Lateralization of Bone Conduction into the Better Ear in Conductive Deafness: Paradoxical Weber Test in Unilaterally Operated Otosclerosis

Abstract

Patients with bilateral asymmetric conductive deafness due to otosclerosis were investigated to establish how B.C. lateralization (Weber) is affected when the poorer ear is transformed by stapes surgery into the better ear. B.C. lateralization was measured in 90 patients at different frequencies on the day before surgery and at various times up to maximum of 4 years post-operatively.

Three types of post-operative behaviour of B.C. lateralization have been observed:

1. Simultaneous reversal—lateralization reverses to the contralateral ear as soon as the operated ear becomes superior to the non-operated one.

2. Late reversal—lateralization shifts into the contralateral ear some weeks or months after the operated side has become the better ear.

3. No reversal—lateralization remains directed to the operated ear in spite of the fact that this side now has the better hearing. There is a Paradoxical Weber: lateralization into better ear in bilateral conductive hearing loss.

The factors ruling B.C. lateralization are discussed. The possible roles played by intercochlear intensity and intercochlear phase difference are analyzed and the presence of a third factor, that of “central habituation” is suggested.

Since longstanding deafness produces a relative sensory deprivation it is conceivable that a sudden hearing improvement can cause a temporary imbalance of the central evaluation of stimuli arriving from both cochleae. This may account for the phenomenon of gradual and late reversal of lateralization.