The Added Value of Diffusion Magnetic Resonance Imaging in the Diagnosis and Posttreatment Evaluation of Skull Base Chordomas.

To determine the use of diffusion-weighted imaging (DWI) in the pre- and posttreatment evaluation of skull base chordomas.  Retrospective study.  Tertiary care university hospital.  In total, 17 patients with histopathological diagnosis of chordoma who had magnetic resonance (MR) imaging and DWI were evaluated. Of them, 13 patients had posttreatment MR imaging including DWI.  Three apparent diffusion coefficient (ADC) values were obtained from tumor, and an ADC value was measured from pons for the purpose of normalization. ADC values of the subtypes of chordomas (typical and chondroid chordomas) were compared.  Ten (59%) masses had increased signal on trace DWI at pretreatment evaluation. The mean ADC /ADC was calculated as 1.55 ± 0.44. The mean ADC values of typical and chondroid chordomas were 1.26 ± 0.29 × 10 mm /s and 0.99 ± 0.46 × 10 mm /s, respectively. There was no statistically significant difference between ADC values of the subtypes ( > 0.05). For posttreatment evaluation, DWI enabled detection of residual tumor in the majority (85%) of cases.  DWI is useful in diagnosis and posttreatment evaluation of skull base chordomas. However, ADC values in our series did not distinguish the subtypes of chordomas.