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.