Importance of Early Diagnosis
An early and accurate diagnosis of memory or other cognitive difficulties is crucial for several reasons. Foremost, a thorough evaluation can reveal any treatable or even reversible causes of cognitive impairment. If Mild Cognitive Impairment (MCI), Alzheimer’s disease (AD), or another dementia is diagnosed, it can facilitate planning and permit patients and families to access available medications and services. Also, with early diagnosis, critical safety issues (e.g., living alone, driving) can be addressed before a crisis occurs.
Understanding the Diagnostic Process
At present, there is no single diagnostic test for detecting AD and other forms of dementia. Rather, the diagnosis is based on a thorough assessment by an experienced clinical to determine the presence (i.e., inclusion) and absence (i.e., exclusion) of particular symptoms. If done thoroughly, such a diagnostic process can yield a highly accurate clinical diagnosis.
Cognitive impairment and dementia can result from a variety of progressive and non-progressive ‘irreversible’ as well as ‘potentially reversible’ causes. For example, potentially reversible causes of cognitive impairment and dementia include severe depression and metabolic disorders (e.g., vitamin B12 deficiency and hypothyroidism) as well as structural brain changes such as occur in Normal Pressure Hydrocephalus (NPH). Medication side effects can cause reversible cognitive difficulties. If a particular drug, or combination of multiple drugs, are causing the cognitive impairments, then stopping the medication(s) and/or changing the dosage may improve symptoms. In some cases, a person may develop cognitive impairment that remains stable and does not progress. A common cause of non-progressive cognitive impairment is a single stroke which permanently impairs certain functions. Another increasingly recognized cause of non-progressive cognitive impairment is traumatic brain injury, as might occur in an auto accident, sports, or combat.
In addition to AD, progressive irreversible causes of dementia include vascular dementia, dementia with Lewy bodies, Parkinson’s disease dementia, frontotemporal dementia, and several other disorders. It is important for physicians to ascertain the most likely cause of the dementia, as the treatment plan may differ.
- A complete clinical history that includes questions about the individual’s overall health, current and past medical conditions, prescription and over-the-counter medications, risk factors (e.g., head trauma, excessive alcohol use), ability to perform daily activities, and changes in behavior and personality.
- Physical and neurological examinations to, for example, look for changes such as slowed movement, weakness, or other symptoms linked to neurological disorders such as Parkinson’s disease or stroke.
- Neuroimaging to look for structural (e.g., CT, MRI), metabolic (e.g., SPECT, FDG, PET), or disease-related (amyloid PET) changes.
- Laboratory tests of blood and urine to check for possible contributors to any cognitive difficulties, such as a B12 deficiency.
- Neuropsychological assessment measures performance on paper-and-pencil tests assessing orientation to time and place, recent memory, language, attention, visual-spatial abilities, and executive functioning (e.g., reasoning, problem-solving, insight, multi-tasking, and planning).
Probable, Possible, and Definite Alzheimer’s Disease
A definite diagnosis of AD can still only be given upon death, following an autopsy of the brain in which a neuropathologist looks for hallmark senile plaques and neurofibrillary tangles in the brain. During life, a doctor may use the terms “probable” and “possible” to indicate the level of diagnostic certainty. A diagnosis of “probable AD” means the doctor has ruled out all other possible sources of the cognitive impairment, leaving AD as the most likely cause. When the cognitive impairment is believed to be due to AD but another condition (e.g., vascular disease) exists that could be contributing to the dementia, a doctor may give the diagnosis of “possible AD.”
Some individuals may have more memory or cognitive difficulties than is typical for people their age, but continue to be able to manage their day-to-day activities. In this case, the doctor may diagnose MCI, a high-risk pre-dementia state.
For more information on diagnostic evaluations, please contact our Memory Assessment and Research Center at 949.824.2382.