Dementia is a decline in cognitive function. It may affect memory, thinking, language, judgment, and behavior. Traditionally, a diagnosis of dementia is based on noticeable signs of decline.
In April 2011, the National Institute on Aging (NIA) of the National Institutes of Health (NIH) and the Alzheimer’s Association published specific criteria for diagnosing dementia.
Dementia is diagnosed only when the following three criteria are met:
- The symptoms interfere with your ability to function at work or at usual activities.
- The symptoms represent a decline from previous levels of functioning and performing.
- The symptoms are not explained by delirium or a major psychiatric disorder.
In addition, your symptoms must include at least two of the following:
- Impaired ability to acquire and remember new information. Symptoms include: repeating questions or conversations; misplacing personal belongings; forgetting events or appointments; getting lost on a familiar route.
- Impaired reasoning and handling of complex tasks and poor judgment. Symptoms include: poor understanding of safety risks; inability to manage finances; poor decision-making ability; inability to plan complex or sequential activities.
- Impaired visuospatial ability. Symptoms include: inability to recognize faces or common objects or to find objects in direct view despite good acuity; inability to use simple tools or dress yourself.
- Impaired language functions. Symptoms include: difficulty thinking of common words while speaking; hesitations; speech, spelling, and writing errors.
- Changes in personality, behavior, or demeanor. Symptoms include: uncharacteristic mood fluctuations such as agitation, impaired motivation, apathy, social withdrawal, decreased interest in previous activities, loss of empathy, compulsive or obsessive behaviors, and socially unacceptable behaviors.
Your doctor may be able to diagnose dementia based on a physical exam and health history. The exam will include tests to check your mental function. This is called a mental status examination. If this is not enough for a diagnosis, more tests may be required.
A detailed patient history will include:
- how and when symptoms developed
- your overall medical condition and history
- your family’s overall medical condition and history
- assessment of your emotional state and living environment
The doctor will also request information from your close friends and family members. This is important because those closest to you may have observed changes in your personality, behavior, memory, and cognitive skills.
A physical exam includes checking your hearing, eyesight, heart, lungs, temperature, blood pressure, and pulse. Your doctor may also order lab tests to help eliminate or identify other health problems, particularly those associated with reversible causes of mental status changes. Possible tests include:
- toxicology screen: Alcohol or medications can cause symptoms mimicking dementia.
- thyroid function tests: thyroid disease may cause altered mentation.
- blood chemistry: imbalance of certain electrolytes or evidence of liver dysfunction may explain changes in brain function.
The most common test of this kind is the Mini-Mental State Exam (MMSE). The MMSE includes 11 questions/tasks designed to evaluate your basic mental status. Questions/tasks include:
- What is the date today?
- Where are we?
- Count to 100 by sevens.
- Write a sentence.
Pictures of your brain may help your doctor make an accurate diagnosis. It is important to know the cause of your symptoms. This will help determine if your condition can be treated or reversed.
Magnetic resonance imaging (MRI) and computed tomography (CT) scans can help find or rule out brain tumors or blood clots that might be causing dementia.
A PET (positron emission tomography) scan allows the doctor to see how your brain is functioning.
A functional MRI (fMRI) measures the changes that take place in active parts of the brain.
A single photon-emission computed tomography (SPECT) shows the distribution of blood in the brain, which generally increases with brain activity.
Magnetoencephalography (MEG) shows the electromagnetic fields produced by the brain's neuronal activity.