Alzheimer's diagnosis
Alzheimer’s diagnosis
How is Alzheimer’s disease diagnosed?
There is currently no single test to identify Alzheimer’s disease. The diagnosis is made only after careful clinical consultation.
The clinical diagnosis might include:
A detailed medical history
A thorough physical and neurological examination
A test of intellectual function
Psychiatric assessment
A neuropsychological tests
Blood and urine tests
Lumbar puncture for cerebral spinal fluid tests
Medical imaging (MRI, PET)
These tests will help to eliminate other conditions with similar symptoms such as nutritional deficiencies or depression. After eliminating other causes, a clinical diagnosis of Alzheimer’s disease can be made with about 80% to 90% accuracy if the symptoms and signs are appropriate. The diagnosis can only be confirmed after death by examination of the brain tissue.
It is important to have an early and accurate diagnosis to determine whether a treatable condition other than Alzheimer’s disease, is causing the symptoms. If Alzheimer’s disease is diagnosed, medical treatment and other assistance can be discussed.
The Healthy Human Brain
The whole brain is fed and provided with oxygen by a complex network of arteries, veins and capillaries. This vascular network is strictly controlled and segregates the brain from the rest of the blood stream. The blood brain barrier protects the brain from infection, but consequently if the brain does become infected it is difficult to treat, as many antibiotics are too large in their molecular structure to cross the barrier. This is also a major problem when finding agents to treat Alzheimer’s disease, as they must pass this barrier to target the brain.
Behind the ears and temples are the temporal lobes of the brain. These regions process speech and working memory, and also ‘higher’ emotions such as empathy, morality and regret. Beneath the forebrain are the more primitive brain regions such as the limbic system. The limbic system is a structure that is common to all mammals and processes our desires and many emotions. Also in the limbic system is the hippocampus – a region that is vital for forming new memories.
The cerebellum is at the back of the brain, which stores our muscle memory so we can do things without thinking – such as riding a bike. The midbrain and brain stem are the most primitive regions of the brain. They control bodily functions such as heart rate and digestion and act as an interface between the spinal cord and the rest of the brain.
All these complex tasks are mediated by the connections between the brain cells (neurons) called synapses. In the adult human brain there are around 100 billion brain cells, each connected to its neighbours by 5-10,000 synapses.
Our brains form a million new connections – a million new synapses – every second we are alive. The pattern and strength of the connections is constantly changing and no two brains are alike.
It is in these changing connections that memories are stored, habits learned and personalities shaped, by reinforcing certain patterns of brain activity, and losing others.
Brain cells communicate though synapses in a variety of ways. Signals pass move across the synapse in the form of chemicals that are known as neurotransmitters. Neurotransmitters a passed from one brain cell, across the synapse (connection) and to the receiving brain cell, which collects the neurotransmitter with a receptor. The receiving cell can then send out another burst of neurotransmitters to other brain cells to pass the message on.
The Brain with Alzheimer’s Disease
Going back to the 1900s, Dr Alzheimer examined the brain of his patient, Mrs Deter, upon her death. He found shrinking of the outer layer of the brain or cortex – the region of the brain involved in memory, language and judgment. We know that the so called shrinking of the brain is caused by the death of the brain cells.
Dr Alzheimer also found two types of deposits in Deter’s brain. One kind was found outside the brain cells, which are known plaques and the other type of deposit was found inside brain cells known as “neurofibrillary tangles. These plaques impair synapses so signals cannot pass between brain cells. Tangles kill brain cells by preventing the normal transport of food and energy around the brain cell.
As brain cells die the brain shrinks, which can be detected using imaging such as magnetic resonance imaging (MRI).
The outer part of the brain is usually the area affected first by the disease. Short-term memory loss is therefore one of the first symptoms of Alzheimer’s disease. But as the disease progresses to deeper parts of the brain, long-term memory is also lost. The disease also affects many of the brain’s other functions and consequently, many other aspects of behaviour are disturbed.
Apart from the few individuals with Familial Alzheimer’s disease, it is not known why one individual gets Alzheimer’s disease late in life and another does not. Scientists are investigating what triggers the formation of plaques and tangles and about other chemical changes that damage brain cells in Alzheimer’s disease.
