Olfactory Dysfunction as an Indicator of Cognitive and Motor Impairment Severity in Huntington’s Disease
Shayan Zadegan1, Madilyn Feik2, Hanna Coco2, Andi Liang3, Frank Ramirez2, Jorge Patino Murillas1, Natalia Pessoa Rocha1, Erin Furr-Stimming1
1Department of Neurology, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 2The University of Texas Health Science Center at Houston (UTHealth), 3Washington University in St Louis, Department of Neurology
Objective:
To explore the association between olfactory dysfunction and Huntington’s disease (HD) symptoms.
Background:
Although olfactory dysfunction in HD gene expansion carriers (HDGECs) has been previously reported, its association with the severity of HD clinical symptomatology is yet to be investigated.
Design/Methods:
Cross-sectional study with 41 HDGECs and 43 age- and gender-matched controls. The olfactory function was assessed using the 12-item Brief Smell Identification Test (BSIT). Participants completed the Unified Huntington's Disease Rating Scale (UHDRS) total motor score (TMS), UHDRS Total Functional Capacity (TFC), and Problem Behaviours Assessment (PBA-s). The cognitive tests included the Montreal Cognitive Assessment (MoCA), Symbol Digit Modalities Test (SDMT), Stroop Color and Word Test (SCWT), and Social Perception-Affect Naming.
Results:
HDGECs presented lower BSIT scores than controls, indicating a poorer ability to discriminate familiar odors (10.17±0.99 versus 7.12±2.19, p<0.0001). HDGECs also performed significantly worse than controls in all cognitive tests. Among HDGECs, higher BSIT scores were significantly associated with better scores in the motor, cognitive, and functional capacity scales: UHDRS-TMS (rs = -0.574; p<0.001), MoCA (rs = 0.538; p=0.0003), SDMT (rs = 0.610; p<0.0001), SCWT interference (rs = 0.502; p=0.0008), social perception (rs = 0.413; p = 0.0073), and TFC (rs = 0.569; p=0.0001). The same associations were not found among controls. We did not find any correlation between olfactory function and PBA-s scores.
Conclusions:
Olfactory dysfunction was associated with worse motor and cognitive symptoms in HDGECs. Our findings suggest that olfactory changes can be used as an indicator of the severity of HD. In the next step, we will investigate the association between olfactory dysfunction and HD progression in a longitudinal study.