A 42-year-old man with thymoma-associated myasthenia gravis presented with 6 weeks of abnormal leg movements. Examination revealed myoclonus in the legs bilaterally (video, links.lww.com/WNL/A322). Chest CT showed recurrence of metastatic thymoma. MRI spine revealed nonspecific hemosiderin deposition at the T9 level without metastases or vascular malformation. EMG demonstrated right leg and rectus abdominus myoclonus up to T6, most prominently at T9-L1 (figure). Serum anti-contactin-associated protein-like 2 (Caspr2) antibodies were positive. Chemotherapy led to resolution of the myoclonus. Caspr2 antibodies have been associated with limbic encephalitis and neuromyotonia,1,2 but our patient showed unusual Caspr2-associated spinal myoclonus.
From Stanford University School of Medicine (H.H.); and Department of Neurology and Neurological Sciences (N.M.M., S.A., S.J., C.A.G.), Stanford University Medical Center, CA.
EMG demonstrates an unusual decrescendo firing pattern which, to our knowledge, has not been previously described. Myoclonic bursts varied between 600 milliseconds and 1.8 seconds in duration.
Author contributions
Harrison Hines: clinical patient care, acquisition of video data, drafting/revising the manuscript, accepts responsibility for conduct of research and final approval. Nick M. Murray and Sarah Ahmad: clinical patient care, critical revision of the manuscript. Safwan Jaradeh: clinical patient care, analysis of EMG studies. Carl A. Gold: clinical patient care, study supervision, critical revision of the manuscript.
Study funding
No targeted funding reported.
Disclosure
The authors report no disclosures relevant to the manuscript. Go to Neurology.org/N for full disclosures.
Acknowledgment
The authors thank Dr. Sarah Yang for help in obtaining and interpreting the EMG results.
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Video: links.lww.com/WNL/A322
- © 2018 American Academy of Neurology
References
Disputes & Debates: Rapid online correspondence
- Tipton et al. response to author
- Author response to Tipton et al.
- Reader response: Paraneoplastic spinal myoclonus associated with Caspr2 antibodies
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