Development of low-frequency tone burst versus the click auditory brainstem response.

Often ABR threshold testing employs clicks to assess high-frequency hearing, and low-frequency tone bursts to assess low-frequency sensitivity. While a maturation effect has been shown for click stimuli, similar data are lacking for low-frequency toneburst stimuli. Thus, 305 infants ranging in conceptional age (CA) from 33 weeks to 74 weeks were tested. Absolute latencies were measured for wave V at 55, 35, and 25 dB nHL in response to a click and for wave V500 in response to a 500 Hz tone burst. Major wave latency in response to 500 Hz tone bursts decreases with age and do not stabilize by 70 weeks CA. Likewise, waves III and V latencies in response to clicks decrease with age, as has been reported by others, and do not stabilize by 70 weeks CA. Wave I latency produced by clicks did not decrease with age, being mature by 33 weeks CA.

Doctor of audiology (AuD) program at the University of South Florida.

This article describes the doctor of audiology (AuD) program at the University of South Florida (USF). The USF AuD program has been operational since the fall of 1999 and, to date, 47 students have graduated from either the postbaccalaureate track or the post-master's track. The faculty consists of 9 full-time and 8 part-time adjunct members who provide a curriculum that covers the audiology scope of practice. Being located in a major metropolitan area allows for diverse clinical practicum experiences that result in students being prepared to become autonomous professional practitioners.

An abbreviated word recognition protocol based on item difficulty.

OBJECTIVE: The purpose of this investigation was to develop a test methodology that would identify those patients requiring a full 50 item word recognition test and allow abbreviated testing of patients who do not need a full 50 item word recognition test. DESIGN: Listeners with normal hearing and listeners with sensorineural hearing loss were administered Auditec trade mark recordings of a 50 word NU-6 list(s). From these listener responses, error rates were determined for each word in the NU-6 word pool. The NU-6 lists were then reordered based on decreasing word difficulty and 10 word and 25 word screening tests were developed. The predictive power of the 10 word and 25 word screening tests was then determined based on the 95% critical difference values for word recognition scores. Clinical decision analysis (CDA) was used to assess how well the 10 word and 25 word screening tests predicted 50 word performance. RESULTS: Data analyses showed: 1) the four NU-6 50 word lists were equivalent in item difficulty; 2) the four NU-6 10 word and 25 word lists were equivalent in item difficulty; and 3) the 10 word and 25 word screening tests have hit rate (HR) values of 93 to 100%, false alarm rate (FAR) values of 0 to 20% and A' values of 0.946 to 1.00 depending upon word configuration and pass criterion. CONCLUSIONS: The four NU-6 10 word and 25 word screening tests differentiated listeners with impaired word recognition ability who required a full 50 word test from listeners with unimpaired word recognition ability who required only a 10 word or 25 word test.

Unilateral hearing loss in children with shunt-treated hydrocephalus.

This study investigated the characteristics of hearing loss in children with ventriculoperitoneal (VP) shunted hydrocephalus. Twelve hydrocephalic children with patent VP shunts participated. The etiology of the hydrocephalus was either intraventricular hemorrhage or spina bifida. Audiometric examination included pure-tone air conduction thresholds, tympanometry, contralateral and ipsilateral acoustic reflex thresholds (ARTs), and distortion product otoacoustic emissions (DPOAEs). A unilateral, high-frequency, cochlear hearing loss was found in the ear ipsilateral to the shunt placement in 10 (83%) of the 12 shunt-treated hydrocephalic children. No hearing loss was observed in the ear contralateral to shunt placement. Based on the pure-tone audiometric findings, coupled with the decrease in DPOAE amplitude in the shunt ear, the hearing loss appears to be cochlear in nature. We suggest that cochlear hydrodynamics are disrupted as the result of reduced perilymph pressure, a consequence of cerebrospinal fluid (CSF) reduction due to the combined effects of a patent shunt and a patent cochlear aqueduct. In addition, a concomitant brain stem involvement is evidenced in the ART pattern, possibly produced by the patent shunt draining the CSF from the subdural space, resulting in cranial base hypoplasia.

The effect of midline petrous apex lesions on tests of afferent and efferent auditory function.

OBJECTIVES: Historically, audiological procedures have focused on the assessment of the afferent (ascending) cochlear-VIIIth nerve system and have, for the most part, ignored the efferent (descending) auditory system. We report afferent and efferent auditory test results for two cases with a cholesterol cyst of the right petrous apex; one lesion involves the afferent segment of the auditory system, and the second lesion involves both the afferent and efferent segments of the auditory system. These "natural experiments" provide a unique opportunity to study the effect of a space-occupying lesion of the petrous apex on afferent and efferent function of the auditory system. DESIGN: Transient evoked otoacoustic emission (TEOAE) suppression studies were performed to assess the effect of the cholesterol cyst on the efferent system of the two cases. In addition, three complementary afferent tests of brain stem auditory function were administered: 1) acoustic reflex thresholds (ARTs); 2) masking level difference (MLD); and 3) auditory brain stem response (ABR). These tests are complementary because the superior olivary complex (SOC) is involved not only in the mediation of the sound evoked efferent reflex assessed in TEOAE suppression, but in the mediation of the ARTs, the MLD, and the ABR. RESULTS: The two cases with midline petrous apex lesions, one not involving the VIII-cochlear efferent auditory system, differed from each other with regards to TEOAEs suppression, and ARTs. Specifically, the case with only afferent involvement produced normal TEOAE suppression, a normal MLD, normal ARTs, and abnormal waves III and V of the ABR, whereas the case with both afferent and efferent involvement produced abnormal TEOAE suppression, a normal MLD, abnormal ARTs, and abnormal waves III and V of the ABR. CONCLUSIONS: These cases illustrate that although several auditory tests can be mediated within the same or adjacent anatomical structures, i.e., the SOC, they may not be equally affected by the same lesion due to different physiology. Further, the TEOAE suppression paradigm is a clinically relevant test to assay the sound evoked efferent reflex that is mediated by the medial olivocochlear system of the SOC.

Effectiveness of Central Auditory Processing Tests With Children.

The purpose of this investigation was to determine central auditory processing (CAP) individual test efficacy and test battery efficacy and to estimate the costs that are associated with the identification of a targeted sample. Ninety-one children with normal learning (NL) abilities and 147 children with a classroom learning disability (CLD) and presumed CAP disorders (CAPDs) ranging in age from 7 to 13 years were given a battery of seven CAP tests. The test battery consisted of: (1) Binaural Fusion Test (BFT), (2) Masking Level Difference (MLD) test, (3) Filtered Speech Test (FST), (4) Time Compressed Speech (TCS) test, (5) Dichotic Digits Test (DDT), (6) Staggered Spondaic Word (SSW) test, and (7) Pitch Pattern Test (PPT).We believe that this investigation is the first report regarding the assessment of the utility of CAP tests using clinical decision analysis (CDA). We determined that the BFT separated the two samples most effectively and that the FST was the next most effective. A test protocol with BFT and FST or BFT and MLD represented the best battery approach when hit rate, false positive rate, and cost factors were considered. However, if the intent is to be certain that a child with CLD has CAPD given a positive test result, then the BFT and MLD would be the test battery of choice.