Facial Stimulation Research Articles

A full-head model to investigate intra and extracochlear electric fields in cochlear implant stimulation

Objective. Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full-head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation. Approach. Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar (TP), and partial TP modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve. Main results. The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities. Significance. Full-head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.

Triphasic Pulse Stimulation Pattern in Cochlear Implant Users Assessed with Ecap Measure

The rationale for the use of three-phase stimulation for programming the processor of the cochlear implantation system (CI) in patients with deafness is presented. To study the possibilities of using a new type of stimulation, we selected patients after cochlear implantation, with signs of facial nerve stimulation (FNS) in postoperative period. All subjects were previously fitted with an audio processor with individual fitting maps based on traditional biphasic stimulation. The use of three-phase stimulation to prevent FNS is caused by the geometry of the electric current pulses, which allows to reduce the penetrating power of the charge in the tissues and eliminate the effect on the facial nerve, without resorting to reducing the levels of stimulation necessary to create a dynamic range of sound perception. Comparative data of the parameters and the results of audiological testing in 21 patients with symptoms of FNS with traditional (two-phase) and three-phase electrical pulses in the stimulation algorithm of the CI system are presented. The positive effect of three-phase stimulation has been established. The results of the study show a significant increase in sound perception indicators when switching to a three-phase stimulation algorithm.

Hearing Improvement after Radiation Therapy for a Facial Nerve Schwannoma: Report of a Case and Review of Literature

Abstract Introduction While facial nerve schwannomas are considered benign, they can impart various significant clinical effects due to pressure on nearby cerebrovascular structures within the cerebellopontine angle (CPA). Although surgical resection and/or radiation therapy often provide definitive treatment of such tumors, posttreatment hearing loss is a common finding. In this report, we present the case of a patient with a facial nerve schwannoma successfully treated with radiotherapy with resultant hearing improvement, an extremely rare clinical finding. Case Presentation A 63-year-old woman presented with a 1-year history of progressively worsening hearing loss and tinnitus. Brain imaging demonstrated an enhancing lesion of the right CPA measuring 2.7 × 2.1 × 3.1 cm. Pretreatment audiometry evaluation revealed sensorineural hearing loss in the right ear with a pure-tone average (PTA) of 74 dB, speech threshold (ST) of 75 dB, and speech discrimination (SD) of 0%. The patient proceeded with attempted surgical resection, aborted due to significant facial nerve stimulation, and ultimately underwent radiation therapy (50.4 Gy, 28 fractions). At the 1-year follow-up visit, the patient reports subjective hearing loss resolution with PTA of 34 dB, 30 dB ST, and 88% SD on audiological evaluation. Conclusion Although radiation therapy for schwannomas within the CPA has historically been associated with hearing loss, fractionated stereotactic radiotherapy (FSRT) may provide improved clinical outcomes compared with high-dose radiosurgery. Given the effectiveness of this treatment modality and improved quality of life offered to patients over surgery, FSRT may be considered an initial management option for patients with facial nerve schwannomas.

Comparative study of the effects of ibuprofen, acetaminophen, and codeine in a model of orofacial postoperative pain in male and female rats.

Pain management is a primary goal after oral surgeries, but little is known about sex differences in the sensitivity to analgesics. This study aimed to compare the efficacy of three drugs with analgesic potential on heat and mechanical hyperalgesia, spontaneous pain and locomotion on male and female rats subjected to a model of orofacial postoperative pain. Male and female Wistar rats were submitted to intraoral incision or sham surgery, and on postoperative day 3, the effect of the ibuprofen (30 and 100mg/kg), acetaminophen (100 and 300mg/kg) and codeine (3 and 10mg/kg) was assessed on responses to heat and mechanical facial stimulation, facial grooming, and locomotion. Ibuprofen reduced heat and mechanical hyperalgesia and grooming behavior in male and female rats in a non-sedative dose; acetaminophen dose-dependently reduced the mechanical hyperalgesia and abolished the heat hyperalgesia and the grooming behavior but caused sedation in both sexes; codeine dose-dependently reduced the mechanical hyperalgesia in male and female rats, and reduced the heat hyperalgesia, but females were less sensitive than males. It reduced spontaneous facial grooming in both sexes, but induced hyperlocomotion in females. Ibuprofen presented the most favorable profile, since it reduced over 50% heat and mechanical hyperalgesia in male and female rats, and significantly reduced spontaneous pain, without causing sedation or affecting locomotion. The identification of sex differences in the sensitivity and safety profile of frequently used analgesics can help guide the choice of more effective individualized therapies for pain control.

