Reflex Threshold Research Articles

Electrically evoked stapedial reflex threshold assessment among malaysian cochlear implant users: Comparisons between different stimulus rates

Background and Objective: Cochlear implant (CI) mapping can be carried out using subjective or objective assessments. Electrically evoked stapedial reflex threshold (ESRT) measurement is one of the valuable objective assessments to establish appropriate CI maps. As such, more research efforts are required to determine the most optimum recording protocols when recording ESRT. In the present study, the effect of stimulus rate on ESRT among CI users was determined. It was also of interest to know which stimulus rate would produce the optimum correlation with the behavioral most comfortable level (MCL) results. Materials and Methods: In this study that employed a repeated measures design, 12 Malaysian CI users were enrolled (mean age = 22.3 ± 13.3 years, ranging from 14 to 51 years). MCL and ESRT (measured in charge units, qu) were measured for three representative electrodes (electrode 2, electrode 6, and electrode 11) using 1000 pps and 2000 pps rates. Results: ESRT was 100% recordable for electrodes 2 and 6. For electrode 2, the mean ESRT values were 20.5 qu and 20.4 qu for 1000 pps and 2000 pps, respectively. While for electrode 6, the mean ESRT was 25.4 qu for 1000 pps and 25.7 for 2000 pps. Excellent correlations were found between ESRT and MCL for both stimulus rates (intraclass correlation ≥0.90). Conclusion: Both stimulus rates were found to produce comparably good ESRT results. Since ESRT and MCL values were highly correlated with each other, the objective ESRT testing can be used conveniently to predict the behavioral MCL, particularly among difficult-to-test patients.

Preemptive local anesthetic infiltration reduces opioid requirements without attenuation of the intraoperative electrical stapedial reflex threshold in pediatric cochlear implant surgery.

Background and Aims:Total intravenous anesthesia using remifentanil provides good surgical condition without affecting the intraoperative electrical stapedial reflex threshold (ESRT). However, remifentanil results in hyperalgesia and increases postoperative opioid requirements. Local anesthetic infiltration is alternative methods to opioid for providing analgesia. However, otologists avoids its use as it can abolish the ESRT. We investigated the effect of the preemptive local anesthetic infiltration on intraoperative ESRT and opioid requirements in pediatric cochlear implant surgery performed under TIVA.Material and Methods:Prospective, randomized, double-blinded, controlled study including 70 child undergoing cochlear implant under TIVA were randomly assigned to a local anesthesia (LA group, n = 35) or control (CT group, N = 35). The primary outcome was the total tramadol consumption during the first 24 h postoperative, and the secondary outcomes were time to first analgesia request, postoperative pain scores, the ESRT and, propofol and remifentanil requirements. The incidence of postoperative vomiting was recorder as well.Results:The total tramadol consumption during the first 24 h after surgery was significantly less in the LA group than in CT group (8.25 [4.3] vs. 16.5 [6.57] mg, P < 0.01). The time to first analgesic request was significantly prolonged in the LA group as compared with the CT group [8 [2–12] vs. 3 [0–8] h, P < 0.01). The postoperative Faces, Legs, Activity, Cry Consolability pain scores were significantly lower in the LA group at 15 min, 30 min, 2, 4 and 6 h postoperative. Mean remifentanil infusion rate [mean (standard deviation)] was significantly higher in in the CT group than in the LA group [0.7 (0.3) vs. 0.5 (0.2) μg/kg/min; P = 0.001).The ESRT response, propofol requirements, and the incidence of postoperative vomiting had no significant differences between both groups.Conclusion:Preemptive local anesthetic infiltration reduced opioid requirements without attenuation of the ESRT in pediatric cochlear implant surgery performed under TIVA.

Stretch reflex excitability in contralateral limbs of stroke survivors is higher than in matched controls

