84 / 264
of 1 year of follow-up (Fig. 2 and Table 1). Although not
statistically significant, there was a trend toward sac de-
compression providing the greatest hearing preservation
compared to all endolymphatic sac surgical procedures.
At short-term follow-up, sac decompression resulted in
only +1.3 dB PTA change, the smallest threshold increase
compared to other endolymphatic sac procedures (Table 2).
Shunting
Endolymphatic sac shunt procedures gained popularity
in the 1960s through House’s (15) subarachnoid shunting
procedure. Over the years, various shunting techniques
have emerged, including mastoid shunts, subarachnoid
shunts, and endolymphatic duct valve placement (11,12,
15,16,22,24,42,45,55,56,71). Each of these approaches
has generated controversy (12,24,72). Thomsen et al. (72)
were some of the first to question the efficacy of mastoid
shunts in their trial comparing mastoid shunt versus
‘‘sham procedure’’ (mastoidectomy). With nearly a de-
cade of follow-up, they concluded that there was no sta-
tistical difference between mastoid shunts and placebo
sham surgery in controlling vertiginous symptoms. Their
study, however, has received much criticism for its po-
tential inaccuracies and study design (73
Y
76).
Since House, many have performed a subarachnoid
shunt to treat medically recalcitrant MD, reporting com-
plete or substantial vertigo control (Category A/B) ranging
from 66% to 93% (11,13,20,22). Despite the early suc-
cesses of this technique, it has been rarely performed for
the last 25 years. In the 1970s, Arenberg offered another
shunting approach, the inner ear endolymphatic valve
(55,56,77). A unidirectional valve was placed directly into
the endolymphatic duct with the intent to promote endo-
lymph flow from the labyrinth to the sac. The inner ear
endolymphatic valve was discontinued because of ques-
tionable long-term vertigo control, with failures attributed
to fibroproliferative responses, valve migration, and valve
plugging (78). Because subarachnoid shunts and inner
endolymphatic duct valve placement techniques are rarely
performed today, we did not include these shunt pro-
cedures in our statistical comparison.
Current mastoid shunt procedures
V
mastoid shunt with
and without silastic
V
achieved 76.4% complete or sub-
stantial (Category A/B) vertigo control at a mean follow-up
of approximately 2.5 years (Fig. 4 and Table 1). With
similar mean follow-up, 71.4% of patients either improved
or maintained initial hearing, with a mean PTA worsening
of 7.2 dB (Fig. 5 and Table 2).
When comparing current procedures (sac decompres-
sion versus mastoid shunt
with
and
without
silastic), both
groups had similar rates of complete or substantial (Category
A/B) vertigo control (79.3% versus 76.4%,
p
= 0.34) at a
minimum of 1 year of follow-up (Table 1). Although both
groups maintained similar rates of stable or improved
hearing (72.8% versus 71.4%,
p
= 0.69), the notable dif-
ference was in mean change in PTA. Sac decompression
resulted in PTA worsening of 1.3 dB, whereas current
mastoid shunting techniques resulted in PTA worsening
of 7.2 dB (Table 2). The significance of this 6-dB differ-
ence could not be statistically calculated because raw data
were unavailable. Although the cause of worsened PTAs
observed with current shunting procedures in our analysis
is unknown, a few speculations may account for this dif-
ference. One speculation may be related to the added in-
vasiveness involved with incision of the endolymphatic
sac performed in shunting procures. Second, differences
in follow-up time may have contributed to this differ-
ence because current mastoid shunting techniques and
decompression patients were seen at an average of 34.8
and 25.8 months, respectively. One could argue that in-
creased time to follow-up may have resulted in worse
hearing PTAs with the progression of MD. In addition,
several studies have demonstrated worse hearing outcomes
with shunt procedures in comparison to the natural course
of MD (44,79). Overall, the 6-dB difference may not be
functionally relevant.
Mastoid Shunt With Silastic Versus Mastoid Shunt
Without Silastic
Groups undergoing mastoid shunting
with
and
without
silastic demonstrated nearly identical rates of complete or
substantial (Category A/B) vertigo control (76.9% versus
75.0%,
p
= 0.47) with a minimum of 1 year of follow-up,
comparable to the high efficacy rate seen in sac decom-
pression patients (Figs. 6 and 8). A difference between
the 2 groups, however, was noted with hearing out-
comes. The mastoid shunting with silastic group achieved
68.0% (mean follow-up, 32.5 mo) stable or improved
hearing, whereas the mastoid shunt without silastic group
achieved 72.5% (mean follow-up, 32.6 mo) (Figs. 7 and 9
and Table 2), a difference that was statistically significant
(
p
= 0.004). Although the etiology of this discrepancy is
unknown, some have suggested that the silastic sheeting
incites a foreign body reaction affecting inner ear func-
tion (78,80,81). The functional significance of this dif-
ference is uncertain. Interestingly, mastoid shunt without
silastic did not demonstrate a statistical difference in
short-term hearing preservation compared to simple sac
decompression (72.5% versus 72.8%,
p
= 0.99). Further,
although not statistically significant, sac decompression
preserved hearing in more patients than mastoid shunt
with
silastic in the short term (72.8% versus 68.0%,
p
= 0.18).
TABLE 5.
Summary of current ESS procedures from 6 studies with both short-term and long-term follow-up
Mean weighted
short-term follow-up (mo)
Category A/B vertigo
control (short term)
Mean weighted
long-term follow-up (mo)
Category A/B vertigo
control (long term)
Current ESS procedures
a
16.0
72.6%
b
79.0
63.4%
b
a
Current ESS procedures = sac decompression and mastoid shunts
with
and
without
silastic sheeting.
b
Short-term versus long-term follow-up Category A/B vertigo control;
p
= 0.004.
A. J. SOOD ET AL.
Otology & Neurotology, Vol. 35, No. 6, 2014
63