Opsoclonus myoclonus syndrome
Opsoclonus Myoclonus (OMS) is a neurological disorder which appears to be the result of an autoimmune attack on the nervous system. Symptoms include opsoclonus, myoclonus, ataxia, intention tremor, dysphasia, dysarthria, mutism, hypotonia, lethargy, irritability or malaise. About half of all OMS cases occur in association with neuroblastoma.
Synonyms
Opsoclonus Myoclonus Ataxia (OMA), Kinsbourne syndrome, Myoclonic Encephalopathy of Infants, Dancing Eyes-Dancing Feet Syndrome.
History
OMS was first described by Dr. Kinsbourne in 1962 (Kinsbourne M. Myoclonic enecphalopathy of infants. Journal of Neurology, Neurosurgery, Psychiatry 25:271-276, 1962.)
Prevalence
OMS is extremely rare, affecting as few as 1 in 10,000,000 people per year (can anyone confirm this?). It affects 1 to 3 percent of children with neuroblastoma.
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 and not contagious.
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.
What to do if you or your child is diagnosed
- Register at the OMS Support forum and ask for help.
- Be aware that sedation is difficult in OMS patients, most health professionals will not be aware to this. Have a look at these articles: What to avoid and [An Innovative Approach to the Problem of Sedating Children with Opsoclonus-Myoclonus Syndrome (Annals of Neurology. 1994;36(3):543-544)
- 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.
Signs and symptoms
Symptoms include opsoclonus, myoclonus, ataxia, intention tremor, dysphasia, dysarthria, mutism, hypotonia, lethargy, irritability or malaise.
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 malaise may begin weeks or months earlier.
Factors triggering a relapse
Infections have been reported to increase the risk for a relapse.
Prognosis
Currently there are no clinically established laboratory investigations available to predict prognosis or therapeutic response.
One study (Medical and Pediatric Oncology 36:612-622,2001) came to the conclusion that:
Patients with OMA and neuroblastoma have excellent survival but a high risk of neurologic sequelae. Favourable disease stage correlates with a higher risk for development of neurologic sequelae. The role of anti-neuronal antibodies in late sequelae of OMS needs further clarification.
Treatment
There is no known definitive cure for OMS. However, several drugs have proven to be effective in its treatment.
Some of medication used to treat the symptoms are:
- 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 slow tapering with pills generally follows.
- Immunoglobulins (antibodies) are often used with varying results.
- Several other immunosuppressive drugs, such as cyclophosphamide (Cytoxin), may be helpful in some cases.
- Chemotherapy for neuroblastoma may sometimes be effective.
- Rutuximab has been used.
- Other medications are used to treat symptoms without influencing the nature of the disease (symptomatic treatment):
- Tradazone can be useful against irritability and sleep problems
The following medications should probably be avoided:
- Midazolam - Can cause irritability
- 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.
External links
- Web sites about OMS