Are parasites the simple solution to the problem of MS?

In medicine, microbes are notorious for causing disease. In neurology particularly, infection is the direct cause of serious diseases such as meningitis and encephalitis. Infections may also act as  catalysts for neurological disorders, for example when they trigger Guillain Barre syndrome (GBS). Infection is therefore a villain, a scoundrel to be apprehended and disarmed whenever it rears its head. But this picture may not hold true when it comes to multiple sclerosis (MS) where a contrary story is emerging, a narrative which holds infection as the hero, the daredevil that will save the day. The premise is simple: MS has very little presence in the regions of the world where infections reign supreme. Just look at any world prevalence map of MS to be convinced.

By MS_Risk_no_legend.svg: *MS_Risk.svg: Dekoderderivative work: Faigl.ladislav (talk)derivative work: Gabby8228 (talk) – MS_Risk_no_legend.svg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=15917004

How strong is this inverse relationship between infection and MS? It all boils down to the so-called hygeine hypothesis of autoimmune diseases. This suggests that the human immune system becomes dysregulated when it is not primed by infections, and this dysregulation results in autoimmune disorders. This point was strongly argued by Aakanksha Dixit and colleagues in their paper published in the International Journal of Molecular Science, titled Novel Therapeutics for Multiple Sclerosis Designed by Parasitic Worms. They contend that the relationship between parasitic infections and autoimmune diseases is “most compelling“, going on to assert that helminthic infections “may be the protective environmental factor against the development of MS”.

By Doc. RNDr. Josef Reischig, CSc. – Archiv autora, CC BY 3.0, Link

To support the hygiene theory of MS, that helminthic infections play a role in banishing MS, three levels of evidence are offered.

  1. The prevalence of MS steadily increases when the frequency of infections in a community is reduces.
  2. People with MS who also have helminthic infections have fewer relapses and slower disease progression.
  3. MS patients who are treated for their helminthic infections develop more relapses and have a more active disease course
Diversity and prevalence of gastrointestinal parasites in seven non-human primates of the Taï National Park, Côte d’Ivoire. Parasite, 2015, 22, 1.doi:10.1051/parasite/2015001, CC BY 4.0, Link

Toxoplasma gondii, the cause of toxoplasmosis, is perhaps the major parasite investigated in relation to MS. Asli Koskderelioglu and colleagues, for example, reported that exposure to T.gondii is less frequent in people with MS than in healthy control subjects. In their 2017 paper titled Is Toxoplasma gondii infection protective against multiple sclerosis risk?, published in Multiple Sclerosis and Related Disorders, they found that MS subjects who have higher toxoplasma antibody levels experience fewer relapses and less severe disease courses. This finding is corroborated by a 2015 paper in the Journal of Neuroimmunology titled Toxoplasma gondii seropositivity is negatively associated with multiple sclerosis.

CC BY 4.0, Link

Neurologists are however very cynical people, and they never believe what single trials tell them. After all, many microbes, such as Ebstein Barr virus (EBV), are touted as MS risk factors. For the sceptical neurologist, only systematic reviews and meta-analyses will do; these are the stuff of our dreams, the essence of our daily existence. So it is with a huge cheer that neurologists welcomed a 2018 systematic review and meta-analysis published in the Journal of Neuroimmunology and titled Is toxoplasma gondii playing a positive role in multiple sclerosis risk? The paper poured very cold water on the beautiful hygiene hypothesis. Whilst the authors, Reza Saberi and colleagues, confirmed that MS subjects had a lower risk of exposure to T. gondii, they found no relationship between this parasite and the development of MS. Wither a theory when it hits the reality of cold statistical analysis.

Cloudburst. Liz West on Flickr. https://www.flickr.com/photos/calliope/28825267500

Notwithstanding the systematic review, the helminth hypothesis marches on. It has even reached the stage of therapeutic trials where, as distasteful as it sounds, subjects ingest parasites by mouth! And the fancied parasite is not Toxoplasma gondii but Trichuris suis ova (TSO). It all began with a small observational trial in 10 people which proved that TSO is safe and well-tolerated (phew), but it had no value whatsoever in treating MS. Not discouraged, the hypothesis entered the slightly larger HINT 2 trial; this again confirmed good tolerability in 16 subjects, but any benefit in reversing MS was questionable. Undeterred, the hypothesis has gone for a bigger study in the form of the TRIOMS trial. This is a randomized, placebo-controlled study of 50 people with MS or clinically isolated syndrome (CIS) in which subjects will be ingesting 2,500 Trichuris suis eggs every two weeks. We wait with bated breaths for the results.

