Kristen W. Yeom, Robert M. Lober, Sonia Partap, Nicholas Telischak, Rachel Tsolinas, Patrick D. Barnes, and Michael S. B. Edwards
Focal hemosiderin deposition (FHD) is commonly observed on brain MRI scans of patients treated for childhood medulloblastoma (MB). The authors sought to determine the clinical significance of FHD and its relationship to patient age, radiation dose, and cognitive outcomes.
A single-institution retrospective study of 93 MB patients at Lucile Packard Children's Hospital at Stanford from 1998 to 2011 identified 41 patients with a negative baseline MRI scan and at least 2 posttreatment MRI scans obtained with T2* gradient recalled echo (GRE). The number and cumulative rate of FHDs detectable by GRE were compared between patients aged 6 years and younger (early age) and aged 7–21 years (late age) at the time of radiotherapy (RT) and between low-dose (1800–2340 cGy) and high-dose (2920–3960 cGy) RT.
The median age at MB diagnosis was 7.3 years (range 0.9–21.0 years), the median clinical follow-up period was 5.8 years (range 0.8–13.4 years), and the median 5-year overall survival was 81% ± 7%. Of 30 school-aged children with MB, 21 (70%) required special education, and the median IQ of 10 tested patients was 100 (range 50–118). Thirty-three patients (80%) had FHD after a median latency of 1.9 years (range 0.1–5.9 years). Ninety-four percent (436 of 466) of the lesions arose in the supratentorial region of the brain, whereas 29 (6%) resided in the brainstem or the cerebellum. No spinal lesions were observed on routine spine MRI scans using T2 fast spin echo imaging. The mean cumulative lesion rate per year was 2.23 ± 3.05, and this rate was higher in older children at the time of RT compared with younger children (3.23 vs 0.67 per year, p = 0.002) but did not differ among different RT doses (p = 0.395). A child's IQ or need for special education showed no significant correlation with the rate of lesion development or number of lesions. None of the lesions resulted in symptomatic hemorrhage that required surgical intervention.
More FHD was observed in children treated for MB at the older ages than in those treated at the younger ages. There was no significant association of the incidence of FHD with radiation dose or cognitive outcomes, and none of the lesions required surgical intervention.
Robert M. Lober, Raphael Guzman, Samuel H. Cheshier, Douglas R. Fredrick, Michael S. B. Edwards, and Kristen W. Yeom
Magnetic resonance imaging is commonly used in diagnosis and surveillance for optic pathway glioma (OPG). The authors investigated the role of diffusion tensor (DT) tractography in assessing the location of visual pathway fibers in the presence of tumor.
Data in 10 children with OPG were acquired using a 3T MRI generalized autocalibrating parallel acquisitions DT–echo planar imaging sequence (25 isotropic directions with a b value of 1000 seconds/mm2, slice thickness 3 mm). Fiber tractography was performed, with seed regions placed within the optic chiasm and bilateral nerves on the coronal plane, including the tumor and surrounding normal-appearing tissue. Tracking was performed with a curvature threshold of 30°.
For prechiasmatic lesions, fibers either stopped abruptly at the tumor or traversed abnormally dilated nerve segments. Similar findings were seen with chiasmatic lesions, with an additional arrangement in which fibers diverged around the tumor. For each patient, DT tractography provided additional information about visual fiber arrangement in relation to the tumor that was not evident by using conventional MRI methods. Retrospective reconstruction of visual fibers in 1 patient with new postoperative hemianopia revealed an unexpected superior displacement of the optic tract that might have been helpful information had it been applied to preoperative planning or surgical navigation.
Optic pathway DT tractography is feasible in patients with OPG and provides new information about the arrangement of visual fibers in relation to tumors that could be incorporated into surgical navigation for tumor biopsy or debulking procedures.
Jennifer L. Quon, Lily H. Kim, Robert M. Lober, Maryam Maleki, Gary K. Steinberg, and Kristen W. Yeom
Moyamoya disease is a dynamic cerebrovascular condition that often requires vascular surveillance. Arterial spin labeling (ASL) is an MR perfusion method that is increasingly used for stroke and other various neurovascular pathologies. Unlike perfusion-weighted MRI, ASL uses endogenous water molecules for signal and therefore obviates gadolinium use; and provides direct, not relative, quantitative cerebral blood flow (CBF) measures. Presently, the potential role of ASL for evaluating postoperative pediatric moyamoya patients is relatively unexplored. This study investigated the role for ASL in evaluating cerebral hemodynamic changes in children who underwent revascularization surgery.
