ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

A method for recording the electrically evoked whole-nerve action potential (EAP) at the time of cochlear implant surgery is described. Measures of EAP growth with stimulus level and functions describing the rate of recovery of the auditory nerve from the refractory state are reported for patients tested intraoperatively and for a group of patients using the Ineraid implant, from whom recordings were made following implantation. Subjects tested intraoperatively were separated into three categories: congeni-tally deaf children (n = 14), prelingual meningitic children (n = 5), and postlingual adults (n = 13). A fourth group consisted of postlingual adults (n = 14) tested postoperatively. Results from all groups showed a similar range of EAP growth and recovery rates across patients. Data from congenitally deaf children formed the exception showing steeper EAP growth functions than other subject groups. Electrically evoked whole-nerve action potential growth and recovery functions of the postoperative group of subjects showed modest correlations to speech perception scores measured after at least 18 months of implant use. The possible use of these measures in fitting an implant to an individual is discussed.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Conventional teaching regarding the acoustic function of the human middle ear is that it serves as an impedance matching system to offset the loss that occurs when sound passes from the low-impedance sound field to the high-impedance cochlear fluid. A transformer analogy is often used with the pressure transformation produced by the eardrum; footplate area ratio and the lever ratio considered to be approximately 27 dB. Recent data on middle ear function has shown this to be only partially correct. A transformer analogy is not appropriate since the pressure gain of the middle ear decreases above 1000 Hz and does not depend on the cochlear load at all frequencies. Experiments are described of umbo, malleus short process, and stapes displacement in human temporal bones using a laser Doppler measuring system (LDS). The measurements support previous studies that indicate that in addition to a roll-off in tympanic membrane function above 1000 Hz, there is slippage in the ossicular lever system that causes an increasing “lever ratio” above 1000 Hz, thought to be caused by translational movement of the ossicular rotation axis near the short process. An improved analog circuit model of the external and middle ear has been developed that produces results equivalent to those found in the temporal bones.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Members of the American Otological Society and the American Neurotology Society were polled regarding stapes surgery and reparative granuloma. Of 467 questionnaires, 176 (38%) were returned, and 319,410 stapes cases were statistically analyzed: 329 reparative granulomas were reported after stapedectomy (incidence = 0.1%) and 29 after stapedotomy (incidence = 0.07%); 77 surgeons reported having encountered at least one reparative granuloma; and 50 surgeons related the occurrence of a reparative granuloma to a specific graft material. Gelfoam was the most common graft material reported when a reparative granuloma was encountered, followed by fat, and vertigo was the most frequently reported presenting symptom. Reported operative techniques as well as manifestations, management, and outcome are discussed.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Direct facial nerve stimulation and monitoring during cerebellopontine angle (CPA) tumor surgery are critical for identification and preservation of function. Electrically evoked facial nerve monitoring was compared with ulnar train-of-four monitoring under progressive neuromuscular blockade. Using a rabbit model, the facial nerve function of six controls was compared to that of six specimens with acute or chronic injuries. Eight of 18 patients who had undergone CPA tumor resection during one year were also studied. Regression analysis correlated between ulnar nerve monitoring and facial electromyographic (EMG) peak voltage in all groups. Facial EMG was measurable, even with 75 percent receptor blockade. The results of this study support the hypothesis that high degrees of neuromuscular blockade do not preclude satisfactory EMG monitoring of the facial nerve during CPA tumor surgery. This study did demonstrate that chronically injured facial nerves may show greater sensitivity to the effects of neuromuscular blockade. Lower levels or avoidance of neuromuscular blockade should be employed under these circumstances.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Since the early 1980s rigid endoscopes have been used by otorhinolaryngologists in the United States primarily for sinus surgery. Recently rigid endoscopes have been used as an adjunct to standard otologic and neurotologic procedures. Diagnostic inspection of the middle ear can be performed through a myringotomy incision to rule out perilymphatic fistula, for identification of cholesteatoma, or for evaluation of the status of the ossicular chain. During chronic ear surgery endoscopes can be used to locate hidden cholesteatoma in difficult to visualize areas such as the eustachian tube, attic, sinus tympani, and beneath an intact posterior canal wall. In acoustic neuroma surgery in which hearing preservation is an objective endoscopes are used to inspect the lateral aspect of the internal auditory canal (IAC) for residual tumor. During vestibular neurectomy endoscopes are used to view the IAC and to help identify the cochleovestibular cleavage plane. The applications, techniques, and limitations of rigid endoscopy in otology and neurotology are discussed.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Recent reports have suggested that particulate matter identified within the membranous portion of the posterior semicircular canal is responsible for the development of positional vertigo. To further investigate this claim, a posterior canal fenestration was carried out in ten patients undergoing acoustic tumor removal via a translabyrinthine approach. Particles were identified in the membranous labyrinth in nine patients. One of these patients described positional vertigo preoperatively. Electron microscopy demonstrated particles within the membranous labyrinth that appeared to be of mixed proteinaceous and mineral content. These data suggest that further studies must be undertaken before the theory of endolymphatic particle migration can be confirmed as the etiology of positional vertigo.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Stapes surgery for fixed footplate associated with X-linked congenital mixed hearing loss usually results in a “gusher” and severe worsening of hearing. Four patients with X-l inked deafness were diagnosed by the characteristic temporal bone computed tomography (CT) findings of enlarged internal auditory canal, hypoplasia of the cochlear base, absent bony modiolus, abnormal vestibular aqueduct, and enlarged labyrinthine facial nerve canal. Three patients were scanned after stapes surgery resulted in a gusher and, in two patients, severe worsening of their hearing loss. Stapes fenestration in the other patient was avoided by CT recognition of the dysplasia. The authors believe that young males presenting with congenital mixed hearing loss should be studied with temporal bone CT prior to middle ear exploration.

ISSN:0192-9763    

出版商:OVID    

年代:1994

数据来源: OVID