Diagnosis of Alzheimer’s Disease

Currently diagnosing Alzheimer’s Disease is a far from straightforward process as there is no conclusive diagnostic test to confirm it. Instead the diagnosis is based at looking at symptoms and trying to identify any other possible cause for those symptoms.

Loss of memory is the symptom that is most commonly associates with Alzheimer’s, but occasional memory lapses happen to everyone and it is only when memory problems become significant, with perhaps the inability to remember names of well known people or objects, difficulty in performing familiar tasks and other changes in cognitive ability and behaviour that a significant problem may be suspected. Even then, problems commonly associated with Alzheimer’s Disease may be symptoms of a number of different conditions such as:

• central nervous system and other degenerative disorders: such as stroke, brain injury, Parkinson’s or Huntington’s Disease;
• metabolic disorders such as hypothyroidism, malnutrition, kidney or liver failure;
• medication induced problems such as drug interactions or side effects;
• psychological conditions such as depression, chronic stress and chronic sleep deprivation;
• infections such as meningitis and encephalitis

Some of the causes of Alzheimer’s-like symptoms are treatable and reversible and ruling out all other possible causes of symptoms is therefore the first step in making a diagnosis of Alzheimer’s Disease. Once all other likely causes of symptoms have been excluded, a diagnosis of probable Alzheimer’s is likely to be given.

Tests and evaluations commonly performed to establish a probable diagnoses of Alzheimer’s Disease:

• Medical history
• Physical examination
• Neuropsychological testing
• Brain-imaging scan

Although there are a number of tests that may point to a diagnosis of Alzheimer’s Disease, currently the only absolutely conclusive way of making diagnosis is by autopsying the brain after death. Brain autopsy can show the presence of amyloid plaques which are one of the hallmarks of Alzheimer’s.

Advances in Diagnosing Alzheimer’s Disease

Eli Lilley has a new imaging agent called Florbetapir (awaiting FDA and other approval) which, when injected into suspected Alzheimer’s sufferers allows amyloid plaques to be detected during a brain scan. If approved, this imaging agent may allow a more certain diagnosis of Alzheimer’s Disease to be made at an earlier stage.

Another recent breakthrough may make it possible to identify people at risk of Alzheimer’s by using a simple blood test to measure the levels of apolipoprotein E (ApoE). ApoE protein is produced by the ApoE gene, the most important genetic risk factor known for Alzheimer’s Disease.

Scientists found that people with high blood levels of ApoE had significantly greater beta amyloid deposits in the part of the brain associated with memory function. Further research will examine how changes in levels of this protein relate to injuries to the brain.

A pilot study undertaken by researchers at University College London, which looked at healthy 70 and 80 year olds, indicated that combining two different tests could help to diagnose Alzheimer’s even before symptoms occur.

Levels of a protein called cerebrospinal fluid (CSF) amyloid were measured in participants, who were then given MRI scans over the following year, to measure brain shrinkage rates. The brains of individuals with low levels of CSF shrank twice as fast as the brains of those people with higher levels. Those with lower CSF levels were also five times more likely to have the ApoE gene, a risk factor for Alzheimer’s.

Early detection and treatment for people with Alzheimer’s Disease may help to slow the progress of the disease and, scientists hope, eventually be able to prevent it from causing symptoms.

Stained Amyloid Plaques: Amyloid Plaques are a hallmark of Alzheimer’s Disease]