Abstract : Object: To evaluate the clinical results, especially surgical outcome of the cystic VS with fluid-fluid level.Methods: Forty-five cystic VS and 86 solid VS were enrolled and the former were divided into fluid-level and non-fluid-level group further. The clinical and neuroimaging features, intraoperative findings, and surgical outcomes of the tree groups were retrospectively compared.Results: Peritumoral adhesion is significantly greater in the fluid-level group (70.8%) than in the non-fluid-level group (28.6%) and the solid group (25.6%) (P<0.0001).Complete removal was significantly fewer in the fluid-level group (45.8%) than in the non-fluid-level group (76.2%, 16/21) and the solid group (75.6%, 65/86) (p=0.015). Postoperative facial nerve function in the fluid-level group is less favorable than two other groups, Good/satisfactory facial nerve function1-year after surgery was seen in 50.0% cases of the fluid-level group versus 83.3% cases of the non-fluid-level group (P=0.038).Conclusions: The cystic VS with fluid-fluid level have more frequency to adhere to surrounding neurovascular structures and less favorable surgical outcome. The possible mechanismof peritumoral adhesion is intratumoral hemorrhage and consequent inflammatory reactions that lead to destruct the tumor–nerve barrier. These findings may be useful in predicting surgical outcome and making surgical strategy preoperatively.Keywords: cystic vestibular schwannoma · fluid-fluid level · peritumoral adhesionCystic vestibular schwannoma (VS) is described as behaving more aggressively, with atypical initial symptoms, preoperative facial palsy, short clinical history, large size, unenlarged internal auditory canal and sudden deterioration because of rapid growth or unpredictable expansion of the cystic component or hemorrhage.Cystic VS also present a therapeutic dilemma. Observation is not recommended for these tumors as the cystic component expand rapidly, resulting in severe mass effect and hydrocephalus6. As to radiotherapy, apart from the large tumor size at diagnosis and the cystic component, sudden deterioration resulting from expansion of the cystic component or hemorrhage after radiosurgery does not support this option too.As to surgery, cystic VS also has worse prognosis because of the difficulty in preserving an adequate subarachnoid dissection plane, hypervascularity of the solid components, frequent engulfment of neurovascular structures, unusual cranial nerve displacement, substantially increased risk of accidental lesion of facial nerve and a greater tendency for postoperative bleeding as compared with solid VS.But the results of other recent studies have not supported above conclusions. So we hypothesize that all cystic VS may not have worse surgical outcome and some undefined factors originating from cystic VS might be responsible for these different clinical and surgical courses. Interestingly, we found a part of cystic VS presented with fluid-fluid level, indicating intratumoral hemorrhage, as previously reported. The aim of this study is to evaluate the clinical results of the cystic VS with fluid-fluid level, and to investigate whether the presence of fluid-fluid level in cystic VS may be relevant and important for predicting the surgical outcome. We also discussed the possible mechanism of peritumoral adhesion and formation of fluid-fluid level, and its implication for surgical strategy.MethodsPatient PopulationFrom April, 2008 to March, 2012, 224 cases of VS were admitted. The clinical data of all cases were reviewed retrospectively. The tumors were defined as cystic when the radiological evidence of cyst formation presented and the intraoperative findings revealed significant cystic components. The cases that were neurofibromatosis-Ⅱ or treated previously by radiosurgery or had recurrent VS were excluded from this study. Eventually, 45 cases of cystic VS and 86 solid VS were enrolled.Preoperative InvestigationAll routine preoperative investigations were performed. Special investigations included pure tone audiometry, speech discrimination test and auditory evoked potentials recordings. Neuroradiological investigations included bone window CT, MRI with contrast enhancement. These 45 cases of cystic VS were further divided into two groups according to whether fluid– fluid level had been seen on preoperative MRI or not. In order to detect small fluid-fluid level in cystic VS, we even used thin-slice T2-weighted 3D TSE pulse sequence with DRIVE. The tumor size was defined as its largest diameter in the cerebellopontine angle without considering the intracanalicular component of the lesion, which was measured and record by the operators (MW. Z. and DJ. Z.) on the radiological workstation.Surgical ProcedureAll cases were operated via suboccipital retrosigmoid approach by the senior author (CJ. Y.), who has performed more than 1000 cases of VS resection. Standard