BOSTON – Brain amyloid imaging may help clinicians to rule Alzheimer’s disease in or out and spare patients with other forms of dementia from the possibly harmful effects of antiamyloid therapies, a small study has shown.
In a case series of 20 patients who were given clinical diagnoses that included frontotemporal dementia, Alzheimer’s disease (AD), Parkinson’s disease, and mild cognitive impairment, PET scanning with the radiotracer florbetapir 18F (Amyvid) was positive and consistent in scans of patients with diagnoses of AD or amnestic mild cognitive impairment, and was negative in scans of patients with Parkinson’s disease, delayed post-traumatic cognitive impairment, depression, and normal cognition.
Dr. Effie Mitsis
One of the patients was a retired National Football League player with a history of multiple concussions. Although neuropsychologists and neurologists disagreed on a diagnosis of possible AD, florbetapir 18F PET imaging helped them confirm a diagnosis of delayed post-traumatic cognitive impairment without amyloidosis and with possible chronic traumatic encephalopathy, said Effie Mitsis, Ph.D., of the department of psychiatry at Mount Sinai School of Medicine in New York.
"If this guy came to our Alzheimer’s disease research center without the scan, undoubtedly one of the neurologists would have put him on an antiamyloid agent and put him into a clinical trial," she said in an interview.
Florbetapir is a radioligand that attaches to amyloid plaques in the brain. Dr. Mitsis and her colleagues use the agent as part of a comprehensive clinical dementia evaluation.
In the series she reported, florbetapir PET scans were negative in all of three patients diagnosed with frontotemporal dementia and primary progressive aphasia, and in two of three patients with behavioral variant frontotemporal dementia.
In one patient diagnosed with Parkinson’s disease and AD, the scans were positive, and in another diagnosed with Parkinson’s disease and depression, the scans were negative, the investigators found.
Of four patients with a diagnosis of amnestic mild cognitive impairment and five with a diagnosis of AD alone, all scans were positive. In contrast, in the one patient with a diagnosis of depression but no neurodegenerative disease, the scans were negative.
Dazed and confused after games
Scans were negative in two patients with normal cognition, and in the former NFL player.
He had retired from the game after a 10-year professional career, during which time he had multiple concussions.
"By 12 hours post game, he was at times unable to name which team he had just played against. He does not recall loss of consciousness, but was dazed and confused sometimes up to a full day afterward. On several occasions, the player had difficulty finding his way home after a game," Dr. Mitsis reported in a poster presentation at the Alzheimer’s Association International Conference 2013.
A designated NFL Neurological Care Program team consisting of a neurologist, a neurologic psychiatrist, a neuropsychologist, neuroradiologists, and nuclear medicine physicians had evaluated him with validated cognitive and memory instruments, and determined that he had impairments in information-processing speed, verbal comprehension, and immediate and delayed word recall, but still had intellectual function and learning ability.
Dr. Mitsis and another neuropsychologist independently reviewed the test results and agreed on the inclusion of possible AD in the diagnosis, a finding that was opposed by all but one member of the original evaluation team.
With florbetapir PET scanning, however, they were able to exclude a diagnosis of cerebral amyloidosis, thereby ruling out AD, Dr. Mitsis said.
The research was supported by grants from the U.S. Department of Veterans Affairs. Dr. Mitsis reported having no relevant financial disclosures.