By Universidad de Córdoba – http://www.uco.es/dptos/zoologia/zoolobiolo_archivos/practicas/practica_4/practica4_botton.htm, Public Domain, Link

Before leaving this subject, we must know that helminths are not the only game in town; they have strong competition from their cousins, bacteria. And the standout character in this arena is Helicobacter pylori. We learnt this from a study published in 2015 in the Journal of Neurology Neurosurgery and Psychiatry. Titled Helicobacter pylori infection as a protective factor against multiple sclerosis risk in females, the paper reported that people with MS were less likely than controls to have been exposed to H. pylori. Two meta-analyses have also reviewed the relationship of H. pylori and MS, arguing strongly that, in Western countries, there is an inverse relationship between H pylori and MS. And they assert that H. pylori may be protective against MS. If it feels like déjà vu, it is.

Helicobacter pylori. AJC21 on Flickr. https://www.flickr.com/photos/ajc1/6946417103

We have surely not heard the last of bugs and MS. However, for now, the foundations of the hygiene theory are a bit shaky, and the future rather hazy.

By Doc. RNDr. Josef Reischig, CSc. – Archiv autora, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=17268274

 

What is the impact of Vitamin D on the complicated course of MS?

Some general neurologists get away with not having to think too much about multiple sclerosis (MS). This is because they have an ‘MSologist‘ at hand to refer all their patients with ‘demyelination‘. Many general neurologists however care for people with MS because they do not have a ‘fallback guy‘ to do the heavy lifting for them. This therefore makes it imperative for neurologists to keep up with everything about this often disabling and distressing disorder.

MS prevalence map. By AdertOwn work and [1], CC BY-SA 3.0, Link
The management of MS is however very tricky, and it is challenging to get a grip of it all. This is partly because the clinical course is varied, and the diagnostic process tortuous. The patient first goes through an onerous retinue of tests which include an MRI, a lumbar puncture, evoked potentials, and a shedload of blood tests. This is all in a bid to secure the diagnosis and to exclude all possible MS mimics.

MRI scan. NIH Image Galley on Flikr. https://www.flickr.com/photos/nihgov/30805879596

Then comes the head-scratching phase of determining if the patient actually fulfils the diagnostic criteria for MS, or if they just have clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS). To secure the diagnosis of MS, the neurologist turns to the McDonald criteria which stipulate dissemination in time and place of inflammatory events. As simple as this should be, this is no easy task at all. This is because, at different times, the criteria have meant different things to different people. The guidelines have also gone through several painful, and often confusing, iterations. Indeed the McDonald criteria have only recently been re-revised-to the delight of MSologists but the chagrin of the general neurologist!

Steampunk Time and Space Machine. Don Urban on Flikr. https://www.flickr.com/photos/donpezzano/3230179951

Once the diagnosis of relapsing remitting MS (RRMS) is reasonably established, the patient is taken through a guided tour of the ever-expanding available treatment options. These are typically to prevent relapses, but more recently to prevent disease progression as well. People with mild to moderate MS are nudged towards interferons, glatiramer acetate, dimethylfumarate, or terifluonamide. Those with more aggressive disease, on the other hand, are offered a menu of fingolimod, natalizumab, or alemtuzumab. Other newer agents include daclizumab and cladribine. And, just stepping into the arena, there is ocrelizumab for primary progressive (PPMS). Whichever option is chosen, the course of treatment is long, and it is fraught with risks such as infections and immune suppression.

https://pixabay.com/en/syringe-pill-bottle-morphine-small-1884784/

Once the bigger questions have been settled, the neurologist then braces for the ‘minor’ questions her enlightened patients will ask. The easier questions relate to the treatment of symptoms, and some of the most vexing concern the role of Vitamin D deficiency. Such questions include, ‘Is vitamin D deficiency a cause of MS?‘, ‘Do people who are vitamin D deficient experience a worse outcome?‘, and ‘Should patients with MS be on Vitamin D supplementation?‘.

Pandora’s box. Michael Hensman on Flikr. https://www.flickr.com/photos/mycael/3664900435

To attempt to resolve these questions I plunged into some of the literature on Vitamin D and MS. And this is like opening Pandora’s box. Here are some of the things I found.

***

Is MS associated with Vitamin D deficiency?

It therefore appears that there is an association of vitamin D deficiency with MS, but it is far from certain that this is a causative relationship. One hypothesis is that vitamin D deficiency is the outcome, rather than the cause, of MS. The deficiency presumably results becuase the very active immune system in people with MS mops up the body’s Vitamin D. This so-called reverse causation hypothesis asserts that vitamin D deficiency is a consumptive vitaminopathy

Sunshine Falls. Dawn Ellner on Flikr. https://www.flickr.com/photos/naturesdawn/4299041739

Does Vitamin D deficiency worsen MS progression?

