What is so distinctive about anti-MUSK myasthenia gravis?

Myasthenia gravis (MG) is an iconic neurological disorder. It is classical in its presentation, weakness setting in with exertion and improving with rest. This fatigability is demonstrable in the laboratory when repetitive nerve stimulation (RNS) of the muscles results in a progressively decremental response. Clinically, myasthenia gravis is often a benign disorder which restricts itself to the muscles of the eyes: this ocular MG manifests just with droopy eyelids (ptosis) and double vision (diplopia). At the extreme however is generalised MG, a severe and life-threatening condition that justifies its grave appellation

By Posey & Spiller – Posey & Spiller: Fatigue (Ptosis) in a patient with MG (ed. 1904), Public Domain, Link

Myasthenia gravis depletes the energy reserve of muscles, something which is entirely dependent on acetylcholine (ACh), a chemical released at nerve endings. After release, ACh traverses the neuromuscular junction (NMJ) to attach itself to the acetylcholine receptor (AChR), which is comfortably nestled on the surface of the muscle. This binding of chemical to receptor is a significant event, setting sparks flying, and muscles contracting. In myasthenia gravis, this fundamental process is rudely disrupted by the onslaught of acetylcholine receptor antibodies. These aggressive AChR antibodies, produced by the thymus gland in the chest, vent their rage by competitively binding to the receptor, leaving acetylcholine high and dry. Eventually, the rampaging antibodies destroy the receptor in an act of unjustified savagery.

Drosophilia Neuron. NICHD on Flickr. https://www.flickr.com/photos/nichd/29596368551/

In tackling myasthenia gravis, it is no wonder that neurologists first have to hunt down the ferocious AChR antibodies. They whisk off an aliquot of serum to a specialist laboratory, but waste no time in planning a counteroffensive, confident that the test will return as positive. The strategy is to boost the level of acetylcholine in the NMJ, tilting the balance in favour of ACh against the antibodies. The tactic is to zealously despatch a prescription for a drug that will block acetylcholine esterase inhibitor, the enzyme which breaks down acetylcholine. The neurologist then closely observes the often dramatic response, one of the most gratifying in clinical medicine; one minute as weak as a kitten, the next minute as strong as an ox. MG is therefore one disorder which debunks the wicked jibe that neurologists know so much…but do so little to make their patients better!

Drosophilia Neuromuscular Junction. NICHD on Flickr. https://www.flickr.com/photos/nichd/34754479075

Unfortunately for the neurologist, every now and then, the AChR antibody test result comes back as negative. In the past, the dumbfounded and befuddled, but nevertheless undaunted neurologist, will march on, battling a diagnosis of antibody-negative MG. Nowadays however, this not a comfortable diagnosis to make because AChR antibody is no longer the only game in town. We now know that there are many other antibodies that are jostling for commanding positions in the anti-myasthenia coalition. These include anti LRP4, cotarctin, titin, agrin, netrin 1, VGKC, and ryanodine. However, the clear frontrunner in this melee is anti-MUSK antibody, responsible for 30-50% of MG in which there are no AChR antibodies.

By PyMol, CC0, Link

Anti MUSK syndrome has many distinguishing features that set it apart from the run-of-the-mill myasthenia gravis. Below are five distinctive markers of anti-MUSK syndrome:

  1. Subjects with anti-MUSK syndrome are typically middle-aged women in their 3rd or 4th decades. This is younger than the usual age of people with AChR MG. Indeed neurologists now recognise typical myasthenia as a disease of older people.
  2. People with anti-MUSK syndrome present with acute and prominent involvement of head and neck muscles. This results in marked swallowing and breathing difficulties. They are therefore at a higher risk of myasthenia crisis.
  3. Single fiber electromyogram (sfEMG), a specific and reliable neurophysiological test of MG, is often normal in anti-MUSK syndrome. This is partly because the limb muscles are usually spared in anti MUSK syndrome.
  4. People with anti-MUSK myasthenia often do not benefit from, nor do they tolerate, the  acetylcholinesterase inhibitors which are used to treat MG. Indeed, these drugs may worsen anti-MUSK syndrome.
  5. Thymectomy, removal of the thymus gland, is not beneficial in people with anti-MUSK syndrome, unlike its usefulness in AChR MG.
Thymus gland 2. RachelHermosillo on Flickr. https://www.flickr.com/photos/rachelhermosillo/5388860587

All this is just the tip of the evolving myasthenia gravis iceberg. You may explore more of myasthenia in our previous blog posts:

How is innovative neurology research energising myasthenia?

