Biofluid biomarkers are tests that determine the specific cause of Frontotemporal degeneration (FTD) during life. Disease-modifying treatments are being rapidly emerging, and clinical trials to assess these potential treatments are proceeding. These treatments are targeting specific proteins such as tau and TDP-43 that are accumulating in the brain and causing FTD. In order to administer these potential treatments to the appropriate patients, it is necessary to know which specific protein is causing the disease in individual patients. Likewise, it is important to know whether the brain is responding to the treatment with a decrease or change in the level of the abnormal protein in the brain.
An alternative is to develop a test that reflects pathologic changes in the brain. Perhaps the best kind of test examines cerebrospinal fluid (CSF). CSF circulates and bathes the brain and spinal cord, and thus may contain these specific, abnormal proteins that are accumulating in the brain and causing the pathologic changes. The CSF is obtained by performing a lumbar puncture (also known as a spinal tap). A lumbar puncture is performed in the lower back at a level that is below the spinal cord in order to minimize any risk of injuring the spinal cord. This procedure is identical to an epidural that is performed to administer anesthesia during childbirth and other procedures. After local anesthesia is applied, one to two tablespoons of fluid are collected, and this fluid replenishes itself very quickly (we make three times that amount of CSF contained inside and around our brain and spinal cord every day). This painless and minimally invasive procedure provides very accurate tests that are available to distinguish FTD from Alzheimer’s disease, and other tests are being developed to distinguish between the various abnormal proteins that cause different forms of FTD, ALS and related conditions.
Another alternative is to develop a blood test. While this is even less invasive than a lumbar puncture, a blood test is much more difficult to develop because of all of the various processes that are occurring in the rest of our body that are unrelated to the brain changes; however, some tantalizing preliminary results suggest that we may be able to develop a blood test for FTD in the near future.