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A diagnosis of Creutzfeldt-Jakob disease (CJD) is usually based on medical history, symptoms and a series of tests.

A neurologist (a doctor who specialises in conditions of the nervous system) will carry out the tests to rule out other conditions with similar symptoms, such as Alzheimer's diseaseParkinson's disease, or a brain tumour.

The only way to confirm a diagnosis of CJD is to examine the brain tissue by carrying out a brain biopsy or, more commonly, after death in a post-mortem examination of the brain.

Specialist services at the National CJD Research and Surveillance Unit in Edinburgh and the National Prion Clinic in London advise local teams when making a diagnosis.

A clinical neurologist will rule out other conditions with similar symptoms.

They'll also check for some common signs of CJD by carrying out the following tests:

  • an MRI brain scan – uses strong magnetic fields and radio waves to produce a detailed image of the brain, and can show up abnormalities particular to CJD
  • an EEG – records brain activity and may pick up abnormal electrical patterns seen in sporadic CJD
  • a lumbar puncture – a procedure where a needle is inserted into the lower part of the spine to draw out a sample of cerebrospinal fluid (which surrounds your brain and spinal cord) so it can be tested for a certain protein that indicates you may have CJD
  • a prototype blood test for variant CJD has also been developed by the prion unit at the Medical Research Council (MRC) and is available through the National Prion Clinic
  • tonsil biopsy – a small piece of tissue can be taken from the tonsils and checked for the abnormal prions found in variant CJD (they're not present in other types of CJD)
  • genetic test – a simple blood test to find out whether you have a mutation (fault) in the gene that produces normal protein; a positive result may indicate familial (inherited) prion disease

During a brain biopsy, a surgeon drills a tiny hole into the skull and removes a small piece of brain tissue using a very thin needle.

It's carried out under general anaesthetic, which means the person will be unconscious during the procedure.

As a brain biopsy carries the risk of causing brain damage or seizures (fits), it's only performed in a few cases where there's a concern that someone doesn't have CJD but some other treatable condition.