Qualitative and Quantitative Analyses of the Enantiomers of Nicotine and Nornicotine Employing Chiral Supercritical Fluid Chromatography.

An optimized method employing chiral supercritical fluid chromatography with diode array UV-VIS detection has been developed for the quantitative analysis of nicotine and nornicotine enantiomer distributions. The method parameters that were optimized included: column type (stationary phases, Chiralpak IG-3), column temperature (40°C), modifier types and concentration (isopropyl alcohol, 10%), additive types and concentrations (diethylamine, 0.2%), elution times (<6 min, flow rate 3 mL/min) and resolution factor (>1.2). These optimized conditions led to nicotine and nornicotine enantiomer detection limits of ~5 ng/µL with accompanying %RSD values of <2% from the analyses of commercially available nicotine-containing formulations.

Chiral Separation of Cannabichromene, Cannabicyclol, and Their Acidic Analogs on Polysaccharide Chiral Stationary Phases.

Until recently, chirality has not been a major focus in the study of cannabinoids, as most cannabinoids of interest, such as cannabidiol and tetrahydrocannabinol, exist as a single isomer from natural sources. However, this is changing as more cannabinoids are identified, and compounds such as cannabichromene and cannabicyclol are emerging as potential investigatory candidates for varying indications. Because these molecules are chiral, the separation and study of the individual enantiomers' biological and physiological effects should therefore be of interest. The purpose of this study was to identify analytical separation conditions and then adapt those conditions to preparative separation. This was accomplished with a column-screening approach on Daicel's immobilized polysaccharide chiral stationary phases using non-traditional mobile phases, which included dichloromethane, ethyl acetate, and methyl tert-butyl ether under high-performance liquid chromatography conditions. CHIRALPAK® IK was found to separate all four compounds well with mobile phases containing hexane-dichloromethane (with or without an acidic additive). From these methods, the separation productivities were calculated to better visualize the separation scalability, which shows that the kilogram-scale separations of each are feasible.

Auditory nerve phase-locked response recorded from normal hearing adults using electrocochleography.

OBJECTIVE: The auditory nerve overlapped waveform response (ANOW), a new measure that can be recorded non-invasively from humans, holds promise for providing more accurate assessment of low frequency hearing thresholds than currently used objective measures. This research aims to investigate the robustness and the nature of the ANOW response in humans. DESIGN: Repeated within-session recordings of the ANOW response using low-frequency Tone Bursts (TBs) were obtained at multiple stimulus levels. ANOW's absolute amplitude and phase locking value (PLV) measures were analysed to obtain normative data and to test the reliability of the ANOW response. STUDY SAMPLE: Thirteen normal hearing adults within the age range of 25 to 40 years. RESULTS: ANOW response was obtained to both 250 Hz and 500 Hz TBs and was traced down to 30-40 dB nHL. ANOW response showed significantly higher amplitude and stronger phase locking using 250 Hz TB compared to 500 Hz TB. High degree of test retest reliability of the ANOW response was found using 250 Hz TB at presentation levels higher than 40 dB nHL. CONCLUSIONS: ANOW response is recordable noninvasively using low-frequency TBs and shows higher robustness as the stimulus frequency decreases.

Medial Olivocochlear Reflex Effect on Cochlear Response in Humans: Elicitor Side and Level.

