Facial Nerve Function Outcome and Risk Factors in Resection of Large Cystic Vestibular Schwannomas.

Objective Cystic vestibular schwannomas (VS) in contrast to solid VS tend to have accelerated growth, larger volume, rapid/atypical presentation, lobulated/adherent surface, and unpredictable course of the cranial nerves. Cystic VS are surgically challenging, with worse clinical outcomes and higher rate of subtotal resection (STR). Methods We retrospectively analyzed postoperative outcomes of 125 patients with cystic VS, operated between years 2005 and 2019 in our center. We confronted the extent of the resection and House-Brackmann (HB) grade of facial palsy with the results of comparable cohort of patients with solid VS operated in our center and literature review by Thakur et al. 1 Results Translabyrinthine approach was preferred for resection of large, cystic VS (97.6%). Gross-total resection (GTR) was achieved in 78 patients (62.4%), near-total resection (NTR) with remnant (<4 × 4 × 2 mm) in 43 patients (34.4%), and STR in 4 patients (3.2%). NTR/STR were significantly associated with higher age, tumor volume >5 cm 3 , retrosigmoid approach, high-riding jugular bulb, tumor adherence to the brain stem, and facial nerve ( p = 0.016; 0.003; 0.005; 0.025; 0.001; and <0.00001, respectively). One year after the surgery, 76% of patients had HB grades 1 to 2, 16% had HB grades 3 to 4, and 8% had HB grades 5 to 6 palsy. Worse outcome (HB grades 3 to 6) was associated with preoperative facial palsy, tumor volume >25 cm 3 , and cyst over the brain stem ( p = 0.045; 0.014; and 0.05, respectively). Comparable solid VS operated in our center had significantly higher HB grades 1 to 2 rate than our cystic VS (94% versus 76%; p = 0.03). Comparing our results with literature review, our HB grades 1 to 2 rate was significantly higher (76% versus 39%; p = 0.0001). Tumor control rate 5 years after surgery was 95.8%. Conclusion Our study confirmed that microsurgery of cystic VS has worse outcomes of facial nerve preservation and extent of resection compared with solid VS. Greater attention should be paid to the above-mentioned risk factors.

Large vestibular schwannomas: long-term outcomes after stereotactic radiosurgery.

OBJECTIVES: Stereotactic radiosurgery (SRS) is an established treatment option of small/medium-sized vestibular schwannomas (VSs). Concerning management of the large VSs, primary SRS remains a controversial option. Our retrospective study analyzes long-term radiological and clinical outcomes of SRS in large VSs. MATERIAL AND METHODS: We retrospectively analyzed 73 patients with single large VS, treated with SRS. Inclusion criteria were: tumor volume >4 cm3, follow-up >2 years, radiological (3D-volumetric studies) and clinical follow-up. SRS was either primary (94.5%) or secondary (5.5%) treatment. The median marginal dose (50%-isodose line) was 12Gy (11.5-12Gy). Fisher exact test, t-test, ANOVA, Kaplan-Meier and Cox regression models were performed when appropriate RESULTS: The median follow-up was 5.5 years. The median VS volume at SRS was 6.5 cm3 (range 4-14.2 cm3). The tumor control rates assessed from Kaplan-Meier curve were 88.3%, 82.4% and 74.7% 5.8 and 10 years after SRS, respectively. Tumor shrinkage was observed in 83.6% of patients (n=61), unchanged volume in 4.1% patients (n=3) and progression in 12.3% (n=9). The median tumor volume significantly decreased to 4.0 cm3, measured at 5-year follow-up (p<0.0001). Large cystic VSs responded better to SRS then homogeneous. Pre-SRS serviceable hearing was present in 37% of patients; 55% of these had hearing preserved after treatment. After SRS, new facial palsy (House-Brackmann gr. III-VI) appeared in 4.1% of patients; 9.6% of patients had transient brainstem/cranial nerves edema. For tumor progression, 8.2% of patients underwent resection, 2.8% of patients repeated SRS. CONCLUSION: Our results are showing that SRS might be safe and effective primary treatment even in large VSs. However, long-term tumor control rates are lower in comparison with small/medium-sized VSs. Thus, closer follow-up should be applied.

