Objective: We assessed structural abnormalities of optic radiation (OR) in patients with Parkinson disease (PD) with dementia (PDD) and dementia with lewy bodies (DLB) by using phase difference enhanced imaging (PADRE).

Background: Structural abnormalities in visual association areas including OR have been reported to be associated with visual hallucinations (VH), which occurs frequently in PDD/DLB patients, often in the early stages of the condition.¹ A recently developed, phase-weighted magnetic resonance imaging (MRI) technique “PADRE” can delineate the OR clearly due to the difference in myelin concentration of nerve fiber.² Therefore, the OR changes on PADRE may represent a useful marker to help diagnosis or early identification of patients with PDD/DLB.

Methods: Coronal PADRE images were obtained with a 3D multi-echo spoiled gradient echo sequence at a 3T MRI system. First, two radiologists reviewed OR appearances in healthy subjects (HS) and PDD/DLB patients on PADRE in a non-blinded manner, and deviations from the appearance of the normal OR were recorded as OR abnormalities. Next, based on the OR abnormalities, two reviewers assessed PADRE images from 15 PDD/DLB patients (all PDD/DLB patients with VH), 34 PD (all PD patients without VH) and 18 HS in blinded manner. Kappa values were calculated for inter-observer agreement. Finally, all PD patients were followed for one year after MRI to determine whether the VH would be appeared.

Results: On the PADRE, the two radiologists identified two layers (internal and external sagittal stratum) of the normal OR, and they were able to consensually define the OR as abnormal when the two layers was obscured at the cranial side of the OR. The observer study by the two reviewers demonstrated the sensitivity/specificity of abnormal findings of the OR were 67%/85% (PDD/DLB vs. PD) and 67%/100% (PDD/DLB vs. HS). The κ values for the interobserver variability between two reviewers were 0.81 with excellent interobserver agreement. During a one-year follow-up observation period, the VH was newly appeared in 3 of 5 PD with abnormal OR findings, but no PD patients without abnormal findings of OR showed the VH.

Conclusions: The PDD/DLB patients had the abnormal PADRE findings of the OR, which might be a useful marker to discriminate PDD/DLB from PD on an individual basis and to help early identification of patients with PDD/DLB.

References: 1.           Pizzi SD, Franciotti R, Tartaro A, et al. Structural alteration of the dorsal visual network in DLB patients with visual hallucinations: a cortical thickness MRI study. PloS one 2014;9(1):e86624.

2.           Ide S, Kakeda S, Korogi Y, et al. Delineation of optic radiation and stria of Gennari on high-resolution phase difference enhanced imaging. Academic radiology 2012;19(10):1283-1289.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/parkinsons-disease-with-visual-hallucination-optic-radiation-abnormalities-on-phase-difference-enhanced-imaging-padre/