11beta-Hydroxysteroid dehydrogenase type 2 is a glucocorticoid metabolizing enzyme that catalyzes rapid inactivation of corticosterone and cortisol to inert 11-keto derivatives. As 11beta-hydroxysteroid dehydrogenase type 2 is highly expressed in the developing brain, but not in the adult CNS, we hypothesized that it may represent a protective barrier to the deleterious actions of corticosteroids on proliferating cells. To test this hypothesis we have investigated the development and growth of the cerebellum in neonatal C57BL/6 mice and mice lacking 11beta-hydroxysteroid dehydrogenase type 2 (-/-). 11beta-Hydroxysteroid dehydrogenase type 2-/- mice had consistently lower body weight throughout the neonatal period, coupled with a smaller brain size although this was normalized when corrected for body weight. The cerebellar size was smaller in 11beta-hydroxysteroid dehydrogenase type 2-/- mice, due to decreases in size of both the molecular and internal granule layers. When exogenous corticosterone was administered to the pups between postnatal days 4 and 13, 11beta-hydroxysteroid dehydrogenase type 2(-/-) mice were more sensitive, showing further inhibition of cerebellar growth while the wildtype mice were not affected. Upon withdrawal of exogenous steroid, there was a rebound growth spurt so that at day 21 postnatally, the cerebellar size in 11beta-hydroxysteroid dehydrogenase type 2-/- mice was similar to untreated mice of the same genotype. Furthermore, 11beta-hydroxysteroid dehydrogenase type 2-/- mice had a delay in the attainment of neurodevelopmental landmarks such as negative geotaxis and eye opening. We therefore suggest that 11beta-hydroxysteroid dehydrogenase type 2 acts as to protect the developing nervous system from the deleterious consequences of glucocorticoid overexposure.

Object Image-guided neuroendoscopy is being increasingly used in an attempt to reduce the morbidity associated with surgery and to make navigation easier. It has a particularly useful application in the pediatric population for the treatment of conditions such as complex hydrocephalus and arachnoid cysts. However, its use has been limited by the requirement for rigid head fixation, which may be difficult in infants because of the immaturity of the skull. In addition there can be line-of-sight issues, which can be a problem with optical-based systems. Electromagnetic navigation has eliminated the requirement for head immobilization, and its successful use in the infant population has been reported. The authors present their series to date, define its role, and discuss its advantages over other forms of image-guided navigation. Methods The authors used the electromagnetic StealthStation and software (Medtronic) for neuronavigation. A dynamic reference frame was attached to the head using an adhesive dressing. The patient was positioned without rigid fixation and was registered using a specially designed stylet. Navigation was through a stylet, which could be placed within the endoscope. Direct advantages were no rigid head fixation, the ability to maneuver the endoscope without the requirement for a bulky optical attachment, and no loss of navigation caused by user obstruction of reflective fiducial markers. The authors performed a total of 28 procedures in 23 patients. There were 9 arachnoid cyst marsupializations, 4 multiple fenestrations for multiloculated hydrocephalus, 4 aqueductal stenting procedures for encysted fourth ventricles, 5 endoscopic third ventriculostomies, 3 septum pellucidotomies, 2 tumor biopsies, and 1 tumor cyst decompression. Results Electromagnetic navigation was successful in all cases. Two complications were reported: a subdural collection, requiring bur hole drainage after a successful fenestration of the arachnoid cyst and failed treatment of complex hydrocephalus requiring subsequent placement of a ventriculoperitoneal shunt. Conclusions The electromagnetic technology provides reliable image-guided endoscopy. It has several advantages over alternative forms of stereotaxy, and the ability to use it without the need for rigid head fixation makes it eminently suitable for the pediatric population. Its use and application in the treatment of a variety of different conditions has been demonstrated successfully.

Object The aim of this study was to prospectively evaluate the use of noninvasive electromagnetic neuronavigation in children, in particular its use in complex hydrocephalus and slit ventricle syndrome. Methods Prospective data was collected from all pediatric patients undergoing insertion of ventriculoperitoneal shunts using electromagnetic frameless neuronavigation from January 2006 to November 2007. Results Twenty-three patients fulfilled the study criteria. All ventricles were cannulated on the first pass. There were no immediate or early postprocedural complications. All but 1 patient had resolution of symptoms (mainly chronic headache) on follow-up (median 7 months, range 1–17 months). The proximal revision rate was 9% (2 of 23 patients). One patient required distal catheter revision. Infection occurred in 1 patient. Conclusions Electromagnetic neuronavigation using a frameless and pinless system is especially suited for pediatric patients. The authors hypothesize that successful placement of ventricular catheters will reduce morbidity and improve shunt longevity.

The presence of acute jugular venous occlusion as a cause of perimesencephalic nonaneurysmal subarachnoid hemorrhage supports a venous origin of hemorrhage.

Survival following recurrence is poor and those prognostic factors that predispose to recurrence include extent of surgical resection and the timing of administration of adjuvant therapy. The extent of resection at re-operation can confer a survival advantage, without a necessary increase in morbidity. Strategies aimed at improving surgical resection at first diagnosis include improving and centralising post-surgical radiological review, defining what are true residuals, and centralising surgical review of incompletely resected tumours. Re-irradiation can improve survival, and with the use of conformal radiation fields need not necessarily lead to neuropsychological damage. Cisplatin and etoposide remain the most effective chemotherapeutic agents to date and with an increase in the understanding of tumour biology this may improve further. Because of the complex nature of this group of patients, decisions regarding their management require the involvement of a paediatric neurosurgeon, paediatric neuro-oncologist and paediatric radiation oncologist.