A Novel Water Method for Reducing Air Conduction in Soft Tissue Conduction

Auditory sensation can be elicited by applying a bone conduction vibrator to skin sites on the head, neck, and thorax over soft tissues. This is called soft tissue conduction (STC). We hypothesized that introducing substances with acoustic impedances that sharply deviate from those of soft tissues, such as air pockets, into the soft tissues beneath soft tissue stimulation sites would have an effect on the auditory threshold to stimulation at skin sites over soft tissue. In human subjects, we assessed the auditory threshold with a bone vibrator applied to several STC sites, especially the cheek, and to several bone conduction sites on the skull. The subjects were equipped with bilateral earplugs. The subject then filled his or her cheek with either air or water, and the auditory threshold was again determined. We also recorded the auditory brain stem response to STC stimulation under the chin in fat sand rats in the absence and presence of subcutaneous air or saline solution pockets (0.4 mL) under the chin. In humans, the threshold to stimulation on the cheek was elevated (13 to 18 dB) in the presence of an air-inflated cheek, but not with a water-filled cheek. In animals, in the presence of an air pocket, the auditory brain stem response threshold was elevated by 10 to 20 dB; no threshold change occurred with a saline solution pocket. The introduction of air (but not water) into the soft tissues beneath the soft tissue stimulation sites led to a threshold elevation in both humans and animals. This was not the case when an identical volume of water was introduced, which would also have interrupted a possible parallel bone conduction pathway. These results provide evidence that soft tissue stimulation at low intensities induces tissue vibrations that are transmitted to the cochlea along a series of soft tissues with similar acoustic impedances.

This study compared the intelligibility of speech delivered via three transducers: a TDH-39 earphone, a Pracitronic KH 70 bone vibrator, and a Radioear B-72 bone vibrator. CID W-1 spondees were presented to normal-hearing listeners via each transducer over a range of intensity levels. Functions relating the percentage of spondees correctly identified to stimulus level were similar for the three transducers, and notably, their slopes were comparable. This suggests that it is appropriate to use the W-1 word lists to determine speech reception thresholds (SRTs) with the KH 70 and B-72 bone vibrators, even though these word lists were originally developed for testing by air conduction. Our subjects also identified NU-6 monosyllabic words equally well for each transducer when the words were delivered at 40 dB above SRT. This result suggests that it is also valid to deliver the NU 6 speech test via the two types of bone vibrators.

This study was designed to map the sites on the skin of the head, neck and thorax at which a clinical bone vibrator elicits auditory sensation. In 10 subjects with normal hearing, a bone vibrator delivering a 2000-Hz warble tone, at an intensity which was at least 5 dB below the intensity which elicited a sensation by air conduction over each site, was applied to 25 sites with an application force of 500 g. Auditory sensations were elicited at many soft tissue (underlying bone >1 cm below the skin) and osseous (bone <0.5 cm below the skin) sites on the head, neck and thorax in all subjects, down to the sternum and thoracic vertebrae. Therefore, auditory vibrations induced at many sites on the head, neck and thorax can reach the cochlea and elicit auditory sensation.

