Dementia refers to a significant intellectual decline that persists over time and affects several areas of cognition (thinking). Dementia often is not diagnosed until months or even years after its onset.
Memory loss is a universal feature of dementia, but other functions are impaired as well, such as abstract thinking and language.
Approximately 1 percent of dementia cases are reversible. In these instances, people may have a physical or psychological condition (such as an operable brain tumor, vitamin B12 deficiency, thyroid disease, alcoholism or depression) that can be cured with treatment.
The most common cause of reversible dementia is a toxic reaction to prescription or over-the-counter medications.
Diagnosis of dementia
Differentiating between irreversible dementia and dementia that results from a medical condition involves a process of systematic elimination. Doctors often start by looking for conditions that are most readily correctable. If these possibilities can be eliminated, then more serious, irreversible dementias—such as Alzheimer’s disease—are considered.
The presence of reversible disorders can complicate the diagnosis of irreversible forms of dementia. In these instances, diagnosing and treating the concurrent condition can provide a clearer view of any problems that persist.
The first step in diagnosis is a thorough medical history and physical examination to identify any vision, hearing, cardiovascular, thyroid or other disorders. Although checking for these conditions might seem unnecessary, they often go unrecognized in older adults and can have a significant effect on memory.
For example, heart failure (a decrease in the heart’s ability to pump blood) may impede mental functioning by reducing the amount of blood circulating to the brain. Recovering from cardiac arrest or heart bypass surgery also can affect memory. Research suggests that about 50 percent of people who undergo heart bypass surgery experience a decline in cognitive function.
The National Institute on Aging-Alzheimer’s Association workgroup recently revised the criteria for diagnosing dementia. The new guidelines can be used by both general healthcare providers as well as specialists, and they allow doctors to diagnose dementia in its mildest and most severe stages.
• A person has cognitive and behavioral symptoms that interfere with his or her ability to function at work or at activities, represent a decline from previous levels of functioning, and are not explained by delirium or a psychiatric disorder.
• The condition is diagnosed by interviewing the patient and someone who knows him or her (perhaps a family member or close friend). This type of interview can be crucial because someone close to the patient knows the individual’s previous level of functioning and can help the physician determine whether cognitive deterioration has occurred.
In addition, an objective cognitive assessment should be performed. This assessment could involve a mental status examination or neuropsychological testing. Mental status tests, such as the Mini-Mental State Examination, the Short Test of Mental Status or the Cognitive Capacity Screening Examination, are given to check for any general cognitive impairment. The Clock-Drawing Test and the Time and Change Test are two other simple tests for dementia. All of these tests take only about five to 15 minutes to complete and can serve as a baseline for comparison should further testing be necessary.
• Cognitive or behavioral impairment occurs in at least two of the following areas: difficulty acquiring and remembering new information (the person might forget appointments, misplace belongings or get lost on a familiar route); difficulty reasoning and handling complex tasks (doesn’t understand safety risks, has difficulty managing finances); has trouble recognizing faces or common objects, putting on clothing or finding objects in direct view; difficulty with speaking, reading or writing (the person is having a hard time thinking of common words while speaking and makes speech, spelling and writing errors); changes in personality, behavior or comportment (the person has uncharacteristic mood fluctuation and decreased interest in previous activities).
The American Academy of Neurology recommends the following tests in the routine evaluation of a patient with suspected dementia:
• Complete blood cell count
• Electrolyte levels in the blood (potassium, sodium and chloride)
• Blood levels of glucose (sugar), urea nitrogen and creatinine
• Blood levels of vitamin B12
• Liver function tests and thyroid function tests
• Depression screening
A routine evaluation would not include single-photon emission computed tomography (SPECT), genetic screening or testing for a variant form of the apolipoprotein E (APOE) gene that significantly increases the risk of developing Alzheimer’s disease. Testing for syphilis or performing a lumbar puncture to check the spinal fluid for biochemical “red flags” (markers) of Alzheimer’s disease would only be done in special circumstances.
The American Academy of Neurology maintains that the usefulness of positron emission tomography (PET), genetic markers for Alzheimer’s disease (other than APOE) and biochemical markers for Alzheimer’s disease in cerebrospinal fluid is not known at this time.