What is the startling research unsettling the treatment of myasthenia gravis?

What is the relationship of pregnancy to myasthenia gravis?

Is Zika virus infection a risk factor for myasthenia gravis?

What does the EMG show in LRP4 myasthenia gravis?

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

What are the most iconic neurological disorders?

***

You may also explore anti-MUSK, and all the other myasthenia gravis subtypes, in neurochecklists. Go on…you know you want to know more!

Antibody lights. Isabelle on Flickr. https://www.flickr.com/photos/diamondgeyser/456900567/

 

7 ominous signs that suggest you need to see a neurologist

Neurologists spend most of their time diagnosing benign conditions which are curable or treatable, or at least people learn to live with. Every now and then we see people with startling symptoms such as coma, convulsions, neck stiffness, or paralysis. These are obviously concerning to patients and their families who have a foreboding of diseases such as meningitis, epilepsy, and stroke. Serious as these disorders are, they at least announce themselves and show their hands. Many other neurological symptoms unfortunately give no hint of the serious diseases that follow in their trail. That is when things get a bit tricky.

Ominous. Ankakay on Flikr. https://www.flickr.com/photos/ankakay/4101391453
Ominous. Ankakay on Flikr. https://www.flickr.com/photos/ankakay/4101391453

What are these seemingly benign symptoms which jolt neurologists out of their blissful complacency? What are these red flag symptoms that pretend they are grey? Here are my 7 deceptively ominous neurological signs everyone should know about.

7. A numb chin

By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See "Book" section below)Bartleby.com: Gray's Anatomy, Plate 784, Public Domain, https://commons.wikimedia.org/w/index.php?curid=531758
By Henry Vandyke CarterHenry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 784, Public Domain, https://commons.wikimedia.org/w/index.php?curid=531758

This must be the most deceptive sinister symptom in neurology. Not many people will rush to their doctors to complain about a numb chin, but it is a symptom that makes neurologists very nervous. This is because the chin gets its sensory supply from the mandibular branch of the fifth cranial nerve, also called the trigeminal nerve because it has three branches. And neurologists know that, for some bizarre reason, cancers from other parts of the body occasionally send deposits to this nerve. The numb chin syndrome is therefore not to be treated lightly.

6. Muscle twitching

OK, don’t panic yet. We have all experienced this; a flickering of an overused and tired muscle; a twitching of the odd finger; the quivering of the calf muscles in older people. Neurologists call these fasciculations, and they are only a concern if they are persistent, progressive, and widespread. And also usually only if the affected muscles are weak. In such cases neurologists worry that fasciculations are the harbingers of sinister diseases, particularly motor neurone disease (MND), better known in America as amyotrophic lateral sclerosis (ALS) or Lou Gehrig disease. Many people with muscle twitching will however have nothing seriously wrong with them, and many will be shooed out of the consulting room with the label of benign fasciculations syndrome (we love our syndromes, especially when they are benign). There are many other causes of fasciculations, but MND is clearly the most sinister of them all.

5. Transient visual loss

Scott Maxwell on freestockphotos. http://www.freestockphotos.biz/stockphoto/9747
Scott Maxwell on freestockphotos. http://www.freestockphotos.biz/stockphoto/9747

Neurologists often ask people with headache if their vision blurs or disappears for brief periods of time. These visual obscurations are not as dramatic as the visual loss that accompanies minor strokes or transient ischaemic attacks (TIAs). Visual obscurations affect both eyes and last only a few seconds. They are the result of sudden but brief increases in an already elevated pressure in the head. This may occur with relatively benign conditions such as idiopathic intracranial hypertension (IIH), but it may also portend a serious disorder such as a brain tumour.

4. Sudden loss of bowel or bladder control

bubble-1013915_1920

Loss of control down there would surely concern many people, but often not with the urgency it deserves. There are many non-neurological causes of bowel or bladder incontinence, but a sudden onset suggests that it is arising from the nervous system. The worrying diagnoses here are spinal cord compression and spinal cord inflammation (transverse myelitis). These disorders are often associated with other symptoms such as leg stiffness and weakness, but I really wouldn’t wait until these set in before I ask to see a neurologist.