BACKGROUND: Understanding the functional differences between crossed and uncrossed medial olivocochlear (MOC) neurons has been of interest to researchers for decades. Previous reports revealed conflicting results about which MOC pathway, crossed or uncrossed, is stronger in humans. Both crossed and uncrossed MOC neurons synapse at the base of the outer hair cells (OHCs) in each ear. OHCs generate the cochlear microphonic, which is a major contributor to the cochlear response (CR) PURPOSE: The current study investigated the effects of eliciting the crossed and uncrossed MOC reflex (MOCR) on CR in humans with three levels of noise. RESEARCH DESIGN: Normal-hearing, young adults (n = 16) participated in this study. The CR was recorded using 500 Hz tone-burst stimuli presented at 80 dB nHL. To examine the crossed and uncrossed MOCR, CR was recorded without and with continuous ipsilateral or contralateral broadband noise (BBN) at three levels (40, 50, and 60 dB SPL). DATA ANALYSIS: Analysis of the CR was completed using the amplitude of the response extracted using fast Fourier transform. Statistical analysis was completed using repeated measures analysis of variance and post-hoc analysis. RESULTS: Compared with baseline, the presentation of BBN, specifically contralaterally, resulted in CR enhancement with no significant difference as a function of the three BBN levels. Greater enhancement of the CR amplitude was observed with contralateral than ipsilateral BBN elicitor. CONCLUSIONS: The current findings suggest that a contralateral elicitor of the uncrossed MOC pathway results in a larger CR amplitude enhancement compared with an ipsilateral elicitor of the crossed MOC pathway, regardless of the elicitor level. Eliciting the MOCR appears to modulate the OHCs function. Furthermore, assessing the MOCR with the 500 Hz CR with BBN elicitors at moderate levels should separate its effects (i.e., increase response amplitude) from those associated with the middle ear muscle reflex (i.e., reduce response amplitude).

Comparing Simultaneous Electrocochleography and Auditory Brainstem Response Measurements Using Three Different Extratympanic Electrodes.

BACKGROUND: Various extratympanic recording electrodes have been used to make electrocochleography (ECochG) and auditory brainstem response (ABR) measurements in clinics, translational research, and basic science laboratories. However, differences may exist in ECochG and ABR measurements depending on the different types of extratympanic electrodes that are used. PURPOSE: The purpose of this research is to compare simultaneously recorded ECochG and ABR responses using three different extratympanic electrodes. This research helps clinicians and researchers to understand how electrode types and recording sites influence EcochG and ABR results. In addition, our findings could provide more normative data to the ECochG and ABR literature as well as give perspective on a preferred electrode approach when performing simultaneous ECochG and ABR testing. RESEARCH DESIGN: Ours was a repeated-measures study with measurements being made from individual participants on two separate sessions. STUDY SAMPLE: Twenty young adult females with normal hearing. PROCEDURE: A three-channel recording system was used to simultaneously record ECochG and ABR measurements in response to alternating polarity click stimuli. In each session, measurements were simultaneously recorded with a TipTrode electrode and one of the tympanic membrane (TM) electrodes. DATA COLLECTION AND ANALYSIS: Suprathreshold summating potential (SP) and action potential (AP) of the ECochG and waves I, III, and V of the ABR, and threshold responses (AP and wave V) were identified. RESULTS: Compared with the ear canal TipTrode electrode, TM electrodes yielded suprathreshold amplitudes that were larger than those from the ear canal electrode, smaller SP-AP ratios, lower AP thresholds, and less variability. These findings can help guide choices made by clinicians, translational investigators, and basic science researchers on which type of extra-tympanic electrode to use for their intended purpose.

Minimally Invasive Posterior Cervical Fusion With Facet Cages to Augment High-Risk Anterior Cervical Arthrodesis: A Case Series.

STUDY DESIGN: Retrospective case series. OBJECTIVES: To evaluate the efficacy and results of minimally invasive posterior cervical fusion with facet cages as an augment to high-risk patients and patients status post multilevel anterior cervical decompression and fusion. METHODS: Thirty-five patients with symptomatic cervical stenosis with high risk for pseudoarthrosis underwent circumferential cervical decompression and fusion via staged anterior and posterior approach. Anterior cervical decompression and fusion was performed first by means of the standard anterior approach, with the patient supine on the operating table. The patients were subsequently flipped into a prone position and minimally invasive posterior cervical facet fusion with DTRAX was performed. The patients were then followed in the outpatient clinic for an average of 312.71 days. Postoperative patient satisfaction scores were obtained via the visual analogue scale (VAS). Preoperative VAS scores were compared with postoperative VAS scores in order to evaluate patient outcomes. RESULTS: Of the 35 patients evaluated, minimum follow-up was 102 days, with a maximum follow-up of 839 days. Average preoperative and postoperative VAS scores were 7.6 and 2.8, respectively (P < .0001), with an average improvement of 4.86 points. This was an average improvement of 64.70% from preoperative to postoperative. Seventeen patients had excellent outcomes, with a postoperative VAS score ≤2. Seven patients achieved a postoperative VAS score of 0, with 100% improvement of preoperative pain and symptoms. Average blood loss was 70.38 mL. Average length of stay was 1.03 days. CONCLUSIONS: The results indicate that minimally invasive posterior cervical decompression and fusion with facet cages, when combined with standard anterior cervical decompression and fusion, is an effective means of obtaining circumferential cervical fusion while simultaneously improving patient outcomes.

