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Diagnosis of Alzheimer's Disease Dementia

The Neurobehavior and Memory Clinic at Northwestern Medicine is affiliated with our center and offers clinical consultations to patients, families and providers, including diagnostic evaluations, second opinions and supportive services.  

A diagnosis of Alzheimer disease dementia (AD) is made when an individual experiences short-term memory loss that is disruptive to their everyday life activities and these changes are determined to be due to a neurodegenerative process (see causes below).  

If a person is evaluated by a doctor very early in the course of the disease, at a point when they are still able to manage all daily affairs independently, they may be given a diagnosis of mild cognitive impairment (MCI) 

There is no one test to diagnose Alzheimer’s disease dementia; instead, the diagnosis is made through a process of "ruling in" and "ruling out." Components of an evaluation include obtaining medical history from the individual with memory changes and their family, neurological exam, cognitive assessment by a neuropsychologist and laboratory tests (e.g., blood work, cerebrospinal fluid analysis and brain imaging with MRI or PET).   

Factors in Determining an Alzheimer's Disease Dementia Diagnosis

  • Signs and symptoms that a person experiences are the most helpful in determining the cause of one’s memory and thinking changes. Assessing this will usually involve tests of memory and other aspects of thinking that can be administered in a doctor’s office.   
  • Basic blood tests should be done to rule out other medical problems or vitamin deficiencies that may be affecting a person’s brain function. Newer blood tests are emerging that may be helpful in the diagnostic process.  
  • Special imaging of the brain such as MRI (magnetic resonance imaging) is also often an important test to rule out uncommon things like tumors, but also more common things like small strokes or changes caused by chronic vascular disease. MRI can also reveal patterns of atrophy (shrinkage) of the brain that may be more suggestive of neurodegenerative disease over other causes. 
Additionally, there are newer tests that may assist in determining the likely underlying neuropathology responsible for the symptoms. These include amyloid and tau PET imaging and lumbar puncture (spinal tap) to examine protein levels in cerebrospinal fluid (CSF) as well as emerging blood based biomarkers. These tests are increasingly being used to identify the presence of abnormal proteins accumulating in the brain. These procedures may not be covered by insurance and may not be appropriate for everyone. Scientists are working to identify new reliable biomarkers. The Mesulam Center is actively involved in these studies.

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