Loss of smell (hyposmia or anosmia) may be a sign of a neurodegenerative disease.


Loss of smell may be associated with:

(1) Parkinson's disease

(2) Alzheimer's disease

(3) other dementias


A feature of hyposmia in a neurodegenerative disease is that the patient is either unaware of the loss or significantly underestimates its severity.


Screening for loss of smell in a general population has limited utility, but it may be helpful in a high-risk population.


The diagnosis of Parkinson's disease should be questioned in a patient with normal smell unless the patient is a female with tremor-dominant disease (Hawkes, 2006).


Anosmia is atypical for a patient with progressive suprnuclear palsy or corticobasal degeneration. Its presence should prompt a review of the diagnosis (Hawkes, 2006)>


Exclusion of other explanations such as chronic sinusitis or head trauma.


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