Transcranial Sonography Findings in Alzheimer's Disease: A New Imaging Biomarker

To validate transcranial sonography (TCS) as a novel imaging tool for the assessment of medial temporal lobe (MTL) atrophy (MTA).

Participants with Alzheimer's disease (AD, n = 30) and age-sex-matched controls (n = 30) underwent TCS and MRI. On TCS, MTL structures (choroidal fissure (CF) and temporal horn (TH)) were measured and combined to create an MTA score in sonography (MTA-S). Furthermore, both THs and the third ventricle were combined to form the ventricle enlargement score in sonography (VES-S). On MRI, the MTL was evaluated by linear measurements, MTA scale and hippocampal volumetry. Validation was performed by comparing imaging methods and the patient group.

Intraclass correlations for CF and TH showed substantial intra/inter-rater reliability (> 0.80). TCS and MRI showed strong to moderate correlation regarding TH (right = 0.88, left = 0.89) and CF (right = 0.70, left = 0.47). MTA-S correlated significantly with the hippocampal volume (right = -0.51, left = -0.47), predicted group membership in logistic regression (Exp(B) right = 3.0, left = 2.7), and could separate AD patients from controls (AUC = 0.93). An MTA-S of 6 mm and 10 mm discriminated MRI MTA scores 0-1 (from 2-4) and MTA score 4 (from 0-3) with 100 % specificity, respectively. VES-S also showed a moderate correlation with the hippocampal volume (r = -0.66) and could differentiate AD patients from controls (AUC = 0.93).

Our results suggest that TCS may be an alternative imaging tool for the assessment of MTL atrophy and ventricular enlargement for patients in whom MRI scanning is not possible. Additionally, TCS offers a practical, patient-friendly and inexpensive option for the screening and follow-up of individuals with AD.