3. Saddle anaesthesia

bicycle-saddle-791704_1920

Whilst we are on the topic of things down there, a related sinister symptom is loss of sensation around the genitals and buttocks, something your doctor will prudently call saddle anaesthesia. This arises when the nerves coming off the lower end of the spinal cord, collectively called the cauda equina, are compressed. The unpalatable condition, cauda equina syndrome (CES), worries neurologists because the compression may be due to a tumour in the spinal canal.

PS: The bicycle saddle is an apt analogy, but if you prefer horse riding, below is an alternative image to soothe your hurt feelings.

 

By BLW - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1956552
By BLW – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1956552

2. A painful droopy eyelid

A droopy eyelid is a deceptively benign symptom which worries neurologists. This symptom, which neurologist prefer to call ptosis, is particularly concerning if it is accompanied by double vision. One worrying disorder which causes ptosis is myasthenia gravis (MG), and this presents with ptosis on both sides. More sinister is ptosis which is present only on one side, particularly if it is painful. This may be caused by brain aneurysms, especially those arising from a weakness of the posterior communicating artery (PCOM) artery. As the aneurysm grows, it presses on the third cranial or oculomotor nerve, one of three nerves that controls the eyeballs and keeps the eyelids open. An aneurysm is literally a time-bomb in the brain as they wield the threat of bursting and causing a catastrophic bleeding around the brain. This makes ptosis an ominous, but also a helpful, neurological symptom.

By Cumulus z niderlandzkiej Wikipedii, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3167579
By Cumulus z niderlandzkiej Wikipedii, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3167579

There are many other causes of ptosis including Horner’s syndrome, so don’t panic yet but get that eyelid checked out if it refuses to straighten out.

 

1. Thunderclap headache

By © Marie-Lan Nguyen / Wikimedia Commons, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=24189896
By © Marie-Lan Nguyen / Wikimedia Commons, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=24189896

thunderclap headache is a symptom that means exactly what it says on the label! Neurologists will ask if the onset felt as if one was hit by a cricket bat. Even though most people have never been so assaulted, almost everyone with thunderclap headache readily agree this is what it feels like. It is such a distressing symptom that it doesn’t strike the afflicted person (pun intended) that their doctors are more concerned about investigating them, then they are in curing their headache. They patient is rushed to the CT scanner, and then subjected to a lumbar puncture. The doctors then heave a huge sigh of relief when the spinal fluid shows no blood or blood products, reassured that the patient has not suffered a subarachnoid haemorrhage (SAH) from a ruptured a brain aneurysm. The patient, who now has just another headache, is left to get to grips with their now, suddenly, very uninteresting symptom. There are many other causes of a thunderclap headache, but a ruptured aneurysm is the most sinister. If you develop a thunderclap headache, don’t wait to see a neurologist…just get to the nearest hospital!

PS: Don’t feel aggrieved if you are across the Pacific; it is also a thunderclap headache if it felt like being hit by a baseball bat!

Baseball bat in sun. Peter Chen on Flikr https://www.flickr.com/photos/34858596@N02/3239696542
Baseball bat in sun. Peter Chen on Flikr https://www.flickr.com/photos/34858596@N02/3239696542

 

Want to check out more ominous signs? Check out Smart handles and red flags in neurological diagnosis by the neurologist Chris Hawkes in Hospital Medicine.

 

What is the startling research unsettling the treatment of myasthenia gravis?

The long-term treatment of myasthenia gravis (MG) relies on drugs which suppress the immune system. I listed some of these in my previous post titled How is innovative neurology research energising myasthenia? Steroids are the established first line immune suppressing treatment for MG but because of their many nasty side effects, they cannot be used at effective doses for long periods. This is why neurologists treating MG use so-called steroid-sparing agents to reduce, or eliminate, the need for steroids.

Little red pills. Jon nagl on Flikr. https://www.flickr.com/photos/jonnagl/2470078845
Little red pills. Jon nagl on Flikr. https://www.flickr.com/photos/jonnagl/2470078845

Azathioprine has the best evidence of effectiveness as a steroid-sparing drug, and it is the acknowledged favourite of neurologists. Azathioprine may however fail or cause unacceptable side effects. It is also unsuitable for people who lack TPMT, the enzyme that breaks it down. It is in these situations that things become slightly tricky for the neurologist.

