Tongue myokymia presenting twelve years after radiation therapy.

OBJECTIVE: This case is a patient with tongue myokymia following radiation therapy 12 years earlier, documented using video and EMG. CASE REPORT: A 68-year-old woman with a history of nasopharyngeal carcinoma presented with subacute onset of difficulty in speaking and involuntary movements of her tongue approximately 12 years after radiation therapy to head and neck. Electromyography displayed myokymic discharges. There was no evidence of recurrent malignancy. SIGNIFICANCE: Delayed effects of radiation therapy might be seen decades later. Myokymic discharges may reveal radiation-induced neuropathy.

Introduction

Myokymia is a clinical phenomenon that refers to undulating rippling muscles with electrophysiological evidence of myokymic discharges. Myokymic discharges are spontaneous bursts of single motor unit potentials firing usually at rates of 5–150 Hz (might be up to 300 Hz), which may appear as doublets, triplets, or multiplets (Gutmann and Gutmann, 2004). Myokymia might be seen in patients with a history of radiation therapy, and it usually presents as brachial or lumbosacral plexopathy. Post-radiation neuropathy of cranial nerves is quite rare. Other etiological factors of facial myokymia include brainstem lesions (e.g., glioma, multiple sclerosis), posterior fossa mass lesions, Guillain–Barre syndrome, and basilar invagination (Gutmann, 1991).

Myokymia of the tongue after radiation therapy has been reported to occur several months to years following the therapy (Richardson and Weiss, 2009, Rison and Beydoun, 2009, Shin et al., 2013). We report the case of a woman who developed hypoglossal neuropathy twelve years after her radiation therapy for nasopharyngeal carcinoma.

Case report

A 68-year-old woman was referred to the Neurology clinic for involuntary tongue movements and difficulty speaking. She had been diagnosed with nasopharyngeal carcinoma in 2003. The biopsy from the mass lesion in her nose had revealed a pleomorphic giant cell mesenchymal tumor. She was treated with 2 sessions of chemotherapy followed by radical radiotherapy to the nasopharyngeal and neck areas. The total radiation dose was 5000 cGy to the neck and 5000 cGy to the nasopharynx; the dose per fraction was 200 cGy. During her follow-up, no metastatic lesions were detected. Since then, she had not experienced any problems. However, in November 2015, she developed involuntary movements of her tongue, which also disrupted her articulation during speaking. Her oncologist had examined her for recurrent or metastatic lesions, but found none. Neurological examination revealed marked atrophy and fasciculation of the tongue on the right side indicating a lesion of the hypoglossal nerve. The examination was otherwise normal. Nerve conduction studies of the peripheral nerves and needle electromyography of muscles in the limbs were normal. Needle electromyography showed myokymic discharges in the right genioglossus muscle (see Fig. 1 and the Video). The patient provided written informed consent for her clinical data and images to be used for educational purposes.

Fig. 1

(A, B) Atrophy and fasciculation of the tongue on the right side and (C) myokymic discharges in needle electromyography of the right genioglossus muscle.

Conclusion

Delayed effects of radiation therapy could be seen even decades later. The case presented here well demonstrates the long-term effects of radiation therapy on lower cranial nerves. In general, in patients with a history of radiation therapy, myokymic discharges may reveal radiation-induced neuropathy, rather than a metastatic involvement, which makes this electrophysiological finding valuable in differential diagnosis.

Conflict of interest

The authors declare that they have no conflicts of interest and nothing to disclose.