Intra-ponto-mesencephalic recording of binaural interaction in human brain-stem auditory evoked potentials.
Brain-stem auditory evoked potentials (BAEPs) were recorded at intraparenchymatous sites along a ponto-mesencephalic stereotactic penetration path in a patient with the rare condition of a ponto-medullary lesion which required biopsy but did not grossly alter scalp BAEPs. Click stimuli were applied either monaurally (with contralateral masking noise against acoustic cross-talk; conditions 'R,' 'L') or binaurally (condition 'RL'). A binaural interaction trace ('BI') was derived by subtracting the sum of the monaural from the binaural responses: BI = (RL)-(R + L). Despite failure to obtain significant BI components above noise level for scalp BAEPs, at the lower pons clearly discernible, multiphasic BI activity could be recorded beginning at the peak latency of scalp wave III and extending over approximately the next 4 msec. Its amplitude rapidly fell off with distance toward more rostral, mesencephalic recording sites. In relation to this positive finding, the equivocality among some of the previous studies on the detection of BI components in human scalp BAEPs is tentatively rephrased in terms mainly of a low signal-to-noise ratio and of functional peculiarities introduced by the respective stimulation protocols.
Department of Neurology, Klinikum Steglitz, Freie Universität Berlin, F.R.G.
G
G
Curio
K
K
Weigel
D000328:Adult; D001254:Astrocytoma / Q000601:surgery; D001932:Brain Neoplasms / Q000601:surgery; D001933:Brain Stem / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008526:Medulla Oblongata; D008636:Mesencephalon / Q000502:physiology*; D011149:Pons / Q000502:physiology*