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OBJECT - Endoscopic third ventriculostomy (ETV) is an alternative to shunt placement in children with hydrocephalus due to tectal plate gliomas (TPGs). However, controversy remains regarding the amount of ventricular size reduction that should be expected after ETV. This study investigates ventricular size change after ETV for TPGs.
METHODS - Twenty-two children were identified from a 15-year retrospective database of neuroendoscopic procedures performed at the authors' institution, Children's Hospital of Alabama, in patients with a minimum of 1 year of follow-up. Clinical outcomes, including the need for further CSF diversion and symptom resolution, were recorded. The frontal and occipital horn ratio (FOR) was measured on pre- and postoperative, 1-year, and last follow-up imaging studies.
RESULTS - In 17 (77%) of 22 children no additional procedure for CSF diversion was required. Of those in whom CSF diversion failed, 4 underwent successful repeat ETV and 1 required shunt replacement. Therefore, in 21 (96%) of 22 patients, CSF diversion was accomplished with ETV. Preoperative and postoperative imaging was available for 18 (82%) of 22 patients. The FOR decreased in 89% of children who underwent ETV. The FOR progressively decreased 1.7%, 11.2%, and 12.7% on the initial postoperative, 1-year, and last follow-up images, respectively. The mean radiological follow-up duration for 18 patients was 5.4 years. When ETV failed, the FOR increased at the time of failure in all patients. Failure occurred 1.6 years after initial ETV on average. The mean clinical follow-up period for all 22 patients was 5.3 years. In all cases clinical improvement was demonstrated at the last follow-up.
CONCLUSIONS - Endoscopic third ventriculostomy successfully treated hydrocephalus in the extended follow-up period of patients with TPGs. The most significant reduction in ventricular size was observed at the the 1-year followup, with only modest reduction thereafter.

INSM1/IA-1 (insulinoma-associated 1) is a developmentally regulated zinc-finger transcription factor, exclusively expressed in the foetal pancreas and nervous system, and in tumours of neuroendocrine origin. We have identified an INSM1 binding site in the neuroD/beta2 promoter and demonstrated transcriptional repressor activity of INSM1 by transient transfection assay. A chromatin immunoprecipitation assay confirmed that in vivo INSM1 is situated on the promoter region of the neuroD/beta2 gene. In an attempt to elucidate the molecular mechanism of transcriptional repression by the INSM1 gene, cyclin D1 was identified as an interacting protein by using a 45-day-old human foetal brain cDNA library and a yeast two-hybrid screen. The physical association between INSM1 and cyclin D1 was confirmed by in vitro and in vivo pull-down assay. Cyclin D1 co-operates with INSM1 and suppresses neuroD/beta2 promoter activity. Co-immunoprecipitation of INSM1, cyclin D1 and HDACs (histone deacetylases) in mammalian cells revealed that INSM1 interacts with HDAC-1 and -3 and that this interaction is mediated through cyclin D1. Overexpression of cyclin D1 and HDAC-3 significantly enhanced the transcriptional repression activity of INSM1 on the neuroD/beta2 promoter. A further chromatin immunoprecipitation assay confirmed that HDAC-3 occupies this same region of the neuroD/beta2 promoter, by forming a transcription complex with INSM1. Thus we conclude that INSM1 recruits cyclin D1 and HDACs, which confer transcriptional repressor activity.