BackgroundSpasticity, characterized by hyperreflexia, is a motor impairment that can arise following a hemispheric stroke. While the neural mechanisms underlying spasticity in chronic stroke survivors are unknown, one probable cause of hyperreflexia is increased motoneuron (MN) excitability. Potential sources of increased spinal MN excitability after a stroke include increased vestibulospinal (VS) and/or reticulospinal (RS) drive. Spasticity, as clinically assessed in stroke survivors, is highly lateralized, thus RS contributions to stroke-induced spasticity are more difficult to reconcile, as RS nuclei routinely project bilaterally to the spinal cord. Yet studies in stroke survivors suggest that there may also be changes in neuromodulation at the spinal level, indicative of RS tract influence. We hypothesize that after hemispheric stroke, alterations in the excitability of the RS nuclei affect both sides of the spinal cord, and thereby contribute to increased MN excitability on both paretic/spastic and contralateral sides of stroke survivors, as compared to neurologically intact subjects.MethodsWe estimated stretch reflex thresholds of the biceps brachii (BB) muscle using a position-feedback controlled linear motor to progressively indent the BB distal tendon in both spastic and contralateral limbs of hemispheric stroke survivors and in age-matched intact subjects.ResultsOur previously reported results show a significant difference between reflex thresholds of spastic and contralateral limbs of stroke survivors recorded from BB-medial (p < 0.005) and BB-lateral (p < 0.001). For this study, we report that there is also a significant difference between the reflex thresholds in the contralateral limb of stroke subjects and the dominant arm of intact subjects, again measured from both BB-medial (p < 0.05) and BB-lateral (p < 0.05).ConclusionThe reduction in stretch reflex thresholds in the contralateral limb of stroke survivors, based here on comparisons with thresholds of intact subjects, suggests an increased MN excitability on contralateral sides of stroke survivors as compared to intact subjects. This in turn supports our contention that RS tract activation, which has bilateral descending influences, is at least partially responsible for increased stretch reflex excitability, post-stroke, as both contralateral and affected sides show increased MN excitability as compared to intact subjects. Still, spasticity, presently diagnosed only on the affected side, with increased MN excitability on the affected side as compared to the contralateral side (our previous study), may be due to a different strongly lateralized pathway, such as the VS tract, which has not been directly tested here. Currently available clinical methods of spasticity assessment, such as the Modified Ashworth Scale, lack the resolution to quantify this phenomenon of a bilateral increase in MN excitability.

A Possible Source of Heterogeneity in Nociceptive Flexion Reflex (NFR) Threshold Among Patients with Fibromyalgia: Systematic Review and Meta-Analysis

Objectives: We aimed to investigate the possibility of sample size as a possible source of heterogeneity in trials comparing the nociceptive flexion reflex threshold (NFRthr) in fibromyalgia (FM) patients and healthy controls. Methods: A systematic search strategy was designed and conducted in electronic databases such as Ovid MEDLINE, Cochrane Libraries, Embase, and PsycINFO. In total, nine scholarly records were filtered by the inclusion and exclusion criteria, passed for data extraction (e.g. study designs and settings; methodology; total, male, and female sample sizes in FM and healthy control groups, and effect sizes), and statistical analyses (e.g. metaanalysis and meta-regression). Using random-effects model, the effect size (i.e. mean difference between the NFRthr in FM patients and healthy controls) was meta-analyzed. Investigating the sample size as a possible source of heterogeneity and utilizing a restricted maximum likelihood (REML) technique, the trials’ effect sizes were meta-regressed in multiple meta-regression against the total, male, and female sample sizes. Prior to any investigations, the aims of this research were registered in the International Prospective Register of Systematic Reviews (PROSPERO; registration number: CRD42019140354). Results: Results indicated the deficit in NFRthr (overall mean difference = −3.16; 95% 𝐶𝐼: −6.82 𝑡𝑜 0.50) was heterogenous (𝐼 2 = 0.91, 𝜏 2 = 25.04, 𝜒2= 91.22, df & < 0.00001) and the overall effect was not statistically significant (Z = 1.69; 𝑃 = 0.09). The multiple meta-regression analyses indicated that one of the main sources of bias to the effect size in the trials was found to be the total (𝑆𝑆𝑡𝑜𝑡𝑎𝑙 = −0.0570; 𝑃 = 0.040) and female (𝑆𝑆𝑓𝑒𝑚𝑎𝑙𝑒 = −0.0569; 𝑃 = 0.047) sample sizes that participated in the studies. Conclusion: The findings suggest that the total and female sample sizes might be possible sources of bias to effect sizes determined in NFRthr in FM patient and healthy controls. A possible solution might be to conduct sex-specific trials to determine the NFRthr among FM patients in future research. Funding Statement: Authors received no source of funding for this research. Declaration of Interests: Authors declare no conflict of interest. Ethics Approval Statement: PROSPERO; registration number: CRD42019140354

Modified Biofeedback (Conditioned Biofeedback) Promotes Antinociception by Increasing the Nociceptive Flexion Reflex Threshold and Reducing Temporal Summation of Pain: A Controlled Trial