Evaluation of Cochlear Implantation in Children With Cochlear Nerve Absence or Deficiency.

To identify associations between cochleovestibular anatomy findings and hearing outcomes found in children with imaging evidence of an absent or hypoplastic cochlear nerve treated with cochlear implantation (CI). retrospective review. Cochlear implant program at tertiary care center. A retrospective review was performed to identify children with imaging evidence of cochlear nerve absence or deficiency who underwent CI evaluation. High-resolution 3-dimensional T2-weighted magnetic resonance imaging in the oblique sagittal and axial planes were reviewed by a neuroradiologist to identify cochleovestibular anatomy. Hearing was assessed pre and postoperatively with Speech Perception Category scores. Seven CI recipients were identified (n = 10 ears) who had bilateral severe to profound sensorineural hearing loss with lack of auditory development with binaural hearing aid trial and imaging evidence of cochlear nerve aplasia/hypoplasia. All ears had 2 nerves in the cerebellopontine angle (100%, n = 10), half of the ears had evidence of 2 or less nerves in the internal auditory canal (IAC). All children showed large improvement in speech perception after CI. Our experience with CIs for children with absent or hypoplastic cochlear nerves demonstrates that CI can be a viable option in select patients who satisfy preoperative audiological criteria. Radiological identification of a hypoplastic or aplastic cochlear nerve does not preclude auditory innervation of the cochlea. CI recipients in this subgroup must be counseled on difficulty in predicting postimplantation language and speech outcomes, and cautioned about facial nerve stimulation.

Accuracy of Repetitive Ocular Vestibular-Evoked Myogenic Potentials to Diagnose Myasthenia Gravis in Patients With Ptosis or Diplopia.

We developed repetitive ocular vestibular-evoked myogenic potentials (roVEMP) as an electrophysiologic test that allows us to elicit the characteristic decrement of extraocular muscles in patients with ocular myasthenia gravis (OMG). Case-control studies demonstrated that roVEMP reliably differentiates patients with OMG from healthy controls. We now aimed to evaluate the diagnostic accuracy of roVEMP for OMG diagnosis in patients with ptosis and/or diplopia. In this blinded prospective diagnostic accuracy trial, we compared roVEMP in 89 consecutive patients presenting with ptosis and/or diplopia suspicious of OMG with a multimodal diagnostic approach, including clinical examination, antibodies, edrophonium testing, repetitive nerve stimulation of accessory and facial nerves, and single-fiber EMG (SFEMG). We calculated the roVEMP decrement as the ratio between the mean of the first 2 responses compared with the mean of the sixth-ninth responses in the train and used cutoff of >9% (unilateral decrement) in a 30 Hz stimulation paradigm. Following a complete diagnostic work-up, 39 patients (44%) were diagnosed with ocular MG, while 50 patients (56%) had various other neuro-ophthalmologic conditions, but not MG (non-MG). roVEMP yielded 88.2% sensitivity, 30.2% specificity, 50% positive predictive value (PPV), and 76.5% negative predictive value (NPV). For comparison, SFEMG resulted in 75% sensitivity, 56% specificity, 55.1% PPV, and 75.7% NPV. All other diagnostic tests (except for the ice pack test) also yielded significantly higher positive results in patients with MG compared with non-MG. The study revealed a high sensitivity of 88.2% for roVEMP in OMG, but specificity and PPV were too low to allow for the OMG diagnosis as a single test. Thus, differentiating ocular MG from other neuro-ophthalmologic conditions remains challenging, and the highest diagnostic accuracy is still obtained by a multimodal approach. In this study, roVEMP can complement the diagnostic armamentarium for the diagnosis of MG. This study provides Class I evidence that in patients with diplopia and ptosis, roVEMP alone does not accurately distinguish MG from non-MG disorders. ClinicalTrials.gov: NCT03049956.

