Longitudinal imaging: Change and causality

Purpose of review Longitudinal studies that use MRI scans performed over multiple time-points have been increasingly employed in the study of different neurological disorders, including degenerative dementia, multiple sclerosis, and epilepsy. Recent findings Although it is well established that increased rates of brain atrophy occur in degenerative dementia and multiple sclerosis, recent data have further described these changes and demonstrated that they correlate with both cognitive and functional decline. Advanced voxel-level techniques have also provided detailed descriptions of regional patterns of change, and a few studies have started to investigate changes over multiple MRI enabling the trajectories of brain loss over time to be determined. Researchers have also started to more thoroughly investigate the underlying causes of brain atrophy. Correlations have been observed between rate of brain atrophy and the presence of abnormal protein deposits in the brain in dementia, and the lesion burden in multiple sclerosis. However, longitudinal studies on epilepsy have been inconsistent, with very little recent data. Recent data further support the suggestion that longitudinal MRI provides a good biomarker of disease progression in dementia and multiple sclerosis, though more work needs to be performed to define the role of longitudinal imaging in epilepsy.