Abstract
Objective To determine the rate of hallucinations across non-Parkinson’s neurodegenerative disorders including Frontotemporal Dementia and explore the underlying cognitive and neural basis for the development of these symptoms
Methods Patients were recruited (n=429) and assessed over a 10-year period at the FRONTIER FTD multidisciplinary research clinic. Patients were assessed at their first visit by means of a clinical interview, a battery of neuropsychological tests and MRI. Data was analysed according to 3 tiers; 1) rate of hallucinations across neurodegenerative disorders; 2) the relationship between neural structures, cognition, behaviour and hallucinations and 3) the impact of the C9orf72 expansion on expression of hallucinations.
Results Tier 1: The majority of cases of hallucinations occurred in patients with bvFTD (22%), Alzheimer’s disease(13%), LPA and Corticobasal syndrome (11%). Rate of hallucinations were low for posterior cortical atrophy (9%), Primary progressive aphasia (PPA) including left and right Semantic Dementia (SD; 6%), PPA-non-fluent variant and Progressive supranuclear palsy (0%; p<0.006). Tier 2: Attentional measures differed between groups (all p<0.02) with hallucinators making more frequent attentional and processing speed errors while structural changes affected regions of attentional networks centred on the prefrontal cortex (p<0.001). Tier 3: Attentional processes were also implicated in C9orf72 carriers with hallucinations as well as visual functions including memory and spatial abilities (p<0.05) while structural changes were focused on the thalamus (p<0.001).
Conclusion Hallucinations are present across neurodegenerative syndromes and highest in FTD. Attentional subsystems and networks are implicated in the generation of these features that dissociate across C9orf72 and sporadic bvFTD.
