OMS Manual/Chapter 2
CHAPTER 2 - MEDICAL TERMINOLOGY OF OMS: GLOSSARY OF TERMS
Description
[edit | edit source]When first encountering OMS, caregivers are rapidly introduced to medical terminology that can be overwhelming. This glossary covers the most important terms, updated to reflect current nomenclature as used in the 2022 International Consensus Statement and in PubMed-indexed literature through 2025.
Core Terminology (updated May 2026)
[edit | edit source]When first encountering OMS, caregivers are rapidly introduced to medical terminology that can be overwhelming. This glossary covers the most important terms, updated to reflect current nomenclature as used in the 2022 International Consensus Statement and in PubMed-indexed literature through 2025.
Opsoclonus: Rapid, involuntary, multidirectional, conjugate fast eye movements without intersaccadic intervals. Also called "saccadomania." These are chaotic eye movements in horizontal, vertical, and diagonal directions — distinctly different from nystagmus (which has a rhythmic, directional pattern). Opsoclonus is the hallmark diagnostic feature of OMS.
Myoclonus: Brief, involuntary, lightning-like twitching of a muscle or group of muscles. In OMS, myoclonus commonly involves the limbs and trunk.
Ataxia: Loss of muscular coordination resulting in unsteady gait, balance difficulties, or inability to walk. In OMS, ataxia frequently causes falls and regression of walking skills.
OMAS / OMS / OMA: Opsoclonus-Myoclonus-Ataxia Syndrome. All three abbreviations refer to the same condition; OMAS is preferred in current international clinical literature.
Paraneoplastic Syndrome: A neurological condition triggered not directly by a tumor, but by the body's immune response to a tumor. In pediatric OMS, the most common associated tumor is neuroblastoma.
Neuroblastoma: A cancer arising from immature nerve cells (neuroblasts). In children with OMS, neuroblastoma is typically found in the adrenal glands, abdomen, or chest. Importantly, in OMS-associated neuroblastoma, the tumor tends to be low-stage with favorable histology and excellent oncological outcomes.
Autoimmune: A process in which the immune system mistakenly attacks the body's own tissues. In OMS, the immune system appears to attack the brain and cerebellum rather than (or in addition to) the tumor.
Immunotherapy: Treatment designed to modulate (suppress or redirect) the immune system. First-line OMS immunotherapy includes corticosteroids, IVIG, and rituximab. See Chapter 8 for details.
IVIG (Intravenous Immunoglobulin): A pooled preparation of antibodies from thousands of healthy donors, given by intravenous infusion to modulate the immune response.
Rituximab (Rituxan): A monoclonal antibody that depletes B cells (CD20+). Rituximab is now incorporated into international treatment protocols for moderate-to-severe OMS and for refractory cases.
ACTH (Adrenocorticotropic Hormone): A hormone that stimulates the adrenal glands to produce cortisol; used as an immunomodulator in OMS, particularly in infants.
B Cells (B lymphocytes): Immune cells that produce antibodies. Elevated B-cell counts in cerebrospinal fluid (CSF) are a characteristic finding in OMS and may be used to guide treatment intensity.
T Cells (T lymphocytes): Immune cells involved in cell-mediated immunity. Both B- and T-cell abnormalities have been documented in OMS.
CSF (Cerebrospinal Fluid): The fluid surrounding the brain and spinal cord. Lumbar puncture (spinal tap) is performed to analyze CSF for elevated white blood cells, B cells, and other markers relevant to OMS.
Lumbar Puncture (Spinal Tap): A procedure in which a needle is inserted into the lower back to collect CSF for analysis. In OMS, CSF analysis may reveal lymphocytic pleocytosis (elevated white blood cells).
MIBG Scan (Meta-Iodobenzylguanidine): A specialized nuclear medicine scan used to detect neuroblastoma. Preferred over CT alone for neuroblastoma detection in OMS workup.
Mitchell-Pike Rating Scale: The standard OMS disease severity scoring tool used by specialists worldwide. Grades 6 domains (stance, gait, arm/hand function, opsoclonus, mood/behavior, speech) on a 0–3 ordinal scale (maximum 18). Download: OMSLife Foundation PDF
Relapse / Flare: Return or worsening of OMS symptoms after a period of improvement. Relapses may be triggered by illness, infection, immunization, or tapering of medications too quickly.
