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Zika virus and neurological disease: is there evidence for causality?

21 Apr, 16 | by Arun Krishnan, Web Editor

Arun Krishnan and Steve Vucic, Neurologists and JNNP web editors, discuss recent data on possible Zika virus-induced neurological disease.

There has been considerable worldwide coverage documenting the impact of the recent Zika virus epidemic which spread through South America and more recently the Carribean. While infection with Zika is of little consequence in most people but there have been major concerns with infection in pregnant women and most of the interest has focussed on the nervous system. The most marked congenital neurological abnormality has been the development of microcephaly in newborns and this was most clearly brought out in the large spike in cases of microcephaly in Brazil in 2016. There have however been concerns about attributing causality based on epidemiological data alone and a recent paper in the New England Journal of Medicine noted that there were methodological concerns in some of the studies and that it may be premature to invoke causality [1]. A more recent report in the same journal has laid out the case for and against a causal effect [2]. In this paper, the authors test current scientific knowledge concerning Zika against accepted criteria for proof of human teratogenicity. Interestingly, the case for causality appears strong when assessed in this manner. Of note, the spike in cases of microcephaly in South America was not the first time that it has been associated with a Zika outbreak: a previous Zika epidemic in French Polynesia in 2013-2014 was also associated with an increase in microcephaly. In both South America and French Polynesia, the Zika outbreak preceded the spike in microcephaly cases and neonates who were affected also manifested other signs that are consistent with Zika exposure. The authors also provide references to studies that have outlined the mechanisms of Zika-induced neurotoxicity, with changes noted in neural progenitor cells that are exposed to the virus, providing evidence of biological plausibility.

In addition to the neonatal neurological manifestations, Zika virus infections have been associated with the occurrence of Guillain Barre Syndrome (GBS) [3-7], an acute immune-mediatied polyradiculoneuropathy with a heterogeneous phenotype[8], that causes acute weakness and impaired sensation. The first case of ZIKA related GBS was reported in 2013 in a French Polynesian lady, clinically presenting as global tetraparesis, facial paralysis, and autonomic nervous system dysfunction[4].  Subsequently, a further 42 GBS cases secondary to Zika virus infection have been reported, with Zika virus infection preceding the onset of GBS by 6 days [5].  Most patients exhibited a rapid disease course, severe tetraparesis and bilateral facial weakness, with an elevated CSF protein level.  Respiratory dysfunction, requiring intensive care management, was evident in 38% of patients, although all responded to therapy with intravenous immunoglobulin or plasmapheresis.  Importantly, no patients died as a result of Zika virus infection related GBS, and over half the patients exhibited good clinical recovery  at 3 months post infection.  Neurophysiological studies disclosed a predominantly distal demyelinating motor neuropathy which improved on follow-up [5].   The pathophysiological mechanisms by which Zika virus infection underlies the development of GBS remains to be fully elucidated, although antigenic mimicry against yet to be identified axonal targets, or direct viral infection of nerves has been invoked.  Given the rapid reversal of clinical and neurophysiological findings, the possibility of an antibody-mediated blockade of nodal Na+ channels leading to failure of distal neurotransmission, should also be explored.

In conclusion, Zika virus infections can lead to severe neurological syndromes including neonatal microcephaly and GBS.  Since the Zika virus infection is spreading rapidly across the South America countries, physicians need to be vigilant about the possibility of neurological sequalae and resources need to be allocated to the management of neurological complications of Zika virus infection.


