An illness that looks like sudden psychosis can be the immune system attacking the brain
It often starts like flu, then turns into hallucinations, paranoia and confusion, so doctors frequently mistake it for a psychiatric disorder. Only named in 2007, anti-NMDA receptor encephalitis is caused by antibodies against a key brain receptor, and in about half of cases an ovarian tumour sets it off.
The Spanish neurologist Josep Dalmau first described the condition in 2007. It strikes roughly one person in 1.5 million each year, about 80 percent of them female, usually adults under 45, though any age can be affected. Among disorders triggered by tumours, it is relatively common.
The attack is autoimmune. Antibodies target the GluN1 part of the brain's NMDA receptors. Teratomas, ovarian tumours that can contain many tissue types including nerve cells, seem to provoke the immune system into making antibodies that then cross-react with the same receptors in the brain. In children, a previous herpes infection of the brain is linked to more than half of known cases, while other patients have no obvious trigger. Antibody levels in the blood run about ten times higher than in spinal fluid, suggesting they are made in the body and slip into the brain, perhaps through a blood-brain barrier weakened by inflammation.
The illness unfolds in stages. Weeks or months of headache or a flu-like spell may come first. Behaviour then changes: agitation, delusions, psychosis, sometimes violence. Odd movements, especially of the lips and mouth, and leg motions like pedalling can appear, along with memory and speech problems. Later come seizures, unstable heart rate and blood pressure, shallow breathing and sometimes catatonia, and most patients at this stage need intensive care. A hallmark is the pile-up of symptoms; most people have at least four and many six or seven.
Because the early picture is psychiatric and brain scans often look normal, misdiagnosis is common. Diagnosis relies on detecting the specific antibodies in spinal fluid. Treatment uses drugs that suppress the immune system, plus surgery when a tumour is present. About 80 percent of patients do well, with better results the earlier treatment starts, although lasting mental or behavioural effects can remain. Around 4 percent die, and roughly 10 percent relapse.
Source: Anti-NMDA receptor encephalitis
