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At least 145 records · Page 8Linked to original sources
PubMed1992

Experimental basis for lidocaine therapy in cochlear disorders.

In order to further our basic understanding of the effects of lidocaine hydrochloride in the inner ear, cochlear potentials and blood flow (CBF) were assessed after intravenous (i.v.), anterior inferior cerebellar artery (AICA), and local round window (RW) lidocaine administrations in guinea pigs and rats. Lidocaine RW applications produced a dose dependent decrease in compound action potentials (CAP) and cochlear microphonics (CM). The sensitivity changes were more pronounced at high frequencies. These findings suggest that lidocaine has specific pharmacological action in the inner ear other than simple anesthesia of the auditory nerve. The basal turn endocochlear potentials (EP) were not altered by topical lidocaine, implicating altered organ of Corti function following local application of lidocaine. RW applications of lidocaine had no effect on CBF or systemic blood pressure (BP). I.v. infusions caused substantial reductions in BP. In the case of systemic infusions the percent changes in CBF were equal to and accountable by the BP changes. The microinfusions (50 mg/ml, 100 nl/min) through AICA produced a 30%, long lasting increase in CBF. However, neither systemic lidocaine nor AICA infusions had an effect on CAP or CM. These findings indicate that systemically given lidocaine may not cross the blood-cochlear barrier and that the cochlear electrophysiological effects due to lidocaine when given locally are partly mediated by direct influence on cochlear hair cell function; they also suggest that lidocaine-induced interference with active ion transport in the lateral wall or an influence on CBF are not contributing factors.

Action Potentials↗
PubMed1990

Perilymphatic fistula in the guinea pig.

Clinical reports on perilymphatic fistulae (PLF) of the round window membrane (RWM) have shown different degrees of hearing loss. However, the hearing can also be entirely unaffected. Experimentally induced PLF of the RWM in animals showed results similar to those of the clinical reports, although some researchers have concluded that perforation of the RWM per se does not necessarily induce significant hearing loss. The purpose of the present study was to clarify if, and how, PLF of RWM in the guinea pig actually affects the auditory action potentials. During 1 h of observation following perforation of the RWM, the immediate and continuous effect of the PLF was evaluated. In more than 50% of the animals, different amounts of threshold shift were obtained. In another group of guinea pigs an attempt was made to clarify the findings by reducing the cerebrospinal fluid pressure before perforating the RWM.

Animals↗
PubMed1978

Auditory brain stem responses in patients with acoustic neuromas.

In the continuing search for methods to diagnose acoustic neuromas at an early stage, we have applied the auditory brain stem response examination to 27 patients with surgically verified acoustic neuromas. It is confirmed that the main indicator of retrocochlear versus cochlear disease is the interaural latency difference of the Jewett5 wave, the IT5. Women exhibit significantly lower latency values to J5 than men, approximately 0.25 msec. Age also has some influence, so that the J5 latency tends to increase with age, but in this investigation the trend did not reach statistical significance. We were unable to find a correlation between tumour size and IT5. Even if the audiogram shows a considerable hearing impairment at 2 kHz this technique can be used without any correction factors, when the stimulus is a 2 kHz filtered tone-pip. In the presence of an acoustic neuroma there will often be adaptation of the response and it is preferable to arrange the mode of stimulus presentation so that this phenomenon eventually becomes prominent. One patient came out with a false-negative result. We believe this to have been due to our lack of experience at that time and that today we would have recognized the presence of a tumour. If this correction is accepted, the series contains no false-negatives. Regardless of this it can be concluded that for the time being, out of the functional audiological tests, the auditory brain stem response examination is the most reliable indicator for the presence of retrocochlear lesions.

Adolescent↗
PubMed1993

The bionic ear and the mythology of paediatric implants.

Parents face a daunting task when deciding whether an implant is an optimal, or even a viable choice for their deaf child. Much of the confusion is as a result of vested interest by both proponents and critics of cochlear implantation.

Bionics↗
PubMed1990

[Narrow-band action potentials of the guinea-pig cochlea as compared with the ordinary electrocochleograms under normal and pathological conditions].

