The vestibular schwannoma surgery learning curve mapped by the cumulative summation test for learning curve

Objective: To demonstrate and quantify the learning curve for microsurgical excision of vestibular schwannoma in a newly formed neurootologic team by using the cumulative summation test for learning curve (LC-CUSUM). To secondarily identify the factors influencing postoperative facial nerve outcome.

Study Design: Retrospective review.

Setting: Tertiary referral center.

Patients: Between 1999 and 2011, 153 consecutive cases of vestibular schwannoma excision.

Intervention: One-hundred and fifty-three patients underwent excision of vestibular schwannoma.

Main Outcome Measures: Facial nerve outcomes were assessed using the House-Brackmann (HB) facial nerve grading system. Postoperative facial nerve outcomes at 12 months were analyzed using the LC-CUSUM method with HB Grades I to III being defined as successful outcomes. The factors that influence postoperative facial nerve outcome were analyzed.

Results: The constructed learning curve shows a gradual improvement in facial nerve outcomes. The learning curve crossed the derived LC-CUSUM barrier at the 56th procedure, indicating that sufficient evidence had accumulated to demonstrate that the surgeon had achieved optimal outcomes at this point. Tumor size (p = 0.008) and surgical approach (p = 0.005) were 2 additional significant factors influencing postoperative facial nerve outcome.

Conclusion: The learning curve is evident in this series of microsurgical excisions of vestibular schwannoma. A newly formed team needs to perform at least 56 cases to gain sufficient experience to accomplish optimal results. Position along the learning curve, tumor size, and familiarity with a preferred surgical approach are the factors, which dominated facial nerve outcome. We recommend the use of LC-CUSUM test for learning curve analysis.