Alzheimer's disease, the most common form of dementia, affects 70% of the 50 million dementia cases worldwide. However, there could be more patients who go unreported, according to María del Carmen Cárdenas Aguayo, head of the Laboratory of Cellular Reprogramming at the Faculty of Medicine of the National Autonomous University of Mexico.
Researchers have observed that some changes in the brain can manifest themselves in the retina, making it a potential region to search for early signs of this disease. Although still in the experimental phase, diagnostic methods for Alzheimer's are being developed based on the detection of amyloid beta or hyperphosphorylated tau at the UNAM laboratory.
Volunteers who report a subjective complaint of memory loss and cognitive capacity undergo a simple test and have blood and nasal exfoliation samples taken. The olfactory neuroepithelium is another potential source of neuronal cells useful for diagnosing Alzheimer's, as amyloid beta and hyperphosphorylated tau proteins can be detected.
Although retinal imaging can detect accumulations of amyloid beta, the diagnosis of accumulations of hyperphosphorylated tau by this organ has not yet been developed. However, the presence of both types of lesions (neurofibrillary tangles and neuritic plaques) confirms the diagnosis of Alzheimer's disease.
Early diagnosis is necessary for proper treatment, and retinal diagnosis seems to be very attractive for identifying the disease in its early stages. However, it would have to be combined with other imaging markers or fluids, as well as follow-up cognitive testing every three to six months, to monitor any cognitive deterioration correlated with Alzheimer's disease.
Dr. Cárdenas Aguayo emphasizes that cognitive reserve must be taken into account in determining the speed of the disease's development. The neural connections generated throughout one's life can cushion the damage caused by Alzheimer's disease, which is why early diagnosis is crucial.
The UNAM researcher stresses the importance of having numerous diagnostic tools, including brain imaging by magnetic resonance or positron emission tomography, retinal diagnosis, and tests to detect pathology markers in fluids such as plasma or cerebrospinal fluid.
Hyperphosphorylated tau is essential for the functioning of neurons, and pathological alterations of this protein correlate with cognitive impairment. Aggregates of hyperphosphorylated tau hinder the normal functioning of neurons, leading to a degeneration in which neurons die, synaptic connections are lost, and forgetfulness begins. The disease starts with short-term memory loss due to damage to the hippocampus region, which is responsible for learning and short-term memory. From there, the damage spreads to the cortex, leading to the loss of long-term memory.