Unilateral olfactory sensitivity in multiple sclerosis.

It is not known whether lateralized olfactory sensitivity deficits are present in MS. Since projections from the olfactory bulb to the olfactory cortex are largely ipsilateral, and since both functional imaging and psychophysical studies suggest that the right side of the brain may be more involved in olfactory processing than the left, we addressed this issue by administering well-validated tests of odor detection, along with tests of odor identification, to each side of the nose of 73 MS patients and 73 age-, gender-, and race-matched normal controls. We also determined, in 63 of the MS patients, whether correlations were present between the olfactory test measures and MRI-determined lesions in brain regions ipsilateral and contralateral to the nose side that was tested. No significant left:right differences in either olfactory sensitivity or identification were present, although in both cases mean performance was lower in the MS than in the control subjects (ps<0.0001). Scores on the two sides of the nose were positively correlated with one another (threshold r=0.56, p<0.0001; Identification r=0.71, p<0.0001). The percent of MS patients whose bilateral test scores fell below the 10th percentile of controls did not differ between the odor identification and detection threshold tests. Both left and right odor identification and detection test scores were weakly correlated with lesion volumes in temporal and frontal lobe brain regions (r's<0.40). Our findings demonstrate that MS does not differentially influence odor perception on left and right sides of the nose, regardless of whether sensitivity or identification is being measured. They also indicate that tests of odor identification and detection are similarly influenced by MS and that such influences are associated with central brain lesions.

Taste dysfunction in multiple sclerosis.

Empirical studies of taste function in multiple sclerosis (MS) are rare. Moreover, a detailed assessment of whether quantitative measures of taste function correlate with the punctate and patchy myelin-related lesions found throughout the CNS of MS patients has not been made. We administered a 96-trial test of sweet (sucrose), sour (citric acid), bitter (caffeine) and salty (NaCl) taste perception to the left and right anterior (CN VII) and posterior (CN IX) tongue regions of 73 MS patients and 73 matched controls. The number and volume of lesions were assessed using quantitative MRI in 52 brain regions of 63 of the MS patients. Taste identification scores were significantly lower in the MS patients for sucrose (p = 0.0002), citric acid (p = 0.0001), caffeine (p = 0.0372) and NaCl (p = 0.0004) and were present in both anterior and posterior tongue regions. The percent of MS patients with identification scores falling below the 5th percentile of controls was 15.07 % for caffeine, 21.9 % for citric acid, 24.66 % for sucrose, and 31.50 % for NaCl. Such scores were inversely correlated with lesion volumes in the temporal, medial frontal, and superior frontal lobes, and with the number of lesions in the left and right superior frontal lobes, right anterior cingulate gyrus, and left parietal operculum. Regardless of the subject group, women outperformed men on the taste measures. These findings indicate that a sizable number of MS patients exhibit taste deficits that are associated with MS-related lesions throughout the brain.

Sniff magnitude test: relationship to odor identification, detection, and memory tests in a clinic population.

Recently a novel measure of olfactory function, the Sniff Magnitude Test (SMT), was developed that relies on changes in inhalation in response to an odor. The relationship of this unique test to that of other olfactory tests has received little investigation. In this study, we assessed, in 132 patients presenting to a chemosensory disorders clinic, the relationship of SMT scores to those from 3 standardized psychophysical tests: the University of Pennsylvania Smell Identification Test (UPSIT), a phenyl ethyl alcohol odor detection threshold test, and a short-term odor memory/discrimination test. SMT scores were roughly related to olfactory dysfunction categories defined for the UPSIT and correlated moderately with the other tests. Malodors (1% and 3% methylthiobutyrate [MTB], 1% ethyl 3-mercaptoproprionate) exhibited stronger correlations than nonmalodors (3% phenyl ethyl alcohol [PEA], 3% amyl acetate, 3% n-butanol) and elicited greater sniff suppression. In a principal component analysis, the SMT measures loaded on components different from those of the other tests, which loaded on a separate component. Anticipatory responses (i.e., smaller sniffs) occurred across trials for the first malodor (1% MTB), but not for the first nonmalodor (3% PEA), that was encountered. These results, along with those of an earlier factor analysis, suggest that sniff magnitude is influenced by odorant quality and intensity, as well as by cognitive factors.