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A persistent stapedial artery is a congenital vascular malformation that can cause tinnitus and/or conductive hearing loss. Although rare, this case highlights the importance of recognizing aberrant anatomy as a potential cause of patients' symptoms. It also demonstrates how to recognize and treat patients with a symptomatic persistent stapedial artery. [ABSTRACT FROM AUTHOR]

Objective: This study sought to evaluate the demographics as well as clinical, audiometric, and surgical outcomes of patients who underwent endoscopic and microscopic stapedotomies. Methods: This study enrolled 87 otosclerosis patients who underwent endoscopic and microscopic stapedotomies. Results: In total, 44 and 43 surgeries were performed using an endoscope and a microscope, respectively. No significant difference was noted in the air--bone gaps of the cohort before or after the procedures (P = .611). Both procedures resulted in similar audiometric outcomes. The mean operative time was more significant in the last 22 patients of the endoscopic group than in the first 22 patients and patients who underwent microscopic stapedotomy (P = .027 and P = .018, respectively). Conclusions: Endoscopic stapedotomy exhibits a learning curve similar to that of other procedures. Patient outcomes were similar between the endoscopic and microscopic procedures. [ABSTRACT FROM AUTHOR]

Background: Otosclerosis is a disease of the osseous labyrinth. The disease causes 5% to 9% of all cases of hearing loss and 18% to 22% of conductive hearing loss. The treatment of choice is a surgery. The hearing improvement after the operation is determined by various factors. Aims/Objectives: The aim of the analysis is to determinate changes in hearing after stapedoplasty in view of surgery side in the patients operated on otosclerosis by right-handed surgeons. Material and Methods: The analysis involved patients hospitalized and operated on otosclerosis between 2012 and 2018. Only patients with their first middle ear surgery due to otosclerosis were included in the study. The patients were operated by 2 right-handed surgeons who used the same surgical technique and had similar experience in otosclerosis surgery. The study included patients who were divided into 2 groups: with self-tightening prosthesis and with manually tightening prosthesis. Results: The procedure performed by right-handed operators on the left side using prostheses requiring manual fixation on the incus was associated with poorer audiometric results compared to the results of surgeries on the right side. In patients with the self-tightening prostheses, the audiometric improvement of hearing was bilaterally comparable independently from operation side. Conclusion: (1) The dependence of hearing improvement on the surgery side was demonstrated in cases of surgeries performed on the left ear by right-handed surgeons, particularly with manually tightening prosthesis. (2) Self-tightening prostheses in stapedotomy limit the human factor, reducing the risk of complications after otosclerosis surgery and provide repeatable hearing improvement. [ABSTRACT FROM AUTHOR]

The study is aimed to assess the scope of endoscopic stapedotomy in overcoming technical challenges faced during conventional stapedotomy using operating microscope. Sixty-four patients with clinical and audiological diagnosis of otosclerosis were randomly assigned into one of the 2 groups—one underwent conventional stapedotomy using operating microscope, while the other group underwent endoscopic stapedotomy, the operating surgeon being the same for both groups, for all cases. The 2 groups were observed in terms of extent of the postero-superior canal bone curettage/drilling, chorda tympani repositioning, visualization of footplate area, surgical time from first incision to ear packing, post-operative morbidity in terms of post-operative pain, vertigo, hearing outcome, and changes in taste sensation. It was observed that irrespective of the width of the external auditory canal, endoscopic approach offered better access to the footplate area requiring lesser bone removal and chorda tympani repositioning. The operating time, post-operative pain, and changes in taste sensation were significantly less in the endoscopic group. However, no difference was noted in terms of the post-operative hearing outcome and incidence of vertigo. Endoscopic stapedotomy has clear advantages in terms of the technicality and accessibility to the working area as well as faster recovery. [ABSTRACT FROM AUTHOR]

