Percutaneous nerve evaluation based on electrode placement under control of autonomic innervation.

BACKGROUND: Foramen needle electrode placement for percutaneous nerve evaluation (PNE) is currently carried out while observing the somatic motor response. This study investigated electrode placement while observing the autonomic as well as the somatic response. METHODS: A consecutive series of ten patients (seven women) with a median age of 51.9 (range 30-75) years undergoing PNE for faecal incontinence (n = 6) and obstipation (n = 4) were investigated prospectively. Electrode placement was carried out under simultaneous electromyography (EMG) of the external anal sphincter (EAS) and internal anal sphincter (IAS) and cystomanometry. RESULTS: PNE under control of somatic and autonomic nerve responses was carried out in all patients. In three out of ten patients, initial needle electrode placement showed single evoked EMG signals from the EAS. Final electrode placement resulted in adequate somatic motor and autonomic responses in all patients. Comparison of the increases in IAS EMG amplitude on the right and left stimulation sites for sacral nerves S3 and S4 demonstrated significant differences [S3 right: median 15.3 (interquartile range (IQR) 10.4; 20.1) µV vs. S3 left: median 11.6 (IQR 8.6; 16.0) µV, p = 0.034 and S4 right: median 24.1 (IQR 20.1; 37.2) µV vs. S4 left: median 12.0 (IQR 10.7; 13.7) µV, p = 0.012]. Stimulation-induced bladder activation was achieved in all seven patients with concomitant urinary dysfunction. CONCLUSIONS: Control of not just the somatic motor response but also the autonomic nerve response during foramen needle electrode placement may objectify PNE.

Evaluation of two-dimensional intraoperative neuromonitoring for predicting urinary and anorectal function after rectal cancer surgery.

PURPOSE: The aim of this study was to compare the results of two-dimensional intraoperative neuromonitoring (IONM) with the postoperative urinary and anorectal function of rectal cancer patients. METHODS: A consecutive series of 35 patients undergoing low anterior resection were investigated prospectively. IONM was performed with electric stimulations of the pelvic splanchnic nerves under simultaneous manometry of the bladder and electromyography (EMG) of the internal anal sphincter (IAS). Urinary and anorectal function were evaluated preoperatively and at follow-up by standardized questionnaires, digital rectal examination scoring system, and long-term catheterization rate. RESULTS: The rate of postoperative newly developed bladder dysfunction was 17 %. IONM with bladder manometry had a sensitivity of 100 %, specificity of 96 %, positive predictive value of 83 %, negative predictive value of 100 %, and overall accuracy of 97 %, respectively. The proportion of patients with severely impaired anorectal function at follow-up was 8 %. The sensitivity, specificity, and positive and negative predictive values for IONM with EMG of the IAS were, respectively, 100, 96, 67, and 100 % with an accuracy of 96 %. The degree of agreement for IONM with EMG of the IAS was good for anorectal function (к = 0.780) and poor for urinary function (к = 0.119). IONM with bladder manometry yielded a very good degree of agreement for urinary function (к = 0.891) and a fair agreement for anorectal function (к = 0.336). CONCLUSIONS: The two-dimensional IONM method is suitable for verification of bladder and IAS innervation. Accurate prediction of urinary and anorectal function necessitates both bladder manometry and EMG of the IAS.

Continuous intraoperative monitoring of autonomic nerves during low anterior rectal resection: an innovative approach for observation of functional nerve integrity in pelvic surgery.

PURPOSE: The aim of this study was to develop a methodological setup for continuous intraoperative neuromonitoring with intent to improve nerve-sparing pelvic surgery. METHODS: Fourteen pigs underwent low anterior rectal resection. Continuous stimulation of pelvic autonomic nerves was carried out with a newly developed tripolar surface electrode during lateral, anterolateral, and anterior mesorectal dissection. Neuromonitoring was performed under electromyography of the autonomic innervated internal anal sphincter. RESULTS: Continuous neuromonitoring resulted in significantly increased electromyographic amplitudes of the internal anal sphincter, confirming intact innervation throughout the whole dissection in each animal (median 0.9 µV, interquartile range 0.5; 1.5 vs. median 3.4 µV, interquartile range 2.1; 4.7) (p < 0.001). The median dissection time in each animal was 10 min within a median number of ten (range 8-13) tripolar electric stimulations. CONCLUSION: The present study is the first to demonstrate that continuous intraoperative monitoring of pelvic autonomic nerves during low anterior rectal resection is feasible.

