A study published in the journal Neurology sets out to describe observable attributes and patterns in motor signs (known as motor sign phenotypes) associated with genetic FTD, and to investigate their association with different patterns of brain atrophy.  

The study’s authors note that while extensive literature details the behavioral and language-based features of genetic FTD, detailed characterization of motor disorders is lacking outside of sporadic cases or case studies. The authors looked to address this by describing the motor phenotypes of genetic FTD.  

Researchers enrolled 322 participants through the Genetic Frontotemporal Dementia Initiative (GENFI) who either carried gene variations associated with the development of FTD; c9orf72, GRN, and MAPT. Participants at risk of developing a gene variation were also enrolled if they had a first-degree relative who was a confirmed carrier.  

Members of the cohort had their motor impairments assessed and rated in severity, and MRI data was collected from 286 members.  

Using statistical analysis to compare data, the study revealed the presence of motor sign clusters in genetic FTD.  

Researchers made several intriguing findings, such as motor signs associated with corticobasal syndrome (CBS) being more frequent in C9orf72 carriers compared to GRN carriers, despite earlier studies associating them with the latter gene. Additionally, symptoms of amyotrophic lateral sclerosis (ALS) with FTD were more frequent in C9orf72 carriers and was rarely detected in GRN and MAPT carriers.  

The study found that the motor phenotypes were correlated with specific patterns of atrophy in the brain. Severity appeared to increase over time, though the rate of increase also depended on the affected gene. 

The study was limited by a lack of control groups with people not carrying a gene variation associated with FTD. However, the study’s findings open new avenues for research on disease-modifying treatments and other interventions.  

Disruption to motor skills is a common feature of FTD disorders like CBD and ALS with FTD. For more on CBD, read the winter 2021 edition of Partners in FTD Care, and for more on ALS with FTD, watch this AFTD Educational Webinar.