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There is a critical need to transition research level flexible polymer bioelectronics toward the clinic by demonstrating both reliability in fabrication and stable device performance. Conductive elastomers (CEs) are composites of conductive polymers in elastomeric matrices that provide both flexibility and enhanced electrochemical properties compared to conventional metallic electrodes. This work focuses on the development of nerve cuff devices and the assessment of the device functionality at each development stage, from CE material to fully polymeric electrode arrays. Two device types are fabricated by laser machining of a thick and thin CE sheet variant on an insulative polydimethylsiloxane substrate and lamination into tubing to produce pre-curled cuffs. Device performance and stability following sterilization and mechanical loading are compared to a state-of-the-art stretchable metallic nerve cuff. The CE cuffs are found to be electrically and mechanically stable with improved charge transfer properties compared to the commercial cuff. All devices are applied to an ex vivo whole sciatic nerve and shown to be functional, with the CE cuffs demonstrating superior charge transfer and electrochemical safety in the biological environment., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Objective: Electrical stimulation is a blunt tool for evoking neural activity. Neurons are naturally activated asynchronously and non-uniformly, whereas stimulation drives simultaneous activity within a population of cells. These differences in activation pattern can result in unintended side effects, including muddled sensory percepts and undesirable muscle contractions. These effects can be mitigated by the placement of electrodes in close approximation to nerve fibers and careful selection of the neural interface's location. This work describes the benefits of placing electrodes within specific fascicles of peripheral nerve to form selective neural interfaces for bidirectional neuroprosthetic devices., Approach: Chronic electrodes were targeted to individual fascicles of the ulnar and median nerves in the forearm of four human subjects. During the surgical implant procedure, fascicles were dissected from each nerve, and functional testing was used to identify the relative composition of sensory and motor fibers within each. FAST-LIFE arrays, composed of longitudinal intrafascicular arrays and fascicular cuff electrodes, were implanted in each fascicle. The location, quality, and stimulation parameters associated with sensations evoked by electrical stimulation on these electrodes were characterized throughout the 90-180 d implant period., Main Results: FAST-LIFE arrays enable selective and chronic electrical stimulation of individual peripheral nerve fascicles. The quality of sensations evoked by stimulation in each fascicle is predictable and distinct; subjects reported tactile and cutaneous sensations during stimulation of sensory fascicles and deeper proprioceptive sensations during stimulation of motor fascicles. Stimulation thresholds and strength-duration time constants were typically higher within sensory fascicles., Significance: Highly selective, stable neural interfaces can be created by placing electrodes within and around single fascicles of peripheral nerves. This method enables targeting electrodes to nerve fibers that innervate a specific body region or have specific functions. Fascicle-specific interfacing techniques have broad potential to maximize the therapeutic effects of electrical stimulation in many neuromodulation applications. (Clinical Trial ID NCT02994160.).

Background: Lead placement within the sacral foramen in sacral neuromodulation patients is guided by visual assessment of the contraction of the pelvic floor musculature (PFM) and/or verbal assessment of the sensation and location of sensation upon stimulation. Generally, lead placement is proceeded by needle probing. This study evaluates which location inside a single sacral foramen would be most ideal for the release of the permanent electrode lead, by measuring electromyographic (EMG) motor responses of the PFM upon stimulation of a peripheral nerve evaluation (PNE) needle., Materials and Methods: In eight patients, four standard PNE needles, and in one patient, two PNE needles, were introduced into the same foramen, parallel to the midline and parallel to each other. Position was verified by X-ray. Needles were stimulated (square pulsed waves, 210 μsec, 14 Hz) at increasing amplitudes (1-2-3-5-7-10 mA). PFM EMG was measured using the Multiple Array Probe (MAPLe) placed intravaginally or intrarectally, with 24 derivations. For this study, the mean (normalized) EMG was taken of all electrodes and different positions within the foramen were compared using the Wilcoxon signed rank test., Results: A total of 202 PFM EMG measurements were recorded upon stimulation. EMG motor responses of the PFM for current stimulation = <2 mA showed statistically significant higher mean (normalized) EMG values for needles positioned cranial, medial, and cranial-medial, in comparison to needles positioned caudal, lateral, and caudal-lateral (p = 0.004; p = 0.021; p = 0.002)., Conclusions: Our data suggest stronger PFM contractions are elicit in cranial- and medial-placed PNE needles upon stimulation with clinically relevant current amplitudes (≤ 2 mA). Placement of the lead should aim for this spot in the foramen., (© 2019 International Neuromodulation Society.)