This study examined whether a modified version of biofeedback (ie, Conditioned Biofeedback) that incorporated placebo analgesia-like manipulations could promote antinociception in healthy, pain-free participants. During Conditioned Biofeedback (n = 28), sympathetic arousal level was displayed visually and participants were asked to reduce it while they received painful electric stimulations that were surreptitiously controlled by their arousal level. Thus, electric pain decreased as arousal decreased to associate successful arousal-reduction/relaxation with pain relief, and to promote expectations for future pain relief. A Biofeedback Only group (n = 24) controlled for the general effects of biofeedback/relaxation. A Biofeedback+Shock group (n = 21) controlled for the effects of practicing biofeedback during painful shocks. Nociceptive flexion reflex (NFR) threshold and temporal summation of pain (TS-pain) were used to assess changes in spinal nociception and pain facilitation, respectively. Results indicated all groups showed pre- to postbiofeedback increases in NFR threshold, but only the Conditioned Biofeedback group showed pre- to postbiofeedback reductions in TS-pain. Moreover, Conditioned Biofeedback resulted in a persistent (prebiofeedback) increase in NFR threshold across sessions, whereas Biofeedback Only resulted in a persistent (prebiofeedback) decrease in TS-pain. In sum, Conditioned Biofeedback may promote antinociception in healthy participants thus reducing risk for chronic pain. The study was registered prospectively on ClinicalTrials.gov (TU1560). PerspectiveA modified version of biofeedback that employs placebo analgesia manipulations was successful in increasing descending inhibition and reducing pain facilitation in healthy volunteers. As a result, it may be an effective means of reducing risk of future chronic pain onset by promoting an antinociceptive pain profile.

Normative Data for Frequency Specificity of Acoustic Reflex Thresholds

Purpose Although acoustic reflex thresholds (ART) have widely used to screen and diagnose auditory lesions, they are confined only for measurements in low probe tone. The present study provides normative adults data based on various frequencies of both probe tone and stimuli, and thus extends to discuss any possible clinical application as frequency specificity. Methods A total of 104 young listeners with normal hearing (53 female and 51 male) participated. After completing hearing screening tests, they performed the ART measurement in twelve conditions consisted of 3 probe tones (e.g., 226, 678, 1,000 Hz) and 4 stimulus frequencies (e.g., 500, 1,000, 2,000, 4,000 Hz). Individual’s thresholds were obtained at each condition and were statistically compared. Results All data were recorded within the normal range proposed in the classic ART measurement. Interestingly, thresholds conducted at the probe tone of 678 Hz were slightly higher than those of the other probe tones regardless of a kind of the stimulus frequencies. Also, all probe tones had the highest ART at 4,000 Hz. Conclusion We obtained the differentiated ART normalize data depending on frequency specificity. In the following study, patients with various pathologies should be applied using same probe tones and their data could be compared in terms of sensitivity and specificity. Key Words: Middle ear muscle, Acoustic reflex thresholds, 678 Hz, 1,000 Hz 중심 단어: 중이근, 음향반사역치, 678 Hz, 1,000 Hz

Experimentally induced spinal nociceptive sensitization increases with migraine frequency: a single-blind controlled study.

The nitric-oxide donor nitroglycerin (NTG) administration induces a facilitation of nociceptive pathways in episodic migraine. This study aims to test the hypothesis that induced spinal sensitization could be more pronounced in patients affected by high-frequency migraine (HF-MIG) with respect to low-frequency migraine (LF-MIG). We enrolled 28 patients with LF-MIG (1-5 migraine days/month), 19 patients with HF-MIG (6-14 migraine days/month), and 21 healthy controls (HCs). Spinal sensitization was evaluated with the neurophysiological recording of the temporal summation threshold (TST) of the nociceptive withdrawal reflex at the lower limb. Temporal summation threshold was recorded at baseline and 30, 60, and 120 minutes after NTG administration (0.9 mg sublingual). Spinal sensitization was detected in LF-MIG at 60 (P = 0.010) and 120 minutes (P = 0.001) and in HF-MIG at 30 (P = 0.008), 60 (P = 0.001), and 120 minutes (P = 0.001) after NTG administration. Temporal summation threshold did not change in HC (P = 0.899). Moreover, TST reduction was more pronounced in HF-MIG with respect to LF-MIG (P = 0.002). The percentage of patients who developed a migraine-like headache after NTG was comparable in the 2 migraine groups (LF-MIG: 53.6%, HF-MIG: 52.6%, P = 0.284), whereas no subjects in the HC group developed a delayed-specific headache. Notably, the latency of headache onset was significantly shorter in the HF-MIG group when compared with the LF-MIG group (P = 0.015). Our data demonstrate a direct relationship between migraine frequency and both neurophysiological and clinical parameters, to suggest an increasing derangement of the nociceptive system control as the disease progresses, probably as a result of the interaction of genetic and environmental factors.

