Putting the science in fiction - Dan Koboldt, Chuck Wendig 2018
Dementia myths, part II
The brain is wider than the sky
By Anne M. Lipton, M.D., Ph.D.
This chapter focuses on the evaluation, diagnosis, and treatment of dementia and common misconceptions regarding these aspects of dementia in writing and popular culture.
Myth #1: Dementia can be diagnosed quickly and easily
Dementia is a hard diagnosis to receive, a hard diagnosis to give, and often requires hard work to diagnose. An adequate evaluation for dementia can require painstaking time and effort, especially for those with milder symptoms and/or unusual features, such as age of onset under sixty-five or behavioral problems early in the course of disease. A medical professional (doctor or similar) makes a diagnosis of dementia based on several factors:
1. MEDICAL HISTORY: A patient with dementia may not be able to provide necessary information due to memory loss or other cognitive problems. Therefore, medical history is also gathered from a family member or another individual close to the patient.
2. HISTORY OF PRESENT ILLNESS: This encompasses initial symptom (problems with memory, language, mood, or behavior), associated symptoms (problems with gait [walking]), onset (When did symptoms start?), duration (length of symptoms), and disease course/progression (gradual, stair-step, rapid, or fluctuating). It is important to ascertain the impact of these symptoms on daily functioning. The patient’s medical history, medications, and social history (use of alcohol and other substances, sexual history, and education/occupation) may also be relevant.
3. EXAMINATION OF THE PATIENT: This includes mental status (cognition, such as memory, language, visuospatial skills, and executive functioning). The diagnosis may require up to a full day of neuropsychological testing (which includes thorough cognitive assessment). The history and examination may be enough to diagnose dementia and even the type of dementia based on certain clinical criteria and guidelines. In medical school, doctors are taught to listen carefully as “the patient gives the diagnosis.” Specialists who care for people with dementia learn that the family gives the diagnosis.
Myth #2: A blood test is the best way to diagnose dementia
Dementia is a clinical diagnosis. Generally speaking, the history is more important than any test in diagnosing dementia. Laboratory and other tests may aid in clarifying the type of dementia and are useful in evaluating for treatable conditions. However, no individual test or medical procedure (or combination thereof) is sufficient for a diagnosis of dementia.
A biomarker is a substance, such as a protein in blood or spinal fluid, which may serve as an objective measure of disease. Researchers have identified a number of potential biomarkers of dementia, but none are definitive. A diagnosis of dementia cannot be made solely on the basis of a lab test, brain scan, lumbar puncture (spinal tap), and/or other medical diagnostic procedure (at least with currently available technology). However, lab tests of blood and urine may help identify or rule out (exclude) reversible types of dementia. In the future, it is more likely that a panel of protein, genetic, or other biomarkers will be used in the diagnosis of dementia rather than a single biomarker.
Genetic testing is a major focus of dementia research. Such testing may inform the diagnosis for certain patients, based on family history, early age of onset, and other factors. It also may help pinpoint a specific type of dementia. However, the genetics for most cases of dementia are not well understood. An analogy may be drawn with heart attacks: While heart attacks seem to run in some families, they are not usually linked to a specific genetic mutation but rather a mix of genetic, environmental, and lifestyle factors.
If a patient has a certain gene or genetic mutation associated with dementia, it may simply confer an increased risk and not necessarily indicate that the individual has dementia or is destined to get it. In many cases where dementia is a concern, genetic testing adds cost without adding benefit. Such testing may even create harm by sowing confusion or have untoward employment or insurance implications for patients and families.
Myth #3: “They saw dementia on the brain scan”
Dementia per se can’t be seen on a brain scan, however, a brain scan may reveal associated features of dementia. Current clinical guidelines recommend structural neuroimaging with head computed tomography (CT) or brain magnetic resonance imaging (MRI) as part of a medical evaluation for dementia. Associated neuroimaging features include atrophy (brain shrinkage) and cerebrovascular disease (CVD). Such findings may help diagnose a specific type of dementia, as certain patterns of atrophy suggest certain types of dementia.
