Otology
Adnan Darr, Karan Jolly, Jameel Muzaffar in ENT Vivas, 2023
Acoustic reflex: Stapedius muscle in middle ear contracts in response to an intense sound Crossed vs uncrossedCN VIII > cochlear nucleus > SOC (bilateral) > FN nucleus (bilateral) > stapediusPattern of abnormality helps identify site of lesionNormal stapedial reflex threshold is 70–100 dB above the pure tone thresholdIf suspect retrocochlear pathology, test acoustic reflex decay: Decreased auditory perception with sustained stimulus
Psychoacoustic and Objective Assessment of Hearing
R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne in Scott-Brown's Essential Otorhinolaryngology, 2022
The result is shown on a chart called a tympanogram, which includes parameters of middle ear compliance/pressure, and the ear canal volume (ECV). The norms for compliance peak are values of 0.3 (or 0.2 for children) to 1.6 cm3 for adults. Low compliance indicates abnormal stiffness of the middle ear (i.e. otosclerosis or malleus fixation). Abnormally high compliance may indicate ossicular discontinuity or atrophic scarring of the eardrum. Different types of tympanogram traces are shown in Figure 4.4. Additional testing through the use of tympanometry includes long time-based tympanometry (Chapter 8) and the acoustic stapedial reflex. The latter is elicited by brief pure tones or noise bursts. The lowest intensity of sound that triggers the reflex is the acoustic reflex threshold (ART). An absent or abnormal stapedial reflex with normal middle ear pressure occurs in otosclerosis.
Auditory Neuropathy Spectrum Disorder and Retrocochlear Disorders in Adults and Children
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
Further study has permitted the characterization of this group of disorders, and better assessment of these patients. These cases are now recognized as relatively common (5–12% of those previously considered to have severe to profound hearing loss in paediatric populations,11,12 with an estimated 1 in 7000 of neonates, assessed by universal newborn hearing screening,13 showed abnormal VIIIth nerve function) and probably represent a heterogeneous group where the common feature is disordered temporal processing (i.e. synchronization of sound). Progressive AN is reported in association with age-related degenerative changes, toxic effects of noise, mitochondrial, genetic and autoimmune disorders, etc.14 The first large series15 identified 49 cases from 543 patients who had either no ABR response or absent waves III and V. In seven patients, the audiometric data ranged from normal hearing to moderate impairment, i.e. 14% had better hearing sensitivity than might have been expected from their ABR, which was completely absent in these cases. Each of these seven patients also had abnormal acoustic reflex findings. Although the range of deficits as identified on medical, behavioural and electrophysiological testing was variable, there were many common features, including perinatal insults such as perinatal asphyxia, hyperbilirubinaemia or head injury. Tests of psycholinguistic abilities revealed significantly worse performance in auditory as compared to visual tasks, and speech discrimination testing revealed worse scores than would have been predicted from the patient’s hearing thresholds in the majority.
Presence of ipsilateral acoustic reflex artifact may result in clinical misidentification
Published in International Journal of Audiology, 2022
Dorothy Neave-DiToro, Michael Bergen, Shlomo Silman, Michele B. Emmer
The acoustic reflex is a bilateral reflex that occurs within the middle ear due to the presentation of high intensity acoustic stimulation. The exact physiological function and the evolution of the reflex is still debated within the literature and numerous theories exist (McGregor et al. 2018). This reflex can be stimulated and measured in the same ear (ipsilateral testing) or can be measured in one ear while the stimulating tone is presented to the opposite ear (contralateral testing). Acoustic reflex testing is being used globally to aid in the detection of middle ear pathologies such as middle ear effusion, otosclerosis, and ossicular discontinuity (Silman and Silverman 1991; Hunter and Shahnaz 2013; Silman and Emmer 1995). Reflex testing has been used to aid in the prediction of hearing loss (Emmer and Silman 2003; Flamme et al. 2017), differential diagnosis of auditory neuropathy (Berlin et al. 2005; Emanuel, Henson, and Knapp 2012; Schairer, Feeney, and Sanford 2013; Flamme et al. 2017), non-organic hearing loss and those at risk for retrocochlear impairment such acoustic neuromas and cerebellopontine angle tumours by use of normative 90th percentile data (Silman and Gelfand 1981). Furthermore, the ipsilateral acoustic reflex threshold (IART) is found to be an important tool in the detection of facial nerve pathology (Silman et al. 1988). More recently, the use of ARTs to assess binaural summation (Rawool and Parrill (2018) and to aid in the diagnosis of noise-induced cochlear synaptopathy (Guest et al. 2019) has been discussed.
Peripheral and central auditory function in adults with epilepsy and treated with carbamazepine
Published in Hearing, Balance and Communication, 2019
Sherifa A. Hamed, Amira M. Oseily
In this study, more than one third of the patients had abnormalities in acoustic reflex (but normal tympanometry) and mild deficits in PTA and abnormalities in BAEPs indicating delayed auditory conduction within the peripheral pathways and brainstem. The acoustic reflex (stapedius) is an involuntary muscle contraction that occurs in the middle ear in response to high-intensity sound stimuli. The reflex decreases the transmission of vibrational energy to the cochlea, where it is converted into electrical impulses to be processed by the brain. The acoustic reflex normally occurs only at relatively high intensities; activation for quieter sounds can indicate ear dysfunction. The pathway involved in the acoustic reflex is complex and can involve the ossicular chain (malleus, incus and stapes), the cochlea (organ of Corti), the auditory nerve, brainstem, facial nerve and other components [44]. In the presence of normal tympanometry, the abnormal acoustic reflex might be attributed to abnormalities in auditory nerve or its pathway within the brainstem. The auditory abnormalities in BAEPs were obvious particularly at high repetition rate frequencies (milliseconds) of BAEPs than with low repetition rate frequencies [45–47]. The increased drug concentrations, dose and/or prolonged exposure to CBZ were found to be associated risks of auditory pathway dysfunction [48–51].
Objective evaluation of binaural summation through acoustic reflex measures
Published in International Journal of Audiology, 2018
Vishakha W. Rawool, Madaline Parrill
It should be noted that acoustic reflex threshold is not a direct measure of loudness perception. Acoustic reflex measures are not affected by factors such as variation in attention or fatigue levels while the psychoacoustic measures of loudness are prone to such confounding factors. However, there are some similarities between acoustic reflex and loudness measures. For example, a narrow-band stimulus has to be of higher intensity than a broad-band stimulus for equal perception of loudness and for recording acoustic reflex thresholds (reviewed in Scharf 1976). In addition, at least some studies show a significant correlation between acoustic reflex thresholds and loudness (Olsen 1999; Rawool 2001). Some studies may not show such relationships due to variation in methodologies for recording acoustic reflex thresholds and loudness perception. For example, instructions provided during the measurement of loudness perception can cause some variation (Olsen 1999). Due to the similarity between acoustic reflex and loudness measures, binaural summation measured using acoustic reflex thresholds may provide us an insight into the ability of an individual to benefit from the advantages provided by binaural summation such as easier detection of signals in the environment and better frequency and intensity discrimination (Jesteadt and Wier 1977; Hall and Fernandes 1983). In addition, objective measurement of binaural summation, through acoustic measures can allow the assessment of the functional integrity of the lower auditory brainstem, more specifically the superior olivary complex.