Olfaction and Gustation

Although spontaneous complaints about abnormalities in the senses of smell and taste are infrequent (95,96), recent reports have demonstrated that disturbances of olfaction are relatively common. Two studies employing the University of Pennsylvania Smell Identification Test (UPSIT) reported abnormalities in 15% and 38.5%, respectively. In the latter study of 26 patients, Doty et al. (97) found 7.7% with severe impairment, 19.3% moderate, and 11.5% mild. They noted a strong negative correlation between a high UPSIT score (normal olfaction) and the number of lesions within the inferior frontal and temporal lobe regions, which are involved with olfaction.

Other investigators have confirmed the presence of olfactory disturbances (98,99) and also correlated diminished olfaction with lesion load in the olfactory region of the brain (99). Hawkes et al. (100) further demonstrated the involvement of olfactory systems by noting abnormalities to hydrogen sulfide evoked responses (H2S-ER) in MS patients. A group with the disease had statistically increased latency and decreased amplitude in the H2S-ER compared to controls. In general, results on the UPSIT correlated well with the evoked response, although an abnormality on one test did not always indicate an abnormality on the other.

Patients with MS rarely complain of disturbances in taste (101). However, a case has been reported in which hemiageusia was the presenting manifestation of the disorder, preceding other signs of trigeminal and brainstem involvement by more than a week (102). A lesion in the right medulla in the floor of the fourth ventricle was observed on MRI. A previous report had noted the occurrence of hemiageusia in a patient with simultaneous right facial numbness (103).

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