Before explaining about the psychoacoustical test related recruitment phenomenon, the Equal Loudness Contours and Loudness Growth Curve are described first. It is necessary to conduct the loudness recruitment test for the differential diagnosis of cochlear impairment. In cases of unilateral moderate sensorineural hearing loss, the alternate binaural loudness balance (ABLB: Fowler) technique must be tried initially. The ABLB technique and a few problems associated with its use are described. The difference limen (DL) tests, including not only intensity DL but also frequency DL and duration DL, are explained with a review of the audiologic literature. Further, the procedure for the short increment sensitivity index (SISI) test is explained in detail. Today, the SISI test is used more frequently than the DL test clinically. The procedure and evaluation of short-tone threshold audiometry are explained. Despite the apparent simplicity of hearing tests, it is clinically difficult to obtain precise values.
We investigated the distribution of behavioral hearing thresholds and auditory steady-state response (ASSR) thresholds in infants and children showing no click-evoked auditory brain stem responses (ABRs) at 105dBnHL. The conditioned orientation response (COR) thresholds in 28 infants and children aged 9 to 32 months showing no click-ABR varied from 58 to 113dB HL in the speech frequency range. 32% of the subjects had aided COR thresholds at levels <60dB HL. These results indicate that absent ABR does not rule out useful residual hearing. Therefore, ASSR testing was carried out in 19 infants and children with absent ABR. ASSR thresholds were present in 87% of the ears at 1000Hz even when click=ABRs were absent. The ASSR technique may quantify hearing losses in the severe to profound range, and indicate some amount of residual hearing.
In 2005, a newborn hearing screening program (NHSP) was carried out for about 70% of all newborn babies in Tottori prefecture, while a hearing screening program conducted at the regular-health examination for 3-year-old children (HS for 3-year-olds) has been carried out for over 90% of all 3-year-old children. We analyzed the data from 31 infants who failed the NHSP and were referred to Tottori University Hospital to undergo diagnostic testing from April 2002 to March 2005. We also analyzed the data from 12 children who failed HS for 3-year-olds from April 2005 to March 2006. Regarding NHSP, 14 out of 31 (45.2%) infants had normal hearing (<40dB hearing level), while 10 (32.3%) were confirmed to have a hearing loss. Automated auditory brainstem response yielded a lower false positive rate (37.5%) than the automated otoacoustic emissions (50%). Regarding HS for 3-year-olds, 6 out of 12 (50%) children had normal hearing, while 6 (50%) were confirmed to have a hearing loss. In addition, 6 had otitis media with effusion (OME). The establishment of comprehensive hearing screening program for both NHSP and HS for 3-year-olds is considered to be needed in order to identify and treat child hearing impairment in an effective manner.
Neonatal Hearing Screening (NHS) was started for half of the newborn babies in Akita Prefecture in November 2001, the other half undergoing conventional hearing checkups with the Hearing Development Checklist used by Pediatricians and Health Nurses. In Nakadohri Hospitial, 35 babies were diagnosed to have both ABR and a list (high or low) score by three months of age. Twenty-one cases had normal hearing and almost full scores. Two cases of severe hearing loss had very low scores. One case with moderate hearing loss also had a very low score, whereas another had a very high score; this later case was proved to have high-frenquency hearing loss. A girl with 80dB in the right ear and 50dB in the left ear scored alomost perfectly by the list (rarely seen). A girl with mild loss on the list scored perfectly. The rest of the cases were dropouts or little information could be obtained due to deafness in the family. The conclusions are that even if a baby scores just a few points on the list, the family should be advised to get his/her hearing checked further. The difficulities in checking babies for hearing impairments, including high-frequency loss and mild to severe hearing loss, should be noted. From the point of view of identificaton of neonatal hearing loss, NHS should be preformed on all babies. NHS is better superior to the conventional system for evaluating hearing loss in infants.
We analyzed the results of newborn hearing screening and diagnostic testing following referral conducted at the Japanese Red Cross Society Wakayama Medical Center for about 7 years. In this Hospital, we conducted the hearing screening on 1653 newborn babies and 54 (3.2%) were judged to require closer examination. Fifty-one infants and 41 infants who failed the newborn hearing screening conducted at 8 obstetric clinics in Wakayama Prefecture (92 cases in total) visited the center for more detailed examination. Sixty-two of the 92 cases (67%) were confirmed to have normal hearing on re-examination by automated instruments and 11 cases (12%) were confirmed to have normal hearing by conventional ABR, while hearing loss was confirmed in the remaining 19 cases (21%) for which early intervention was possible. Among the 41 patients referred to us by obstetric clinics, as many as 17 cases (41%) were diagnosed to have hearing loss. This high percentage probably reflects the fact that the patients had undergone prior testing, such as the one-month-old health checkup, several times before coming to our hospital. There were few cases who were diagnosed to have hearing loss based on conventional ABR conducted 3 to 4 months after birth, but none of the cases diagnosed to have hearing loss were later found to have normal hearing. This indicates that conventionalABR is an effective and reliable method of hearing examination.