[Signal stability as key requirement for continuous intraoperative neuromonitoring]. / Signalstabilität als Grundvoraussetzung für kontinuierliches intraoperatives Neuromonitoring.

BACKGROUND: Postoperative recurrent laryngeal nerve (RLN) palsy is a well-known and dreaded complication of thyroid surgery. Continuous intraoperative neuromonitoring (CIONM) has been developed in order to provide an effective real-time surveillance of the RLN to its full extent and to detect subtle changes in nerve conductivity. A key requirement for a reliable interpretation of CIONM is signal stability. PATIENTS AND METHODS: In a prospective randomized controlled pilot study 24 patients corresponding to 30 nerves at risk (NaR) were included to compare a newly developed, flexible, saxophone-shaped backstrap electrode for vagal stimulation (16 NaR) to a commercially available CE-marked cylindrical and rigid electrode (14 NaR). Electrode applicability, safety and signal stability were analyzed by assessment of electrode implantation times, stimulation currents, EMG amplitudes and electrode displacement rates. RESULTS: Implantation and extraction was significantly faster and easier with the saxophone-shaped backstrap electrode. Accidental electrode displacement occurred up to eight times per operation when applying the cylindrical electrode, while a total of two displacements resulted using the backstrap electrode in this study. Stimulation currents necessary for supramaximal RLN stimulation were significantly lower using the newly developed electrode. At the same time, significantly greater stable EMG amplitudes resulted using the new saxophone-shaped electrode. No RLN palsy occurred during the study. CONCLUSIONS: According to the data, only the saxophone-shaped backstrap electrode provided the signal stability required for CIONM. The closed electrode geometry with isolated contacts for nerve stimulation and defined current entry provide the prerequisites required for reliable continuous intraoperative neuromonitoring.

Selective pelvic autonomic nerve stimulation with simultaneous intraoperative monitoring of internal anal sphincter and bladder innervation.

BACKGROUND: Pelvic autonomic nerve preservation avoids postoperative functional disturbances. The aim of this feasibility study was to develop a neuromonitoring system with simultaneous intraoperative verification of internal anal sphincter (IAS) activity and intravesical pressure. METHODS: 14 pigs underwent low anterior rectal resection. During intermittent bipolar electric stimulation of the inferior hypogastric plexus (IHP) and the pelvic splanchnic nerves (PSN), electromyographic signals of the IAS and manometry of the urinary bladder were observed simultaneously. RESULTS: Stimulation of IHP and PSN as well as simultaneous intraoperative monitoring could be realized with an adapted neuromonitoring device. Neurostimulation resulted in either bladder or IAS activation or concerted activation of both. Intravesical pressure increase as well as amplitude increase of the IAS neuromonitoring signal did not differ significantly between stimulation of IHP and PSN [6.0 cm H(2)O (interquartile range [IQR] 3.5-9.0) vs. 6.0 cm H(2)O (IQR 3.0-10.0) and 12.1 µV (IQR 3.0-36.7) vs. 40.1 µV (IQR 9.0-64.3)] (p > 0.05). CONCLUSIONS: Pelvic autonomic nerve stimulation with simultaneous intraoperative monitoring of IAS and bladder innervation is feasible. The method may enable neuromonitoring with increasing selectivity for pelvic autonomic nerve preservation.

Online signal processing of internal anal sphincter activity during pelvic autonomic nerve stimulation: a new method to improve the reliability of intra-operative neuromonitoring signals.

AIM: Intra-operative neuromonitoring is increasingly applied in several surgical disciplines and has been introduced to facilitate pelvic autonomic nerve preservation. Nevertheless, it has been considered a questionable tool for the minimization of risk, as the results are variable and might be misleading. The aim of the present experimental study was to develop an intra-operative neuromonitoring system with improved reliability for monitoring pelvic autonomic nerve function. METHOD: Fifteen pigs underwent low anterior rectal resection with pelvic autonomic nerve preservation. Intra-operative neuromonitoring was performed under autonomic nerve stimulation with observation of electromyographic signals of the internal anal sphincter and bladder manometry. As the internal anal sphincter frequency spectrum during stimulation was found to be mainly in the range of 5-20 Hz, intra-operative neuromonitoring signals were postoperatively processed by implementation of matching band pass filters. RESULTS: In 10 preliminary experiments, signal processing was performed offline in the postoperative analysis. Of 163 stimulations intra-operatively assessed by the surgeon as positive responses, 135 (83%) were confirmed after signal processing. In the following five consecutive experiments intra-operative online signal processing was realized and demonstrated reliable intra-operative neuromonitoring signals of internal anal sphincter activity with significant increase during pelvic autonomic nerve stimulation [0.5 µV (interquartile range = 0.3-0.7) vs 4.8 µV (interquartile range = 2.5-7.5); P < 0.001]. CONCLUSION: Online signal processing of internal anal sphincter activity aids reliable identification of pelvic autonomic nerves with potential for improvement of intra-operative neuromonitoring in pelvic surgery.