Bionic blink improves real-time eye closure in unilateral facial paralysis

Facial paralysis is the inability to move facial muscles thereby impairing the ability to blink and make facial expressions. Depending on the localization of the nerve malfunction it is subcategorised into central or peripheral and is usually unilateral. This leads to health deficits stemming from corneal dryness and social ostracization. Objective: Electrical stimulation shows promise as a method through which to restore the blink function and as a result improve eye health. However, it is unknown whether a real-time, myoelectrically controlled, neurostimulating device can be used as assistance to this pathological condition. Approach: We developed NEURO-BLINK, a wearable robotic system, that can detect the volitional healthy contralateral blink through electromyography and electrically stimulate the impaired subcutaneous facial nerve and orbicularis oculi muscle to compensate for lost blink function. Alongside the system, we developed a method to evaluate optimal electrode placement through the relationship between blink amplitude and injected charge. Main results: Ten patients with unilateral facial palsy were enrolled in the NEURO-BLINK study, with eight completing testing under two conditions. (1) where the stimulation was cued with an auditory signal (i.e. paced controlled) and (2) synchronized with the natural blink (i.e. myoelectrically controlled). In both scenarios, overall eye closure (distance between eyelids) and cornea coverage measured with high FPS video were found to significantly improve when measured in real-time, while no significant clinical changes were found immediately after use. Significance: This work takes steps towards the development of a portable medical device for blink restoration and facial stimulation which has the potential to improve long-term ocular health.

Intraoperative EABR Testing Predicts Strength of Cochlear Implant Stimulation Optimized After Long-Term Use in Pediatric Malformation Ears.

This study focused on the intensities of cochlear implant (CI) stimulation in pediatric CI users with inner ear malformation or cochlear nerve deficiency (CND). In this population, CI programming is difficult because a large intensity of CI stimulation is required to achieve sufficient hearing, but the excess CI stimuli often induce facial nerve stimulation. We aimed to assess whether the results of intraoperative electrically evoked auditory brainstem responses (EABRs) testing predict maximum current levels of CI stimuli (cC levels) optimized by a behavioral-based method after long-term CI use. A retrospective case review. A tertiary referral CI center. A total of 116 ears with malformations (malformation group) and 63 control ears (control group) from patients younger than 18 years who received CI. The malformation group comprised 23 ears with a common cavity (CC), 26 with incomplete partition type 1 (IP-1), 26 with incomplete partition type 2 (IP-2), and 41 with CND. Diagnostic. Correlation between intraoperative EABR results and cC levels determined by the behavioral-based CI programming after long-term CI use. The CC, IP-1, and CND ears required significantly larger cC levels than the IP-2 ears and control groups. However, the cC levels increased to reach the plateau 1 year after surgery in all groups. Among the malformation group, 79 ears underwent intraoperative EABR testing. Greater than 80% of the CC, IP-1, and IP-2 ears and 54.8% of the CND ears exhibited evoked wave V (eV) and were included in the eV-positive category. Myogenic responses but no eV were observed in 18.2, 15.0, and 35.5% of the CC, IP-1, and CND ears, defined as the myogenic category. No eV or myogenic response was elicited in 9.7% of the CND ears. We focused on minimum current levels that elicited eV (eV levels) in the eV-positive category and maximum current levels that did not elicit any myogenic responses (myogenic levels) in the myogenic category. A significant relationship was detected between the eV levels and the cC levels. When analyzed in each malformation type, the eV levels significantly correlate with the cC levels in the CC and CND ears but not in the IP-1 and IP-2 ears, probably because of slight variation within the IP-1 group and the small number of the IP-2 group. The myogenic category did not show a significant relationship between the myogenic levels and cC levels, but the cC levels were similar to or smaller than the myogenic levels in most ears. This study confirmed that intraoperative EABR testing helps predict the optimal cC levels in malformation ears. EABR-based CI programming immediately after cochlear implantation, followed by behavioral-based CI programming, may allow us to achieve early postoperative optimization of CI maps even in young children with severe malformations.

