Delayed microsurgery for vestibular schwannoma after gamma knife radiosurgery

Abstract

Stereotactic radiosurgery for vestibular schwannomas (VSs) has become popular during the last decade with promising clinical results after long-term follow-up. However, on rare occasions, some cases have needed traditional microsurgery to remove the tumor several months or years after radiosurgery. We present a retrospective analysis of data acquired during a 16-year period in delayed microsurgery of seven patients with VSs who underwent gamma knife surgery (GKS). A total of 444 with VS underwent GKS between March 1993 and December 2008, and 7 (1.57%) underwent delayed microsurgery at a median of 26 months (range from 3 months to 6 years) after GKS. The mean size of the tumor during GKS was 10.4 ml (range 2.3-23.5 ml). These seven patients were younger, and female predominant. The indications of microsurgery included adverse radiation effect with peri-focal edema, tumor enlargement, and cyst enlargement. Although the perifocal edema could lead to more difficulty in surgery than in typically performed operations for schwannoma, subtotal resection was achieved in all patients. There was no surgery-related morbidity or mortality. The histology showed benign tumor in five patients, malignant peripheral nerve sheath tumor in one, and necrotic tissue in one. The need of microsurgery for further treatment of VS after radiosurgery is rare, but can be a challenge to neurosurgeons in terms of surgical indication, timing, and techniques. The authors concluded the incidence of delayed microsurgery was 1.57% in a series of 444 patients over a 16-year period. We concluded some experience from operative indications, timing, approach, and outcome.

Vestibular Schwannoma Microsurgery for Recurrent Tumors After Radiation Therapy or Previous Surgical Resection

“…Timing for microsurgical resection after radiation therapy varied widely in previously published surgical series ranging between 6 and 92 months (2,14,15,19,22,25,39). Some authors recommend to avoid surgery during the first 2 to 3 years after radiation therapy unless there are significant symptoms associated with tumor enlargement (9,33,37).…”

A meta-analysis of treatment of vestibular schwannoma using Gamma Knife radiosurgery

“…The total number of patients meeting the criteria for the work selected in 28 articles was 3233 [7, 9, 12, 15–17, 22, 23, 25–27, 29, 30, 33, 34, 36–41, 43, 45, 47–50, 52]. The described groups of patients ranged from 21 to 444 in size depending on location and duration of the study [33, 36]. Average age was 52.6 years.…”

Surgery of vestibular schwannomas

“…[32] It is difficult to assume that a remnant of VS that expanded despite the previous therapy will change its biological behavior and stop growing. As recommended by some authors, partial removal [31,33] may indeed lead to better functional outcome in some cases; but it is a short-term solution.…”

“…[9,10] Patients with failed radiosurgery are treated either with repeated radiosurgery or surgically. [29][30][31] Surgery is indicated in patients with large tumors compressing the brainstem, in case of sustained tumor growth, which is documented on serial MR examinations or in case of progression of symptoms. [32] Surgery after failed radiosurgery is more complex and challenging due to the development of extensive postradiational changes.…”

“…[32] Surgery after failed radiosurgery is more complex and challenging due to the development of extensive postradiational changes. [29,31] Still, its goal should be compete tumor removal. [32] It is difficult to assume that a remnant of VS that expanded despite the previous therapy will change its biological behavior and stop growing.…”