Prognosis of Patients with Behavioral Variant Frontotemporal Dementia Who have Focal Versus Diffuse Frontal Atrophy

Only a few studies have investigated the relationship between different subtypes and disease progression or prognosis in patients with behavioral variant frontotemporal dementia (bvFTD). Since a localized injury often produces more focal signs than a diffuse injury, we hypothesized that the clinical characteristics differ between patients with bvFTD who show diffuse frontal lobe atrophy (D-type) on axial magnetic resonance imaging (MRI) scans versus those with focal or circumscribed frontal lobe atrophy (F-type).

In total, 94 MRI scans (74 scans from bvFTD and 20 scans from age-matched normal controls) were classified into 35 D- and 39 F-type bvFTD cases based on an axial MRI visual rating scale. We compared baseline clinical characteristics, progression in motor and cognitive symptoms, and survival times between D- and F-types. Survival analyses were performed for 62 of the 74 patients.

While D-type performed better on neuropsychological tests than F-type at baseline, D-type had higher baseline scores on the Unified Parkinson's Disease Rating Scale (UPDRS) Part III. Evaluations of motor progression showed that the disease duration with motor symptoms was shorter in D-type than F-type. Moreover, the survival time was shorter in D-type (6.9 years) than F-type (9.4 years). Cox regression analyses revealed that a high UPDRS Part III score at baseline contributed to an increased risk of mortality, regardless of the pattern of atrophy.

The prognosis is worse for D-type than for those with F-type. Shorter survival in D-type may be associated with the earlier appearance of motor symptoms.