Auditory brain-stem potentials with unilateral pontine hemorrhage
E. J. Hammond, B. J. Wilder, I. J. Goodman and S. B. Hunter
Although there have been extensive anatomical and physiological studies in
animals, the actual neural sources, or even the laterality, of some
components of auditory brain-stem evoked potentials in humans are
uncertain. We studied these responses in a 56-year-old patient who had a
clearly demarcated pontine hemorrhage on the right side. The patient was
somnolent, with dense left hemiplegia and signs of involvement of right
cranial nerves V, VI, and VII. Stimulation of the left ear (ie,
contralateral to the lesion) evoked a normal series of waves with clearly
resolved positive components peaking at 2.0, 3.3, 4.8 (wave IV), and 6.0 ms
(wave V). Stimulation of the right ear (ie, ipsilateral to the lesion)
evoked only waves I, III, and IV. These results suggest that a pathway
ipsilateral to the stimulated ear is necessary and sufficient for
generation of auditory wave V and that wave IV is generated in bilateral
pathways.