Neural prostheses and biomedical microsystems in neurological rehabilitation.

Interfaces between electrodes and the neural system differ with respect to material and shape depending on their intended application and fabrication method. This chapter will review the different electrode designs regarding the technological implementation and fabrication process. Furthermore this book chapter will describe electrodes for interfacing the peripheral nerves like cuff, book or helix as well as electrodes for interfacing the cortex like needle arrays. The implantation method and mechanical interaction between the electrode and the nervous tissue were taken into consideration. To develop appropriate microtechnological assembling strategies that ensure proper interfacing between the tiny electrodes and microelectronics or connectors is one of the major challenges. The integration of electronics into the system helps to improve the reliability of detecting neural signals and reduces the size of the implants. Promising results with these novel electrodes will pave the road for future developments such as visual prosthetics or improved control of artificial limbs in paralyzed patients.

Experiments on the development and use of a new generation of intra-neural electrodes to control robotic devices.

The development of interfaces linking the human nervous system with artificial devices is an important area of research and several groups are now addressing it. Interfaces represent the key enabling technology for the development of devices usable for the restoration of motor and sensory function in subjects affected by neurological disorders, injuries or amputations. For example, current hand prostheses use electromyographic (EMG) signals to extract volitional commands but this limits the possibility of controlling several degrees of freedom and of delivering sensory feedback. To achieve these goals, implantable neural interfaces are required. Among the candidate interfaces with the peripheral nervous system intra-neural electrodes seem to be an interesting solution due to their bandwidth and ability to access volition and deliver sensory feedback. However, several drawbacks have to be addressed in order to increase their usability. In this paper, experiments to address many of these issues are presented as part of the development of a new generation of intra-neural electrodes. The results showed seem to confirm that these new interfaces seem to have interesting properties and that they can represent a significant improvement of the state of the art. Extensive experiments will be carried out in the future to validate these results.

Neural prostheses in clinical applications--trends from precision mechanics towards biomedical microsystems in neurological rehabilitation.

Neural prostheses partially restore body functions by technical nerve excitation after trauma or neurological diseases. External devices and implants have been developed since the early 1960s for many applications. Several systems have reached nowadays clinical practice: Cochlea implants help the deaf to hear, micturition is induced by bladder stimulators in paralyzed persons and deep brain stimulation helps patients with Parkinson's disease to participate in daily life again. So far, clinical neural prostheses are fabricated with means of precision mechanics. Since microsystem technology opens the opportunity to design and develop complex systems with a high number of electrodes to interface with the nervous systems, the opportunity for selective stimulation and complex implant scenarios seems to be feasible in the near future. The potentials and limitations with regard to biomedical microdevices are introduced and discussed in this paper. Target specifications are derived from existing implants and are discussed on selected applications that has been investigated in experimental research: a micromachined implant to interface a nerve stump with a sieve electrode, cuff electrodes with integrated electronics, and an epiretinal vision prosthesis.

Considerations on noise of electrodes in combination with amplifiers for bioelectrical signal recording.

Detection of weak bioelectrical signals needs a recording system with a very low system noise. In this paper, the noise of electrodes as well as the influence of different combinations of electrodes and amplifiers on the system noise was investigated. As a first result the electrodes noise is similar to the noise of a passive electronic part with the same impedance. For smaller electrodes a reduction of the electrode impedance will reduce the system noise, also for larger electrodes the electrode itself is not the dominant noise source, so that an improvement of the amplifier is the way to get a better system. A special amplifier was tested with iridium and platinum black electrodes of different sizes.

[Coating material of parlene C as encapsulation material for biomedical micro-implants]. / Untersuchungen zur Abscheidung von Parylen C als Kapselungsmaterial für Biomedizinische Mikroimplantate.

Biomedical microsystems attain to contact with environments like blood, ephitHelium and saline solutions therefore they need an encapsulation. Parylene seems to be a suitable polymer to cover the implants and protect them against moisture and aggressive environment. This paper describes the characterisation of Parylene C coatings and its possibilities to protect implants. Beside the encapsulation of biomedical microsystems the manufacturing of fexible electrodes and the cytotoxicity behavior of RIE etched Parylene layers was investigated.