microneurosurgical techniques were employed with intraoperative neuroelectrophysiological monitoring with Medelec Synergy (Oxford Instruments Medical, UK) in all cases.A complete resection was attempted in all cases. The facial nerve runs along the surface of the tumor and usually becomes elongated and thin. It must pay attention to identify it and dissect it along the arachnoidal plane. Sometime, it is difficult to preserve the arachnoidal plane, due to a stronger peritumoral adhesion. Moreover, the facial nerves may be displaced in a differentposition, which may depend on the pattern of the cyst in VS. The presence of multiple cysts made it more difficult to identify the course of facial nerve and protect it during tumor dissection. The characteristics of the adhesion of tumor were carefully noted by reviewing the surgery and surgical video records. By the senior author (CJ. Y.), the tumor was considered to be adhesive if a subarachonid plane of dissection did not exist between the tumor capsule and peritumoral neurovascular structures, such as facial nerve, brain stem or PICA, which resulted in discontinuity of facial nerve or deliberately leaving small pieces of tumor remnant adhering to these important neurovascular structures; Otherwise it is non-adhesive if the subarachonid plane of dissection did exist and can be lent to blunt or sharp dissect the tumor capsule from facial nerve, brain stem or PICA totally.Postoperative Outcome and Follow-up Postoperative facial nerve function wasassessed according to the House-Brackmann (HB) classification system at discharge (about two weeks postoperatively) and 1 year postoperative. All cases were analyzed for complications and postoperative course and followed up by repeated MRI and neurological examination, especially facial nerve function.Statistical AnalysisWith the statistics software of SPSS 12.0, One-way ANOVA analysis was used to determine statistical differences in the duration of symptoms and tumor size between cystic VS with or without fluid-level and solid VS. Chi-square test was used to determine the differences in the rate of multicyst, peritumoral adhesion, total resection and facial nerve outcome between cystic VS with or without fluid-level and solid VS. Significant differences was considered at p<0.05.ResultsClinical FeaturesThese groups consisted of 66 male and 65 female cases who were 13 to 79 years of age (mean 44.86 years). According to preoperative MRI, 24 cases of cystic VS with fluid-fluid level were regarded as fluid-level group. While, 21 cases without fluid-fluid level were regarded as non-fluid-level group. (Figure 1 A, B) It is noteworthy that thin-slice T2-weighted 3D TSE pulse sequence with DRIVE detected some small fluid-fluid levels in 7 cases, which had not beenfound in conventional MRI scan. (Figure 2 A, B) Moreover, obvious multicyst was seen in 19 cases (79.2%, 19/24) of the fluid-level group versus 10 cases (47.6, 10/21) of the non-fluid-level group (P=0.027). (Figure 3)The clinical records of cystic VS were summarized in Table 1. The mean duration of symptoms was 41.49±11.13 (Mean±SE) months in the fluid-level group, 39.38±10.90 months in the non-fluid-level group and 51.92±7.83 months in the solid group(p = 0.644). The mean tumor size was 38.63±1.89 (Mean±SE) mm in the fluid-level group, and 39.14±2.41mm in the non-fluid-level group (p = 0.955). It was 32.42±1.11 mm in the solid group and significantly smaller than that of cystic VS (p=0.004)Surgical OutcomeIn the fluid-level group, 17(70.8%, 17/24) were considered to be adhesive, of which 14 adhered to facial nerve (Figure 4), 2 adhered to brain stem and 1 adhered to PICA. While in the non-fluid-level group, 6(28.6%, 6/21) were considered to be adhesive, of which 5 adhered to facial nerve and 1 adhered to PICA. And in the solid group, 22(25.6%, 22/86) were considered to be adhesive, of which 15 adhered to facial nerve, 5 adhered to brain stem and 2 adhered to both of them simultaneously. Peritumoral adhesion is significantly greater in the fluid-level group (70.8%) than in the non-fluid-level group (28.6%) and the solid group (25.6%) (P<0.0001). Complete removal was achieved in 45.8% (11/24) patients of the fluid-level group which was significantly lower than in the non-fluid-level group (76.2%, 16/21) and the solid group (75.6%, 65/86) (p=0.015). Five (20.8%, 5/24) in the fluid-level group, 1 (4.8%, 1/21) in the non-fluid-level group and 4 (4.7, 4/86) in the solid group had facial nerve broken, in spite of no significant difference (P= 0.058). However, of this case with facial nerve broken in the non-fluid-group, although MRI did not found any fluid-fluid level, there were other obvious hemorrhage appearances, as shown in Figure 5.Postoperative Course and Follow-upAt discharge, the facial nerve function was evaluated in all cases. Reconstruction of the facial nerve was attempted in five cases with facial nerve brok