Biomedical subjects

Chris Halpin

Publications and source records attributed to Chris Halpin.

5 recordsLinked to original sources

PubMed2006

Using audiometric thresholds and word recognition in a treatment study.

OBJECTIVES: First, to examine a possible limit on significant results imposed by a progressive floor effect for hearing threshold improvement in a treatment study. This floor effect for hearing recovery suggests that if inclusion criteria are not set sufficiently high, the superiority of a treatment group may not be detectable. Second, to examine the outcomes when using two different types of criteria for significant change in a subject's word recognition score. METHODS: Several single-number criteria (e.g., 15 percentage points) are compared with the 95% (p=0.05) criteria from the binomial critical difference table for monosyllables. Critical differences for binomial variables change depending on whether the starting value lies in the middle (near 50% correct) or at either extreme of the range of scores (0 or 100%). Different judgments of significant word recognition improvement (or decrease) using binomial versus single-value criteria are presented. DATA SOURCE: A recent treatment study of sudden sensorineural hearing loss (n=318) is used to illustrate these effects. CONCLUSION: First, there is a progressive floor effect of presenting severity that co-varies with the outcome measure hearing threshold recovery. In some designs, this may act to constrain the ability to detect a significant difference. Second, in the example data set, the use of single-value criteria for significant within-subject change in word recognition (e.g., 15 percentage points) introduced a miscategorization error rate of approximately 9% when compared with the result of the binomial 95% critical difference table.

Audiometry, Pure-Tone↗

PubMed2005

Audiologic features of Norrie disease.

OBJECTIVES: Norrie disease is an X-linked recessive disorder in which patients are born blind and develop sensory hearing loss in adolescence. The hearing loss associated with Norrie disease has been shown in a genetically altered knockout mouse to involve dysfunction of the stria vascularis; most other structures are preserved until the later stages of the disease. The objective of this study was to characterize the audiologic phenotype of Norrie disease for comparison with the pathophysiologic mechanism. METHODS: The design combined two series of clinical audiologic evaluations, with special attention to speech intelligibility. RESULTS: The audiologic results for 12 affected individuals and 10 carriers show that patients with Norrie disease retain high speech intelligibility scores even when the threshold loss is severe. CONCLUSIONS: The cochlear mechanism-- failure of the stria vascularis-- accounts for some of the higher values in the wide distribution of speech scores in cases with similar pure tone audiograms.

Adult↗

PubMed2003

Oral steroid treatment of sudden sensorineural hearing loss: a ten year retrospective analysis.

OBJECTIVE: To describe ten years of experience with Sudden Sensorineural Hearing Loss and compare the outcomes with and without treatment with oral corticosteroids. STUDY DESIGN: Retrospective review of medical records. SETTING: Large specialty hospital, Department of Otolaryngology. PATIENTS: Patients presenting with sudden onset (72 hours) unilateral sensorineural hearing loss, with no evidence of Ménière's Disease, acoustic injury, retrocochlear disease, and other specifiable disorders. INTERVENTIONS: The majority of patients received a standard course of oral corticosteroids (Prednisone 60 mg and taper). A smaller group declined treatment. MAIN OUTCOME MEASURES: Recovery of hearing sensitivity was measured using standard audiometry and reported as change in Pure Tone Average. Word recognition scores were also analyzed. RESULTS: When severe-to-profound cases are analyzed, a significant improvement (p <.01) in Pure Tone Average is seen in cases treated with steroids versus those untreated. When milder cases are included, a statistical floor effect prevents differentiation of these groups. Word recognition scores were significantly improved (p <.05) in the treated group. CONCLUSIONS: Application of steroid medication significantly improves the recovery outcomes in cases of Severe Sudden Sensorineural Hearing Loss.

Administration, Oral↗

PubMed2002

Vascular defects and sensorineural deafness in a mouse model of Norrie disease.

Norrie disease is an X-linked recessive syndrome of blindness, deafness, and mental retardation. A knock-out mouse model with an Ndp gene disruption was studied. We examined the hearing phenotype, including audiological, histological, and vascular evaluations. As is seen in humans, the mice had progressive hearing loss leading to profound deafness. The primary lesion was localized to the stria vascularis, which houses the main vasculature of the cochlea. Fluorescent dyes showed an abnormal vasculature in this region and eventual loss of two-thirds of the vessels. We propose that one of the principal functions of norrin in the ear is to regulate the interaction of the cochlea with its vasculature.

Acoustic Stimulation↗

PubMed2002

The tuning curve in clinical audiology.

This article will explore the audiograms formed by the expected psychophysical thresholds from single, normally functioning inner hair cells. Like the audiogram formed by the vibrotactile response region, these psychophysical tuning curves represent fundamental limits in audiometry since they are the worst possible thresholds expected, even if no other cells are functioning. These examples can be put to many uses, but the most important lesson of the hypothetical tuning curve audiogram is that whereas each cell gives rise to thresholds across many frequencies, it cannot be expected to transmit more than one cell's worth of speech information. In the clinic, this means that even when many frequencies respond on the audiogram, there may be a much more restricted set of actual cells remaining in the cochlea, and only these remaining cells will respond, for example, to hearing aids.

Audiology↗