Session Information
Date: Tuesday, June 21, 2016
Session Title: Myoclonus
Session Time: 12:30pm-2:00pm
Location: Exhibit Hall located in Hall B, Level 2
Objective: To evaluate the accuracy of clinical phenotyping in a heterogeneous cohort of patients presenting with myoclonus and to determine clinical characteristics. Furthermore, we studied the added value of EEG-EMG back-averaging, coherence analysis, and SEP in distinguishing myoclonus subtypes.
Background: Myoclonus is a heterogeneous hyperkinetic movement disorder that can be anatomically classified into cortical (CM), subcortical (SCM), spinal (SM) and peripheral (PM) myoclonus. Accurate clinical diagnosis of myoclonus and its subtype remains challenging.
Methods: Clinical characteristics of all patients with myoclonus were reviewed retrospectively (February 2006 and May 2014). Video-EMG and accelerometry were used as gold standard tests in determining myoclonus and anatomical subtypes. We focussed on clinical phenotyping, back-averaging, coherence analysis, and somatosensory evoked potential (SEP).
Results: A total of 102 patients with myoclonus were identified; CM (38%), SCM (9%), SM (8%), PM (3%). The remaining 40% were diagnosed with functional myoclonus (FM). Electrophysiological tests supported the clinical diagnosis myoclonus in 84% and its subtype in 64% of cases. Rate of onset, preceding contributing events, and provoking action or body position were the principal differentiating clinical factors between myoclonic subtypes. Back-averaging analysis was possible in 14/25 CM cases (43% cortical correlate) and 14/28 FM cases (64% bereitschaftspotential). A cortical origin was identified in 5/11 (45%) using coherence analysis and 3/11 (27%) with SEP.
Conclusions: Clinical diagnosis, supported by video-EMG-accelerometry was accurate in the majority of cases, with CM and FM being most common. Specific clinical features (e.g. rate of onset) were helpful in distinguishing subtypes. Sophisticated electrophysiological tests can be of additional value in determination of the anatomical subtype of myoclonus. Further evaluation of the sensitivity and specificity of electrophysiological testing is required, potentially facilitating more specific diagnosis of myoclonic subtypes and enabling targeted treatment.
To cite this abstract in AMA style:
R. Zutt, J.W. Elting, H. van der Hoeven, F. Lange, M.A.J. Tijssen. How do we clinically distinguish subtypes of myoclonus? A retrospective study [abstract]. Mov Disord. 2016; 31 (suppl 2). https://www.mdsabstracts.org/abstract/how-do-we-clinically-distinguish-subtypes-of-myoclonus-a-retrospective-study/. Accessed June 14, 2025.« Back to 2016 International Congress
MDS Abstracts - https://www.mdsabstracts.org/abstract/how-do-we-clinically-distinguish-subtypes-of-myoclonus-a-retrospective-study/