1246 The Impact of Latency Variations on the Predictive Value of Facial Nerve Proximal-to-distal Amplitude Ratio During Vestibular Schwannoma Surgery

INTRODUCTION: Intraoperative facial nerve (FN) electromyographic (EMG) monitoring is now considered an essential part of vestibular schwannoma (VS) surgery and is used for both intraoperative monitoring and postoperative outcome prediction. METHODS: Forty-eight patients underwent FN stimulation at the brainstem (proximal) and the internal acoustic meatus (distal) using a current intensity of 2 mA. The proximal latency and the P/D amplitude ratio were assessed. House-Brackmann grades I-II indicated good FN function; and grades III-VI were considered fair/poor function. A P/D amplitude ratio >0.6 was used as a cutoff to indicate good FN function, while a ratio of =0.6 indicated fair/poor FN function. RESULTS: The P/D amplitude ratio was measured for all patients, and the calculated sensitivity (SE), specificity (SP), positive predictive value (PPV), and negative predictive value (NPV) were 85.2%, 85.7%, 88.5%, and 81.8% respectively. Then the CMAPs from the mentalis muscle were classified based on their proximal latency into: Group I (<6 msec); group II (6-8 msec); and group III (>8 msec). The SE, SP, PPV, and NPV became 90.5%, 90.9%, 95%, and 83.3% respectively in group II. In group I, SE and NPV increased whereas, SP and PPV decreased. While in group III, SP and PPV increased, whereas SE and NPV decreased. CONCLUSIONS: At a latency between 6-8msec, the P/D amplitude ratio was predictive of outcome with high SE and SP. When the latency was <6 msec or >8 msec, the same predictive ability was not observed. Knowing the impact of latency variations of P/D amplitude ratio measurement is important for a better understanding of the ability and limitations of this method in predicting postoperative FN function.

Contralateral Facial Innervation in Healthy Subjects and in Patients with Peripheral Facial Palsy.

Background: We aimed to investigate the extent of the response of the orbicularis oris muscle to stimulation of the contralateral facial nerve both in patients with peripheral facial palsy (PFP) and in healthy subjects. Methods: EMG was performed at 2-6 weeks after the onset of PFP in the patient group and at any time in the healthy control group. We performed nerve conduction testing, electroneurography, and surface and needle EMG. Results: A total of 276 participants (patients/healthy controls: 218/58) were analyzed. The extent of the response of the contralateral orbicularis oris muscles to facial nerve stimulation was higher in healthy controls compared to that in the affected group. The response of the contralateral orbicularis oris muscles to stimulation of the paralyzed facial nerve was more extensive in those patients to whom glucocorticoid or physical therapy had been given. Cross-facial innervation in the orbicularis oris muscle extended up to 1.5 cm in one-third of healthy controls and was higher than that in those with PFP. Glucocorticoid or physical therapy seemed to improve cross-innervation in facial palsy. Conclusions: Our findings suggest that the stimulus leading to the contralateral muscular response is mediated through crossing axons rather than muscular fibers.

Cochlear-facial dehiscence – the most common cause of facial nerve stimulation from a cochlear implant? A case–control study

