Creutzfeldt-Jakob Disease (cont.)
How is CJD Diagnosed?
There is currently no single diagnostic test for CJD. When a doctor suspects
CJD, the first concern is to rule out treatable
forms of dementia such as encephalitis (inflammation of the brain) or
chronic
meningitis. A neurological examination will be performed and the doctor may seek
consultation with other physicians. Standard diagnostic tests will include a
spinal tap to rule out more common causes of dementia and an
electroencephalogram (EEG) to record the brain's electrical pattern, which can
be particularly valuable because it shows a specific type of abnormality in CJD.
Computerized tomography of the brain can help rule out the possibility that the
symptoms result from other problems such as stroke or a brain tumor. Magnetic
resonance imaging (MRI) brain scans also
can reveal characteristic patterns of brain degeneration that can help diagnose
CJD.
The only way to confirm a diagnosis of CJD is by brain biopsy or
autopsy. In a brain biopsy, a neurosurgeon removes a small piece of tissue from the
patient's brain so that it can be examined by a neuropathologist. This
procedure may be dangerous for the patient, and the operation does not always
obtain tissue from the affected part of the brain. Because a correct diagnosis
of CJD does not help the patient, a brain biopsy is discouraged unless it is
needed to rule out a treatable disorder. In an autopsy, the whole brain is
examined after death. Both brain biopsy and autopsy pose a small, but definite,
risk that the surgeon or others who handle the brain tissue may become
accidentally infected by self-inoculation. Special surgical and disinfection
procedures can minimize this risk. A fact sheet with guidance on these
procedures is available from the NINDS and the World Health Organization.
Scientists are working to develop laboratory tests for CJD. One such test,
developed at NINDS, is performed on a person's cerebrospinal fluid and
detects a protein marker that indicates neuronal degeneration. This can help diagnose CJD
in people who already show the clinical symptoms of the disease. This test is
much easier and safer than a brain biopsy. The false positive rate is about 5 to
10 percent. Scientists are working to develop this test for use in commercial
laboratories. They are also working to develop other tests for this disorder.