Long-term MRI surveillance after microsurgery for vestibular schwannoma.

OBJECTIVES: To determine the optimal postoperative magnetic resonance imaging (MRI) schedule and length of follow-up for patients undergoing microsurgical excision of vestibular schwannoma (VS).

STUDY DESIGN: A retrospective review of patients who underwent microsurgical excision of VS at a single tertiary care center between January 1993 and March 2004.

METHODS: Two hundred and twenty subjects were analyzed and characteristics gathered, including tumor size, surgical approach, completeness of resection, and length of follow-up to last MRI. All postoperative MRIs were reviewed. Radiologic progression is defined as a transition to a more advanced MRI grade from a less advanced MRI grade (eg, clean, linear, nodular) and was recorded for each of the subjects' serial MRIs. The MRI categorized findings were also binned into five time periods for summary analyses. Interval-censored survival analysis was performed to model time to recurrence across the population.

RESULTS: Of the non-neurofibromatosis type 2 (NF2) cohort, the average tumor size at the time of resection was 1.98 ± 1.02 cm (range 0.4-5 cm); average length of follow-up was 9.0 ± 4.6 years (range 1-19); 102 subjects (47.2%) underwent a retrosigmoid resection; and 110 (50.9%) underwent a translabyrinthine resection. Eight of these subjects (4.1%) demonstrated radiologic progression; of those, four underwent additional treatment. Survival analysis showed early (1-2 years postoperative), middle (2-10 years postoperative), and late (> 10 years postoperative) radiologic progression events.

CONCLUSION: The current recommended MRI surveillance schedule after microsurgery for VS includes MRIs at 1, 5, and 10 years postoperatively. Nonparametric survival analysis suggests that a majority of radiologic progression events occur in the first 10 years postoperatively.

LEVEL OF EVIDENCE: 4. Laryngoscope, 127:2132-2138, 2017.