Objectives: In rodents, we reported that short pulse-width (PW) neuromodulation might provide more efficient therapy delivery than traditional 0.21 msec PW. Using fully implanted, commercialized systems in the sheep, the goal of this study was to characterize the relationship of electromyographic (EMG) responses of the external anal sphincter (EAS) to different PWs of sacral neuromodulation (SNM)., Materials and Methods: In seven sheep, InterStim® quadripolar tined leads were implanted adjacent to the S3 nerve root bilaterally to deliver SNM and two pairs of intramuscular leads were placed on either side of the EAS for EMG sensing. The EMG responses to SNM with different PWs were examined using variable intensities in both anesthetized and conscious conditions., Results: The EMG responses from ipsilateral EAS (I EAS ) and contralateral EAS (C EAS ) were compared. The area under the curve of EMG responses from I EAS were significantly stronger than that from C EAS. The late component EMGs were more sensitive to nerve stimulation with a higher response amplitude in awake sheep. The response threshold-PW relationship from the I EAS as ascertained visually and with EMG in anesthetized and awake sheep were fitted with a monoexponential nonlinear regression; the resulting chronaxies were of 0.05 msec (n = 6), and 0.04 msec (n = 6), and 0.04 msec (n = 8), respectively., Conclusions: In both anesthetized and awake conditions, a similar motor response may be evoked in the EAS at PWs much shorter (0.04-0.05 msec) than the 0.21 msec typically used with SNM. Potential battery savings manifested by shorter PW would provide more efficient therapy delivery and increased longevity of the stimulator., (© 2018 International Neuromodulation Society.)

Purpose: This five-year, retrospective, multicenter study evaluated the long-term safety and efficiency of sacral neuromodulation (SNM) in Chinese patients with urinary voiding dysfunction., Patients and Methods: This is a Chinese national, multicenter, retrospective study that included 247 patients (51.2% female) who received an implantable pulse generator (IPG) (InterStim, Medtronic, Minneapolis, MN, USA) between 2012 and 2016. Success was considered if the initial ≥50% improvement in any of primary voiding diary variables persisted compared with baseline. The results were further stratified by identifying patients who showed >50% improvement and those although showed <50% improvement but still wanted to receive IPG; these data were collected and analyzed for general improvement., Results: Following test stimulation, 187 patients (43%) declined implantation and 247 (57%) underwent implantation using InterStim®. Among 247 patients, 34 (13.7%) had overactive bladder (OAB), 59 (23.8%) had interstitial cystitis/bladder pain syndrome (IC/BPS), 47 (19%) had idiopathic urinary retention (IUR), and 107 (44.1%) had neurogenic bladder (NB). IPG efficiency rate for OAB, interstitial cystitis/bladder pain syndrome, idiopathic urinary retention, and neurogenic bladder were 42.5, 72.4, 51.6, and 58.8%, respectively. The mean duration of follow-up was 20.1 ± 12.8 months., Conclusions: SNM appears effective in the long term, with a total IPG implantation rate of approximately 57% (ranging between 42.5 and 72.4% depending on indication). Interstitial cystitis/bladder pain syndrome appear to be the best indication for stage I testing. Chinese neurogenic bladder patients are most inclined to choose SNM. SNM is relatively safe, with low postoperation adverse events of 16.1% and reoperation rate of 3.2% during the follow-up period., (© 2019 International Neuromodulation Society.)