The narrow-band action potentials (NAP) and the ordinary electrocochleograms were recorded from the guinea-pig cochlea under normal and pathological conditions in order to study whether the NAP could be a useful measure to detect cochlear dysfunctions. The cochlea damaged either by the administration of kanamycin or by a mechanical lesion of the round window served as pathological materials. Recordings showed that the threshold and amplitude measured for the N1 potential of NAPs ran in parallel with those of the cochlear microphonic potentials (CM), under both normal and pathological conditions of the cochlea. This implies that the CM could be replaced by the NAP when difficulties were present in recording CMs. It may be inferred that the NAP reflects responses of the inner hair-cells and cochlear nerves, while the CM would mainly be derived from responses of the outer hair-cells to the frequency-specific movements of the basilar membrane. If so, the NAP should offer a good means for the objective audiometry. Recording NAPs is also superior to the ordinary electrocochleography in that the method makes it possible to obtain responses generated near the apex of the cochlea, i.e., responses to low-pitch sound stimuli.

Action Potentials↗
PubMed1993

[Acute sensory deafness originating from experimental double-membrane rupture].

Combined rupture of Reissner's membrane and the round window membrane (double-membrane rupture) as a cause of acute profound sensorineural hearing loss was investigated in guinea pigs. Action potentials (APs) of the cochlear nerve in response to tone pip stimuli (1, 2, 4, 8kHz) were recorded before and after rupture of Reissner's membrane at each turn of the cochlea. Then the round window was perforated to create leakage of the perilymph. Ninety minutes later, AP was again recorded. After these procedures, the animal was sacrificed for histological study to confirm the rupture of Reissner's membrane. The ears with double-membrane rupture showed a larger decrease in AP amplitude at all test frequencies than did control ears with round window rupture alone. The ears in which Reissner's membrane was ruptured at the second turn showed more a pronounced decrease in AP amplitude than those ruptured at the third and apical turns. It was concluded that double-membrane rupture could be a cause of sudden deafness, but that the disturbance of cochlear function depends on where Reissner's membrane ruptures.

Action Potentials↗
PubMedDate not supplied

[Susac syndrome: clinical and diagnostic approach. A new case report].

INTRODUCTION: The Susac syndrome is made up of the clinical triad: encephalopathy, visual and hearing defects. It is caused by microangiopathy of unknown origin affecting the small arteries of the brain, retina and cochlea. It is very uncommon. It mainly affects young women. The course of the illness is usually monophasic and self-limiting. The deficit of visual acuity is caused by occlusion of tributaries of the retinal artery. The auditory defect is bilateral and symmetrical, and particularly affects medium and low frequencies. NMR is of great diagnostic value, showing multiple lesions in the grey and white matter. Our case gives more data regarding the evolution of this condition and the contribution of cerebral SPECT to diagnosis, the results of systemic treatment, use of hyperbaric oxygen and reflections on the physiopathology of the process. CLINICAL CASE: We present the clinical case of a young woman who presented with psychiatric symptoms and migraine followed by clinical encephalopathy and acute/subacute coma. There were also visual and auditory deficits. Other types of systemic disease were ruled out. CONCLUSIONS: Findings on SPECT suggested the presence of a microangiopathic disorder of the brain. The patient responded to systemic treatment with cortico-steroids. The encephalopathy resolved in a few days and two months later she had resumed her former daily activities. Treatment with hyperbaric oxygen definitely reduced visual sequelae.

Adult↗
PubMed2002

[Multi-channel cochlear implant in cochlear ossification].

