[Olfactory event-related potentials to isoamyl acetate in congenital anosmia]

To investigate the olfactory origin of the event-related potential (OEP) by evaluating OEP and standardized psychophysical measures in patients with congenital anosmia.

Olfactory function was evaluated by OEP and standardized psychophysical measures including smell identification test and odor detection threshold tests for 3 chemosensory stimulants: phenylethyl alcohol (PEA), isoamyl acetate (IAA), and chloracetyl phenone (CAP) in 9 subjects with isolated congenital anosmia and 9 age- and gender-matched normosmic controls.

There was a significant difference in the smell identification test score (P < 0.001) and odor detection thresholds for PEA and IAA (P < 0.001) between the anosmic and normosmic subjects. Detection thresholds for CAP, a trigeminal stimulant, did not differ between the 2 groups. In the control subjects, OEP to IAA was characterized by 4 reproducible components (P1, N1, P2 and N2). In the subjects with congenital anosmia, no reproducible evoked potential components were identified in response to IAA. No reproducible evoked potential components were seen in response to the air control stimulus in either the anosmic or normosmic groups.

These data suggest that OEP provide a specific and objective measure of olfactory function.