CVD is blood vessel disease of the brain, such as leukoaraiosis (small-vessel white matter disease) or evidence of strokes (infarcts, or dead brain tissue). A significant amount of CVD may suggest a vascular dementia, but not always. Atrophy and/or CVD may occur in a person with no dementia, in which case these findings are said to be “nonspecific” or “incidental.” In keeping with the precept that dementia is a clinical diagnosis, it is imperative to look at the patient, not just the scan.
Another possible finding on neuroimaging is hydrocephalus (increased cerebrospinal fluid in brain ventricles). In cases of dementia, this is commonly hydrocephalus ex vacuo (hydrocephalus occurring secondary to atrophy). Since nature abhors a vacuum, the fluid-filled ventricles expand to account for the loss of brain tissue. But again, this is a nonspecific finding that may occur with aging and is not sufficient for a diagnosis of dementia.
On the other hand, normal pressure hydrocephalus (NPH) is a specific type of hydrocephalus that can cause urinary incontinence, dementia, and gait problems and is treatable via neurosurgical placement of a shunt. This underscores why it’s important to do a brain scan: not to “see dementia” but to evaluate for other potentially treatable conditions, such as NPH or tumors, which can cause dementia or dementia-type symptoms.
Dementia can’t be diagnosed by brain scan alone. But neuroimaging may provide corroborating evidence for the diagnosis, exclude the diagnosis (e.g., if the scan uncovers a brain tumor or something else that may account for the patient’s symptoms), or help identify the type of dementia.
Functional neuroimaging includes functional MRI (fMRI), brain positron emission tomography (PET), and brain single-photon emission computed tomography (SPECT). fMRI is primarily used for research purposes. Lowered brain metabolism (hypometabolism) on PET or SPECT scans, as well as radioligand (radioactively labeled probes) studies on PET scans, may help in differentiating dementia types. However, these scans are expensive and not necessary for all patients.
PET offers the closest thing to “seeing dementia” in a living person. Radioligands may make visible some of the proteins that collect abnormally in the brain in dementia. PET scans are mainly done for research (e.g., studies investigating medications to treat these abnormal proteins) or in difficult-to-diagnose clinical cases, especially in patients under age sixty-five.
Myth #4: “You can’t diagnose Alzheimer’s disease while someone is alive”
Dementia, including Alzheimer’s disease, can be diagnosed during life—at least possible and probable Alzheimer’s disease. However, a diagnosis of definite Alzheimer’s disease requires postmortem confirmation by a brain autopsy (neuropathological evaluation).
Myth #5: Dementia is not treatable
Most dementias are treatable, although usually not curable or reversible. Current medications for dementia treat day-to-day symptoms and may slow cognitive, behavioral, and functional decline. In addition, behavioral and environmental interventions, brain therapy (adult day programs), planning, participation in research studies, support groups, and understanding the specific diagnosis and prognosis may make a world of difference for people with dementia and their families.
Some dementias are considered as potentially reversible (i.e., possibly curable). These are far and few between in real life but may make for a rich plot point in fiction. The mnemonic (memory prompt) that doctors sometimes use to remember the reversible dementias is
DEMENTIA:
Drugs (including certain medications and alcohol)
Endocrine (e.g., certain thyroid conditions) or metabolic (e.g., Wilson’s disease, which involves an overaccumulation of copper)
Mental illness (e.g., severe depression)
Eyes and ears declining
Normal pressure hydrocephalus or tumor or other “space-occupying” brain lesion
Toxins (e.g., excessive manganese in miners or bismuth overdose)
Infection (e.g., neurosyphilis)
Anemia (vitamin B12 or folate deficiency)
Timely medical evaluation is key in identifying any potentially reversible cause of dementia. Cognitive, behavioral, and functional symptoms can progress to a point of no return, even in a so-called “reversible” dementia. In fiction, this can serve as an important pacing device (the so-called “ticking time bomb”).