By NLM - NLM Pillbox, http://pillbox.nlm.nih.gov/assets/large/000040lg.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14666931
By NLM – NLM Pillbox, http://pillbox.nlm.nih.gov/assets/large/000040lg.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14666931

In theory, neurologists are spoilt for choice when they can’t use Azathioprine. Methotrexate is my favourite option in such cases because it has an easy weekly dosing regime and it is fairly well-tolerated. Alas, a recent paper in Neurology titled A randomized controlled trial of methotrexate for patients with generalized myasthenia gravis has unsettled me by suggesting that methotrexate is not living up to its top billing. The authors of the paper studied 50 people with myasthenia gravis who were already taking steroids. They put some of them on methotrexate, and the others on placebo. The outcome was surprising; methotrexate did very little to reduce the requirement for steroids, and it did nothing to improve the symptoms of MG.

By Fdardel - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15465576
By Fdardel – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15465576

 

This is clearly disappointing. Whilst waiting for further studies to confirm or refute this finding, I wonder how reliable the other steroid-sparing MG drugs are. How good are mycophenolate, ciclosporin, cyclophosphamide, tacrolimus, and rituximab? What really works in MG? To the rescue comes the International consensus guidance for management of myasthenia gravis, just hot off the press! Alas, the experts who drafted this guidance only compounded my woes. They made many treatment recommendations, but these came with as many caveats. They said the evidence for mycophenolate and tacrolimus in MG is rather thin, and the evidence-based ciclosporine and cyclophosphamide have potentially serious side effects. And they couldn’t agree on how promising rituximab, the new kid on the block, really is.

By Oguenther at de.wikipedia - Own work mit Jmol auf Basis RCSB PDB 2OSL., Public Domain, https://commons.wikimedia.org/w/index.php?curid=15482243
By Oguenther at de.wikipedia – Own work mit Jmol auf Basis RCSB PDB 2OSL., Public Domain, https://commons.wikimedia.org/w/index.php?curid=15482243

We are therefore back to the question, what to do when Azathioprine fails? The experts tell us to stick to the usual suspects, but they urge caution. Perhaps what we need are newer and safer alternatives such as Lefluonamide, so new to the MG arena that it did not get a mention in the expert guidance.

 

 

What are the most iconic neurological disorders?

Neurology is a broad specialty covering a staggering variety of diseases. Some neurological disorders are vanishingly rare, but many are household names, or at least vaguely familiar to most people. These are the diseases which define neurology. Here, in alphabetical order, is my list of the top 60 iconic neurological diseases, with links to previous blog posts where available.

 

1. Alzheimer’s disease

By uncredited - Images from the History of Medicine (NLM) [1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=11648572
By uncredited – Images from the History of Medicine (NLM) [1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=11648572

2. Behcet’s disease

By Republic2011 - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=17715921
By Republic2011Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=17715921

3. Bell’s palsy

By http://wellcomeimages.org/indexplus/obf_images/69/f2/8d6c4130f4264b4b906960cf1f7e.jpgGallery: http://wellcomeimages.org/indexplus/image/M0011440.html, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=36350600
By http://wellcomeimages.org/indexplus/obf_images/69/f2/8d6c4130f4264b4b906960cf1f7e.jpgGallery: http://wellcomeimages.org/indexplus/image/M0011440.html, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=36350600

4. Brachial neuritis

5. Brain tumours

6. Carpal tunnel syndrome

7. Cerebral palsy (CP)

8. Cervical dystonia

9. Charcot Marie Tooth disease (CMT)

By http://wellcomeimages.org/indexplus/obf_images/66/09/4dfa424fe11bb8dc56b2058f04ba.jpgGallery: http://wellcomeimages.org/indexplus/image/V0026141.html, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=36578490
By http://wellcomeimages.org/indexplus/obf_images/66/09/4dfa424fe11bb8dc56b2058f04ba.jpgGallery: http://wellcomeimages.org/indexplus/image/V0026141.html, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=36578490

10. Chronic inflammatory demyelinating polyneuropathy (CIDP)

11. Cluster headache

12. Creutzfeldt-Jakob disease (CJD)

By Unknown - http://www.sammlungen.hu-berlin.de/dokumente/11727/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4008658
By Unknownhttp://www.sammlungen.hu-berlin.de/dokumente/11727/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4008658

