Neural Correlates of Schizotypal Personality Disorder: A Systematic Review of Neuroimaging and EEG Studies

Background: Schizotypal Personality Disorder (SPD) is a cluster A personality disorder affecting 1.0% of the general population, characterised by disturbances in cognition and reality testing dimensions, affected regulation, and interpersonal function. SPD shares similar but attenuated phenomenological, genetic, and neurobiological abnormalities with Schizophrenia (SCZ) and is described as part of schizophrenia spectrum disorders. Objective: The aim of this work was to identify major neural correlates of SPD. Methods: This is a systematic review conducted according to PRISMA statement. The protocol was prospectively registered in PROSPERO -International prospective register of systematic reviews. The review was performed to summarise the most comprehensive and updated evidence on functional neuroimaging and neurophysiology findings obtained through different techniques (DW-MRI, DTI, PET, SPECT, fMRI, MRS, EEG) in individuals with SPD. Results: Of the 52 studies included in this review, 9 were on DW-MRI and DTI, 11 were on PET and SPECT, 11 were on fMRI and MRS, and 21 were on EEG. It was complex to synthesise all the functional abnormalities found in a single, unified, pathogenetic pathway, but a common theme emerged: the dysfunction of brain circuits including striatal, frontal, temporal, limbic regions (and their networks) together with a dysregulation along the dopaminergic pathways. Conclusion: Brain abnormalities in SPD are similar, but less marked, than those found in SCZ. Furthermore, different patterns of functional abnormalities in SPD and SCZ have been found, confirming the previous literature on the 'presence' of possible compensatory factors, protecting individuals with SPD from frank psychosis and providing diagnostic specificity.