Brown, Andrew E.

Abstract Purpose We describe the case of a 22-year-old male who developed thyroid storm necessitating therapeutic plasma exchange (TPE). The patient’s past medical history was complicated by epilepsy, for which he took lacosamide. Little evidence was available to guide lacosamide dosing during TPE. Because of an exacerbation of the patient’s underlying epilepsy in the context of the thyroid storm, we conducted therapeutic medication monitoring of lacosamide concentrations to guide management. Summary We arranged for measurement of the lacosamide concentration immediately before TPE (5.1 μg/mL) and 2.5 hours after the initial measurement (3.4 μg/mL) to determine the amount of lacosamide removed by TPE. Utilizing population pharmacokinetic parameters, we calculated the expected concentration and compared this to the measured concentration. The difference between these values was used to determine the percentage removed via TPE compared to the expected post-TPE concentration. We found that one TPE session removed an additional 20% of serum lacosamide. Conclusion TPE appeared to remove an additional 20% of lacosamide when compared to the expected post-TPE concentration.

Autoimmune movement disorders are increasingly recognized, but isolated tremor is extremely rare. We describe a 70‐year‐old male with rapidly progressive, severe postural and intention tremor and weight loss. His cerebrospinal fluid was inflammatory and harbored a neural tissue‐restricted antibody. The autoantigen was identified by immunoprecipitation and mass spectrometry and confirmed by antigen‐specific assays to be specific for tenascin‐R. He was investigated for cancer and diagnosed with follicular lymphoma that expressed tenascin‐R suggesting a paraneoplastic origin; cancer treatment and immunotherapy led to complete recovery. With this individualized patient approach and antibody discovery, we expand the spectrum of antibodies accompanying autoimmune hyperkinetic movement disorders. ANN NEUROL 2023;94:502–507