Remission: Absence or near-absence of active OMS symptoms. Remission does not mean the disease is cured; ongoing monitoring is required.
Neurocognitive Sequelae: Long-term neurological and cognitive effects. Studies consistently show that 70–80% of children with OMS experience long-term deficits in motor, cognitive, language, or behavioral function (Brunklaus A et al., Mitchell WG et al., Margolin E et al.).
Cerebellar Atrophy: Shrinkage of the cerebellum (the brain region controlling coordination), seen on follow-up MRI in approximately one-third of OMS patients, correlating with symptom severity (Rossi A et al., Almudhry M et al., Martinez Popple M et al., Anand G et al.).
Saccade: A rapid, conjugate eye movement. Opsoclonus consists of rapid, back-to-back saccades in all directions without pause.
Fasctigial Nucleus: A structure in the cerebellum that regulates saccadic eye movements. Dysfunction (disinhibition) of the fastigial nucleus is proposed as a key mechanism of opsoclonus.
Idiopathic OMS: OMS without an identified underlying cause (no tumor found, no confirmed infection). Approximately 50% of pediatric OMS cases are idiopathic or parainfectious.
Parainfectious OMS: OMS triggered by a preceding viral or bacterial infection (e.g., Mycoplasma pneumoniae, varicella zoster, Epstein-Barr virus, enterovirus). Desai SD et al., do Rosário MS et al., Rossor T et al.)
* Ganglioneuroblastoma:
http://www.healthline.com/health/ganglioneuroblastoma
* Central Nervous System (CNS):
http://biology.about.com/od/organsystems/ss/central-nervous-system.htm
Components and Processes of the Immune System
[edit | edit source]* Cytokines:
http://www.news-medical.net/health/What-are-Cytokines.aspx
* Chemokines:
http://www.news-medical.net/health/What-are-Chemokines.aspx
* Process of b/t cell proliferation Key role of CXCL13/CXCR5 axis for cerebrospinal fluid B cell recruitment in pediatric OMS
Pranzatelli MR, Tate ED, McGee NR, Travelstead AL, Ransohoff RM, Ness JM, Colliver JA
http://www.ncbi.nlm.nih.gov/m/pubmed/22264765/?i=24&from=Opsoclonus-myoclonus%20syndrome
* Elevated B-cell activating factor BAFF, but not APRIL, correlates with CSF cerebellar autoantibodies in pediatric opsoclonus-myoclonus syndrome
http://www.ncbi.nlm.nih.gov/pubmed?db=pubmed&cmd=search&term=19339060
Scans and Imaging
[edit | edit source]* Magnetic Resonance Imaging (MRI):
http://www.medicalnewstoday.com/articles/146309.php
* X-ray computed tomography (CT Scan):
http://www.medicalnewstoday.com/articles/153201.php
Other Key Medical Terms
[edit | edit source]* Blood Brain Barrier:
http://www.brainfacts.org/brain-basics/neuroanatomy/articles/2014/blood-brain-barrier
* Biomarkers (generic medical definition):
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3078627/
Labs
[edit | edit source]* Catecholamine:
http://www.medicinenet.com/script/main/art.asp?articlekey=20210
* Complete Blood Count (CBC):
http://www.medicinenet.com/complete_blood_count/article.htm
* Flow cytometric analysis of cerebrospinal fluid
http://www.news-medical.net/life-sciences/What-is-Flow-Cytometry.aspx
* Absolute Neutrophil Count (ANC):
http://www.medicinenet.com/script/main/art.asp?articlekey=20030
* Comprehensive Metabolic Panel (CMP):
https://medlineplus.gov/ency/article/003468.htm
* Liver Function Tests (LFT):
http://www.medicinenet.com/liver_blood_tests/article.htm
* Quantitative Immunoglobulins Test:
http://labtestsonline.org/understanding/analytes/immunoglobulins/tab/test
* Fantastic website which offers easy to understand information about labs and interpreting results:
http://Www.labtestsonline.org