Human medial olivocochlear reflex: Contralateral activation effect on low and high frequency cochlear response.

The role of the medial olivocochlear (MOC) reflex has been investigated by assessing changes of cochlear responses (CR) in humans. The CR consists of pre-neural and neural potentials originating from the inner ear, and at high signal levels is dominated by cochlear microphonic (CM). The CM originates from the outer hair cells, where the MOC fibers synapse, and there is little research about using it to investigate the MOC reflex in humans. The current study aimed to investigate the effect of contralateral activation of the MOC reflex on the CR in humans. The CR was recorded in female adults (n = 16) to 500 and 2000 Hz tone burst stimuli presented at 80 dB nHL with and without contralateral broadband noise (CBBN) at 40 dB SPL. Two different methods were utilized to quantify and analyze the CR data: peak amplitude and power spectrum. Results revealed enhancement of the CR amplitude with activation of the MOC reflex. Furthermore, on average, enhancement in the CR amplitude was observed to 500 Hz, but not 2000 Hz stimulus. The CR power spectrum findings revealed similar findings to the peak amplitude. These findings indicate the MOC effect is measurable when using a low frequency stimulus, but not high frequency. Moreover, the CR could be used as a potential tool to study the MOC reflex in humans.

Saturday allied health services for geriatric evaluation and management: A controlled before-and-after trial.

OBJECTIVE: To assess the effect of Saturday allied health services on a geriatric evaluation and management ward. METHODS: A controlled before-and-after trial at two wards. Allied health services were added to usual weekday staffing on Saturdays for 6 months on the experimental ward. Length of stay, functional independence, readmissions, discharge destination and costs were evaluated at pre-intervention (N = 331) and intervention (N = 462). RESULTS: Relative to the comparison ward, the experimental ward had longer length of stay (mean 7.8 days, 95% CI 4.7-10.8), fewer readmissions (mean 3.1 days, 95% CI 0.6-5.7) and no difference in the proportion discharged home. Cost-effectiveness demonstrated no significant difference in cost ($2639, 95% CI $-386 to $5647) and functional independence gain (3.6 units, 95% CI 0.8-6.5) favouring the experimental ward. CONCLUSION: These findings do not support the provision of additional Saturday allied health services in geriatric evaluation and management to reduce length of stay.

Electrocochleography: New Uses for an Old Test and Normative Values.

Purpose This article combines the results of 3 studies that were presented at the HeAL 2018 Conference in Lake Como, Italy, in June 2018. Each study involved electrocochleography (ECochG), a neurodiagnostic evaluation that has been used clinically for over 80 years but whose applications continue to expand. The 1st study describes recent research wherein ECochG was recorded from asymptomatic subjects who were siblings or offspring of patients with a confirmed diagnosis of Ménière's disease (MD). Our results provide evidence that ECochG may be helpful in not only diagnosing MD but also predicting it as well. Second, case studies are described where ECochG was important in both diagnosing superior semicircular canal dehiscence and monitoring the repair of this condition during surgery. Finally, although ECochG has been practiced clinically for over 8 decades, the protocols for recording, measuring, and interpreting the electrocochleogram continue to lack standardization among clinicians and scientists. We thus present normative data for some of these features based on noninvasive recordings made from the tympanic membrane from 100 normal hearing subjects. Conclusions Although the primary use of ECochG continues to be in the diagnosis of MD, we report on 2 additional clinical applications for this important test of inner ear/auditory nerve function. First, a preliminary study on a small sample of subjects indicates that ECochG may also be useful in predicting MD prior to the onset of symptoms in individuals who may be genetically predisposed to developing it. Second, through a series of case studies, we demonstrate how ECochG is used to help diagnose superior semicircular canal dehiscence and monitor the status of the inner ear during the surgical repair of this condition. Finally, normative values for clinically important components of the electrocochleogram based on tympanic membrane recordings have been established from a large sample of subjects.

