The Non-linear Electrical Properties of Silver/silver Chloride Electrodes in Sodium Chloride Solution.

An electrical measurement is non-linear when it is affected by the applied stimulus, i.e. when the measured phenomenon changes with amplitude. If pinched hysteresis loops can be observed in the voltage current representation, the underlying tissue can be classified as a memristor. Several biological memristors have been published, like human skin and apples. However, changes in the polarization impedance of electrodes may also cause pinched hysteresis loops. The question whether the reported biological memristors are real or whether the results just reflect changes in the polarization impedance arises. If the impedance of the measured object is close to or smaller than the polarization impedance of the used electrodes, the latter may dominate the measurement. In this study, we investigated the non-linear electrical properties of silver/silver chloride electrodes in a sodium chloride solution that has a similar concentration as human sweat and compared these to results from human skin. First of all, we found that silver/silver chloride electrodes in sodium chloride solution can be classified as memristors. However, the currents obtained from the sodium chloride solution are much higher than the currents recorded from human skin and there is a qualitative difference in the pinched hysteresis loops in both cases. We can conclude that the non-linear electrical measurements with silver/silver chloride on human skin are actually dominated by the skin and we can confirm that the human skin memristor really exists.

Accelerated Internal Auditory Canal Screening Magnetic Resonance Imaging Protocol With Compressed Sensing 3-Dimensional T2-Weighted Sequence.

BACKGROUND AND PURPOSE: High-resolution T2-weighted sequences are frequently used in magnetic resonance imaging (MRI) studies to assess the cerebellopontine angle and internal auditory canal (IAC) in sensorineural hearing loss patients but have low yield and lengthened examinations. Because image content in the Wavelet domain is sparse, compressed sensing (CS) that uses incoherent undersampling of k-space and iterative reconstruction can accelerate MRI acquisitions. We hypothesized that an accelerated CS T2 Sampling Perfection with Application optimized Contrasts using different flip angle Evolution (SPACE) sequence would produce acceptable diagnostic quality for IAC screening protocols. MATERIAL AND METHODS: Seventy-six patients underwent 3 T MRI using conventional SPACE and a CS T2 SPACE prototype sequence for screening the IACs were identified retrospectively. Unilateral reconstructions for each sequence were separated, then placed into mixed folders for independent, blinded review by 3 neuroradiologists during 2 sessions 4 weeks apart. Radiologists reported if a lesion was present. Motion and visualization of specific structures were rated using ordinal scales. McNemar, Wilcoxon, Cohen κ, and Mann-Whitney U tests were performed for accuracy, equivalence, and interrater and intrarater reliability. RESULTS: T2 SPACE using CS reconstruction reduced scan time by 80% to 50 seconds and provided 98.7% accuracy for IAC mass detection by 3 raters. Radiologists preferred conventional images (0.7-1.0 reduction on 5-point scale, P < 0.001), but rated CS SPACE acceptable. The 95% confidence for reduction in any cerebellopontine angle, IAC, or fluid-filled inner ear structure assessment with CS SPACE did not exceed 0.5. CONCLUSIONS: Internal auditory canal screening MRI protocols can be performed using a 5-fold accelerated T2 SPACE sequence with compressed sensing while preserving diagnostic image quality and acceptable lesion detection rate.

The value of intraoperative EABRs in auditory brainstem implantation.

OBJECTIVE: To compare the intraoperative electrically evoked auditory brainstem response (EABR) morphologies between neurofibromatosis II (NF2) adult auditory brainstem implant (ABI) recipients who had auditory percepts post-operatively and those who did not and between NF2 adult ABI recipients and non-NF2 pediatric ABI recipients. METHODS: This was a retrospective case series at a single tertiary academic referral center examining all ABI recipients from 1994 to 2016, which included 34 NF2 adults and 11 non-NF2 children. The morphologies of intraoperative EABRs were evaluated for the number of waveforms showing a response, the number of positive peaks in those responses, and the latencies of each of these peaks. RESULTS: 27/34 adult NF2 patients and 9/10 children had EABR waveforms. 20/27 (74.0%) of the adult patients and all of the children had ABI devices that stimulated post-operatively. When comparing the waveforms between adults who stimulated and those who did not stimulate, the proportion of total number of intraoperative EABR peaks to total possible peaks was significantly higher for the adults who stimulated than for those who did not (p < 0.05). Children had a significantly higher proportion of total number of peaks to total possible peaks when compared to adults who stimulated (p < 0.02). Additionally, there were more likely to be EABR responses at the initial stimulation than intraoperatively in the pediatric ABI population (p = 0.065). CONCLUSIONS: The value of intraoperative EABR tracing may lie in its ability to predict post-operative auditory percepts based on the placement of the array providing the highest number of total peaks.