Objectives: Kilohertz high-frequency alternating current (KHFAC) electrical nerve stimulation produces a reversible nerve block in peripheral nerves in human patients with chronic pain pathologies. Although this stimulation methodology has been verified with nonselective extrafascicular electrodes, the effectiveness of producing a selective nerve block with more-selective intrafascicular electrodes has not been well documented. The objective of this study was to examine whether intrafascicular electrodes can block painful stimuli while preserving conduction of other neural activity within the implanted nerve., Materials and Methods: We analyzed the effects of various stimulation waveforms delivered through Utah Slanted Electrode Arrays (USEAs) implanted in the median nerve of a male human subject with a left brachial plexus injury. We compared KHFAC stimulation with a sham control., Results: KHFAC stimulation through USEA electrodes produced a reduction in pain sensitivity in the palmar aspect of the left middle finger. KHFAC had limited effects on the patient's ability to feel tactile probing in the same area or move the digits of his left hand. Other tested stimulation parameters either increased or showed no reduction in pain., Conclusions: KHFAC stimulation in peripheral nerves through intrafascicular electrodes demonstrated a selective reduction in pain sensitivity while preserving other nerve functions. This treatment may benefit patient populations who have chronic pain originating from peripheral nerves, but who do not want to block whole-nerve function in order to preserve sensory and motor function reliant on the implanted nerve. Furthermore, KHFAC may benefit patients who respond negatively to other forms of peripheral nerve stimulation therapy., (© 2018 International Neuromodulation Society.)

Objective: Previous studies suggest that somatosensory feedback has the potential to improve the functional performance of prostheses, reduce phantom pain, and enhance embodiment of sensory-enabled prosthetic devices. To maximize such benefits for amputees, the temporal properties of the sensory feedback must resemble those of natural somatosensation in an intact limb., Approach: To better understand temporal perception of artificial sensation, we characterized the perception of visuotactile synchrony for tactile perception restored via peripheral nerve stimulation. We electrically activated nerves in the residual limbs of two trans-tibial amputees and two trans-radial amputees via non-penetrating nerve cuff electrodes, which elicited sensations referred to the missing limbs., Main Results: Our findings suggest that with respect to vision, stimulation-induced sensation has a point of subjective simultaneity (PSS; processing time) and just noticeable difference (JND; temporal sensitivity) that are similar to natural touch. The JND was not significantly different between the participants with upper- and lower-limb amputations. However, the PSS indicated that sensations evoked in the missing leg must occur significantly earlier than those in the hand to be perceived as maximally synchronous with vision. Furthermore, we examined visuotactile synchrony in the context of a functional task during which stimulation was triggered by pressure applied to the prosthesis. Stimulation-induced sensation could be delayed up to 111  ±  62 ms without the delay being reliably detected., Significance: The quantitative temporal properties of stimulation-induced perception were previously unknown and will contribute to design specifications for future sensory neuroprostheses.

Sacral neuromodulation is an effective treatment of urinary incontinence, fecal incontinence, and idiopathic urinary retention. The procedure is considered low risk with overall low complication rates. This report describes a 40-year-old woman who underwent sacral neuromodulation explant and full-system implant for weaning efficacy of her device. During device removal, the tined lead broke and was left in situ. Four months later, she was diagnosed as having a wound infection at the site of the retained lead. Imaging revealed lead fragment migration into the sigmoid colon. A colocutaneous fistula was noted soon thereafter. The retained lead was removed during a colonoscopy and the fistula healed. A retained lead can result in migration through the peritoneum and into the colon. This can be managed with assistance from colorectal or gastroenterology consultants.

