Twenty-eight children with steep high tone sensorineural hearing loss were analyzed. Those clinical findings were described as follows; 1) The number of patients according to the first frequency of their steep sloping was one in 0.5kHz, 7 in 1kHz, 15 in 2kHz, 3 in 4kHz and 2 in 8kHz. 2) Most of them were diagnosed at 7 years old after regular screening hearing test at their elementary school. Most of their parents had no doubt of their hearing loss. 3) Speech discrimination score (SDS) anylized in 2kHz steep frequency were distributed from 50% to 95%. 4) Articulation errors were appeared mostly in confusion of fricatives and unvoiced affricates. 5) 8 cases had the possibility of familial deafness, and the other 9 cases had asphyxia episode at their birth. These factors should be cared as a high risk of steep high tone hearing loss.
The effect of the middle ear reflex (MER) on cochlear microphonics (CM) and middle ear impedance has been reported. However, its effect on ossicular vibrations has not been clarified. In this study, using Laser Doppler Velocimeter (LDV), ossicular vibrations of guinea pigs and rabbits were measured directly when contralateral stimuli were presented to induce the MER. The measured results revealed that the amplitude of ossicular vibrations decreased with an increase in the stimulus intensity, and that the attenuation of ossicular vibrations at low frequencies was larger than at high frequencies. Also, from these results, the mode change of the ossicular vibrations before and after stimulation was speculated.
Although it has been postulated that kendo causes sensorineural hearing loss (SNHL), no such clinical cases demonstrating distinct relationship between kendo and SNHL have been reported. We reported a 17-year-old male student who developed acute SNHL (45-70dB HL at 1-8kHz) in his left ear following Kendo exercise. His hearing was almost recovery by the 11th day from the onset, indicating a similar process to temporary threshold shift (TTS) with a delayed recovery. In order to confirm whether or not a hitting sound and/or shock by “shinai”, a bamboo sword, during Kendo excercise induces TTS, 17 volunteer medical students in the Kendo team in Miyazaki Medical College were subject to pure tone audiometry before and after the “Men-Uchi” exercise. Two subjects who showed high-frequency-dips before the exercise were found to cause TTS following the exercise. The result of this preliminary study may indicate that the assessment of TTS caused by Kendo excercise is potentially useful for estimating susceptibility to “Kendo-induced SNHL” in young Kendo players.
To investigate the mechanism of delayed endolymphatic hydrops (DEH), 404 patients with unilateral profound sensorineural hearing loss were analyzed. The cause of profound hearing loss, hearing level in the contralateral ear, time lapsed from the onset of hearing loss in the first ear to the opposite ear were retrospectively evaluated. Hearing loss in the contralateral ear with 30dB or more in at least one audiometric frequency was seen in 60% of the 404 patients, and 79 (20%) of them showed 60dB or more of average hearing level. It was found that 50 of the 404 were diagnosed as DEH and 26 (6%) of them were contralateral type. While 48, 065 patients visited our clinic due to all otorhinolaryngological diseases during the same period, and only 275 (0.6%) out of all the patients were diagnosed as Meniere's disease. The results suggested that contralateral-type DEH is not Meniere's disease unexpectedly occurred in the opposite ear with profound hearing loss but the first affected ear might play a role to cause contralateral hearing loss. It is indicated that patients with unilateral profound hearing loss might have a great risk of hearing disability in the opposite ear.
Superficial siderosis of the central nervous system (SSCN) characterized by sensorineural hearing loss, ataxia, and pyramidal tract signs is a rare. The symptoms are caused by intracellular and extracellular hemosiderin deposition in the leptomeninges, subpial tissue, spinal cord, and cranial nerves as a result of chronic bleeding in the subarachnoid space, In the previous reports, the diagnosis of SSCN was often made at autopsy or during a neurosurgical procedure. Recently, MRI makes the non-invasive diagnosis of SSCN possible. A 43-year-old male with SSCN presented with the chief complaint of bilateral hearing loss and gait disturbance. The diagnosis of SSCN was made by T-2 weighted images on MRI of the central nervous system showing diffuse marginal hypointensity of the cerebrum, brain stem and cerebellum. Bleeding source into the subarachnoid space could not be detected on the detailed examinations, and the hearing loss was rapidly progressed to total deafness in both ears. SSCN should be considered in the differential diagnosis of unexplainable progressive sensorineural hearing loss. MRI is useful as noninvasive method for accurate diagnosis of SSCN.
Several factors in 6 cases with moderate or severe hearing impairment after their first three or more years of life were examined. At the same time questionnaires completed by 252 parents of hearing-impaired children were analyzed. In two third of these children, parents first suspected their children to have hearing difficulties within their first one and a half years. Unfortunately, proper diagnosis was considerably delayed in spite of parents' suspicion, due to a lack of sufficient awareness of childhood deafness. Informations regarding children's hearing dysfunction and consequent language retardation must be distributed among medical practitioners, community health nurses and parents. There was a considerable difference in the language development of children whose hearing impairment ranged from moderate to severe, Theoretically, severe hearing disorders should be detected much earlier. On the other hand, the auditory screening system for three-year-old children was quite effective in detecting the moderate hearing impairment.
A 21-year-old female complained of headache and vomiting as the first neurologic symptom at 17 years of age. Mitochondrial encephalopaty, lactic acidosis and stroke-like episodes (MELAS) was diagnosed by clinical findings and muscle biopsy revealing ragged red fibers. Next year, bilateral sensorineural hearing loss was found. After a strokelike episode at age 20, she noticed the difficulty with recognition of speech and environmental sounds, but hearing level (50dBnHL) on pure tone audiometry (PTA) was not changed. These psychoacoustic deficits revealed auditory agnosia due to cortical lesions. The thresthold in ABR was consistent with that in PTA and prolongation of I-V wave was not found. EOAE response was not detected at level of 78.5dB. Brain MRI and CT showed cerebral cortical atrophy in the temporal, parietal and occipital lobes and ventricular dilatation. PET images of cerebral glucose metabolism and blood flow indicated that the areas of activity were rightlateralized in the temporal gyrus and the posterior inferior frontal region (Broca area). We concluded that hearing disturbance in this case might be caused by decrease of cochlear function and cortical auditory damage.
The tonotopic organization of the human auditory cortex has been investigated using the auditory evoked potentials. 21-ch auditory evoked potentials from 5 normal adults were collected after monaural tone burst stimuli of 500, 1000, 2000, and 4000Hz were given. Increasing stimulus frequency resulted in a decrease in N1 amplitude and an associated decrease in N1 latency. The equivalent dipoles for N1 were estimated using the dipole tracing method. The dipoles located in the contralateral temporal lobes or near the thalamus. The dipoles of the contralateral temporal lobes located deeper in the lateral portion with increasing frequencies. Our results were similar to the findings of previous investigators who support the tonotopic organization.