Robert W. Keith

Lead exposure and the central auditory processing abilities and cognitive development of urban children: The cincinnati lead study cohort at age 5 years

This analysis examined the relationship between lead exposure as registered in whole blood (PbB) and the central auditory processing abilities and cognitive developmental status of the Cincinnati cohort (N = 259) at age 5 years. Although the effects were small, higher prenatal, neonatal, and postnatal PbB levels were associated with poorer central auditory processing abilities on the Filtered Word Subtest of the SCAN (a screening test for auditory processing disorders). Higher postnatal PbB levels were associated with poorer performance on all cognitive developmental subscales of the Kaufman Assessment Battery for Children (K-ABC). However, following adjustment for measures of the home environment and maternal intelligence, few statistically or near statistically significant associations remained. Our findings are discussed in the context of the related issues of confounding and the detection of weak associations in high risk populations.

An effect of linguistic experience. Auditory word discrimination by native and non-native speakers of English.

In this study, the effect of linguistic experience on the auditory discrimination of words has been examined. 18 subjects, including 6 native and 12 non-native speakers of English, were tested with CID auditory test W-22 in quiet and in the presence of white noise at the signal-to-noise (S/N) ratios of +12, +6 and 0 dB. The non-native speakers of English included 6 with 1 year of experience and 6 with 3-4 years of experience speaking Enligsh in the USA. In the absence of noise, the results were essentially equivalent for all three groups. As noise level increased, word discrimination deteriorated for all three groups with non-native speakers of English obtaining results significantly poorer than native speakers of English. Linguistic experience and noise levels were significant at the 0.001 level fo confidence. It appears that at 0 dB S/N, individual variability of non-native speakers of English, regardless of their original linguistic background, was much smaller than that found for native speakers of English. The results of the study tend to indicate that a limited linguistic experience results in a persistent deterioration of auditory word discrimination under impoverished conditions of audition.

Transpetrosal access to meningiomas juxtaposing the temporal bone

Meningiomas arising from the petroclival dura have presented a challenge to both otolaryngologists and neurosurgeons. Access by means of subtemporal, suboccipital, translabyrinthine, or transcochlear routes have inherent limitations both surgically as well as from resultant morbidity.

Intraoperative Monitoring of the Vagus Nerve during Intracranial Glossopharyngeal and Upper Vagal Rhizotomy

Intracranial section of the glossopharyngeal and upper vagal rootlets for the treatment of vagoglossopharyngeal neuralgia may cause dysphagia or vocal cord paralysis from injury to the motor vagal rootlets in 10% to 20% of cases. To minimize this complication, we recently applied a technique of intraoperative monitoring of the vagus nerve (previously described by Lipton and McCaffery to monitor the recurrent laryngeal nerve during thyroid surgery) in a patient undergoing intracranial rhizotomy for vagoglossopharyngeal neuralgia. By inserting an electrode in the ipsilateral false vocal cord and stimulating the rostral vagal rootlets intraoperatively under general anesthesia, we could differentiate the rostral vagal motor rootlets from the sensory rootlets. In this patient, the technique allowed us to preserve a rostral vagal rootlet, which if sectioned, could have caused dysphagia or vocal cord paralysis. We conclude that intraoperative monitoring of the rostral vagal rootlets is an important technique to minimize complications of upper vagal rhizotomy.

Effect of middle-ear dysfunction and disease on hearing and language in high-risks infants

The effect of middle-ear dysfunction and disease on hearing and language development at one year of age was evaluated for 143 high-risk infants. These infants were categorized as normal or abnormal based on otologic history, otoscopic examinations, and on tympanometric examinations. Language was significantly related to gestational age, being delayed by approximately the amount of prematurity. Language scores were therefore adjusted for gestational age. Speech-detection threshold was not related to gestational age, and was used as the measure of hearing. Hearing levels were negatively correlated with adjusted language quotients. Infants with abnormal otologic histories reported were not different from infants with normal histories in either hearing or language development. Infants with bilateral otoscopic abnormalities had significantly higher speech-detection thresholds, but did not differ in language development from those with bilaterally normal otoscopy. Infants who were abnormal bilaterally by tympanometric examination had significantly higher speech-detection thresholds as well as significantly delayed language development. A significant effect on both hearing and language was found among those infants bilaterally abnormal by tympanometry for whom evidence of middle-ear disease was not visualized by otoscopic examination. Implications of these findings are discussed.