Objective: Numerical simulation and animal experiments quantified tissue temperatures during the transcutaneous recharge of neuromodulation implants. The temperature results were used to determine the likelihood of tissue injury in humans., Materials and Methods: Experiments were completed using sheep with implants at different depths ranging from 0.7 to 2.15 cm. The calculations were replicates of the experiments. Additional calculations were completed for laterally offset implants (up to 2 cm). Benchtop tests were performed to determine the power dissipation in the components. These power dissipation rates were inputs to the simulation. The now-verified model was next applied to a human situation with a core temperature of 37°C., Results: There was excellent agreement between the simulations and the animal-model for all depths; the experimental and simulated temperatures near the implant were almost identical. The results were negligibly affected by a misalignment of the implant. The maximum experimental temperatures in the sheep were 41.8, 43.2, and 41.8°C while the calculated maxima were 41.9, 43.3, and 41.2°C for the shallow, medium, and deep cases, respectively. The experimental values are 3.1, 4.5, and 3.1°C above the body core temperature. The simulation results are 3.2, 4.6, and 2.5°C above the core temperature. The model was then applied to a human situation with a body core temperature of 37°C. The maximum values of the simulated temperatures are 39.9, 41.2, and 39.1°C. The cumulative equivalent exposure at 43°C (CEM43) for these three implant depths are 0.30, 0.88, and 0.12 min. These thermal exposures are below those known to cause thermal injury in human skin tissue., Conclusions: The numerical simulation predicts tissue temperatures during transcutaneous recharge of implants. Results show that the implant depth does not have a large impact on the tissue temperatures and thermal exposures are sufficiently low so that they are unlikely to have any physiologic consequence., (© 2017 International Neuromodulation Society.)

Purpose: This study was designed to investigate the safety and performance of a new implantable system for tibial nerve stimulation for overactive bladder symptoms., Materials and Methods: A battery-free stimulation device for tibial nerve stimulation (BlueWind Medical, Herzliya, Israel) was implanted in 15 patients. Safety and efficacy assessments were done at 3 months after activation with a 3-day bladder diary, a 24-hour pad test and 2 quality of life questionnaires., Results: Two males and 13 females were enrolled in the study. Mean age was 54 years (range 19 to 72). Five of 15 patients were previously treated with percutaneous tibial nerve stimulation and 12 experienced urgency urinary incontinence. Median operative time was 34 minutes. At 3 months of followup a significant change was seen in 24-hour frequency from a mean ± SD of 11.8 ± 3.5 to 8.1 ± 2.0 times per day (p = 0.002), the number of severe urinary urgency episodes from 6.5 ± 5.1 to 2.0 ± 2.1 times per day (p = 0.002), the number of severe incontinence episodes from 2.8 ± 5.2 to 0.3 ± 0.4 episodes per day (p = 0.017), urinary loss per day from 243 ± 388 to 39 ± 55 gm (p = 0.038) and improvement in quality of life. After implantation, 3 patients received prolonged antibiotic treatment and 3 received pain medication for 1 week. In 1 patient the device was explanted due to pain and swelling suspicious for infection, although tissue cultures did not reveal a bacterial infection., Conclusions: This novel posterior tibial nerve stimulator is safe and easy to implant with good clinical results., (Copyright © 2017 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.)

Introduction: The field of neuromodulation continues to grow, especially in the area of pain management. Percutaneous nerve field stimulation continues to gain significant popularity for chronic, focal, and intractable neuropathic pain., Materials and Methods: Tuohy needles have been traditionally used as the instrument of choice for subcutaneous implantation of peripheral field stimulators. The ON-Q® Tunneling System (Braun Melsungen AG, Melsungen, Germany) provides an adaptable option for subcutaneous implantation of electrodes, with a variety of lengths and gauges available. This system uses a disposable blunt needle and a peel-away sheath and is firm but malleable. Gentle curves can be applied to the stylet prior to implantation. The blunt, malleable nature of the needle and the soft Silastic sheath allow for applications in areas with greater curvature, such as the face, and ensure a subcutaneous placement., Conclusions: The great adaptability of this system allows for implantation of electrodes subcutaneously with efficacy and ease. Here we present a technical note on the use of this system for subcutaneous implantation of peripheral nerve field stimulators., (© 2014 International Neuromodulation Society.)