FigureThere is a different type of hearing device called the Baha® bone conduction implant, also known as an osseointegrated auditory prosthesis, that is made especially for people with a long history of sick ears and ear surgeries. Such patients tend to be frustrated with their poor hearing and are often nervous about the risk of another ear infection. They also want to avoid more ear surgery at all costs. If the health of the ear can be stabilized, which is often a challenge, a conventional hearing aid may be used. Unfortunately, ear infections tend to recur, making regular hearing aids contraindicated for long periods of time. Years ago we fitted people who had this problem with a bone conductor on a headband attached to a high-power, body-worn hearing aid. Some of these fittings brought much happiness to patients who after not hearing sound for many years suddenly could hear well. The down side of this type of fitting is the wear and tear that the vibrator and the headband inflict on the wearer's head. The band is often too loose or too tight. It is hard to keep in place, and it is uncomfortable to wear. Extended use of the vibrator leads to an indentation in the patient's head created by the constant pressure exerted by the bone vibrator, which eventually erodes the bone directly under the vibrator. We usually try to fix this problem by moving the vibrator to the opposite side of the head, but eventually patients move it back to the original spot because it allows them to hear better. Developed in Sweden in 1977, Baha received FDA clearance for use in this country in 1996. Cochlear purchased Entific, the company that made it, in 2005. HOW IT WORKS Implanting the Baha is a relatively simple surgical procedure. A prosthesis is screwed into the mastoid. Then, 3 to 6 months later, the Baha sound processor is attached to the prosthesis with a coupler. For people who have good hearing via bone conduction and poor hearing via air conduction, this can work extremely well. The amplified sound bypasses the defective outer and middle ear and goes directly into both inner ears. The quality of hearing is described as quite good. Currently, Baha implantation is restricted to people age 5 years and above. Before that age, a child may use a Baha sound processor worn on a soft band and used similarly to a conventional bone-conduction hearing aid. After surgery, the child may use the same Baha sound processor on the implant and abutment. The reason for restricting implantation by age is that younger children are thought to have immature bone density, which may not permit good osseointegration. To ensure osseointegration with pediatric patients, it is recommended that the sound processor not be attached to the prosthesis until 6 months after surgery. In adults the waiting period is usually 3 months. Figure 1 shows the parts of the Baha. The separate piece in the photo is the small titanium implant that is screwed into the bone behind the patient's ear. New bone tissue grows around the implant securing it to the head. The implant is attached to an abutment that connects it to the hearing aid. The main part of the system is the sound processor, which receives the sound, amplifies it, and then transfers it to the patient via vibrations.Figure 1: The Baha system.ADVANTAGES For appropriate candidates, Baha has several benefits over alternative fittings: Feedback is reduced or eliminated. There is no discomfort from wearing a large, tightly fitting earmold. The conductive hearing loss is bypassed so the power requirement is lower. Reducing the required gain results in less saturation and distortion. There is no headband to wear. Because Baha is perceived as a surgical procedure rather than a hearing aid, it is currently approved by Medicare and many insurance companies. ACCESSORIES Various accessories can be used with Baha. Direct audio input is available so the patient can connect to a stereo, TV, or MP3 player. The unit can be used with a Microlink FM receiver to help with classroom situations and hearing in noise. A telecoil unit can be used to improve telephone listening. SUMMARY If conventional hearing aids or ear surgery does not provide a patient with good hearing, then a Baha should be considered. Its use is indicated when feedback is intractable and/or when the patient suffers from irritated ears or has malformed ears or ear canals. The Baha is also sometimes recommended for single-sided deafness.

In this paper we present three experiments to measure the control parameter space of apparent haptic motion using a variety of stimulation attributes and body sites. In Experiment 1 we measured the range of Stimulus Onset Asynchrony (SOA) that created the percept of continuous motion between two vibrating points on the dorsal forearm and on the back by varying the frequency, intensity and duration of stimulation. The SOA space for apparent motion varied with duration and body site but not with frequency and intensity of stimulation. In Experiment 2 we measured the SOA space for moving sensations when direction of motion and spacing between actuators were varied. On the forearm the SOA space was influenced by both the direction and spacing. However, on the back it was only affected by the direction of actuation. Finally, in Experiment 3 we measured the SOA space using four or more actuation points, creating two-dimensional apparent motion. The results of the present study are discussed in the context of designing haptic contents for movies, amusement rides and video games.

The magnitude and origin of audiometric air-bone gaps in the range 3 kHz to 8 kHz was investigated in 20 normal subjects. The average gap ranged from a minimum of about 3 dB at 3 kHz to a maximum of about 19 dB at 6 kHz. Approximately 5 dB of the gap at high frequencies is caused by excess air-radiated sound from the bone vibrator. A larger error appears to result from discrepancies between the air and bone conduction standards to which audiometers are calibrated. These errors may influence diagnosis and we recommend that bone conduction tests at frequencies greater than 4 kHz are avoided. These findings have implications for medico-legal work where small air-bone gaps have diagnostic significance.

Intra-operative subcortical electrical stimulation: A comparison of two methods

There is evidence that sensitivity to noxious stimuli differs between the sexes and across the body, but few studies have investigated differences in the perception and experience of acute pain stimuli across the body in healthy individuals. We recruited 52 healthy participants, aged 18-36 (50% men) and administered 39, 42 and 45°C stimuli at four body sites bilaterally to examine differences in the experience of pain intensity and unpleasantness between body sites via an 11-point numerical rating scale. Noxious and innocuous thermal heat stimuli were perceived as significantly more intense when delivered to the wrist (M=3.98, SD = 1.93) and back (M =4.07, SD=1.98) compared to the shoulder (M=3.45, SD=1.91) and leg (M=3.46, SD=1.87). Pain unpleasantness ratings yielded similar findings; stimuli were perceived as more unpleasant when administered to the wrist (M=2.83, SD=1.93) and lower back (M=3.04, SD=2.11) compared to the shoulder (M=2.63, SD=1.85) and leg (M=2.26, SD=1.82). These findings suggest that painful thermal stimuli delivered to the wrist and back are perceived as more intense and unpleasant compared with other body sites in healthy persons. These differences may be due to variations in receptor density, or the relative importance of these sites for daily living and survival. Moreover, these insights are helpful for the design of studies investigating pain experience in healthy persons in experimental or clinical settings. WHAT DOES THIS STUDY ADD?: We tested sensitivity to acute suprathreshold thermal stimulations across a range of body sites to investigate for potential variability. We found significant differences in the perceived intensity and unpleasantness of noxious and innocuous thermal stimuli at the wrist and lower back, compared with the shoulder and leg. These results suggest that pain experience is driven by receptor density or the relative functional importance of these sites.

