Jack D. Clemis

The Large Vestibular Aqueduct Syndrome

It has long been known that abnormally large vestibular aqueducts may accompany congenital malformations of the cochlea and semicircular canals. Recently, enlargement of the vestibular aqueducts as the sole radiographically detectable inner ear anomaly has been recognized as a distinct pattern of congenital inner ear malformation. Patho‐genesis of the large vestibular aqueduct syndrome probably stems from an early derangement in the embryogenesis of the endolymphatic duct. This anomaly appears to be relatively common in children with sensorineural hearing loss and is probably significantly underdiagnosed. Hearing loss is typically bilateral and progressive, with stepwise rather than fluctuant hearing decrements often triggered by relatively minor head trauma. A review of 17 patients (33 ears) revealed an average hearing level at presentation of 57 dB with a speech discrimination score of 66%. Considerable variability exists in hearing level among affected ears, ranging from normal hearing (4%) to profound deafness (39%). In 12 patients (23 ears) with an average long‐term follow‐up of 7.3 years, the hearing loss progressed by an average of 25 dB, with a drop of 29% in speech discrimination over the period of observation. An endolymphatic to subarachnoid shunt was performed on seven ears in an effort to stabilize hearing. Four of these ears had a substantial immediate postoperative drop in hearing. For this reason, endolymphatic sac surgery is not recommended for patients with this deformity.The radiographic observation of 50 patients, each having an enlarged (greater than 1.5 mm. diameter) vestibular aqueduct, are analyzed. In addition to the aqueduct other associated inner ear anomalies have been identified in 60% of this population including: enlarged vestibule (14); enlarged vestibule and lateral semicircular canal (7); enlarged vestibule and hypoplastic cochlea (4); and hypoplastic cochlea (4). The large equeduct then presumably represents an arrested phase of inner ear development common to all 50 cases. Only 8 of these cases may fall into the Mondini or Mondini-Alexander classification wherein cochlear abnormalities have been identified. The size of the aqueduct ranged from 1.5 to 8 mm. in the anteroposterior diameter; the clinical incidence is 50 in 3700 consecutive cases referred for inner ear tomography. Bilateral involvement is twice as common as unilateral with a female to male predominance of 3:2. Most cases are associated with congenital hearing losses.

Brain stem electric response audiometry in the differential diagnosis of acoustic tumors

A brief history of the advances made in acoustic tumor diagnosis and treatment is presented indicating the benefits derived therefrom over the past 15 years. The recent application of brain stem electric response audiometry (BERA) as related to tumors affecting the auditory nerve is reviewed. Patients were considered to have a positive test result for tumor detection (abnormal BER) when their responses showed one of three characteristics: 1. wave V latencies were significantly different from the normal mean, 2. the interaural latency difference (ILD) was greater than .3 msec. (.4 msecs when the hearing loss was greater than 65 db HL), or 3. no response could be recognized at suprathreshold levels. An abnormal BER result was observed in 92.6% of 27 surgically proven tumors in this study. Two patients with surgically proven tumors had a false‐negative test. In a series of 115 nontumor patients with asymmetric sensorineural hearing losses of multiple etiology, one in three had an abnormal BER result. All conductive losses increased wave V latency values. The authors have concluded that an abnormal ILD is far from pathogmonic for a tumor affecting the auditory nerve; interpretive caution is recommended with even small conductive hearing losses. False‐negative responses are few, false‐positive responses are common (relative to tumor diagnosis). BERA is the most efficient audiometric test available today in our search for tumors affecting the auditory nerve. As such, this test probably heralds a new era in diagnostic audiology.

Hypoglossal — facial nerve anastomosis: A review of forty cases caused by facial nerve injuries in the posterior fossa

Hypoglossal‐facial anastomosis has been our procedure of choice in the repair of the permanently injured facial nerve in the cerebellopontine cistern, when the nerve cannot be primarily repaired. Total failures are few and complications are rare. Most results are good to excellent, if assessment is based upon realistic expectations. These include: 1. normal facial symmetry in repose, 2. good midface voluntary motion, 3. no reflex or emotional facial movement, 4. some synkinesis and donor‐injected mass facial movement, and 5. surprisingly little functional loss from hypoglossal paralysis.