Objective: In this study, we analyze device- and procedure-related adverse events (AEs) from a recent prospective, multicenter, double-blinded controlled study that utilized peripheral nerve stimulation (PNS) of occipital nerves for management of chronic migraine., Methods: PNS device characteristics (lead length and spacing), surgical techniques including lead orientation (parallel or perpendicular to the nerve), and implantable pulse generator (IPG) placement (upper buttock, abdomen, infraclavicular, or lower axilla) in 157 patients were analyzed to identify any relationship with the AE incidence rate. Number of prior PNS implants performed (NPPIP) by the implanter and its relationship with different AE categories (hardware-related, biological, and stimulation-related events) and frequently observed device/procedure-related AEs (lead migration/fracture/breakage, persistent pain at the lead/IPG location, unintended/undesirable changes in stimulation, infection) were also evaluated. Three-way ANOVA tests were utilized to evaluate the dependence of AE occurrence on the variables described above., Results: IPG pocket locations closer to the lead (e.g. infraclavicular region) were associated with a lower AE incidence rate (p < 0.05). Higher NPPIP was related to lower stimulation- and hardware-related AEs (p < 0.05), frequently observed AEs like lead migration, pain, and infection (p < 0.05), and procedure-related additional surgeries (p < 0.05)., Conclusion: Implantation of the IPG closer to the lead location was associated with reduced AEs. PNS is a relatively new procedure, and the skill and precision in performing these procedures improves with experience. Our results demonstrate that as the implanter gains more experience with these procedures, a significant reduction in device- and procedure-related AEs may be expected., (© 2014 International Neuromodulation Society.)

Tinnitus, as a phantom sound can express itself as a pure tone and as a noise-like sound. It is notoriously difficult to treat, and in medically, psychologically and audiologically intractable tinnitus patients sometimes intracranial electrodes overlying the auditory cortex are implanted. In this case report, we describe a patient who had a complete resolution of the pure tone component of his tinnitus by an auditory cortex implant, without any beneficial effect on the noise-like aspect of his tinnitus, even after changing the stimulation design to burst stimulation, which is known to treat noise-like tinnitus better than tonic stimulation. After an initial successful treatment of his noise-like component with transcutaneus electrical nerve stimulation, a wire electrode is inserted subcutaneously and connected to his internal pulse generator. With the dual stimulation his pure tone tinnitus remains abolished after 5 years of stimulation and his noise-like tinnitus is improved by 50%, from 8/10 to 4/10. This case report suggests that multi-target stimulation might be better than single target implantation in selected cases., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Electrical stimulations of neuronal structures must ensure net injected charges to be zero for biological safety and voltage compliance reasons. We present a novel architecture of general purpose biphasic constant current stimulator that exhibits less than 5.6 fC error while injecting 140 nC charges using 1.4 mA currents. The floating current sources and conveyor switch based system can operate in monopolar or bipolar modes. Anodic-first or cathodic-first pulses with optional inter-phase delays have been demonstrated with zero quiescent current requirements at the analog front-end. The architecture eliminates blocking capacitors, electrode shorting and complex feedbacks. Bench-top and in-vivo measurement results have been presented with emulated electrode impedances (resistor-capacitor network), Ag-AgCl electrodes in saline and in-vivo (acute) peripheral nerve stimulations in anesthetized rats.