  1. Broutet N, Krauer F, Riesen M, Khalakdina A, Almiron M, Aldighieri S, et al. Zika Virus as a Cause of Neurologic Disorders. The New England journal of medicine. 2016. Epub 2016/03/10. doi: 10.1056/NEJMp1602708. PubMed PMID: 26959308.
  2. Rasmussen SA, Jamieson DJ, Honein MA, Petersen LR. Zika Virus and Birth Defects – Reviewing the Evidence for Causality. The New England journal of medicine. 2016. Epub 2016/04/14. doi: 10.1056/NEJMsr1604338. PubMed PMID: 27074377.
  3. Roze B, Najioullah F, Ferge JL, Apetse K, Brouste Y, Cesaire R, et al. Zika virus detection in urine from patients with Guillain-Barre syndrome on Martinique, January 2016. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin. 2016;21(9). Epub 2016/03/12. doi: 10.2807/ PubMed PMID: 26967758.
  4. Oehler E, Watrin L, Larre P, Leparc-Goffart I, Lastere S, Valour F, et al. Zika virus infection complicated by Guillain-Barre syndrome–case report, French Polynesia, December 2013. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin. 2014;19(9). Epub 2014/03/15. PubMed PMID: 24626205.
  5. Cao-Lormeau VM, Blake A, Mons S, Lastere S, Roche C, Vanhomwegen J, et al. Guillain-Barre Syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. Lancet. 2016. Epub 2016/03/08. doi: 10.1016/s0140-6736(16)00562-6. PubMed PMID: 26948433.
  6. Anaya JM, Ramirez-Santana C, Salgado-Castaneda I, Chang C, Ansari A, Gershwin ME. Zika virus and neurologic autoimmunity: the putative role of gangliosides. BMC medicine. 2016;14(1):49. Epub 2016/03/24. doi: 10.1186/s12916-016-0601-y. PubMed PMID: 27001187; PubMed Central PMCID: PMCPmc4802632.
  7. Araujo LM, Ferreira ML, Nascimento OJ. Guillain-Barre syndrome associated with the Zika virus outbreak in Brazil. Arq Neuropsiquiatr. 2016;74(3):253-5. Epub 2016/04/07. doi: 10.1590/0004-282×20160035. PubMed PMID: 27050856.
  8. Vucic S, Kiernan MC, Cornblath DR. Guillain-Barre syndrome: an update. J Clin Neurosci. 2009;16(6):733-41. Epub 2009/04/10. doi: S0967-5868(08)00527-4 [pii]10.1016/j.jocn.2008.08.033 [doi]. PubMed PMID: 19356935.

Antibody-mediated encephalitis: new insights into diagnosis and treatment

9 Sep, 15 | by Arun Krishnan, Web Editor

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 . 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.

Catatonia: what is it, why does it happen and how do you treat it?

29 Jul, 15 | by Arun Krishnan, Web Editor

Some readers will no doubt have watched the 1990 movie, Awakenings starring Robin Williams and Robert de Niro, about a group of patients who had suffered a form of encephalitis and survived, only to be permanently in a state of reduced awareness and responsiveness. The movie was based on a book by the famous neurologist, Oliver Sacks, and explores the potential use of a new treatment for these patients. In his memoir of the same name, Sacks was referring to the possible beneficial effects of L-DOPA, a medication that is first-line treatment for Parkinson’s Disease. That book was written 40 years ago, so what have we learnt since then about this condition?

In this issue of JNNP, Wijemanne and Jankovic have reviewed this topic and have provided an insightful update on this condition . As noted in their review, catatonia can occur in numerous conditions, both neurological and psychiatric, and it is no longer regarded purely as a form of schizophrenia. In addition, there are a number of systemic conditions in which it can occur including cardiovascular, renal and connective tissue disorders. It can also occur as an adverse reaction to numerous medications.

While the exact pathophysiology remains unclear, the role of changes in GABA neurotransmission have been explored in depth and Zolpidem, a GABA-agonist, has been suggested as a possible treatment. Electroconvulsive therapy (ECT) remains a very potent treatment for this condition and neuroleptic medications are also trialled in some patients. However, as noted in their review, the question of why this occurs remains unresolved and is a question for future research.

Scrub typhus: another treatable neurological infection

3 Jul, 15 | by Arun Krishnan, Web Editor

Infectious diseases of the nervous system are an evolving and extremely interesting area of neurology. There always seems to be a new infection on the horizon and this means that neurologists constantly need to stay up-to-date on how these infections present clinically. Importantly, many are treatable and this means that you have to be on the ball to ensure that patients can receive early treatment with a reduction in long-term disability.

