Paraneoplastic or autoimmune disorders of the peripheral or autonomic nervous system

**Definition:** Paraneoplastic and autoimmune disorders of the peripheral and autonomic nervous system result from a targeted immune attack on neurons or glial cells in the peripheral nervous systems (peripheral or autonomic neuropathies). In the paraneoplastic context, this attack is a consequence of a potentially effective tumour immune response initiated by onco-neural antigens derived from a systemic cancer. In the non-paraneoplastic context termed autoimmune the etiology remains elusive though increasing evidence indicates a preceding infectious trigger in at least some cases. Onset may be subacute or insidious and these disorders may be limited, multifocal or generalised. Autoimmune somatic peripheral nerve disorders may affect the nerve at multiple levels including root, nerve and plexus and may be axonal, demyelinating or both. Autoimmune autonomic disorders result in autonomic failure that can be partial or generalised. The prototypic autonomic neuropathy is the autoimmune ganglionopathy associated with antibodies targeting the ganglionic nicotinic acetylcholine receptor (α3 gAChR). Screening for cancer is appropriate for those with specific neural antibody profiles and other risk factors.

Associated neural antibodies in peripheral neuropathies include anti neuronal nuclear antibody type 1 or anti-Hu, CASPR2, gAChR, ganglioside (GM1 IgG and IGM) antibodies.