P6434Evaluation of the nociceptive flexor reflex, as a new method for the diagnosis of microvascular angina

Abstract The purpose of this study was to study the diagnostic value of the nociceptive flexor reflex (NFR) method in patients with microvascular angina. Materials and methods The study included 49 patients with MVA (main group), 40 patients with classical angina II-III f.c. (comparison group 1), 42 patients with silent myocardial ischemia (comparison group 2) and 32 healthy volunteers (control group). Criteria for inclusion in the group with MVA: chest pain, positive stress test, unchanged coronary arteries according to coronary angiography, the presence of myocardial perfusion disturbance and reduction of the coronary reserve according to positiron-emission tomography of the myocardium at rest, with adenosine and cold one test. Chest pain syndrome was observed in all 49 patients. All subjects studied the functional activity of nociceptive and antinociceptive systems using the nociceptive flexor reflex method on the equipment of expert class electromyography system, the pain threshold (Pb) values, the reflex threshold (Pr) were calculated and the ratio of pain and reflex threshold was calculated to calculate the pain threshold / threshold reflex (Pb/Pr), which in healthy people is about 0.9–1.0. Results and discussion In te study of NFR in patients with MVA in the group as a whole, a decrease in the pain threshold, reflex threshold and Pb/Pr ratio compared with normal values were found. The pain threshold in patients in the group was lower (statistically significantly) when compared with the group 1, the group 2 and the control group (p&lt;0.0001; p&lt;0.0001; p&lt;0.0001, respectively). The reflex threshold in patients of the MCC group was also significantly lower when compared with the group 1, the group 2 and the control group (p&lt;0.001; p&lt;0.0001; p&lt;0.001, respectively). Due to the fact that the low pain threshold was found in 84.4% of the examined patients with MVA who had microvascular dysfunction according to positron-emission tomography, we evaluated the prognostic value of the NFR method for diagnosing the disease. To do this, an assessment was made of the odds ratio (OR) of identifying MVA in groups of patients with different levels of index K (the ratio of the pain threshold value to the reflex threshold value). We have chosen the value of index K with the highest specificity and high sensitivity equal to 0.8892. Based on the data obtained, the diagnostic value of the NFR method was calculated during the verification of the MVA. When conducting a mathematical analysis, it was found that this technique has high sensitivity (84.4%), specificity (95.12%), positive (90.48%) and negative predictive value (91.76%). We have not found information in the literature on the use of the NFR assessment method and its diagnostic value in MVA. Findings Due to the high diagnostic value of determining the NFR, we propose to include this method in the MVA diagnostic algorithm as an additional one.

Effect of Intensity Level and Speech Stimulus Type on the Vestibulo-Ocular Reflex.

Accurate vestibulo-ocular reflex (VOR) measurement requires control of extravestibular suppressive factors such as visual fixation. Although visual fixation is the dominant suppressor and has been extensively studied, the mechanisms underlying suppression from nonvisual factors of attention and auditory stimulation are less clear. It has been postulated that the nonvisual suppression of the VOR is the result of one of two mechanisms: (1) activation of auditory reception areas excites efferent pathways to the vestibular nuclei, thus inhibiting the VOR or (2) cortical modulation of the VOR results from directed attention, which implies a nonmodality-specific process. The purpose of this research was to determine if the VOR is affected by the intensity level and/or type of speech stimulus. A repeated measures design was used. The experiment was single-blinded. Participants included 17 adults (14 females, three males) between the ages of 18-34 years who reported normal oculomotor, vestibular, neurological, and musculoskeletal function. Each participant underwent slow harmonic acceleration testing in a rotational chair. VOR gain was assessed at 0.02, 0.08, and 0.32 Hz in quiet (baseline). VOR gain was also assessed at each frequency while a forward running speech stimulus (attentional) or a backward running speech stimulus (nonattentional) was presented binaurally via insert earphones at 42, 62, and 82 dBA. The order of the conditions was randomized across participants. VOR difference gain was calculated as VOR gain in the auditory condition minus baseline VOR gain. To evaluate auditory efferent function, the medial olivocochlear reflex (MOCR) was assayed using transient-evoked otoacoustic emissions (right ear) measured in the presence and absence of broadband noise (left ear). Contralateral acoustic reflex thresholds were also assessed using a broadband noise elicitor. A three-way repeated measures analysis of variance was conducted to evaluate the effect of frequency, intensity level, and speech type on VOR difference gain. Correlations were conducted to determine if difference gain was related to the strength of the MOCR and/or to the acoustic reflex threshold. The analysis of variance indicated that VOR difference gain was not significantly affected by the intensity level or the type of speech stimulus. Correlations indicated VOR difference gain was not significantly related to the strength of the MOCR or the acoustic reflex threshold. The results were in contrast to previous research examining the effect of auditory stimulation on VOR gain as auditory stimulation did not produce VOR suppression or enhancement for most of the participants. Methodological differences between the studies may explain the discrepant results. The removal of an acoustic target from space to attend to may have prevented suppression or enhancement of the VOR. Findings support the hypothesis that VOR gain may be affected by cortical modulation through directed attention rather than due to activation of efferent pathways to the vestibular nuclei.