Stapedius muscle even though being the smallest skeletal muscle in human body, it has a major role in otology. As many of the distinguished books in otology missed to explain much about stapedius muscle, and also considering the need for the anatomy based visit to this small muscle we felt it was important to have a exercise like this. In the dissection hall of our institution we dissected 32 cadaveric temporal bones and delineated stapedius muscle as a part of PG teaching programme to have a clear idea of the anatomy of stapedius muscle, its origin, attachment, extension, size (all dimensions). Length of the stapedius muscle varied between 9 and 11 mm. Stapedial tendon measured about 2 mm. The muscle had a classical sickle shape with tendon looking like the handle of the sickle. It has a bulky belly with a maximum breadth of 2-3 mm. It was found to be medial to midportion of vertical limb of facial nerve. All of our temporal bones measured size varied from 9 to 11 mm in length excluding stapedial tendon. Stapedial tendon measured almost 2 mm. Muscle is classical sickle shaped with tendon acting like the handle of the sickle. It has a bulky tummy which forms the maximum breadth of 1-3 mm. Why to have a clear idea about the anatomy of stapedius muscle is that, unless the anatomy is clear there is chance of confusing the muscle with that of facial nerve while doing facial nerve grafting and also while drilling for facial nerve decompression in experienced hands may get confused and decompress the muscle. Stapedius muscle said to be the smallest muscle in the body, but its not as small as its been described. Detailed awareness of the anatomy of stapedius muscle is needed so as to avoid confusion while facial nerve grafting and while drilling. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the possible role of cochlear outer hair cell function with TEOAE and DPOAE tests in patients with normal hearing and tinnitus. 25 tinnitus patients with normal hearing sensitivity selected as study group. Control group consist of 50 normal hearing subjects without tinnitus. All subjects had thresholds below 25 dBHL at frequencies 250–8,000 Hz, tympanogram type A and normal acoustic reflex thresholds. TEOAE were recorded with click stimulus at 80 dB SPL at 1,000, 2,000, 3,000 and 4000 Hz. DPOAE were measured at frequencies 1,000–8,000 Hz and intensity of L1 55 dB SPL and L2 65 dB SPL. Amplitude of DPOAE and TEOAE were decreased in all frequencies in study group. There was significant difference regarding prevalence abnormal TEOAE and DPOAE between study group and control group. There was relationship between dysfunction of outer hair cells and tinnitus in subjects with normal hearing. [ABSTRACT FROM AUTHOR]

Counter, S. Allen, Leo H. Buchanan, Fernando Ortega, Anthony B. Jacobs, and Göran Laurell. Assessment of the brainstem-mediated stapedius muscle reflex in Andean children living at high altitudes. High Alt Med Biol. 18:37-45, 2017.-This study examined the physiological thresholds, amplitude growth, and contraction duration of the acoustic stapedius reflex (ASR) in Andean children aged 2-17 years living at altitudes of 2850 m (Altitude I Group) and 3973 m (Altitude II Group) as part of a general medical assessment of the health status of the children. The brainstem-mediated ASR reveals the integrity of the neuronal components of the auditory reflex arc, including the cochlea receptors, eight cranial nerves, and brainstem neural projections to the cochlear nuclei, bilateral superior olivary nuclei, facial nerve nuclei, and facial nerve and its stapedius branch. Uncrossed (ipsilateral) and crossed (contralateral) ASR thresholds (ASRT), ASR amplitude growth (ASRG) function, and ASR muscle contraction duration (decay/fatigue) (ASRD) were measured noninvasively with 500, 1000 Hz and broadband (bandwidth = 125-4000 Hz) noise stimulus activators using a middle ear immittance system. Oxygen saturation (SaO2) level and heart rate were measured in a subsample of the study group. Statistical analyses revealed that the Altitude I and Altitude II groups had ASRT, ASRG function, and ASRD rates comparable to children at sea level and that the two groups were not significantly different for any of the ASR measures. No significant association was found between SaO2 or heart rate and ASRT, growth, and muscle fatigue rate. In conclusion, the assessment of the ASR in children in the high-altitude groups revealed normal function. Furthermore, the results indicate no adverse oto-physiological effects of altitude on the brainstem-mediated ASR at elevations between 2850 and 4000 m and suggest normal middle ear and auditory brainstem function. [ABSTRACT FROM AUTHOR]

Key Clinical Message We assessed the value of stapedius reflex testing as an objective measurement of striated muscle function in four patients with Pompe disease. Common tests of disease severity and efficacy of enzyme replacement therapy ( ERT) yield highly variable results that depend on patient cooperation and day-to-day performance, whereas stapedius reflex thresholds improved in seven of eight ears after 2 years of ERT. [ABSTRACT FROM AUTHOR]

