Editors' Note: Phenotypic Variability in ALS-FTD and Effect on Survival

Dr. Ahmed et al. examined initial presentations and cognitive and behavioral profiles in 59 patients with amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD) and 39 patients with behavioral variant frontotemporal dementia (bvFTD) and compared their MRI brain atrophy patterns and survival trajectories. They found that initial motor presentation in ALS-FTD was associated with shorter survival than those with a cognitive presentation, despite similar overall cognitive deficits. Patients with ALS-FTD also showed reduced emotional processing as well as greater motor cortex and dorsal lateral prefrontal cortex atrophy than those with bvFTD, with motor cortex atrophy, in turn, associated with a 1.5-fold reduction in survival. In response, Dr. Abe cites a case report of a patient with ALS and dementia who presented with disturbances in emotion processing and behavior, with such early behavioral changes also noted in other studies of ALS-FTD. Dr. Abe suggests that functional neuroimaging studies may help further elucidate pathophysiologic processes in these cases, citing a case of a patient with ALS-FTD and prominent bulbar palsy and memory loss but preserved personality who had hypoperfusion in the central and prefrontal cortex, but not in the dorsolateral prefrontal cortex. Responding to these comments, the authors agree that ALS-FTD can present with cognitive and behavioral changes. They note that their study results suggest that survival in ALS-FTD may be mediated by motor function and other critical physiologic aspects. They also note that patients with ALS-FTD and an initial cognitive presentation had more prominent language changes, but contrary to the conventional perception of bvFTD as having more deficits in emotional processing, patients with ALS-FTD had greater deficits in this domain in their study. They agree that functional neuroimaging, in combination with clinical, structural, and pathologic evaluation, can help improve our understanding of these diseases. This exchange demonstrates how modern phenotypic studies are challenging previous assumptions about distinctions between different subtypes of FTD and ALS-FTD and elucidating new discoveries about these conditions.

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