Anosmia in dementia is associated with Lewy bodies rather than Alzheimer's pathology

Abstract

Consensus clinical criteria for dementia with Lewy bodies had a sensitivity of 64% and specificity of 89%. In the absence of definite Alzheimer's disease, the criteria had sensitivity of 100%. In patients with definite Alzheimer's disease, anosmia was slightly more sensitive (55%) than the consensus criteria (33%). However, the addition of anosmia to the consensus criteria did not improve their overall performance. Conclusion-Dementia with Lewy bodies is associated with impaired odour detection. Misdiagnosis may have accounted for some previous reports of impaired odour detection in Alzheimer's disease. Simple but more sensitive tests of anosmia are required if they are to be clinically useful in identifying patients with dementia with Lewy bodies. (J Neurol Neurosurg Psychiatry 2001;70:739-743)

Olfactory Dysfunction in Parkinson’s Disease

“…While olfactory dysfunction has been demonstrated in AD, patients with Lewy body dementia have even greater impairments in olfaction, lending significance to the role of Lewy pathology in olfactory dysfunction [42][43][44] . Based on this assumption, it would be expected that nondegenerative causes of parkinsonism have intact olfaction, as is the case in vascular parkinsonism [45] and MPTP-induced parkinsonism [46] .…”

Premotor Symptoms and Early Diagnosis of Parkinson's Disease

“…Cross-sectional studies have clearly shown that hyposmia is a highly sensitive finding in PD, but it is not specific. Olfaction is also impaired in dementia with Lewy bodies (DLB) [11,12], pure autonomic failure [13], and amyotrophic lateral sclerosis, with mixed results found for Alzheimer's disease and multiple system atrophy [11,12]. Therefore, this nonmotor finding may be used as a premotor test to identify an at-risk group for PD, but it is certainly not diagnostic.…”

Combinations of Markers Provide Clues to the Underlying Neurodegenerative Disorder in REM Sleep Behavior Disorder

“…In dementia patients, neuropathologic studies reported neuronal alterations in several subcortical structures such as the olfactory tract/bulb, anterior olfactory nucleus, orbito-frontal cortex, hippocampus, and amygdala in the olfactory system (Hubbard et al, 2007). Olfactory abnormalities have been reported in Alzheimer's disease (AD), but anosmia appears to be common in dementia with Lewy bodies (DLB) but not in pure AD (McShane et al, 2001). A Lewy body variant of AD had an increased frequency of anosmia compared with "pure" AD (Olichney et al, 2005).…”