Tinnitus is characterized by an auditory perception of sound, with no stimuli from the external environment. Tinnitus is an increasingly significant complaint, affecting 10-17% of the world population. As a symptom, it should always be considered with pathology in the auditory system. Our study aims to assess the relationship of this symptom with the presence of a stapedial reflex and the phenomenon of recruitment. Medical records of patients complaining of subjective tinnitus during their first consultation in the Outpatient Clinic of the Unicamp Teaching Hospital, in Brazil, between 2011 and 2012 were analyzed. We carried out a study with 65 non-randomized tinnitus individuals using questionnaires, clinical and audiological evaluations. The visual analogue scale was used to characterize the degree of disturbance caused by tinnitus. Statistical tests were performed using the IBM SPSS Statistics 19. No association was found between tinnitus and the presence of acoustic reflex or phenomenon of recruitment. We concluded that there is no relationship between tinnitus, the phenomenon of recruitment or the presence of an acoustic reflex. [ABSTRACT FROM AUTHOR]

The value of high-resolution CT scanning in diagnosing stapedial otosclerosis and in influencing surgical planning was studied. 40 cases, consisting of patients of both genders, above the age of 14 years, with a clinical diagnosis of otosclerosis underwent HRCT of the temporal bones. Images were acquired in axial plane, with a bone algorithm, keeping slice thickness at 0.5 mm and intervals of 0.5 mm. Reconstruction of the volume data set was done to obtain overlapping slices in various planes, so as to obtain the best possible images of the footplate of stapes. The thickness of the footplate was measured and the site of lesion was noted in these images. On exploratory tympanotomy, the footplate was assessed and graded according to a visual scale. HRCT was able to diagnose stapedial otosclerosis in 85% ears. It was able to identify the presence of a thickened footplate correctly with a sensitivity of 85.3% ( P value 0.16). It was able to correctly localize the site of otosclerotic focus in 85% cases ( P value <0.01). Thus, an estimate of the thickness of the footplate likely to be encountered and thus the amount of drilling likely to be required to create a fenestra; and the likely site of maximum thickness could be made pre-operatively. This study also established the value of multislice CT on the acquisition of such data. This method obviates the requirement of difficult patient positioning, reduces scanning time; while greatly improving the sensitivity of the scanning. [ABSTRACT FROM AUTHOR]

The article presents the discussion on Idiopathic intracranial hypertension (IIH) being a clinical syndrome due to the raised intracranial pressure (ICP) in the absence of a focal brain lesion and hydrocephalus. Topics include stretching or compression of various nerves due to the raised ICP producing several other neurological symptoms; and absence of stapedial reflex reflecting a severe disease or indicating a poor prognosis.

Introduction: The major objective of a stapedotomy is the restoration of hearing. In training centers, the hearing results obtained by resident physicians are lower than those achieved by more experienced surgeons. An analysis of the surgical results obtained by resident physicians is essential to identification of the deficiencies in the learning process. Objective: To analyze the postoperative hearing results obtained by otosclerosis patients who underwent stapedotomy performed by surgeons in a residency program. Methods: The pre- and postoperative audiometric results were evaluated in a retrospective study of 98 otosclerosis patients who underwent stapedotomy from January 2000 to December 2010. Results: The distribution of patients according to the postoperative results was as follows: 68.4% of the patients achieved a postoperative gap of less than or equal to 10 dB, and 91.8% of the patients achieved a postoperative gap of less than or equal to 20 dB. Three (3.1%) patients had profound sensorineural hearing loss after the procedure. Conclusions: An improvement in surgical outcomes of doctors in training is essential for the continuation of training for stapes surgery during medical residency. [ABSTRACT FROM AUTHOR]

Adaptation to constant vibration (acoustic oscillation) is likely to confer a specific morphology at the bone-tendon and bone-ligament interfaces at the ear ossicles, which therefore represent an exciting target of enthesis research. We histologically examined (i) the bone attachments of the tensor tympani and stapedius muscles and (ii) the annular ligament of the incudostapedial joint obtained from seven elderly donated cadavers. Notably, both aldehyde-fuchsin and elastic-Masson staining demonstrated that the major fibrous component of the entheses was not collagen fibers but mature elastic fibers. The positive controls for elastic fiber staining were the arterial wall elastic laminae included in the temporal bone materials. The elastic fibers were inserted deeply into the type II collagen-poor fibrocartilage covering the ear ossicles. The muscle tendons were composed of an outer thin layer of collagen fibers and an inner thick core of elastic fibers near the malleus or stapes. In the unique elastic fiber-mediated entheses, hyaluronan, versican and fibronectin were expressed strongly along the elastic fibers. The hyaluronan seemed to act as a friction-reducing lubricant for the elastic fibers. Aggrecan was labeled strongly in a disk- or plica-like fibrous mass on the inner side of the elastic fiber-rich ligament, possibly due to compression stress from the ligament. Tenascin-c was not evident in the entheses. The elastic fiber-mediated entheses appeared resistant to tissue destruction in an environment exposed to constant vibration. The morphology was unlikely to be the result of age-related degeneration. [ABSTRACT FROM AUTHOR]

