Question
What options and recommendations are available for patients reporting unilateral tinnitus in their dead ear?
Answer
In cases of unilateral deafness with tinnitus, CROS, BICROS or transcranial stimulation, combined with training to improve space localization of the sound, is recommended. The goal is to reactivate parts of the auditory pathways, which received decreased input as a result of deafness. This approach is based on recent developments in neuroscience.
It is common knowledge that the nervous system exhibits an enormous amount of plasticity and that information from various sensory systems is integrated into a coherent entity. The visual and vestibular systems are classical examples of such a collaboration. It also has been recognized that, in the absence of sensory input, phantom perception occurs (phantom limb, phantom pain, tinnitus), with accompanied reorganization of receptive fields. A few years ago a new dramatic development was reported for controlling phantom pain and phantom limb by utilizing multisensory interaction (Ramachandran, Rogers_Ramachandran, 1996 ).
Phantom pain and phantom limb frequently cannot be controlled by any pharmacological or surgical approach. However, by introducing visual input, it turned out to be possible to control phantom pain in patients with one of their hands amputated. These patients were instructed to put the healthy hand into the box with a glass top and the mirror inside, so they saw only the healthy hand and its mirror reflection, which mimicked the missing hand, and to move the hand. After several sessions the phantom pain, which could not be controlled by other means, disappeared. Presumed mechanisms of action involved reorganization of receptive fields of somatosensory representation of the hands by visual input and partially restoring the balance disturbed by the lack of sensory input from the missing hand. Recent data with fMRI strongly supported this postulate (Borsook et al, 1998).
This information had direct effect on the treatment of tinnitus in patients with ipsilateral profound unilateral hearing loss or unilateral deafness. While the high level of plasticity of the nervous system was recognized long ago, the extent of plasticity and reorganization of receptive fields within the auditory system was not sufficiently appreciated. Recent data changed this situation dramatically with results showing reorganization of the tonotopic cortical maps due to the presence of tinnitus (Muhlnickel et al. 1998).
Based upon the results with phantom pain, the idea was to utilize the combined actions of the auditory and visual systems by fitting patients with CROS, BICROS or transcranial systems. This provided them with auditory information from a whole auditory space, which in combination with the information from the visual system would restore spacial localization of the sound, and modify receptive fields in the auditory pathways. The clinical results confirmed that these patients had partially restored their space localization of auditory stimuli (tested with closed eyes).
Furthermore, as hoped, this method also was helpful for their tinnitus. A systematic study on a large number of cases is needed, but results obtained so far are very encouraging. Patient are experiencing significant improvement of their tinnitus, and their ability of utilizing sound from the ''deaf side'' is substantially better, resulting in improved quality of life.
Borsook, D., Becerra, L., Fishman, S., Edwards, A., Jennings, S.L., Stojanovic, M., Papinicolas, L., Ramachandran, V.S., Gonzales, R.G., Breiter, H. (1998) Acute plasticity in the human somatosensory cortex following amputation. NeuroReport 9(6), 1013_7.
Muhlnickel, W., Elbert, T., Taub, E., Flor, H. (1998) Reorganization of auditory cortex in tinnitus. Proc. Natl. Acad. Sci. U.S.A. 95(17), 10340_3.
Ramachandran, V.S., Rogers_Ramachandran, D. (1996) Synaesthesia in phantom limbs induced with mirrors. Proc. R. Soc. Lond. B. Biol. Sci. 263(1369), 377_86.
BIO:
Pawel J. Jastreboff, Ph.D., Sc.D, is a Professor of Otolaryngology and Director of Tinnitus & Hyperacusis Center, Department of Otolaryngology at Emory University. Margaret M. Jastreboff, Ph.D. is an Associate Professor of Otolaryngology and Director of Academic Affairs at the Department of Otolaryngology, Emory University.