Hiroaki Nishida

Comparison of acute low-tone sensorineural hearing loss versus meniere's disease by electrocochleography

To clarify the pathogenesis of acute low-tone sensorineural hearing loss (ALHL), we retrospectively compared the electrocochleographic findings from 20 patients with ALHL with those from 58 patients with Menieres disease (MD) classified into 4 groups (MD1 through MD4) according to their pure tone average. The mean summating potential-action potential ratio in the ALHL group was 0.35 ± 0.13, which was significantly higher than the control ratio but similar to the ratio seen in the MD1 group (pure tone average < 25 dB hearing level). The mean detection threshold of the cochlear microphonics in the ALHL group was 32.0 ± 9.4 dB normal hearing level, which was again similar to that seen in the MD1 group. Moreover, more than 50% of patients with ALHL had normal cochlear microphonics input-output curves. We therefore conclude that the pathogenesis of ALHL arises from an endolymphatic hydrops with little or no impairment of hair cells that resembles early-stage MD.

Changes of the action potential, the summating potential and cochlear microphonics in experimental endolymphatic hydrops.

The changes of the action potential (AP), the summating potential (SP) and cochlear microphonics (CM) were investigated in reference to the grade of endolymphatic hydrops produced by endolymphatic sac obliteration in guinea pigs. In a few cases with minimum endolymphatic hydrops, super-normal AP was obtained. With an increase of endolymphatic hydrops, CM responses were reduced although AP responses at intensive stimulation were maintained relatively well. It is thought that the polarity of positive SP, as observed in control, was influenced to deflect towards negative SP by an interaction between the increased degree of endolymphatic hydrops and the changes of the biochemical components of the inner ear fluids.

Experimental Labyrinthine Lesions through Stylomastoid Foramen

It was confirmed that the substances injected into the facial nerve through the stylomastoid foramen, reached every part of the inner ear. In sensitized animals, by repeated provocative injections of antigen, acute reversible episodes, very similar to that of Ménières disease, were observed. The injection of various solutions and the provocative injection into the sensitized animals, resulted in completely opposite reactions. In sensitized animals, the electrophysiological phenomena of the cochlea also showed fluctuations like Ménières disease.

Evoked Otoacoustic Emissions and Electrocochleography in a Patient with Multiple Sclerosis

A 24-year-old woman with multiple sclerosis had right-sided hearing impairment with tinnitus. She underwent electrocochleography (ECochG) and examination of evoked otoacoustic emissions (EOAEs) to assess cochlear function. An acoustic probe to measure EOAEs was inserted into the external ear canal. The ECochG action potential and cochlear microphonics were recorded by a transtympanic needle electrode technique. Both fast and slow components of EOAEs appeared in either the period of deteriorated hearing acuity or when it was improved. They showed normal detection thresholds and input-output curves during both periods. Cochlear microphonics with almost normal detection thresholds and input-output functions were obtained during the period of deteriorated hearing acuity. Action potential (N1) input-output curves during relapse with hearing loss were notably lower in amplitude and longer in latency than those obtained at the time hearing impairment showed improvement. The EOAE and ECochG findings suggested that this patient had almost normal cochlear function, and we assumed from the magnetic resonance imaging and auditory brain stem response findings as well as the ECochG that the hearing impairment was caused by dysfunction of auditory pathways in the brain stem, including structures that contribute to generation of the N1 potential of the ECochG.

Electrocochleographic study of sudden deafness.

By performing electrocochleography (AP, SP and CM) on 34 patients with sudden deafness, it was thought that the pathophysiology of this disease could be deduced. The various waveform patterns of AP and SP responses obtained in cases of sudden deafness were classified into the following types: 1) AP high response; 2) decreased AP high response; 3) AP low response; 4) dominant — SP; 5) — SP or + SP; and 6) AP, SP no response. The cases showing the type of dominant — SP and AP high response had satisfactory prognoses. In these cases the sensory epithelium and the cochlear nerve seemed to indicate a reversible condition being affected by the temporary functional block. Furthermore, it seemed to indicate that the neural regions related to the source of AP(N1) response were impaired in cases in which CM were recorded at normal response threshold in spite of the absence of AP(N1) response. In the unsatisfactory prognosis cases with decreased AP high response, AP low response and AP, SP no response in which only the extremely low or depressed CM responses could be recorded, it seemed that the sensory epithelium and the cochlear nerve were affected permanently, although the degree of impairment varied.

