Taste and smell phantoms revealed by brain functional MRI (fMRI)

Purpose: Our goal was to demonstrate the appearance of phantom tastes and s mells (phantageusia and phantosmia, respectively) by use of functional MRI (fMRI) of the brain and to demonstrate the efficacy of drug treatment that inhibited both the subjective presence of these phantoms and the fMRI brain activation initiated by these phantoms. Method: Multislice FLASH NR or echo planar MR brain scans were obtained in two patients with phantageusia and phantosmia in response to memory of two tastants (salt and sweet); memory of two odors (banana and peppermint); act ual smell of amyl acetate, menthone, and pyridine; and memory of phantom ta stes and smells before and after treatment with thioridazine and haloperido l. Activation images were: derived using correlation analysis, and ratios o f brain area activated to total brain area were obtained. Results: Prior to treatment, both patients experienced persistent birhinal and global oral obnoxious tastes and smells in the absence of any external stimulus. The fMRI response to memory of phantoms was activation in sensory -specific brain regions for taste and smell, respectively. fMRI activation was greater than for memory of any tastant or odorant or for actual smell o f any odor. After treatment with thioridazine or haloperidol, which success fully inhibited each phantom in each patient, fMRI response to phantom memo ry was significantly inhibited and was significantly lower than for memory of any tastant or odorant or actual smell of any odorant. Conclusion: These results demonstrate that (a) phantom taste and smell can be revealed by fMRI brain activation, (b) brain activation in response to t aste and smell phantoms is localized in sensory-specific brain regions for taste and smell, respectively, (c) brain activation in response to memory o f each phantom initiated the greatest degree of activation we had previousl y measured,and (d) treatment with thioridazine or haloperidol inhibited bot h the presence of each phantom and its associated fMRI brain activation. Th is is the first study in which phantom tastes and smells have been demonstr ated by an objective technique and treatment that inhibited the phantoms wa s characterized by objective inhibition of fMRI activation. These: two pati ents represent a relatively common group that may be classified as having p rimary phantageusia and phantosmia distinct from those with phantoms or aur as secondary to neurological, migrainous, psychiatric, or other causes.