Chordoma (Clival Chordoma): a locally invasive skull base tumor that arises from remnants of the primitive notochord. Chordomas are often considered a benign tumor because of their slow growth rate. However, some chordomas behave aggressively and have more malignant characteristics with extensive invasiveness including a small subset of patients (~10%) that develop metastases to distant sites beyond their site of origin. As they expand, clival chordomas can cause headaches, double vision as well as hearing loss, difficulty swallowing, facial numbness, incoordination, motor weakness, and memory disturbance. These relatively rare tumors are diagnosed by MRI and CT scans. Initial treatment is usually with surgical debulking, most often by an endonasal transsphenoidal approach. Because chordomas often invade the bone and dura of the skull base, complete surgical resection is often not possible and continued growth of residual tumor is common. Most recurrent or residual tumors are best treated with stereotactic radiotherapy (SRT), stereotactic radiosurgery (SRS) or proton beam radiation. Learn more.