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Natural History of Cystic Vestibular Schwannomas.

OBJECTIVE
To determine the natural history of cystic vestibular schwannomas (VS).


STUDY DESIGN
Retrospective cohort.


SETTING
Single tertiary academic hospital.


PATIENTS
Adults diagnosed with cystic VS who had at least 2 MRIs performed at least 6 months apart between 2008 and 2016 with no intervening treatment.


MAIN OUTCOME MEASURES
Volumetric growth rates of both the entire tumor and individual cystic and solid components were measured. Linear growth rate of the entire tumor was assessed using the largest diameter parallel to the petrous face at the cerebellopontine angle (CPA).


RESULTS
Twenty-one patients met inclusion criteria. The average volumetric growth rate of the tumor was 1.1 ± 2 (range: -1.2 to 7.8), while the average growth rate of the cystic component was 0.8 ± 1.6 (range: -0.5 to 5.3) cm3/year. The CPA diameter of the tumor demonstrated an average linear growth rate of was 1.2 ± 4.4 (range: -8to 13.5) mm/year. With regards to tumor diameter, 9/21 (42.9%) remained stable, 3/21 (14.2%) decreased in size, while 9/21 (42.9%) increased in size.


CONCLUSIONS
Cystic tumors demonstrate a wide variability in growth rate. Larger, multi-center studies will be required to further compare this relationship to solid tumors.