CNTNAP1 and cerebellar ataxia: IgG4 antibodies directed against some of these paranodal antigens, namely neurofascin (Nfasc 155 and Nfasc 140/186), contactin-1 (CNTN1), and contactin associated protein-1 (Caspr1), result in a demyelinating polyneuropathy resembling CIDP but with distinct clinical features such as early age of onset, subacute presentation, presence of tremor and ataxia, and poor responsiveness to first-line agents (51, 52).