Effect of facial skin cooling induced by a handheld fan on the cough reflex threshold and urge to cough induced by citric acid.

Facial skin cooling induced by a handheld fan alleviates the cough reflex and the urge to cough induced by citric acid http://bit.ly/2m1kzAP

Amygdala group II mGluRs mediate the inhibitory effects of systemic group II mGluR activation on behavior and spinal neurons in a rat model of arthritis pain

The amygdala plays a critical role in emotional-affective aspects of behaviors and pain modulation. The central nucleus of amygdala (CeA) serves major output functions, and neuroplasticity in the CeA is linked to pain-related behaviors in different models. Activation of Gi/o-coupled group II metabotropic glutamate receptors (mGluRs), which consist of mGluR2 and mGluR3, can decrease neurotransmitter release and regulate synaptic plasticity. Group II mGluRs have emerged as targets for neuropsychiatric disorders and can inhibit pain-related processing and behaviors. Surprisingly, site and mechanism of antinociceptive actions of systemically applied group II mGluR agonists are not clear. Our previous work showed that group II mGluR activation in the amygdala inhibits pain-related CeA activity, but behavioral and spinal consequences remain to be determined. Here we studied the contribution of group II mGluRs in the amygdala to the antinociceptive effects of a systemically applied group II mGluR agonist (LY379268) on behavior and spinal dorsal horn neuronal activity, using the kaolin/carrageenan-induced knee joint arthritis pain model. Audible and ultrasonic vocalizations (emotional responses) and mechanical reflex thresholds were measured in adult rats with and without arthritis (5–6 h postinduction). Extracellular single-unit recordings were made from spinal dorsal horn wide dynamic range neurons of anesthetized (isoflurane) rats with and without arthritis (5–6 h postinduction). Systemic (intraperitoneal) application of a group II mGluR agonist (LY379268) decreased behaviors and activity of spinal neurons in the arthritis pain model but not under normal conditions. Stereotaxic administration of LY379268 into the CeA mimicked the effects of systemic application. Conversely, stereotaxic administration of a group II mGluR antagonist (LY341495) into the CeA reversed the effects of systemic application of LY379268 on behaviors and dorsal horn neuronal activity in arthritic rats. The data show for the first time that the amygdala is the critical site of action for the antinociceptive behavioral and spinal neuronal effects of systemically applied group II mGluR agonists.

A Tendon Indentation Method to Quantify Velocity-Dependent Reflex Responses after Hemispheric Stroke.

Stretch reflex responses in passive muscle can be utilized to assess spasticity in chronic stroke survivors. In this study, we present a different method of eliciting the reflex response by imposing tendon indentation using a linear motor. Specifically, we test a "Ramp-and-hold" protocol, utilizing a linear motor controlled by a position-controlled feedback loop (Linmot, Inc), to indent the biceps brachii distal tendon at different velocities. The protocol was tested on the affected arm of three stroke subjects. We also utilized a tendon indentation combined with tendon-tapping method to quantify the reflex threshold. Our results indicate that the reflex response was elicited at velocities equal to or above 50 mm/s in 2/3 subjects. No reflex response was detected in one subject. All subjects showed a distinct reflex threshold using the indentation/tapping method. Furthermore, the presence of a reflex response during tendon-tapping was not necessarily accompanied by the elicitation of a reflex response during the ramp-and-hold. However, our data suggests that the indentation threshold during tapping is correlated to the presence of a reflex response at the velocities tested during the ramp-and-hold. Though more time consuming, tendon indentation using ramp-and-hold could provide greater resolution of the reflex response to quantify spasticity than the current clinically employed ballistic tapping method using a reflex hammer.