Diagnostic Significance of Summating Potential in Sensorineural Deafness

The polarity of the summating potential wave induced by electrocochleographical examination has an important bearing upon the pathophysiology or the prognostic evaluation of sensorineural deafness. Electrocochleographical examination was performed on cases of sudden deafness, Ménières disease, progressive sensorineural deafness, sensorineural deafness due to barotrauma, etc. When the polarity of the summating potential showed an increased negative wave, physiological blockage in sensorineural structures was revealed. In other words, under such conditions sensorineural structures have a potential for activity although hearing acuity was damaged. On the other hand, when the summating potential has an increased positive polarity wave, gradual decrease of the hearing acuity was revealed.

Regional Difference in Susceptibility to Damage of Vestibulo-Semicircular Canals in Experimental Labyrinthine Lesion

In the study on regional difference in susceptibility to damage of vestibulo-semicircular canals upon causing labyrinthine lesion by four different procedures, namely, by intracranial approach, through the middle ear, through the facial nerve and by means of experimental endolymphatic hydrops, the following results were obtained. 1. The crista of posterior semicircular canal among the semicircular canals and the macula of the saccule within the vestibule were most susceptible to impairment. In other words, the most susceptible region was the so-called pars inferior. In regard to the impairment of the cupulas, the posterior semicircular canal was the most susceptible region. 2. Recovery from markedly reduced caloric nystagmus within a short period so as to see provocation of caloric nystagmus may result from the reconstruction of the cupulas and the normalization of vacuole-like findings of the sensory epithelium.

Right Vertebral Artery Aneurysm Manifesting as Sensorineural Hearing Loss.

A 79-year-old woman complained of right hearing loss, tinnitus and dizziness. CT, MRI and angiography demonstrated a large aneurysm of the right vertebral artery. On the pure-tone audiogram, there was a remarkable difference between the right and left ears. On the left side hearing was almost normal for her age, although on the right side hearing at the frequency above the 1kHz was severely affected. Electrocochleography was performed using the extratympanic approach. The detection thresholds of both cochlear microphonics and action potential were lower than the audiometric threshold. In spite of the difference in the audiometric threshold between the right and the left ears, the DP audiograms were similar. The auditory brainstem response was normal in the left ear, but only wave I was demonstrated in the right ear. It is thought that these neurotological examinations showed retrocochlear hearing loss.

Experimental labyrinthine disorders and direction of nystagmus.

The purpose of this paper is to demonstrate the variation of the direction of nystagmus which is elicited from the peripheral labyrinth. The direction of nystagmus depends, among other things, on the nature of the stimulus. Depending on the degree of pathophysiological conditions in the labyrinth, atypical nystagmus which does not comply with the rule is occasionally elicited even though the same stimulus is given. Hyperfunctional stimulation to the labyrinth, such as allergy, causes nystagmus which beats to the affected side and also shows hyperactivity of the whole nerve action potential and cochlear microphonics.

The Role of Cerebrospinal Fluid in Cases of Sudden Deafness

Cerebrospinal fluid was examined in 20 patients experiencing sudden deafness. Pressure, protein, glucose and cell counts were measured, virus culture was done, and IgG, IgA, IgM in concentrated cerebrospinal fluid were measured by means of the single radial immunodiffusion method and IgE also by means of the radio-immunosorbent test. Pressures ranged from 110 mm H2O to 330 mm H2O and the mean being 178 mm H2O. Protein and glucose were almost normal, IgG and IgE were normal. In five cases, IgM were demonstrated. IgA ranged from 0.08 mg/dl to 1.7 mg/dl. In two cases, the viruses were cultured and were determined to be Herpes according to morphological features. In the group showing complete recovery and/or improvement, the initial pressure and glucose value were rather low; in the group showing no change, the value of IgA was low. In the two cases where virus was isolated, there was no alteration of pure tone audiometry nor was there any improvement of hearing acuity. The virus isolated from the two cases presented was of low virulence since the number of cells in the CSF was small and the virus grew poorly even after serial cultivation. Accordingly, virus such as these may act one of the causative agents in sudden deafness.