Objective: The use of multiple cylindrical leads and multicolumn and single column paddle leads in spinal cord stimulation offers many advantages over the use of a single cylindrical lead. Despite these advantages, placement of multiple cylindrical leads or a paddle lead requires a more invasive surgical procedure. Thus, the ideal situation for lead delivery would be percutaneous insertion of a paddle lead or multiple cylindrical leads. This study evaluated the feasibility and safety of percutaneous delivery of S-Series paddle leads using a new delivery device called the Epiducer lead delivery system (all St. Jude Medical Neuromodulation Division, Plano, TX, USA)., Materials and Methods: This uncontrolled, open-label, prospective, two-center study approved by the AZ St. Lucas (Ghent) Ethics Committee evaluated procedural aspects of implantation of an S-Series paddle lead using the Epiducer lead delivery system and any adverse events relating to the device. Efficacy data during the patent's 30-day trial also were collected., Results:   Data from 34 patients were collected from two investigational sites. There were no adverse events related to the Epiducer lead delivery system. The device was inserted at an angle of either 20°-30° or 30°-40° and was entered into the epidural space at T12/L1 in most patients. The S-Series paddle lead was advanced four vertebral segments in more than 50% of patients. The average (±standard deviation [SD]) time it took to place the Epiducer lead delivery system was 8.7 (±5.0) min. The average (+SD) patient-reported pain relief was 78.8% (+24.1%)., Conclusions: This study suggests the safe use of the Epiducer lead delivery system for percutaneous implantation and advancement of the S-Series paddle lead in 34 patients., (© 2012 International Neuromodulation Society.)

Background: In spinal cord stimulation (SCS) mainly 2 distinctive implantation techniques can be recognized: the percutaneous and surgical technique., Material and Methods: A puncture is made with a blunt 14 gauge Tuohy needle. Once inside the epidural space the guide wire needs to be advanced in the epidural space, then the Tuohy needle is removed. The Epiducer is advanced under the guidance of lateral fluoroscopy, to confirm epidural entry. The S-series electrode is introduced through the sheet in the epidural space., Conclusion: We present a novel technique to introduce small profile paddle leads (S-Series™: St. Jude Medical - Neuromodulation Division, Plano, TX) in the epidural space via a percutaneous approach using the Epiducer™ (St. Jude Medical - Neuromodulation Division, Plano, TX) lead delivery system., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: In spinal cord stimulation for the management of chronic, intractable pain, a satisfactory analgesic effect can be obtained only when the stimulation-induced paresthesias cover all painful body areas completely or partially., Objective: To investigate the effect of stimulus pulse width (PW) and contact configuration (CC) on the area of paresthesia (PA), perception threshold (VPT), discomfort threshold (VDT), and usage range (UR) in spinal cord stimulation., Methods: Chronic pain patients were tested during a follow-up visit. They were stimulated monopolarly and with the CC giving each patient the best analgesia. VPT, VDT, and UR were determined for PWs of 90, 210, and 450 microseconds. The paresthesia contours at VDT were drawn on a body map and digitized; PA was calculated; and its anatomic composition was described. The effects of PW and CC on PA, VPT, VDT, and UR were tested statistically., Results: Twenty-four of 31 tests with low thoracic stimulation and 8 of 9 tests with cervical stimulation gave a significant extension of PA at increasing PW. In 14 of 18 tests (low thoracic), a caudal extension was obtained (primarily in L5-S2). In cervical stimulation the extension was predominantly caudal as well. In contrast to VPT and VDT, UR is not significantly different when stimulating with any CC., Conclusion: PA extends caudally with increasing PW. The mechanism includes that the larger and smaller dorsal column fibers have a different mediolateral distribution and that smaller dorsal column fibers have a smaller UR and can be activated only when PW is sufficiently large. A similar effect of CC on PA is unlikely as long as electrodes with a large intercontact distance are applied.

Objective: The placement of a percutaneous electrode for trial stimulation to evaluate the effectiveness of spinal cord stimulation can be impossible because of epidural adhesions from previous spinal surgeries. The authors would like to describe a combination of techniques in order to place a percutaneous lead for a test phase., Materials and Methods: Technical report of an illustrative case where a partial laminectomy was used to assist a percutaneous lead placement., Results: Adequate trial spinal cord stimulation with a single lead electrode at the right target area was possible., Conclusion: This case demonstrates the possibility to use a combination of an open and percutaneous technique for trial spinal cord stimulation in patients with prior operations in the target area of stimulation., (© 2010 International Neuromodulation Society.)