There is therefore no single answer to this question, but the emerging consensus is that Vitamin D deficiency adversely affects the course of MS. 

Milk splash experiment. Endre majoros on Flikr. https://www.flickr.com/photos/boneball/24597145866

Should people with MS be on Vitamin D supplementation?

Even if Vitamin D deficiency doesn’t cause MS, the evidence suggests that it negatively influences the course of the disease.

Salmon salad nicoise. Keith McDuffee on Flikr. https://www.flickr.com/photos/gudlyf/3609052894

What to do?

This is the million dollar question eloquently posed by a recent editorial in the journal Neurology titled Preventing multiple sclerosis: to (takevitamin D or not to (takevitamin D? The reasonable consensus is to encourage vitamin D replenishment to prevent MS, starting from preconception. It is also generally agreed that people with MS should be on vitamin D supplementation in the expectation that it will slow the disease activity.

A practical approach to Vitamin D replacement is the Barts MS team vitamin D supplementation recommendation. This is to start with 5,000IU/day vitamin D, and aim for a plasma level of 100-250 nmol/L. Depending on the level, the dose is then adjusted, up or down, to between 2-10,000IU/day. They also advise against giving calcium supplementation unless there is associated osteoporosis.

What is a general neurologist to do? To follow the prevailing trend, and hope it doesn’t change direction too soon!

Vitamin D Pills. Essgee51 on Flikr. https://www.flickr.com/photos/sg51/5224823967

 

What are the most controversial questions in neurology?

Uncertainty and doubt abound in Neurology. There are many evidence-free areas where experts rub each other the wrong way. These controversies are big and occur in all neurology subspecialties. Controversy-busters have tried for about a decade to iron out these wrinkles on neurology’s face, but the unanswered questions remain. This is why there is a 10th World Congress of Controversies in Neurology (CONy) holding in Lisbon this year.

I want to assure you I have no conflict of interest to declare in this blog. My interest is to explore  which questions have plagued this conference over the last 10 years to pick out the most controversial topics in neurology. To do this I reviewed all previous conference programs and focused on the items that were slated for debate. I looked for practical topics that have remained unresolved, or are just emerging. Here are my top controversial neurological questions:

Raccoon argument II. Tambako The Jaguar on Flikr. https://www.flickr.com/photos/tambako/7460999402
Raccoon argument II. Tambako The Jaguar on Flikr. https://www.flickr.com/photos/tambako/7460999402

 

1st CONy 2007 (Berlin, Germany)

  • Clinically isolated syndromes (CIS): To treat or not to treat
  • Is stem cell therapy an imminent treatment in advanced multiple sclerosis (MS)?
  • Vascular cognitive impairment is a misleading concept?
  • Is mild cognitive impairment a misleading concept?

 

2nd CONy 2008 (Athens, Greece)

  • Can physical trauma precipitate multiple sclerosis?
  • Should patients with Parkinson’s disease (PD) be treated in the pre-motor phase?
  • What is the first line therapy for chronic inflammatory demyelinating polyneuropathy (CIDP)?
  • Is intravenous immunoglobulin (IVIg) effective in chronic myasthenia gravis (MG)?
  • Tau or ß-amyloid immunotherapy in Alzheimer’s disease (AD)?
  • Chronic fatigue syndrome is an organic disease and should be treated by neurologists?

 

3rd CONy 2009 (Prague, Czech Republic)

  • Should cerebrospinal fluid (CSF) be tested in every clinically isolated syndrome?
  • Can we prevent multiple sclerosis (MS) by early vitamin D supplementation and EBV vaccination?
  • Does Parkinson’s disease (PD) have a prion-like pathogenesis?
  • Patients with medication overuse headache should be treated only after analgesic withdrawal?

 

 

4th CONy 2010 (Barcelona, Spain)

  • Camptocormia in parkinson’s disease (PD): Is this dystonia or myopathy?
  • Does chronic venous insufficiency play a role in the pathogenesis of multiple sclerosis (MS)?
  • IVIg or immunosuppression for long-term treatment of CIDP?

 

5th CONy 2011 (Beijing, China)

  • Is sporadic Parkinson’s disease etiology predominantly environmental or genetic?
  • Is multiple sclerosis (MS) an inflammatory or a primarily neurodegenerative disease?
  • Are the new multiple sclerosis oral medications superior to conventional therapies?
  • Is bilateral transverse venous sinus stenosis a critical finding in idiopathic intracranial hypertension (IIH)?

