Inflammation in the brain: from brain fog to autoimmune encephalitis

When we think about inflammation, we usually picture a swollen joint or an irritated gut. But the brain can become inflamed too — and it doesn’t have pain receptors the way your knee does, so it rarely announces itself with an ache. Instead, brain inflammation tends to show up as how you think and feel.

Inflammation doesn’t stop at the neck

The immune system and the nervous system are in constant conversation. When the immune system is activated — by an infection, a food sensitivity, a toxic exposure, blood-sugar swings, or ongoing stress — that signal reaches the brain too. The result is neuroinflammation: immune activity in the brain that, at lower grades, doesn’t look like a disease on a scan but absolutely affects how you function.

In practice, this is the far more common picture. It tends to feel like:

None of this requires a hospital. But it’s real, it’s often driven by things we can identify and change, and it responds well to a root-cause approach.

What drives brain inflammation

The everyday version rarely has a single cause. More often it’s a stack of drivers — the same ones behind inflammation elsewhere in the body. The big ones we look for:

• Gut health. A big share of the immune system lives in the gut, and the gut–brain axis carries those signals north. Dysbiosis and a permeable gut lining are common contributors. (See SIBO and prebiotics.)
• Blood-sugar swings. Spikes and crashes are inflammatory and hit the brain hard — a common, fixable source of fog and mood dips.
• Toxins and mold. Mold and mycotoxin exposure is a frequently missed driver of neuroinflammation. (See mold & mycotoxins.)
• Chronic or hidden infections. Lingering viral or bacterial infections can keep the immune system — and the brain — on alert.
• Chronic stress. Ongoing stress keeps inflammatory signaling switched on and shapes how genes are expressed. (See the power of epigenetics.)
• Whole-body inflammation. When the whole system is inflamed, the brain rarely escapes it. (See chronic inflammation.)

What can help calm it

Because the drivers are largely identifiable, lower-grade neuroinflammation is often very workable. The approach mirrors calming inflammation anywhere: find the inputs and change them. That usually means an anti-inflammatory way of eating, steadying blood sugar, restoring the gut, removing toxic exposures, addressing infections, and protecting sleep and stress recovery. It’s rarely one silver bullet — it’s the stack of small corrections that lets the brain settle.

The severe end: autoimmune encephalitis

At the far end of the spectrum sits autoimmune encephalitis. It’s rare and very different in kind from everyday neuroinflammation — but it’s worth understanding, both because it shows how far immune–brain interactions can go and because recognizing it early genuinely matters.

Autoimmune encephalitis is a serious autoimmune condition in which healthy brain cells are attacked by the immune system’s antibodies, which improperly identify the body’s own cells as external invaders. It is inflammation in the brain caused by those attacks, which may also target the spinal cord.

This disease has been recognized relatively recently, and in some cases has been associated with ovarian tumors. Because of its recency — and the already complex nature of autoimmune disease — it can be difficult to diagnose and treat. But it is not rare by any means among neurological conditions, and new research is emerging rapidly.

It most commonly affects people between 13 and 50, often occurs in younger people, and is generally found in women more than men. Each year, it affects roughly 10–15 people per 100,000. You may be more at risk if you have a family history of autoimmunity, so it’s worth knowing your family health history and watching for symptoms.

What causes autoimmune encephalitis?

Previously, infections appeared to be the most commonly known cause — including viruses carried by insects such as mosquitoes and ticks.¹ Examples include West Nile, Zika, the La Crosse virus, and St. Louis virus. It could also be triggered by exposure to streptococcus and herpes simplex.² However, within the past 20 years, our understanding of the neuroglial antibody targets involved has shifted dramatically.³

Types of autoimmune encephalitis

There are at least 11 recognized types, each defined by the specific antibody involved and the part of the brain it targets — which is why presentations vary so widely.⁴ The best known is anti-NMDA receptor encephalitis, which most often affects children and young adults, begins with flu-like symptoms, and progresses quickly.⁵ The individual antibody names mostly matter for the diagnosis and treatment decisions your medical team will make; the useful takeaway is that this is a real, recognized, and often treatable category of brain inflammation — most types improve substantially with prompt immunotherapy.

Symptoms to watch for

Because there are so many types, symptoms vary — but many overlap. Common signs include:

• Cognitive impairment — e.g. a sudden decline in work or academic ability
• Psychosis — hallucinations, disorientation, confusion, euphoria, fear
• Headaches, seizures, and memory impairment
• Panic attacks and loss of mobility (e.g. poor balance)
• Sudden changes in behavior — compulsivity, inappropriate behavior

Treatments available

Prompt immunotherapy is key to managing many types of autoimmune encephalitis.⁶ Immunotherapy is actually a type of cancer treatment, but because it works to rebuild the immune system, it also helps here — it uses the body’s own immune cells to bolster its defenses.

Alongside immunotherapy, first-line treatments include IV steroids, corticosteroids (an immunosuppressant that prevents the immune system from making additional harmful autoantibodies), IV immunoglobulin, and plasma exchange. Second-line treatments include rituximab (antibody infusion) and cyclophosphamide, a chemotherapy drug that slows the growth of immune-system cells. Other treatments suppress the immune system or target specific cells in different ways. The best, most personalized plan comes from discussions with your healthcare provider.

Where functional medicine fits

Functional medicine focuses on addressing the root cause of a disease, taking a holistic view of a patient — physical, mental, emotional, and sometimes spiritual health. We may look closely at sleep, exercise, nutrition, and other factors in your life.

While it’s important to also pursue medical treatment, functional medicine can be a helpful partner in supporting people with autoimmune disease. At Genesis Functional Wellness, we investigate the underlying dysfunctions behind your symptoms and take a full view of your health through customized testing and more. (You can read more about how the pieces connect in a tangled mess and how to calm the fire of chronic inflammation.)