vCJD has well defined and consistent clinical and pathological features that together make it relatively easy to identify and distinguish from sporadic CJD.11

Investigations carried out antemortem can be helpful in eliminating other possible psychological illnesses and neurological disorders that may be treatable. With tonsil biopsy as a probable exception, a definite diagnosis of vCJD requires pathological examination of brain tissue.

Antemortem testing

Magnetic Resonance Imaging (MRI) (link to definition in glossary): The MRI scan may show relatively specific changes that aid diagnosis, particularly in the case of vCJD.2 MRI identification of increased signal of a certain portion of the brain (bilaterally increased pulvinar signal) is a useful non-invasive test for the diagnosis of vCJD.12

Electroencephalogram (EEG): An EEG may show changes which often are detected in the most common subtypes of sporadic CJD and some subtypes of hereditary or iatrogenic CJD.2 Conversely, these changes have only been seen very rarely in cases of vCJD and only late in the clinical course.10

Lumbar puncture (Spinal Tap): The elevated presence of four “marker” proteins in the cerebrospinal fluid (CSF) called 14-3-3, tau, S100 and NSE is helpful in diagnosing most cases of sporadic CJD but is less reliable in diagnosing vCJD.13 Examination of CSF using other markers also is done to exclude other causes of the symptoms like inflammation or infection of the brain.2

Brain biopsy: The hallmark of vCJD in brain tissue is the presence of rounded deposits of abnormal proteins surrounded by vacuoles, called florid plaques or daisy plaques. Spongiform change is characteristic of both vCJD and sCJD. However, the lack of spongiform change on brain biopsy does not mean a negative diagnosis. Lack of spongiform change could mean the disease has not affected the part of the brain sampled. Brain biopsy is not done routinely because of risk to the patient and to the medical team performing the operation.2

Tonsil biopsy: Variant CJD, unlike classic CJD, can be diagnosed if a tonsil biopsy sample is positive for the abnormal prion protein (PrPSc).14 Variant CJD is the only type of prion disease in which a very highly reliable diagnosis can be made with a biopsy of the tonsils.11 However, concerns about potential complications associated with this invasive diagnostic procedure and the current limitations of vCJD therapy have reduced the use of this procedure.10

Postmortem testing

Postmortem testing of the brain is done in many countries’ prion surveillance centers, similar to the National Prion Disease Pathology Surveillance Center in the United States, that solicit brain tissue from deceased individuals suspected of dying from a prion disease. These laboratories perform three basic examinations to establish or exclude the diagnosis of a prion disease: histopathology, immunohistochemistry (IHC) and Western Blot. Gene analysis also is performed to determine the subtype of CJD present.

Histopathology: The brain of someone with any type of CJD nearly always shows signs of spongiform change; the brain tissue has the appearance of a sponge when seen under the microscope. In vCJD specifically, a particular and unique type of plaque known as a florid plaque is typical of the disease. The florid plaques are surrounded by an area of spongiform change.2

Immunohistochemistry (IHC): The presence and distribution of the abnormal PrP is established and correlated to that of the tissue lesions examined in the histopathology examination.2

Immunoblot/Western Blot: This technique can detect much smaller amounts of abnormal PrP than IHC and can establish which type (type 1 or 2) of the abnormal prion protein (PrPSc) is present in the affected tissue. It often is used in concert with IHC because it cannot establish the distribution of the abnormal prion proteins (PrPSc).2

Genetic analysis: In order to identify the subtype of CJD present, genetic analysis must be conducted to determine the normal prion protein (PrP) genotype. The presence of the codon for amino acids methionine (M) or valine (V) at position 129 of the human prion protein determines the subtype. All cases of variant CJD have shown the M/M subtype.2

There is no known effective treatment of vCJD, and it is invariably fatal.4

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