What’s evolving at the cutting-edge of autoimmune neurology?

This is a follow up to my previous blog titled What are the dreadful autoimmune disorders that plague neurology. Autoimmune neurology is a rapidly evolving field; blink and you will miss important developments. So what’s evolving in autoimmune neurology? Below are my top 4.

 

1. Insignificance of isolated VGKC positivity

By The original uploader was Iantresman at English Wikipedia - Transferred from en.wikipedia to Commons., CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1821346
By The original uploader was Iantresman at English Wikipedia – Transferred from en.wikipedia to Commons., CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1821346

Anti VGKC antibody encephalitis is caused by two different antibodies called LGI1 and Caspr2. The immunology laboratory would however only test for these two if the ‘generic’ VGKC test is positive. Neurologists are understandably left scratching their heads when both tests turn out to be negative. Not any more, going by a report in Neurology titled The relevance of VGKC positivity in the absence of LGI1 and Caspr2 antibodies. The judgment is out: a positive VGCK antibody test is not significant if both LGI1 and Caspr2 are negative. What a relief.

2. IgG4-mediated autoimmune disorders

By Swharden - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4752456
By SwhardenOwn work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4752456

This is a fairly new group of autoimmune disorders consisting of at least 13 different types. They are bad news because they cause many neurological disorders and also ravage other organs. I have previously discussed IgG4 peripheral neuropathy in my post titled What’s looming at the frontline of peripheral neuropathy. The other neurological diseases associated with IgG4 include, surprisingly, myasthenia gravis (MG), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and neuromyotonia. Less familiar IgG4 disorders are encephalopathyhypertrophic pachymeningitis and  sleep disorders with antibody to Iglon5. Trust the researchers to keep the clinicians ever on their toes.

3. GRIN-1 NMDA receptor encephalitis

DNA strand. Mehmet Pinarci on Flikr. https://www.flickr.com/photos/99843102@N05/14002600832
DNA strand. Mehmet Pinarci on Flikr. https://www.flickr.com/photos/99843102@N05/14002600832

Many acquired neurological disorders have a way of dragging genetics into their fold. Such is the case it seems with anti NMDA receptor encephalitis. This is the case with the GRIN-1 gene which codes for an NMDA receptor subunit. Mutations in this gene results in visual impairmentintellectual disability, and eye movement disorders. This is reported in Neurology by Josep Dalmau and colleagues in a paper titled Delineating the GRIN1 phenotypic spectrum. It is appropriate that the authors call this the genetic sibling of NMDA receptor encephalitis.

4. ECT for anti-NMDA receptor encephalitis 

Medcraft B-24 MarkII ECT. Niall Williams on Flikr. https://www.flickr.com/photos/niftyniall/17654690751
Medcraft B-24 MarkII ECT. Niall Williams on Flikr. https://www.flickr.com/photos/niftyniall/17654690751

The typical treatment of autoimmune encephalitis revolves around steroids, intravenous immunoglobulins (IVIg), and plasma exchange. Neurologists, when pushed to the wall, may use heavy duty agents such as Rituximab and Cyclophosphamide. Because anti-NMDA receptor encephalitis may be associated with ovarian teratomas, neurologists may make the difficult trip across the border to consult their gynaecology colleagues. I thought these were all the treatment options for anti NMDA receptor encephalitis until I read this case report, again in Neurology, which reported an excellent response to Electroconvulsive therapy in anti-NMDA receptor encephalitis. A no-brainer then if you see neurologists exchanging pleasantries with psychiatrists: they are the ECT experts. It is just a case report for now, but well-worth thinking about when all else fails.

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You may check out The Anti NMDA Receptor Encephalitis Foundation which is raising awareness of autoimmune encephalitis.

And here is a recent practical and comprehensive review of anti NMDA encephalitis by Eric Lancaster in the Journal of Clinical Neurology

And indulge me to make another shameless pitch here for neurochecklists which, after all, covers   autoimmune neurology comprehensively!

Metronidazole-two case lessons for neurologists

I came across two articles recently which highlighted neurological complications of metronidazole I was previously unaware of.

321-Metronidazole by Chris on Flikr. https://www.flickr.com/photos/chrisinplymouth/3947569729
321-Metronidazole by Chris on Flikr. https://www.flickr.com/photos/chrisinplymouth/3947569729

 

The first is a case report of metronidazole-induced encephalopathy in the journal Neurocritical Care. I admit I only read the abstract and the key word there is involvement of the dentate nuclei.

 

Metronidazole by Chris on Flikr. https://www.flickr.com/photos/chrisinplymouth/3949517597/
Metronidazole by Chris on Flikr. https://www.flickr.com/photos/chrisinplymouth/3949517597/

 

The second case report is of metronidazole-induced ataxia in the journal Movement Disorders.

 

These are rather uncommon side-effects and should not deter from prescribing metronidazole. But it is just worth looking more carefully at that medication list if your next patient  has unexplained encephalopathy or ataxia.