Maturation of the auditory system in clinically normal puppies as reflected by the brain stem auditory-evoked potential wave V latency-intensity curve and rarefaction-condensation differential potentials.

OBJECTIVE: To evaluate auditory maturation in puppies. ANIMALS: Ten clinically normal Beagle puppies. PROCEDURE: Puppies were examined repeatedly from days 11 to 36 after birth (8 measurements). Click-evoked brain stem auditory-evoked potentials (BAEP) were obtained in response to rarefaction and condensation click stimuli from 90 dB normal hearing level to wave V threshold, using steps of 10 dB. Responses were added, providing an equivalent to alternate polarity clicks, and subtracted, providing the rarefaction-condensation differential potential (RCDP). Steps of 5 dB were used to determine thresholds of RCDP and wave V. Slope of the low-intensity segment of the wave V latency-intensity curve was calculated. The intensity range at which RCDP could not be recorded (ie, pre-RCDP range) was calculated by subtracting the threshold of wave V from threshold of RCDP RESULTS: Slope of the wave V latency-intensity curve low-intensity segment evolved with age, changing from (mean +/- SD) -90.8 +/- 41.6 to -27.8 +/- 4.1 micros/dB. Similar results were obtained from days 23 through 36. The pre-RCDP range diminished as puppies became older, decreasing from 40.0 +/- 7.5 to 20.5 +/- 6.4 dB. CONCLUSION AND CLINICAL RELEVANCE: Changes in slope of the latency-intensity curve with age suggest enlargement of the audible range of frequencies toward high frequencies up to the third week after birth. Decrease in the pre-RCDP range may indicate an increase of the audible range of frequencies toward low frequencies. Age-related reference values will assist clinicians in detecting hearing loss in puppies.

Urinary bladder cortical evoked potentials in man: suitable stimulation techniques.

A practical and easily applicable method of recording cortical potentials evoked by bipolar electrical stimulation of the bladder wall is described. This constitutes an objective electrophysiological test of afferent bladder central projections. Comparison of bipolar and monopolar methods of intravesical stimulation led to the conclusion that the simpler monopolar intravesical electrode technique is unsuitable because it yields potentials contaminated by extravesical components.

Neurophysiological assessment of the central motor pathway to the external urethral sphincter in man.

A recently developed neurophysiological method by which the motor cortex in man can be electrically stimulated has been applied to the assessment of the central motor pathway to the external urethral sphincter. It was observed that there was parallel activation of the anal sphincter, the pelvic floor and the lower limb muscles, voluntary facilitation and marked inhibition during micturition. This method can be used to assess the volitional and the various segmental and suprasegmental influences on the behaviour of the external urethral sphincter. Unfortunately, the poor tolerance of subjects to the scalp sensations caused by the electrical stimulus is a major limitation to its clinical use, though this should be obviated by the introduction of a cortical magnetic stimulator.