Decrements in volume of anterior ventromedial temporal lobe and olfactory dysfunction in schizophrenia

Context: Patients with schizophrenia exhibit olfactory deficits, but it is unclear whether these represent a specific abnormality. The link between olfactory impairments and regional brain abnormalities has yet to be established. Objectives: To determine whether patients with schizophrenia exhibit volumetric deficits in the anterior ventromedial temporal lobe, the target for neuronal inputs from the olfactory bulb, and whether these are related to olfactory performance deficits. Design: A cohort study of patients and healthy control subjects who underwent both 1-mm spoiled-gradient echo magnetic resonance imaging and behavioral tests of olfaction and memory. Setting: Schizophrenia Research Center at the University of Pennsylvania, Philadelphia. Participants: Fifty-two patients with a DSM-IV diagnosis of schizophrenia and 38 healthy control subjects. Individuals were excluded for history of head trauma, significant substance abuse, and medical conditions affecting brain function or olfactory capacity. Main Outcome Measures: Gray matter volumes of the left and right temporal poles and the perirhinal and entorhinal cortexes; olfactory threshold detection sensitivity and identification test scores; composite indexes of verbal and spatial memory ability. Results: Patients had reduced volumes, relative to cranial size, in left (P=.003) and right (P=.01) perirhinal and left (P=.002) and right (P=.002) entorhinal cortexes, but not in the temporal pole. Perirhinal, but not entorhinal, cortical volume decrement was associated with decreased olfactory threshold sensitivity. Neither region was associated with impaired memory performance. Conclusions: Patients with schizophrenia have reduced cortical volumes in brain regions that receive afferents directly from the olfactory bulb. Behavioral olfactory deficits are related to structural brain abnormalities in these regions.