Pseudomonoventricle due to a malformation of the septum pellucidum.

Three children with complete absence of the frontal horns of the lateral ventricles and a single midline cavity on CT scan are reported. Two patients presented with adipsia, persistent serum hyperosmolarity and partial central diabetes insipidus. Another presented with congenital hemiplegia. The CT appearance was different from that of the known causes of monoventricle and was attributable to a malformation of the septum pellucidum, first described neuropathologically by Gross and Kaltenbäck (1957) who termed it frontal pseudomonoventricle.