Cochlear ossification, considered until only a few years ago as a contraindication for cochlear implants (C.I.), may now be managed by means of a wide variety of surgical techniques. In cases with massive ossification, the drill-out circummodiolar technique described by Gantz et al. in 1988 and successively modified by Balkany et al. in 1997 may be adopted. The technique of electrode insertion in the scala vestibuli, perfected by Steenerson et al. in 1990, may be used when cochlear ossification has spread no further than the scala tympani. Other methods call for a groove to be drilled along the proximal tip of the basal turn of the cochlea (Cohen and Waltzman, 1993), the insertion of electrodes through the middle cranial fossa (Colletti et al., 2000), or the utilization of a double electrode array (Bredberg et al., 1997, Lenarz et al., 2001). This study reports the experience conducted at the Cochlear Implants Centre of the Otorhinolaryngoiatrics, Otological and Otoneurological Microsurgery Section of the University of Parma in a group of 15 patients who underwent C.I. in the presence of varying degrees of ossification. In 3 cases the ossification was limited to the region of the round window and a few millimetres of the scala tympani; cochleostomy was performed anteriorly and inferiorly to the anterior niche of the round window. In 11 cases (of which 3 of pediatric age), the ossification had spread to the horizontal portion of the scala tympani; in these cases, the electrodes were inserted in the scala vestibuli. The scala vestibuli was opened by drilling anteriorly to the round window and superiorly to the spiral ligament. In the only case of massively ossified cochlea, it was possible to partially insert the electrodes in a circum-modiolar tunnel. In the 12-month follow-up hearing test, the 3 patients with ossification of the round window region and the first millimetres of the scala tympani respectively averaged 61.6% in recognizing 2-syllable words and 59% in recognizing words embedded in phrases. The averages on the 12-month follow-up hearing test in the 8 adult patients who received the implant in the scala vestibuli were 80.6% in recognizing 2-syllable words and 89.1% in recognizing words in phrases. The 3 pediatric patients were classified on the Geers and Moog scale, which situated 2 of them in the 6th category of perception and 1 of them in the 4th category of perception. As regards the only case of massive cochlear ossification, the patient underwent surgery recently, and the sole follow-up available is the one conducted after only 3 months; the vowel identification average was 55%; the average on the VCV test was 31%; and the 2-syllable word recognition average was 20%.

Acoustic Stimulation↗
PubMedDate not supplied

[Evaluation of hearing performance in cochlear implant patients].

OBJECTIVES: To determine the speech perception levels of cochlear implant patients and to evaluate the possible effects of implant type, duration of deafness, and bacterial meningitis on the patients' hearing performance. PATIENTS AND METHODS: A three-section test battery on speech perception was administered to 21 cochlear implant patients (12 males, 9 females; mean age 25 years; range 9 to 40 years). The patients' performance was assessed with respect to single- or multi-channel implant design, duration of hearing loss, and etiologic factors of hearing loss. RESULTS: The overall mean success score was 74.6 (range 49-100). No significant difference was found between patients using single- or multi-channel implants. The mean score of 12 patients whose duration of hearing loss was below the average (8.2 years) was significantly higher than those of nine patients with a longer history of hearing loss (85.7 versus 59.6, p=0.001). Patients with meningitis-associated hearing loss exhibited a significantly lower performance than those presenting with other etiologic factors (61.9 versus 84.1, p=0.001). CONCLUSION: Early diagnosis and rehabilitation are essential to achieve better performance following cochlear implantation.

Adolescent↗
PubMed2003

[A comparison between findings of high resolution computed tomography and magnetic resonance imaging in the preoperative assessment of cochlear implant patients].

OBJECTIVES: We compared the preoperative findings of high resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) with those observed during surgery to determine their value for cochlear implant patients. PATIENTS AND METHODS: A retrospective assessment was made on preoperative HRCT and MRI scans of 124 cochlear implant patients (71 males, 53 females; mean age 15 years; range 2 to 63 years). Congenital cochlear anomalies, cochlear ossification, new bone formation in the middle ear, and structures in the internal auditory canal were evaluated and compared with intraoperative findings. RESULTS: Cochlear anomalies detected in five patients by HRCT and MRI were confirmed intraoperatively. Cochlear ossification encountered in six patients during surgery was only demonstrated in four patients; HRCT and MRI scans only showed a narrow basal turn in the remaining two patients. During surgery, eight patients were found to have cochlear fibrosis: this finding was documented in five patients (62.5%) by MRI, and in none by HRCT scans. CONCLUSION: Although HRCT provides valuable information for surgical planning, its limitations may justify the additional use of MRI before cochlear implantation.

Adolescent↗
PubMed2003

[A new case of Susac syndrome and a review of the literature].

We report a single case of Susac syndrome (microangiopathy of the brain, retina, and cochlea). A 26-year-old woman developed branch retinal artery occlusion in the right eye, associated with bilateral hearing loss that mostly involved low frequencies. MRI of the brain revealed small multifocal hyperintensities in the white matter of the cerebrum on T2-weighted images with gadolium enhancement. The treatment consisted of anticoagulation and antiplatelet drugs. Seventy-one cases of Susac syndrome have been reported in the literature. The Susac syndrome is more frequent in females and its etiology remains unknown. However, immune inflammatory disorders, vasospastic phenomena, and coagulopathy could be involved in its pathophysiology. Treatment options are not standardized, ranging from antithrombotic drugs to immunomodulatory therapy. The course of the disease is self-limited after an initial fluctuating active phase. The prognosis of Susac syndrome is good in most cases.