Introduction: Serotonin seems to play a central role in tinnitus. The intensity dependence of auditory evoked potential (IDAP) is considered an index of central serotonergic activity in the auditory cortex. The higher the steepness of the N1/P2 component amplitude-stimulus function slope (N1/P2 ASF slope as calculated by IDAP), the lower the central serotonergic activity. Similarly, the N1 amplitude-stimulus function slope (N1 ASF slope) was investigated. Auditory brainstem responses (ABR) examine the auditory system functionality from the periphery and through the brainstem, where serotonergic projections have been identified. Objectives: Assessing whether tinnitus perception neurotransmitters activity inbalance could be investigated by an electrophysiological approach. Materials and Methods: Ten normoacousic tinnitus patients and 14 healthy controls were included in the study. Subjects underwent EEG (IDAP) recording, ABR recording and psychometric questionnaires administration. Results: N1/P2 ASF slope and N1ASF slope tended to have a greater steepness in patients. N1ASF slope was significantly correlated with ABR wave V and interpeak III-V latencies in patients. ABR wave V and interpeak III-V latencies were significantly longer in patients than in controls. Conclusion: N1/P2 ASF slope, N1 ASF slope and ABR components appear to be useful electrophysiologic methods to study possible functional alterations related to the serotonergic activity. [ABSTRACT FROM AUTHOR]

Scleraxis (Scx) is a basic helix-loop-helix transcription factor expressed in tendon and ligament progenitor cells and the differentiated cells within these connective tissues in the axial and appendicular skeleton. Unexpectedly, we found expression of the Scx transgenic reporter mouse, Scx-GFP, in interdental cells, sensory hair cells, and cochlear supporting cells at embryonic day 18.5 (E18.5). We evaluated Scx-null mice to gain insight into the function of Scx in the inner ear. Paradoxical hearing loss was detected in Scx-nulls, with ~50% of the mutants presenting elevated auditory thresholds. However, Scx-null mice have no obvious, gross alterations in cochlear morphology or cellular patterning. Moreover, we show that the elevated auditory thresholds correlate with middle ear infection. Laser interferometric measurement of sound-induced malleal movements in the infected Scx-nulls demonstrates increased impedance of the middle ear that accounts for the hearing loss observed. The vertebrate middle ear transmits vibrations of the tympanic membrane to the cochlea. The tensor tympani and stapedius muscles insert into the malleus and stapes via distinct tendons and mediate the middle ear muscle reflex that in part protects the inner ear from noise-induced damage. Nothing, however, is known about the development and function of these tendons. Scx is expressed in tendon progenitors at E14.5 and differentiated tenocytes of the stapedius and tensor tympani tendons at E16.5-18.5. Scx-nulls have dramatically shorter stapedius and tensor tympani tendons with altered extracellular matrix consistent with abnormal differentiation in which condensed tendon progenitors are inefficiently incorporated into the elongating tendons. Scx-GFP is the first transgenic reporter that identifies middle ear tendon lineages from the time of their formation through complete tendon maturation. Scx-null is the first genetically defined mouse model for abnormal middle ear tendon differentiation. Scx mouse models will facilitate studies of tendon and muscle formation and function in the middle ear. [ABSTRACT FROM AUTHOR]

The aim of the study was to systematize the key developmental phases of the stapedius muscle and the pyramidal eminence to clarify their formation, as well as to understand the variations and anomalies that can affect these structures. Sixty human embryos and fetuses between 38 days and 17 weeks of development were studied. The stapedius muscle is formed by two anlagen, one for the tendon, which derives from the internal segment of the interhyale, and another for the belly, located in the second pharyngeal arch medial to the facial nerve and near the interhyale but forming a completely independent anlage. In the interhyale, two segments were differentiated, these forming an angle; at the vertex, the belly of the stapedius muscle is attached. The internal segment is located from the attachment of the belly of the stapedius muscle to the anlage of the stapes, forming the anlage of the tendon of the stapedius muscle. The external segment completely disappears at the beginning of the fetal period. The pyramidal eminence is formed by an anlage independent of Reichert’s cartilage, from the mesenchymal tissue of the tympanic cavity, which condenses around the belly of the stapedius muscle from 12 weeks of post-conception development. The length of the tendon of the stapedius muscle in adults varies, depending on the attachment site of the belly of the stapedius muscle in the interhyale, which would determine the length of the internal segment (anlage of the tendon) and consequently the tendon length. This variation depends on the greater or lesser persistence of the angulation observed during development, between the tendon and the belly of the stapedius muscle. [ABSTRACT FROM AUTHOR]