In this issue of JNNP, Misra et al from Lucknow in India have presented a comprehensive analysis of patients admitted to their institution in 2012-2013 who had been diagnosed with Scrub Typhus, a condition transmitted by a rickettsial organism that is usually spread by ticks, lice and fleas There are certain areas of the world where this organism is endemic, including India, Pakistan, Russia, Japan and Australia.

Amazingly, the authors identified 38 cases in this short period of time and have provided a wonderful overview of how these patients present. Meningitis and encephalitis are common presentations with patients often experiencing headache, fever and disorientation. The condition can also be life-threatening and some patients in this series were admitted to intensive care units with lung involvement or kidney failure. The most important aspect of this paper is that ~90% had a good response to antibiotic treatment with doxycycline. As suggested by the authors, scrub typhus should be included in a list of conditions that can cause encephalopathy with fever, particularly in patients who live in or who have travelled to areas where this condition is endemic.

The obesity-stroke paradox: why do obese patients have milder strokes?

15 Jun, 15 | by Arun Krishnan, Web Editor

Over the weekend, the Sydney Morning Herald wrote of the ‘heavy cost’ of obesity to the Australian health system . The article featured a quote that “the new normal is to be overweight or obese”. The epidemic of obesity has presented major health challenges that are not just faced by the developed world but which are now increasingly also becoming part of the health dilemmas facing developing countries.

There are groups of obese patients however who do not seem to encounter the health problems that one might expect and these patients have been called the ‘obese well’ The reasons for why these people remain free of health problems remains unclear although a number of theories have been put forward including reduced inflammatory mediators in this group of patients. Accordingly, the possibility that anti-inflammatory drugs may improve outcomes such as glucose control and diabetes risk is an ongoing area of research.

In the current issue of JNNP, Kim and colleagues from Seoul have demonstrated that mild-moderate elevations of body mass index (BMI) are associated with reduced stroke severity . This backs up previous studies that have shown lower risk of mortality in obese patients who suffer haemorrhagic or ischaemic stroke. The importance of these observations is that it lays the foundation for further studies that may be able to address why this group is relatively protected from severe long-term disability. This will help in drilling down on the potential ways of improving outcomes in all stroke patients, regardless of BMI.

Amyotrophic lateral sclerosis: from Charcot to cutting edge molecular genetics

3 Jun, 15 | by Arun Krishnan, Web Editor

For most clinicians, having to tell a patient that they have motor neuron disease/amyotrophic lateral sclerosis (ALS) is a difficult and challenging dilemma. In the community, it is one of the few remaining conditions that are inseparably linked with severe physical disability resulting in loss of independence and eventually loss of life. On a more optimistic note, the pace of research in this field provides hope for a cure or at the least for treatments that may slow the progression of the condition.

ALS was first described by Jean-Martin Charcot, the father of modern Neurology and in the current issue of JNNP, Turner and Swash chart the historical journey that commenced with Charcot’s initial descriptions of the condition, which largely remain true and accurate to the present day. In addition, the authors have also managed to provide a state-of-the-art review of where we are at in terms of genetic contributions to this condition and provide a thorough analysis on the potential cause of ALS.

In addition to the obvious question of who is likely to develop ALS, they also touch on another intriguing question of whether there are individuals who are likely to never develop ALS.

In short, this is a highly recommended review.

Peptic ulcers, Nobel Prizes and Multiple Sclerosis

22 May, 15 | by Arun Krishnan, Web Editor

It has been a decade now since Barry Marshall and Robin Warren from the University of Western Australia (UWA) were awarded the Nobel Prize for Medicine for discovering the link between Helicobacter Pylori (H.pylori) and the development of peptic ulcers. Famously, their discovery involved Marshall ingesting the bacteria himself in order to prove his hypothesis. In keeping with very many Nobel Prize winners, the duo had to contend with fierce opposition from colleagues within the medical fraternity who simply refused to believe that there was any suggestion that ulcers could be due to infectious organisms.