Whole Recombinant Saccharomyces cerevisiae Yeast Expressing Ras Mutations as Treatment for Patients With Solid Tumors Bearing Ras Mutations: Results From a Phase 1 Trial.

We are developing whole, heat-killed, recombinant Saccharomyces cerevisiae yeast, engineered to encode target proteins, which stimulate immune responses against malignant cells expressing those targets. This phase 1 trial, enrolling patients with advanced colorectal or pancreas cancer, was designed to evaluate safety, immunogenicity, response, and overall survival of ascending doses of the GI-4000 series of products, which express 3 different forms of mutated Ras proteins. The study enrolled 33 heavily pretreated subjects (14 with pancreas and 19 with colorectal cancer), whose tumors were genotyped before enrollment to identify the specific ras mutation and thereby to identify which GI-4000 product to administer. No dose limiting toxicities were observed and no subject discontinued treatment due to a GI-4000 related adverse event (AE). The majority of AEs and all fatal events were due to underlying disease progression and AE frequencies were not significantly different among dose groups. GI-4000 was immunogenic, as Ras mutation-specific immune responses were detected on treatment in ∼60% of subjects. No objective tumor responses were observed but based on imaging, clinical status and/or biochemical markers, stable disease was observed in 6 subjects (18%) on day 29, while 1 subject had stable disease at days 57 and 85 follow-up visits. The median overall survival was 3.3 months (95% confidence interval, 2.3-5.3 mo), and 5 subjects survived past the 48-week follow-up period. No significant dose-dependent trends for survival were observed. This first clinical trial in humans with GI-4000 demonstrated a favorable safety profile and immunogenicity in the majority of subjects.

Human Summating Potential Using Continuous Loop Averaging Deconvolution: Response Amplitudes Vary with Tone Burst Repetition Rate and Duration.

Electrocochleography (ECochG) to high repetition rate tone bursts may have advantages over ECochG to clicks with standard slow rates. Tone burst stimuli presented at a high repetition rate may enhance summating potential (SP) measurements by reducing neural contributions resulting from neural adaptation to high stimulus repetition rates. To allow for the analysis of the complex ECochG responses to high rates, we deconvolved responses using the Continuous Loop Averaging Deconvolution (CLAD) technique. We examined the effect of high stimulus repetition rate and stimulus duration on SP amplitude measurements made with extratympanic ECochG to tone bursts in 20 adult females with normal hearing. We used 500 and 2,000 Hz tone bursts of various stimulus durations (12, 6, 3 ms) and repetition rates (five rates ranging from 7.1 to 234.38/s). A within-subject repeated measures (rate x duration) analysis of variance was conducted. We found that, for both 500 and 2,000 Hz stimuli, the mean deconvolved SP amplitudes were larger at faster repetition rates (58.59 and 97.66/s) compared to slower repetition rates (7.1 and 19.53/s), and larger at shorter stimulus duration compared longer stimulus duration. Our concluding hypothesis is that large SP amplitude to short duration stimuli may originate primarily from neural excitation, and large SP amplitudes to long duration, fast repetition rate stimuli may originate from hair cell responses. While the hair cell or neural origins of the SP to various stimulus parameters remains to be validated, our results nevertheless provide normative data as a step toward applying the CLAD technique to understanding diseased ears.

Normative data for TM electrocochleography measures.

