Design
An open-label pilot study of intravenous infusions of high-dose immunoglobulin administered once a month for 3 months in nine patients with classic amyotrophic lateral sclerosis. Selected patients had a rapidly progressive course with signs of worsening noticeably evident every 6 weeks prior to therapy. A patient with multifocal motor neuropathy with conduction block that presented as a lower motor neuron syndrome was concurrently treated to document the efficacy of the same preparation of immunoglobulin in a potentially treatable disease that simulates lower motor neuron syndrome. The efficacy of high-dose intravenous immunoglobulin infusions was assessed by objective measurement of maximum voluntary isometric contraction in all muscle groups of two limbs before and after therapy.

Setting
The Clinical Center of the National Institutes of Health, Bethesda, Md.

Results
All patients with amyotrophic lateral sclerosis worsened during the study. By the end of the third month, their mean total muscle scores (megascores) had declined by 71.2 points, from a mean of 369.7 (range, 200 to 605) to 298.5 (range, 130 to 552) points. The pace of progression did not change during the 4-month observation period. In contrast, the patient with multifocal motor neuropathy responded to intravenous immunoglobulin therapy and increased his megascores by 146 points after 3 months. The GM₁ antibody titers were normal in all the patients.

Conclusions
High-dose intravenous immunoglobulin, a prohibitively expensive drug, has no apparent therapeutic role in improving the symptoms or arresting the pace of progression in patients with amyotrophic lateral sclerosis. In contrast, multifocal motor neuropathy is an immunopathologically different disease that responds to intravenous immunoglobulin therapy.