PubMed Health⌕ Search

Biomedical subjects

M Z Cashman

Publications and source records attributed to M Z Cashman.

10 recordsLinked to original sources
PubMed2000

Electrocochleography and gentamicin therapy for Ménière's disease: a preliminary report.

OBJECTIVE: It is widely held that an enlarged summating potential (SP) relative to the eighth nerve action potential (AP) is a reflection of endolymphatic hydrops. Aminoglycosides are an accepted treatment for incapacitating Ménière's disease and are known to affect both sensory and secretory cells of the inner ear. The intent of this study was to determine whether this effect on secretory cells could be objectively confirmed by virtue of changes in the electrocochleogram (ECoG) of patients receiving gentamicin therapy for Ménière's disease. STUDY DESIGN: This was a prospective longitudinal study of repeated ECoG measures in three groups of subjects. Ménière's patients undergoing gentamicin treatment were compared with two control groups: individuals with stable Ménière's disease and normal-hearing control subjects. SETTING: The study was conducted at a tertiary referral center. PATIENTS: The sample included 21 normal-hearing subjects, 15 patients with stable unilateral Ménière's disease, and 12 with disabling unilateral Ménière's disease. INTERVENTIONS: For patients with disabling Ménière's disease, gentamicin was administered transtympanically. Audiograms, impedance tests, and ECoG were performed twice for all subjects. MAIN OUTCOME MEASURES: The SP and AP amplitudes, AP latency, and SP/AP ratio of the EcoG were measured. RESULTS: A statistically significant reduction in the SP/AP ratio was observed after gentamicin administration (analysis of variance interaction effect: F2 = 5.64; p = 0.0065). CONCLUSIONS: The significant reduction in the SP/AP ratio in the gentamicin-treated Ménière's group supports the hypothesis that gentamicin improves the electrophysiologic function of the cochlea, possibly by reducing the severity of the associated endolymphatic hydrops.

Acoustic Impedance Tests↗
PubMed1996

Auditory brainstem response. A comparison of different interpretation strategies for detection of cerebellopontine angle tumors.

In this retrospective study (111 tumor; 1370 non-tumor patients), the effectiveness of the auditory brainstem response for identifying cerebellopontine angle tumors was studied using different criteria to interpret the test. Individual ABR features were examined. The I-V was best (sensitivity = 82%; specificity = 97%) but present for only 44% of the population; I-III (sensitivity = 50%; specificity = 96%) and III-V (sensitivity = 30%; specificity = 97%) were worst. Ninety-three percent of patients had V and ILDV, with good results (sensitivity = 74% and 81% respectively; specificity = 93% each). Three interpretation strategies were compared: (1) included the latencies of V, ILDV, I-V, III-V and I-III and ILDI-V, (2) excluded III-V and I-III, (3) used I-V and ILDI-V when available; V and ILDV otherwise. When corrected for hearing loss, strategy 3 provided significantly better specificity (91%) than strategy 1 (87%), with no significant difference in sensitivity (92% and 93%, respectively).

Cerebellar Neoplasms↗
PubMed1994

Hearing preservation in acoustic neuroma surgery: value of monitoring cochlear nerve action potentials.

This study reviews the hearing results in 80 consecutive patients who underwent complete removal of histologically proven acoustic neuromas by use of the suboccipital approach. Of these, 56 patients had successful monitoring of cochlear compound action potentials; 20 were not monitored because their surgery predated monitoring; and 4 had unsuccessful monitoring. A significant difference was found in hearing preservation rates between the group in whom compound action potential monitoring was performed and those in whom monitoring was either unavailable or failed (p = 0.02). Overall, 38% (30 of 80) had preserved hearing. There were 51 patients in whom the click threshold for the cochlear compound action potential was measured during surgery. Twenty-one patients had a threshold shift of 20 dB or less, 15 (71%) of these retained serviceable hearing (speech reception threshold < or = 50 dB; speech discrimination score > or = 60%). Of 12 patients in whom the threshold shift was 30 to 60 dB, none had serviceable hearing after surgery. The click threshold shift was predictive of a significant postoperative hearing change (p < 0.001).

Action Potentials↗
PubMed1993

The effect of hearing loss on ABR interpretation: use of a correction factor.

