Abstracts

RATIONALE: Olfactory sense has previously been found to be impaired in epilepsy patients, and, in cases where unilateral olfactory impairment is identified, may be used to assist in seizure focus lateralization. Many available tests of olfaction can be costly and complicated to use. The Alberta Smell Test (AST; Green & Iverson, 1989) has been used in normal and head injured populations, and is reportedly an inexpensive, brief, and easily administered test of olfactory function. The purpose of the present study was to test the ease of administration and discriminability of the AST in epilepsy patients when compared to normal controls.
METHODS: The AST involves unilateral presentation of eight different scents to subjects who are asked to identify the odors from a choice card. There are 10 counterbalanced trials per nostril. Sixteen epilepsy surgical candidates and 16 healthy controls were tested. The epilepsy sample was 75% female (n = 12) while the control group was 63% female (n = 10). There were no significant differences between groups for age (epilepsy M = 34.2 years; control M = 33.6 years). The controls had more years of education than did the epilepsy subjects (epilepsy M = 13.9 years; control M = 17.3 years; p [lt] .01). The number of current smokers did not differ between groups (epilepsy n = 6; control n = 4). The epilepsy group had average intelligence (M WAIS-III FSIQ = 94.8 [12.3]), had a mean seizure onset of 19.0 (18.5) years old, and had had epilepsy for a mean of 15.2 (10.6) years. There were three epilepsy subjects with right hemisphere seizure focus, nine with left hemisphere focus, two with bilateral independent foci, and one with generalized onset as identified through video/EEG monitoring. In one subject, seizure semiology was consistent with complex partial seizures of temporal lobe origin, however, focus laterality was not clear and the subject did not seize during the video/EEG study. No subject reported a prior history of nasal injury, surgery, or polyps.
RESULTS: Using two-tailed t-tests, when the two groups were compared on the total score for the AST, the epilepsy subjects performed significantly worse than controls (epilepsy M = 11.5 [2.2]; control M = 14.7 [2.4]; p [lt] .01). Unilateral olfactory functioning in both the left and right nostrils was also significantly reduced in epilepsy patients as compared to controls (Right: epilepsy M = 6.0 [1.2]; control M = 7.3 [1.4]; p [lt] .01) (Left: epilepsy M = 5.5 [1.6]; control M = 7.4 [1.4]; p [lt] .01). The current sample was not large enough to perform analyses using seizure focus laterality.
CONCLUSIONS: The AST was brief (5 minutes) and easy to administer. All subjects tolerated the test without adverse effects. This olfactory measure was also found to discriminate epilepsy patients from normal controls, both in terms of overall performance and when each nostril was evaluated individually. These preliminary findings suggest that the AST is an effective, convenient, and inexpensive tool that can be used to investigate olfactory functioning in the epilepsy population. Further research will help to clarify whether the AST is useful in providing information regarding seizure focus laterality.