Arterial Spin Labeling MRI To Determine Effects of Transcranial Magnetic Stimulation on Cerebral Blood Flow in Patients Diagnosed With Mild Cognitive Impairment

Abstract

Mild cognitive impairment (MCI) is a term used to describe adults who have not crossed the threshold into being diagnosed with progressive dementia, typically Alzheimer’s, but show obvious signs of cognitive impairment1. Recent studies have determined that reduced cerebral blood flow (CBF) has effects on the pathophysiology of Alzheimer Disease (AD)2 and can be one of the early symptoms before any obvious signs of cognitive impairment, but the study of hyper/hypoperfusion patterns in AD are still controversial with many differing opinions and not enough research. Transcranial magnetic stimulation (TMS) has been an important tool used as a therapeutic device for cognitive disorders, like depression, and has begun to be used as a treatment for other cognitive impairments, like MCI or AD. TMS has also been known to have the ability to affect perfusion (increasing or decreasing it) based on the style of TMS and the strength of the applied magnetic field. To determine the effects of transcranial magnetic stimulation on cerebral blood flow, perfusion changes can be detected using arterial spin labeling (ASL), a type of MRI modality. In this study, 11 subjects underwent testing for MCI and were split into groups of those diagnosed as having MCI and those who were diagnosed as cognitively normal (CN). All subjects completed sessions of transcranial magnetic stimulation therapy. ASL MRI images were obtained before and after the sessions and region of interest statistical analyses were carried out to determine if TMS affects CBF differently in patients diagnosed with MCI. Subjects with MCI showed statistically significant differences in CBF in certain regions compared to the CN group and suggest that TMS may alter CBF in areas affected by hypoperfusion in patients diagnosed with MCI and AD.