Olfactory Dysfunction in Schizophrenia and Temporal Lobe Epilepsy

Background: Schizophrenia and mesial temporal lobe epilepsy (TLE) represent two common brain disorders that share dysfunction of temporo-limbic neural substrates.

Objective: We evaluated whether patients with schizophrenia exhibited olfactory performance more similar to right or left temporal lobe epilepsy patients.

Methods: Odor identification ability and detection threshold sensitivity were measured in 40 patients with schizophrenia, 14 patients with right- and 18 patients with left-temporal lobe epilepsy (TLE) patients, and 25 healthy controls. Odor identification was assessed with the University of Pennsylvania Smell Identification Test (UPSIT) and odor detection threshold sensitivity with a single-staircase procedure using the stimulant phenyl ethyl alcohol (PEA).

Results: Relative to controls, only patients with schizophrenia and right TLE exhibited significant impairment in UPSIT performance. Left TLE patients and controls performed comparably on the UPSIT. Detection threshold sensitivity to PEA did not differ significantly among the four groups.

Conclusions: These data suggest a greater reliance of olfactory processing on right hemisphere structures and are also consistent with recent neuroimaging studies that have implicated aberrant processing of olfactory information in right hemispheric brain regions in schizophrenia.