This article describes a new powering system for implantable medical devices that could significantly increase their lifetime. The idea is based on the substitution of the usual implantable device battery for an electric accumulator (rechargeable battery), which is fed by the electric power generated by a photovoltaic converter inside the implantable device. Light impinges on the photovoltaic device through an optical fiber going from the photovoltaic device to just beneath the patient's epidermis. Light can enter the optical fiber by passing through the skin. A complete power-by-light system has been developed and tested with a real implantable pulse generator for spinal cord stimulation. The feasibility of the proposed system has been evaluated theoretically. For example, after 13 h/week of laser exposure, the lifetime of the implantable device would increase by 50%. Other combinations resulting in lifetime increases of more than 100% are also possible. So, the proposed system is now ready to take a further step forward: in vivo animal testing.

Background and Aim: Sacral nerve stimulation is the therapy of choice in patients with neurogenic faecal and urine incontinence, constipation and some pelvic pain syndromes. The aim of this study is to determine the best insertion angles of the electrode under laparoscopic visualization of the sacral nerves., Materials and Methods: Five fresh cadaver pelvises were dissected through an anterior approach of the presacral space, exposing the ventral sacral roots. Needles and electrodes were inserted into the S3 foramen. Both right and left sides were used, with the traditional percutaneous procedure. The validation was done by a laparoscopic camera controlling the position of the needle and electrode on the nerve. The angles were assessed with a goniometer and were confirmed in two living patients., Results: The mean angle of insertion in the sagittal plane was 62.9+/-3 degrees (range, 59-70). In the axial plane, the mean angle for the left side was 91.7+/-13.5 degrees (range, 80-110) and 83.2+/-7.7 degrees for the right side (range, 75-95). These angles resulted in the optimal placement of the leads along the S3 sacral root, in all these cases., Conclusions: This study allows direct visualization during the placement of the needle and electrode, thus permitting accurate calculations of the best angle of approach during the surgical procedure in sacral nerve stimulation. These objective findings attempt to standardize this technique, which is often performed with the aid of intra-operative fluoroscopy but still leaving a lot to chance. These insertion angles should help to find more consistent and reproducible results and thus improved outcome in patients.

Patients with bilateral total deafness due to lesions of the vestibulocochlear nerve can be treated by electrical stimulation of the second auditory neuron. A 22-channel multi-electrode implant with transcutaneous transmission was developed that allows the selection of the most useful electrodes. Acoustic neuromas were removed from 49 out of 58 patients by ENT surgeons and neurosurgeons working in collaboration and using either a translabyrinthine or suboccipital approach. The central electroauditory prosthesis was implanted in the same procedure. Six patients were deaf after previous acoustic neuroma surgery without recurrence, three had diagnoses other than neurofibromatosis type 2 (NF2). There were no complications due to the implantation procedure. Side effects could be excluded by stimulation of the auditory electrodes alone. Most of the patients used their ABI daily. They reported perception of different sounds and frequencies, enhancement of lip-reading ability, and three of the patients were able to use the telephone.

The posterior tibial nerves of 18 rabbits were intraneurally implanted with coiled wire electrodes for up to 9 weeks to evaluate their usefulness for neuromuscular electrical stimulation. In one group an electrode was implanted and removed in one leg while the other leg was chronically implanted. A second group was chronically implanted without electrical stimulation in one leg and implanted with cyclical electrical stimulation applied through the electrode in the other leg. No significant changes in nerve conduction velocities between the time of implantation and up to 9 weeks post-implantation were observed in either the stimulated or the non-stimulated nerves. Little change in motor current threshold was observed beyond 10 days post-implantation. The nerves showed little or no histologic demyelination or denervation in most specimens, although in about 40% of the nerves, a bulbous formation of connective tissue was observed at electrode entry and exit sites with some demyelination in these regions. The spinal cords showed no histologic abnormalities in either group. The gastrocnemius and soleus muscles showed only occasional signs of denervation. One cat was implanted in both the posterior tibial and peroneal nerves of each leg for a 4-year period. Threshold current showed very little change during the implantation period. The nerves showed minimal focal demyelination at the electrode site and the muscles showed normal fibers.