It is a well-known fact that the categorical judgment on a stimulus is generally influenced by the context, but systematic studies on quantitative aspects of the context effect are rather few. The present study investigated the influence of the relative positions of the target and context stimuli both on the stimulus continuum and on the time axis. The influence of stimulus attributes was also investigated using pure tones, complex tones with a formant structure, and synthetic vowel sounds. The results indicated the existence of a gradual transition from assimilation to contrast in almost all cases studied, the contrastive effect becoming more intense with increased stimulus complexity in nonspeech stimuli and most intense in speech stimuli. An interpretation of the results is presented on the basis of a model for the process of categorical judgment. [Work supported by Grant-in-Aid for Scientific Research from the Ministry of Education.]

Evaluate whether elevating the tympanic membrane from the malleus during endoscopic tympanoplasty may negatively affect postoperative hearing outcomes or perforation rates by comparing 2 similar endoscopic tympanoplasty techniques. Retrospective cohort. Tertiary care center. Endoscopic over-under cartilage tympanoplasties age and gender matched to endoscopic underlay cartilage tympanoplasties between January 2015 and January 2019. Exclusion criteria included preoperative or intraoperative cholesteatoma, performance of mastoidectomy or ossicular chain reconstruction, and lack of postoperative audiogram. Endoscopic cartilage tympanoplasty via over-under or underlay technique. Pre- and postoperative pure-tone average and word recognition score, graft success. A total of 52 patients were evaluated: 26 endoscopic over-under cartilage tympanoplasties were matched to endoscopic underlay cartilage tympanoplasties. Both groups demonstrated a statistically significant improvement in air conduction hearing (9 dB [P < 0.001] and 6 dB [P < 0.01], respectively), and bone pure-tone average did not worsen in either group (P < 0.001 and P < 0.05, respectively). Postoperative air conduction pure-tone average was statistically noninferior in the over-under group compared with the underlay group (P < 0.05). Reperforation was present in 3 patients (12%) in the underlay group and none in the over-under group, but this difference was not statistically significant (P = 0.24). Endoscopic over-under cartilage tympanoplasty effectively closes tympanic membrane perforations and improves hearing, without greater risk than underlay tympanoplasty. Elevating the tympanic membrane from the malleus does not confer worsen hearing outcomes.

Eosinophilic Otitis Media (EOM) is an intractable disease caused by type 2 inflammation, such as Eosinophilic Chronic Rhinosinusitis (ECRS) and bronchial asthma. Biologics have recently been used to treat ECRS and bronchial asthma. Biologics are not indicated for EOM; however, because approximately 10% of ECRS cases has concomitant EOM, concomitant EOM improvement has been observed when dupilumab is administered for ECRS. Therefore, we aimed to investigate the current status of EOM treatment and clarify the effect of dupilumab on EOM. This retrospective study included 25 patients attending our hospital. The disease status of patients with EOM not treated with dupilumab (control) and those treated with dupilumab at the time of evaluation were compared. The EOM disease status was compared using the EOM severity score, temporal bone shadow on Computed Tomography (CT), and standard pure tone audiometry. Twenty-four of the 25 patients with EOM had concomitant ECRS, and 12 were administered with dupilumab. The severity score of EOM, temporal bone CT score, and air conductance hearing were significantly improved after dupilumab administration in 12 patients with EOM. Comparison of EOM patients without dupilumab (control) and those treated with dupilumab at the time of evaluation revealed that the severity score of EOM, temporal bone CT score, and air conduction hearing were significantly better in patients treated with dupilumab. Our study demonstrated that dupilumab was administered to approximately half of the patients with EOM, suggesting that the treatment of EOM has undergone significant changes due to dupilumab administered to ECRS. Our study also suggests that dupilumab is highly effective in patients with EOMs.

