- SymptomsChanges that progress quickly.
- Neurological examA specialist looks for other causes first.
- MRI and EEGBrain scan and brain wave test.
- Spinal fluid testsIncluding RT-QuIC, where available.
- Specialist reviewCriteria give a probable diagnosis.
- ConfirmationA definite diagnosis needs brain tissue, usually after death.
The order differs by hospital and country.
Most families reach this part of the site in the middle of the tests, when some results are back and others are not. The three pages below answer the three questions people ask most often.
- How prion disease is diagnosed walks through the usual order of events, from the first appointment to the specialist opinion.
- Tests explained takes each test one at a time and says what it involves and what it can show.
- Questions for your doctor is a short list you can take to an appointment.
Who makes the diagnosis?
A neurologist, a doctor who specialises in the brain and nervous system. The same tests that look for a prion disease also look for other conditions that can cause similar symptoms, some of which can be treated, so ruling those out is part of the work.
Because these illnesses are rare, local teams usually ask a national specialist service for an opinion. In the United Kingdom that is the National CJD Research and Surveillance Unit in Edinburgh and the National Prion Clinic in London. In the United States it is the National Prion Disease Pathology Surveillance Center, which runs the national reference laboratory. Help by country lists the centre for other countries.
What does a probable diagnosis mean?
You may see the words possible, probable or definite in a letter. They come from agreed international criteria that doctors use so cases are counted the same way everywhere.
Probable means the pattern of symptoms together with the test results fits a prion disease closely, and nothing else explains it. Definite is reserved for cases where brain tissue has been examined, which in practice usually means after death. A probable diagnosis is treated as the diagnosis for care, planning and support. It is not a lesser answer or a sign that doctors are unsure what to do next.
Why can the tests take time?
Spinal fluid and genetic samples are often sent to one national laboratory, which adds days to weeks. Scans may be repeated, because the changes a radiologist looks for can be clearer later than at the first scan. A second lumbar puncture is sometimes suggested when the first result was negative and the clinical picture still fits.
Waiting is one of the hardest parts of this, and you can ask at any point what is outstanding, who is waiting for it, and when the team expects to speak to you again.
Where to go next
Prion diseases explains the illnesses these tests are looking for. Understand and Care holds the pages on care, support and practical help.
Nothing on this page can tell you what one person’s results mean. That belongs with the neurologist who ordered the tests, and anything about a gene in the family belongs with a genetic counsellor.
Explore
- How prion disease is diagnosedThe usual order of events when doctors look for a prion disease: the first appointment, the scans, the spinal fluid test, the specialist opinion.
- Questions for your doctorQuestions families find useful to ask a neurologist about a suspected prion disease, covering tests, timing, specialist opinion and support.
- Tests explainedEach test used when doctors suspect a prion disease, what it involves for the person having it, and what it can and cannot show.