24931 Ganglioside Antibody Panel, Serum (GM1B)

Screening tests are performed for IgG and IgM antibodies to GM1 and GD1b. If positive, the appropriate titer will be performed at an additional charge.

Useful for supporting diagnosis of neurological diseases, primarily motor neuron disease and motor neuropathies. Ganglioside antibodies are polyclonal autoantibodies produced at high levels directed against ganglioside (GM1 and GD1b) antisera. Gangliosides are sphingolipids that are important components of neural cell membranes. Typically, multifocal motor neuropathy begins with asymmetric upper limb weakness which becomes more generalized over many years. Sensory function is spared and reflexes are normal. The weak limbs may have atrophic muscles with fasciculation. On a clinical basis, these patients may be mistakenly diagnosed as suffering from amyotrophic lateral sclerosis (ALS). Patients with multifocal motor neuropathy do not have prominent upper motor neuron signs (spasticity) and bulbar weakness is extremely unusual. The multifocal motor neuropathy may be associated with characteristic electrophysiologic changes of conduction block in motor nerve pathways. In the clinical evaluation of patients with lower motor neuron disease or motor neuropathy, measurement of antiganglioside antibodies has become part of the diagnostic evaluation. In patients with a confirmed diagnosis of multifocal motor neuropathy, biopsy of affected nerve has shown an intensive inflammatory infiltrate in the area of conduction block. The implication of the antiganglioside antibodies and the inflammatory infiltrates in nerve is that this disorder represents an immune-mediated neuropathy which may respond to immunosuppression. Reports from other institutions and experience at Mayo Clinic have confirmed that some patients with multifocal motor neuropathy do respond well to immunosuppression. It is, therefore, important to distinguish clearly between patients with motor neuron disease and those with motor neuropathy. The estimation of antiganglioside antibodies provides 1 component of the evaluation.

High titers (>1:2,000) have been found only in patients with multifocal motor neuropathy and not with motor neuron disease. About 30% to 50% of patients with these clinical syndromes or the pure motor variant of chronic inflammatory demyelinating polyneuropathy have increased antibody titers. Increased antibody titers, therefore, appear to be a specific but not sensitive marker of those related disorders.

  For IgG and IgM antibodies directed against monosialo GM1 and disialo GD1b, 99% of 182 age- and sex-stratified normal individuals had titers <1:1,000; 99% of 121 patients with well-defined motor neuron disease had titers <1:2,000; and all patients with titers >1:2,000 had motor neuropathy.