A-20The Role of Neuropsychology in Identifying Frontotemporal Dementia Associated with C9ORF72 Genetic Mutation: A Case Study

Abstract

Objective: The C9ORF72 gene mutation is the most common form of familial frontotemporal dementia (FTD). Its clinical presentation is often associated with prominent psychotic symptoms, making it difficult to distinguish from very late onset psychotic disorders (VLOPD). Therefore, the objective of this case study is to highlight the neuropsychological differences that exist between C9ORF72 gene mutation FTD and VLOPD. Method: A 71-year-old female presented with a 2-year history of unusual beliefs and hallucinations. For example, she believed people were trespassing and stealing from her. She heard people knocking on her door and saw people looking through her windows. She had significant apathy and social withdrawal. PET scan results were inconclusive (i.e., atypical for FTD). Referral question asked for differential diagnosis between neuro-cognitive disorders and a psychiatric condition. Results: The cognitive profile revealed prominent deficits in language, frontally-mediated memory systems, and executive functions. Collateral informants endorsed moderate behaviour change including apathy, unusual beliefs, impulsiveness, and stereotypic behaviours. A decline in everyday activities was reported. The breadth and severity of the neuropsychological results were supportive of a neurodegenerative disorder with prominent frontal dysfunction, suggesting a possible FTD as opposed to a psychotic disorder. Genetic testing revealed a C9ORF72 gene mutation. Conclusion: A prominent psychiatric presentation may overshadow cognitive deficits in C9ORF72 gene mutation FTD. Neuropsychological testing plays a key role in distinguishing neurodegenerative disorders from VLOPD. VLOPD is typically associated with milder impairments in memory and executive functioning while C9ORF72 gene mutation FTD is often associated with significant impairments in memory, executive functions, language, and/or visuospatial abilities.