Why does one person develop memory problems while another experiences seizures or changes in behaviour? And how do doctors find out whether these symptoms are caused by Alzheimer’s disease, an immune disorder or something else?
These clues, called chemical signatures or biomarkers, are being studied to improve the diagnosis of several diseases, particularly those affecting the brain and nervous system. The challenge is to establish what these changes mean, how reliably they point to a particular disease and whether patients can access the tests. In Alzheimer’s disease, for instance, doctors and researchers look for changes in proteins called amyloid-beta and tau . Certain forms of these proteins can be measured in blood and cerebrospinal fluid, the liquid surrounding the brain and spinal cord. Tests measuring phosphorylated tau, particularly p-tau217, can help identify changes associated with Alzheimer’s disease. Researchers are also studying alpha-synuclein, a protein associated with Parkinson’s disease. In another condition, autoimmune encephalitis, tests that detect antibodies directed against particular brain proteins can help identify an immune response affecting the brain. This condition can cause seizures, memory problems and changes in behaviour. Chemical signatures can also help distinguish conditions that appear similar. Identifying specific antibodies can help doctors recognise the condition and begin appropriate treatment. Mehta’s Hospitals, Chennai. Selected molecular tests are already used in specialist practice. Researchers are also studying markers such as neurofilament light, a protein that can indicate damage to nerve cells, he adds. Cost and availability pose further challenges in India. Specialised tests may not be offered at every hospital, and patients may have to travel to larger centres to access them. Differences in laboratory methods can also affect how consistently results are interpreted.
Because it can cause behavioural changes and problems with memory, autoimmune encephalitis, for example, may initially be mistaken for a psychiatric illness. 57 million people worldwide were living with dementia in 2021, with Alzheimer’s disease accounting for an estimated 60% to 70% of cases, according to the World Health Organization. The WHO also estimates that nearly 10 million new cases of dementia occur each year.
“In neurosurgery, examining the molecular characteristics of a brain tumour can help doctors classify it and decide on treatment,” says Aqib M., senior consultant neurosurgeon, Dr.