Clinical Use of an Insert Earphone

There are several applications of and advantages to using an insert earphone. An insert earphone has three parts: a transducer to convert electrical energy to sound, a conduit to deliver the sound into the ear canal, and a coupler connecting the device to the canal. The data from this study indicate that there is a distinct advantage in using insert earphones over TDH-49 phones (standard headphones) in the attenuation of low frequency ambient noise. The use of insert earphones will permit one to test hearing in areas of higher ambient noise than was previously possible. Insert earphones are used to shorten the hearing aid selection process. A technique is described in which only one real ear measurement is required for an accurate hearing aid fitting. Most, but not all, of the masking dilemmas that are encountered with standard headphones are circumvented or eliminated by using insert earphones. In brain stem auditory evoked reponse testing, the insert earphone reduces the stimulus artifact without influencing the acoustic signal. Finally, the insert earphone solves the collapsing ear canal problem.

Audiograms derived from the brain stem response

Nineteen normal and 22 hearing impaired subjects were used in this study. Thresholds were determined by the following methods: 1. behavioral continuous tone, 2. behavioral tone burst, and 3. the brain stem electric response (BER) with tone bursts. A comparison of the BER thresholds with the behavioral thresholds are made for each subject. The difference between these three measures of threshold suggests that audiograms can be derived from the brain stem response threshold. The derived audiogram compares favorably with conventional audiograms. However, it must be remembered that the brain stem response is not hearing.

Sudden hearing loss in the contralateral ear in postoperative acoustic tumor: Three case reports†‡

Careful presurgical otologic assessment of the contralateral ear in acoustic tumor patients is essential, not only to establish baseline data but more importantly to resolve the intense patient anxiety that arises almost immediately when the diagnosis is presented. Any subsequent reduction in hearing acuity in the contralateral ear after the tumor ear has been deafened, poses serious psychological, socio‐economic and medical problems.

Effects of Conductive Hearing Loss on Auditory Brainstem Response

The purpose of this paper is not to propose that auditory brainstem response (ABR) be utilized for the assessment of conductive losses, but to define the effects of conductive hearing loss on the ABR when such a complication occurs. Conductive losses attenuate cochlear stimulation. Since wave V latency is inversely related to stimulus intensity, the magnitude of the conductive loss should be a predictor of the wave V latency delay. In this study, ABR wave V latencies from patients with known conductive losses due to canal occlusion, middle ear effusion, ossicular fixation and chain interruption were compared with latency values calculated from the magnitude of the loss. In those patients with occlusion of the external auditory canal and middle ear effusion, the shift of the wave V latency-intensity function correlated well with the air-bone gap. This correlation was poor for patients with ossicular chain disorders. In mixed hearing losses, the increased wave V latency due to the conductive component may totally mask an increase in latency caused by a retrocochlear component.

The contralateral ear in acoustic tumors and hearing conservation

Hearing conservation in acoustic tumor surgery is an admirable goal and a logical extension of micro neurotologic surgery, but ideal candidates for conservation are few, and attempts to preserve hearing in those few fail in about half of all cases. Conserved hearing most often falls far beyond a range that will provide binaural function and is, therefore, of questionable use. The problem of hearing conservation in acoustic tumor surgery is rationally approached based upon the implications of the total presurgical overview, particularly with reference to age, general health, tumor size, and especially hearing in the tumor ear, the contralateral ear, and interaural relationships. Technical considerations, the morbidity and mortality, and, finally, probability factors are reviewed from the literature. The patients consideration regarding potentials for hearing conservation, his need for conservation, and alternative options are discussed.

Acoustic reflex latency test in the evaluation of nontumor patients with abnormal brainstem latencies

The acoustic reflex latency test (ARLT), an indirect measure of neural conduction time utilizing the electroimpedance method, was used to evaluate 43 highly suspect, nontumor patients who demonstrated abnormal latency results on brainstem electric response audiometry (BERA), false-positive for tumor. Normative values and criteria for tumor-positive ARLT results were established on a control group using a second generation test unit, comprised of dual impedance bridges and a digital signal averager, designed especially to perform the ARLT. When cut-off criteria for both absolute reflex latency and interaural latency difference (ILD) values were applied to this BERA false positive population, the ARLT correctly identified 93% of patients as having end-organ lesions. Differences in ARLT and BERA test results are attributed to differences in 1) method of measurement, 2) characteristics of the eliciting signal, and 3) generation of the response. These factors are discussed as sources of variability. Both ARLT and BERA are recommended as tandem procedures when screening for acoustic or angle tumors.

A workable approach to the identification of neonatal hearing impairment

The American Hearing Research Foundation has developed a regional Infant Screening Program in the state of Illinois, designed to meet the vital need for early identification of hearing impairment on a mass scale. The four major components of the program include: 1. Application of the High Risk Register to the general newborn population, 2. Hearing Screening in the Intensive Care Nursery, 3. Electrophysiologic confirmation with Brain Stem Electric Response testing and 4. Subsequent and immediate remediation and/or habilitation.