The authors' first results show that tumor resections with 5-ALA in combination with intraoperative cortical stimulation have the advantages of both methods and, thus, provide additional safety for the neurosurgeon during resections of primary malignant brain tumors in eloquent areas. Nonetheless, more cases and additional studies are necessary to further prove the advantages of this multimodal strategy.

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OBJECTIVE This study was conducted to investigate the success rate of using the facial motor evoked potential (FMEP) of orbicularis oculi and oris muscles for facial nerve function monitoring with use of a stepwise protocol, and its usefulness in predicting facial nerve outcome during cerebellopontine angle (CPA) surgeries. METHODS FMEPs were recorded intraoperatively from 60 patients undergoing CPA surgeries. Transcranial electrocortical stimulation (TES) was performed using corkscrew electrodes positioned at hemispheric montage (C3/C4 and CZ). The contralateral abductor pollicis brevis muscle was used as the control response. Stimulation was always applied contralaterally to the affected side using 1, 3, or 5 rectangular pulses ranging from 200 to 600 V with 50 μs of pulse duration and an interstimulus interval of 2 ms. Facial potentials were recorded from needles placed in the orbicularis oculi and oris muscles. RESULTS FMEP from the orbicularis oris and oculi muscles could be reliably monitored in 86.7% and 85% of the patients, respectively. The immediate postoperative facial function correlated significantly with the FMEP ratio in the orbicularis oculi muscle at 80% amplitude ratio (P = .037) and orbicularis oris muscle at 35% ratio (P = .000). FMEP loss was always related to postoperative facial paresis, although in different degrees. CONCLUSION FMEPs can be obtained reliably by using TES with 3 to 5 train pulses. Stable intraoperative FMEPs can predict a good postoperative outcome of facial function. However, further refinements of this technique are necessary to minimize artifacts and to make this method more reliable.

FMEP amplitude ratio and waveform morphology during VS resection seem to represent independent quantitative parameters that can be used to predict postoperative facial function. Event-to-baseline FMEP monitoring is quite useful to dictate when intraoperative changes in surgical strategy are warranted to reduce the chances of facial nerve injury.

Hearing preservation is a major goal in the treatment of neurofibromatosis type 2 (NF2) associated vestibular schwannoma (VS), particularly in children and adolescents. In this study, we retrospectively reviewed hearing and volumetry data sets of 39 operated tumors (ears) in 23 patients under the age of 25 and in a follow-up period of 21 to 167 months. Hearing data over a compatible period on 20 other tumors, which did not receive surgery due to their less aggressive nature, were included for comparison. Surgery was carried out via a retrosigmoid approach with the brainstem auditory evoked potential (BAEP) guide. Immediately after surgery, functional hearing was maintained in 82% of ears. Average hearing scores were better in the non-surgery ears. However, the hearing scores in both groups worsened gradually with a similar dynamic during the 42-month postoperative follow-up period. No accelerated impairment of hearing was evident for the operated cases. Rather, the gap between the two hearing deterioration lines tended to close at the end of the follow-up period. Our result suggested that the BAEP-guided surgery did not cause additional hearing deterioration in the long-term and seemed to slow down hearing deterioration of those tumors that were initially more aggressive.

ObjectiveNearly two-thirds of patients with vestibular schwannoma (VS) are reporting a significantly impaired quality of life due to tinnitus. VS-associated tinnitus is attributed to an anatomical and physiological damage of the hearing nerve by displacing growth of the tumor. In contrast, the current pathophysiological concept of non-VS tinnitus hypothesizes a maladaptive neuroplasticity of the central nervous system to a (hidden) hearing impairment resulting in a subjective misperception. However, it is unclear whether this concept fits to VS-associated tinnitus. This study aims to determine the clinical predictors of VS-associated tinnitus to ascertain the compatibility of both pathophysiological concepts.MethodsThis retrospective study includes a group of 478 neurosurgical patients with unilateral sporadic VS evaluated preoperatively regarding the occurrence of ipsilateral tinnitus depending on different clinical factors, i.e., age, gender, tumor side, tumor size (T1–T4 according to the Hannover classification), and hearing impairment (Gardner–Robertson classification, GR1–5), using a binary logistic regression.Results61.8% of patients complain about a preoperative tinnitus. The binary logistic regression analysis identified male gender [OR 1.90 (1.25–2.75); p = 0.002] and hearing impairment GR3 [OR 1.90 (1.08–3.35); p = 0.026] and GR4 [OR 8.21 (2.29–29.50); p = 0.001] as positive predictors. In contrast, patients with large T4 tumors [OR 0.33 (0.13–0.86); p = 0.024] and complete hearing loss GR5 [OR 0.36 (0.15–0.84); p = 0.017] were less likely to develop a tinnitus. Yet, 60% of the patients with good clinical hearing (GR1) and 25% of patients with complete hearing loss (GR5) suffered from tinnitus.ConclusionThese data are good accordance with literature about non-VS tinnitus indicating hearing impairment as main risk factor. In contrast, complete hearing loss appears a negative predictor for tinnitus. For the first time, these findings indicate a non-linear relationship between hearing impairment and tinnitus in unilateral sporadic VS. Our results suggest a similar pathophysiology in VS-associated and non-VS tinnitus.

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Surgical resection of AVMs in eloquent motor areas can be considered a safe option for selected cases when performed in conjunction with a detailed functional assessment. Possible selection criteria for surgical treatment are discussed in light of the presented clinical data.