Olfactory bulb involvement in neurodegenerative diseases.
Level 4 - case-series / case-control
Autopsy cohort study embedded within a narrative review
PubMed 24554308 · doi:10.1007/s00401-014-1261-7
What was done
The authors reviewed the neuropathological and pathophysiological mechanisms underlying olfactory dysfunction in neurodegenerative diseases (particularly Alzheimer's disease and synucleinopathies). In addition, they evaluated neuropathological changes in the olfactory bulb and tract in an autopsy cohort of 536 individuals (57.8% female, mean age 81.3 years).
What was found
In the postmortem cohort (n = 536), the severity of hyperphosphorylated tau (HPτ), amyloid-beta (Aβ), and alpha-synuclein (αSyn) pathology in the olfactory bulb correlated and increased significantly (P < 0.001) with increasing neuritic Braak stages, Thal Aβ phases, and cerebral Lewy body pathology, respectively.
Why it matters
Olfactory bulb pathology closely mirrors overall cerebral disease staging in Alzheimer's and Lewy body spectrum disorders. This supports exploring olfactory tissue examination or testing as potential biomarkers for early detection and cohort stratification in neurodegenerative disease trials.
Limits
The primary quantitative data are cross-sectional and postmortem from an elderly cohort (mean age 81.3 years), precluding longitudinal observation of symptom onset versus lesion development. Specific correlation coefficients, effect sizes, and diagnostic accuracy metrics (sensitivity/specificity) were not reported in the abstract.
Cited by
- context For most individuals, the pathology of Parkinson's and Alzheimer's disease begins in the nose with misfolded protein and spreads backwards into the brain.