The uncertainty can be nearly as troubling as an older adult’s growing memory gaps, recent indecisiveness and odd behavior changes. It’s the limbo of wondering: Are these signs of dementia? Does the future hold Alzheimer’s disease?
Methods to diagnose Alzheimer’s disease earlier and more accurately keep emerging. One such test involves patients undergoing a spinal tap to provide a sample of cerebrospinal fluid, or CSF — the fluid that surrounds and protects the brain and spinal cord — for analysis.
Researchers, and potentially health care providers, can use these tests to detect key proteins associated with Alzheimer’s disease. The results can help either confirm an Alzheimer’s diagnosis or suggest that some other type of dementia or medical condition is causing a patient’s cognitive impairment and other worrisome symptoms.
[See: 10 Seemingly Innocent Symptoms You Shouldn’t Ignore.]
The Changing Alzheimer’s Arena
Biological markers of specific proteins known as amyloid and tau can be isolated in the cerebrospinal fluid. Those biomarkers may indicate that amyloid plaques and tau tangles — Alzheimer’s hallmarks — exist in the brain.
In the early 2000s, positron emission tomography, or PET scanning, made amyloid imaging possible in the brains of living people. More recently, it became possible to visualize tau infiltration, as well.
However, it’s not feasible for all older adults with potential signs of dementia to undergo a PET scan. Brain PET scans cost roughly between $3,000 and $5,000 per patient. Spinal-tap based testing for Alzheimer’s may offer an alternative or additional diagnostic tool.
Guidelines redefining Alzheimer’s diagnosis based on three biomarkers — amyloid plaques, tau tangles and deterioration of the nervous system — were published in the April 2018 issue of the journal Alzheimer’s & Dementia. For now, these guidelines are primarily for research purposes.
“The key advance that’s occurring in the field is we’re redefining Alzheimer’s disease as a biological disease caused by a pathophysiology, and with these biomarkers,” says guideline co-author Dr. Jason Karlawish, a professor at the Perelman School of Medicine at University of Pennsylvania and a co-director of the Penn Memory Center. “It holds promise for a more accurate diagnosis for the subset of people who have those biomarkers. It holds great promise for the development of treatments that can target those biomarkers.”
In July 2018, the U.S. Food and Drug Administration granted breakthrough designation to biomarker tests for Alzheimer’s disease using cerebrospinal fluid. These tests, developed by the Swiss biotech company Roche, were already approved in Europe.
In the U.S., it’s now likely that CSF testing for Alzheimer’s will move beyond the realm of research into clinical medicine and be used by doctors to diagnose or rule out Alzheimer’s disease and determine dementia treatment.
Spinal Tap Procedure
A spinal tap, or lumbar puncture, is a minimally invasive procedure. First, the lower back is numbed with a local anesthetic. The clinician inserts a thin hollow needle between two lumbar bones, or vertebrae, and withdraws a sample of cerebrospinal fluid.
A spinal headache, caused by leaking of fluid into nearby tissues, is the most common aftereffect of a spinal tap. About one-quarter of people who have spinal taps develop a headache that lasts a few hours, although some headaches may persist for several days following the procedure.
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To help ensure that spinal taps for CSF testing are used properly among patients who might have Alzheimer’s, a multidisciplinary group of experts developed a set of appropriate use criteria. These were published in the November 2018 issue of Alzheimer’s & Dementia.
Clarifying which patients should undergo a spinal tap to test CSF is a major issue addressed in detail in the criteria. How to relay the sensitive information from a patient’s test results is another important concern.
“There’s only one approved test available on the market at this point,” says Rebecca Edelmayer, director of scientific engagement at the Alzheimer’s Association. “But we anticipate there will be a number of diagnostic companies entering the market soon. (Although) the technology is not yet widely available for Alzheimer’s disease diagnosis, the Alzheimer’s Association and this work group of experts recommend that medical professionals do become familiar with these criteria now and anticipate using lumbar puncture and cerebrospinal fluid analysis in the near future.”
Alzheimer’s Possibility
Losing one’s train of thought, increasing forgetfulness, feeling overwhelmed by decision-making and depression are among the first symptoms that make people wonder whether they or loved ones may have Alzheimer’s disease.
Persistent decline in memory, an age of onset over 60, worries about cognitive decline and a feeling of worse performance than others in the same age group are features associated with increased Alzheimer’s risk.