 

6th CONy 2012 (Vienna, Austria)

  • Will there ever be a valid biomarker for Alzheimer’s disease (AD)?
  • Is amyloid imaging clinically useful in Alzheimer’s disease (AD)?
  • Do functional syndromes have a neurological substrate?
  • Should blood pressure be lowered immediately after stroke?
  • Migraine is primarily a vascular disorder?

 

 

7th CONy 2013 (Istanbul, Turkey)

  • Is intravenous thrombolysis the definitive treatment for acute large artery stroke?
  • Atrial fibrillation related stroke should be treated only with the new anticoagulants?
  • Is the best treatment for chronic migraine botulinum toxin?
  • IS CGRP the key molecule in migraine?
  • Is chronic cluster headache best treated with sphenopalatine ganglion (SPG) stimulation?
  • When should deep brain stimulation (DBS) be initiated for Parkinson’s disease?
  • Do interferons prevent secondary progressive multiple sclerosis (SPMS)?
  • Is deep brain stimulation (DBS) better than botulinum toxin in primary dystonia?
  • Are present outcome measures relevant for assessing efficacy of disease modifying therapies in multiple sclerosis (MS)?
  • Should radiologically isolated syndromes (RIS) be treated?
  • Does genetic testing have a role in epilepsy management?
  • Should cortical strokes be treated prophylactically against seizures?
  • Should enzyme-inducing antiepileptic drugs (AEDs) be avoided?
  • EEG is usually necessary when diagnosing epilepsy

 

8th CONy 2014 (Berlin, Germany)

  • Is late-onset depression prodromal neurodegeneration?
  • Does Parkinson’s disease begin in the peripheral nervous system?
  • What is the best treatment in advanced Parkinson’s disease?
  • Are most cryptogenic epilepsies immune mediated?
  • Should epilepsy be diagnosed after the first unprovoked seizure?
  • Do anti-epileptic drugs (AEDs) contribute to suicide risk?
  • Should the ketogenic diet be prescribed in adults with epilepsy?
  • Do patients with idiopathic generalized epilepsies require lifelong treatment?
  • Cryptogenic stroke: Immediate anticoagulation or long-term ECG recording?
Southern Chivalry: Argument Vs Clubs. elycefeliz on Flikr. https://www.flickr.com/photos/elycefeliz/6271932825
Southern Chivalry: Argument Vs Clubs. elycefeliz on Flikr. https://www.flickr.com/photos/elycefeliz/6271932825

 

9th CONy 2015 (Budapest, Hungary)

  • Is discontinuation of disease-modifying therapies safe in  long-term stable multiple sclerosis?
  • Is behavioral therapy necessary for the treatment of migraine?
  • Which is the first-line therapy in cases of IIH with bilateral papilledema?
  • Should patients with unruptured arterio-venous malformations (AVM) be referred for intervention?
  • Should survivors of hemorrhagic strokes be restarted on oral anticoagulants?
  • Will stem cell therapy become important in stroke rehabilitation?
  • Do statins cause cognitive impairment?

 

10th CONy 2016 (Lisbon, Portugal)

  • Which should be the first-line therapy for CIDP? Steroids vs. IVIg
  • Should disease-modifying treatment be changed if only imaging findings worsen in multiple sclerosis?
  • Should disease-modifying therapies be stopped when secondary progressive MS develops?
  • Should non-convulsive status epilepsy be treated aggressively?
  • Does traumatic chronic encephalopathy (CTE) exist?
  • Does corticobasal degeneration (CBD) exist as a clinico-pathological entity?
  • Is ß-amyloid still a relevant target in AD therapy?
  • Will electrical stimulation replace medications for the treatment of cluster headache?
  • Carotid dissection: Should anticoagulants be used?
  • Is the ABCD2 grading useful for clinical management of TIA patients?
  • Do COMT inhibitors have a future in treatment of Parkinson’s disease?

 

Debate Energetico. Jumanji Solar on Flikr. https://www.flickr.com/photos/jumanjisolar/5371921203
Debate Energetico. Jumanji Solar on Flikr. https://www.flickr.com/photos/jumanjisolar/5371921203

 

Going through this list, I feel reassured that the experts differ in their answers to these questions? The acknowledgement of uncertainty allows us novices to avoid searching for non-existent black and white answers. It is however also unsettling that I thought some of these questions had been settled long ago. It goes to show that apparently established assumptions are not unshakable?

Do you have the definitive answers to resolve these controversies? Are there important controversies that are missing here? Please leave a comment