Alzheimer's Disease Diagnosis

At one time in the not-so-distant past, the only way to definitively diagnose Alzheimer’s disease (AD) was post-mortem—after the person had died and an autopsy of the brain was performed. Thankfully today, an experienced physician can be reasonably confident about making an accurate diagnosis in a living person.

That being said, making an accurate diagnosis of AD is as much an art as it is a science. Why? There are multiple conditions (neurodegenerative and other causes for dementia) that show similar symptoms to AD. And while we know that genetics play a distinct role, approximately 75 percent of individuals with Alzheimer disease have no known family history of AD. Thus, having a doctor who is an expert in AD diagnostics is essential.

Diagnostic Steps

As described by the National Institute on Aging (NIA), a doctor experienced in diagnosing AD will take the following steps.

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 family’s overall medical condition and history
• assessment of the person’s emotional state and living environment

Additionally, the doctor will seek 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 and Lab Tests

A comprehensive physical exam will be conducted, including:

• an evaluation of the patient’s hearing, sight, heart, lungs, temperature, blood pressure, and pulse readings
• 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 neuropsychological test is the 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. This test is by no means perfect; its results can be affected, for example, by how much education a person has, but it is a fair start at assessing whether a patient may have Alzheimer’s disease.

Brain Imaging

• MRI (magnetic resonance imaging) and CT (computed tomography) scans: These are diagnostic tools that help rule out other reasons for AD symptoms, 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 as measured by the use of glucose in specific parts of the brain.

Genetic Testing

Diagnosing early-onset AD (when symptoms appear in a person well before the age of 60) will very likely include genetic testing.

The Latest in AD Diagnostics Criteria

Established in 1984, the diagnostic criterion for dementias in general (and Alzheimer’s disease, in particular) primarily focus upon when signs of problems in thinking, learning, and memory became noticeable to an individual, family, or friends.

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

Thus, to reflect our current thinking that AD begins creating distinct and measurable changes in the brains of affected people years (and perhaps even decades) ­before memory and thinking symptoms are noticeable, the National Institute on Aging (NIA) of the National Institutes of Health (NIH) and the Alzheimer’s Association have published (as of April 2011) the following three additional overarching phases to better reflect the progression of AD over time, as part of the diagnostic process.

Preclinical Alzheimer’s Disease

This denotes changes that may indicate the very earliest signs of disease—for example, measurable changes in biomarkers (such as brain imaging and spinal fluid chemistry) before outward symptoms are visible. Currently, there are no clinical diagnostic criteria for this phase; however, a scientific framework has been created to help researchers better define this stage of Alzheimer’s.

Mild Cognitive Impairment (MCI) Due to Alzheimer’s Disease

This denotes mild changes in memory and thinking abilities, enough to be noticed and measured, but not to an extent that impairs or compromises an individual’s ability to function independently and conduct everyday activities.

Dementia Due to Alzheimer’s Disease

This denotes cognitive (e.g., memory and thinking) and behavioral symptoms that impair an individual’s ability to function in daily life.