Autoimmune encephalitis isn’t something most people have heard of-until it hits close to home. It’s not a stroke, not a virus, not a typical brain infection. It’s when the body’s own immune system turns on the brain, attacking neurons and causing confusion, seizures, memory loss, and sometimes even catatonia. The good news? If caught early, it’s often treatable. The bad news? It’s easily missed. Symptoms start slowly, like a bad flu or a mood swing, and by the time doctors suspect it, precious time has passed.

What Are the Real Red Flags?

You might think of encephalitis as a feverish, confused patient with a stiff neck. That’s infectious encephalitis, usually from viruses like herpes. Autoimmune encephalitis looks different. It creeps in over days or weeks, not hours. The first signs? Often, they’re psychiatric. Someone becomes paranoid, aggressive, or withdrawn-like a personality change no one can explain. Or they start having unexplained seizures, especially if they’ve never had them before. Memory problems come fast: forgetting names, losing track of conversations, repeating questions. These aren’t normal forgetfulness. They’re sharp, sudden, and getting worse.

Other red flags include:

• Changes in heart rate or blood pressure-sudden spikes or drops without obvious cause
• Severe insomnia or sleeping 16 hours a day
• Faciobrachial dystonic seizures: brief, repetitive jerks in the face and arm, often happening dozens of times a day
• Low sodium levels in the blood (hyponatremia), causing nausea, confusion, or weakness
• Flu-like symptoms a week or two before neurological issues start: headache, fever, diarrhea

These aren’t random. They’re patterns. A 2025 study of over 200 patients found that 85% had memory issues, 63% had sleep problems, and 42% had autonomic dysfunction. If someone has even two of these symptoms-especially seizures plus memory loss-autoimmune encephalitis needs to be ruled out. Don’t wait for a diagnosis. If suspicion is high, start treatment while waiting for test results. Every day matters.

Which Antibodies Are Behind It?

There are more than 20 known antibodies linked to autoimmune encephalitis. They’re like fingerprints-each one tells you something about the disease, who’s likely to get it, and what might be causing it.

Anti-NMDAR is the most common, making up about 40% of cases. It hits young people, especially women in their 20s. Half of these cases are tied to ovarian teratomas-tumors that can be removed surgically. Once the tumor’s gone, the brain often starts healing. But even without a tumor, this type responds well to immunotherapy.

Anti-LGI1 affects older men, mostly over 60. It’s known for those tiny, frequent facial and arm jerks (faciobrachial dystonic seizures). Almost two-thirds of patients have low sodium. Recovery is good-55% fully recover within two years-but it comes back in about one in three cases.

Anti-GABABR is rare but dangerous. Half the people with this antibody have small cell lung cancer. If the cancer isn’t found and treated, the brain won’t recover. This one needs aggressive cancer screening.

Less common antibodies include anti-CASPR2, anti-AMPAR, and anti-IgLON5. Each has its own pattern. Anti-GFAP, for example, often causes swelling in the spinal cord too. Testing for these isn’t simple. You need both blood and spinal fluid. CSF is more sensitive-up to 20% more likely to catch the antibody than blood alone. If you test only serum and it’s negative, don’t rule it out. Repeat the test with CSF.

How Is It Diagnosed?

There’s no single test. Diagnosis is a puzzle. Doctors look at symptoms, brain scans, spinal fluid, EEGs, and antibody results together.

MRI scans can be normal in up to half of cases. When they do show something, it’s usually mild swelling in the temporal lobes-the memory centers. That’s called limbic encephalitis. It’s a big clue. Infectious encephalitis, by contrast, shows widespread damage in 89% of cases.

EEGs often show slow brain waves, not the sharp spikes seen in viral infections. That’s a subtle but important difference.

Spinal fluid analysis is critical. In autoimmune encephalitis, white blood cell counts are usually under 100 per microliter. In infections, they’re often in the hundreds or thousands. Protein levels are only mildly elevated. Oligoclonal bands? Usually absent. These details help rule out MS or infections.