OBJECTIVE: Establish normative data for tympanic electrocochleography (TM ECochG) parameters in normal hearing adults without Ménière's disease's (MD) symptoms. Describe TM ECochG variables that help to distinguish normal from MD ears. MATERIAL AND METHODS: We enrolled 100 subjects (N = 200 ears), 59 females, aged between 19 and 71 years from 09/2010 to 04/2014. Inclusion criteria: normal otomicroscopy, hearing thresholds ≤25 dB nHL from 250 to 4000 Hz, normal tympanogram, no symptoms of MD according to the AAO-HNS 1995 criteria and Gibson's score <7. We excluded subjects with dizziness, aural fullness or other symptoms of endolymphatic hydrops. The following parameters were analyzed: SP/AP amplitude ratio, SP/AP area ratio and the difference between AP latency with rarefaction and condensation stimuli. RESULTS: There was no significant difference between right and left ears (Intraclass correlation coefficient < 0.6). SP/AP amplitude ratio varied between 0.084 and 0.356 and SP/AP area ratio between 0.837 and 1.671 (percentiles 5 and 95). The AP latency difference to rarefaction and condensation clicks was between 0.0 and 0.333 ms. CONCLUSION: Normative data for TM ECochG parameters were established in 100 normal hearing subjects without MD. These data can be used to distinguish normal from pathological findings and in follow-up of MD patients.

Otolith Dysfunction in Persons With Both Diabetes and Benign Paroxysmal Positional Vertigo.

OBJECTIVE: Vestibular dysfunction is a well-recognized complication of type 2 diabetes (DM) that may contribute to increased fall risk. The prevalence of benign paroxysmal positional vertigo (BPPV) is higher in people with DM. The impact of DM on the otolith organs of the vestibular system in people with BPPV is unknown. The purpose of this study was to analyze otolith function using vestibular-evoked myogenic potential (VEMP) tests in people with DM and concurrent BPPV (BPPV + DM), and to examine the relationships between VEMP variables and diabetes-related variables. STUDY DESIGN: Prospective, cross-sectional study. SETTING: Tertiary academic medical center. SUBJECTS AND METHODS: Participants 40 to 65 years were recruited in four groups: controls (n = 20), people with DM (n = 19), BPPV (n = 18), and BPPV + DM (n = 14). Saccule and utricle function were examined using cervical VEMP (cVEMP) and ocular VEMP (oVEMP), respectively. Diabetes-related variables such as HbA1c, duration of diabetes, and presence of sensory impairment due to diabetes were collected. RESULTS: The frequency of abnormal cVEMP responses was higher in the DM (p = 0.005), BPPV (p = 0.003), and BPPV + DM (p <0.001) groups compared with controls. In the participants with diabetes, higher HbA1c levels were correlated with prolonged P1 (p = 0.03) and N1 latencies (p = 0.03). The frequency of abnormal oVEMP responses was not different between groups (p = 0.2). CONCLUSION: Although BPPV and DM may independently affect utricle and saccule function, they do not seem to have a distinct cumulative effect.

The Effect of Contralateral Pure Tones on the Compound Action Potential in Humans: Efferent Tuning Curves.