Objectives: Objective measures mostly used to fit cochlear implants are the are the electrically evoked action potentials in the first place, followed by the electrically evoked stapedial reflex thresholds (ESRT). Several studies have shown that the general correlation between ESRT and subjectively measured comfort levels (MCL) is high (Hughes, 2012; Alvarez et al, 2007; Gordon, Papsin and Harrison, 2004; Lorens et al., 2004). ESRT variation due to stimulus duration needs to be investigate specially in the pediatric population regarding deviation according to stimulus length as well loudness. Material and methods: 26 children at the age less than 5 years, Med- El CI users, with all 12 active electrodes, with no cochlear malformation. Stimulation parameters as follow: burst duration: 100, 200, 300, 500 ms, stimulating electrodes: 2, 6, 9, 11. Results: For 13 children we managed to complete the procedure and to record ESR threshold for all mentioned durations, for seven children we receive no ESR response, for the rest -- we stopped the measurement. Conclusions: ESRT threshold values depend on such parameter as burst duration. Further measurements need to be done to find correlation between MCLs and objective threshold for different burst durati [ABSTRACT FROM AUTHOR]

Objectives: A novel setting for assessing the electrically evoked stapedius reflex threshold (ESRT) not requiring pre-ear-pressurization and not limited to a single probe frequency has been developed. Such a setting is currently being tested in a study enrolling adult and pediatric patients in subsequent age-blocks, running in Vienna (Austria) and Tübingen (Germany). Material: Patients implanted for at least 6 months with a Med-El cochlear implant (CI) are recruited in Vienna, Austria, and in Tubingen, Germany. After a successful tympanometry assessment and screening, ESRTs are measured with a commercially available tympanometry device for each active CI channel. Likewise, the ESRT measurement is also performed with the new setting without pre-ear-pressurization. Methods: Demographic data (age, gender, and hearing loss etiology and duration) were descriptively assessed. The median MCL values for each Med-El CI electrode obtained with a standard device and with the new setting were compared and assessed against the MCLs set during a behavioural fitting session. Results: At the time this abstract has been compiled we have enrolled 14 (8 in Vienna, and 6 in Tubingen) patients (6 male, 8 female). The average results show that the ESRT results obtained with a standard device and with our setting are very similar, but the ear probe stability and sensitivity might be greater using the experimental setting. The ESRT results of both settings are comparable with those of the behavioral fitting outcomes used to set the previous CI maps in terms of correlation. Conclusions: Our preliminary results show that measuring ESRT without requiring pre-ear-pressurization may become an interesting alternative for CI fitting. [ABSTRACT FROM AUTHOR]

