Selective Facial Muscle Activation with Acute and Chronic Multichannel Cuff Electrode Implantation in a Feline Model.

OBJECTIVES: Facial paralysis is a debilitating condition with substantial functional and psychological consequences. This feline-model study evaluates whether facial muscles can be selectively activated in acute and chronic implantation of 16-channel multichannel cuff electrodes (MCE). METHODS: Two cats underwent acute terminal MCE implantation experiments, 2 underwent chronic MCE implantation in uninjured facial nerves (FN) and tested for 6 months, and 2 underwent chronic MCE implantation experiments after FN transection injury and tested for 3 months. The MCE were wrapped around the main trunk of the skeletonized FN, and data collection consisted of EMG thresholds, amplitudes, and selectivity of muscle activation. RESULTS: In acute experimentation, activation of specific channels (ie, channels 1-3 and 6-8) resulted in selective activation of orbicularis oculi, whereas activation of other channels (ie, channels 4, 5, or 8) led to selective activation of levator auris longus with higher EMG amplitudes. MCE implantation yielded stable and selective facial muscle activation EMG thresholds and amplitudes up to a 5-month period. Modest selective muscle activation was furthermore obtained after a complete transection-reapproximating nerve injury after a 3-month recovery period and implantation reoperation. Chronic implantation of MCE did not lead to fibrosis on histology. Field steering was achieved to activate distinct facial muscles by sending simultaneous subthreshold currents to multiple channels, thus theoretically protecting against nerve damage from chronic electrical stimulation. CONCLUSION: Our proof-of-concept results show the ability of an MCE, supplemented with field steering, to provide a degree of selective facial muscle stimulation in a feline model, even following nerve regeneration after FN injury. LEVEL OF EVIDENCE: N/A.

Magnetic Resonance-Guided Laser Ablation for the Treatment of Recurrent Dural-Based Lesions: A Series of Five Cases.

BACKGROUND AND OBJECTIVE: Magnetic resonance-guided laser-induced thermotherapy (MR-LITT) is a minimally invasive technique that shows promise in neuro-oncology because of its superiority in delivering precise minimally invasive thermal energy with minimal collateral damage. In this analysis, we investigate initial data on the effect of MR-LITT on dural-based lesions. METHODS: Five patients were identified with dural-based lesions (4 meningiomas, 1 solitary fibrous tumor) with clear evidence of radiologic progression. In all 5 cases, the tumors were localized to the lateral convexity or paramedian locations in the supratentorial space. All patients received MR-LITT and then a follow-up magnetic resonance imaging scan at 24 hours after treatment, at 1 month, and at each subsequent follow-up visit. Local control of the ablated tumor was evaluated with radiographic follow-up and symptomatic progression-free survival was recorded. RESULTS: Five LITT treatments were performed on 5 patients with an average age of 65.2 years. The average tumor volume was 29.7 cm3 and ablation dosage was 12.4 W. On average, 80% of the pretreatment lesion volume was ablated. The mean follow-up time was 59.3 weeks. In total, 2 patients (1 with an anaplastic meningioma and 1 with a solitary fibrous tumor) had radiographic evidence of disease progression. In the observed time of the 3 patients with no progression, there was a 52% reduction in tumor volume. There were no major perioperative complications. CONCLUSIONS: MR-LITT is a promising technology for dural-based lesion treatment. This initial study demonstrates that MR-LITT is safe and offers several advantages over open surgical treatment. Randomized studies are needed to evaluate its role as a treatment adjunct.

The role of magnetic resonance-guided laser ablation in neurooncology.

INTRODUCTION: The use of magnetic resonance-guided laser-induced thermal therapy (MR-LITT) as a minimally invasive method of treating intra-cranial pathology is a rapidly growing field. The use of MR-LITT in neurooncology has shown promising results; however, there has been no review to date of the current literature. METHODS: A review of the published literature regarding MR-LITT in neurooncology was performed. Studies on PubMed were included if at least one patient with a cerebral tumour or radiation necrosis was treated using quantitative MR thermography-guided LITT, as well as if either safety or outcomes were discussed. RESULTS: In treating recurrent Grade-III and -IV gliomas, we found improved median overall survival of 20.9 months from diagnosis of recurrence, which is comparable with that of 18.9 months for high-dose-rate brachytherapy and 24.4 months for repeated open surgery. Median progression-free survival (PFS) of recurrent glioma is noted to be 4.5 months. For metastatic lesions, we found a median overall survival (OS) to vary between 9.0 and 19.8 months with a PFS between 3.8 and 8.5 months. Current literature reports median OS in similar patients to lie between 7.0 and 28.6 months. Severe complication rates (with permanent deficits) are found to be between 12 and 16.7%, comparable with 11% found in literature for open surgery. CONCLUSIONS: The current literature shows that MR-LITT is safe and shows promising local tumour control rates. Larger randomised studies are warranted to further investigate this adjuvant therapy in the treatment of recurrent high-grade gliomas and metastases.