Concordance of bilateral vestibular schwannoma growth and hearing changes in neurofibromatosis 2: neurofibromatosis 2 natural history consortium.

OBJECTIVE: To examine the relationship between the amount of change in size and associated hearing in bilateral vestibular schwannomas (VSs) in persons with neurofibromatosis 2 (NF2).

STUDY DESIGN: Annual magnetic resonance imaging and audiological examinations were conducted on NF2 patients.

SUBJECTS: Fifty-two patients enrolled in the NF2 Natural History Consortium in whom both VSs were untreated. Magnetic resonance imaging and hearing exams were available for at least 2 time points 1 year apart. The 32 males and 20 females had a mean age at diagnosis of 26 years (SD = 18). In 19 (37%) subjects, the NF2 germline mutation could not be identified in the blood (mosaic).

OUTCOME MEASURES: Greatest diameter change in tumor size for each of the 2 tumors from first to second evaluation was determined. Differences in amounts of change between the 2 sides and in hearing (4-frequency pure-tone average) were evaluated using multivariate analysis of variance.

RESULTS: Overall, the VSs demonstrated significant average growth (p < 0.001), and hearing worsened significantly (p < 0.001) over 1 year. The amount of change in the bigger tumors was not associated with the amount of change in the smaller tumors within each patient. Vestibular schwannoma size changes were not associated with the corresponding hearing changes (Kendall's tau, p = not significant [n.s.]).

CONCLUSION: A significant 1-year change in VS size and hearing occurred in NF2 patients. Clinically, tumor change or hearing deterioration on one VS cannot be used to predict changes in the other VS. This suggests that, although NF2 is a Mendelian disease, the germline genotype-phenotype relationship may resemble that of complex disorders.