Confusion is a common enough symptom in clinical practice. Often, it can be attributed to systemic conditions, such as medication side effects or infection. Occasionally however, one can be caught out in a situation where a patient develops confusion that is due to a more sinister and rare cause. Encephalitis is a rare cause of confusion but it is important to recognise as early treatment is the key to preventing disability. While viral forms of encephalitis are well recognised, more recently the possibility of immune-mediated encephalitis due to circulating antibodies has begun to emerge as an important cause of encephalitis. Often these disorders occur in the presence of a remote malignancy, such as lung or ovarian cancer and often the neurological diagnosis is the first sign of the malignancy.

In the present issue of JNNP, Onugoren and colleagues have published a series of cases of encephalitis due to unusual antibodies http://jnnp.bmj.com/content/86/9/965.abstract . In their series, patients developed a form of encephalitis known as limbic encephalitis, due to GABA and AMPA receptor antibodies. Lung cancer was subsequently diagnosed in a number of their patients. Interestingly, immune treatments led to improvements in the neurological status of a number of these patients.

This is an interesting paper on a rare but emerging form of encephalitis. The diagnostic and treatment insights are particularly interesting for neurologists everywhere.