rT2SIs than medulloblastomas/ependymomas. A simple method consisting of sequential measurement of rDWSI and rT2SI to predict histopathology was then constructed. Using this method, 39 of 50 (78%) tumors were accurately predicted.

CONCLUSION

Measurement of rDWSI and rT2SI using standard MRI of the brain can be used to predict histopathology with favorable accuracy in pediatric patients with cerebellar tumors.