Medicare will start paying for specialized brain scans in some patients to help determine if they have Alzheimer's disease, the federal agency that runs the reimbursement program announced yesterday.
The decision caps a four-year struggle by makers of the technology -- known as positron emission tomography, or PET -- to gain approval from the Centers for Medicare and Medicaid Services for PET's use in patients suspected of having Alzheimer's disease.
But in the absence of convincing evidence that PET scans can, by themselves, tell whether a person has Alzheimer's, the agency settled on a much narrower application. It will reimburse for the brain scans only for patients whose Alzheimer's symptoms are not typical and who doctors believe may instead have one of several rare brain diseases known collectively as "fronto-temporal dementia. "
Those conditions -- the best known is Pick's disease -- generally occur at a younger age than Alzheimer's. They tend to first become apparent as behavioral changes and language difficulties rather than memory loss. Nevertheless, they can mimic Alzheimer's enough that distinguishing them can be difficult, and that can be important because these dementias tend to progress much more rapidly.
The decision memo from the centers said PET scanning is "reasonable and necessary" for patients who have shown mental decline for at least six months and for whom a diagnosis of either fronto-temporal dementia or Alzheimer's is still possible after a thorough examination. It added, however, that medical evidence does not justify using the expensive scans on people who simply have early dementia.
PET involves injecting radioactive chemicals that break down in the bloodstream over a period of hours. A scanner tracks them to identify areas where metabolic processes are out of balance.
The scans, which typically cost about $2,000, are covered by Medicare for use in spotting about a dozen kinds of cancer.
The agency had no immediate estimate yesterday of how many people might be eligible for the newly approved scans or what the annual costs will be.
Last year, the agency rejected efforts by PET scan manufacturers to gain Medicare coverage for the procedure as a general test for Alzheimer's. That diagnosis can be made with certainty only by examining the brain after death.
Although the agency determined that the technique might be more accurate than many doctors, who must make a diagnosis on the basis of symptoms, it also found that this modest advantage had little practical value. Patients diagnosed with probable Alzheimer's on the basis of symptoms are typically offered a prescription for one of the few approved medicines, which have been shown to delay slightly the disease's inexorable march.