Objective: Objective fitting of cochlear implants (CI) still represents an important challenge in the audiological field. Reliable and reproducible fitting procedures might significantly contribute to improve the clinical benefits introduced by the CI's, most of all in non-compliant patients. Furthermore, potential development of next generation smart CI processors would greatly depend on a reliable and objective fitting methodology. Finding methodologies providing reliable monitoring of the stapedius reflex (SR) and detection of the SR threshold (SRT) -- given its acknowledged correlation with the most comfortable loudness levels (MCL) -- is therefore a crucial aspect. The retrofacial approach is a surgical procedure allowing a direct intraoperative access to the stapedius muscle (SM) unlocking the possibility of neurophysiological monitoring of the SM and the measurement of its electromyographic signal. Aim: The aim of the current study is to test the feasibility of intraoperative recording of SM electromyographic (EMG) signals related to acoustically and electrically evoked SR in single sided deaf CI candidates. Material and methods: A multicentred clinical study was set up in Tübingen and Jena, to assess SR-related EMG responses in 7 single-sided CI-patients. During standard CI implantation surgery to reach the belly of the stapedius muscle (SM), an EMG electrode was placed on the muscle belly. Access to SM was performed via either a retrofacial approach, or from drilling of the pyramidal eminence (PE), according to individual anatomy and pre-operative planning. During a pre-surgical decisional phase, 3D reconstructions produced after manual segmentation of Dyna Computed Tomography (Dyna-CT) images of the CI patient's temporal bone were evaluated. 3D renderings were available for consultation along all the duration of the surgery. Elicitation of the reflex was done via both contralateral acoustic stimulation (via tympanometer) and ipsilateral electrical stimulation (via the CI). Several frequencies and intensities were used for acoustic stimulation, as well as several CI channels were stimulated at different intensities during electrical stimulation. CI stimulation was performed at 250 pulses per second, in order to allow stimulation artefacts to be almost completely differentiated from EMG spikes, which enabled artefact removal and not only basic filtering during post-processing of the data. The contraction of the SM (movement of the stapedius tendon) was assessed visually via the microscope to determine whether a SR was present, and at the same time EMG recordings were performed to obtain the neurophysiological response. EMG measurements were analysed in post-processing, but for most supra-threshold stimulations, EMG spikes were clearly seen on the raw unfiltered signal during the trials. Results: The muscle was accessed via retrofacial approach in 71% of the cases (5/7 patients) and via anterior approach in 43% of the cases (3/7 patients). On 1/7 cases both approaches were performed following intraoperative decision of the surgeon since the anatomy allowed it. SR -- EMG signals were successfully recorded in 71% of the cases (5/7 patients). EMG-based thresholds were calculated based on the signal-to-noise ratio during the stimulation, data analysis showed a Pearson correlation of 0.95 between the thresholds detected via EMG and those detected visually by the surgeon -- movement at the level of the stapedius tendon. The EMG signal showed a high sensitivity, being detected even before the visual confirmation in 33% of the assessed cases. Conclusions: Our results confirmed that it is possible to reliably record SRrelated EMG signals intraoperatively. The methodology for accessing the SM and subsequent electrode placement was found safe and effective, following an imaging-based pre-operative evaluation. [ABSTRACT FROM AUTHOR]

Introduction: Surgical treatment is a standard procedure in cases of otosclerosis and other conditions connected with stapes immobilized in the oval window niche. The most often applied treatment is stapedotomy, meaning the replacement of the immobilized stapes by a prosthesis. The properly conducted operation provides stabile hearing improvement. Aim: The paper aims to present failures after stapedotomy operations, audiometric indications for the future operation, and postoperative changes occurring within the middle and inner ear in comparison to the hearing and balance examinations' results. Material: The authors of the paper conducted a retrospective analysis of the reoperation cases after prior stapedectomies and stapedotomies performed in our clinic and in other clinics. The authors present causes of the airbone gap occurring postoperatively, as well as other difficult conditions after repeated operation. The authors discuss indications for reoperations and possibilities of the middle ear reconstructions. Results: Treatment is assessed based on the long term followup of the patients, otoscopic examination and results of pure tone audiometry and analysis of intraoperative assessments. Conclusions: Correctly performed operation with properly chosen prosthesis allows obtaining hearing improvement with closure of the air-bone gap. Reoperation is always a great challenge for the surgeon, and it requires experience and skills to reconstruct the middle ear. Proper assessment of the patient's condition before next operation allows lower the surgical risk and helps to choose surgical tactics. [ABSTRACT FROM AUTHOR]

Stapedius motoneurons (SMN) mediate the contraction of the stapedius muscle, which protects the inner ear from injury and reduces the masking effects of background noise. A variety of inputs to SMNs are known to exist, but their terminal ultrastructure has not been investigated. We characterized the synaptic terminals on retrogradely labeled SMNs found just ventromedial to the facial motor nucleus. About 80% of the terminals contained round synaptic vesicles. One type (Sm Rnd) had small, round vesicles filling the terminal with occasional dense core vesicles and formed an asymmetric synapse. Sm Rnd terminals were small with lengths of apposition to the SMN less than 3 microm. Partial reconstructions from serial sections demonstrated that these terminals formed up to three synapses per terminal. Another terminal type (Lg Rnd) had large, round vesicles and asymmetric synapses. Most Lg Rnd terminals were small but some were extensive, e.g., abutting the SMN for up to 10 microm. One of these terminals formed at least seven synapses. Another terminal type (Pleo) had pleomorphic vesicles and symmetric active zones that, in some cases, were invaginated by spines from the SMN. A fourth uncommon terminal type (Het Rnd) had round vesicles of heterogeneous sizes and asymmetric synapses. A fifth rare terminal type (Cist) had large, round vesicles and an accompanying subsurface cistern in the SMN. These were generally the same kinds of terminals found on other motoneurons, but the high proportion of round vesicle synapses indicate that SMNs receive mostly excitatory inputs. [ABSTRACT FROM AUTHOR]

