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Myokymia is usually recognized as continuous
involuntary fine movements of the muscle. It is a very rare
condition and occurs mostly as focal or segmental myokymia in
association with a history of radiotherapy, facial myokymia in
inflammatory demyelinating diseases or neurovascular
connection syndromes, brainstem neoplasms, Guillain-Barrésyndrome
or other intramedullary pontine lesions. Therefore,
detection of myokymic discharges in EMG will guide differential
diagnosis. We here report two patients with the unusual
appearance of unilateral myokymia of the tongue with different
aetiologies.
Patients: Case 1: A 48-year old woman presented with
permanent involuntary undulating painless movements of the
tongue. Three years ago she underwent postsurgical gamma
knife radiosurgery for an ipsilateral cerebello-pontine angle
schwannoma. Repeated magnetic resonance imaging (MRI)
of the brain did not reveal any evidence of tumour recurrence.
Case 2: A 43-year old man presented with recurrent rippling and
quivering movements of the tongue for approximately one year.
These episodes last for some seconds and occur several times
a day. He described swelling in his tongue which caused speech
difficulties. MRI scan of the brain disclosed a space occupying
meningioma in the area of the hypoglossal canal with
accompanying displacement of the medulla oblongata as the
underlying lesion.
Results: In both cases needle electromyography revealed
myokymic discharges of the tongue guided by clinical suspicion.
They are characterized by rhythmic, grouped, spontaneous
repetitive discharges, which originate from spontaneous
depolarization or ephaptic transmission along demyelinated
segments of the nerve. This finding is suggestive of a
hypoglossal nerve lesion leading to hyperexcitability of the
nerve membrane.
Conclusion: Myokymia of the tongue is a very rare condition
and is much less common then facial or other focal myokymia
syndromes. Different aetiologies as former radiotherapy and a
space occupying meningioma of the cerebrospinal passage
affecting the hypoglossal nerve caused myokymia in the two
cases presented here. With this report we aim to raise clinical
suspicion of tongue myokymias and underline the high clinical
and electromyographic impact of myokymias with regard to
differential diagnosis.