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Do A-waves help predict intravenous immunoglobulin response in multifocal motor neuropathy without block?
Dale J Lange1, Rajwinder Nijjar, Andrei Voustianiouk
1Department of Neurology, Division of Neuromuscular Disease, Mount Sinai School of Medicine, New York, New York, USA. langed@hss.edu
Introduction:
Are there electrophysiological findings that predict response to intravenous immunoglobulin (IVIg) in patients with lower motor neuron (LMN) syndromes without multifocal conduction block (MCB)?
Methods:
We enrolled 9 patients with LMN syndromes without MCB to receive 18 weeks of IVIg therapy. Response was measured at weeks 2 and 18 using the Appel Amyotrophic Lateral Sclerosis (AALS) score (includes grip and pincer strength measures), ALS Functional Rating Scale (ALSFRS), and electrophysiological measures, including motor unit estimates (MUNEs).
Results:
No change occurred in AALS or ALSFRS scores posttreatment. Grip/pincer strength increased in 7 patients (P = 0.028) after initial treatment (responders); 2 showed no improvement (non-responders). No electrophysiological measure changed after treatment in either group but MUNEs trended higher (P = 0.055). "Abnormal A-waves" (complex, repetitive biphasic, or present in multiple nerves) occurred in pretreatment studies more often in responders (P = 0.028).
Discussion:
"Abnormal A-waves" may signal IVIg-responsive LMN syndromes even if conduction block is absent.
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