This retrospective study examined 15 consecutive pediatric patients with moyamoya disease (n = 7) or moyamoya syndrome (n = 8) presenting between 2010 and 2014 who underwent revascularization and in whom 3T ASL was performed pre- and postoperatively. Postoperative MRI at least 3 months after revascularization procedure was used for analysis. Quantitative CBF in various vascular territories was interrogated: anterior, middle, and posterior cerebral arteries, and basal ganglia supplied by the lenticulostriate collaterals, resulting in evaluation of 20 brain regions.
After revascularization, CBF in the high middle cerebral artery territory significantly increased (p = 0.0059), accompanied by a decrease in CBF to the ipsilateral lenticulostriate-supplied basal ganglia (p = 0.0053). No perfusion changes occurred in the remaining cerebral vascular territories after surgery.
ASL-based quantitative CBF showed improved cerebral perfusion to the middle cerebral artery territory after revascularization in children with both moyamoya syndrome and disease. Reduced perfusion to the basal ganglia might reflect pruning of the lenticulostriate collaterals, potentially from effects of revascularization. ASL can quantitatively evaluate hemodynamic changes in children with moyamoya after revascularization, and it may be a useful adjunct to routine clinical MRI surveillance.
Omar Choudhri, Robert M. Lober, Joaquin Camara-Quintana, Kristen W. Yeom, Raphael Guzman, and Michael S. B. Edwards
The authors describe the application of a flexible CO2 laser for corpus callosotomy in children with epilepsy.
This retrospective case series reviews all cases in which pediatric patients underwent a corpus callosotomy performed using the CO2 OmniGuide laser between May 2005 and October 2012. Data were collected from 8 corpus callosotomy procedures in 6 pediatric patients presenting with medically refractory epilepsy marked by drop attacks.
Complete corpus callosotomies were performed in 6 patients (3 boys, 3 girls; ages 5–14 years). In 4 patients the complete callosotomy occurred as a single procedure, and in 2 patients an anterior two-thirds callosotomy was performed first. These 2 patients subsequently required a complete callosotomy due to inadequate control of their drop attacks. In all cases there was clean lesioning of the tract with preservation of the ependymal plane and less inadvertent thermal tissue damage due to low penetration of the laser through cerebrospinal fluid. All patients had resolution or improvement of drop attacks after surgery. No complications were encountered, and imaging demonstrated a clean sectioning of callosal fibers with preservation of normal ventricular anatomy.
These cases illustrate the use of this device in completing corpus callosotomy in pediatric patients. The low-profile laser fiber tip was well suited for working in the depths of the interhemispheric fissure with minimal brain retraction. The flexible CO2 laser allows a precise callosal lesioning through an interhemispheric approach and is a useful adjunct to be employed in these cases.
Melanie G. Hayden Gephart, Robert M. Lober, Robert T. Arrigo, Corinna C. Zygourakis, Raphael Guzman, Maxwell Boakye, Michael S. B. Edwards, and Paul G. Fisher
Pediatric primary spinal cord tumors (PSCTs) are rare, with limited comprehensive data regarding incidence and patterns of diagnosis and treatment. The authors evaluated trends in the diagnosis and treatment of PSCTs using a nationwide database.
The Surveillance, Epidemiology, and End Results (SEER) registry was queried for the years 1975–2007, evaluating clinical patterns in 330 patients 19 years of age or younger in whom a pediatric PSCT had been diagnosed. Histological diagnoses were grouped into pilocytic astrocytoma, other low-grade astrocytoma, ependymoma, and high-grade glioma. Patient demographics, tumor pathology, use of external beam radiation (EBR), and overall survival were analyzed.
