Optic radiation atrophy in Lewy body disease with visual hallucination on phase difference enhanced magnetic resonance images

Parkinson disease psychosis: from phenomenology to neurobiological mechanisms

Parkinson disease (PD) psychosis (PDP) is a spectrum of illusions, hallucinations and delusions that are associated with PD throughout its disease course. Psychotic phenomena can manifest from the earliest stages of PD and might follow a continuum from minor hallucinations to structured hallucinations and delusions. Initially, PDP was considered to be a complication associated with dopaminergic drug use. However, subsequent research has provided evidence that PDP arises from the progression of brain alterations caused by PD itself, coupled with the use of dopaminergic drugs. The combined dysfunction of attentional control systems, sensory processing, limbic structures, the default mode network and thalamocortical connections provides a conceptual framework to explain how new incoming stimuli are incorrectly categorized, and how aberrant hierarchical predictive processing can produce false percepts that intrude into the stream of consciousness. The past decade has seen the publication of new data on the phenomenology and neurobiological basis of PDP from the initial stages of the disease, as well as the neurotransmitter systems involved in PDP initiation and progression. In this Review, we discuss the latest clinical, neuroimaging and neurochemical evidence that could aid early identification of psychotic phenomena in PD and inform the discovery of new therapeutic targets and strategies.

Superior cerebellar peduncle atrophy of progressive supranuclear palsy on phase difference enhanced imaging: a comparison with Parkinson's disease

PURPOSE

Phase difference enhanced (PADRE) imaging can enhance myelin density and delineate the superior cerebellar peduncle (SCP). We aimed to determine if SCP atrophy was distinguishable on PADRE imaging and evaluate its diagnostic performance compared with previous MRI progressive supranuclear palsy (PSP) findings.

METHODS

Two reviewers measured the SCP widths on PADRE in 20 PSP and 31 Parkinson's disease (PD) patients. The SCP and middle cerebellar peduncle (MCP) widths and the pons and midbrain areas were measured on 3D-T1WI, and the ratio of the area of the pons to the area of the midbrain, the MCP/SCP ratio, and the magnetic resonance parkinsonism index (MRPI) were calculated. We used the Steel-Dwass test to compare PSP, PD, and HS, and receiver operating characteristic curve (ROC) analyses to assess the sensitivity and specificity for diagnosing PSP from PD. A comparison of ROC curves was performed between the SCP on PADRE and these 3D-T1WI parameters.

RESULTS

In radiologist 1, the SCP on PADRE in PSP (1.1 ± 0.3 mm) was significantly smaller than those in PD (2.4 ± 0.4 mm) (P < 0.001); the area under the curve (AUC) was 0.97. At a 1.75-mm cutoff value, the diagnostic sensitivity and specificity for differentiating PSP from PD were 93.5% and 100%, respectively. The AUC of the SCP on PADRE was significantly higher than the 3D-T1WI parameters (the SCP, MCP, pons area, MCP/SCP ratio, and MRPI).

CONCLUSION

Assessing SCP with PADRE imaging may yield high diagnostic accuracy for discriminating PSP from PD.