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Morgan Bliss, Gerald Grant, Ethan Tittler, Tina Loven, Kristen W. Yeom and Douglas Sidell

In contrast to more common nasal and cervical lesions, the frontotemporal pit is a rarely encountered lesion that is often associated with a dermoid and may track intracranially. Due to delays in diagnosis, the propensity to spread intracranially, and the risk of infection, awareness of these lesions and appropriate diagnosis and management are important. The authors present 2 cases of frontotemporal pits from a single institution. Epidemiology, presentation, and management recommendations are discussed.

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Jennifer L. Quon, Lily H. Kim, Robert M. Lober, Maryam Maleki, Gary K. Steinberg and Kristen W. Yeom

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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Katie L. Pricola, Jason Karamchandani, Hannes Vogel, Gary V. Dahl, Kristen W. Yeom, Michael S. B. Edwards and Raphael Guzman

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder that occurs most commonly in the pediatric population as a result of pathological clonal proliferation of Langerhans cells with subsequent damage and destruction to surrounding tissue. Clinically, LCH presents in a variety of ways, which often results in prolonged time to diagnosis and subsequently poorer outcomes. In this case report, the authors describe an unusually early presentation of multisystem LCH in a patient at birth, which resulted in a 5-month delay to diagnosis and treatment. This patient presented both atypically young and with an uncommon initial manifestation of multisystem disease with multiple soft-tissue swellings rather than early skin involvement. Additionally, this patient had an unusual radiographic appearance with biparietal skull destruction on initial skull radiographs and biparietal soft-tissue lesions on CT resembling cephalohematoma at 3 months of age. The clinical and radiological evaluation, pathology, and treatment strategies are discussed, with particular attention paid to the importance of further workup of atypical nonresolving cephalohematomas to prevent disease progression and poorer outcomes.

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Robert M. Lober, Raphael Guzman, Samuel H. Cheshier, Douglas R. Fredrick, Michael S. B. Edwards and Kristen W. Yeom

Object

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.

Methods

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°.

Results

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.

Conclusions

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.

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Omar Choudhri, Robert M. Lober, Joaquin Camara-Quintana, Kristen W. Yeom, Raphael Guzman and Michael S. B. Edwards

OBJECT

The authors describe the application of a flexible CO2 laser for corpus callosotomy in children with epilepsy.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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Kristen W. Yeom, Robert M. Lober, Sonia Partap, Nicholas Telischak, Rachel Tsolinas, Patrick D. Barnes and Michael S. B. Edwards

Object

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.

Methods

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.

Results

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.

Conclusions

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.

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James Pan, Jennifer L. Quon, Eli Johnson, Bryan Lanzman, Anjeza Chukus, Allen L. Ho, Michael S. B. Edwards, Gerald A. Grant and Kristen W. Yeom

OBJECTIVE

Fast magnetic resonance imaging (fsMRI) sequences are single-shot spin echo images with fast acquisition times that have replaced CT scans for many conditions. Introduced as a means of evaluating children with hydrocephalus and macrocephaly, these sequences reduce the need for anesthesia and can be more cost-effective, especially for children who require multiple surveillance scans. However, the role of fsMRI has yet to be investigated in evaluating the posterior fossa in patients with Chiari I abnormality (CM-I). The goal of this study was to examine the diagnostic performance of fsMRI in evaluating the cerebellar tonsils in comparison to conventional MRI.

METHODS

The authors performed a retrospective analysis of 18 pediatric patients with a confirmed diagnosis of CM-I based on gold-standard conventional brain MRI and 30 controls without CM-I who had presented with various neurosurgical conditions. The CM-I patients were included if fsMRI studies had been obtained within 1 year of conventional MRI with no surgical intervention between the studies. Two neuroradiologists reviewed the studies in a blinded fashion to determine the diagnostic performance of fsMRI in detecting CM-I. For the CM-I cohort, the fsMRI and T2-weighted MRI exams were randomized, and the blinded reviewers performed tonsillar measurements on both scans.