Objectives To investigate the prevalence of cochlear-facial dehiscence (CFD) and other radiographical pathologies in ears with facial nerve stimulation (FNS) from a cochlear implant (CI). Methods Retrospective case–control study of 27 patients with CI and FNS on either ear (study group) and 27 patients without FNS, matched for age, sex and type of electrode array (control group). Preoperative CT scans of all 108 ears were re-evaluated. Subanalyses included comparisons between the study and control groups and associations between FNS and radiographic pathologies. Results CFDs were detected in 20 of 54 ears (37%) in the study group and in 3 of 54 ears (6%) in the control group (P < 0.001). The corresponding numbers of otosclerosis were 10 (18%) and 0 (P = 0.011) and of developmental anomalies 16 (30%) and 8 (15%) (not significant). FNS was present in 33 ears in the study group, of which 14 (42%) had a CFD. FNS was absent in six ears with CFD and CI, four of which contralateral to an ear with FNS. Eight of 14 ears with FNS and CFD had a lateral electrode array and six had a perimodiolar electrode array. We found no association between the presence of CFD and stimulation thresholds for FNS. The adjusted odds ratio for developing FNS in the presence of a CFD was 9.9 (95% CI 2.7–36.0). Conclusions CFD was the most common radiographic pathology in ears with FNS, with a 10-fold increased risk of FNS. To avoid CI-related FNS, preoperative CT scan and awareness of typical dehiscence symptoms are strongly recommended.

Pathophysiology of Facial Nerve Stimulation and Its Implications for Electrical Stimulation in Cochlear Implants.

A small number of cochlear implant (CI) users experience facial nerve stimulation (FNS), which can manifest as facial twitching. In some patients, this can be resolved by adjusting the electrical stimulation parameters. However, for others, facial stimulation can significantly impair CI outcomes or even prevent its use. The exact mechanisms underlying FNS are unclear and may vary among patients. Transimpedance measurements were used to assess lateral and longitudinal spread of current within 15 cochlea of nucleus CI recipients with FNS (13 unilateral recipients and 1 bilateral recipient). We compared the transimpedance measurements with programming parameters from clinical visits and pre- and postoperative temporal bone computed tomography (CT) scans to identify factors that may contribute to FNS in each CI ear. In nine ears, transimpedance curves showed inflection, which suggests a localized current sink within the cochlea. This indicates a low-impedance pathway through which current exits the cochlea and stimulates the labyrinthine segment of the facial nerve canal. Electrodes near this current sink were disabled or underfit to minimize facial stimulation. In the other seven ears, current flow peaked toward the basal end of the cochlea, suggesting that current exits through the round window or other structures near the basal end of the cochlea, stimulating the tympanic segment of the facial nerve. Objective transimpedance measurements can be used to elucidate the mechanisms of FNS and to develop strategies for optimizing electrical stimulation parameters and speech coding to minimize or eliminate FNS in a small subset of CI users.

First Evidence of Cutaneous Remodelling Induced by Synchronized Radiofrequency Aided by High-Intensity Facial Muscle Stimulation: Porcine Animal Model.

The quality of one's facial appearance diminishes with aging as skin and underlying soft tissues deteriorate. Connective tissue and musculofascial degeneration leads to skin laxity and wrinkles developing. To evaluate the effects of synchronized radiofrequency with high intensity facial stimulation technology on dermal collagen and elastin fibers in a porcine model. Eight sows were divided into Active (N = 6) and Control (N = 2) groups. Synchronized radiofrequency and high intensity facial stimulation were delivered to the ventrolateral abdomen. The Active group received four 20-minute treatments, once a week. Control group was untreated. Skin biopsy sample were histologically analyzed for connective tissue changes pre- and post-treatment. Data were analyzed statistically (α = 0.05). In the Active group: the collagen-occupied area at baseline was 1.12 ± 0.09 × 106 μm 2 and increased by +19.6% ( p < .001) at 1-month and by +26.3% ( p < .001) 2 months post-treatment; elastin-occupied area at baseline was 0.11 ± 0.03 × 106 μm 2 and increased by +75.9% ( p < .001) at 1-month and +110.8% ( p < .001) at 2-months follow-up. No significant changes ( p > .05) found in the Control samples. Collagen and elastin fiber content increased significantly after treatments. Connective tissue in the treatment area was denser up to 2-months post-treatment.

