Opsoclonus-myoclonus syndrome – causes, symptoms, diagnosis, treatment, pathology


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.

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