Opsoclonus Myoclonus (Kinsbourne syndrome, Myoclonic Encephalopathy of Infants, Dancing Eyes-Dancing Feet Syndrome)
What is Opsoclonus Myoclonus?
Also known as OMS, opsoclonus-myoclonus syndrome is a neurological disorder that affects speech and language, movement, balance, behaviour and vision. Many cases come on very suddenly and are severe. Other cases can be chronic (long-term). Opsoclonus is the name given for rapid side-to-side eye movements and myoclonus is a name given to sudden, jerky muscle movements.
Other names for OMS include:
- OMAS
- Kinsbourne syndrome
- opsoclonic encephalopathy
- dancing eyes-dancing feet
What are the symptoms of OMS?
Common symptoms of OMS include:
- opsoclonus (moving the eyes suddenly from side to side)
- myoclonus (sudden jerky movements in the muscle groups)
- being unsteady on your feet and a lack of balance
- difficulty forming words and sounds or complete mutism
- lack of muscle tone (dystonia)
- outbursts of anger
- disturbed sleep patterns
- severe irritability
What causes OMS?
Around 50 percent of cases that involve both opsoclonus and myoclonus are caused by a tumour, known as a neuroblastoma. This type of tumour is made up of underdeveloped nerve cells. In other cases, the cause is often viral. Infections that may cause OMS include St Louis encephalitis and Coxsackie virus B3. It may be possible that more cases are caused by a tumour. However, the tumour may have disappeared before investigations are undertaken.
Who is affected?
OMS is very rare and it affects 1 in every million people. It is most commonly found in young children between the ages of 18 months and 5 years old, but it can also affect adults. Both males and females are affected.
Diagnosing OMS
OMS is often misdiagnosed as cerebellar ataxia in children, as the symptoms are very similar and the muscular symptoms tend to become apparent prior to symptoms related to the eyes. Once a child has symptoms of opsoclonus, this makes making a diagnosis easier and symptoms alone are usually sufficient to give doctors a good idea of a diagnosis. Tests such as CT scans can be used to confirm a diagnosis and to identify a tumour. An MIBG scan may also be recommended. This test is designed to detect abnormal cell development within the body and it is commonly used to detect neuroblastoma. The spinal fluid may also be analysed to look for abnormal white blood cells.
Treatment for OMS
The main aim of treatment is to eradicate symptoms and options include immunotherapy and surgery in cases where there is a tumour present. In most cases, surgery is sufficient treatment for tumours and chemotherapy and radiotherapy are not required. However, immunotherapy will be required in addition to surgery.
A form of treatment known as FLAIR therapy is used to treat patients and benefits are seen in up to 90 percent of people. It is possible for therapy, particularly the use of ACTH, to cause side-effects and any risks will be outlined prior to the beginning of treatment. Without FLAIR therapy, the relapse rate is relatively high at around 50-60 percent of cases. With FLAIR therapy, the rate is much lower at around 20 percent. Results tend to be best in cases where treatment was administered early. In cases where improvements are marginal and the condition becomes chronic, it is common for children to have severe behavioural problems and mental health issues, including an elevated risk of depression.