Tau Brain Scans

The deadly disease Alzheimer's takes a terrible toll on not just memories but also lives of millions year on year. Although doctors use checklists of symptoms and signs to detect Alzheimer's, these methods are open to major variations in medical opinion about a single patient. There is a danger of Alzheimer's disease - AD - being confused with any other dementia or common declining intellectual disabilities.

Sometimes, memory loss need not be the first symptom of Alzheimer's and it could be behavioral or language changes or difficulty in everyday activities. Hence, doctors treating Alzheimer are always left to face uncertainty in trying to diagnose the disease in the living, and only an autopsy can confirm the disease for certain.

A pioneering brain image - Tau brain imaging - can detect the build-up of destructive proteins linked to Alzheimer's. This is the beginning of diagnosing the condition and testing of new drugs. Reported in the journal Neuron, tau brain scan can identify living clumps of a protein called tau that is closely linked to the disease. With this new diagnosis, patients can be helped early to make the most of their remaining life span. This definitive diagnosis can tell Alzheimer's disease apart from other disorders.

To understand this, it is relevant to know that Alzheimer's patients lose their brain's nerve fibers and there is an abnormal buildup of protein that damages nerve cells. Patients who begin with mild memory loss soon worsen to become restless, anxious, confused and moody. Patients lose their ability to talk or care for themselves in the final stages.

Tauopathies are a set of neuro-degenerative diseases associated with phosphorylated tau protein aggregation in the human brain. In Alzheimer's, tau protein is deposited within the neurons as neurofibrillary tangles. The German psychiatrist and later Neuro pathologist Dr. Alois Alzheimer was the first to describe this disease as pre senile dementia.

It is the associated protein tau that causes the tangles to aggregate in an insoluble form. The tau protein is referred to as 'PHF' or paired helical filaments. There are other conditions as well in which such neurofibrillary tangles are observed and these include progressive supranuclear palsy, chronic traumatic encephalopathy, Parkinson-dementia complex, ganglioglioma, meningioangiomatosis and tuberus sclerosis among others. These non-Alzheimer's tauopathies are grouped as Pick's complex.

A protein called tau (τ) is very closely linked to Alzheimer's and tangles of tau are thought to be one way in which the brain cells are killed. Researchers have developed a chemical that could bind to tau and then be detected during a brain scan. This was tested on mice and people and it showed that suspected Alzheimer's could be revealed by this technology that could detect tau.

Dr Makato Higuchi, National Institute of Radiological Sciences, Japan says that this emission tomography image of tau accumulation provides robust information on brain regions and also risk for tau-induced neuronal death. Although this research is at an early stage, it could eventually lead to identifying Alzheimer's.

As another Alzheimer's expert says "Tau can be compared to railroad ties that stabilize a train truck that brain cells use to transport food, messages and other vital cargo throughout neurons. In Alzheimer's, changes in tau protein causes the tracks to become unstable in neurons of the hippocampus, the center of memory. Abnormal tau spreads from cell to cell, disseminating pathological tau in the brain cortex".

While researchers have already tried time-tested medical imaging techniques to detect this disease, and while magnetic resonance imaging and computed tomography scan only rule out other disorders, there is no positive detection tool for Alzheimer's. Tau imaging highlights a new method for detecting tau, which would be a key player in both Alzheimer's and frontotemperal dementia in the living brain. The tau scan is capable of visualizing the protein inside the brain and is important for assessing whether treatments in clinical trials are hitting the target.

If the tau scan is shown to be effective, then it could become a potential aid for providing people with accurate diagnosis for monitoring the disease progression. The new focus for Alzheimer's treatment is halting the toxic tau.

A set of researchers at the Mayo Clinic in the US were able to look at the evolution of tau using neuro pathologic measures. Just like one could identify the changing seasons by looking at the rings of a tree, and the aging of the tree by viewing the cross section, studying the different stages of Alzheimer's gives a perspective of the cognitive impact of a wide range of amyloids and tau severity. At the Mayo brain bank, a collection of thousands of post mortem brains have allowed to understand changes in tau and amyloid that occur over a period of time.

There is an estimated 3 to 4 million people in the US with some form of Alzheimer's and there is a tendency for the number to increase over the years. Therefore, a good diagnostic tool is a must. Tau imaging represents significant advancement in the field and it is hoped that combined tau and amyloid positive PET scans may in the future help researchers get closer to an affirmative diagnosis of Alzheimer's disease.