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|NI FEATURE: THE EDITORIAL DEBATE II-- PROS AND CONS
|Year : 2018 | Volume
| Issue : 5 | Page : 1293-1294
Opsoclonus myoclonus ataxia syndrome
Satish Khadilkar1, Rajesh Benny2
1 Department of Neurology, Bombay Hospital Institute of Medical Sciences, Mulund, Mumbai, Maharashtra, India
2 Department of Neurology, Fortis Hospitals, Mulund, Mumbai, Maharashtra, India
|Date of Web Publication||17-Sep-2018|
Dr. Satish Khadilkar
110, New Wing, First Floor, Bombay Hospital, 12 New Marine Lines, Mumbai - 400 020, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Khadilkar S, Benny R. Opsoclonus myoclonus ataxia syndrome. Neurol India 2018;66:1293-4
The problem with rare diseases is obvious; no one sees several, and hence, getting a total perspective of the illness is difficult. Literature on such conditions accumulates bit by bit, depicting observations on behaviour of the illness and the therapy employed in that given patient; generalizations of which are challenging. In this context, the manuscript in this issue of Neurology India, titled “Pediatric opsoclonus myoclonus ataxia syndrome: Experience of a tertiary care university hospital" is important as it gives information on a cohort of patients with this uncommon illness. Naturally, the cohort is small, but patients have been followed up over time, which gives valuable information. While such information is available in some populations, only a few case reports and a single case series have been written up from India, hence this manuscript is particularly relevant.
As we know, the constellation of opsoclonus, myoclonus and ataxia (the opsoclonus, myoclonus and ataxia syndrome, OMAS), also known as the Kinsbourne syndrome, is a rare auto-immune disease. It is more common in children. Importantly, it may herald the presence of an occult neuroblastoma in 40- 50% of cases; and in the remaining patients, the disease occurs due to post-infectious causes. Girls tend to have more of tumoral OMAS. The clinical presentation of those patients with or without a tumour is identical. Uncommonly, opsoclonus may be a late clinical feature, in which case, diagnosis of this syndrome may be delayed.
Non-tumoral cases tend to be triggered by a variety of systemic infections. As you will note from the case reports available in the Indian literature, a variety of antecedent infections like scrub typhus, dengue, or malaria, have been reported in our patients, which is of interest. The present investigation by Huddar and colleagues does not give information on this aspect and authors mention the limitation that patients reached their centre after the acute phase was over.
The authors present a useful algorithm in their exposition of the topic, outlining workflow for such cases. It is important to recognise that the para-infectious and neoplastic columns merge at level two, emphasizing the fact that ruling out a neoplasm is rewarding for patients with OMAS; these could be outwardly para-infectious. Thus, it is important to screen children presenting as OMAS for an occult neuroblastoma. The symptoms may precede the diagnosis of the neuroblastoma in more than 50% of children with OMAS. Magnetic resonance imaging (MRI) of the pelvis, chest and abdomen, measurement of urinary vanillylmandelic acid and homovanillic acid should be performed in all children presenting with this condition. If the MRI is negative, it is important to perform a nuclear scan with 123- I- metaiodobenzylguanidine.
The present study utilized computed axial tomograms. The authors emphasize the fact that even when urinary vanillylmandelic acid and iodine-123 meta-iodobenzylguanidine were normal, the scan aided in the detection of the underlying tumour in their cohort of patients. While going through the detection rates of neuroblastoma in various series, one comes across a very wide range, from under 10% to two-thirds, suggesting the impact of the techniques used by various studies and underlining the need for a diligent search for the tumour. A neuroblastoma is an unusual tumour that can undergo spontaneous regression. Hence, in those patients without a tumour, it is difficult to know whether it was there in the first place or not. In those patients with non-tumoural OMAS, an MRI brain to look for structural lesions, and a cerebrospinal fluid examination to look for other infections that may have triggered the syndrome (hepatitis C, Epstein Barr virus, Coxsackie B3, mycoplasma pneumonia, human immunodeficiency virus etc.) are warranted. In the Indian setting, as pointed out earlier, search for the triggering infections probably needs to be wider to include specific infectious agents such as dengue, malaria, scrub typhus and the likes.
The main stay of treatment is immunotherapy, as removal of tumour alone does not improve the neurological symptoms. Most children respond to immunomodulation. In a large series of 74 patients, Tate and colleagues  compared various treatment modalities. Corticotropin therapy was documented to be superior to glucocorticoid therapy in their subjects. Also, a combination therapy (with either rituximab/cyclophosphamide or rituximab with chemotherapy) was found to be more beneficial than corticotropin alone. As expected, the risk of side-effects was higher in the combination group.
In the present investigation by Huddar et al., corticosteroids formed the mainstay of immunotherapy, and except for one child requiring intravenous immunoglobulins, all others responded to corticosteroid therapy and other medications were not required. This is interesting and encouraging as a proportion of non-responders have existed in the series of OMAS patients, and combination therapies have been resorted to. Huddar and colleagues also make a point that neuro- behavioural issues were more significant and long-lasting than speech and motor dysfunctions in their cohort. It, indeed, will be interesting to postulate as to whether these manifestations are to be considered as therapy failures in some way or are residual in nature, and whether their presence demands a more aggressive therapy paradigm. At this point in time, this postulation would be difficult to answer and longer follow-ups will be revealing. From the available literature, it presently appears that early and aggressive treatment of the syndrome does not guarantee a better outcome. This is more so for neurobehavioral abnormalities and not for motor symptoms, which improve in about 60% of the subjects, as shown in the present investigation.
Clearly, this manuscript by Huddar and colleagues is important as it provides us with some insights into the longitudinal monitoring and therapy of subjects of this uncommon syndrome of OMAS and touches upon areas where further work is required.
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Huddar A, Bindu PS, Nagappa M, Bharath RD, Sinha S, Mathuranath PS, Taly AB. Pediatric opsoclonus-myoclonus-ataxia syndrome: Experience from a tertiary care university hospital. Neurol India 2018;66:1332-7. [Full text]
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Tate ED, Pranzatelli MR, Verhulst SJ, Markwell SJ, Franz DN, Graf WD, et al
. Active comparator-controlled, rater-blinded study of corticotropin-based immunotherapies for opsoclonus-myoclonus syndrome. Child Neurol 2012;27:875-84.
Catsman-Berrevoets CE, Aarsen FK, van Hemsbergen ML, van Noesel MM, Hakvoort-Cammel FG, van den Heuvel-Eibrink MM. Improvement of neurological status and quality of life in children with opsoclonus myoclonus syndrome at long-term follow-up. Pediatr Blood Cancer 2009;53:1048-53.