Chronic motor neuropathies: response to interferon-beta1a after failure of conventional therapies

The effect of interferon-beta1a (INF-beta1a; Rebif) was studied in patients with chronic motor neuropathies not improving after conventional treatments such as immunoglobulins, steroids, cyclophosphamide or plasma exchange.

A prospective open study was performed with a duration of 6-12 months. Three patients with a multifocal motor neuropathy and one patient with a pure motor form of chronic inflammatory demyelinating polyneuropathy were enrolled. Three patients had anti-GM1 antibodies. Treatment consisted of subcutaneous injections of IBF-beta1a (6 MIU), three times a week. Primary outcome was assessed at the level of disability using the nine hole peg test, the 10 metres walking test, and the modified Rankin scale. Secondary outcome was measured at the impairment level using a slightly modified MRC sumscore.

All patients showed a significant improvement on the modified MRC sumscore. The time required to walk 10 metres and to fulfil the nine hole peg test was also significantly reduced in the first 3 months in most patients. However, the translation of these results to functional improvement on the modified Rankin was only seen in two patients. There were no severe adverse events. Motor conduction blocks were partially restored in one patient only. Anti-GM1 antibody titres did not change.

These findings indicate that severely affected patients with chronic motor neuropathies not responding to conventional therapies may improve when treated with INF-beta1a. From this study it is suggested that INF-beta1a should be administered in patients with chronic motor neuropathies for a period of up to 3 months before deciding to cease treatment. A controlled trial is necessary to confirm these findings.