Mesencephalic area measured by transcranial sonography in the differential diagnosis of parkinsonism

Abstract

BackgroundTranscranial B-mode sonography (TCS) has become an important tool in the differential diagnosis of parkinsonism given that current technology enables an adequate assessment of brain structures. In this study we aimed at evaluating the usefulness of midbrain area measured by TCS in the differential diagnosis between Parkinson's Disease (PD) and Progressive Supranuclear Palsy (PSP). MethodsPatients with a diagnosis of PD or PSP according to current clinical criteria were recruited. PSP patients were classified as Richardson's syndrome and PSP-parkinsonism. TCS was performed and the mesencephalic area and third ventricle width were measured offline by an examiner blinded to clinical diagnosis. ResultsTCS was performed in 60 patients (75% PD, 25% PSP). Eight patients (13,3%) had inadequate acoustic window. Patients with PSP had a smaller mesencephalic area (3.58 cm2 vs 5.28 cm2, p < 0.001). A mesencephalic area ≥4.27 cm2 discriminates PD from PSP with a positive predictive value 100%. Patients with PSP also had a higher third ventricle diameter (8.84 mm vs 5.11 mm, p < 0.001). Within the PSP group patients with Richardson's syndrome had a wider third ventricle than patients with PSP-Parkinsonism phenotype (9.57 mm vs 7 mm, p = 0.01), but no differences were found in the mesencephalic area between both phenotypes. ConclusionsMeasurement of the mesencephalic area and the third ventricle width by TCS is a non-invasive, easily accessible technique that is useful in the differential diagnosis between PD and PSP, at least in the late stages of the disease.