Endoscopic laryngeal patterns in vagus nerve stimulation therapy for drug-resistant epilepsy

Delayed vagal nerve compressive neuropathy following placement of vagal nerve stimulator: case report

Vagal neuropathy causing vocal fold palsy is an uncommon complication of vagal nerve stimulator (VNS) placement. It may be associated with intraoperative nerve injury or with device stimulation. Here we present the first case of delayed, compressive vagal neuropathy associated with VNS coil placement which presented with progressive hoarseness and vocal cord paralysis. Coil removal and vagal neurolysis was performed to relieve the compression. Larger 3 mm VNS coils were placed for continuation of therapy. Coils with a larger inner diameter should be employed where possible to prevent this complication. The frequency of VNS-associated vagal nerve compression may warrant further investigation.

Integrated, Transparent Silicon Carbide Electronics and Sensors for Radio Frequency Biomedical Therapy

The integration of micro- and nanoelectronics into or onto biomedical devices can facilitate advanced diagnostics and treatments of digestive disorders, cardiovascular diseases, and cancers. Recent developments in gastrointestinal endoscopy and balloon catheter technologies introduce promising paths for minimally invasive surgeries to treat these diseases. However, current therapeutic endoscopy systems fail to meet requirements in multifunctionality, biocompatibility, and safety, particularly when integrated with bioelectronic devices. Here, we report materials, device designs, and assembly schemes for transparent and stable cubic silicon carbide (3C-SiC)-based bioelectronic systems that facilitate tissue ablation, with the capability for integration onto the tips of endoscopes. The excellent optical transparency of SiC-on-glass (SoG) allows for direct observation of areas of interest, with superior electronic functionalities that enable multiple biological sensing and stimulation capabilities to assist in electrical-based ablation procedures. Experimental studies on phantom, vegetable, and animal tissues demonstrated relatively short treatment times and low electric field required for effective lesion removal using our SoG bioelectronic system. In vivo experiments on an animal model were conducted to explore the versatility of SoG electrodes for peripheral nerve stimulation, showing an exciting possibility for the therapy of neural disorders through electrical excitation. The multifunctional features of SoG integrated devices indicate their high potential for minimally invasive, cost-effective, and outcome-enhanced surgical tools, across a wide range of biomedical applications.

Stridor Related to Vagus Nerve Stimulator: A Case Report

Implantation of a vagus nerve stimulator (VNS) can be an effective treatment for medically refractory seizures. Laryngeal side effects from a VNS can include hoarseness, cough, and shortness of breath. This report highlights a 5-year-old female who presented with stridor in the setting of acquired laryngomalacia, global developmental delay, and a VNS device. The case demonstrates that a VNS can exacerbate the symptoms of acquired laryngomalacia and that close monitoring of laryngeal side effects is crucial to optimizing care in this population. Laryngoscope, 131:E1733-E1734, 2021.

Pharyngolaryngeal spasm-induced dysphagia in an epileptic patient undergoing vagus nerve stimulation therapy

Vagus nerve stimulation for refractory epilepsy may induce laryngeal side effects such as dysphonia and dysphagia. Careful tuning of the stimulation parameters and collaboration between epileptologists and otolaryngologists can help significantly reduce side effects.

Behavioral Management of Laryngeal Complaints Caused by Vagal Nerve Stimulation for Medically Refractory Epilepsy

OBJECTIVES/HYPOTHESIS

This study investigated behavioral management of dysphonia and laryngeal dyspnea secondary to use of vagal nerve stimulation (VNS) in an individual with medically refractory epilepsy.

STUDY DESIGN

Retrospective chart review.

METHODS

Medical records from a single patient were reviewed. The patient received treatment with the speech-language pathologist (SLP) and laryngologist to observe patterns of laryngeal hyperfunction using biofeedback, and treatment with the SLP to learn to perform rescue breathing techniques, relaxation techniques, and awareness of muscle tension to aid the control of symptoms during activation. Data collected included neurology and laryngology notes. Neurology notes were used to track VNS settings, tolerance, and incidence of seizures. Laryngology notes included documentation of diagnosis, treatment, and measures of patient perception of severity (ie, Voice Handicap Index, Dyspnea Index, Cough Severity Index).

RESULTS

Prior to treatment, the patient was unable to receive benefits from VNS due to severe laryngeal adverse effects, such that the device remained off for eight months postimplantation. Following treatment, the patient effectively managed laryngeal side effects and was able to tolerate increases in VNS output current, signal frequency, and duration.

CONCLUSIONS

Voice therapy was effective in managing changes in vocal fold mobility and laryngeal tension. As the number of individuals receiving VNS for epilepsy and inflammatory conditions increases, the SLP and laryngologist may play a key role in interdisciplinary management of laryngeal side effects secondary to vagal nerve stimulation.

