Does promethazine (Atosil) influence the human's early acoustically evoked potentials in the same way as the late potential N1?

Quantitative analysis of reversible dysfunction of brain-stem midline structures caused by disturbance of basilar artery blood flow with the auditory brain-stem responses

To clarify the effects of disturbances in basilar artery blood flow, basilar artery angiospasm was induced in 2 cats and 4 guinea pigs and auditory brain-stem responses (ABRs) were continuously recorded preceding, during and following the angiospasm. The angiospasm caused specific ABR changes in that waves II (P2-N2) and III (P3-N3) were attenuated without any corresponding amplitude reduction of P4. Those changes were equivalent following stimulation of either ear. Moreover, the ABR changes gradually recovered within 5 h. On the basis of the animal experiments, 52 patients with subarachnoid hemorrhage, supratentorial tumor showing increased intracranial pressure or hydrocephalus were selected for repeated ABR examinations. ABR abnormalities similar to those observed in the animal experiment were obtained especially from the patients exhibiting grade 3 or 4 symptomatology with subarachnoid hemorrhage. In these cases, the wave III to wave IV-V amplitude ratio was significantly decreased. In some cases the ABR abnormalities and the wave III to wave IV-V amplitude ratio recovered as the clinical course improved. These results support the conclusion that specific ABR changes (wave III to wave IV-V amplitude ratio) reflect transient ischemic dysfunction of the midline portion of the brain-stem caused by disturbances of basilar artery blood flow.

The effects of diazepam on the auditory brain stem responses

Sedation is widely used to improve the quality of auditory brain stem response (ABR) recording. This study demonstrated a small but significant increase in I-V interval following diazepam administration. There was no apparent effect on the ABR amplitudes.

Reference values and characteristics of brain stem audiometry in neonates and children

ABR (Auditory Brainstem Response) delivering the acoustic stimulus both through a headphone (PHN) and in free field (FF), have been recorded in 59 "normal" children divided into four age-related groups: (1) 22 children born at a gestational age ranging between the 36th and the 41st week; (2) 12 with ages ranging from 1 to 6 months; (3) 15 with ages ranging from 6 to 12 months; (4) 10 with ages ranging from 12 to 36 months. Peak latency values obtained with FF technique have been corrected by calculating the delay due to the distance between the loudspeaker and the tested ears (2.04 ms). When using this correction, no statistically significant differences were found between latency values of peaks JI and JV recorded using the two technique. While JI latency values of various groups do not differ significantly, groups 2--and especially group 1--JV latency values are statistically different from those of the 3rd and 4th group. This observation was confirmed by JV--JI interval values. JV wave in neonates (group 1), using PHN technique, is detectable at 60 dB p.e. SPL (82%) while in all other groups at 60 dB this wave is clearly detectable in all children (100%). Using FF technique, JV wave is still visible at 60 dB in 78% of the neonates (group 1) and in almost all children of the other groups. Considering ABR waveform, using PHN technique, in the first two groups only three waves are visible and the first one disappears at about 80 dB, while the typical 4--5 waves of normal adult tracings are detectable since 8--12 months of age. FF tracings instead show three peaks in all groups, the first (JI) being less evident when compared with the one obtained using PHN technique. JV amplitude values observed in FF are higher than those obtained delivering the stimulus through the headphone.

The dependence of early acoustically evoked potentials on age

Early acoustically evoked potentials (brain-stem potentials, latency up to 10 ms) were compared in two groups of varying age (25 and 63 years old, respectively). Although no age-dependent change in potential amplitudes was detected, a significantly longer latency period in older subjects was established for potentials III, IV, V, and VII at all levels of stimulus intensity. However, the difference in latency time between two consecutive responses shows that potentials IV and VI followed more quickly in the older than in the younger persons. An explanation of this discovery is attempted.