Otoacoustic emissions (OAEs) are useful for studying medial olivocochlear (MOC) efferents, but several unresolved methodological issues cloud the interpretation of the data they produce. Most efferent assays use a ‘probe stimulus’ to produce an OAE and an ‘elicitor stimulus’ to evoke efferent activity and thereby change the OAE. However, little attention has been given to whether the probe stimulus itself elicits efferent activity. In addition, most studies use only contralateral (re the probe) elicitors and do not include measurements to rule out middle-ear muscle (MEM) contractions. Here we describe methods to deal with these problems and present a new efferent assay based on stimulus frequency OAEs (SFOAEs) that incorporates these methods. By using a postelicitor window, we make measurements in individual subjects of efferent effects from contralateral, ipsi-lateral, and bilateral elicitors. Using our SFOAE assay, we demonstrate that commonly used probe sounds (clicks, tone pips, and tone pairs) elicit efferent activity, by themselves. Thus, results of efferent assays using these probe stimuli can be confounded by unwanted efferent activation. In contrast, the single 40 dB SPL tone used as the probe sound for SFOAE- based measurements evoked little or no efferent activity. Since they evoke efferent activation, clicks, tone pips, and tone pairs can be used in an adaptation efferent assay, but such paradigms are limited in measurement scope compared to paradigms that separate probe and elicitor stimuli. Finally, we describe tests to distinguish middle-ear muscle (MEM) effects from MOC effects for a number of OAE assays and show results from SFOAE-based tests. The SFOAE assay used in this study provides a sensitive, flexible, frequency-specific assay of medial efferent activation that uses a low-level probe sound that elicits little or no efferent activity, and thus provides results that can be interpreted without the confound of unintended efferent activation. [ABSTRACT FROM AUTHOR]

Ipsilateral and contralateral stapedius muscle contractions were studied as functions of the sound pressure level (SPL) and duration of 2-kHz tone bursts. The study complemented a preceding study in which temporal summation of stapedius muscle contractions produced by pairs of short tone bursts was determined and analyzed. The muscle contractions were determined indirectly by measuring changes in the acoustic impedance they produced at the tympanic membrane. The data for the stapedius muscle contraction as a function of tone-burst duration were derived from another study and analyzed in part with the help of the SPL functions obtained in the present study. According to the experimental results, the stapedius muscle contraction produced by contralateral stimulation follows a compressive power function paralleling both the cochlear output and loudness functions. The ipsilateral contraction follows an expansive power function. Mathematical analysis showed that the muscle tension due to contralateral stimulation increases with tone duration approximately according to the characteristic of a linear integrator having an exponentially decaying memory with a time constant that increases with SPL from ≈200 to 370 msec. The simple relationship appears to be possible because of mutual cancellation of neural-processing characteristics preceding and following the temporal integration. [ABSTRACT FROM AUTHOR]

Determines human stapedius-muscle contractions in response to three-kilohertz, 20-millisecond tone bursts by measuring the associated acoustic-impedance changes at the tympanic membrane with an acoustic bridge. Temporal additivity of the muscle responses; Summation time constant; Evidence that the magnitude of the muscle response obeyed a compressive function paralleling the loudness function.

Preservation of stapedius muscle and incudo-stapedial joint during stapedotomy for otosclerosis is the motto of the dat. The Study was carried out in 500 patients. In Group A (n = 140), the stapedius muscle and incudostapedial joint were preserved. In Group B (n = 360), the stapedius muscle was cut. One month after surgery in Group A patients, the Stapedius-Reflex (SR) was evoked in 75% and three months later in 90%. The mean Loudness Discomfort Level (LDL) after one month of surgery in Group A was 95dB while three months after it was increased to 110dB. Speech discrimination score (SDS) in Group A with 80 dB suprathreshold is 93% and in Group B it is only 72%. This study established the fact that the preservation of stapedial muscle and incudo stapedial join is beneficial and essential, whenever possible, in the surgery for otosclerosis. [ABSTRACT FROM AUTHOR]