Cochlear Implantation in Inner Ear Malformations

Introduction: Cochlear Implantation (CI) has proven to be an effective treatment for severe bilateral Sensorineural Hearing Loss (SNHL). Inner ear malformation is a rare anomaly and occurs in approximately 20% of cases with congenital SNHL. There are particular challenges in the implantation of malformed cochleae, such as in cases of facial nerve anomalies, Cerebrospinal Fluid (CSF) leaks or facial stimulation, and the outcomes may differ depending on the severity of the malformation. The aim of this study was to assess the impact of Inner Ear Malformations (IEMs) on surgical complications and outcomes of cochlear implantation. Methods: Between 2018 and 2022, 9 patients with inner ear malformations were implanted in our department and completed at least 1 year of follow-up. The age range was between 2 years and 4 months and 5 years (average, 3.36 yr). Auditory performance, receptive and expressive language skills, and production and use of speech were evaluated preoperatively and at least 1 year after implantation. Results: In the study group, the most common malformation was an isolated Enlarged Vestibular Aqueduct (EVA) (55,5%). Overall, the patients with IEMs showed significant improvement in auditory-verbal skills. In general, the patients who had normal cochleae scored significantly better compared to patients with IEMs. Conclusion: Based on these findings, cochlear implantation is surgically feasible in patients with common cavity, IP types I and II, and EVA. The surgeon should be ready to make modifications in the surgical approach because of the abnormal course of the facial nerve and be ready to produce special precautions to cerebrospinal fluid gusher. Patients with EVA were the best performers in terms of auditory-verbal skills.

Unveiling Myasthenia Gravis: A Comprehensive Analysis of Diagnostic Tools and Clinical Insights

Objective: This research offers a comprehensive analysis of Myasthenia Gravis (MG), uncovering the remarkable accuracy of spinal accessory, ulnar, and facial nerve repetitive nerve stimulation (RNS), along with the precision of single fiber electromyography (SF-EMG) in MG diagnosis. We also embark on an exploration of clinical features and autoantibody test results in generalized MG patients.&#x0D; Methods: In this prospective study, we welcomed 31 individuals definitively diagnosed with generalized MG into our quest. The categorization of patients was conducted in accordance with the criteria set by the Myasthenia Gravis Foundation of America (MGFA). We examined patients' trapezius, nasalis, and abductor digiti minimi (ADM) muscles using RNS. We meticulously recorded the presence of MG autoantibodies, clinical subtypes based on affected muscle groups, and SF-EMG jitter rates.&#x0D; Results: The mean age of the 31 patients of whom 19 (61.3%) were male, was 64 ± 13.9 years. Among them, 20 showed positivity in the Anti-AChR antibody test. In 28 patients, accounting for 90.3% of the study group, single fiber electromyography (EMG) displayed increased jitter. There were 4 (12.9%), 24 (77.4%) and 12 (38.7%) patients featuring a decremental response of exceeding 10% in ADM, trapezius and nasalis muscles, respectivelyOur investigation revealed notable findings, such as the absence of substantial correlations between decremental response rates and age, gender, duration of complaints, antibody test results, thymus abnormalities, affected muscle types, familial history, or increased jitter rates in SF-EMG (p&gt;0.05).&#x0D; Conclusion: As our findings clearly show, we can confidently attest to the remarkable sensitivity of RNS in MG diagnosis when muscle selection is precise. A gem discovered on our study is the high sensitivity of the spinal accessory nerve, a revelation that should guide the course of routine RNS studies, particularly for those facing ocular-onset myasthenia.

Activation of α 2A and α 2B -adrenergic receptors inhibits tactile stimulation-evoked parallel fiber-Purkinje cell synaptic transmission in mouse cerebellar cortex.