Vagus Nerve Stimulation-Induced Laryngeal Motor Evoked Potentials: A Possible Biomarker of Effective Nerve Activation

Vagus nerve stimulation (VNS) therapy is associated with laryngeal muscle activation and induces voice modifications, well-known side effects of the therapy resulting from co-activation of the recurrent laryngeal nerve. In this study, we describe the non-invasive transcutaneous recording of laryngeal motor evoked potentials (LMEPs), which could serve as a biomarker of effective nerve activation and individual titration in patients with drug-resistant epilepsy. We recruited drug-resistant epileptic patients treated for at least 6 months with a VNS. Trains of 600-1200 VNS pulses were delivered with increasing current outputs. We placed six skin electrodes on the ventral surface of the neck, in order to record LMEPs whenever the laryngeal muscular threshold was reached. We studied the internal consistency and the variability of LMEP recordings, and compared different methods for amplitude calculation. Recruitment curves were built based on the stimulus-response relationship. We also determined the electrical axis of the LMEPs dipole in order to define the optimal electrode placement for LMEPs recording in a clinical setting. LMEPs were successfully recorded in 11/11 patients. The LMEPs threshold ranged from 0.25 to 1 mA (median 0.50 mA), and onset latency was between 5.37 and 8.77 ms. The signal-to-noise ratio was outstanding in 10/11 patients. In these cases, excellent reliability (Intraclass correlation coefficient, ICC > 0.90 across three different amplitude measurements) was achieved with 10 sample averages. Moreover, our recordings showed very good internal consistency (Cronbach's alpha > 0.95 for 10 epochs). Area-under-the-curve and peak-to-peak measurement proved to be complementary methods for amplitude calculation. Finally, we determined that an optimal derivation requires only two recording electrodes, aligned on a horizontal axis around the laryngeal prominence. In conclusion, we describe here an optimal methodology for the recording of VNS-induced motor evoked responses from the larynx. Although further clinical validation is still necessary, LMEPs might be useful as a non-invasive marker of effective nerve activation, and as an aid for the clinician to perform a more rational titration of VNS parameters.

Neurological results of the modified treatment of epilepsy by stimulation of the vagus nerve

INTRODUCTION

The vagus nerve stimulation (VNS) is used for treatment of drug-resistant epilepsy but laryngeal side effects are common. We tried to improve VNS by modifying the implantation procedure. The aim was to reduce the rate of side effects that have prevented using VNS to its full capacity.

METHODS

We operated on 74 pediatric patients for VNS device implantation using a modified surgical protocol incorporating lower neck incision for electrode placement and 36 patients who were operated by standard technique were used for control group. We retrospectively analyzed reduction in frequency of seizures, reduction in severity of seizures (assessed by the shortened Ictal/post-ictal subscale of the Liverpool Seizure Severity Scale that included falling to the ground, postictal headache and sleepiness, incontinence, tongue biting, and injury during attack).

RESULTS

Using the new implantation technique, side effects related directly to VNS therapy occurred in six cases (8.1%) showing statistically sound improvement over the standard implantation technique (p ˂ 0.05). To achieve good results, the maximum stimulation (3.5 mA) was used in 24 patients (32.4%), with no laryngeal side effects detected. Twelve patients (16.2%) were seizure-free after the first year of VNS treatment. 74.3% of patients experienced a 50% reduction in seizure frequency and improved ictal or postictal activity.

CONCLUSION

To minimize laryngeal complications in implantation surgery for VNS devices, the surgical technique may be modified, and lower neck incision could be used. A low rate of laryngeal side effects allows using the VNS device to its full electrical capacity.

Impact of Vagal Nerve Stimulation on Objective Vocal Quality, a Pilot Study

OBJECTIVE

The purpose of this study was to determine the impact of vagal nerve stimulation (VNS) on the vocal quality using the dysphonia severity index (DSI). It was hypothesized that the objective vocal quality and other vocal characteristics are disordered in comparison with an age- and gender-matched control group. In addition, the acoustic vocal parameters were compared during three conditions: at rest, during normal stimulation, and raised stimulation. A significant relation between the amount of stimulation and the presence of disturbed acoustic parameters was hypothesized.

METHODS

Subjective (auditory-perceptual evaluation and voice handicap index) and objective (aerodynamic, vocal range, acoustic measurements and determination of the DSI) measurements were used to determine the vocal quality in 13 subjects with VNS in three different conditions (at rest and during normal and raised stimulation) and the age- and gender-matched control group.

RESULTS

The subjects with VNS had a disordered perceptual vocal quality mainly characterized by the presence of a moderate roughness and slight breathiness, and the objective vocal quality by means of the DSI value is -2.4. During stimulation and especially during raised stimulation, the fundamental frequency is significantly increased. However, the subjects experienced no psychosocial handicapping effect of the vocal quality on the quality of life.

CONCLUSIONS

Subjects with VNS have typical vocal characteristics. Ear, nose, and throat specialists and voice therapist must be aware of the presence of this vocal pattern at rest and during normal and raised stimulation. Especially, professional voice users and elite vocal performers must be informed before implantation.

Treatment of epilepsy by stimulation of the vagus nerve from Head-and-Neck surgical point of view

OBJECTIVES/HYPOTHESIS

The current article is dedicated to the surgical aspect of the vagus nerve stimulation (VNS) and our efforts to improve the surgical technique. The aim was to reduce the side effect/surgical complication rate as well as the time needed for this surgery.

STUDY DESIGN

A case series.

METHODS

The surgical data of 72 consecutive patients (age 4-14) who were operated for VNS device implantation from 2007 to 2014 were collected and analyzed. We designed the new surgical protocol that was implemented in all 72 cases and analyzed postsurgical side effects/complication rates. This protocol suggests low neck incision, detecting the vagus between the heads of the sternocleidomastoid muscle, a submuscular pocket for the device, and a short tunnel between it and the vagus electrodes.

RESULTS

The implantation took about 40 minutes; 4.2% of the patients (n = 3) were afflicted by complications related to surgery; and one patient (1.4%) suffered from hardware malfunctions. Side effects related to VNS therapy itself occurred in seven cases (6.9%).

CONCLUSION

To minimize laryngeal complications in implantation surgery for VNS devices, the surgical technique should be significantly modified, and lower neck incision could be implemented together with a submuscular pocket for the battery.

LEVEL OF EVIDENCE

4.