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  • Seven-Year Update of Multi-Center Prospective Study of Large Vestibular Schwannomas: Acoustic Neuroma Subtotal Resection Study (A.N.S.R.S)

    Final Number:

    A. Monfared; E. Corrales; P. Theodosopoulos; N. Blevins; J. Oghali; S. Selesnick; H. Lee; R. Gurgel; M. Hansen; R. Nelson; B. Gantz; W. Kutz; B. Isaacson; P. Roland; R. Amdur; R. Jackler

    Study Design:
    Clinical Trial

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2014 Annual Meeting

    Introduction: Patients with large acoustic neuromas are at high risk of poor facial nerve (CNVII) function following surgery. Subtotal resection has the potential for better facial nerve outcome but higher tumor recurrence.

    Methods: Patients with acoustic neuromas = 2.5 cm underwent gross total (GTR), near total (NTR) with remnant tumor no larger than 0.5cm3 on postoperative MRI or 2x2x5mm residual in surgery, or subtotal (STR) resection defined as any larger remnant. Patients received stereotactic radiation if tumor remnant grew.

    Results: Of 132 enrolled patients, 73 had at least 1-year follow up (mean 38 months). Average age was 48.7 years, mean tumor diameter was 3.33cm, and 34% were cystic. As defined by postoperative MRI 12 had GTR, 22 NTR, and 39 STR. There were 14(21%) recurrences, 1(8%) in GTR, 2(9%) in NTR, and 11(28%) in STR groups with average of 35 months to recurrence (4-74mo). The recurrences were treated with SRT in 11 cases, IMRT in 1 case, and surgery in 2 cases due to size and cystic nature of recurrence. Four of post-radiation remnants (33%) continued to grow and required surgical salvage. Tumor recurrence was related to longer followup, non-cystic tumor, larger residual tumor, and STR resection. Good facial nerve function (House-Brackmann I and II) was achieved in 67% immediately and 81% at 1-year from surgery. Better immediate but not late nerve function was associated with smaller preoperative tumor size and residual tumor left behind.

    Conclusions: Less-than-total resection of large acoustic neuromas allows for excellent facial nerve outcomes, however the rate of persistent growth is inversely proportional to the size of residual tumor. Growing tumor remnants may be treated effectively with stereotactic radiation, though about 1/3 of tumors may still require surgical salvage. The NTR group had slightly better CNVII outcome compared to GTR without increased risk of recurrence.

    Patient Care: Allow skullbase surgeons to better understand advantages and disadvantage of subtotal and near-total vs. gross total resection of large acoustic neuromas.

    Learning Objectives: By the conclusion of this session, participants should be able to: 1) Identify advantages and disadvantages of near-total, subtotal and gross total resection of large acoustic neuromas 2) Describe facial nerve outcome in treatment of large acoustic neuromas as function of degree of resection, 3) Discuss, in small groups difference in rate of tumor recurrence depending on degree of resection


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