The Generative Brain

Rapidly progressive dementia and CJD

More detail

Rapidly progressive dementia means thinking and memory declining over weeks to months rather than years. CJD is one of the causes doctors look for, and so are infections, autoimmune conditions, vitamin problems and cancers, some of which can be treated. That is why so many tests are done before anyone settles on a diagnosis.

How changes in the brain can show up
  1. 1Front of the brainThinking, planning, personality and mood
  2. 2Side of the brainMemory and finding words
  3. 3Deep centre, the thalamusSleep and body rhythms
  4. 4Back of the brainSight
  5. 5CerebellumBalance and coordination

A simplified picture. Prion disease can affect many areas, and which come first differs by person and by type of disease.

Families often meet this phrase in a hospital corridor, usually alongside the letters CJD, and it sounds like a diagnosis. It is not one. It is a description of how fast things are changing, and it is the reason for the long list of tests.

What does the phrase mean?

Dementia that develops over weeks to months, occasionally days, instead of the years that most dementias take. Doctors use the term to flag that someone needs to be assessed quickly, usually in hospital, because some of the conditions that cause it can be treated.

Why is CJD mentioned so early?

Because prion disease is one of the best known causes of this pattern, particularly when there are also problems with balance, coordination or movement alongside the memory and thinking changes.

Mentioning it is not the same as diagnosing it. Specialists describe CJD as high on the list to be considered, which means it has to be tested for and either confirmed or excluded.

What else can cause it?

A long list, which doctors group by type: problems with blood vessels, infections, toxic and metabolic causes, autoimmune conditions, cancers, side effects of treatment, other degenerative brain diseases and conditions affecting the whole body.

Some of those are treatable, and some are reversible. Low vitamin B12, thiamine or niacin, thyroid problems, autoimmune inflammation of the brain, certain infections and some cancers all appear on the list, and each has its own treatment.

A specialist centre in the United States reviewed around 825 people referred to it over five years with rapid decline, most of them with a presumed diagnosis of CJD. Just over half turned out to have prion disease. Around 18 in every 100 had a different condition, many of which were treatable, and in about 28 in every 100 the records were not sufficient to reach a conclusion. The treatable group is the reason nobody should stop testing early.

Why are there so many tests?

Because the conditions on that list are told apart by different tests, and because some of the tests used for CJD are not reliable enough on their own.

In the series above, the spinal fluid marker 14-3-3 had a sensitivity of 48 percent and a specificity of 66 percent, and the EEG picked up fewer than 45 in 100 cases on first testing. Newer tests, including the spinal fluid seeding test RT-QuIC and MRI read by someone experienced in prion disease, perform much better, and they are still interpreted alongside everything else. How prion disease is diagnosed sets out the current tests.

The same assessment also screens for the treatable causes: blood tests including vitamin B12, thyroid antibodies, tests for infections such as HIV and syphilis, imaging of the body as well as the brain, and in some cases specialist antibody tests on blood and spinal fluid.

What can we do while we wait?

Ask who is coordinating the tests and what the next one is for. Ask whether the case has been discussed with a national prion centre or a specialist dementia service, since this is a situation where second opinions are normal rather than a sign of mistrust.

Symptoms can be treated while the cause is still being worked out, and published guidance recommends involving a palliative care team early rather than waiting for a confirmed diagnosis. That is not a sign anyone has given up. What to expect covers the practical side, and support groups lists people who can talk with you now.

One worry is worth answering plainly: there is no evidence that CJD passes from person to person through ordinary social or clinical contact, and caring for someone at home needs no special precautions.

Where next?

Rapidly progressive dementia and CJD: more detail is the clinical version, with the full differential and the test figures. The suspected case pathway is written for clinicians, sporadic CJD covers the commonest prion disease and how prion disease progresses what follows a diagnosis.

Nothing here describes a particular person, and no test figure on this page says anything about one individual’s results. Questions about what is being tested and why belong with the treating team.

Sources for this page