Electrically Stimulated Olfactory Evoked Potential in Olfactory Disturbance

Abstract

Olfactory evoked potential is considered a useful method of electrophysiological olfactometry for the diagnosis of olfactory disturbance. However, electrophysiological olfactometry is not as widely used as electrophysiological audiometry, such as the auditory brain stem response, because odor stimulation is difficult to perform. In contrast, electrical pulse stimulation is easy to perform, and its evoked potential is also easily recorded by the averaging method. We recorded olfactory evoked potentials from the scalp produced by electrical stimulation on the olfactory mucosa and investigated the relationship between this electrical olfactory evoked potential (EOEP) and the results of Toyoda and Takagi's perfumist's strip method (T&T) olfactometry, which is a standard Japanese means of psychophysical olfactometry. In EOEP-detectable cases, the detection and cognitive thresholds of T&T olfactometry were 1.32+/-1.99 (mean +/- SD; n = 10) and 3.02+/-1.64 (n = 10), respectively. But in the undetectable cases, the thresholds were 4.67+/-2.03 (n = 8; 5.8 means off the scale) and 5.80+/-0.00 (n = 8), respectively. The differences between the T&T thresholds of EOEP-detectable and -undetectable cases were significant. We concluded that EOEP is suitable for electrophysiological olfactometry.

Examination of chemosensory functions in patients with dysosmia

“…Our T&T result showed significantly decreased olfactory function in comparing patients to healthy subjects, and similar trends were observed in the Ishimaru et al [9] study. T&T examination is sensitive to the smell loss of Japanese sinusitis/polyposis patients [12] and has been used as a “subjective” examination of olfactory function in Chinese clinics for many years.…”

“…In this study, the results were interpreted by the following criteria: subjects had normal olfactory function if T&T results were normal and oERPs were detectable at the same time; subjects had functional anosmia if T&T results indicated anosmia and oERPs were undetectable at the same time; subjects might have hyposmia if T&T results indicated hyposmia and oERPs were undetectable, possibly because detection of oERPs was interfered with by blinking movement or hyperactivity of facial muscles during examination; subjects still had olfactory function if T&T results indicated functional anosmia and oERPs were detectable. Ishimaru et al [9] examined 14 patients using T&T and EOEP methods and observed a T&T value greater than 5.8 in 1 patient with detectable EOEP. Lötsch et al [15] also observed detectable oERPs in 20% of patients with functional anosmia, a result consistent with ours.…”

“…Briefly, quantitative analysis was based on the dilution time of 5 odorants (rose, scorched, rotten, fruit and stool), each substance at 8 concentrations (10 2 ~10 5 ) which represented 8 degrees (−2 to +5). Average odor threshold, which was obtained by dividing the sum of identification threshold for 5 olfactory substances by 5, was used to judge the degree of olfactory injury [9]. …”

“…Because odor discrimination largely relies on olfactory sensation [7], physicians should not only examine hypogeusia but also investigate potentially concomitant hyposmia when subjects complain about tasteless food. Currently, the common methods used in clinical laboratories include olfactory event-related potentials (oERPs) [8] and T&T olfactometer [9] for olfactory examination, trigeminal event-related potentials (tERPs) [10] for trigeminal nerve examination, and triple drop method for gustatory examination [11]. The purpose of the present study was to exam 272 subjects using the above methods to investigate changes of the chemical sensory functions in patients with dysosmia in a Chinese population.…”

Intranasal trigeminal chemosensitivity in patients with postviral and post-traumatic olfactory dysfunction

“…In brief, quantitative analysis was determined by the dilution of five odorants (A, b-phenyl ethyl alcohol; B, methyl cyclopentenolone; C, isovaleric acid; D, g-undecalactone; and E, skatole), each at eight concentration series (10 -2~1 0 5 ), which were represented by 8 degrees (-2 to + 5) and zero represents the average detection threshold of normosmic subjects. Average odor threshold, which was obtained by dividing the sum of the identification threshold for five olfactory substances by five, was used to judge the degree of olfactory injury [7].…”