RESULTS

The mean age of the CM-I cohort was 7.39 years, and 50% of these subjects were male. The mean time interval between fsMRI and conventional T2-weighted MRI was 97.8 days. Forty-four percent of the subjects had undergone imaging after posterior fossa decompression. The sensitivity and specificity of fsMRI in detecting CM-I was 100% (95% CI 71.51%–100%) and 92.11% (95% CI 78.62%–98.34%), respectively. If only preoperative patients are considered, both sensitivity and specificity increase to 100%. The authors also performed a cost analysis and determined that fsMRI was significantly cost-effective compared to T2-weighted MRI or CT.

CONCLUSIONS

Despite known limitations, fsMRI may serve as a useful diagnostic and surveillance tool for CM-I. It is more cost-effective than full conventional brain MRI and decreases the need for sedation in young children.

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Michael Iv, Omar Choudhri, Robert L. Dodd, Shreyas S. Vasanawala, Marcus T. Alley, Michael Moseley, Samantha J. Holdsworth, Gerald Grant, Samuel Cheshier and Kristen W. Yeom

OBJECTIVE

Patients with brain arteriovenous malformations (AVMs) often require repeat imaging with MRI or MR angiography (MRA), CT angiography (CTA), and digital subtraction angiography (DSA). The ideal imaging modality provides excellent vascular visualization without incurring added risks, such as radiation exposure. The purpose of this study is to evaluate the performance of ferumoxytol-enhanced MRA using a high-resolution 3D volumetric sequence (fe-SPGR) for visualizing and grading pediatric brain AVMs in comparison with CTA and DSA, which is the current imaging gold standard.

METHODS

In this retrospective cohort study, 21 patients with AVMs evaluated by fe-SPGR, CTA, and DSA between April 2014 and August 2017 were included. Two experienced raters graded AVMs using Spetzler-Martin criteria on all imaging studies. Lesion conspicuity (LC) and diagnostic confidence (DC) were assessed using a 5-point Likert scale, and interrater agreement was determined. The Kruskal-Wallis test was performed to assess the raters’ grades and scores of LC and DC, with subsequent post hoc pairwise comparisons to assess for statistically significant differences between pairs of groups at p < 0.05.

RESULTS

Assigned Spetzler-Martin grades for AVMs on DSA, fe-SPGR, and CTA were not significantly different (p = 0.991). LC and DC scores were higher with fe-SPGR than with CTA (p < 0.05). A significant difference in LC scores was found between CTA and fe-SPGR (p < 0.001) and CTA and DSA (p < 0.001) but not between fe-SPGR and DSA (p = 0.146). A significant difference in DC scores was found among DSA, fe-SPGR, and CTA (p < 0.001) and between all pairs of the groups (p < 0.05). Interrater agreement was good to very good for all image groups (κ = 0.77–1.0, p < 0.001).

CONCLUSIONS

Fe-SPGR performed robustly in the diagnostic evaluation of brain AVMs, with improved visual depiction of AVMs compared with CTA and comparable Spetzler-Martin grading relative to CTA and DSA.

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Lily H. Kim, Edward H. Lee, Michelle Galvez, Murat Aksoy, Stefan Skare, Rafael O’Halloran, Michael S. B. Edwards, Samantha J. Holdsworth and Kristen W. Yeom

OBJECTIVE

Spine MRI is a diagnostic modality for evaluating pediatric CNS tumors. Applying diffusion-weighted MRI (DWI) or diffusion tensor imaging (DTI) to the spine poses challenges due to intrinsic spinal anatomy that exacerbates various image-related artifacts, such as signal dropouts or pileups, geometrical distortions, and incomplete fat suppression. The zonal oblique multislice (ZOOM)–echo-planar imaging (EPI) technique reduces geometric distortion and image blurring by reducing the field of view (FOV) without signal aliasing into the FOV. The authors hypothesized that the ZOOM-EPI method for spine DTI in concert with conventional spinal MRI is an efficient method for augmenting the evaluation of pediatric spinal tumors.

