Exploring Olfactory Function and Its Relation with Behavioral and Cognitive Impairment in Amyotrophic Lateral...

Behavioral and cognitive impairment are common in amyotrophic lateral sclerosis (ALS) and represent a continuum with frontotemporal dementia (FTD). Olfactory dysfunction has been described in a subset of ALS patients and might be associated with frontotemporal and insular cortex dysfunction.

To evaluate olfaction dysfunction in ALS patients and its relationship with either cognition or behavioral impairment.

28 consecutive ALS patients underwent an extensive cognitive and behavioral battery and were classified as patients with normal cognition (ALS-N, n = 11) or with part of the ALS-FTD spectrum (n = 17), including either cognitive or behavioral impairment or dementia. Odor verbal and visual identification and discrimination were investigated in patients and age-matched controls using a test adapted from the Sniffin' Sticks.

Olfactory function was significantly different between ALS-FTD spectrum patients and controls (p < 0.001) and inversely correlated with behavioral and cognitive performance. The 10-point cutoff distinguished ALS-N from ALS-FTD spectrum patients with a sensitivity and specificity of 71 and 100%, respectively.

Hyposmia is common in a subset of ALS patients and strongly associated with behavioral and cognitive impairment. Olfactory testing may represent an early screening tool in order to identify ALS subjects with cognitive/behavioral dysfunction. Further studies in larger series are mandatory in order to better investigate clinical and pathological aspects in this group of patients.