The 2023 diagnostic criteria from the International Autoimmune Encephalitis Consortium are the gold standard. They require:

• Subacute onset (under 3 months)
• At least two of: new seizures, psychiatric symptoms, memory loss, altered consciousness, or movement disorders
• Exclusion of other causes
• Positive antibody test or typical MRI/CSF findings

If you meet the criteria and have a known antibody, the diagnosis is definite. If you don’t have the antibody but have the symptoms and CSF/MRI findings? Still probable. Don’t wait for perfect proof. Start treatment.

What Are the Treatment Options?

Treatment is tiered. First-line, second-line, then third-line. The goal: shut down the immune attack fast.

First-line therapy is usually high-dose steroids-1 gram of IV methylprednisolone daily for five days. It’s given in the hospital. About 68% of patients improve within a week or two. IV immunoglobulin (IVIg) is often given at the same time: 0.4 grams per kilogram of body weight daily for five days. It works in 60-70% of cases.

But here’s the key: If there’s a tumor, remove it first. In anti-NMDAR encephalitis, 85% of patients improve after ovarian teratoma removal. In anti-GABABR, finding and treating lung cancer is life-saving. Screening must be thorough-pelvic ultrasound, CT chest/abdomen/pelvis. Repeat it in 4-6 months. 15% of tumors show up later.

Second-line kicks in if first-line fails. That happens in 30-40% of cases. Rituximab (given weekly for four weeks) helps 55% of patients. Cyclophosphamide (monthly for six months) helps 48%. Tocilizumab, a newer drug, shows 52% response in resistant cases.

Plasma exchange is used for the sickest patients-those in ICU with seizures or breathing problems. Five to seven sessions over two weeks can stabilize them fast. It clears antibodies out of the blood quickly.

Timing is everything. Patients treated within 30 days of symptoms have a 78% chance of good recovery. If treatment is delayed beyond 45 days, that drops to 42%. Dr. Josep Dalmau, who discovered anti-NMDAR encephalitis, says: “Every day counts.” Don’t wait for antibody results. If the clinical picture fits, start treatment now.

What Happens After Treatment?

Recovery isn’t instant. Even after the immune attack stops, the brain needs time to heal. About 55% of anti-LGI1 patients fully recover in two years. For anti-NMDAR, it’s 45%. But 40% of survivors have lasting problems.

The most common long-term issues:

• Cognitive: Memory loss, trouble focusing, slow thinking (32%)
• Psychiatric: Depression, anxiety, mood swings (28%)
• Seizures: Needing ongoing anti-seizure meds (22%)

Rehabilitation makes a difference. Twelve weeks of cognitive therapy improves memory in 65% of patients. SSRIs help 70% of those with depression. Physical therapy improves movement in 50% of people with motor issues within eight weeks. Sleep problems? Melatonin (3-5 mg at bedtime) helps 60%. For fast heart rate, beta-blockers work in 75% of cases.

Recurrence is real. Anti-NMDAR comes back in 12-25% of cases, usually within a year. Anti-LGI1 recurs in 35%-often without warning. Long-term follow-up every 3-6 months for two years is essential. Watch for subtle changes: forgetfulness, irritability, new twitching.

What’s Next in Research?

The field is moving fast. Scientists are now tracking GFAP-a protein released when brain cells are damaged. Blood levels of GFAP correlate with disease activity in 82% of cases. It might one day replace spinal taps for monitoring.

New drugs are in trials. B-cell depletion therapies and complement inhibitors are showing 60% response in patients who didn’t respond to anything else. These could change the game for those with refractory disease.

The biggest takeaway? Autoimmune encephalitis isn’t rare. It’s underdiagnosed. If someone you know has a sudden, unexplained change in behavior, memory, or movement-especially with seizures or low sodium-push for testing. Don’t let it be labeled as psychiatric or ‘just stress.’ The brain is sick. And with the right treatment, it can heal.