Opsoclonus Myoclonus syndrome

Opsoclonus myoclonus syndrome (OMS) is a rare neurological disorder of unknown causes which appears to be the result of an autoimmune attack on the nervous system. It is an extremely rare condition, affecting as few as 1 in 10,000,000 people per year. It affects 1 to 3 percent of children with neuroblastoma.

OMS was first described by Dr. M. Kinsbourne in 1962. Other names for OMS include:

• Opsoclonus Myoclonus Ataxia (OMA)
• Kinsbourne syndrome
• Myoclonic Encephalopathy of infants
• Dancing Eyes-Dancing Feet syndrome
• Dancing Eyes syndrome

Signs and symptoms

Symptoms include:

• myoclonus
• ataxia
• intention tremor
• dysphasia
• dysarthria
• mutism
• hypotonia
• lethargy
• irritability or malaise.

About half of all OMS cases occur in association with neuroblastoma.

Diagnosis

Because OMS is so rare and occurs at an average age of 19 months, a diagnosis can be slow. Some cases have been misdiagnosed as having been caused by a virus or conditions such as cerebellar ataxia.

Cause

The ultimate cause of OMS is unknown. About half of all cases are associated with neuroblastoma and most of the others are suspected to be associated with an undetected neuroblastoma. It is hypothesised that a viral infection causes the remaining cases, and probably most or all of the adult cases. Certainly OMS is not an infectious disease.

What to do if you or your child is diagnosed

• Register at the and ask for help.
• Be aware that sedation is difficult in OMS patients, most health professionals will not be aware of this. Have a look at these articles: and [
• Find a specialist (typically a neurologist) who has treated OMS before to look after you. Even though OMS is so rare, most major population centers should have one or two people who have a 'special interest' in OMS.

Disease course and clinical subtypes

In most cases OMS starts with an acute flare-up of physical symptoms within days or weeks, but some less obvious symptoms such as irritability and ACTH has shown improvements in symptoms but can result in an incomplete recovery with residual decifits.

• corticosteroids (such as prednisone or methylprednisolone) used at high dosages (500 mg - 2 g per day intravenously for a course of 3 to 5 days) can accelerate regression of symptoms. Subsequent EXTREMELY slow tapering with pills generally follows.
• Immunoglobulins (antibodies) are often used with varying results.
• Several other immunosuppressive drugs, such as cyclophosphamide, may be helpful in some cases.
• Chemotherapy for neuroblastoma may sometimes be effective.
• Midazolam - Can cause irritability.
• Melatonin - Is known to stimulate the immune system.
• Also, see the links in the section above for more details

Additional treatment options include plasmapheresis ("washing the blood", showing similarities to dialysis) for severe, non-steroidresponsive relapses.

Contacts

The following table shows a list of medical practitioners who have had some experience with OMS:

Opsoclonus Myoclonus Syndrome Medical Practitioners

Name	Location	Experience	Comments
Dr. Jayne Antony	Westmead Children's Hospital, Sydney, Australia	Seen at least 4 OMS patients as of 2004	..
Dr. Padraic Grattan-Smith	Randwick Children's Hospital, Sydney, Australia	Seen at least 4 OMS patients as of 2004	..
Dr. Michael Pranzatelli	National Pediatric Myoclonus Center, Illinois, USA	Specializes in OMS
Dr. Wendy Mitchell	Children's Hospital, Los Angeles, USA	Extensive experience	..

A list of contacts outside the USA can be found at the page.

References

• Kinsbourne M. Myoclonic enecphalopathy of infants. Journal of Neurology, Neurosurgery, Psychiatry 25:271-276, 1962.
• Rudnick E, Khakoo Y, Antunes N, Seeger RC, Brodeur GM, Shimada H, Gerbing RB, Stram DO, Matthay KK. Opsoclonus-myoclonus-ataxia syndrome in neuroblastoma: Clinical outcome and anti-neuronal antibodies. A Children's Cancer Group Study. Med Pediatr Oncol, 2001; 36:612-622.