13. Duchenne muscular dystrophy (DMD)

By G._Duchenne.jpg: unknown/anonymousderivative work: PawełMM (talk) - G._Duchenne.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=9701531
By G._Duchenne.jpg: unknown/anonymousderivative work: PawełMM (talk) – G._Duchenne.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=9701531

14. Encephalitis

15. Epilepsy

16. Essential tremor

17. Friedreich’s ataxia

By Unknown - http://www.uic.edu/depts/mcne/founders/page0035.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3960759
By Unknownhttp://www.uic.edu/depts/mcne/founders/page0035.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3960759

18. Frontotemporal dementia (FTD)

19. Guillain-Barre syndrome (GBS)

By Anonymous - Ouvrage : L'informateur des aliénistes et des neurologistes, Paris : Delarue, 1923, Public Domain, https://commons.wikimedia.org/w/index.php?curid=28242077
By Anonymous – Ouvrage : L’informateur des aliénistes et des neurologistes, Paris : Delarue, 1923, Public Domain, https://commons.wikimedia.org/w/index.php?curid=28242077

20. Hashimoto encephalopathy

21. Hemifacial spasm

22. Horner’s syndrome

By Unknown - http://ihm.nlm.nih.gov/images/B15207, Public Domain, https://commons.wikimedia.org/w/index.php?curid=19265414
By Unknownhttp://ihm.nlm.nih.gov/images/B15207, Public Domain, https://commons.wikimedia.org/w/index.php?curid=19265414

23. Huntington’s disease (HD)

https://en.wikipedia.org/wiki/George_Huntington#/media/File:George_Huntington.jpg
https://en.wikipedia.org/wiki/George_Huntington#/media/File:George_Huntington.jpg

24. Idiopathic intracranial hypertension (IIH)

25. Inclusion body myositis (IBM)

26. Kennedy disease

27. Korsakoff’s psychosis

28. Lambert-Eaton myasthenic syndrome (LEMS)

29. Leber’s optic neuropathy (LHON)

30. McArdles disease

31. Meningitis

32. Migraine

33. Miller-Fisher syndrome (MFS)

By J3D3 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=34315507
By J3D3Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=34315507

34. Motor neurone disease (MND)

35. Multiple sclerosis (MS)

36. Multiple system atrophy (MSA)

37. Myasthenia gravis (MG)

38. Myotonic dystrophy

39. Narcolepsy

40. Neurofibromatosis (NF)

41. Neuromyelitis optica (NMO)

42. Neurosarcoidosis

43. Neurosyphilis

44. Parkinson’s disease (PD)

45. Peripheral neuropathy (PN)

46. Peroneal neuropathy

47. Progressive supranuclear palsy (PSP)

48. Rabies

49. Restless legs syndrome (RLS)

50. Spinal muscular atrophy (SMA)

51. Stiff person syndrome (SPS)

52. Stroke

53. Subarachnoid haemorrhage (SAH)

54. Tension-type headache (TTH)

55. Tetanus

56. Transient global amnesia (TGA)

57. Trigeminal neuralgia

58. Tuberous sclerosis

59. Wernicke’s encephalopathy

By J.F. Lehmann, Muenchen - IHM, Public Domain, https://commons.wikimedia.org/w/index.php?curid=9679254
By J.F. Lehmann, Muenchen – IHM, Public Domain, https://commons.wikimedia.org/w/index.php?curid=9679254

60. Wilson’s disease

By Carl Vandyk (1851–1931) - [No authors listed] (July 1937). "S. A. Kinnier Wilson". Br J Ophthalmol 21 (7): 396–97. PMC: 1142821., Public Domain, https://commons.wikimedia.org/w/index.php?curid=11384670
By Carl Vandyk (1851–1931) – [No authors listed] (July 1937). “S. A. Kinnier Wilson“. Br J Ophthalmol 21 (7): 396–97. PMC: 1142821., Public Domain, https://commons.wikimedia.org/w/index.php?curid=11384670

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The Neurology Lounge has a way to go to address all these diseases, but they are all fully covered in neurochecklists. In a future post, I will look at the rare end of the neurological spectrum and list the 75 strangest and most exotic neurological disorders.

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!

What are the dreadful autoimmune disorders that plague neurology?

