A 49-year-old man with undifferentiated nasopharyngeal carcinoma underwent 2 cycles of chemotherapy, followed by right-side head and neck radiation therapy. Thirteen years later, he developed progressive dysphagia and dysarthria. Neurologic examination showed atrophy associated with wave-like movements and prominent rippling in the right side of the tongue; needle electromyography revealed myokymic discharges in the right genioglossus muscle (Video 1). MRI of the head and neck confirmed isolated unilateral tongue atrophy (Figure) while laryngoscopy showed delayed initiation of swallowing and reduced laryngeal elevation.
Video 1
Atrophy and myokymia of the tongue on the right side (part 1). Needle electromyography of the right genioglossus muscle shows myokymic discharges consisting of repetitive bursts from a single motor unit potential occurring at a regular interval (3 per second) with an intraburst frequency of approximately 50 Hz (part 2).Download Supplementary Video 1 via http://dx.doi.org/10.1212/201607_Video_1
Axial T1-weighted (A) and T2-weighted (B) images showing prominent right hemi-tongue atrophy (arrows). The dotted line indicates the course of the lingual septum.
Delayed effects of radiation therapy could be seen even decades later and are directly related to radiation dosage.1 Myokymic discharges of the tongue are likely due to the damage of the hypoglossal nerve induced by microvascular injury and fibrosis with subsequent hyperexcitability of the axon membrane.1 In an oncology patient, myokymia is usually associated with radiation-induced neuropathy rather than cancer recurrence.2
Study Funding
No targeted funding reported.
Disclosure
The authors report no relevant disclosures. Go to Neurology.org/N for full disclosures.
Appendix Authors
Footnotes
Go to Neurology.org/N for full disclosures.
Submitted and externally peer reviewed. The handling editor was Whitley Aamodt, MD, MPH.
Teaching slides links.lww.com/WNL/C499
- Received July 22, 2022.
- Accepted in final form October 11, 2022.
- © 2022 American Academy of Neurology
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