Musculoskeletal simulation framework for impairment-based exoskeletal assistance post-stroke.

Assistive technology for the lower extremities has shown great promise towards improving gait function in people following neuromuscular injuries. However, our previous work assisting knee flexion torque in post-stroke Stiff-Knee gait found that augmenting strength can induce secondary complications such as spasticity due to stretching of the rectus femoris. In this work we explore whether we could have obtained improved knee flexion but avoided a spastic response by simulating combinations of hip and knee flexion torques using musculoskeletal modeling and simulation. We explore previously collected data on a case-by-case basis to determine individual-specific quadriceps reflex thresholds based on estimated rectus femoris muscle fiber stretch velocities. We then implemented a forward simulation framework to identify the subject-specific hip-knee assistance prescription to improve knee range of motion without initiating a spastic response. The obtained subject-specific assistive prescription informs the development of new gait assistance strategies for post-stroke gait and could be extended to other neuromuscular gait impairments.

Effects of ginsenoside-Rg2 on mechanical allodynia, heat hyperalgeia, depressive state of rats with chronic sciatic nerve constriction injury

To investigate the effects of ginsenoside-Rg2 on mechanical allodynia, heat hyperalgeia, depressive state of rats with chronic sciatic nerve constriction injury. Fifty SD rats were randomly divided into 5 groups: blank control group (Normal, normal + saline),sham operation group (Sham, sham operation + saline),chronic constriction injury of the sciatic nerve group (CCI, CCI + saline),ginsenoside-Rg2 low dose group (CCI + Rg2 5 mg/kg), and ginsenoside-Rg2 high dose group (CCI + Rg2 10 mg/kg).After the CCI model was established,drug were injected into the abdominal cavity through the syringe once a day,for 14 consecutive days.The mechanical shrinkage foot reflex threshold (MWT) and thermal withdrawal latency(TWL) were determined at 1 d before the operation and at 1,3,5,7,10 and 14 d after the operation.Light-dark transition test, forced swimming test were determined at 1 d before the operation and at 14 d after the operation. Compared with the sham group, the MWL and TWL of the CCI rats were decreased significantly (P＜0.01), time in the light compartment and number of transition were decreased (P＜0.01), the immobility time in FST was also prolonged significantly (P＜0.01). At 14 days after CCI operation, the MWL and TWL of the ginsenoside-Rg2 groups were increased significantly (P＜0.01), time in the light compartment and number of transition were also shortened significantly (P＜0.01), the immobility time in FST was also shortened significantly (P＜0.01). Intraperitoneal injection of ginsenoside-Rg2 can inhibit the mechanical and thermal pain sensitivity of CCI rats,and can relieve depressive state.

Effect of Probe-Tone Frequency on Ipsilateral and Contralateral Electrical Stapedius Reflex Measurement in Children With Cochlear Implants.

