Do patients with motor neuron disease suffer from disorders of taste or smell?

Olfactory or gustatory dysfunction has been described in patients with motor neuron disease. This disorder along with other degenerative diseases has been tentatively linked with the olfactory vector hypothesis according to which a toxic agent may enter the organism via the nasal mucosa. In our study we assessed 26 patients diagnosed as suffering from motor neuron disease at various stages and compared them with 26 matched controls using 'Sniffin' Sticks' for smell and taste strips for taste testing. The two groups did not differ with respect to either ability. The smell test correlated with age, but not with the duration of the disease. We concluded that neither olfaction nor gustation seem to be linked to or influenced by the disease, making the causation by a toxin entering the body via the nasal or oral route rather unlikely as well as a degenerative process encompassing sensory pathways.