BACKGROUND: The compound action potential (CAP) has been suggested in the literature as an alternative to otoacoustic emissions for evaluating the efferent auditory system. However, very few studies have examined efferent influence on auditory nerve potentials in humans. PURPOSE: This study examines the effects of presenting contralateral pure tones on the ipsilateral CAP onset and offset amplitudes as a potential clinical tool for the assessment of efferent auditory function. RESEARCH DESIGN: CAPs for 1- and 4-kHz tone pips (TPs) and clicks were recorded from 9, 9, and 8 participants, respectively. Contralateral tones were presented at levels ranging from 20 to 70 dB HL in 10-dB steps. The frequencies of the contralateral tones were 0.5, 1, 2 kHz for the 1-kHz TP CAP; 2, 4, 8 kHz for the 4-kHz TP CAP; and 0.5, 1, 2, 4, 8 kHz for the click CAP. DATA ANALYSIS: The CAP onset and offset amplitudes in all experimental conditions were analyzed and compared to the CAP amplitude without contralateral stimulation (i.e., baseline). RESULTS: Maximum suppression of 1-kHz TP CAP onset amplitude was obtained in seven out of nine participants by the 1-kHz contralateral pure tone at 40 dB HL. The 4-kHz TP CAP onset amplitude was maximally suppressed in eight out of nine participants by the 8-kHz contralateral pure tone at 30 dB HL. The click CAP offset amplitude was maximally suppressed in four out of eight participants by the 8-kHz contralateral tone presented at 40 dB HL. The 1- and 4-kHz TP CAP offset and click CAP onset amplitudes were not affected by contralateral stimulation. CONCLUSIONS: These results along with the previous studies may suggest that the efferent system is maximally stimulated by moderate signal-level tones (i.e., 30-40 dB HL), and that efferent activity is dependent on frequency cues of both the stimulus and suppressor tones. Other factors that might be affecting efferent influence on the CAP in humans such as sound duration, phase, bandwidth, and periodicity need to be further investigated.

Quantification of Total Particulate Matter and Benzene-Soluble Fraction Inhalation Exposures in Roofing Workers Performing Tear-off Activities.

Asphalt shingle removal (tear-off) from roofs is a major job task for an estimated 174,000 roofers in the United States. However, a literature search showed that there are no published studies that characterize worker inhalation exposures to asphalt particulates during shingle tear-off. To begin to fill this gap, the present study of inhalation exposures of roofers performing asphalt shingle tear-off was undertaken. The airborne agents of interest were total particulate matter (TP) and organic particulates measured as the benzene-soluble fraction (BSF) of total particulate. The study's objectives were to measure the personal breathing zone (PBZ) exposures of roofing tear-off workers to BSF and TP; and to assess whether these PBZ exposures are different from ambient levels. Task-based PBZ samples (typical duration 1-5 hours) were collected during asphalt shingle tear-off from roofs near Houston, Texas and Denver, Colorado. Samples were analyzed for TP and BSF using National Institute of Occupational Safety and Health (NIOSH) Method 5042. As controls, area samples (typical duration 3-6 hours) were collected on the ground near the perimeter of the tear-off project Because of the presence of significant sources of inorganic particulates in the work environment, emphasis was placed on the BSF data. No BSF exposure higher than 0.25 mg/m3 was observed, and 69% of the PBZ samples were below the limit of detection (LOD). Due to unforeseen confounding, however, statistical comparisons of on-the-roof PBZ samples with on-the-ground area samples posed some special challenges. This confounding grew out of the interaction of three factors: statistical censoring from the left; the strong inverse correlation between LOD concentration and sampling duration; and variation in sampling durations between on-the-ground area samples and on-the-roof PBZ samples. A general linear model analysis of variance (GLM-ANOVA) was applied to help address the confounding. The results of this analysis indicate that personal sample BSF results were not statistically significantly different from the background/area samples.

Age-related changes in vestibular evoked myogenic potentials using a modified blood pressure manometer feedback method.

PURPOSE: To collect age-specific vestibular evoked myogenic potential (VEMP) data and to characterize age-related differences in VEMP parameters using a modified blood pressure manometer (BPM) method of sternocleidomastoid (SCM) muscle monitoring. METHODS: VEMPs were recorded on healthy adults ranging in age from 23 to 84 years with no history of dizziness, neuromuscular pathologies, or cervical complaints. Participants were assigned to 3 groups using a nonprobability static group assignment based on their age. VEMP P1 and N1 latency, threshold, peak-to-peak amplitude, and interamplitude difference (IAD) ratios were obtained at 130 dB SPL. RESULTS: Statistical differences were detected in peak-to-peak mean amplitude and threshold measures among groups. Post hoc analysis revealed that differences shown were between the young group and both older groups. No significant differences were noted in P1 and N1 latencies or IAD ratios. CONCLUSIONS: This study confirmed a significant decline in VEMP amplitude and increase in VEMP thresholds in healthy older persons. Normative age-related data may be necessary to properly interpret VEMP recordings in a clinical setting when evaluating aging populations. The BPM method utilized for controlling SCM muscle may be a valuable alternative to control SCM muscle contraction when electromyography equipment is not available.