The mechanism by which α2-adrenergic receptors (ARs) modulate the cerebellar parallel fiber-Purkinje cell (PF-PC) synaptic transmission is unclear. We investigated this issue using electrophysiological and neuropharmacological methods. Six- to eight-week-old ICR mice were used in the study. Under in vivo conditions, PF-PC synaptic transmission was evoked by facial stimulation of ipsilateral whisker pad, and recorded using cell-attached patch from PCs. Under in-vitro conditions, PF-PC synaptic transmission was evoked by electrical stimulation of the molecular layer in cerebellar slices, and was recorded using whole-cell recording from PCs. SR95531 (20 µM) was added to the ACSF during all recordings to prevent GABAA receptor-mediated inhibition. Air-puff stimulation of the ipsilateral whisker pad in-vivo evoked simple spike (eSS) firing of cerebellar PCs. Microapplication of noradrenaline (15 µM) to the molecular layer significantly decreased the numbers and frequency of eSS, an effect abolished by the α2-AR antagonist. Microapplication of an α2-AR agonist, UK14304 (1 µM), significantly decreased the numbers of eSS in PCs, which was abolished by either α2A- or α2B-AR antagonist, but not by α2C-AR antagonist. Under in-vitro conditions, application of UK 14304 significantly decreased the amplitude of PF-PC EPSCs and increased the paired-pulse ratio, which were abolished by either α2A- or α2B-AR antagonist. The present results indicate that activation of presynaptic α2A- and α2B-AR downregulates PF-PC synaptic transmission in mouse cerebellar cortex.

Sensorimotor integration in cranial muscles tested by short- and long-latency afferent inhibition

ObjectiveTo compressively investigate sensorimotor integration in the cranial-cervical muscles in healthy adults. MethodsShort- (SAI) and long-latency afferent (LAI) inhibition were probed in the anterior digastric (AD), the depressor anguli oris (DAO) and upper trapezius (UT) muscles. A transcranial magnetic stimulation pulse over primary motor cortex was preceded by peripheral stimulation delivered to the trigeminal, facial and accessory nerves using interstimulus intervals of 15-25 ms and 100-200 ms for SAI and LAI respectively. ResultsIn the AD, both SAI and LAI were detected following trigeminal nerve stimulation, but not following facial nerve stimulation. In the DAO, SAI was observed only following trigeminal nerve stimulation, while LAI depended only on facial nerve stimulation, only at an intensity suprathreshold for the compound motor action potential (cMAP). In the UT we could only detect LAI following accessory nerve stimulation at an intensity suprathreshold for a cMAP. ConclusionsThe results suggest that integration of sensory inputs with motor output is profoundly influenced by the type of sensory afferent involved and by the functional role played by the target muscle. SignificanceData indicate the importance of taking into account the sensory receptors involved as well as the function of the target muscle when studying sensorimotor integration, both in physiological and neurological conditions.

Hearing Performance in Cochlear Implant Users Who Have Facial Nerve Stimulation.

Introduction Facial nerve stimulation (FNS) is a complication in cochlear implant (CI) when the electrical current escapes from the cochlea to the nearby facial nerve. Different management to reduce its effects are available, although changes might result in a less-than-ideal fitting for the CI user, eventually reducing speech perception. Objective To verify the etiologies that cause FNS, to identify strategies in managing FNS, and to evaluate speech recognition in patients who present FNS. Methods Retrospective study approved by the Ethical Board of the Institution. From the files of a CI group, patients who were identified with FNS either during surgery or at any time postoperatively were selected. Data collection included: CI manufacturer, electrode array type, age at implantation, etiology of hearing loss, FNS identification date, number of electrodes that generated FNS, FNS management actions, and speech recognition in quiet and in noise. Results Data were collected from 7 children and 25 adults. Etiologies that cause FNS were cochlear malformation, head trauma, meningitis, and otosclerosis; the main actions included decrease in the stimulation levels followed by the deactivation of electrodes. Average speech recognition in quiet before FNS was 86% and 80% after in patients who were able to accomplish the test. However, there was great variability, ranging from 0% in quiet to 90% of speech recognition in noise. Conclusion Etiologies that cause FNS are related to cochlear morphology alterations. Facial nerve stimulation can be solved using speech processor programming parameters; however, it is not possible to predict outcomes, since results depend on other variables.

Facial and Cochlear Nerves Outcomes in the Surgical Resection of Giant Vestibular Schwannoma: Is There Any Predictive Value for Intraoperative Neuromonitoring of the Facial Nerve?

