In health, the blood brain barrier (BBB) prevents dangerous “players” traveling in the blood from reaching the protected space of the brain. Many inflammatory brain diseases are associated with preceding viral or bacterial infection, autoimmune processes, and/or their impact on the integrity of the blood brain barrier. Some people also have underlying risk factors for infectious or autoimmune inflammation.
Causes of brain inflammation
Inflammation occurs as a natural response to an infection or when body tissues are injured. Inflammatory processes, however, can run afoul and begin to attack the body’s own cells. Chronic inflammation that persists after an infection goes away or that arises without an obvious trigger may be due to autoimmunity. In some people this process is persistent and in others it can come and go.
The brain is usually kept safe from infection due to the blood brain barrier, or BBB. However, if the BBB is compromised, antibodies, white blood cells, or inflammatory products of white blood cells may cross into and injure or irritate various regions of the brain.
Risk factors of brain inflammation
- Chronic inflammation is often related to genetics or environmental determinants. Indeed, the interaction of several different risk factors likely contribute to inflammatory brain disorders and include the following:
- Genetics – certain genetic mutations can contribute to the dysregulation of the immune function or mental health propensities..
- Infections – exposure to certain infections trigger the immune system and can potentially initiate or exacerbate an autoimmune reaction.
- Stress –chronic stress can lead to immune system dysfunction, contributing to a persistent low-grade inflammation associated with cognitive, behavioral, and emotional changes; acute stress can also lead to increased inflammatory activity.
- Maternal/paternal influence – environmental factors during pregnancy and early life—such as exposure to inflammation in utero or infancy—may affect how different genes from both father and mother are expressed. Breastfeeding is felt to alter the types of bacteria living in a person’s gut, possibly changing how their immune system reacts to perceived threats lifelong.
- Injury and aging – Injury to the head can trigger proinflammatory mechanisms that compromise the brain’s stability. Aging brains may suffer from chronically increased levels of proinflammatory cytokines .
- Tumors – an immune response against some tumors (benign or malignant) can generate antibodies directed against neuronal cells, which contribute to a condition called autoimmune encephalitis.