Neurologists have always known that autoimmunity accounts for many nervous system disorders. A classical example is Sydenham’s chorea or St Vitus dance. This movement disorder develops after rheumatic fever, and is caused by antibodies to the bacterium called Streptocccus. The modern-day resurrection of this condition is called paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections. I know, too long, but just call it PANDAS. A great acronym I must say, quite unlike ABGA which stands for anti basal ganglia antibody syndrome, an umbrella term for many movement disorders provoked by external agents.

Prague. Pedro Szekely on Flikr. https://www.flickr.com/photos/pedrosz/3806301921
Prague. Pedro Szekely on Flikr. https://www.flickr.com/photos/pedrosz/3806301921

Neurologists are also comfortable with the knowledge that primary autoimmune disorders affect the nervous system. Prominent here are the neuropsychiatric features of systemic lupus erythematosus (SLE). SLE also presents with movement disorders such as chorea, amongst many other features. Similarly, there are diverse neurological manifestations of the anti-phospholipid antibody syndrome.

By Gentaur - Gentaur, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7222221
By Gentaur – Gentaur, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7222221

A third group of neurological diseases are more sinister because the antibodies are generated by cancer cells. These paraneoplastic neurological syndromes are legion and protean, requiring a high index of suspicion to diagnose. Most frustrating for neurologists is that the cancer itself may not emerge for several years after the diagnosis of a paraneoplastic syndrome. Notorious for this cloak and dagger behaviour is small cell lung cancer (SCLC). Because of the potential consequences, neurologists deploy their heavy duty imaging scans such as positron emission tomography (PET) scans. They then lie low, year after year, waiting to nab the devious cancer as soon as it shows up.

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In recent years, a completely different class of disorders has attained notoriety and infamy in the form of autoimmune encephalitis. These disorders often pretend to be infectious diseases, but they totally disregard the antibiotics and antiviral agents the neurologist attacks them with. By subterfuge and subversion they disable ion channels and receptors to cause havoc in the brain. And nobody has described such havoc better than Susannah Cahalan in her book Brain on Fire: My Month of Madness.

 

Autoimmune encephalitis may fester for weeks, years or decades, evading detection by its duplicitous behaviour, and by the increasing number of antibodies that may be responsible. There are however three main culprit antibodies which neurologists are now getting a grip on:

  • Voltage gated potassium channel (VGKC)
  • N-methyl-d-aspartase (NMDA)
  • α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)

These conditions are all potentially fatal but eminently curable; this underlies the importance of recognising and treating them very early. A recent paper in Lancet Neurology summarises the clinical approach to autoimmune encephalitis (pdf).

 

B0007683 Ion channels. Wellcome Images on Flikr. https://www.flickr.com/photos/wellcomeimages/5814248573
B0007683 Ion channels. Wellcome Images on Flikr. https://www.flickr.com/photos/wellcomeimages/5814248573

 

Autoimmune neurology is a rapidly evolving field. I will review recent developments in this area in a second post to follow shortly titled What’s breaking at the cutting edge-of autoimmune neurology?

How is innovative neurology research energising myasthenia?

Myasthenia gravis (MG) is one of the best characterised neurological disorders. The hallmark of MG is fatigable weakness. This manifests as intermittent ptosis (droopy eyelids), diplopia (double vision), and limb weakness. There are two main types-ocular MG affects just the eyes and eyelids, and generalised MG affects the body, including the bulbar functions of  breathing and swallowing.

By Doctor Jana - http://docjana.com/#/nmj, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=46835961
By Doctor Jana – http://docjana.com/#/nmj, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=46835961

 

The problem in MG is straightforward lack of communication; the nerves and muscles aren’t talking to each other. The two meet up at the neuromuscular junction (NMJ) where the nerves send packages of acetylcholine to bind with acetylcholine receptors (AChR) on the surface of the muscles. The muscles usually acknowledge this by contracting and producing action, but in MG this response is blocked by antibodies to the acetylcholine receptor (AChR antibodies). Like all culprits, it has wily accomplices such as anti-muscle specific kinase (anti-MUSK) antibody.