Background: Giant vestibular schwannoma (VS) represents one of the most challenging interventions in skull base surgery. Preserving facial and cochlear nerves requires effective surgical planning and nuanced techniques. Objectives: The present study evaluates the role of intraoperative neuromonitoring (IONM) in predicting the outcome of facial and cochlear nerves. Methods: This retrospective cohort comprised 34 patients with a giant (Samii IV/IVb grade) VS during 2016 - 2019. The retrosigmoid approach was used for tumor resection. Pre- and postoperative facial exams were graded according to the House-Brackmann Scale. Hearing ability was also classified according to the Hannover Hearing Classification. Intraoperative findings included the location of the nerve complex, tumor consistency, the surgical plane of the tumor from the facial nerve/ brainstem, and the level of internal auditory canal (IAC) decompression. Intraoperative neuromonitoring was used for all surgeries. The amplitude required for a positive response was recorded during the facial nerve's direct electrical stimulation (DES). All patients were followed 6 and 12 months postoperative. Results: The preoperative facial nerve function was normal in 91.2% of patients, and 8.8% had slight facial nerve impairment (FNI). Considering preoperative hearing status, 9 cases (26.5%) had moderate hearing loss or impairment, while 25 patients (73.5%) complained of severe hearing impairment. The mean intraoperative direct facial nerve stimulation threshold was 1.38 ± 0.89. Hearing impairment was moderately severe in 7 (20.6%) and severe in 25 patients (73.5%) postoperation. In addition, postoperative assessment revealed 13 (38.2%) cases with moderate FNI and 12 (35.2%) with moderately severe FNI. The tumor size did not affect the postoperative hearing loss, and the postoperative hearing loss did not improve significantly (P = 0.32). There was no statistically significant correlation between the intensity of intraoperative DES and postoperative facial nerve function (P &gt; 0.05). No significant correlation was observed between tumor consistency and postoperative hearing status (P &gt; 0.05). Conclusions: The retrosigmoid approach combined with IONM appears to be associated with favorable facial and cochlear nerve outcomes in giant VS. The postoperative facial nerve function may improve, but sensorineural hearing status may not improve significantly. Moreover, the intensity of intraoperative DES may not predict the postoperative facial function. Therefore, the findings of IONM should be interpreted carefully.

Cochlear Implant Stimulation Parameters Play a Key Role in Reducing Facial Nerve Stimulation.

A percentage (i.e., 5.6%) of Cochlear Implant (CI) users reportedly experience unwanted facial nerve stimulation (FNS). For some, the effort to control this problem results in changing stimulation parameters, thereby reducing their hearing performance. For others, the only viable solution is to deactivate the CI completely. A growing body of evidence in the form of case reports suggests that undesired FNS can be effectively addressed through re-implantation with an Oticon Medical (OM) Neuro-Zti implant. However, the root of this benefit is still unknown: is it due to surgical adjustments, such as varied array geometries and/or positioning, or does it stem from differences in stimulation parameters and/or grounding? The OM device exhibits two distinct features: (1) unique stimulation parameters, including anodic leading pulses and loudness controlled by pulse duration-not current-resulting in lower overall current amplitudes; and (2) unconventional grounding, including both passive (capacitive) discharge, which creates a pseudo-monophasic pulse shape, and a 'distributed-all-polar' (DAP) grounding scheme, which is thought to reduce current spread. Unfortunately, case reports alone cannot distinguish between surgical factors and these implant-related ones. In this paper, we present a novel follow-up study of two CI subjects who previously experienced FNS before re-implantation with Neuro-Zti implants. We used the Oticon Medical Research Platform (OMRP) to stimulate a single electrode in each subject in two ways: (1) with traditional monopolar biphasic cathodic-first pulses, and (2) with distinct OM clinical stimulation. We progressively increased the stimulation intensity until FNS occurred or the sound became excessively loud. Non-auditory/FNS sensations were observed with the traditional stimulation but not with the OM clinical one. This provides the first direct evidence demonstrating that stimulation parameters and/or grounding-not surgical factors-play a key role in mitigating FNS.