Olfactory dysfunction is common in multiple sclerosis (MS). Olfactory bulb and tract pathology in MS and other demyelinating disease remains unexplored. A human autopsy cohort of pathologically confirmed cases encompassing the spectrum of demyelinating disease (MS; n=17), neuromyelitis optica (NMO); n=3), and acute disseminated encephalomyelitis (ADEM); n=7)) was compared to neuroinflammatory (herpes simplex virus encephalitis (HSE); n=3), neurodegenerative (Alzheimer’s disease (AD); n=4), and non-neurologic (n=8) controls. For each case, olfactory bulbs and/or tracts were stained for myelin, axons, and inflammation. Inferofrontal cortex and hippocampus were stained for myelin in a subset of MS and ADEM cases. Olfactory bulb/tract demyelination was frequent in all demyelinating diseases (MS 12/17 (70.6%); ADEM 3/7 (42.9%); NMO 2/3 (66.7%)) but was absent in HSE, AD, and non-neurologic controls. Inflammation was greater in the demyelinating diseases compared to non-neurologic controls. Olfactory bulb/tract axonal loss was most severe in MS where it correlated significantly with the extent of demyelination (r=0.610, P=0.009) and parenchymal inflammation (r=0.681, P=0.003). The extent of olfactory bulb/tract demyelination correlated with that found in the subjacent adjacent inferofrontal cortex but not hippocampus. We provide unequivocal evidence that olfactory bulb/tract demyelination is frequent, can occur early and be highly inflammatory, and is specific to demyelinating disease.
The olfactory system is your concerned with your sense of smell and in rodents it contains stem cells capable of remyelination (olfactory ensheathing cells) In this study they looked MSers and non MSer and found demyelination was common in parts of the brain associated with sense of smell. There was also nerve loss too.This effect was common and was found in 70%of people. How’s your sense of smell. ProfHawkes is our smelly neuro and carries around “scratch and sniff” cards in his pocket…how weird is that?
DeLuca GC, Joseph A, George J, Yates RL, Hamard M, Hofer M, Esiri MM. Olfactory Pathology in Central Nervous System Demyelinating Diseases. Brain Pathol. 2014 Sep. doi: 10.1111/bpa.12209. [Epub ahead of print]