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Paraneoplastic neurologic syndrome
Paraneoplastic neurological syndromes (PNS) can be defined as remote effects of cancer that are not caused by the tumor and its metastasis, or by infection, ischemia or metabolic disruptions.
ORPHA:36388Classification level: Group of disorders
- Paraneoplastic cerebellar degeneration
- Prevalence: Unknown
- Inheritance: Not applicable
- Age of onset: All ages
- ICD-10: -
- OMIM: -
- UMLS: C0393534 C0751911 C3267031
- MeSH: -
- GARD: 7326
- MedDRA: 10072106
PNS are rare, affecting less than 1/10,000 patients with cancer.
Only the Lambert-Eaton myasthenic syndrome is relatively frequent, occurring in about 1% of patients with small cell lung cancer. The other most common PNS are subacute cerebellar ataxia, limbic encephalitis (LE), opsoclonus-myoclonus (OM), retinopathies (cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR), Stiff-Person syndrome (SPS), chronic gastrointestinal pseudoobstruction (CGP), sensory neuronopathy (SSN), encephalomyelitis (EM) and dermatomyositis (see these terms). PNS can affect any part of the central or peripheral nervous system, the neuromuscular junction, and muscle. They can be isolated or occur in association. PNS are usually severely disabling.
They are caused by autoimmune processes triggered by the cancer and directed against antigens common to both the cancer and the nervous system (onconeural antigens).
In most patients, the neurological disorder develops before the cancer becomes clinically overt and the patient is referred to the neurologist for identification of the neurological disorder as paraneoplastic. Due to their high specificity, the best way to diagnose a neurological disorder as paraneoplastic is to identify one of the well-characterized anti-onconeural protein antibodies in the patient's serum. In addition, as these antibodies are associated with a restricted range of cancers, they can guide the search for the underlying tumor at a stage when it is frequently not clinically overt.
Management and treatment
This is a critical point as, to date, the best way to stabilize PNS is to treat the cancer as soon as possible. Unfortunately, about one-third of patients do not have detectable antibodies and 5% to 10% have an atypical antibody that is not well-characterized. As PNS are believed to be immune-mediated, suppression of the immune response represents another treatment approach.