56. BACK TO THE FUTURE: VISUAL HALLUCINATIONS CAPTURED ON FDG-PET IN ADVANCE OF GROSS COGNITIVE IMPAIRMENT: A CASE FOR ETIOPATHOLOGICAL REDEFINITION OF ALZHEIMER'S DISEASE.

Introduction

Neurobiological studies to date suggest that psychosis in AD and related dementias may be associated with distinct imaging, genetic, neuropathological, and CSF biomarkers. Notably, most of the neurobiological studies to date have focused on patients with established dementia, given that psychotic symptoms are much rarer in prodromal states and may be confused with primary psychiatric pathology. Further study of psychosis-associated biomarkers in patients with prodromal conditions is clearly required.

Methods

We describe the case of a previously healthy woman in her middle 70s with new-onset and prominent visual hallucinations referred for neuropsychiatric evaluation after an extensive medical work-up by neurology to rule out organic causes. A thorough psychiatric, neurological, and cognitive evaluation was conducted. We conducted an FDG-PET evaluation to further elucidate the underlying pathophysiology.

Results

We report for the first time in the literature a case of the Phantom Boarder Phenomenon (PB), in which animals (snakes) and insects (spiders) have entered or are living in the patient's home despite evidence to the contrary. The patient experiences fear, anxiety, social isolation, living alone with no interpersonal relationships, and personal loss. Extensive medical, neurological, ophthalmological, and psychiatric workup and evaluation was completely normal, except for the FDG-PET findings that demonstrated early signs of synaptic dysfunction on bilateral temporal lobes.

Conclusions

Our case report supports the notion found in other studies that identified the temporal lobes as the neurobiological substrate of positive BPSD and FDG-PET as a potential instrument to predict their development.