Simon NG, Ayer G, Lomen-Hoerth C.
Submitted by Andrew Tarulli, MD
About the Study
Simon and colleagues report the results of treatment of 31 consecutive patients with focal-onset lower motor neuron (LMN) pattern limb weakness with intravenous immunoglobulin (IVIg). None of the patients had electrodiagnostic signs of a generalized motor neuron disorder or evidence of conduction block. Patients were treated with an IVIg dose of 2 g/kg for a minimum of 3 months. Only 3 of 31 patients responded. The authors concluded that the findings do not support uniform use of IVIg in patients with progressive LMN-type weakness.
A pattern of purely LMN-type weakness, often of the upper extremity, is a common problem in neuromuscular practice. In such patients without explanatory spine disease, a focal presentation of amyotrophic lateral sclerosis and multifocal motor neuropathy with conduction block are the primary considerations. When more diffuse signs of denervation and conduction block (or at least signs of acquired demyelination) are not present, establishing a diagnosis is very challenging. The most common options in such cases include waiting for clues to the diagnosis to develop or trying empiric therapy with IVIg as both a diagnostic and therapeutic measure.
In this, the largest prospective study of empiric IVIg treatment in patients with progressive LMN weakness, a response was identified in fewer than 10%. None of the patients who responded to IVIg would go on to develop other signs of ALS, while amongst those who did not respond, 43% developed clinical upper motor neuron (UMN) signs, 32% would develop bulbar symptoms, and 25% would develop progressive LMN weakness and be diagnosed with progressive muscular atrophy (PMA). Elevated anti-GM1 ganglioside antibodies were detected in 2 of 3 responders. The likelihood of IVIg responsiveness in a patient with a pure LMN syndrome and negative anti-GM1 ganglioside antibody titers is low.
About the News Science Editorial Board
The board helps to highlight significant, timely science news items for AANEM members. It reviews articles in journals and websites, identifies newsworthy items in the field each month, and writes article summaries.
Board members: Zaeem Siddiqi, MD, PhD (chair); Shan (Sarah) Chen, MD, PhD; Brent Goodman, MD; Ileana Howard, MD; Nicholas Johnson, MD; Carlos Luciano, MD; Andrew Tarulli, MD; Leigh Maria Ramos-Platt, MD