METHODS

Thirty-eight consecutive patients (mean age 8 years) who underwent ZOOM-EPI spine DTI for CNS tumor workup were retrospectively identified. Patients underwent conventional spine MRI and ZOOM-EPI DTI spine MRI. Two blinded radiologists independently reviewed two sets of randomized images: conventional spine MRI without ZOOM-EPI DTI, and conventional spine MRI with ZOOM-EPI DTI. For both image sets, the reviewers scored the findings based on lesion conspicuity and diagnostic confidence using a 5-point Likert scale. The reviewers also recorded presence of tumors. Quantitative apparent diffusion coefficient (ADC) measurements of various spinal tumors were extracted. Tractography was performed in a subset of patients undergoing presurgical evaluation.

RESULTS

Sixteen patients demonstrated spinal tumor lesions. The readers were in moderate agreement (kappa = 0.61, 95% CI 0.30–0.91). The mean scores for conventional MRI and combined conventional MRI and DTI were as follows, respectively: 3.0 and 4.0 for lesion conspicuity (p = 0.0039), and 2.8 and 3.9 for diagnostic confidence (p < 0.001). ZOOM-EPI DTI identified new lesions in 3 patients. In 3 patients, tractography used for neurosurgical planning showed characteristic fiber tract projections. The mean weighted ADCs of low- and high-grade tumors were 1201 × 10−6 and 865 × 10−6 mm2/sec (p = 0.002), respectively; the mean minimum weighted ADCs were 823 × 10−6 and 474 × 10−6 mm2/sec (p = 0.0003), respectively.

CONCLUSIONS

Diffusion MRI with ZOOM-EPI can improve the detection of spinal lesions while providing quantitative diffusion information that helps distinguish low- from high-grade tumors. By adding a 2-minute DTI scan, quantitative diffusion information and tract profiles can reliably be obtained and serve as a useful adjunct to presurgical planning for pediatric spinal tumors.

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Yuhao Huang, Timothy G. Singer, Michael Iv, Bryan Lanzman, Siddharth Nair, James A. Stadler III, Jia Wang, Michael S. B. Edwards, Gerald A. Grant, Samuel H. Cheshier and Kristen W. Yeom

OBJECTIVE

Children with intracranial arteriovenous malformations (AVMs) undergo digital DSA for lesion surveillance following their initial diagnosis. However, DSA carries risks of radiation exposure, particularly for the growing pediatric brain and over lifetime. The authors evaluated whether MRI enhanced with a blood pool ferumoxytol (Fe) contrast agent (Fe-MRI) can be used for surveillance of residual or recurrent AVMs.

METHODS

A retrospective cohort was assembled of children with an established AVM diagnosis who underwent surveillance by both DSA and 3-T Fe-MRI from 2014 to 2016. Two neuroradiologists blinded to the DSA results independently assessed Fe-enhanced T1-weighted spoiled gradient recalled acquisition in steady state (Fe-SPGR) scans and, if available, arterial spin labeling (ASL) perfusion scans for residual or recurrent AVMs. Diagnostic confidence was examined using a Likert scale. Sensitivity, specificity, and intermodality reliability were determined using DSA studies as the gold standard. Radiation exposure related to DSA was calculated as total dose area product (TDAP) and effective dose.

RESULTS

Fifteen patients were included in this study (mean age 10 years, range 3–15 years). The mean time between the first surveillance DSA and Fe-MRI studies was 17 days (SD 47). Intermodality agreement was excellent between Fe-SPGR and DSA (κ = 1.00) but poor between ASL and DSA (κ = 0.53; 95% CI 0.18–0.89). The sensitivity and specificity for detecting residual AVMs using Fe-SPGR were 100% and 100%, and using ASL they were 72% and 100%, respectively. Radiologists reported overall high diagnostic confidence using Fe-SPGR. On average, patients received two surveillance DSA studies over the study period, which on average equated to a TDAP of 117.2 Gy×cm2 (95% CI 77.2–157.4 Gy×cm2) and an effective dose of 7.8 mSv (95% CI 4.4–8.8 mSv).

CONCLUSIONS

Fe-MRI performed similarly to DSA for the surveillance of residual AVMs. Future multicenter studies could further investigate the efficacy of Fe-MRI as a noninvasive alternative to DSA for monitoring AVMs in children.