Adult↗
PubMed2002

[Radiological study of temporal bone in children with profound deafness before cochlear implant: CT vs magnetic resonance imaging].

OBJECTIVE: To evaluate the clinical application of magnetic resonance imaging (MRI) and CT in children with profound deafness before cochlear implant and their impact on surgical decision. METHODS: The pre-operative CT and MRI data from 71 children with bilateral profound deafness planned for cochlear implant were studied. RESULTS: 12 patients showed enlarged vestibular aqueduct (16.9%); 14 patients had Mondini malformation (19.7%); 3 patients demonstrated enlarged internal auditory meatus (4.2%); and 2 patients were suspected to have fistulae (2.8%) on both CT and MRI examinations. In comparison between MRI and CT, unilateral cochlear fibrosis was detected in 5 patients(7%) by MRI, but none by CT scans. Bilateral dehiscent facial nerve was detected in 1 patient(1.4%) by CT scan, while MRI was normal. CONCLUSION: CT and MRI are essential for the pre-operative planning of cochlear implant, especially in patients with enlarged vestibular aqueduct, Mondini malformation, enlarged internal auditory meatus and suspected fistulae. These two imaging modalities are complementary to each other in cases with cochlear fibrosis and facial nerve dehiscence.

Child↗
PubMed1992

[Inner ear damage due to hyperlipidemia in the young and old guinea pigs].

Nineteen guinea pigs of one month and 11 of 30 months were given high fat diet for 3 months to produce hyperlipidemia; 16 of them followed by 3 months' normal diet to resume blood lipid level; 27 for control. The results showed that: The serum cholesterol level of the experimental groups was markedly elevated (P < 0.01) with fatty degeneration of liver. Damages in OHC, IHC, cells of stria vascularis and few myelin sheaths of cochlear nerve were seen in all experimental animals, and the reduction of cochlear damages was not seen in those animals with blood lipid level resumed to normal. Auditory dysfunction was very marked as shown by ABR in the old animals with hyperlipidemia as compared with controls (P < 0.01).

Animals↗
PubMed1992

Electrocochleographic recordings in chronic and healed perilymphatic fistula.

This study examined electrocochleographic recordings in 15 guinea pigs with perilymphatic fistulas. A chronic round window fistula was induced in each animal by insertion of a sigmoid stainless steel needle with the lumen intact. In the contralateral control ear, a similar needle was inserted with the lumen crushed. In this way the model compared acute (control group) versus chronic (experimental group) perilymphatic fisulae. Electrocochleographic recordings were obtained before, immediately after needle insertion, in a subset at two to three weeks after needle insertion, and again at 17-22 weeks when the fistulas had healed with the needles still in place. Minimal threshold changes were noted from the pre- to the acute post-condition. More marked elevation of threshold was noted for the 17-22 weeks condition. Threshold elevation was greater in the experimental ears but was present in the control ears. The SP/AP amplitude ratio was generally stable for the pre- to post-conditions in both ears. For the 17-22 week epoch the SP/AP amplitude ratio was still fairly stable for the click stimulus but the ratio diminished for the toneburst stimuli. For the subset analyzed at 7-21 days the SP/AP amplitude ratio tended to increase for both groups for all stimuli although AP thresholds were normal.

Animals↗
PubMed1992

Evaluations of 3M/House single-channel and nucleus multichannel cochlear implants.

3M/House single-channel (n = 158) and Nucleus multichannel (n = 71) adult cochlear implant users were surveyed about their devices. In comparison to the 3M/House users, the Nucleus users reported better speech and environmental sounds perception and more hours of daily use. However, Nucleus users also were more likely to report that the expense of upkeep and frequent movement of external parts of their implants were problems. On average, users in both groups were satisfied and felt that their implants had positively affected their lifestyle, enjoyment of social events, and employability. Differences between groups regarding these variables were not found. Multiple regression indicated that the users' ratings of the effects of their implants on speech perception, environmental sounds perception, enjoyment of social events, and lifestyle were all statistically significant predictors of satisfaction. It was concluded that the majority of the users in either group thought their devices provided real-world benefits.

Adult↗