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resection, although follow-up in all these series is lim-
ited. Together, these data demonstrate that in many
cases incomplete tumor resection is required in order to
preserve facial nerve integrity, and that more aggressive
resection is associated with poorer postoperative facial
nerve function.
In a previous study, the authors found that at 3, 5,
and 10 years following SRS for treatment of sporadic VS,
45%, 52%, and 77% of patients developed nonserviceable
hearing, respectively. 16 In the current study, 15 of 17
(88%) patients with serviceable hearing prior to SRS lost
useful hearing at a median of 40 months following treat-
ment, which is even greater than prior estimates.16–19 The
higher percentage of cases that lost serviceable hearing
following radiation in the current study is most likely
attributable to the added effects of tumor growth.16–20 The
small number of patients with preoperative serviceable
hearing in our study precluded analysis of hearing preser-
vation surgery after failed radiation therapy; however,
this would seem like an unrealistic goal in most cases.8
The merit of gross total tumor resection in the set-
ting of recurrent VS has been a subject of ongoing
debate.6,8 Our data suggest that gross total tumor resec-
tion is less frequently achievable in previously radiated
tumors compared to nonradiated controls. We acknowl-
edge that our GTR rate of 49% seems low for the
patients presented here. However, we want to emphasize
that we are very stringent about not considering NTR in
which there is no residual tumor visible on the 3-month
follow-up MRI as a complete resection. If we were to
include NTR and GTR together, the rate would be 76%.
Irradiation inevitably delivers a minimum of the pre-
scribed marginal dose to the facial nerve–tumor plane,
leading to formation of adhesions and poor surgical
planes. As a general strategy, our group enters surgical
salvage cases with the intent to remove the tumor in its
entirety; however, we utilize intraoperative impression
and results of intraoperative electroprognostic testing to
assist in determining when less-than-complete resection
should be performed in order to preserve facial nerve
integrity.14 The limited cumulative data suggest that
short- and intermediate-term tumor control is good even
following subtotal resection. Long-term data will be
required to ascertain the risk of delayed recurrence.
Theoretically, reirradiation carries an increased risk
of cranial neuropathy, hydrocephalus, and radiation-
induced cerebral edema or necrosis. Furthermore, tumors
that initially fail radiation therapy may be considered
more radioresistant and less likely to respond to addi-
tional radiation treatment. Despite these considerations,
preliminary data suggest that retreatment with low-dose
SRS is well tolerated and provides tumor control in the
majority of cases.21–23 Until more data are available docu-
menting the long-term safety and efficacy of this strategy,
the authors favor microsurgical salvage in most cases.
With the increasing number of VS cases worldwide
receiving primary radiation therapy, and the ongoing
trend toward dose deescalation to limit treatment mor-
bidity, our ability to manage radiation failure is becoming
increasingly relevant.3 In the authors’ experience,
approximately 6% of patients who receive primary SRS
experience treatment failure at 5 to 7 years following
radiation.12,24 This number may be greater for cystic,
large, or rapidly growing tumors—or in cases where less
than 12 Gy to the tumor margin is prescribed. 2,25–27
Data regarding the utility of radiation therapy for treat-
ment of residual progressive disease following subtotal
resection is mixed. Several studies have demonstrated
that the results following subtotal resection are on par
with primary radiation treatment. 28,29 However, in a
recent preliminary report of a large prospective multicen-
ter study, Monfared et al. found that four of 11 (36%)
cases failed salvage radiation therapy, leading to the con-
clusion that radiation control of growing tumor remnants
following microsurgery is suboptimal. 30
Our study has several strengths and limitations. We
included a relatively large and homogenous cohort of spo-
radic VS and excluded patients with NF2 given the signifi-
cant difference in tumor biology and behavior. Control
subjects, matched by age, tumor size, and center, were
included for comparison. Additionally, patients were
included from two separate institutions on separate conti-
nents to try and reduce surgeon specific biases. Finally,
both institutions have a strong track record of utilizing SRS
and microsurgery in the management of VS. Limitations
include retrospective review of data, which carries a risk of
selection bias, heterogeneous and incomplete data points,
and inconsistent follow-up. When previous SRS has failed,
much longer follow-up is necessary to truly determine the
fate of tumor remnants following less than GTR.
CONCLUSION
Microsurgical resection of VS following SRS is tech-
nically challenging. Nevertheless, facial nerve preserva-
tion with effective tumor control remains an attainable
goal in most patients. Intraoperative surgical judgment
about when to perform less than GTR and how to maxi-
mize tumor removal in such cases remains extremely
important and is very difficult to objectify.
Acknowledgment
The authors would like to thank Amy E. Glasgow, MHA,
for her valuable assistance with statistical analysis.
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