“Running to stand still…”

When I started working as a Clinical Microbiologist in 2007, anti-NMDA receptor encephalitis had not yet been discovered. The diagnostic test, looking for anti-NMDA receptor antibodies, only appeared commercially around 2010.

Now it is the latest fashionable test to perform…

I am getting old.

The whole area of auto-immune encephalitis has progressed rapidly in the last 10 years, and this potentially treatable cause of encephalitis (options include steroids, IV immunoglobulins, plasma exchange and immunomodulators) is now thought to be similar in prevalence to some viral encephalitides.

Anti-NMDA receptor encephalitis represents the vast majority (approx. 80%) of all cases of autoimmune encephalitis. It usually presents with a short prodromal period followed by a range of symptoms such as auditory and visual hallucinations, delusions, behavioural change, decreased level of consciousness, seizures, and autonomic dysfunction. 

A majority of patients (58%) with anti-NMDA receptor encephalitis will have a CSF leucocytosis(Raised CSF protein and oligoclonal bands are also seen in a proportion of patients.) So testing for anti-NMDA receptor antibodies becomes the obvious default for a patient with a CSF leucocytosis and negative bacterial culture and negative CSF viral PCR…

Other causes of autoimmune encephalitis include unfamiliar names such as anti-LGl1, anti-AMPAR, anti GABA  and anti-CASPR to name but a few. You will likely see these crop up from time to time on CSF request forms.

It is of course not microbiology per se. However we need to know about it as we end up getting the CSF samples and we need to triage the test requests, and deal with the perennial problem of separating a ml or two of CSF for several different tests, which often get sent away to different laboratories…

I didn’t need to worry about these exotic tests 10 years ago. Now I do.

Sometimes it feels like you need to keep running just to stand still…


p.s.  For the academics amongst you, NMDA stands for N-methyl-D-aspartate.

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