Arterial spin labeling (ASL) MRI can detect signs of cognitive decline in the brain even before symptoms appear, according to a new study published online in the journal Radiology. The technique has the potential to serve as a biomarker in very early diagnosis of preclinical dementia.
Researchers studied the MRI technique, which doesn’t require injection of a contrast agent. ASL measures brain perfusion, or penetration of blood into the tissue. The study group included 148 healthy elderly participants and 65 people with mild cognitive impairment (MCI). The participants underwent brain MRI and a neuropsychological assessment, a common battery of tests used to determine cognitive ability.
Of the 148 healthy individuals, 75 remained stable, while 73 deteriorated cognitively at 18 months clinical follow-up. Those who deteriorated had shown reduced perfusion at their baseline ASL MRI exams, particularly in the posterior cingulate cortex, an area in the middle of the brain that is associated with the default mode network, the neural network that is active when the brain is not concentrating on a specific task. Declines in this network are seen in MCI patients and are more pronounced in those with Alzheimer’s disease.
The pattern of reduced perfusion in the brains of healthy individuals who went on to develop cognitive deficits was similar to that of patients with MCI.
“There is a known close link between neural activity and brain perfusion in the posterior cingulate cortex,” says study author Sven Haller, MD, from the University of Geneva in Switzerland. “Less perfusion indicates decreased neural activity.”
The results suggest that individuals with decreased perfusion detected with ASL MRI may temporarily maintain their cognitive status through the mobilization of their cognitive reserve, but will eventually develop subtle cognitive deficits.
Previous research done with PET, the current gold standard for brain metabolism imaging, found that patients with Alzheimer’s disease had reduced metabolism in the same area of the brain where the perfusion abnormalities were found using ASL MRI. This points to a close link between brain metabolism and perfusion, according to Haller.
ASL MRI has potential as a standalone test or as an adjunct to PET for dementia screening, Haller says. While PET can identify markers of Alzheimer’s disease in the brain and cerebrospinal fluid, it exposes the patient to radiation. ASL does not expose the patient to radiation and is easy to perform in routine clinical settings. The results also support a role for ASL MRI as an alternative to neuropsychological testing.
The researchers plan to perform follow-up studies on the patient group to learn more about ASL and long-term cognitive changes.
— SOURCE: RSNA