Faculty Bibliography

BACKGROUND: Hydrocephalus in patients with neurofibromatosis type I (NF1) is usually obstructive, and may arise secondary to tumoral or non-tumoral causes. The treatment of hydrocephalus in these patients is often challenging due to combined pathologies and unique anatomical changes. The use of endoscopic third ventriculostomy (ETV) as treatment has rarely been described in this group. In this study we aimed to characterize the indications, considerations and outcome of ETV in patients with NF1 gathered in a multicenter international cohort. METHODS: Five centers participated in this retrospective study. Following an IRB approval, data and images were collected. Inclusion criteria were patients of all ages with NF1 who underwent an ETV for the treatment of obstructive hydrocephalus. Exclusion criteria were patients who had no post-operative radiological or clinical follow up. ETV failure was defined as recurrent clinical or radiological signs of hydrocephalus. RESULTS: Forty-two patients were included in this study. Common etiologies for hydrocephalus were aqueductal/tectal tumor (31%), aqueductal web (26%), and aqueductal stenosis due to neurofibromatosis related changes (14%). Ten patients had a preoperative diagnosis of optic pathway glioma. Six patients were defined as ETV failure within 1 month, 3 more within 9 months and 1 more within 4 years. ETV was defined as successful in 32 patients (76%) with a mean follow up of 59.4 +/- 50.9 months (4 months - 15 years). CONCLUSION: ETV is a safe treatment for selected patients with NF1 and obstructive hydrocephalus. Individual anatomical and pathological aspects should be taken into consideration.

Optic gliomas are brain tumors characterized by slow growth, progressive loss of vision, and limited therapeutic options. Optic gliomas contain various amounts of myxoid matrix, which can represent most of the tumor mass. We sought to investigate biological function and protein structure of the myxoid matrix in optic gliomas to identify novel therapeutic targets. We reviewed histological features and clinical imaging properties, analyzed vasculature by immunohistochemistry and electron microscopy, and performed liquid chromatography-mass spectrometry on optic gliomas, which varied in the amount of myxoid matrix. We found that although subtypes of optic gliomas are indistinguishable on imaging, the microvascular network of pilomyxoid astrocytoma, a subtype of optic glioma with abundant myxoid matrix, is characterized by the presence of endothelium-free channels in the myxoid matrix. These tumors show normal perfusion by clinical imaging and lack histological evidence of hemorrhage organization or thrombosis. The myxoid matrix is composed predominantly of the proteoglycan versican and its linking protein, a vertebrate hyaluronan and proteoglycan link protein 1. We propose that pediatric optic gliomas can maintain blood supply without endothelial cells by using invertebrate-like channels, which we termed primitive myxoid vascularization. Enzymatic targeting of the proteoglycan versican/hyaluronan and proteoglycan link protein 1 rich myxoid matrix, which is in direct contact with circulating blood, can provide novel therapeutic avenues for optic gliomas of childhood.

INTRODUCTION: Optic gliomas are classified as pilocytic astrocytoma (PA) or pilomyxoid astrocytoma (PMXA). Abundant bluish chondroid myxoid matrix is characteristic of PMXA but not PA. We sought to investigate the molecular composition of myxoid matrix and its biologic role in angiogenesis of optic gliomas. We reviewed clinical and pathological data on a cohort of 120 patients with optic glioma diagnosed at NYU Langone Medical Center from 1996 to 2014. We analyzed microvascular density (MVD), perfusion, hypoxia and proliferation by immunohistochemistry and ultrastructural features by electron microscopy. To identify the composition of the myxoid matrix in PMXA we performed liquid chromatography-mass spectrometry (LC-MS) without sample fractionation quantified using peptide spectral counts. PMXA showed significantly lower MVD by CD34 (8.1 vs 14.5, p-value < 0.002) and Erg (7 vs. 13.6, p-value 0.003) than PA, however GLUT-1 showed equal perfusion. Electron microscopy showed that PMXA contain both regular blood vessels with endothelial lining and channels completely lacking endothelial and smooth muscle cells. LC-MS stratified optic gliomas into three distinct groups. We identified 5389 proteins of which 188 were differentially expressed in the three groups (p<0.05, Benjamini-Hochberg adjustment). Between PA and PMXA, we found that most of differentially expressed proteins (146/188) displayed a positive fold change (increasing in PMXA relative to PA), and a minority (42/188) showed a negative fold change. The most abundant extracellular matrix proteins were a chondroitin sulfate proteoglycan versican (VCAN 3.7-fold increase Q=0.000463) and its paralog vertebrate Hyaluronan And Proteoglycan Link Protein 1 (HAPLN1, 22-fold increase from the PA to the PMXA group Q=4.60x10-7). Optic gliomas can develop endothelium-independent channels reminiscent of those in invertebrates to maintain blood supply. The myxoid matrix is composed of VCAN and its linking paralog HAPLN1. Targeting the myxoid matrix may provide novel avenues for therapy of optic gliom