Frontal lobe dysfunction is associated with reduced DAT-SPECT accumulation in Lewy body disease

Area of Science:

• Neurology
• Neuroimaging
• Neurodegeneration

Background:

• Lewy body disease (LBD) is characterized by early olfactory and cognitive dysfunction preceding motor symptoms.
• Dopamine transporter (DAT) imaging via ¹²³I-ioflupane SPECT shows correlations with these dysfunctions in LBD.
• Decreased frontal lobe cerebral blood flow (CBF) is hypothesized to be involved in these relationships, potentially aiding assessment of LBD progression.

Purpose of the Study:

• To investigate the relationship between olfactory and frontal lobe dysfunction and dopamine transporter (DAT) availability in Lewy body disease (LBD).
• To explore the role of reduced cerebral blood flow (CBF) in the frontal lobe on these correlations.
• To elucidate the pathological progression of LBD, focusing on the sequence of olfactory, striatal, and frontal lobe dysfunction.

Main Methods:

• Retrospective analysis of 139 de novo Lewy body disease (LBD) patients.
• Olfactory function assessed using the Odor Stick Identification Test for Japanese (OSIT-J).
• Frontal lobe function evaluated with the Frontal Assessment Battery (FAB).
• ¹²³I-ioflupane SPECT imaging used to assess dopamine transporter (DAT) availability (specific binding ratio - SBR).
• Patients categorized based on reduced (n=28) or normal (n=56) frontal lobe CBF.

Main Results:

• Significant correlations were found between OSIT-J and FAB scores.
• Odor Stick Identification Test for Japanese (OSIT-J) scores correlated significantly with the specific binding ratio (SBR) in both reduced and normal CBF groups.
• The specific binding ratio (SBR) correlated with Frontal Assessment Battery (FAB) scores only in patients with reduced frontal lobe CBF.

Conclusions:

• Frontal lobe and striatal dysfunction in Lewy body disease (LBD) patients are linked only after a decline in cerebral blood flow (CBF).
• A temporal sequence in LBD pathology is suggested: olfactory dysfunction manifests first, followed by striatal, and then frontal lobe dysfunction.
• ¹²³I-ioflupane SPECT, alongside olfactory and cognitive tests, may help track LBD progression.