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Multifocal motor neuropathy: the diagnostic spectrum and response to treatment.
Neurology J.
Slee M, Selvan A, Donaghy M.
Department of Clinical Neurology, University of Oxford, West Wing, John Radcliffe Hospital, Oxford OX3 9DU, UK.
OBJECTIVE:
To define the clinical spectrum in a large cohort of patients with
multifocal motor neuropathy (MMN) and the effectiveness of IVIg
treatment. We also test two neurophysiologic criteria for conduction
block (CB) for relevance to treatment responsiveness. METHODS:
Retrospective case cohort analysis of 47 patients with MMN followed for
up to 12 years.
RESULTS: A total of 32 (70%) had an upper-limb onset
with most showing clinical features of conduction block: weakened but
non-wasted muscles (67%) and differential weakness across muscles
supplied by a common terminal motor nerve (54%). Differential weakness
of finger extension was a characteristic early sign. Application of
consensus criteria for definite CB would have denied a trial of
treatment to 6 patients with a typical phenotype compared with new
criteria. No association was found between CB and presence of anti-GM1
ganglioside antibody. A total of 24 (51%) patients were treated with
IVIg, which was associated with a marked initial improvement in
self-reported disability in most patients. The magnitude of initial
disability improvement was not sustained in all patients over time.
However, the majority of treated patients reported significantly less
disability at last follow-up than prior to treatment. Patients
converted to a domiciliary IVIg program maintained function at least as
well as hospital treated patients. CONCLUSION: The importance of the
clinical phenotype of multifocal motor neuropathy (MMN) is emphasized.
Neither conduction block (CB) nor antibody status is a reliable
predictor of treatment responsiveness. Over-reliance upon consensus CB
criteria can deny IVIg to patients with MMN who are treatment
responsive.
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