Interactive image-guided transcallosal microsurgery for anterior third ventricular cysts

Although the treatment of colloid cysts remains controversial, high viscosi ty and small volume are poor prognostic indicators for successful burr hole aspiration and cortical incision via craniotomy may be associated with pos toperative epilepsy. The anterior transcallosal approach provides a direct and adequate pathway to the lateral ventricles, where the foramen of Monro serves as a natural entrance into the anterior third ventricle, especially when the foramen is dilated by a lesion. When the midsuperior portion of th e IIIrd ventricle cannot be reached, the interforniceal or the subchoroidal exposures have been advocated. Stereotactic techniques contribute to a min imal invasive approach and reduce morbidity. Nine patients harbouring anter ior third ventricular cysts (seven colloids and two intrinsic craniopharyng iomas) underwent anterior transcallosal microsurgical excision assisted by an interactive infrared-based image guided system (EasyGuide, Neuro, Philip s). There were 4 men and 5 women ranging in age from 15 to 42 years (mean 2 8.5). Transcallosal transforaminal (5 cases) or interforniceal (4 cases) ap proaches allowed total excision in eight patients and subtotal in one. Post operative morbidity included a case of transient hemiparesis and a case of transient short-term memory disturbances; both resolved in the first months . Mortality was zero. Particular advantages of the method were accurate tra jectory and position of callosotomy incision determination, visualisation a nd avoidance of superior saggital sinus, retraction of bridging veins and t he often variable pericallosal arteries, spatial orientation within the ven tricular system, and identification of the periventricular anatomical struc tures.