The most common presenting sign is seizures. The seizures are most commonly focal in nature (i.e. only affecting certain areas of the body) and are characterised by licking and chewing movements (called “orofacial automatisms”), hypersalivation, dilated pupils and disorientation.  In some cats, the seizures are generalised and so affect the whole body, with collapse on to the side and rigid extension of the legs with paddling movements. Another seizure type is “circling seizures”, in which cats perform a circling motion, often combined with behaviour change and disorientation.

Other signs can include altered behaviour such as aggression, anxiety and/or seeking out comfort from the owner. Less commonly we can see confusion, increased sleepiness and altered urination habits.

Our experience to date suggests that the outcome is very variable. In some cats, the seizures are well controlled with phenobarbital medication and these cats go to lead a normal life.  Sadly, in some cats, the seizures prove to be extremely difficult to control despite multiple medications. We don’t yet know how to predict which cats will do well with treatment and which won’t, but a prompt response to initiation of treatment is encouraging.  We also hope that with improved understanding of this disease and how best to treat it, more cats can be effectively treated.

Our study looks at one association in feline autoimmune encephalitis, antibodies to a brain protein called leucine-rich glioma-inactivated 1 (LGI1). Antibodies are immune proteins which normally are involved in the body’s response to infection, but in autoimmune disease can be directed against our own tissues. LGI1-antibodies are established as a cause of autoimmune encephalitis in humans, where the hallmark symptoms are seizures, behaviour change, and memory loss or cognitive problems.

As yet the risk factors in cats are unknown. In humans, there are some genetic associations that increase the risk for this form of autoimmune encephalitis, but we do not know if this is the case in cats.

We and others have found that the typical age for this form of AE in cats is young adults, around four years old, although it can be found in all ages.

We typically focus treatment on reducing the frequency and severity of further seizures.  Phenobarbital, an antiseizure medication commonly used in animals with epilepsy, is our first line treatment. It is given orally twice daily and requires periodic blood tests to ensure it is at a safe concentration within the blood.  Phenobarbital might be used in combination with levetiracetam (another antiseizure medication, but it requires administration three times daily) if the seizures are frequent or difficult to control.

In some cats we additionally prescribe steroid medication as this has been shown to help in people affected by the same condition. This is also administered orally and is given once or twice daily.

Generally, once started on antiseizure medications these are continued lifelong.  In occasional cases (for example, if there has been multiple years since the last seizure) we might attempt to reduce or stop the antiseizure medications, but this always carries a risk of the seizures recurring.

In cats receiving steroid medication our goal is to slowly reduce the dose over time and eventually stop administration all together. Steroid medication can have lots of side effects and so we aim to reduce the dose promptly to minimise these side effects.

So far, this form of autoimmune encephalitis is not linked to specific breeds. Most cats in published studies are domestic short hair, which mirrors the overall population of cats.

Some cats show a very good response to treatment, with no further seizures and resolution of any documented behavioural changes. However, in other cats, the seizures can continue or they can experience relapse and we work to try minimise the frequency and severity of these ongoing seizures. As we are still early on in our understanding of this disease we don’t yet have large studies on the long term outcome of cats with autoimmune encephalitis but this is something we are working on.

Yes, affected cats can have an excellent quality of life after autoimmune encephalitis.  Many will require ongoing medication and occasional check ups with the vet, but overall we hope they can lead a relatively normal life.

This is an area we are working on. In humans, we know that antibodies can persist even after the acute disease and symptoms have resolved.

Our study (Royal Veterinary College ethics URN 2025 2390-A) accepts samples of cats with seizures and/or behaviour change submitted by veterinary surgeons. All samples must be residual from those taken for needed veterinary care. If you are concerned about these symptoms in your cat, please discuss with your vet and they can liaise with us to arrange testing if they think it is appropriate. Full details of how to submit a sample are here.

We also have owner-focussed research studies ongoing. These include quality-of-life questionnaires and microbiome collection. If you are interested in taking part in these studies please contact us.