Patients suspected of retrocochlear disorders often have abnormal ABRs in the presence of high-frequency hearing loss, making clinical decisions difficult. In a retrospective study of the ABR test results of 1539 patients, the false-positive and false-negative rates for ABR are presented as a function of hearing loss at 4000 Hz, both before and after using Selters and Brackmann's correction factor for hearing loss. For patients with more than 50 db HL at 4000 Hz the false-positive and false-negative rates, uncorrected for hearing loss, were 25.0% and 2.9% respectively, and when the correction factor was used were 12.5% and 5.8%. When hearing loss at 4000 Hz was over 90 dB the ABR was abnormal in 75% of nontumor patients. Conclusions are that a correction factor for hearing loss is helpful with reservations, and that ABR is not a useful test when 4000 Hz hearing loss is greater than 90 dB HL and 2000 Hz is greater than 75 dB HL.

Adolescent↗
PubMed1989

Cochlear nerve action potentials during cerebellopontine angle surgery: relationship of latency, amplitude, and threshold measurements to hearing.

The cochlear nerve action potential (AP) was monitored during two types of hearing preservation surgery: (1) removal of small cerebellopontine angle tumors and (2) retrolabyrinthine vestibular nerve section. The purpose of this investigation was to study the relationship between changes in intraoperative AP latency, amplitude, and threshold, and changes in audiometric hearing subsequent to surgery. The presence or absence of a cochlear nerve AP toward the end of surgery accurately predicted the presence or absence of postoperative hearing (93%). Regression analyses were performed to explore the relationship between audiometric pre- and postoperative thresholds and intraoperative AP threshold changes. Statistically significant relationships were found for (1) pre-operative audiometric thresholds and initial AP click thresholds (p = 0.0068); (2) final AP click thresholds and postoperative audiometric thresholds (p = 0.0003); (3) AP click (p = 0.0001) and 1 kHz (p = 0.0006) threshold shifts and pre- to postoperative audiometric threshold shifts. No relationship was found between either AP latency or amplitude values and postoperative hearing. Intraoperative threshold measurements can be used as an indicator of hearing change. If amplitude or latency indices are also monitored it may be better to use stimulus levels close to the evoked potential threshold.

Action Potentials↗
PubMed1988

Cochlear nerve monitoring during cerebellopontine angle operations.

The authors present their experience with intraoperative monitoring of cochlear nerve action potentials (AP) in 30 adult patients. Operative procedures were acoustic neuroma excision with attempted hearing preservation and selective vestibular neurectomy in patients with incapacitating Meniere's disease and serviceable hearing (SRT less than 50 db, discrimination greater than 60%). Loss of AP is detected rapidly and has been demonstrated after manipulation of the cochlear nerve and after coagulation of small arteries on the tumour capsule. Presence of an AP at the end of the procedure usually correlates with postoperative preservation of hearing. AP monitoring appears to be a reliable means of detecting potentially reversible changes in cochlear nerve function intraoperatively.

Action Potentials↗
PubMed1983

Diagnostic features of the auditory brainstem response in identifying cerebellopontine angle tumours.

This report concerns the diagnostic features of the ABR which are most effective in identifying patients with cerebellopontine angle tumours. The conclusions are based on the results of 40 normal subjects, 35 patients without a cerebellopontine angle tumour and 68 patients without a tumour. One hundred per cent of the tumour patients and ten per cent of the non-tumour patients had abnormal ABR results.

Adolescent↗
PubMed1983

Cerebellopontine angle lesions: an audiological test protocol.

Audiological test protocols were devised for use in patients suspected of having a cerebellopontine angle tumor. Data supporting the logic for inclusion of each test are presented. Protocol design was based on test results obtained in 45 tumor and 554 non-tumor patients. In summary, we found: 1) speech-in-noise results were of some value in those patients with normal hearing and of no value in those patients with hearing loss, 2) the acoustic reflex test gave misleading information in 25% of patients, and 3) the ABR test proved to be the most effective test in separating tumor and non-tumor patients. All individuals having cerebellopontine angle tumors and 11% of those without such lesions had abnormal ABR results in this series.

Acoustic Impedance Tests↗
PubMed1982

A comparison of three modes of hearing aid-telephone coupling.

The stray magnetic field emitted by telephone receivers has been used by hearing aid wearers to improve telephone communication. Recent technical advances by Bell Canada have eliminated the magnetic field. The company sponsored the design of a hearing aid modification to compensate for the loss of this magnetic field. This report concerns the evaluation of the modification. The results of two experiments indicated that it did not provide a satisfactory substitute for the magnetic field. A by-product of this project was the development of a device (audiometer-telephone interface) which permits simulation of telephone listening, thus allowing clinical assessment of a patient's telephone communication ability.

Adult↗