Faculty Bibliography

Throughout the industrial world, technology and techniques are now available so that any child, no matter how young or how impaired, can have an accurate and precise assessment of middle ear function, auditory reactivity, and physiological processing of auditory stimuli. Yet, a major problem exists in the lack of timely identification of many children with hearing impairments. Presently, identification systems are primarily proactive and are based on technology. These consist of testing of infants with biological risk factors and the use of hearing screening programs at various times during the first decade of life. The reactive sources of referral appear to be inadequate, an impression that is supported by the data on the delay of diagnosis. These inadequacies appear to be due to a lack of awareness on the part of health providers as to the potential hearing losses; ignorance concerning the ability to diagnose them; and a lack of awareness of the potential of effective intervention. Two additional approaches are suggested which would be added to those already existing for improving the number of children who will have their diagnoses made in a timely fashion. The first of these is educational: health providers should have required and continuing education concerning the effects of hearing loss, the ability to diagnose, and to intervene effectively. A parallel educational program should be provided for the public. The second is the periodic assessment of speech and language from early infancy through the first few years of life for all children. This would enable children with suspected impairments to be referred for definitive testing.(ABSTRACT TRUNCATED AT 250 WORDS)

The contrast-enhanced computed tomographic (CT) scans of the temporal bone and brain in 18 patients with otologic disease and acquired immunodeficiency syndrome (AIDS) were retrospectively reviewed. Seven scans revealed middle ear and mastoid disease; three scans were consistent with central nervous system (CNS) pathology; and eight scans demonstrated no abnormalities. CT scanning was found useful in localizing otopathology and diagnosing CNS toxoplasmosis, aural polyps, osteomyelitis, mastoiditis, and middle ear effusion due to hypertrophic lymphoid tissue. The authors conclude that AIDS patients with sensorineural hearing loss should undergo contrast-enhanced brain CT scans to rule out CNS pathology; AIDS status does not alter criteria for CT scanning in patients with conductive hearing loss; and that images of the nasopharynx should be included on temporal bone CT scans of patients with conductive hearing loss in order to exclude eustachian tube obstruction by hypertrophic lymphoid tissue

DNA analysis by flow cytometry was performed on tissue blocks from 41 patients with nasopharyngeal carcinoma. The histologic slides were reviewed by a pathologist and blindly classified according to the World Health Organization classification. The paraffin-embedded blocks were processed to obtain individual nuclei, which were then stained with propidium iodide. The nuclei were analyzed on a flow cytometer. Excluding 10 uninterpretable histograms, the remainder were interpreted blindly and classified as diploid or aneuploid. The Cox proportional hazards survival model was used to analyze stage, histology, radiation dose, and ploidy. We observed more diploids (23 of 31; 74%) than aneuploids (eight of 31; 26%). The 2-year survival rate of diploids was 55%, compared with 25% of aneuploids (P less than .05). We conclude that ploidy status is an independent prognostic factor in nasopharyngeal carcinoma

Facial nerve paralysis associated with cerebellopontine angle surgery has been reported to range up to 26% in a recent series. Various methods of intraoperatively monitoring the facial nerve have been developed to reduce the incidence of facial paralysis. We report our experience with an intraoperative monitoring technique using intramuscular EMG electrodes to detect subclinical electrical responses that were amplified and made audible to the operating surgeon after gating stimulus artifacts. A 3.6% incidence of facial paralysis in 111 consecutive cases with this intraoperative monitoring method compared with 14.5% in 207 previously unmonitored cases indicates significant reduction of this complication in cerebellopontine angle surgery (p less than 0.001). Along with this reduction in facial paralysis, an increase in the percentage of partial facial paresis was observed in the monitored group (p less than 0.05). The percentage of those with intact facial function was similar in the monitored (82.0%) and unmonitored groups (78.3%)

One way in which animals localize sounds along the horizon is by detecting the level differences at the 2 ears. Neurons in the lateral superior olive (LSO) encode this cue by integrating the synaptic drive from ipsilateral excitatory and contralateral inhibitory connections. This synaptic integration was analyzed in 400-500-microns brain slices through the gerbil superior olive. Intracellular recordings from LSO neurons were obtained during the application of independent or conjoint electrical stimuli to the excitatory afferent and inhibitory afferent pathways. Stimulation of ascending fibers from the ipsilateral cochlear nucleus reliably evoked EPSPs and action potentials. Stimulation of the medial nucleus of the trapezoid body (MNTB) consistently evoked IPSPs. The evoked postsynaptic potentials differed in that IPSPs were 2 times the duration of EPSPs. An electrophysiological estimate of convergence indicated approximately 10 excitatory and 8 inhibitory afferents per LSO neuron. MNTB stimulation suppressed synaptically evoked action potentials. When stimulus amplitude was increased to the excitatory pathway, it was generally found that a greater MNTB stimulus was necessary to suppress the action potential. A similar commensurate rise in ipsilateral and contralateral acoustic stimulation was also found to be necessary to give the same criterion response. These results confirm that the LSO can integrate evoked action potentials and IPSPs to encode interaural level. Increasing stimulus voltage was found to decrease both action potential and IPSP latency, suggesting that intensity information may be encoded with temporal cues in the nervous system. It was also found that an evoked burst of action potentials could be inhibited in such a way as to yield intermediate discharge rates, dependent on contralateral stimulus level. Taken together, these results suggest that certain properties related to level-difference coding may be available for intracellular analysis using the brain-slice preparation. Several temporal characteristics of the synaptic potentials, including latency and duration, may play a critical role in this simple computation

For patients with head and neck squamous carcinoma, a clinical response to induction chemotherapy has correlated with a survival advantage. Similarly, patients with diploid tumors have displayed a survival advantage when compared with patients with aneuploid tumors. This study examined DNA content in 33 patients who had undergone induction chemotherapy as part of two clinical protocols to determine if there was a correlation between the patients with diploid tumors and the patients with a clinical response to chemotherapy. Although patients with stage III tumors had a longer disease-free survival than stage IV patients (p less than 0.0002), the addition of DNA content information did not improve the ability to predict response. Specifically, there was no correlation between DNA content and the response to chemotherapy. In addition, for this group of patients, a diploid DNA content was not correlated with a survival advantage. We conclude that DNA content information did not add significantly to the prediction of clinical outcome in these patients who received induction chemotherapy

The purpose of the present study was to analyze and compare the amplitude spectra of ABRs recorded from 40 elderly and 40 young subjects in order to determine if there are any age related differences. A spectral analysis was performed on each subject's ABR. It was found that the ABRs recorded from older subjects have a significantly greater amount of low frequency spectral energy than ABRs recorded from young subjects. This difference was attributed to the greater amount of low frequency background noise found in the ABRs of older subjects. Modification of standard recording procedures should be considered when ABRs are recorded from older subjects.