Chemosensory dysfunction in neurodegenerative diseases.

Area of Science:

• Neuroscience
• Neurology
• Otolaryngology

Background:

• Neurodegenerative diseases frequently manifest with impaired smell function, varying in severity across conditions.
• Olfactory testing offers a unique diagnostic approach, probing brain regions beyond standard physical examinations.
• Smell dysfunction can indicate preclinical stages of neurodegenerative diseases, prompting its inclusion in diagnostic criteria.

Purpose of the Study:

• To review the current understanding of smell and taste disorders in neurodegenerative diseases.
• To explore the pathological mechanisms underlying these sensory deficits.
• To highlight the diagnostic potential of olfactory testing in early disease detection.

Main Methods:

• Literature review of studies on olfactory and gustatory dysfunction in neurodegenerative conditions.
• Analysis of research investigating the pathological underpinnings of smell and taste alterations.
• Examination of diagnostic guidelines and recommendations incorporating olfactory testing.

Main Results:

• Olfactory dysfunction is a common feature in Alzheimer's disease (AD) and Parkinson's disease (PD), aiding in their differentiation from other disorders.
• Formal olfactory testing can identify individuals in the preclinical stages of neurodegenerative diseases.
• Taste impairment is also observed but has received less research attention compared to smell dysfunction.

Conclusions:

• Olfactory testing is a valuable tool for the early diagnosis and differential diagnosis of neurodegenerative diseases.
• The American Academy of Neurology and Movement Disorder Society recognize smell dysfunction as a key diagnostic criterion for PD.
• Further research is needed to fully understand the role of taste dysfunction and the pathological basis of sensory changes in neurodegeneration.