A variety of suspected causes are being investigated including factors in the environment, biochemical disturbances and immune processes. The cause may vary from person to person and may be due to one factor or a number of factors.
Doctors use several methods and tools to help determine whether a person who is having memory problems has Alzheimer’s disease.
To diagnose Alzheimer’s, doctors may:
Ask the person and a family member or friend questions about overall health, use of prescription and over-the-counter medicines, diet, past medical problems, ability to carry out daily activities, and changes in behavior and personality.
Conduct tests of memory, problem solving, attention, counting, and language.
Carry out standard medical tests, such as blood and urine tests, to identify other possible causes of the problem.
Perform brain scans, such as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET), to support an Alzheimer’s diagnosis or to rule out other possible causes for symptoms.
These tests may be repeated to give doctors information about how the person’s memory and other cognitive functions are changing over time.
People with memory and thinking concerns should talk to their doctor to find out whether their symptoms are due to Alzheimer’s or another cause, such as stroke, tumor, Parkinson’s disease, sleep disturbances, side effects of medication, an infection, or another type of dementia. Some of these conditions may be treatable and possibly reversible.
If the diagnosis is Alzheimer’s, beginning treatment as early as possible in the disease process could help preserve daily functioning for a while. An early diagnosis also helps families plan for the future. They can take care of financial and legal matters, address potential safety issues, learn about living arrangements, and develop support networks.
In addition, an early diagnosis provides people with more opportunities to participate in clinical trials or other research studies testing possible new treatments for Alzheimer’s.
There is no single diagnostic test that can determine if a person has Alzheimer’s disease. Physicians (often with the help of specialists such as neurologists, neuropsychologists, geriatricians and geriatric psychiatrists) use a variety of approaches and tools to help make a diagnosis. Although physicians can almost always determine if a person has dementia, it may be difficult to identify the exact cause.
During the medical workup, the health care provider will review the person’s medical history, including psychiatric history and history of cognitive and behavioral changes. He or she will want to know about any current and past medical problems and concerns, as well as any medications the person is taking. The doctor will also ask about key medical conditions affecting other family members, including whether they may have had Alzheimer’s disease or other dementias.
Ask about diet, nutrition and use of alcohol.
Review all medications. (Bring a list or the containers of all medicines currently being taken, including over-the-counter drugs and supplements.)
Check blood pressure, temperature and pulse.
Listen to the heart and lungs.
Perform other procedures to assess overall health.
Collect blood or urine samples for laboratory testing.
The physician will test:
Reflexes.
Coordination, muscle tone and strength.
Eye movement.
Speech.
Sensation.
The neurological exam may also include a brain imaging study.
Mental cognitive status tests
Mental cognitive status testing evaluates memory, thinking and simple problem-solving abilities. Some tests are brief, while others can be more time intensive and complex. More comprehensive mental cognitive status tests are often given by a neuropsychologist to evaluate executive function, judgment, attention and language.
Genetic testing
Researchers have identified certain genes that increase the risk of developing Alzheimer’s and other rare “deterministic” genes that directly cause Alzheimer’s. Although genetic tests are available for some of these genes, health professionals do not currently recommend routine genetic testing for Alzheimer’s disease.
Risk genes: While there is a blood test for APOE-e4, the strongest risk gene for Alzheimer’s, this test is mainly used in clinical trials to identify people at higher risk of developing Alzheimer’s. Carrying this gene mutation only indicates a greater risk; it does not indicate whether a person will develop Alzheimer’s or whether a person has Alzheimer’s. Genetic testing for APOE-e4 is controversial and should only be undertaken after discussion with a physician or genetic counselor.
Deterministic genes: Testing also is available for genes that cause autosomal dominant Alzheimer’s disease (ADAD) or “familial Alzheimer’s,” a rare form of Alzheimer’s that accounts for 1 percent or less of all cases. ADAD runs strongly in families and tends to begin earlier in life, sometimes as early as one’s 30s. Many people in these families do not wish to know their genetic status, but some get tested to learn whether they will eventually develop the disease. Some ADAD families have joined clinical studies to help researchers better understand Alzheimer’s.
A standard medical workup for Alzheimer’s disease often includes structural imaging with magnetic resonance imaging (MRI) or computed tomography (CT). These tests are primarily used to rule out other conditions that may cause symptoms similar to Alzheimer’s but require different treatment.