Olfactory bulb volume in patients with temporal lobe epilepsy.

The study aimed to investigate the volume of the olfactory bulb (OB) in patients with temporal lobe epilepsy (TLE). Specifically, we wanted to see whether the olfactory deficit typically found in TLE patients also exerts a top-down influence on the OB. Twenty patients, and 20 age- and sex-matched healthy controls underwent olfactory testing by means of the Sniffin' Sticks testing device (measurement of odor threshold, and identification abilities). In addition, they underwent an MR scan with 2-mm-thick T2-weighted fast spin-echo images without interslice gap in the coronal plane covering the anterior and middle segments of the base of the skull. Olfactory function was significantly impaired in TLE patients compared to healthy controls both at threshold level and for odor identification (p < 0.001); in addition, OB volumes were smaller than in controls (p = 0.013). The deficit seen at the level of the OB did not correlate with the side of the epileptic focus. Assuming that the olfactory deficit in TLE patients is due to the central nervous epileptic focus it appears that the OB volume is not only subject to changes in the periphery of the olfactory system, but also changes as a consequence to changes at a cortical level.