Opsoclonus myoclonus syndrome

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: José Eduardo Riceto Loyola Junior, M.D.[2]

Synonyms and keywords:

Overview

Opsoclonus myoclonus syndrome (OMS) is a rare neurological disorder, which can be very heterogenous, presenting itself with many different symptoms such as opsoclonus and/or myoclonus - which name the syndrome, but also ataxia, behavioral and/or sleep disturbances. It is believed to be caused by an immune system dysfunction, either induced by infection or paraneoplastic etiologies.

Historical Perspective

• Opsoclonus myoclonus syndrome was first described in 1962 by M. Kinsbourne, who presented a series of six cases of children with ataxia, myoclonus and opsoclonus.
• The syndrome was named as "myoclonic encephalopathy", but has also been called as "dancing eye syndrome". Recently it has been more often referred to as opsoclonus myoclonus syndrome.

Classification

• There is no established system for the classification of opsoclonus myoclonus syndrome.

Pathophysiology

• The pathogenesis of opsoclonus myoclonus syndrome is characterized by neuroinflammation involving dysregulated B cells. It is believed that loss of tolerance and autoantibody production causes the neurological damage seen in the disease.
• Cerebrospinal fluid studies have shown B cell recruitment to the brain via CXCL13/CXCR5 and CXCL10/ CXCR3 ligand/receptor pairs. The B cell activating factor plays a role increasing B cell survivability and there may be seen intrathecal production of oligoclonal bands.
• There are two theories about the cause of the disease:
  • Dysfunction of the Purkinje cells in the cerebellar vermis leading to disinhibition of the oculomotor neurons of the fastigial nucleus of the cerebellum.
  • Disinhibition of burst neurons, which are mostly under inhibition from omnipause cells, causing saccadic eye movements.
• It is not known if the triggers that causes opsoclonus myoclonus syndrome and those that causes relapses of the disease are the same or if they affect the same region of the brain.
• There is no obvious gene/mutation associated with the development of opsoclonus myoclonus syndrome.
• On microscopic histopathological analysis, gliosis and inflammation in the cerebellar vermis are characteristic findings of opsoclonus myoclonus syndrome.

Clinical Features

• Opsoclonus myoclonus syndrome (also often called: “dancing eyes-dancing feet” syndrome) is a rare syndrome of unknown etiology that presents with the following features:
  • Opsoclonus,
  • Myoclonic jerks,
  • Behavioral disturbances
  • Ataxia.
• The cause is not yet known but the accepted hypothesis is that it is an autoimmune, inflammatory reaction which damages the central nervous system. It is theorized that I can be triggered by either a paraneoplastic (being associated with neuroblastoma in children) or an infectious etiology.
• In children it is associated neuroblastoma in approximately half of cases. In this age group it also presents with gait ataxia, dysarthria, drooling, irritability, vomiting, and insomnia.
• It has a relapse-remitting course. Symptoms may vary in duration during relapses and the remission period is also variable, but usually the relapses last at least 48-72h.
• Children affected by the disease may not be fully asymptomatic between the episodes of the disease, persisting with significant speech and language deficits, sleep and some behavioral changes.
• Most patients have no detectable antibody, but a few patients presenting with neuroblastoma do have anti-neuronal and anti-Purkinje cell antibodies.
• Children with neuroblastoma and opsoclonus myoclonus syndrome usually have a better prognosis for their neuroblastomas as they are in more differentiated stages.

Differentiating Opsoclonus Myoclonus syndrome from other Diseases

• Opsoclonus myoclonus syndrome must be differentiated from acute inflammatory cerebellar ataxia, which can be differentiated by the type of eye movement, rapid recovery without treatment and absence of irritability.

Epidemiology and Demographics

• The prevalence of opsoclonus myoclonus syndrome is approximately 1 per 1,000,000 individuals worldwide.

Age

• Opsoclonus myoclonus syndrome is more commonly observed among patients aged 18 months old and may occur up to 5-6 years old.
• Relapses of the disease may affect adults.

Gender

• Girls are slightly more affected with opsoclonus myoclonus syndrome than boys.

Race

• There is no racial predilection for opsoclonus myoclonus syndrome.

Risk Factors

• There are no risk factors associated with the development of opsoclonus myoclonus syndrome.

Natural History, Complications and Prognosis

• The majority of patients with [disease name] remain asymptomatic for [duration/years].
• Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
• If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
• Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
• Prognosis is generally poor, as the patients with opsoclonus myoclonus syndrome usually remain with developmental delays and severe learning difficulties.
• Adult opsoclonus myoclonus syndrome can occur as a paraneoplastic syndrome in association with small cell lung cancer or breast cancer, half of the cases being idiopathic and parainfectious.

Diagnosis

Diagnostic Criteria

• The diagnosis of opsoclonus myoclonus syndrome is made when at least 3 of the following 4 diagnostic criteria are met:
  • Rare type of cancer that affects the nerve (neuroblastoma)
  • Uncontrolled eye movement (opsoclonus)
  • A movement disorder with sudden muscle contractions (myoclonus) and/or lack of coordination (ataxia)
  • Behavioral and/or sleep disturbance

Symptoms

The component features of OMS include repeated, random and rapid eye movements in both horizontal, vertical and diagonal directions (opsoclonus); unsteady gait or loss of ability to stand and walk (ataxia); brief, repeated, shock-like spasms of several muscles within the arms, legs (myoclonus), or tremor interfering with hand use. Behavioral and sleep disturbances, including extreme irritability, inconsolable crying, reduced and fragmented sleep (insomnia) and rage attacks are common. Difficulty articulating speech (dysarthria), sometimes with complete loss of speech and language may occur. Additional symptoms such as decreased muscle tone (hypotonia) and vomiting are common.

• [Disease name] is usually asymptomatic.
• Symptoms of [disease name] may include the following:

• [symptom 1]
• [symptom 2]
• [symptom 3]
• [symptom 4]
• [symptom 5]
• [symptom 6]

Physical Examination

• Patients with [disease name] usually appear [general appearance].
• Physical examination may be remarkable for:

• [finding 1]
• [finding 2]
• [finding 3]
• [finding 4]
• [finding 5]
• [finding 6]

Laboratory Findings

• There are no specific laboratory markers associated with opsoclonus myoclonus syndrome.
• In adults with OMS, a blood exam may show Hu anti-neuronal nuclear antibodies (anti-Hu) but not in children.

• A [positive/negative] [test name] is diagnostic of [disease name].
• An [elevated/reduced] concentration of [serum/blood/urinary/CSF/other] [lab test] is diagnostic of [disease name].
• Other laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].

Imaging Findings

• There are no [imaging study] findings associated with [disease name].

• [Imaging study 1] is the imaging modality of choice for [disease name].
• On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
• [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].

Other Diagnostic Studies

• [Disease name] may also be diagnosed using [diagnostic study name].
• Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].

Treatment

Medical Therapy

• There is no treatment for [disease name]; the mainstay of therapy is supportive care.

• The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
• [Medical therapy 1] acts by [mechanism of action 1].
• Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].

Surgery

• Surgery is the mainstay of therapy for [disease name].
• [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
• [Surgical procedure] can only be performed for patients with [disease stage] [disease name].

Prevention

• There are no primary preventive measures available for [disease name].

• Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].

• Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].

References

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