Established in 1984, the diagnostic criterion for dementias in general (and Alzheimer’s disease, in particular) primarily focused upon when signs of problems in thinking, learning, and memory became noticeable to an individual, family, and friends. This approach has served us well.

However, our knowledge of the clinical manifestations and biology of dementias has vastly increased over the past 27 years—due in no small part to significant technological advances, the ongoing efforts of research scientists, ­and to clinical trials participants.

Thus, as of April 2011, the National Institute on Aging (NIA) of the National Institutes of Health (NIH) and the Alzheimer’s Association has published the following to reflect our most current understanding and advances.

Dementia Criteria (Regardless of Cause)

Dementia is only diagnosed when there are cognitive or behavioral (neuropsychiatric) symptoms that satisfy the following three criteria:

  1. interfere with a person’s ability to function at work or at usual activities
  2. represent a decline from previous levels of functioning and performing
  3. are not explained by delirium or major psychiatric disorder

In order for a doctor to diagnose a condition as dementia, there must be cognitive or behavioral impairment involving a minimum of two of the following:

  • an impaired ability to acquire and remember new information
    • symptoms: repetitive questions or conversations, misplacing personal belongings, forgetting events or appointments, getting lost on a familiar route
  • an impaired reasoning and handling of complex tasks, and poor judgment
    • symptoms: poor understanding of safety risks, inability to manage finances, poor decision-making ability, inability to plan complex or sequential activities
  • an impaired visuospatial ability.
    • symptoms: inability to recognize faces or common objects or to find objects in direct view despite good acuity, inability to operate simple implements, or orient clothing to the body
  • an impaired language functions (speaking, reading, writing)
    • symptoms: difficulty thinking of common words while speaking, hesitations; speech, spelling, and writing errors
  • changes in personality, behavior, or demeanor
    • symptoms: uncharacteristic mood fluctuations such as agitation, impaired motivation, initiative, apathy, loss of drive, social withdrawal, de- creased interest in previous activities, loss of empathy, compulsive or obsessive behaviors, socially unacceptable behaviors.

Diagnostic Steps

Cognitive impairment is detected and diagnosed through a combination of taking a patient history from the patient and a knowledgeable informant and by conducting an objective cognitive assessment. The assessment can be comprised of either a “bedside” mental status examination or neuropsychological testing (when the routine history and bedside mental status examination can’t provide a confident diagnosis).

Patient History

A detailed patient history will be conducted, including:

  • description of how and when symptoms developed
  • description of the person’s overall medical condition and history
  • description of the person’s family’s overall medical condition and history
  • assessment of the person’s emotional state and living environment

Additionally, the doctor will seek to get information from the patient’s close friends and family members. This part of the diagnostic process often proves to be particularly instructive—as those closest to the patient can offer valuable insights concerning possible changes in the patient’s personality, behavior, memory and cognitive skills.

Physical Examination

A comprehensive physical exam will be conducted. Typically, this includes evaluating a patient’s hearing, sight, heart, lungs, temperature, blood pressure and pulse readings. A doctor may also order lab tests (such as blood, urine tests and possibly spinal fluid) to help eliminate and/or identify additional health problems, such as diabetes, or thyroid or liver problems.

Neuropsychological Testing

The most commonly used test of this kind is he Mini-Mental State Exam (MMSE). The MMSE includes a selection of questions and tasks designed to evaluate a patient’s basic cognitive (mental) status, e.g., do they know today’s date and where they are; can they repeat a list of words or a phrases; can they count backwards from 100 by sevens.

Brain Imaging

MRI (magnetic resonance imaging) and CT (computed tomography) Scan—these are diagnostic tools that reveal the structures of the brain. This helps rule out other reasons for symptoms of dementia, such as brain tumors or blood clots in the brain

PET (positron emission tomography) scan—this diagnostic tool allows the doctor to see levels of brain activity, i.e., how the brain and its tissues are functioning.

Functional MRI (fMRI)—measures the metabolic changes that take place in active parts of the brain

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.