Neuropsychological correlates of visual hallucinatory phenomena in Lewy body disease

Visual hallucinations (VH) ranging from minor to complex, are the most common psychiatric feature of Lewy Body Disease (LBD). Despite their high prevalence and poor prognostic implications instigating extensive research, the precise mechanisms underlying VH remain unclear. Cognitive impairment (CI) is a risk factor and a consistent correlate of VH in LBD. To help shed light on their underlying mechanisms, this study investigates the pattern of CI across the spectrum of VH in LBD.

30 LBD patients with minor VH (MVH), 13 with complex VH (CVH) and 32 without VH were retrospectively compared on the domains of higher-order visual processing, memory, language and executive functioning. The VH groups were further stratified to investigate whether phenomenological subtypes have distinct cognitive correlates.

LBD patients with CVH were impaired on the visuo-spatial and executive functioning domains relative to controls. LBD patients with MVH were also impaired on the visuo-spatial domain. No differences emerged in cognitive domains affected between patient groups endorsing specific hallucinatory phenomena.

A pattern of CI indicating fronto-subcortical dysfunction in combination with posterior cortical involvement is implicated in the genesis of CVH. Moreover, this posterior cortical dysfunction may precede the occurrence of CVH as indicated by selective visuo-spatial deficits in LBD patients with MVH.