The incidence of pediatric PSCT was 0.09 case per 100,000 person-years and did not change over time. Males were more commonly affected than females (58% vs 42%, respectively; p < 0.006). Over the last 3 decades, the specific diagnoses of pilocytic astrocytoma and ependymoma increased, whereas the use of EBR decreased (60.6% from 1975 to 1989 vs 31.3% from 1990 to 2007; p < 0.0001). The 5- and 10-year survival rates did not differ between these time periods.
While the incidence of pediatric PSCT has not changed over time, the pattern of pathological diagnoses has shifted, and pilocytic astrocytoma and ependymoma have been increasingly diagnosed. The use of EBR over time has declined. Relative survival of patients with low-grade PSCT has remained high regardless of the pathological diagnosis.
Katie Shpanskaya, Jennifer L. Quon, Robert M. Lober, Sid Nair, Eli Johnson, Samuel H. Cheshier, Michael S. B. Edwards, Gerald A. Grant, and Kristen W. Yeom
While conventional imaging can readily identify ventricular enlargement in hydrocephalus, structural changes that underlie microscopic tissue injury might be more difficult to capture. MRI-based diffusion tensor imaging (DTI) uses properties of water motion to uncover changes in the tissue microenvironment. The authors hypothesized that DTI can identify alterations in optic nerve microstructure in children with hydrocephalus.
The authors retrospectively reviewed 21 children (< 18 years old) who underwent DTI before and after neurosurgical intervention for acute obstructive hydrocephalus from posterior fossa tumors. Their optic nerve quantitative DTI metrics of mean diffusivity (MD) and fractional anisotropy (FA) were compared to those of 21 age-matched healthy controls.
Patients with hydrocephalus had increased MD and decreased FA in bilateral optic nerves, compared to controls (p < 0.001). Normalization of bilateral optic nerve MD and FA on short-term follow-up (median 1 day) after neurosurgical intervention was observed, as was near-complete recovery of MD on long-term follow-up (median 1.8 years).
DTI was used to demonstrate reversible alterations of optic nerve microstructure in children presenting acutely with obstructive hydrocephalus. Alterations in optic nerve MD and FA returned to near-normal levels on short- and long-term follow-up, suggesting that surgical intervention can restore optic nerve tissue microstructure. This technique is a safe, noninvasive imaging tool that quantifies alterations of neural tissue, with a potential role for evaluation of pediatric hydrocephalus.
Jennifer L. Quon, Michelle Han, Lily H. Kim, Mary Ellen Koran, Leo C. Chen, Edward H. Lee, Jason Wright, Vijay Ramaswamy, Robert M. Lober, Michael D. Taylor, Gerald A. Grant, Samuel H. Cheshier, John R. W. Kestle, Michael S. B. Edwards, and Kristen W. Yeom
Imaging evaluation of the cerebral ventricles is important for clinical decision-making in pediatric hydrocephalus. Although quantitative measurements of ventricular size, over time, can facilitate objective comparison, automated tools for calculating ventricular volume are not structured for clinical use. The authors aimed to develop a fully automated deep learning (DL) model for pediatric cerebral ventricle segmentation and volume calculation for widespread clinical implementation across multiple hospitals.
The study cohort consisted of 200 children with obstructive hydrocephalus from four pediatric hospitals, along with 199 controls. Manual ventricle segmentation and volume calculation values served as “ground truth” data. An encoder-decoder convolutional neural network architecture, in which T2-weighted MR images were used as input, automatically delineated the ventricles and output volumetric measurements. On a held-out test set, segmentation accuracy was assessed using the Dice similarity coefficient (0 to 1) and volume calculation was assessed using linear regression. Model generalizability was evaluated on an external MRI data set from a fifth hospital. The DL model performance was compared against FreeSurfer research segmentation software.
Model segmentation performed with an overall Dice score of 0.901 (0.946 in hydrocephalus, 0.856 in controls). The model generalized to external MR images from a fifth pediatric hospital with a Dice score of 0.926. The model was more accurate than FreeSurfer, with faster operating times (1.48 seconds per scan).
The authors present a DL model for automatic ventricle segmentation and volume calculation that is more accurate and rapid than currently available methods. With near-immediate volumetric output and reliable performance across institutional scanner types, this model can be adapted to the real-time clinical evaluation of hydrocephalus and improve clinician workflow.