Epileptic olfactory auras: a clinical spectrum

To investigate the relative frequency of olfactory aura in a large number of patients with focal epilepsy, and examine the full clinical spectrum of epileptic olfactory auras (OAs) and their relationship to hemispheric lateralization and localization of epileptogenic focus.

This retrospective study was based on the medical records of 1384 patients with focal epilepsy. Of these, 71 (5.1%) patients were present with OAs, comprising 25 (35.2%) men and 46 (64.8%) women with a mean age of 35.43 ± 12.89 years. These 71 patients were classified according to the clinical features of the OAs, and the electroencephalography and magnetic resonance imaging findings were examined.

The relative frequency of OAs was 5.1% in the focal epileptic patients. The clinical spectrum of OAs in our cases was outlined as follows, complex OAs and elementary OAs. Elementary OAs were divided into three subgroups: elementary neutral OAs, elementary unpleasant OAs, and elementary pleasant OAs. In our cases, there was no difference between the right and left hemispheres in terms of lateralization of the epileptogenic focus. In all the 71 patients, the epileptogenic zone was most commonly localized in the temporal lobe (n = 58; 81.7%).

The relative frequency of OAs in focal epilepsies is likely to be found higher than expected. Elementary OAs occur much more frequently than complex OAs. Among the elementary OAs, elementary unpleasant OAs and elementary neutral OAs are the most common types, whereas elementary pleasant OAs are extremely rare.