The Phenotype of the C9ORF72 Expansion Carriers According to Revised Criteria for bvFTD.

BACKGROUND: The C9ORF72 expansion is one of the most common genetic etiologies observed with behavioural variant frontotemporal dementia (bvFTD). Revised diagnostic criteria for bvFTD (FTDC) were recently introduced but only a few studies have evaluated the accuracy of these criteria.

OBJECTIVE: The objective of the study was to evaluate the applicability of the FTDC criteria and assess the psychiatric history of these patients.

METHODS: The study examined 36 patients carrying the C9ORF72 expansion and suffering from bvFTD (N = 32) or from bvFTD with motor neuron disease (bvFTD-MND, N = 4). Neuropsychological, neuropsychiatric, structural brain imaging and PET/SPECT data were evaluated.

RESULTS: We found 0.75 sensitivity (SD 0.44, 95%CI 0.57-0.87) for possible bvFTD and 0.64 (SD 0.44, 95%CI 0.57-0.87) for probable bvFTD. The sensitivity was even higher in bvFTD patients without MND, i.e., 0.81 for possible bvFTD and 0.69 for probable bvFTD. PET/SPECT was normal in 17.6% of scanned patients with bvFTD. A history of psychiatric symptoms (psychotic and/or mood symptoms) was detected in 61% of cases.

CONCLUSIONS: The FTDC possible and probable bvFTD criteria seem to identify the majority of the C9ORF72 expansion carriers with bvFTD, even though they exhibit only a limited number of behavioral criteria but a significant amount of psychiatric symptoms. The presence of a normal PET/SPECT does not exclude the possibility the C9ORF72 associated bvFTD.