Paraneoplastic cerebellar syndrome (PCD) is a rare disorder caused by the secondary effects of cancer and is believed to be immune mediated. High titers in the patient's serum and cerebrospinal fluid (CSF) of autoantibodies directed against both neurons and tumor have been detected in some forms of this syndrome. These autoantibodies are considered the result of an immunologic response to tumor and may cross-react with cells of the nervous system, causing neuronal damage. Specific forms of this syndrome often are associated with specific antineuronal antibodies and tumors. The onset of neurologic symptoms and detection of these antibodies often precede diagnosis of the tumor; therefore, detection of these antibodies greatly assists the diagnosis of this syndrome and prompts investigations for the underlying tumor. Most paraneoplastic syndromes are rare, affecting less than 1% of persons with cancer.
Causes and symptoms
Most or all paraneoplastic syndromes are activated by the body's immune system. In response to a tumor, the immune system produces an antigen that is normally expressed exclusively in the nervous system. The tumor antigen is identical to the normal antigen, but for unknown reasons the immune system identifies it as foreign and mounts an immune response.
In general (although not always), PS develops in an acute or subacute fashion, over days or weeks. The nervous system disability is usually severe.
Due to the many manifestations of paraneoplastic syndromes, PS should be evaluated clinically by a coordinated team of doctors, including medical oncologists, surgeons, radiation oncologists, endocrinologists, hematologists, neurologists, and dermatologists.
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Because PS are considered to be immune-mediated disorders, two treatment approaches have been used: removal of the source of the antigen by treatment of the underlying tumor, and suppression of the immune response. Physicians often also prescribe a combination of either plasma exchange or intravenous immune globulin and immunosuppressive agents such as corticosteroids, cyclophosphamide, or tacrolimus. For most paraneoplastic syndromes, immunotherapy is not effective. Disorders involving the central nervous system, such as encephalomyelitis associated with cancer or paraneoplastic cerebellar degeneration, usually respond poorly to treatment, although they may stabilize when the underlying tumor is treated.
Disorders such as CD are usually associated with neuronal damage, and because they evolve subacutely and treatment is often delayed, neurons die, making recovery much more difficult.
It is important that caregivers for those with paraneo-plastic syndromes receive adequate support. The disorder typically emerges suddenly and without warning. The neurological manifestations of PS are complex and often require 24-hour patient care. Many caregivers will require quick access to information on caring for a disabled person. This includes information on social security benefits, insurance coverage, handicapped license plates, evaluations for physical therapy; handheld showerheads, and home healthcare and visiting nurses; and social workers and other support services.