A decade on, the multiple sclerosis (MS) research group from UWA have collaborated with Barry Marshall to investigate the possible connections between H.pylori and MS development. In a paper that appears in this month’s issue of JNNP, the authors have explored the ‘hygiene hypothesis’ in MS . This hypothesis contends that exposure to infections early in life are able to potentially reduce development of allergic and immune disease later in life through priming of the immune system. In their paper, the authors provide evidence that evidence of exposure to H.pylori is lower in MS patients than in controls. They also demonstrate that female MS patients who have evidence of previous exposure to H.pylori have lower rates of disability than those who do not. In terms of future research, the authors suggest that it would be important to work out why this relationship is only noted female patients and not in male patients.

Decision-making and multiple sclerosis: there is hope!

4 May, 15 | by Arun Krishnan, Web Editor

One of the most common concerns that I hear as a clinician from MS patients concerns their ability to organise and look after their lives. MS patients who have even the most mild degrees of physical disability report an alarmingly significant effect of the illness of their ability to multi-task and to just get things done in the course of a day. Due to the rapid rate of progress in developing new drugs for MS, we don’t see the levels of physical disability that we used to compared to patients who developed the condition in decades past. Yet, regardless of which medication an MS patient is taking, almost all report fatigue and some difficulty with decision making. The difficulty as a clinician is diagnosing this as there are no simple bedside tests to assess you go about making the sorts of daily decisions that one needs to as a functioning adult. Treatments? Don’t go there, there is simply nothing out there for this problem.

For any disease, you can’t really develop treatments that work without a very detailed knowledge of the mechanism that cause that disease. That’s my lead-in for telling MS patients that there is little I can offer them for any type of cognitive change that they may experience. Fortunately, Muhlert and colleagues have provided an interesting paper in the current issue of JNNP which provides the first evidence that changes in decision-making in MS patients are related to changes in specific parts of the brain’s grey and white matter. These are the studies that we need to make headway into a very prevalent issue for MS patients and their families.

Medication-overuse headache: finally, we have an intervention that works.

20 Apr, 15 | by Arun Krishnan, Web Editor

Headache. Common, painful, frustrating, exhausting- and that’s just what the neurologist feels when a headache patient walks in the room. The patients themselves are often at their wits end as headache, whatever the cause, is often functional incapacitating and can really ruin quality of life. Of all the headache types that are seen in neurology, medication-overuse headache (MOH) can be particularly challenging. The condition typically occurs in patients who take frequent large quantities of acute headache treatments, including over-the –counter drugs. The problem here is that these patients often are taking these tablets for another headache condition such as migraine. After taking large amounts of these acute treatments over long periods of time, their migraine symptoms often tend to morph with MOH symptoms and it can be very hard to tell the two apart. Getting patients to cut down on these meds is hard. How do keep patients on the straight and narrow, when as a neurologist, you only see them infrequently?

The answer: involve the GP! In this issue of JNNP, Kristoffersen and colleagues from Norway did just that . They undertook a randomised study in which they asked GPs to undergo further training in how to reduce consumption of drugs related to MOH. Patients were randomised to standard care or to the intervention. The study was successful in that allocation to the intervention improved outcomes in patients with MOH.

MOH is a very common problem and this paper sets out a simple intervention that could make a big difference to the care of these patients.

Temozolomide reduces risk of seizures in low grade glioma!

7 Apr, 15 | by Steve Vucic, Web Editor

Low grade gliomas are associated with a higher frequency of seizures.  While antieplipetic medications are utilized to reduced seizure frequency, in this issue of JNNP temozolomide was also associated with a a significant reduction in seizure frequency.  Perhaps temozolomide should be added to therapy of LGGs with intractable seizures.




Seizure reduction in a low-grade glioma: more than a beneficial side effect of temozolomide

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