The upper loudness limit of electrical stimulation in cochlear implant patients is sometimes set using electrically elicited stapedius reflex thresholds (eSRTs), especially in children for whom reporting skills may be limited. In unilateral cochlear implant patients, eSRT levels are measured typically in the contralateral unimplanted ear because the ability to measure eSRTs in the implanted ear is likely to be limited due to the cochlear implant surgery and consequential changes in middle ear dynamics. This practice is particularly limiting in the case of fitting bilaterally implanted pediatric cases because there is no unimplanted ear option to choose for eSRT measurement. The goal of this study was to identify an improved measurement protocol to increase the success of eSRT measurement in ipsilateral or contralateral or both implanted ears of pediatric cochlear implant recipients. This work hypothesizes that use of a higher probe frequency (e.g., 1000 Hz compared with the 226 Hz standard), which is closer to the mechanical middle ear resonant frequency, may be more effective in measuring middle ear muscle contraction in either ear. In the present study, eSRTs were measured using multiple probe frequencies (226, 678, and 1000 Hz) in the ipsilateral and contralateral ears of 19 children with unilateral Advanced Bionics (AB) cochlear implants (mean age = 8.6 years, SD = 2.29). An integrated middle ear analyzer designed by AB was used to elicit and detect stapedius reflexes and assign eSRT levels. In the integrated middle ear analyzer system, an Interacoustics Titan middle ear analyzer was used to perform middle ear measurements in synchrony with research software running on an AB Neptune speech processor, which controlled the delivery of electrical pulse trains at varying levels to the test subject. Changes in middle ear acoustic admittance following an electrical pulse train stimulus indicated the occurrence of an electrically elicited stapedius reflex. Of the 19 ears tested, ipsilateral eSRTs were successfully measured in 3 (16%), 4 (21%), and 7 (37%) ears using probe tones of 226, 678, and 1000 Hz, respectively. Contralateral eSRT levels were measured in 11 (58%), 13 (68%), and 13 (68%) ears using the three different probe frequencies, respectively. A significant difference was found in the incidence of successful eSRT measurement as a function of probe frequency in the ipsilateral ears with the greatest pair-wise difference between the 226 and 1000 Hz probe. A significant increase in contralateral eSRT measurement success as a function of probe frequency was not found. These findings are consistent with the idea that changes in middle ear mechanics, secondary to cochlear implant surgery, may interfere with the detection of stapedius muscle contraction in the ipsilateral middle ear. The best logistic, mixed-effects model of the occurrence of successful eSRT measures included ear of measurement and probe frequency as significant fixed effects. No significant differences in average eSRT levels were observed across ipsilateral and contralateral measurements or as a function of probe frequency. Typically, measurement of stapedius reflexes is less successful in the implanted ears of cochlear implant recipients compared with measurements in the contralateral, unimplanted ear. The ability to measure eSRT levels ipsilaterally can be improved by using a higher probe frequency.

(101) Using Quantitative Sensory Testing to Assess the Pain System in Sexual Assault Survivors

Trauma exposure, especially sexual assault (SA), is highly correlated with pain conditions, in that many chronic pain samples report trauma histories. However, our understanding of the mechanisms behind this relationship is limited. Previous findings from our lab suggest that SA disrupts descending pain modulation. However, to date, no study has used quantitative sensory testing (QST) to comprehensively assess the pain system in SA survivors. 41 healthy, pain-free SA survivors were matched to a group of 41 healthy, pain-free trauma exposed persons without SA (TE). These groups were compared to a group of healthy, pain-free persons with no trauma history (no-TE; N=62). QST included warm, cool, heat, cold, ischemia, and electric thresholds, and heat, cold, ischemia, and electric tolerances. The nociceptive flexion reflex (NFR) threshold was used to assess spinal nociception. Results suggested SA survivors had higher cool thresholds than the TE and no-TE groups. Moreover, SA survivors had lower cold thresholds, cold tolerances, and heat tolerances than no-TE. Surprisingly, SA survivors had higher ischemia tolerances than no-TE and TE groups. The TE group had lower heat and cold tolerances than the no-TE group. None of the other group differences were significant for any pain outcome. These findings suggest that SA is associated with greater sensitivity in A-delta fibers (cool thresholds) and hyperalgesia in response to thermal stimuli (heat, cold). However, hypoalgesia was noted in response to deep tissue pain (ischemia). By contrast, TE is primarily associated with reduced tolerance to heat and cold. These group differences are not likely due to spinal sensitization due to the lack of group differences in NFR. Future studies are needed to replicate these findings and determine whether QST responses can predict negative sequela of SA and non-SA trauma exposure.

Earplug-induced changes in acoustic reflex thresholds suggest that increased subcortical neural gain may be necessary but not sufficient for the occurrence of tinnitus

The occurrence of tinnitus is associated with hearing loss and neuroplastic changes in the brain, but disentangling correlation and causation has remained difficult in both human and animal studies. Here we use earplugs to cause a period of monaural deprivation to induce a temporary, fully reversible tinnitus sensation, to test whether differences in subcortical changes in neural response gain, as reflected through changes in acoustic reflex thresholds (ARTs), could explain the occurrence of tinnitus.Forty-four subjects with normal hearing wore an earplug in one ear for either 4 (n = 27) or 7 days (n = 17). Thirty subjects reported tinnitus at the end of the deprivation period. ARTs were measured before the earplug period and immediately after taking the earplug out. At the end of the earplug period, ARTs in the plugged ear were decreased by 5.9 ± 1.1 dB in the tinnitus-positive group, and by 6.3 ± 1.1 dB in the tinnitus-negative group. In the control ear, ARTs were increased by 1.3 ± 0.8 dB in the tinnitus-positive group, and by 1.6 ± 2.0 dB in the tinnitus-negative group. There were no significant differences between the groups with 4 and 7 days of auditory deprivation.Our results suggest that either the subcortical neurophysiological changes underlying the ART reductions might not be related to the occurrence of tinnitus, or that they might be a necessary component of the generation of tinnitus, but with additional changes at a higher level of auditory processing required to give rise to tinnitus. This article is part of a Special Issue entitled: Hearing Loss, Tinnitus, Hyperacusis, Central Gain.