Benefits of pallidal stimulation in dystonia are linked to cerebellar volume and cortical inhibition.

Clinical benefits of pallidal deep brain stimulation (GPi DBS) in dystonia increase relatively slowly suggesting slow plastic processes in the motor network. Twenty-two patients with dystonia of various distribution and etiology treated by chronic GPi DBS and 22 healthy subjects were examined for short-latency intracortical inhibition of the motor cortex elicited by paired transcranial magnetic stimulation. The relationships between grey matter volume and intracortical inhibition considering the long-term clinical outcome and states of the GPi DBS were analysed. The acute effects of GPi DBS were associated with a shortening of the motor response whereas the grey matter of chronically treated patients with a better clinical outcome showed hypertrophy of the supplementary motor area and cerebellar vermis. In addition, the volume of the cerebellar hemispheres of patients correlated with the improvement of intracortical inhibition which was generally less effective in patients than in controls regardless of the DBS states. Importantly, good responders to GPi DBS showed a similar level of short-latency intracortical inhibition in the motor cortex as healthy controls whereas non-responders were unable to increase it. All these results support the multilevel impact of effective DBS on the motor networks in dystonia and suggest potential biomarkers of responsiveness to this treatment.

Dualistic effect of pallidal deep brain stimulation on motor speech disorders in dystonia.

BACKGROUND: Although pallidal deep brain stimulation (GPi-DBS) is an effective treatment for dystonia, it may cause important stimulation-induced side-effects such as hypokinetic dysarthria or stuttering. However, the reasons behind the occurrence of these side-effects remain unknown. OBJECTIVE: To objectively investigate the impact of GPi-DBS on patients with dystonia on speech fluency, intelligibility, and key aspects of hyperkinetic and hypokinetic dysarthria. METHODS: Speech was systematically evaluated in 19 dystonic patients with GPi-DBS. Each patient was tested twice within one day in both the GPi-DBS ON and GPi-DBS OFF stimulation conditions. A control sample of 19 matched healthy speakers underwent the same speech assessment. RESULTS: We observed an improvement of hyperkinetic dysarthria symptoms in 47% and an aggravation of hypokinetic dysarthria symptoms in 26% of patients with the GPi-DBS switched ON. A higher stimulus intensity was found in a group of patients in whom the hypokinetic dysarthria worsened with the GPi-DBS ON when compared to other dystonic patients (p = 0.02). Furthermore, we revealed a significant increase of dysfluent words in the GPi-DBS ON when compared to OFF condition (p = 0.001) associated with the shorter distance of the active contact localization along the medio-lateral direction (r = -0.70, p = 0.005). CONCLUSION: This study provides evidence of dualistic effects of GPi-DBS on speech in dystonia manifested as an improvement of hyperkinetic or a deterioration of hypokinetic dysarthria. Our findings suggest that lower stimulation parameters and placement of active contacts more laterally in the internal globus pallidus should be preferred to avoid the possible side effects of hypokinetic dysarthria and dysfluency.

Distinct populations of neurons respond to emotional valence and arousal in the human subthalamic nucleus.

Both animal studies and studies using deep brain stimulation in humans have demonstrated the involvement of the subthalamic nucleus (STN) in motivational and emotional processes; however, participation of this nucleus in processing human emotion has not been investigated directly at the single-neuron level. We analyzed the relationship between the neuronal firing from intraoperative microrecordings from the STN during affective picture presentation in patients with Parkinson's disease (PD) and the affective ratings of emotional valence and arousal performed subsequently. We observed that 17% of neurons responded to emotional valence and arousal of visual stimuli according to individual ratings. The activity of some neurons was related to emotional valence, whereas different neurons responded to arousal. In addition, 14% of neurons responded to visual stimuli. Our results suggest the existence of neurons involved in processing or transmission of visual and emotional information in the human STN, and provide evidence of separate processing of the affective dimensions of valence and arousal at the level of single neurons as well.