After adequate preparation, patient in prone position, and incision made via the midline posteriorly, a foramina magnum identified and a resection of of of the posterior aspect of C1 done. Dura exposed : massive posterior fossa adhesion identified and released, 
Mobilization done with exposure of the sub-arachnoid space, Clear CSF noted under a moderate pressure. The valve and the shunt and the ventricular catheter mobilized with subsquent connection. 
wound closed in layers, 
immediate post operation period satisfactory. 