We investigated 64 infants referred to our clinic between 2000 to 2005 for further evaluation of hearing after newborn hearing screening. Thirty-two cases each had been screened by automated auditory brainstem response (AABR) and otoacoustic emission (OAE) studies. The results of examination combining conditioned orientation response audiometry (COR) and ABR revealed that 32 (50%) cases had hearing loss, including 20 (63%) cases who had been screened by AABR and 12 (38%) cases who had been screened by OAE. Bilateral hearing loss was detected in 9 (56%) of 16 infants referred for bilateral hearing loss. The false-positive rate was relatively small, therefore, the screening examinations appeared to have been adequately performed. Six of the 47 cases referred for unilateral hearing loss were diagnosed as having bilateral hearing loss. Progression of the hearing loss was confirmed in two cases, and a falsenegative result of screening was suspected in four cases. Strict follow-up of infants referred for unilateral hearing loss is needed, because they frequently progress to bilateral hearing loss. In our prefecture, since universal screening has not been introduced yet, referral of some infants from the obstetric clinic was delayed, resulting in delayed diagnosis. The designing of a universal screening system in the prefecture would be highly desirable.
We investigated 16 infants who had been referred between 2004 and 2006 to KKR Otemae Hospital for advanced hearing evaluation after newborn hearing screening. The average age of the infants at their first visit was 1.5 months. The first auditory brainstem response (ABR) test revealed normal hearing in 5 of the 16 infants. Since most of the cases had been screened using otoacoustic emission tests, the narrowness of the external ear canal or effusion in the tympanum might have been responsible for the false-positive results. Repeat ABR examination within 6 months showed improvement of the hearing threshold to the normal range in 6 of the remaining 11 cases. This improvement may be explained by the maturation of myelin in the auditory tract. Although newborn hearing screening results in the referral of a considerable number of infants who eventually show normal hearing, this system remains useful to identify children with hearing impairment before the age of 6 months, which is critically important for determining the need for hearing aids and special education. Since a substantial amount of time is required to evaluate infants, we suggest that more hospitals participate in advanced hearing examination for the early diagnosis of hearing impairment in new-born infants.
Fasudil, a potent Rho-kinase inhibitor, has been reported to reverse the endothelin-induced vasoconstriction of the spiral modiolar artery in the gerbil cochlea. We previously demonstrated that both endothelin receptors and endothelin-converting enzymes are expressed in the rat cochlea and that the serum endothelin levels in patients with sudden sensorineural hearing loss (SSHL) were significantly increased before steroid treatment. Since one subgroup of SSHL is believed to arise from vasoconstriction and vasospasm of the spiral modiolar artery ultimately causing ischemic stroke of the cochlea, we conducted a clinical investigation of fasudil (Rho-kinase inhibitor) combined with a steroid for the treatment of SSHL by preventing the inner ear ischemia induced by endothelin. Nine out of ten SSHL patients (90%) who received intravenous infusion of fasudil (9 days×30mg twice/day) showed complete or significant recovery in the level of hearing. The average hearing level was 72.7dB (n=10) before fasudil treatment, 44.9dB at the end of fasudil treatment (9 days after), and 31.9dB at the final evaluation. These results indicate that idiopathic SSHL could be caused by endothelin-induced vasoconstriction and vasospasm of the spiral modiolar artery of the cochlea, and that the fasudil administration combined with a steroid may be a novel potent treatment option for SSHL.
A number of reports have shown the presence of glucocorticoid receptor (GR) in the inner ear, and steroid drugs are commonly used for the treatment of sensorineural hearing loss. However, the site of steroid action in the cochlea is not yet well understood. Here, we examined the effect of a GR antagonist, mifepristone, on acoustic trauma in guinea pigs. The animals were exposed to 4kHz pure tone of 100 or 120dB SPL, followed by subcutaneous injection of mifepristone (20mg/kg). Seven days later, the compound action potentials (CAPs) of the cochlear nerve and distortion product otoacoustic emissions (DPOAEs) were recorded. Mifepristone significantly inhibited the recovery of the CAP threshold after exposure to 120dB SPL, but did not change the DPOAE output. It is suggested that mifepristone, and thus glucocorticoids, may influence the inner hair cells and connected nerve fibers without having any influence on the outer hair cells (OHCs). We next studied the changes in the DPOAEs in 9 patients with idiopathic sudden sensorineural hearing loss (ISSNHL) before and after steroid administration combined with hyperbaric oxygen therapy (HBO). The recovery of the DPOAEs did not differ significantly between patients with good hearing recovery and those with poor hearing recovery. This result implies that the main responsible for the therapeutic effects of steroid plus HBO in ISSNHL is unlikely to be the OHCs.
Three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) MRI has recently been used to evaluate the pathology of the inner ear in cases of sensorineural hearing loss (SNHL). It is also possible by this method to detect the breakdown of the blood-labyrinth barrier in the affected ears. In this study, nine of twelve patients with sudden SNHL showed high signals in the affected ear on precontrast 3D-FLAIR. Two of these patients also showed gadolinium enhancement on 3D-FLAIR in the affected inner ear. Furthermore, the patient with acute [as different from “sudden”?] SNHL also showed gadolinium enhancement in the affected inner ear. This finding suggests a breakdown of the blood-labyrinth barrier at the time of the MRI. Further study is required to clarify the relationship between the 3D-FLAIR findings and the hearing prognosis. It is expected that 3D-FLAIR MRI would be useful for elucidating the pathologic condition in cases of SNHL.