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A. J. SOOD ET AL.

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

72.6% b

63.4% b

16.0

79.0

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/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. 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). Mastoid Shunt With Silastic Versus Mastoid Shunt Without Silastic

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

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