Matthew M. Pearson

Activation of the Hedgehog pathway in pilocytic astrocytomas

Pilocytic astrocytoma is commonly viewed as a benign lesion. However, disease onset is most prevalent in the first two decades of life, and children are often left with residual or recurrent disease and significant morbidity. The Hedgehog (Hh) pathway regulates the growth of higher WHO grade gliomas, and in this study, we have evaluated the activation and operational status of this regulatory pathway in pilocytic astrocytomas. Expression levels of the Hh pathway transcriptional target PTCH were elevated in 45% of tumor specimens analyzed (ages 1–22 years) and correlated inversely with patient age. Evaluation of a tissue array revealed oligodendroglioma-like features, pilomyxoid features, infiltration, and necrosis more commonly in specimens from younger patients (below the median patient age of 10 years). Immunohistochemical staining for the Hh pathway components PTCH and GLI1 and the proliferation marker Ki67 demonstrated that patients diagnosed before the age of 10 had higher staining indices than those diagnosed after the age of 10. A significant correlation between Ki67 and PTCH and GLI1 staining indices was measured, and 86% of Ki67-positive cells also expressed PTCH. The operational status of the Hh pathway was confirmed in primary cell culture and could be modulated in a manner consistent with a ligand-dependent mechanism. Taken together, these findings suggest that Hh pathway activation is common in pediatric pilocytic astrocytomas and may be associated with younger age at diagnosis and tumor growth.

Active spontaneous decompression of a suprasellar-prepontine arachnoid cyst detected with routine magnetic resonance imaging. Case report.

Arachnoid cysts are congenital CSF collections that arise adjacent to arachnoid cisterns. These lesions can be incidental neuroimaging findings but may also cause symptoms and necessitate treatment, particularly in children. The authors present their experience with a male infant harboring a large suprasellar-prepontine arachnoid cyst who underwent spontaneous decompression into the ventricular system, as evidenced by a visualized CSF flow jet observed on routine MR imaging.

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 T2-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.

Pediatric posterior reversible encephalopathy syndrome presenting with isolated cerebellar edema and obstructive hydrocephalus

In this report, the authors describe the case of a teenage boy who presented with hypertensive emergency, posterior reversible encephalopathy syndrome, and hydrocephalus due to fourth ventricle outlet obstruction. Posterior reversible encephalopathy syndrome is a well-characterized but uncommon syndrome in children that is generally triggered by severe hypertension. The unusual clinical picture of this patient, who had isolated cerebellar edema leading to obstructive hydrocephalus, has been rarely described in children.

Endoscopic removal of an intraventricular primitive neuroectodermal tumor: retrieval of a free-floating fragment using a urological basket retriever.

The endoscopic resection of intraventricular tumors represents a unique challenge to the neurological surgeon. These neoplasms are invested deep within the brain parenchyma and are situated among neurologically vital structures. Additionally, the cerebrospinal fluid system presents a dynamic pathway for resected tumors to be mobilized and entrapped in other regions of the brain. In 2011, the authors treated a 3-year-old girl with a third ventricular mass identified on stereotactic brain biopsy as a WHO Grade IV CNS primitive neuroectodermal tumor. After successful neoadjuvant chemotherapy, endoscopic resection was performed. Despite successful resection of the tumor, the operation was complicated by mobilization of the resected tumor and entrapment in the atrial horn of the lateral ventricle. Using a urological stone basket retriever, the authors were able to retrieve the intact tumor without additional complications. The flexibility afforded by the nitinol urological stone basket was useful in the endoscopic removal of a free-floating intraventricular tumor. This device may prove to be useful for other practitioners performing these complicated intraventricular resections.

Intramedullary spinal immature teratoma: resolution of quadriplegia following resection in a 4-week-old infant

Intramedullary spinal cord teratomas are rare entities in infants. Management of these lesions is primarily surgical, with outcome dependent on rapid surgical decompression and complete gross-total tumor resection. The lesions are typically of the mature type, with immature teratomas displaying unique pathological features. The authors report a case of an extensive intramedullary immature teratoma in an infant with resolution of quadriplegia following gross-total radical resection. At the 1-year follow-up, there was radiographic evidence of tumor, and surgical reexploration yielded portions of immature teratoma and extensive gliosis.

Innovative application of cerebral RSO2 monitoring during shunt tap in pediatric ventricular malfunctioning shunts

Objective This study aimed to determine the reliability and potential application of cerebral regional tissue oxygenation (rSO2) monitoring in malfunctioning ventricular shunts during tap. Methods This is a prospective case series using convenience sample in subjects with confirmed malfunctioning shunt who had left and right cerebral rSO2 monitoring every 5 seconds before, during, and 1 hour after shunt tap. Results Ninety-four subjects had cerebral rSO2 monitoring. Sixty-three subjects had proximal malfunctions, and 31 subjects had distal shunt malfunctions. The intrasubject’s cerebral rSO2 trend and variability at pretap, during, and posttap times were highly correlated. Overall, the average rSO2 is lower in pretap as compared with posttap. Left cerebral rSO2 had lower means and larger SD as compared with right cerebral rSO2. Left pretap and posttap cerebral rSO2 variability was significantly associated with the location of shunt malfunction regardless of pretap, during, or posttap periods (P < 0.001), whereas right rSO2 variability was not predictive for malfunction location. Left cerebral rSO2 variability showed utility for identifying the location of malfunction with area under the receiver operating characteristic curve equal to 0.8. Conclusions Reliable cerebral rSO2 readings before, during, and after shunt tap were demonstrated. Left cerebral rSO2 changes from before to after shunt tap were more predictive for shunt malfunction location than right cerebral rSO2 changes. Observing cerebral rSO2 changes in relationship to shunt tap represents a potential surrogate in measuring cerebral pressures and blood flow changes after cerebral spinal fluid drainage. Significantly greater cerebral rSO2 changes occur for distal malfunction versus proximal malfunction after shunt tap, indicating its potential as an adjunct tool for detecting shunt malfunction type.