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[Electromyography of the infrahyoid muscles - part 3: findings after transposition as a myofascial flap in tongue reconstruction].

BACKGROUND
Due to the preservation of its nerval supply the neurovascular infrahyoid muscle flap in tongue reconstruction enables to prevent atrophy of the musculature. In this study the integrity of the infrahyoid muscles (IHM) after transposition into the oral cavity was examined by means of electromyography.


METHODS
17 patients after partial or complete reconstruction of the tongue with IHM were studied at varied times after surgery. The IHM in the oral cavity was inserted by a concentric needle electrode and activity at rest as well as the discharge pattern at maximal voluntary innervation was evaluated. During light voluntary activity a motor unit potential (MUP) analysis were performed.


RESULTS
13 of 17 patients (76,5 %) in total revealed electromyographic activity in the transfered IHM flaps. Within the first 6 months after surgery 71,5 % of the patients or 77,8 % of the IHM flaps showed activity. After 6 months in 61,5 % of the patients or 64,7 % of the IHM flaps muscular activity was demonstrated. In 84,6 % of the patients or 88,2 % of the flaps we could detect neurogenic lesions at least once. Maximal voluntary contraction showed a discrete activity pattern in 63 %. In 26 % of all cases we found a discrete to reduced interference pattern and in 10 % a reduced interference pattern.


CONCLUSIONS
Functioning muscle tissue could be demonstrated in the most IHM flaps, but almost all of the studied muscles showed neurogenic lesions with a loss of motor units due to the traumatic surgery. Maybe bioelectrical stimulation of the Ansa cervicalis with implantable amplifiers will lead to better flap contractility in the future.