Electrocochleography: a review of recording approaches, clinical applications, and new findings in adults and children.

Research related to expanding and improving the clinical use of electrocochleography (ECochG) has been ongoing for 25 yr at the University of Kansas Medical Center. This article presents highlights of findings from our laboratory during this period that have contributed to current ECochG recording approaches and clinical applications. A review of new data related to improving the sensitivity of ECochG in the diagnosis of Ménière's disease, the use of an ear canal recording approach for improving auditory brain stem response testing in newborns, and technical aspects related to recording the cochlear microphonic in newborns also will be presented.

Improved sensitivity of electrocochleography in the diagnosis of Meniere's disease.

ECochG has long been shown to complement the diagnosis of MD, primarily through measurement of the SP/AP amplitude ratio. While reported in the literature to be highly specific to this disorder, ECochG's sensitivity in the general MD population remains relatively low (ranging from 20-65%). The current study assessed the sensitivity and specificity of the ECochG protocol we employ for suspected MD patients, which includes measuring both the amplitudes and areas of the SP and AP to clicks (to derive the SP/AP amplitude and area ratios), and the SP amplitudes to 1000 and 2000 Hz tone bursts. A retrospective chart review was conducted to compare ECochG results from 178 suspected MD patients with their eventual diagnoses. Measurements of highest sensitivity and specificity (determined using a logistic regression analysis) included: SP amplitude, SP area, SP/AP area ratio, and total SP-AP area. Sensitivity and specificity values associated with these measures were 92% and 84%, respectively. The sensitivity value is considerably higher than previously reported, and is attributable to the inclusion of area measurements in our protocol.

ABR recordings in newborns using an ear canal electrode.

The objective of this study was to improve the sensitivity of ABR recordings in newborns via a procedure that utilizes the ear canal as a recording site. Conventional recordings were compared to ear canal recordings of the ABR in 45 normally-hearing newborns who passed their newborn hearing screening. Responses were obtained at stimulus levels of 80, 60, 40, and 20 dBnHL using forehead (+) to ear canal (-), versus forehead (+) to mastoid (-) electrode configurations. ABR parameters evaluated included measurement of component amplitudes of wave I and V, absolute latencies of I and V, the I-V interwave interval, and amplitude ratio. At stimulus levels of 80, 60, and 40 dBnHL, wave I amplitude was significantly larger using the ear canal configuration. This investigation shows that the amplitude of wave I is significantly larger and easier to identify when the ear canal is used as one of the recording sites in comparison to more conventional scalp (mastoid) recordings.

Observations on mastoid versus ear canal recorded cochlear microphonic in newborns and adults.

The cochlear microphonic (CM) may play an important role in the diagnosis of auditory neuropathy (AN) in newborns. However, since the CM tends to mirror the waveform of the acoustic stimulus, conscientious recording methodology must be applied to separate true response from artifact. The difficulty in achieving this separation has limited the clinical usefulness of the CM. In an effort to call attention to the importance of recording protocol when measuring the CM, the present study was designed to optimize CM recordings in humans by investigating the following parameters: (1) secondary minus electrode recording site (mastoid versus ear canal [EC]), (2) stimulus parameters, and (3) grounding and shielding conditions. Normative data were collected in full-term newborns (n = 7) and adults (n = 4) with no known risk factors for cochlear or retrocochlear pathology. Results suggest that the CM is easier to separate from stimulus artifact using an EC electrode and toneburst stimuli. In addition, electromagnetic shielding and grounding of the electrode cables and the acoustic transducer were effective in reducing and/or eliminating stimulus artifact. Results from this normative study may be helpful in improving the diagnostic utility of the CM in AN and other hearing-related disorders.