Opsoclonus-myoclonus syndrome is also called OMS or dancing eyes-dancing feet syndrome.
Opsoclonus describes seemingly random, involuntary, and rapid eye movements in the horizontal,
vertical, and diagonal directions.
Myoclonus describes lightening-like limb movements or limb jerks, that can also be more tremulous.
The syndrome also causes ataxia, which often results in the inability to walk, sit or crawl,
and the loss of previously attained abilities, like speech.
Generally speaking, OMS is thought to be an autoimmune condition in which the body attacks
the nervous system, resulting in the characteristic signs and symptoms.
The precise cause of OMS is unknown, but in children, it’s often due to a paraneoplastic
syndrome.
The idea is that a hidden or occult tumor - like a neuroblastoma or ganglioneuroblastoma
- triggers the body’s immune system, and the resulting antibodies unintentionally target
healthy cells of the nervous system.
CD20+ B-cells that get into the CSF fluid seem to play an important role.
One brain area that gets affected is the cerebellum, which plays an important role in coordinating
body movements.
In older children and adolescents OMS is thought to be triggered by an infection, and in adults,
it’s often due to a paraneoplastic process due to lung or breast cancer, for example.
In children with OMS, there’s almost always ataxia, so it’s sometimes referred to as
OMAS - with the A representing ataxia.
In fact, most toddlers with OMS are initially misdiagnosed with acute cerebellar ataxia
of childhood.
The diagnosis of OMS is also often based on symptoms like opsoclonus and myoclonus which
can appear abruptly, progressing over days to weeks.
Other symptoms include the loss of developmental milestones like speech, developing extreme
irritability, and severe sleep disturbances.
Although there is no diagnostic test, a spinal tap can be done to look for evidence of antibodies
- called oligoclonal bands - in the cerebrospinal fluid or CSF.
And lymphocyte flow cytometry can be done to look for increased amounts of CD20+ B-cells
in the CSF.
Finally, a CT scan, MRI scan, PET scan, or a combination of these scans can be done to
help identify tumors that may have triggered OMS.
Finally, it’s important to ensure that the symptoms are not due to other processes, like
brain tumors or other lesions, which can also be identified on the imaging studies.
Immunosuppressive treatment options for OMS include corticosteroids, adrenocorticotropic
hormone, intravenous immunoglobulin or IVIG, cyclophosphamide, and rituximab, which is
a manufactured antibody that targets CD20+ B-cells, If a tumor is found, it is usually
removed by surgery, and rarely requires chemotherapy.
To help treat insomnia and rage attacks, certain medications can be used.
In mild cases, symptoms often improve or resolve completely, whereas in severe cases, there
may be residual symptoms for life and relapses are common.
All right, as a quick recap...Opsoclonus-myoclonus syndrome is a rare condition, with prominent
ataxia and behavioral changes, known for the unique eye movement, opsoclonus, which is
conjugate, involuntary, and rapid movements of the eyes in every direction, and quick,
“shock-like” movements of the arms and legs, called myoclonus.
The cause is thought to be either paraneoplastic or parainfectious in most cases.
The diagnosis typically involves imaging to aid with the diagnosis, while treatment includes
immunosuppressive therapy in addition to treatment for any tumor that’s identified.