The relationship between frontotemporal dementias (FTDs) and amyotrophic lateral sclerosis (ALS) is well established and is believed to be more pronounced in those with bulbar onset ALS (B-ALS). This study compared cognitive and behavioral symptoms among persons with B-ALS to those of individuals with nonbulbar phenotypes (NB-ALS).

Outpatient clinic data collected during an initial neuropsychology consultation at an ALS interdisciplinary clinic in an academic medical center was retroactively analyzed. All individuals were diagnosed with ALS by neurologists specializing in movement and neuromuscular disorders based on results of neurological/motor examination, electromyographies, and (when available) genotypic data. Total scores on the short form of the Montreal Cognitive Assessment (MoCA-SF) and scores on the ALS Cognitive Behavioral Screen (ALS-CBS) and ALS CBS Caregiver questionnaire were of focus. 22 B-ALS and 44 NB-ALS individuals were compared on said measures using univariate analyses while controlling for ALS symptoms duration.

B-ALS individuals scored significantly lower on the MoCA-SF (F(2)=3.15, p=0.05, n2=0.13) and the tracking subscale of the ALS-CBS (F(2)=3.50, p=0.04, n2=0.17). The groups were not significantly different on other ALS-CBS measures, including caregiver-rated behavior questionnaire.

Consistent with previous research, this study found lower total scores on a brief screener of global cognition and tasks of tracking requiring cognitive control in those with B-ALS relative to NB-ALS individuals. Interestingly, despite behavioral variant being the most prevalent FTD phenotype, the groups did not differ significantly in terms of caregiver-rated behavioral changes. It is hypothesized that the absence of these differences could reflect effects of gradual loss of speech and functionality that secondarily limit caregivers' abilities to observe behavioral changes concerning for possible behavioral variant FTD. That said this could reflect limitations of the sample and/or study design, and further exploration is therefore needed. Recommendations for future studies of neuropsychological/behavioral variables in B-ALS as well as development of more targeted instruments for use in this population are discussed.