Anti-MAG associated cerebellar ataxia and response to rituximab

Myelin-associated glycoprotein (MAG) is a glycoprotein specific to Schwann cells. Schwann cells produce myelin for nerve cells in the peripheral nervous system. MAG also plays a role in the central nervous system (CNS) by maintaining myelin integrity and inhibiting axonal regeneration from cerebellar neurons. There is a well-established link between distal demyelinating neuropathy and anti-MAG antibodies in patients with monoclonal gammopathy of unknown significance. We describe a series of five patients with anti-MAG antibodies with evidence of cerebellar rather than just sensory ataxia and our experience of treatment with rituximab.

Cerebellar ataxia was clinically suspected and confirmed using magnetic resonance spectroscopy (MRS) of the cerebellum. All patients underwent detailed nerve conduction studies.

Four patients were males. The ages ranged from 64 to 82 years. All patients were anti-MAG positive and also had IgM monoclonal gammopathy. Four patients had neuropathy, whilst one had no evidence of neuropathy. All patients were treated with rituximab and showed improvement in the MRS parameters of the cerebellum.

Anti-MAG antibodies might be involved in the pathogenesis of idiopathic sporadic ataxias, even in the absence of peripheral neuropathy. Rituximab seems to be a promising therapeutic intervention for those cases.