Antinociception and cardiovascular responses produced by electrical stimulation in the nucleus tractus solitarius, nucleus reticularis ventralis, and the caudal medulla

Electrical stimulation of the brachioradialis branch of the radial nerve inhibits the discharge of motor units in biceps brachii. Because the distal portion of brachialis is also innervated by a branch of the radial nerve, however, there is uncertainty over the origin of the inhibitory projection to the motor units in biceps brachii. PURPOSE: To determine the extent to which inhibition of the biceps brachii motor neuron pool with radial nerve stimulation is mediated by afferent projections from the brachioradialis or brachialis. METHODS: Stimulating electrode location was optimized for both the brachioradialis and brachialis branches of the radial nerve by observing the electrically evoked motor responses from the interference electromyogram of both muscles. Six male subjects produced low elbow flexion forces (2.8 ± 1.6 %MVC) to maintain the discharge of a biceps brachii motor unit at 11.1 ±0.8 pps. Stimulation was applied every 2 – 3 s with a 30-ms delay after the discharge of the motor unit. Stimulus intensity was 0.9x motor threshold (MT). Pre- and post-stimulus time histograms were constructed from the 108 ±12 stimuli that occurred during the discharge of the motor units. The influence of the two stimulus locations was assessed on the same biceps brachii motor unit. Inhibition was quantified as the percent change from the pre- to post-stimulus interspike intervals. RESULTS: Seven motor units were recorded for each stimulation location. To determine the selectivity of stimulation, motor thresholds were identified for both muscles at each stimulation site. There was a limited capacity to selectively stimulate either nerve branch; the stimulus intensity (0.9x MT) for each muscle corresponded to ∼0.73x MT for the other muscle. Despite this limited selectivity, the magnitude of inhibition on biceps brachii motor units was significantly less (P <0.05) when stimulation was optimized for the brachialis branch of the radial nerve (3.4 %) than the brachioradialis branch (6.5 %). CONCLUSION: These data suggest that either there are fewer inhibitory afferent projections from radial nerve-innervated brachialis than from brachioradialis or that brachialis afferents do not inhibit biceps brachii motor units and the observed inhibition was due to activation of brachioradialis afferents at a lower stimulus intensity. Inhibition of biceps brachii motor units with radial nerve stimulation appears to be primarily mediated by afferents from the brachioradialis muscle. Supported by NINDS R01 NS43275.

Background Hearing results of endoscopic and microscopic tympanoplasty have been compared using the average pure tone threshold which could conceal subtle differences at a specific frequency. Objectives To compare frequency-specific hearing outcomes of endoscopic and microscopic tympanoplasty. Material and methods The study included 42 patients who underwent endoscopic or microscopic type I tympanoplasty. The medical charts of these patients were reviewed retrospectively. We evaluated the pure tone audiometry at 250, 500, 1000, 2000 and 4000 Hz, including bone conduction (BC), air conduction (AC) and air-bone gap (ABG) before and after the surgery. The main outcome measures were frequency-specific pre- and post-operative hearing thresholds and the corresponding changes. We also assessed the graft success rate and surgical complications. Results BC revealed a significant aggravation at 4000 Hz in microscopic tympanoplasty group, but no significant differences between the two groups at any frequencies. Both groups showed improvements in AC and ABG at all frequencies, without significant differences between the two groups at any single frequency. The maximum improvement of AC and ABG was found at 250 Hz. The graft success rate and operative complications were also similar. Conclusions and significance The frequency-specific hearing outcomes of endoscopic and microscopic tympanoplasty are similar.

Considering the aging population, the prevention of falls will become increasingly importance. One of the causes of an elderly people fall is the increase of the center of gravity deflection. Therefore we thought about stimuli to vibration receptor. The purpose of this study is to suppress the center of gravity deflection by giving planta pedis stimuli by single frequency vibration. We made a simple vibration stimulator which can give 225Hz vibration stimuli to planta pedis on three points. This frequency was decided by our prior study. The vibration stimuli points are heel, the root of big toe and the root of a little toe. The intensity of stimuli is set to 90% of the smallest stimuli intensity that the subject can feel it. We evaluated the effect of vibration stimuli by time duration of one-leg standing with closed eyes and the locus of the center of gravity deflection. The results showed that the time duration extended and the trajectory of the center of gravity deflection decreased even in only one point stimulation. Most effective point was the root of big toe. Our result is that the vibration stimuli to planta pedis are useful for fall prevention of elderly people.Keywordsfall preventionvibration stimulisine wavecorpuscle of Vater-Pacini