Real-time measurement of electrode impedance during intracochlear electrode insertion.

OBJECTIVES/HYPOTHESIS: This pilot study details the use of a software tool that uses continuous impedance measurement during electrode insertion, with the eventual potential to assess and optimize electrode position and reduce insertional trauma. STUDY DESIGN: Software development and experimental study with human cadaveric cochleae and two live surgeries. METHODS: A prototype program to measure intracochlear electrode impedance and display it graphically in real time has been developed. The software was evaluated in human cadaveric temporal bones while simultaneously making real-time fluoroscopic recordings and in two live surgeries during intracochlear electrode insertion. RESULTS: Impedance changes were observed with various scalar positions, and values were consistent with those obtained using clinically available software. Using Contour Advance electrodes, impedance values increased after stylet removal, particularly when using the monopolar mode. CONCLUSIONS: Impedance values seem systematically affected by electrode position, with higher values being associated with proximity to the cochlear wall. The new software is capable of acquiring impedance measurements during electrode insertion, and these data may be useful to guide surgeons to achieve optimal and atraumatic electrode insertion, to guide robotic electrode insertion, and to provide insights about electrode position in the cochlea.

Cochlear implantation in prelingually deafened adolescents.

OBJECTIVES: To determine the efficacy of cochlear implantation (CI) in prelingually deafened adolescent children and to evaluate predictive variables for successful outcomes. DESIGN: Retrospective medical record review. PARTICIPANTS: Children aged 10 to 17 years with prelingual hearing loss (mean length of deafness, 11.5 years) who received a unilateral CI (mean age at CI, 12.9 years). INTERVENTION: Unilateral CI. MAIN OUTCOME MEASURES: Standard speech perception testing (Consonant-Nucleus-Consonant [CNC] monosyllabic word test and Hearing in Noise [HINT] sentence test) was performed preoperatively, 1 year postoperatively (year 1), and at the last follow-up/end of the study (EOS). RESULTS: There was a highly significant improvement in speech perception scores for both HINT sentence and CNC word testing from the preoperative testing to year 1 (mean change score, 51.10% and 32.23%, respectively; P < .001) and from the preoperative testing to EOS (mean change score, 60.02% and 38.73%, respectively; P < .001), with a significantly greater increase during the first year (P < .001). In addition, there was a highly significant correlation between improvements in performance scores on the CNC word and HINT sentence speech perception tests and both age at CI and length of deafness at the year 1 testing (P ≤.009) but not from the year 1 testing to EOS testing. Adolescents with progressive deafness and those using oral communication before CI performed significantly better than age-matched peers. CONCLUSIONS: Adolescents with prelingual deafness undergoing unilateral CI show significant improvement in objective hearing outcome measures. Patients with shorter lengths of deafness and earlier age at CI tend to outperform their peers. In addition, patients with progressive deafness and those using oral communication have significantly better objective outcomes than their peers.

Open distal humerus fractures--review of the literature.

Fractures of the distal humerus can be difficult to treat due to the periarticular nature of these injuries and the complexity of the elbow joint. Although anatomic and timely repair of the distal humerus with meticulous handling of soft tissues and appropriate postoperative therapy all help to optimize results, an open fracture presents other challenges that may limit successful outcomes in spite of these measures. Open fractures have been found to affect younger males involved in high-energy injuries, as well as older, osteoporotic females involved in lower energy situations. Successful management of these injuries requires urgent and aggressive soft tissue management, skeletal stabilization, and treatment of neurovascular insult (if applicable). This article presents a review of the current literature available concerning the epidemiology, assessment and examination, treatment options, complications, and outcomes of patients with open distal humerus fractures.