Changes in behavior, such as paranoid delusions, unexplained delirium and combativeness are also Alzheimer’s symptoms. Family history of Alzheimer’s increases the risk of developing the disease.
Geriatricians, primary care physicians and nurse practitioners have multiple ways to evaluate an older patient for cognitive impairment or dementia. They routinely administer brief mental status exams including verbal questions and simple paper-and-pencil exercises to assess memory and thinking ability. Other tests measure a patient’s reflexes, movement, coordination and balance.
If Alzheimer’s or other dementia is suspected, patients might see a neurologist for evaluation. At that point, testing may include brain imaging like a PET scan. A spinal tap for CSF testing could become part of the clinical process to pinpoint Alzheimer’s in patients with signs of concern.
However, the presence of biomarkers does not always mean that a person will show Alzheimer’s symptoms. Conversely, not everyone with Alzheimer’s symptoms will have clear evidence of related biomarkers. Many factors and co-existing conditions can complicate a dementia diagnosis.
[See: 11 Things Seniors Should Look for in a Health Provider.]
Positive Test: Now What?
Unfortunately, there is no cure for Alzheimer’s disease. Drugs currently used to treat patients at different Alzheimer’s phases don’t stop the disease from progressing, although they may reduce cognitive symptoms for a limited time period. So, what tangible benefit is there in making an earlier Alzheimer’s diagnosis?
“There are broad reasons to diagnose a disease early,” Karlawish says. “One is so people know what’s up ahead in their own lives so they can make plans. Two, to explain the certain symptoms that you’re currently having and why you’re suffering. And three, to be able to get in treatment, whether that is pharmacologic or nonpharmacologic treatment, to try to improve your quality of life and ease your suffering.”
For people experiencing cognitive impairment and other distressing symptoms, Karlawish says, the role of a test like a spinal tap is to understand: “What’s the cause of my problem? What should I therefore expect in the future?”
Patients will handle the likelihood they have Alzheimer’s disease in different ways. “People have various reactions to information,” Karlawish says. “Some people are very information-seeking. Knowledge is power: It settles anxiety. Other people are just the opposite: That knowledge about something that’s quite stigmatizing, like Alzheimer’s, only escalates anxiety.”
Research Connection
The ability to participate in research is a practical reason for patients with suspected Alzheimer’s to undergo testing, along with other potential benefits. Study volunteers could be among the first to try a new, potentially effective drug or treatment.
“We really think that early and accurate diagnosis is critical for care of individuals living with dementia,” Edelmayer says. “Because as therapies become available, the appropriate use of lumbar puncture and cerebrospinal fluid analysis may give medical professionals and those living with dementia a head start in preparing for the course of the disease.”
Testing that enables an earlier, accurate diagnosis “can assure the high-quality care and treatment,” Edelmayer says. “It can facilitate the planning for the future and it also enables people to enroll in clinical trials at this early stage and introduce them to disease-modifying therapies that are now in development.”
For people interested in being matched to clinical trials, the Alzheimer’s Association TrialMatch site allows online access to learn about clinical trials available in the U.S. and potentially find a study that fits.
Who Should or Shouldn’t Be Tested?
According to the appropriate use criteria, a spinal tap for CSF analysis would be inappropriate for someone who has no cognitive impairment and who functions within normal range for his or her age, as established by objective testing. At the other end of the spectrum, it would be inappropriate to perform a spinal tap for CSF testing to determine disease severity on a patient who already has an established Alzheimer’s diagnosis.
“The biggest distinction for appropriate use and inappropriate use for this particular type of procedure is that there has to be some type of self-reported — or maybe your family or your clinician is reporting — what we would call subjective cognitive decline in the individual that is concerning,” Edelmayer says. “In addition, the individual should likely have a family history or increased risk of developing dementia.”
Such testing would not be meant for routine screening, but as an additional diagnostic tool for patients who need further evaluation, Edelmayer notes: “This is a tool that physicians will eventually be using to help patients get through a triage of testing that could not only be accurate but also cost-effective for the patient.”
Another recommendation is that testing be done by a dementia expert, Edelmayer says. That expert could better determine appropriateness in the first place, educate the family about benefits and risks and ensure the procedure is done according to established guidelines for lumbar punctures and CSF drawing.
“Most importantly,” she says, “the clinicians themselves — the dementia experts — are using the results to implement a treatment plan and integrate this information into (the plan) moving forward.”
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Using Spinal Taps to Reveal Alzheimer’s Disease Earlier originally appeared on usnews.com
