Cerebritis

What cerebritis is

When bacteria or fungi reach the brain, they first cause an area of poorly defined inflammation and swelling. This is early cerebritis (days 1 to 3) and late cerebritis (days 4 to 9). Over the following days, the body starts to wall off the infection, and a capsule forms around a central pocket of pus, creating a brain abscess (from about day 10 onward). At the cerebritis stage there is no capsule to drain, so treatment is mainly with antibiotics.

The word "cerebritis" is also used, less precisely, for inflammation of the brain from autoimmune disease, most commonly lupus cerebritis, a form of neuropsychiatric lupus.

Causes

Infectious cerebritis

Germs reach the brain by:

• spread from nearby infections: sinusitis, middle ear and mastoid infections (otitis media), and dental abscesses
• the bloodstream: from endocarditis, lung abscess, or congenital heart disease with right-to-left shunts
• direct entry: after penetrating head injury or brain surgery
• unknown source in some cases

Common organisms include streptococci, Staphylococcus aureus and anaerobic bacteria. In people with weakened immune systems (HIV, transplant recipients, chemotherapy), fungi, Nocardia and Toxoplasma are also possible.

Lupus and other autoimmune cerebritis

In systemic lupus erythematosus, antibodies, inflammation of small blood vessels and clotting can affect the brain. Other autoimmune causes include autoimmune encephalitis and vasculitis.

Symptoms

• headache, often the first and most common symptom
• fever, though not always present
• nausea and vomiting from raised pressure in the skull
• confusion, drowsiness or behavior change
• seizures
• weakness, numbness or speech difficulty depending on location
• vision problems
• stiff neck if the meninges are involved

Lupus cerebritis can cause headaches, seizures, psychosis, confusion, memory problems, mood changes and strokes, often during a lupus flare.

Cerebritis vs encephalitis vs brain abscess

Diagnosis

• MRI with contrast: the key test. Cerebritis appears as an area of swelling with patchy enhancement and no defined capsule. Diffusion-weighted imaging helps distinguish infection from tumor.
• CT scan when MRI is not available.
• Blood tests: blood count, inflammatory markers and blood cultures.
• Tests for the source: sinus and dental imaging, ear examination, echocardiogram for endocarditis, chest imaging.
• Lumbar puncture: often avoided if there is mass effect from swelling, because of the risk of brain herniation.
• Biopsy or aspiration if the cause is unclear.
• For lupus: autoantibodies, complement levels, MRI and sometimes spinal fluid analysis.

Treatment

Infectious cerebritis

• IV antibiotics that penetrate the brain, usually a combination such as a third-generation cephalosporin plus metronidazole, with vancomycin if Staphylococcus is suspected. Treatment is guided by cultures and typically lasts 6 to 8 weeks.
• Treating the source: sinus or ear surgery, dental extraction, treating endocarditis.
• Repeat MRI to confirm improvement and to check whether an abscess forms that may need drainage.
• Steroids to reduce dangerous brain swelling in some cases.
• Anti-seizure medicines when seizures occur.

Lupus cerebritis

• high-dose corticosteroids
• immunosuppressants such as cyclophosphamide, mycophenolate or rituximab
• anticoagulation if antiphospholipid antibodies cause clotting
• treatment of seizures and psychiatric symptoms

Complications and outlook

Without treatment, infectious cerebritis can progress to a brain abscess, cause brain herniation, ventriculitis or death. With early antibiotics, many patients recover fully, though some have lasting seizures or neurological deficits. Lupus cerebritis outcomes depend on lupus control and the extent of brain involvement, and many people improve with treatment.

Frequently asked questions

What is cerebritis?

Cerebritis is inflammation of a localized area of brain tissue. It is usually an early stage of a bacterial brain infection that can develop into a brain abscess. The term is also used for autoimmune brain inflammation, especially in lupus.

What causes cerebritis?

Infectious cerebritis is caused by bacteria or fungi reaching the brain from nearby sinus, ear or dental infections, through the bloodstream from conditions like endocarditis, or after head injury or surgery. Lupus cerebritis is caused by the immune system attacking the brain and its blood vessels.

What is the difference between cerebritis and a brain abscess?

Cerebritis is the early, poorly defined inflammation that comes first. A brain abscess forms over the next 1 to 2 weeks as the body builds a capsule around a pocket of pus. Cerebritis is treated with antibiotics. A larger abscess may also need surgical drainage.

What is lupus cerebritis?

Lupus cerebritis is an informal term for brain involvement in systemic lupus erythematosus. It can cause headaches, seizures, confusion, psychosis, mood changes and strokes. It is treated with steroids and immunosuppressive medicines, and blood thinners if clotting antibodies are present.

Can cerebritis be cured?

Infectious cerebritis can often be cured with several weeks of IV antibiotics, especially when treated early and the source is controlled. Some people have lasting effects such as seizures. Lupus cerebritis can usually be controlled with immune-suppressing treatment.