E1855. Clival Chordoma: What Radiologists Need to Know
  1. Saif Baig; Nassau University Medical Center
  2. Adam Holtzman; UF Health Jacksonville Department of Radiation Oncology
  3. Michael Rutenberg; UF Health Jacksonville Department of Radiation Oncology
  4. Peter Fiester; UF Health Jacksonville Department of Radiology
  5. Dinesh Rao; UF Health Jacksonville Department of Radiology
Chordomas are rare, typically indolent tumors arising from embryonic remnants of the primitive notochord. Skull base forms are slow-growing tumors most commonly originating along the clivus, locally extending into adjacent structures. Radiologists play an important role in diagnosis, treatment planning and follow-up, providing valuable information to surgeons and radiation oncologists for pre-operative planning, identification of post-treatment changes and disease recurrence. This educational review provides an overview of clinical characteristics, surgical anatomy, identification of treatment complications, and patterns of disease recurrence for radiologists to provide value in the management of these lesions.

Educational Goals / Teaching Points
1. Review of imaging characteristics on CT and MRI for skull base chordomas. 2. Emphasize how imaging influences the management of patients with skull base chordoma. 3. Review skull base anatomy with regard to tumor location and surgical planning and approaches. 4. Review the current treatment paradigms for post operative radiotherapy and complications.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Both computed tomography (CT) and magnetic resonance imaging (MRI) are required for accurate characterization of clival chordomas and their relationship to adjacent anatomy. MRI is used in diagnosis treatment planning of intracranial chordomas due to its ability to discriminate between and adjacent normal anatomical structures. Classic and chondroid skull base chordomas demonstrate hyperintense signal on T2-weighted sequences along with heterogenous hypotense foci. T2-weighted sequences are superior in differentiating adjacent neural structures from abutting tumors. In contrast, poorly differentiated chordoma demonstrates mainly T2-weighted hypointense signal. On T1-weighted sequences, chordomas classically demonstrate intermediate to low signal intensity with small hyperintense foci representing mucus or hemorrhage. Classic and chondroid chordomas will display a honeycombed enhancement with lines of non-enhancement on contrast-enhanced on T1-weighted sequences. Contrast-enhancement and tumor resolution further improves with the addition of fat suppression. CT is superior to MRI in evaluating for internal matrix and osseous involvement.

Skull base chordomas are locally aggressive, slow-growing malignant tumors with high rates of recurrence. A combination of CT and MR information are required to characterize tumor extension and its relationship to surrounding neuroanatomy. Recognizing image findings of common late radiation treatment effects such as brainstem and temporal lobe necrosis, optic and cranial neuropathies, and cervical myelopathy is important as presenting symptoms may not be conclusive based on clinical history or physical exam alone. Radiologists have a central role in characterizing initial disease, post-surgical anatomy and residual disease, radiation treatment planning, identifying disease recurrence and late treatment effects.