Signs and symptoms from damage to any part of the nervous system remote from the site of malignancy or metastases.
Paraneoplastic neurological disorders increasingly recognized to have anti neural antibodies in the serum and the CSF.
These disorders reflect immune mediated and associated cancer induced immune responses, which include neuronal autoantibodies.
In a series of 60,000 consecutive patients suspected of having the PN syndrome 0.9 percent of patients had antibodies (Pittock SJ).
Due to tumors expressing antigens ectopically that have homologues expressed in the nervous system.
When the immune system encounters tumor cell antigens antibodies re generated and can be detected in the serum and CSF.
Such antibodies to tumor antigens can cross the blood-brain barrier and attack the central and peripheral nervous systems producing this syndrome.
Anti-neural antibodies are noted to be present with many cancer patients who do not have this syndrome.
Only 0.01% of patients with malignancy develop this process.
Most common lesions associated with this process is small cell lung cancer (3%-10%), thymoma(15%), and POEMS syndrome(100%).
May occur in non-small cell lung cancer.
May develop before a cancer has been identified to be present.
In more than 2/3 of patients neurological symptoms precede the diagnosis of the cancer.
The signs and symptoms of PNS may be worse than that of the cancer itself.
Serum autoantibodies target neuronal cells surface proteins and are associated with cognitive impairment.
The likelihood that the Lambert-Eaton myasthenic syndrome or subacute cerebellar degeneration in a middle or elderly patient is related to a PNS is more than 50 percent (o’Neill JH).
The likelihood of a subacute sensory neuropathy or dermatomyositis being related to a PNS is about 20 percent (Sigurgeirsson B).
The likelihood of myasthenia gravis being related to a PNS is about 10 percent.
Cancers most commonly involved with PNS are small cell lung cancer, breast cancer, ovarian cancer, thymoma, neuroblastoma, plasma cell tumors and ovarian teratoma.
A search for a malignancy should be done in all patients with suspected PNS, if a malignant disease is not known to be present.