Résumé :
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The objective of this study was to determine clinical, electrophysiological and biological characteristics of chronic sensory ataxia associated with anti-GD1b IgM antibodies. Anti-GD1b antibodies had been associated with acute and chronic sensory neuropathies. Place of theses neuropathies among CANOMAD and CIDP is still discussed. We retrospectively studies patients presenting with chronic sensory ataxia in whom anti-GD1b antibodies were significantly elevated. 12 patients satisfied these conditions (6 men and 6 women, mean age 56 years). An electrophysiological examination and a CSF analysis were performed for all patients. Sera were tested for anti-GD1b, GQ1b, GM1 and anti-MAG antibodies. 11 of them were treated with at least one IVIg infusion. Six patients had anti-GD1b and anti-GQ1b IgM antibodies suggesting an antidisialosyl profile. They all had pure sensory symptoms and cranial nerve involvement in 4/6. Electrophysiology was suggestive of a ganglionopathy or a pure sensory neuropathy and was normal in one patient. These findings were suggestive of CANOMAD, but this syndrome was complete in only one patient. They all were treated by IVIg and 3/6 improved at least partially. Six patients had only anti-GD1b IgM antibodies. 4 patients had sensori-motor symptoms, whereas the two others had only sensory symptoms. Cranial nerve involvement was associated in 3/6. Electrophysiology was suggestive of a sensory or sensori-motor neuropathy in 4 patients, and of a demyelinating neuropathy suggestive of CIDP in the two others. 4/6 improved with IVIg. Anti-disialosyl antibody profile was associated with pure sensory ataxia without any motor involvement frequently associated with IgM gammopathy. These findings were strongly suggestive of CANOMAD, which is exceptionally present in his full description in our study. Isolated GD1b IgM antibodies are associated with either axonal either demyelinating sensory or sensori-motor neuropathies. Nevertheless, whatever electrophysiological profile was, chronic sensory ataxia associated with anti-GD1b antibodies improved with IVIg in 2/3 patients.
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