Intraoperative monitoring: normative range associated with normal postoperative glottic function

Area of Science:

• Otorhinolaryngology
• Neurosurgery
• Surgical Oncology

Background:

• Intraoperative nerve monitoring (IONM) is increasingly used in thyroid surgery.
• Limited data exists on normative electrophysiologic electromyographic (EMG) parameters for recurrent laryngeal nerve (RLN) monitoring.
• Establishing these parameters is crucial for assessing nerve function during surgery.

Purpose of the Study:

• To define normative EMG parameters for RLN intraoperative neuromonitoring.
• To correlate these parameters with normal postoperative vocal cord function.
• To provide objective criteria for intraoperative decision-making.

Main Methods:

• Prospective data collection at a tertiary care center.
• Quantitative analysis of evoked waveform amplitude and threshold in 167 nerves from 125 patients.
• Correlation of intraoperative EMG data with postoperative vocal cord function assessment.

Main Results:

• A final intraoperative amplitude range of 247-3607 μV predicted normal postoperative vocal cord function.
• Lower amplitudes (average 97.5 μV) in two patients correlated with transient paralysis.
• Final amplitude effectively predicted postoperative RLN function immediately after surgery.

Conclusions:

• Proposed IONM EMG data criteria can predict normal postoperative vocal cord function.
• These criteria offer real-time information on nerve status during thyroid surgery.
• This allows for surgical strategy adaptation, especially in bilateral procedures, to prevent paralysis.