Recurrent laryngeal nerve recovery patterns assessed by serial electromyography

Area of Science:

• Veterinary neurology
• Nerve injury and recovery

Background:

• Recurrent laryngeal nerve (RLN) injury can impair vocal fold function.
• Laryngeal electromyography (LEMG) is a tool for assessing RLN injury prognosis.
• The temporal dynamics of LEMG changes post-injury require further elucidation.

Purpose of the Study:

• To investigate the serial changes in LEMG following various types of acute recurrent laryngeal nerve injuries in a canine model.
• To establish the optimal timing for LEMG interpretation to predict RLN recovery.

Main Methods:

• Thirty-six canine recurrent laryngeal nerves underwent various injury models including crush, transection with reanastomosis, cautery, and stretch.
• Serial LEMG of thyroarytenoid muscles was performed monthly for six months post-injury.
• Vocal fold motion was assessed at six months to correlate with LEMG findings.

Main Results:

• Fibrillation potentials and positive sharp waves (signs of poor prognosis) were observed in most injuries within one month, persisting for an average of 2.26 months.
• Motor unit potentials (signs of good prognosis) began appearing around 3.61 months post-injury.
• A significant proportion (27.8%) of muscles showed mixed prognostic indicators between two and four months.

Conclusions:

• LEMG is a valuable tool for predicting recurrent laryngeal nerve recovery.
• Interpreting LEMG findings before three months post-injury may lead to an overestimation of a negative prognosis.
• Serial LEMG assessment with attention to timing is essential for accurate prognosis of RLN injuries.