Multi-electrode sequential versus single electrode stimulation to elicit the stapedial reflex during cochlear implantation: Correlation with maximum comfort level

ObjectivesTo assess whether electrical stimulation sequentially delivered through 4 electrodes located in different cochlear areas may elicit the stapedial reflex at lower levels compared to single electrode stimulation and to correlate the sequentially obtained values with the maximum comfort level (C-level). Patients and methodsA retrospective study was performed on 35 post-verbal adult patients (age 19–80 years) consecutively implanted in 2 cochlear implant centers, evaluating the level of stimulation (pulse width) necessary to electrically evoke the stapedial reflex with two different stimulation modalities: single electrode versus sequential 4 electrode stimulation. Threshold values were compared with C-level obtained at activation. ResultsThe average differences of pulse width and C-level were significantly smaller (P<0.0001) when the stapedial reflex was obtained with the sequential stimulation modality and reached statistical significance for every single electrode (P<0.0001). ConclusionsStapedial reflex thresholds obtained with sequential stimulation through 4 different electrodes significantly correlate to the C-level obtained at the first setting and may be helpful in defining the upper limit of the dynamic field during initial CI mapping.

Long term reliability of nociceptive withdrawal reflex thresholds

BackgroundThe nociceptive withdrawal reflex (NWR) is a polysynaptic spinal reflex protecting the body from harmful stimuli. Two different methods to assess its’ threshold (NWR-T) have been part of clinical trials concerning the evaluation of the nociceptive system in the human body. NWR-T’s are gathered by stimulation at the sole of the foot and over the sural pathway. Consequently, EMG analyzes the muscle activity over the biceps femoris and tibialis anterior muscle. Past studies favor stimulation at the sole of the foot. New methodThe two methods were compared concerning retest-reliability and subjective pain ratings. The retest-reliability was tested over a period of 21 days using an up-down staircase method. Reliability was evaluated with a Bland Altman agreement analysis. Subjective pain ratings were evaluated with a numeric rating scale (NRS). ResultsNWR-T assessment was successful for all subjects. The EMG muscle activity had larger reflex amplitudes for measurements of the tibialis anterior muscle. NWR-T values showed greater variability than NRS values. Comparison with existing methodThe retest-reliability over a period of 21 days showed stable NWR-T results for both stimulation sites, but superior reliability was gathered with stimulation at the sole of the foot. Subjects rated stimulation over the sural pathway as more painful. ConclusionsThe NWR-T upholds reliable measurements over a longer period of time and seems to be a stable measure for pain condition. Reliability estimations, EMG recordings, and subject’s rating show stimulation at the sole of the foot could be the better choice.

Abnormal visuo-vestibular interactions in vestibular migraine: a cross sectional study.

Vestibular migraine is among the commonest causes of episodic vertigo. Chronically, patients with vestibular migraine develop abnormal responsiveness to both vestibular and visual stimuli characterized by heightened self-motion sensitivity and visually-induced dizziness. Yet, the neural mechanisms mediating such symptoms remain unknown. We postulate that such symptoms are attributable to impaired visuo-vestibular cortical interactions, which in turn disrupts normal vestibular function. To assess this, we investigated whether prolonged, full-field visual motion exposure, which has been previously shown to modulate visual cortical excitability in both healthy individuals and avestibular patients, could disrupt vestibular ocular reflex and vestibular-perceptual thresholds of self-motion during rotations. Our findings reveal that vestibular migraine patients exhibited abnormally elevated reflexive and perceptual vestibular thresholds at baseline. Following visual motion exposure, both reflex and perceptual thresholds were significantly further increased in vestibular migraine patients relative to healthy controls, migraineurs without vestibular symptoms and patients with episodic vertigo due to a peripheral inner-ear disorder. Our results provide support for the notion of altered visuo-vestibular cortical interactions in vestibular migraine, as evidenced by vestibular threshold elevation following visual motion exposure.