To the Editor: In the Case Record involving a 38-year-old manwith multifocal motor neuropathy, discussed by Triggs and Cros(Dec. 27 issue),1 Triggs emphasizes that it is important todistinguish multifocal motor neuropathy from amyotrophic lateralsclerosis or other motor neuron diseases because it respondsfavorably to immunotherapy. He mentions that plasma exchange,cyclophosphamide, and intravenous immune globulin are all beneficial.However, only treatment with intravenous immune globulins hasbeen shown to be beneficial in randomized, controlled trials.2Cyclophosphamide has been reported to be effective but onlyanecdotally, and its toxicity precludes long-term use, whichis usually necessary in patients with multifocal motor neuropathy.Plasma exchange is a well-established therapy in other immune-mediatedneuropathies, such as chronic inflammatory demyelinating neuropathy,but has not been shown to be effective in patients with multifocalmotor neuropathy and may lead to deterioration with respectto symptoms.3,4,5
Elisabeth A. Cats, M.D. W-Ludo van der Pol, M.D., Ph.D. Leonard H. van den Berg, M.D., Ph.D. University Medical Center Utrecht 3584 CX Utrecht, the Netherlands e.cats{at}umcutrecht.nl
References
Case Records of the Massachusetts General Hospital (Case 40-2007). N Engl J Med 2007;357:2707-2715. [Free Full Text]
van Schaik IN, van den Berg LH, de Haan R, Vermeulen M. Intravenous immunoglobulin for multifocal motor neuropathy. Cochrane Database Syst Rev 2005;2:CD004429-CD004429. [Medline]
Carpo M, Cappellari A, Mora G, et al. Deterioration of multifocal motor neuropathy after plasma exchange. Neurology 1998;50:1480-1482. [Free Full Text]
Claus D, Specht S, Zieschang M. Plasmapheresis in multifocal motor neuropathy: a case report. J Neurol Neurosurg Psychiatry 2000;68:533-535. [Free Full Text]
Feldman EL, Bromberg MB, Albers JW, Pestronk A. Immunosuppressive treatment in multifocal motor neuropathy. Ann Neurol 1991;30:397-401. [CrossRef][ISI][Medline]
The discussant replies: I agree with Cats and colleagues thatplasma exchange has not been shown to be effective in multifocalmotor neuropathy. In describing therapy for multifocal motorneuropathy, the published article states, "Plasma exchange,cyclophosphamide, and intravenous immune globulin are all beneficial. . . ."However, in my original discussion of this case, I mentionedtreatment with plasma exchange only in reference to early reportsdescribing treatment of multifocal motor neuropathy with plasmaexchange and cyclophosphamide in combination. My original statementwas as follows: "Initial treatment studies described beneficialeffects of plasma exchange and cyclophosphamide. Prednisone,in contrast, is ineffective and may worsen the disease. Subsequentstudies have demonstrated the beneficial effects of intravenousimmunoglobulin in multifocal motor neuropathy and the favorablerisk-to-benefit ratio of this therapy relative to that of cytotoxictherapy has made IVIg the initial treatment of choice in thesepatients." This statement was changed during the editorial process,and the change erroneously implied that treatment of multifocalmotor neuropathy with plasma exchange is beneficial.
William J. Triggs, M.D. McKnight Brain Institute Gainesville,FL 32611
Correction
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Triggs and Cros, 
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