Role of Diffusion-Weighted MRI in Clival Chordoma

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Purpose: Chordoma is a rare notochordal tumor with a proclivity for the skull base and sacrococcygeal region. Poorly differentiated chordoma (PDC), as reported in the pediatric literature, displays more aggressive behavior compared with classic chordoma (CC). We investigated the role of diffusion-weighted imaging (DWI) MRI in evaluating these chordoma types.

Methods: Nine patients with clival chordoma (median age, 9.5 years; range, 22 months to 60 years) who had pretreatment DWI MRI (echo planar imaging technique, b = 1000 s/mm2, 3 directions) were retrospectively reviewed, after IRB approval. The apparent diffusion coefficient (ADC) of the solid portions of the tumor, exclusive of hemorrhage or cyst, was measured using the region of interest method. Immunohistochemical staining for nuclear Brachyury was performed to confirm chordoma diagnosis. Staining with SMARCB/INI-1 was performed to distinguish chordoma types. The ADC values of clival chondrosarcoma were assessed in two patients for comparison.

Results: All cases of PDC (n = 3) were seen in children. The diagnosis of CC (n = 6) was made in 4 adults and 2 children. There was a significant difference between ADC values of PDC (891 ± 127 mm2/s) and CC (1491 ± 167 mm2/s) (P = 0.001). Chondrosarcoma showed the highest ADC (1756 ± 47 mm2/s), but statistical significance was not assessed due to low sample size. Enhancement characteristics did not distinguish these tumor types.

Conclusions: Diffusion MRI may serve as a useful adjunct in assessing clival tumors, particularly in identifying poorly differentiated chordoma. A larger series incorporating diffusion MRI of clival tumors may further define its role in evaluating other tumors such as chondrosarcoma.



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