Backgrounds: Unilateral vocal cord paralysis caused from recurrent laryngeal nerve (RLN) injury is not an unusual disease and may deteriorate patients'voice and swallowing outcomes. Although the long term treatment effect is encouraged, the point when to perform surgical treatment is not conclusive. Previous reports suggested late treatment principle because patients may spontaneous reinnervation to some degree within 4-5 months after injury. The vocal cord position and tone may change during reinnervation. Others delineated laryngeal synkinesis by misdirected reinnervation is common and suggested early temporary injection laryngoplasty. They implied early injection laryngoplasty may improve patients'not only short term voice outcomes but also decrease the incidence of transcervical laryngeal framework surgery as a determined surgery. However, lacking of prospective study and objective data makes the treatment-time policy still controversial. Purposes: 1. To find incidence of spontaneous reinnervation or synkinetic regeneration. 2. To detect the relationship between changing of glottal gap and laryngeal synkinesis. 3. To detect the impaction of early intracordal hyaluronic acid injection on vocal cord position change in patients with laryngeal synkinesis. Study design: Forty patients is planned to be enrolled in the study. Twenty of them will undergo hyaluronate intracordal injection at three-six month from RLN damage. The other 20 patients will follow the watch-and wait policy. Laryngoscope, laryngeal EMG (electromyography), voice analysis and voice outcome survey will be done at 3-6 month and 12-month after RLN injury. At the end of follow up, the glottal gap, voice laboratory data and quality of life will be compared. The outcomes will also be correlated with laryngeal electromyography (LEMG) data and the impact of synkinetic reinnervation.
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voice outcome
Timeframe: before intervention and at 6 month follow-up