43.1 Introduction

Vestibular schwannoma (VS) recurrence after prior microsurgery (MS) is rare, with an estimated incidence of 0.05 to 9.2% following gross total resection (GTR) at the primary operation.s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur Recurrence is defined as occurring specifically after GTR, in comparison to progression of residual tumor—a considerably more common occurrence, with an incidence of 44% after subtotal resection (STR).s. Literatur ^,​ s. Literatur This distinction is emphasized in planning for repeat surgery, as it is generally held that a prior GTR or an aggressive STR will have a higher risk of scaring and adhesions along the facial nerve–tumor interface (FNTI), given that it was previously dissected along its full length. By contrast, a less aggressive primary STR that was limited to a biopsy or debulking may not have significantly engaged the FNTI, resulting in a less perilous repeat operation. Furthermore, the capacity of the facial nerve to withstand a second dissection may be significantly diminished, particularly if it was previously subject to substantial manipulation during the primary operation.

Various tactics are employed in treating recurrent or progressive residual VS after MS, including stereotactic radiosurgery (SRS), fractionated radiotherapy, repeat MS, and observation—a strategy reserved for those patients with slow-growing tumors and without brainstem compression. For the majority of patients, SRS is the treatment of choice, which has been demonstrated to provide excellent tumor control in VS recurrence after MS.s. Literatur Notwithstanding, repeat MS after MS may warrant consideration in specific patient populations, in particular those individuals with brainstem compression requiring more urgent treatment, in patients with secondary trigeminal neuralgia who would benefit from direct decompression of the trigeminal nerve, tumors with large macrocystic changes, or individuals strongly desiring surgical treatment in lieu of radiation.

43.2 Example—Recurrent Vestibular Schwannoma

A healthy 28-year-old man experienced progressive hearing loss in his left ear over 12 months. Neurologic workup included magnetic resonance imaging (MRI) of the brain, which revealed a left 3.5-cm cerebellopontine angle (CPA) mass with extension into the internal auditory canal (IAC) and homogenous gadolinium enhancement, consistent with VS (Fig. 43‑1 a). The fourth ventricle was effaced and signs of early hydrocephalus were apparent. The patient was taken to the operating room for a retrosigmoid (RS) craniotomy and drilling of the IAC, during which GTR was achieved, and baseline facial nerve stimulation at the brainstem was preserved. The patient awoke with House–Brackmann (HB) grade I facial nerve function, and underwent a routine postoperative recovery. Follow-up MRI at 6 months was negative for nodular enhancement or any other evidence of residual tumor (Fig. 43‑1 b).

Further follow-up continued uneventfully until surveillance imaging at 7 years after initial resection demonstrated a new, small area of enhancement within the left IAC (Fig. 43‑1 c). Treatment options including SRS, repeat MS, and observation were discussed, and the patient elected surgery. Repeat MS was planned via a translabyrinthine (TL) approach; the IAC dura was opened in the typical fashion, and a clear nodular recurrence was identified along the distal superior vestibular nerve. Dissection was readily carried out along the FNTI, and GTR was achieved without marked difficulty. Postoperatively, the patient maintained HB grade I facial nerve function; his immediate postoperative course was complicated by cerebrospinal fluid (CSF) rhinorrhea, which resolved after placement of a lumbar drain and 48 hours of intermittent CSF diversion. Follow-up MRI 3 months after surgery confirmed GTR, and the patient has continued to remain recurrence free over more than 5 years of subsequent follow-up (Fig. 43‑1 d).

43.3 Review of the Literature—Recurrent Vestibular Schwannoma

Four studies have described individual outcomes after repeat MS for recurrent VS in radiation-naive, non–neurofibromatosis type 2 (NF2) patients with no history of facial reanimation surgery, documenting a total of 50 patients (Table 43‑1 ).s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur For the overall patient cohort, mean time-to-revision was 73 months, employment of the same approach for repeat surgery was common (90%), extent of resection was GTR in most patients (95%), and unfavorable (HB grades III–VI) facial nerve function after revision surgery was frequently reported (68%). Additional complications were rare, and predominantly limited to CSF leak (4%).

In the largest preceding series, Samii et al reported outcomes in 36 radiation-naive individuals undergoing repeat MS after primary GTR, as well as a second 17-patient cohort of patients who had previously undergone SRS during the interval between primary GTR and repeat MS.s. Literatur To provide a control, outcomes in both groups were compared to a randomly selected group of 30 primary VS resections with no history of prior radiation. All operations were via RS craniotomy, and GTR was universally achieved. Within the MS-after-MS only group, favorable HB grades I to II preoperative facial nerve function was present in 25 (69%) at the time of repeat surgery; this was preserved in 12 (48%). No second recurrences were reported, and the mean follow-up period after repeat MS was 60 months. Of particular interest, Samii et al did not detect a significant difference in their comparison between patients undergoing repeat MS with and without a prior history of SRS, with respect to facial nerve, extent of resection, or tumor control outcomes.

A series of six recurrences without a history of radiation therapy or facial reanimation were reported by Roche et al; three each underwent enlarged TL after primary TL surgery, or repeat surgery via TL after primary RS.s. Literatur In the enlarged TL group, GTR was achieved in two (67%), and favorable HB grades I to II facial nerve function was preserved in the only patient who had favorable preoperative function (100%). By contrast, of the three patients who underwent repeat TL surgery after primary RS, GTR was again achieved in two (67%), but HB grades I to II function was preserved in only one of three patients with favorable preoperative facial nerve function.

Four recurrences after GTR were reported by Freeman et al, within a larger series of both recurrent and residual tumors undergoing repeat surgery.s. Literatur Two underwent same-approach repeat surgery, both of who deteriorated from favorable pre-repeat surgery facial nerve function to unfavorable post-repeat surgery favorable nerve function. Of the two patients in whom an alternate approach was utilized, one maintained stable HB grade III facial nerve function, while the other improved from HB grades III to II. No complications or second recurrences were reported after a mean of 47 months of follow-up. Another small series of four repeat surgeries was reported by Shelton, who employed the TL approach at both primary and repeat surgery.s. Literatur GTR was achieved in all four patients (100%), and favorable postoperative facial nerve function was preserved in one of two patients with preoperative HB grades I to II function (50%); no other complications were reported.

Hong et al reported a series of 15 patients undergoing repeat MS; unfortunately, detailed analysis is prohibited by pooled reporting of outcomes between these patients and three others who had growth of residual tumors, rather than true recurrences.s. Literatur Although 14 of these patients underwent alternate-approach repeat surgery, detailed outcomes are not specified on an individual patient basis, and so the outcomes by approach cannot be compared. Notwithstanding, overall outcomes were encouraging, with preservation of favorable preoperative HB grades I to II facial nerve function in seven of ten patients (70%), and GTR in ten of fifteen patients (67%).