By No machine-readable author provided. S. Jähnichen assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=423915
By No machine-readable author provided. S. Jähnichen assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (based on copyright claims)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=423915

 

AChR antibodies are produced by a gland in the chest called the thymus. Disturbingly, this rather shabby-looking tissue may become enlarged (thymic hyperplasia), or cancerous (thymoma). The neurologist is therefore quick to request a CT chest scan as soon as MG is confirmed. Alas, the thymus is often normal or even shrivelled, to the delight of the patient who escapes the cardiothoracic surgeon. The neurologist is however ambivalent because surgery often gives a one-off cure, and saves the neurologist from a life-long commitment to monitor toxic treatments. The life of a Neurologist!

With so much known about MG, one would think there is very little on the horizon to put a smile on the faces of people with MG. But this old dog still has a few new tricks, and here are 4 energising reports I came across.

1. Predicting generalisation of ocular MG

By BruceBlaus. When using this image in external sources it can be cited as:Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=29452230
By BruceBlaus. When using this image in external sources it can be cited as:Blausen.com staff. “Blausen gallery 2014“. Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=29452230

 

Neurologists are aware that ocular MG could transform to generalised MG, they just don’t know who is at risk. Generalised MG is obviously a worse condition and requires more heavy-duty treatments. After much speculation, a report in JAMA Neurology has found the predictor of MG generalisation. Titled Clinical Utility of Acetylcholine Receptor Antibody Testing in Ocular Myasthenia Gravis, the authors confirmed, for the first time ever, that the risk of generalisation is linked to higher AChR antibody levels. I know, you were expecting some new, cutting-edge test or technology: sorry for the dampener, but sometimes it’s the little things that count. 

2. Linking MG to muscular dystrophy

By Cbenner12 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19555962
By Cbenner12Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19555962

 

Congenital myasthenia is a slightly different kettle of fish from conventional MG. For one, the diversity of genetic mutations that cause congenital myasthenia is mind-boggling; there are >20 genetic forms of MG such as DOK 7, RAPSYN, LAMB 2, and AGRIN. And these all differ in their presentation and response to treatment. An addition to this long list of congenital myasthenic syndromes should therefore normally not be exciting news. But there is something different in the recent report in the journal Brain about GMPPB (you really don’t want to know what this stands for). The paper, titled Mutations in GMPPB cause congenital myasthenic syndrome, opens up a can of worms because GMPPB also plays a role in causing muscular dystrophy. The authors see this as a bridge between myasthenia and muscular dystrophy. All rather complicated stuff, not quite sure what the implications are, but that’s the reason neurologists exist!

3. Leflunomide for drug-resistant MG

By MarinaVladivostok - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=27488894
By MarinaVladivostokOwn work, CC0, https://commons.wikimedia.org/w/index.php?curid=27488894

 

Immunosuppression is the ultimate treatment for MG because it reduces the production of the MG-causing antibodies. And the neurologist has a list, an arm length, of immunosuppressive agents to try. This variety of options is helpful because earlier choices may be ineffective, intolerable, or impractical. Azathioprine, methotrexate, mycophenolate …these roll out easily from the neurologist’s pen. Leflunomide would however sound very strange in neurological circles; it is more familiar to rheumatologists who use it to treat rheumatoid arthritis. Neurologists, ever peeping into the rheumatology recipe book, thought why not try Leflunomide in MG. They reported their findings in Journal of Neurology as Leflunomide treatment in corticosteroid-dependent myasthenia gravis: an open-label pilot study. And the recipe worked; 9 of 15 people with severe, steroid-dependent, MG improved on Leflunomide. Great news for when the going gets tough.

3, 4 Diaminopyridine for anti-MUSK MG

Thankfully not all MG treatment involves immunosuppression. One approach is to prevent the break down of the enzyme (esterase) that breaks down acetylcholine-got it? In this way there will be more acetylcholine available to counter the effect of AChR antibodies. Medications that work in this way are called acetylcoline esterase inhibitors (ACEI). It’s OK to  re-read all this before proceeding!

Pyridostigmine is the quintessential ACEI. But this is not effective in the more severe anti-MUSK MG where typical MG treatments don’t work so well. Neurologists have tried all sorts, including Rituximab, to varying success. What to do when all fails? A paper in the journal Neurology offers some hope that anti-MUSK MG may respond to 3,4 Diaminopyridine. This will be heart-warming news to all neurologists, if they ignore the fact that it is a single case report! But hey, from little acorns grow giant oak trees.

Want to dig deeper into MG? Try this update on myasthenia gravis.