Degeneration of white matter in the brain, which can be detected using specialized MRI scans, could be an early sign of specific forms of Alzheimer's disease, including so-called early-onset AD, a study suggests.
Researchers in Italy used a specialized MRI technique to assess 53 people with three different types of Alzheimer's and found all of the patients had extensive white matter damage, along with regional gray matter damage.
"Alzheimer's is a gray matter disease," says Federica Agosta, co-author of a study done at the San Raffaele Scientific Institute in Milan and reported in the journal Radiology. "However, white matter damage has a central role in how the disease strikes and progresses."
In the disease, which progressively erodes memory and cognitive skills, abnormal deposits of proteins form amyloid plaques and tau tangles in the brain, leading to a reduction of neurons and slowly causing brain tissue to shrink.
The researchers looked at patients suffering three kinds of Alzheimer's: early-onset AD and two atypical varieties known as focal syndrome because they occur in localized regions of the brain.
The more common late-onset AD usually seen around age 65 or beyond primarily results in gradual memory loss, whereas in the early-onset form of the disease, several areas of the brain are affected, leading to deficits in visuospatial capabilities and executive functioning. Visuospatial deals with visual perception of the spatial relationships of objects.
Patients with focal AD syndrome can exhibit symptoms that include language deficits or visual disturbances.
The researchers took advantage of a specialized form of MRI known as diffusion tensor imaging, which utilizes the movement of water molecules to reveal microstructures in biological tissue.
The technique is exquisitely sensitive to white matter degradation, the researchers noted.
"Our goal was to use DTI to identify similarities and differences in white tract damage across the AD spectrum and in relation to patterns of cortical [gray matter] atrophy," Agosta explains.
There have been suggestions by scientists studying Alzheimer's that the pathology of the disease may be traveling along fibers of white matter in the brain to move from one region of the brain to another.
The new research lends support to that theory, Agosta says, which may offer some help in the early diagnosis of some forms of Alzheimer's.
"In early-onset AD and atypical AD forms, white matter degeneration may be an early marker that precedes gray matter atrophy," she says.
The study findings also emphasize the importance of accurate identification and diagnoses of patients with those atypical forms of AD, she says.
"Because there is not much structural damage in the early stages of focal Alzheimer's disease, there is a risk that patients may be misdiagnosed and excluded from clinical trials," she concludes.
