Olfactory dysfunction in temporal lobe epilepsy: a case of ictus-related parosmia

Olfactory abnormalities in temporal lobe epilepsy (TLE) usually involve either brief hallucinations prior to seizures or chronic impairments in odor discrimination and identification. We describe the case of a man (B.C.) with TLE with an unusual presentation, an ictus-related parosmia. B.C. reported distorted perception of odor quality and hedonics that could provoke nausea and gagging, typically at its most extreme in the week or so following a seizure. Measures of B.C.'s olfactory functioning were obtained at stages of the ictal cycle when parosmia symptoms were severe and when they had decreased. Unlike other parosmics, B.C.'s detection thresholds were always normal, and unlike others with TLE, he evidenced little impairment in identification or discrimination. Testing during a period of more severe parosmia suggested that B.C.'s experiences might be the result of hedonic changes. We argue this may be the effect of seizure activity on the amygdala, which is known to be involved in mediating emotive reactions to odors.