Scientists have discovered a new way to test for the presence of a fatal brain disease, CJD, which will allow doctors to detect the disorder far earlier than previous methods and with greater accuracy. The study has been published in the New England Journal of Medicine.
Cretutzfeldt-Jakob Disease (CJD) is a rare, fatal neurodegenerative disease caused by an unusual infectious agent called a prion. Prions are misfolded proteins that trigger normal, correctly folded counterpart proteins to also misfold, which are then strung together into long amyloid fibers. This misfolding spreads like wildfire across the brain, resulting in rapid disease progression.
Initial symptoms of CJD can be difficult to interpret. For example, sufferers may experience depression or personality changes. As the disease progresses and more of the brain becomes destroyed by this mass of misfolded proteins, other symptoms start to appear such as blindness and memory loss. By this stage, which is usually around 1 year after infection, death is imminent. The extent of damage by these protein aggregates is so severe that the brains of the deceased look like a sponge.
While the disease is incurable at present, early diagnosis can help prevent the spread of disease to others via exposure to spinal fluid and nervous tissue and also helps rule out other diseases with similar symptoms. The current diagnostic test, called RT-QulC, is invasive and involves removing cerebrospinal fluid (CSF) from patients and mixing it with normally folded proteins. If prions are present, they quickly cause these proteins to misfold and aggregate into insoluble amyloid fibers. This test has proved extremely useful in the past, but unfortunately it misses between 10-20% of cases.
The new test still relies on RT-QulC, but samples are taken from brushings of the very top of the nasal cavity where olfactory neurons, cells involved in our sense of smell, are found. When this technique was compared with the old method on the same patients, the researchers discovered that it was significantly more sensitive. More specifically, the new method identified 97% of cases, whereas the old method only picked up 77%.
While the new sample collection technique is likely to be uncomfortable and not without some pain, it is less invasive than removing CSF which is an added benefit to patients. Furthermore, since prions appear in olfactory neurons long before the CSF, this new technique should allow diagnosis at a much earlier stage.
As mentioned, since there is currently no cure for the disease, unfortunately earlier diagnosis is not going to improve patient outcome. However, it does reduce the chances of transmitting the disease to others, which is important.
[Header image "Prion Protein Fibrils," by NIAID, via Flickr, used in accordance with CC BY 2.0]