Objective To estimate the risk of loss of serviceable hearing during the co
nservative management of vestibular schwannomas.
Study Design: Retrospective case review.
Methods: Twenty-five patients with a radiological diagnosis of unilateral v
estibular schwannoma were managed conservatively for a mean duration of 43.
8 months (range, 12-194 mo). The pure-tone average (PTA) (0.5, 1, 2, and 3
kHz) and speech discrimination scores (SDS) were measured at regular interv
als throughout the entire duration of follow-up. Serviceable hearing was de
fined using two criteria: 70% SDS/30 dB PTA (the 70/30 rule) and 50% SDS/50
dB PTA (the 50/50 rule). The size and growth rate of tumors were determine
d according to the American Academy of Otolaryngology--Head and Neck Surger
y guidelines (1995). Intervention was recommended if there was evidence of
continuous or rapid radiological tumor growth, and/or increasing symptoms o
r signs suggestive of tumor growth,
Results: The risk of loss of serviceable hearing for the total group was 43
% using the 70/30 rule and 42% using the 50/50 rule. Tumor growth was consi
dered significant (> 1 mm) in 8 tumors (32%) and nonsignificant in 17 (68%)
. The risk of loss of serviceable hearing for the tumor-growth group was 67
% using the 70/30 rule and 80% using the 50/50 pule. In contrast, the risk
of loss of serviceable hearing for the no tumor-growth group was 25% using
the 70/30 rule and 14% using the 50/50 rule. No audiological factors predic
tive of tumor growth were identified.
Conclusions: There is a significant risk of loss of serviceable hearing dur
ing the conservative management of vestibular schwannomas. This risk appear
s to be greater in tumors that demonstrate significant growth.