Heterogeneity of autoimmune encephalitis outlined to INA delegates

The guest lecture at the Irish Neurological Association (INA) Neurology Update meeting in Belfast was on the subject of autoimmune encephalitis.

The lecture was delivered by Prof Sarosh R Irani, who is head of the Oxford Autoimmune Neurology Group, and Co-director, Oxford Autoimmune Neurology Group, Diagnostic Laboratory.

Prof Irani is a Consultant Neurologist and clinician-scientist with clinical and laboratory experiences in the field of autoantibody-mediated diseases of the central nervous system. He runs a dedicated clinic for the care of these patients and runs a research group of 20 clinicians and scientists to learn more about the origins and treatments of these diseases.

According to Prof Irani, autoimmune encephalitis should be thought of as a heterogeneous range of disorders rather than a single disorder.

 Autoimmune encephalitis refers to a group of conditions that occur when the body’s immune system mistakenly attacks healthy brain cells, leading to inflammation of the brain. People with autoimmune encephalitis may have various neurologic and/or psychiatric symptoms. Neurologic symptoms may include impaired memory and cognition, abnormal movements, seizures, and/or problems with balance, speech, or vision. Psychiatric symptoms may include psychosis, aggression, inappropriate sexual behaviours, panic attacks, compulsive behaviours, euphoria, or fear.

In his talk, Prof Irani showed how the clinical features of autoantibody-mediated encephalopathies are distinctive.

For example, he spoke of how LGi1 autoimmune encephalitis is characterised by a number of frequent, multifocal seizure localisations with multiple semiologies, in addition to faciobrachial dystonic seizures and numerous subclinical seizures.

According to Prof Irani, the LGi1 and CASPR2 variants have strong human leucocyte antigen (HLA) associations.

He spoke of GABA_A and GABA_B receptor encephalitis, which is characterised by “complex partial seizures”, and amnesia and behavioural change. This type of autoimmune encephalitis is also associated with cancer.

Also, Prof Irani said patients with Iglon5-antibodies show a unique neuroimmunology-neurodegenerative interface.

The last condition described was NMDA receptor encephalitis, which occurs  when antibodies produced by the body’s own immune system attack NMDA receptors in the brain.

Prof Irani stated these patients have “a distinctive psychiatric syndrome (and movement disorder)” and that psychiatric symptoms manifest before people begin developing seizures.

Speaking to the Medical Independent (MI), Prof Irani explained how the diversity of the condition, which responds well to immunotherapy, came to be recognised.

“It started with one or two or three patients, when people spotted that patients who had an encephalitis in a certain form had a specific biomarker, which turned out to be causative. And people then said ‘this looks similar, this one looks similar, and this one looks similar, maybe they also have other autoantibodies’. So over the last 20 years, that has gone exponentially upwards in terms of numbers, each phenotype seems to be a little different to the next, although there are clear overlaps.”

Prof Irani said currently 14 types of the condition have been classified, but speculated this is likely to grow over the coming years.

“These are very treatable cases,” he said. “They tend not to do well with conventional treatments. But if you give them treatments which suppress the immune system, they do very well usually. Neurologists are very switched on and excited about developments in this area. I think the key is to do the same in general medicine because that is often where patients first turn up, or psychiatry, which is the other place where they first turn up. Those are the two specialties, if they can keep their eyes and ears open, it would make a big difference.”