Olfactory Dysfunction Reflects Disease Progression in Japanese Patients with Multiple Sclerosis

Area of Science:

• Neurology
• Neuroscience
• Ophthalmology

Background:

• Olfactory dysfunction is a key clinical sign in multiple sclerosis (MS).
• It is more prevalent and severe in secondary progressive MS (SPMS) compared to relapsing-remitting MS (RRMS).
• Evaluating olfactory deficits can aid in assessing MS disease status.

Purpose of the Study:

• To investigate olfactory dysfunction as a marker for disease status in Japanese patients with MS.
• To compare olfactory identification, cognitive function, and brain atrophy between RRMS and SPMS patients.
• To determine if olfactory dysfunction can differentiate between MS subtypes.

Main Methods:

• Olfactory identification was assessed using the Odor Stick Identification Test for the Japanese (OSIT-J).
• Cognitive function was evaluated using the Wechsler Adult Intelligence Scale (WAIS-III).
• Central brain atrophy was measured by third ventricle width (3rd VW) on MRI.

Main Results:

• SPMS patients exhibited significantly lower OSIT-J scores than RRMS patients.
• The lower limit of normal (LLN) score effectively discriminated between RRMS and SPMS (AUC=0.933).
• SPMS patients showed poorer processing speed and greater 3rd VW compared to RRMS patients.

Conclusions:

• Worsened olfactory dysfunction, cognitive impairment, and brain atrophy are characteristic of SPMS compared to RRMS.
• Olfactory dysfunction serves as a reliable indicator of disease progression in MS.
• This finding can help distinguish SPMS from RRMS, irrespective of ethnicity or cultural background.