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Biomedical subjects

D L McPherson

Publications and source records attributed to D L McPherson.

16 recordsLinked to original sources
PubMed1989

Auditory brainstem-evoked potentials in term infants born to mothers addicted to opiates.

A series of 20 normal newborn term infants and 12 infants born to mothers who had abused opiates during pregnancy were studied. Auditory brainstem-evoked potentials were used to describe neurophysiologic dysfunction in a group of drug-addicted term infants. Significant differences in the auditory brainstem-evoked potentials were found between the two groups. Specifically, a decrease in the central conduction times was noted for the I-III interpeak interval, suggesting neurophysiologic dysfunction in the area of the pons and cerebellum.

Evoked Potentials, Auditory↗
PubMed1987

Hydrocephalus: increased intracranial pressure and brain stem auditory evoked responses in the hydrocephalic rabbit.

The auditory evoked response (AER) was used to study the effect of increased intracranial pressure (ICP) on the auditory pathway in normal New Zealand rabbits and in those made hydrocephalic by intracisternal injections of kaolin. AERs were studied: (a) in the normal and then in the hydrocephalic animal; and (b) in the hydrocephalic animal during further ICP elevation by cerebrospinal fluid infusion. The AER was obtained from ongoing electroencephalographic activity after rarefaction auditory clicks presented at 90 dB sound pressure equivalent. In comparing base line normal AERs to those found in hydrocephalic conditions, a statistically significant increase in latency for AER components N2, P2, and P5 was noted in hydrocephalic rabbits. Increased ICP in the hydrocephalic model showed an increase in the latencies of AER components for P0 and P1 at 250 mm H2O, and a prolongation of P3-P5 central conduction time at 700 mm H2O above base line cerebrospinal fluid pressure. In addition, a decrease in the P4/N5 amplitude and an increase in P1-P3 central conduction times at 700 mm H2O was observed. The differences between normal and hydrocephalic rabbit AER base lines may be the result of the chronically increased ICP and presumed chronic anatomical changes within the auditory pathway due to kaolin itself. The differences in the AER from base line hydrocephalus to acute increased ICP may indicate that the hydrocephalic system is more sensitive to acute neuropraxic pressure effects on the brain stem auditory structures than is the normal brain.

Animals↗
PubMed1986

Cerebral cortical contributions to sensory evoked potentials: hydranencephaly.

The contribution of the cerebral cortex to the generation of sensory evoked potentials was studied in an infant with hydranencephaly. On CT scan no tissue above the thalamus was noted. Long-latency potentials to auditory stimuli were absent whereas the short-latency or brain-stem auditory evoked potentials and some of the components of the middle latency auditory evoked potentials (No and Po) were present. To visual stimulation only the electroretinogram was detected. To somatosensory stimulation only the spinal cord potentials could be detected. The absence of long-latency components in each of the sensory modalities supports the concept that these potentials require intact cerebral hemispheres in man.

Anencephaly↗
PubMed1985

Auditory brainstem response in infant hydrocephalus.

Fifteen infants with hydrocephalus ranging in age from 32 to 43 weeks from conception were studied. The auditory brainstem response (ABR) was measured 48 h prior to the placement of a CSF shunt and within 5 days following shunt insertion. Results of this study showed a general improvement in the ABR following placement of the shunt. No consistent patterns were observed that allowed a clear explanation of the cause and effect of the abnormal ABR. However, the changes seen in the ABR are caused by increased CSF pressure, which may compress the transmission fibers, and generators of the ABR producing a type of neuropraxis. Early shunting appears to have a better outcome on the ABR than later shunting.

Auditory Threshold↗
PubMedDate not supplied

Binaural interaction of the auditory brain-stem potentials and middle latency auditory evoked potentials in infants and adults.

Binaural interactions in brain-stem auditory evoked potentials and in middle latency auditory evoked potentials were studied in 18 normal hearing adults and 10 normal term infants. Binaural interactions at the times of ABR waves V and VI were comparable in term infants and adults. Binaural interaction during the time domain of the middle latency auditory evoked potentials was the greatest at N20 in term infants and at N40 in adults. Measurement of binaural interaction during maturation may be a useful tool in assessing neurologically affected infants.

Acoustic Stimulation↗
PubMedDate not supplied

Experimentally induced round window membrane lesions.

This investigation confirmed previous studies indicating that the middle and inner ear of the guinea pig have a pronounced tendency to healing. Middle ear hemorrhage of surgical origin appears to stop quickly in the guinea pig. A surgically created perforation of the round window with or without removal of perilymphatic fluid by suction resulted in a spontaneous healing of the round window membrane in 12/13 animals. Perilymphatic hemorrhage, associated with short post-surgical interval was found in a substantial number of cases. The origin of the perilymphatic hemorrhage is doubtful. Degeneration of the organ of Corti was found in four ears in three animals and appeared to be correlated to the perilymphatic hemorrhage. Electrophysiological measurements appeared to correlate well with the anatomical findings for one animal with very small changes and for three animals with pronounced middle and inner ear pathology. In three additional animals less agreement was observed. In general these animals showed a more pronounced decrease of function than would be expected by the anatomy.

Animals↗
PubMedDate not supplied

Auditory brain stem potentials recorded at different scalp locations in neonates and adults.

The auditory evoked brain stem potential was recorded in 14 normal full-term infants and nine normal-hearing adults. Silver-silver chloride electrodes were placed at nasion, forehead, vertex, each mastoid over the bony prominence, and the seventh cervical vertebra (noncephalic reference) in order to study the scalp distribution of the auditory brain stem response. Large differences in the scalp distribution between the newborn and adult populations were observed. At the ipsilateral mastoid, an x wave occurring at approximately 2 ms and a y wave occurring at approximately 3.3 ms were identified in the adult; this contrasts to a y wave at approximately 3.7 ms in the neonate. It appears that there are either separate generators for some of the components in the adult versus the neonate, and/or as the nervous system matures, myelinization occurs with a concomitant change in the scalp distribution of the auditory brain stem potentials.

Adult↗
PubMedDate not supplied

Preliminary observations of binaural hearing in an attention-deficit pediatric population.

Brainstem auditory evoked potentials and middle latency auditory evoked potentials were recorded from 21 normal hearing children between 8 and 13 years of age. An age-matched control group of 13 children was used to compare the results of 8 children diagnosed with ADHD. One sample of 2000 averages was collected for right monaural, left monaural, and binaural stimulus presentation conditions. The binaural interaction component was then determined using the formula: [(right monaural+left monaural)--binaural]. Absolute latencies and amplitudes for waves V, N20, P30, and N40 were then compared using descriptive statistics, analysis of variance, and matched t-tests. Percent binaural interaction was also computed for both groups. Significant differences were noted between control and ADHD groups on measures of N40 amplitudes for binaural stimulation, N40 amplitude for the sum of the right and left monaural waveforms, and percent binaural interaction at N40. These results suggest a dysfunction or immaturity in the auditory activity of the thalmo-cortical projections.

Adolescent↗