How I do it: ultrasound-guided placement of ommaya reservoir in a patient with small ventricles and cavum septum pellucidum.

BACKGROUND Intraventricular chemotherapy via Ommaya reservoir is an important part of the treatment in patients with malignant central nervous system tumors. In these patients, catheter placement can be challenging due to the normal-sized ventricles. METHOD Intraoperative ultrasound guidance was used for Ommaya reservoir placement in a 56-year-old patient with multiple intracranial and leptomeningeal metastases who had cavum septum pellucidum et vergae malformation. The catheter was successfully placed into the frontal horn of the lateral ventricle outside the cavum. CONCLUSION Intraoperative ultrasound is a suitable image guidance system in patients with slit-like or normal-sized ventricles. It can also be used in patients with ventricular malformations.