Sudomotor testing discriminates between subjects with and without antibodies against botulinum toxin A--a preliminary observation.

With an increasing number of patients being treated with botulinum toxin A (BTX A), the incidence of neutralizing anti-BTX antibodies (ABA) is rising. Because BTX A is known to inhibit sweating, sudometry seems to be a promising tool to test the efficacy of BTX A. We injected BTX A subcutaneously in normal control subjects and four patients with spasmodic torticollis, two responders and two nonresponders with proven ABA. Sweating was visualized using iodine starch staining and quantified used capacitance hygrometry. BTX A inhibited sweating completely at the injection site in both control subjects and all responders without evidence for ABA. However, continued sweating was recorded when the nonresponders with proven ABA were tested. We conclude that sudomotor testing is able to discriminate between subjects with and without clinically important ABA.