Modified far lateral approach for a 4th ventricular tumor with CPA extension: Illustrative teaching case.

A 56-year old female presented with several months of nausea, imbalance, and gait instability. Imaging demonstrated a 4^th ventricular lesion extending toward the left cerebello-pontine angle (CPA). Here we describe how a modified far lateral approach with C1 laminectomy is an alternative approach to such a lesion, providing circumferential visualization for resection. IRB approval was not needed due to descriptive approach, and the patient consented to research. The patient was positioned 3/4 prone with left side up, and an incision was made to expose the mastoid, occipital bone, C1, and C2. After the corresponding myocutaneous flap was raised, the vertebral artery was identified with Doppler, and a left far lateral craniotomy spanning from right of midline to the left sigmoid sinus was created. Additionally, we completed a left C1 laminectomy and drilled bone along the lateral foramen magnum up to the condyle without condylectomy. The dura was opened with exposure of the obex to the left CPA. The intertonsillar and left vermus-tonsillar planes were dissected to identify the lesion, overlying PICA was released from the lesion, and the left tonsil was elevated for tumor exposure. The tumor was then debulked superficial-to-deep, followed by lateral-to-medial, prior to closing. A gross total resection was achieved without surgical complications. At two-week follow-up, the patient was ambulating with a walker, incisional pain was improving, and nausea was resolved. A modified far lateral approach provides an alternative to midline suboccipital and retrosigmoid craniotomies for 4^th ventricular tumors that extend laterally towards the CPA.