MRI signal changes in the skull base bone after endoscopic nasopharyngectomy for recurrent nasopharyngeal carcinoma

Objective: To evaluate the signal changes of the skull base after salvage surgery via endoscopic transnasal approach for local recurrent nasopharyngeal carcinoma Methods: Twenty patients with nasopharyngeal carcinoma after radiation failure underwent nasophargeryngectomy via an endoscopic transnasal approach were selected from April 2006 to December 2011, including 16 males and 4 females with 31 to 67 years old. Each patient had previously received irradiation and experienced recurrence after 8 to 83 months of completed irradiation. All patients underwent MRI no more than 2 weeks before the salvage surgery and were subjected to repeat MRI scans 2 weeks, 3 months, 6 months later and semi-annually thereafter, with the follow-up time of 6 to 45 months (median 18 months). A two-sided Chi-square test was used to compare the signal changes and the tendency of changes on all presurgical and postsurgical MR images. Results: The MRI signal changes were detected at 92 sites of skull-base between 2 weeks and 3 months after the surgery, which was hypointense on T₁WI with moderate to marked contrast enhancement. In the follow-up period, the signal abnormalities at 36 sites of skull base had resolved or restored to the normal, and 34 sites remained stable, while in 22 sites, the MR signal changes became more obvious. The skull base bones adjacent to the region of the resection were more likely to show signal changes than nonadjacent areas (72 vs. 20, χ² = 33.128, P < 0.01). The signal changes were more common on the ipsilateral skull base to the recurrent tumor in contrast to the contralateral skull base (68 vs 24, χ² = 21.182, P < 0.01). Conclusions: The skull base signal changes after salvage surgery via endoscopic transnasal approach for local recurrent nasopharyngeal carcinoma, and it occurs in specific location. Most of sites tend to resolve or be stable at the follow up. (authors)