Two Chinese Australian siblings from nonconsanguineous parents presented with adolescent-onset dystonia-parkinsonism with prominent anxiety. Examination revealed eyelid, lower facial, and distal upper extremity myoclonus (Video 1), which was recorded using surface EMG (Figure 1). Compound heterozygous pathogenic variants in ATP13A2 were identified, c.3176T>G (p.L1059R) and c.3253delC (p.L1088WfsX4), confirming the diagnosis of Kufor-Rakeb syndrome (KRS).1 KRS classically presents as juvenile-onset, levodopa-responsive parkinsonism combined with pyramidal signs, upgaze palsy, cognitive decline, and, uniquely, facial-faucial-finger minimyoclonus.2 This distinctive pattern of myoclonus is a useful clue to the diagnosis in affected individuals and distinguishes it from other forms of juvenile-onset parkinsonism.
Video 1
Patient 1 demonstrated action-induced eyelid, facial, tongue, and distal upper extremity myoclonus with vertical supranuclear gaze palsy and parkinsonism. Faucial myoclonus affecting the base of the tongue and palate was also present but not demonstrated on this video. Patient 2 had similar findings of parkinsonism, prominent facial and tongue myoclonus, and myoclonus affecting the fingers, particularly with action, and confirmed with surface EMG recording.Download Supplementary Video 1 via http://dx.doi.org/10.1212/200751_Video_1
Surface EMG showed both brief, synchronous <50 ms EMG bursting across facial muscles consistent with myoclonus (Panel A, wide arrows) and more sustained bursting typical of tremulous activity (Panel B, thin arrows). Upper limb surface EMG showed findings more consistent with a dystonic tremor, with continuous muscle activity present between discrete, tremulous EMG bursting (Panel C, arms extended). These neurophysiologic characteristics, to our knowledge not previously reported, demonstrate that what has been described phenomenologically as facial-faucial-finger myoclonus may have both myoclonic and tremulous features. ECR = extensor carpi radialis; FCR = flexor carpi radialis; orbi = orbicularis; R = right.
Study Funding
The authors report no targeted funding.
Disclosure
The authors report no disclosures relevant to the manuscript. Go to Neurology.org/N for full disclosures.
Acknowledgment
The authors thank Professor John Morris for his assistance in videotaping.
Appendix Authors
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.
Submitted and externally peer reviewed. The handling editor was Whitley Aamodt, MD, MPH.
Teaching slides links.lww.com/WNL/C59
- Received October 24, 2021.
- Accepted in final form April 4, 2022.
- © 2022 American Academy of Neurology
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