Objective: To study the use of transcranial sonography (TCS) in discriminating between patients with dementia with Lewy bodies (DLB) and Parkinson's disease with dementia (PDD).
Methods: Fourteen patients with DLB, 31 with PDD and 73 with PD without dementia (PDnD) were studied with TCS.
Results: All assessable patients with DLB, 97% with PDD, and 94% with PDnD showed at least unilateral hyperechogenicity of substantia nigra (SN). However, bilateral marked SN hyperechogenicity was present in 80% of DLB patients but only in one third of PDD and PDnD patients, and was associated with younger age at disease onset in PD but not in DLB. An asymmetry index > or = 1.15 of bilateral SN echogenic sizes, estimated by division of larger size by smaller size, was found in 69% of PDD patients but only 20% of DLB patients. Combination of SN echogenic sizes, asymmetry indices and onset age discriminated PDD from DLB with a sensitivity of 96%, a specificity of 80% and a positive predictive value of 93%. TCS of brainstem raphe, thalami, lenticular nuclei, caudate nuclei and ventricle widths did not discriminate between DLB and PDD. Compared with PDnD patients, DLB and PDD patients exhibited significantly larger widths of third ventricle and of frontal horns. In PDD patients, scores on the Unified Parkinson's Disease Rating Scale correlated with widths of third ventricle and of frontal horns.
Conclusions: SN hyperechogenicity is typical for PDD and DLB. However, size, asymmetry and relation of SN hyperechogenicity to age at disease onset discriminate PDD from DLB.