The effect of unilateral chorda tympani damage on taste

Patients with localized damage to the taste system often experience no subjective change in real-world taste experience. In an effort to understand this, eight patients who recently underwent acoustic neuroma removal were evaluated for taste loss. Localized taste testing showed that taste intensities decreased in the distribution of cranial nerve VII ipsilateral to tumor removal as expected, but asymmetries occurred for IX. Intensities were greater on the side contralateral to the tumor removal. In addition, palatal taste, also thought to be mediated by VII, was not totally abolished. It is concluded that cranial nerve IX is normally inhibited by cranial nerve VII in the taste network. When VII is damaged, this inhibition is abolished. This release of inhibition serves as a compensation mechanism that preserves normal taste experience.