see also: Laryngeal EMG (Electromyography) Anatomy and Video

Laryngeal EMG with Concurrent Transnasal Laryngoscopy

Note: last updated before 2013

PREOPERATIVE PREPARATION

1. Evaluation
   1. Head and neck exam to include indirect or fiberoptic laryngoscopy.
   2. Videostroboscopy (preferable preoperatively, optimal to have video recording concomitant with electromyography EMG and voice recording).
   3. Prepare equipment and personnel
      1. Electrodes
         1. Bipolar hooked wire electrodes, 75 µm diameter bifilar stainless steel wires (preferred for purely diagnostic work)
         2. Bipolar concentric needle electrode
         3. Unipolar wire electrode
         4. Unipolar needle electrode
         5. Unipolar injection needle electrode
      2. Pre-amplifier
      3. Instrumentation amplifier: a dry run in the EMG suite to search for and eradicate 60 cycle interference is helpful before attempting clinical EMG
      4. Power amplifier and speakers (for audio monitoring)
      5. Computer with digitizing board and Windaq software for visual monitoring using oscillographic display feature
      6. Videolaryngoscopy unit coupled to television monitor and videotape recorder
      7. Microphone
      8. Medication 
         1. No sedation necessary
         2. Oxygen by nasal cannula available
         3. 1% lidocaine with 1:100,000 epinephrine for injection with 27-gauge needle
         4. Equipment for and personnel experienced in airway management readily available (crash cart, 14-gauge angiocatheter, trach set)
2. Contraindications
   1. Bleeding disorder (coagulopathy, Coumadin, aspirin)
   2. Altered anatomy precluding percutaneous placement of needle electrodes (infection, previous surgery)
   3. Inability of patient to cooperate (young children, psychiatric disorder, severely compromised health)
3. Consent
   1. Potential complications
      1. Bleeding/infection/reaction to anesthetic/damage to adjacent structures (very rare but to include voice, swallowing, breathing)
      2. Briefly describe procedure to patient as placing recording electrodes into the muscles of the voice box through the skin. Generally causes no discomfort and has been performed many times without complication.

OPERATIVE PROCEDURE

1. Preparation
   1. Place in supine position
      1. Elevate back to near 90 degrees if necessary to improve videolaryngoscopy (most can be done with patient supine)
      2. Neck in neutral position unless necessary to extend for exposure and placement of needles
   2. Inject 0.5 cc lidocaine 1% with 1:100,000 epinephrine superficially in small weal over midline cricothyroid ligament (for thyroarytenoid recording) and 1 cm inferiorly over lower border of cricoid (for CT recording).
   3. Place reference electrode on forehead
   4. Intranasal topical Neosynephrine/Pontocaine mixture aerosolized if flexible fiberoptic laryngoscopy done concomitantly (no topical laryngeal anesthetic is used)
2. Placement of Electrodes
   1. Palpate structures of anterior neck to definitively identify midline, cricoid cartilage, lower border of thyroid cartilage, thyroid notch, and hyoid bone.
      1. Difficult in obese patients
      2. Avoid excessive injection of local anesthetic to allow continued palpation of structures after injection.
      3. If tracheotomy is present, it is usually necessary to remove it for access for needle placement. Perform only on patients able to tolerate short-term removal of tracheotomy tube. May use nasal speculum placed into tracheotomy site to maintain airway during testing
   2. Cricothyroid muscle
      1. Pierce the skin in midline with electrode and direct needle posterolaterally along long axis of pars oblique aiming at lower surface of thyroid cartilage posterior to the inferior tuberculum without penetrating cricothyroid ligament .
         1. Too superficial: sternohyoid
         2. Too deep: lateral cricoarytenoid
      2. Confirm placement with maneuvers
         1. Cricothyroid: activity varies responsively with diminished activity with phonation at low pitch and increased activity at high pitch
         2. Sternohyoid: activity with elevation of head (glottis open to keep LCA activity silent)
         3. Lateral cricoarytenoid: burst of activity associated with initiation of phonation
   3. Thyroarytenoid muscle
      1. Pierce skin in midline with electrode directed superolaterally through cricothyroid ligament to depth (from skin) of 1.5 to 4 cm depending on thickness of neck and angle of entry. After needle pierces skin, TA should be entered through a submucosal approach without entering airway.
         1. Too superficial: sternohyoid or cricothyroid
         2. Too deep: through vocal fold into posterior cricoarytenoid
         3. Too medial: enter laryngeal lumen with EMG recording "air" (60 cycle burst of noise)
      2. Confirm placement with maneuvers
         1. Marked thyroarytenoid activity with breath holding, glottal stop, and phonation
         2. Position of needle electrode may be confirmed by moving electrode within substance of thyroarytenoid muscle and observing vocal fold movement with fiberoptic scope. May cause patient to swallow or cough.
      3. Data collection
         1. Note amplifier gains so recorded data can be expressed in terms of actual voltages detected by the electrodes in the muscle.
         2. The patient is asked to produce a series of phonatory tasks and laryngeal maneuvers to assess the integrity of the laryngeal muscle of interest.
         3. Record data directly to the computer using Windaq acquisition software.
      4. Configuration of recording electrodes
         1. Near-field recordings measure the voltage difference that exists between the two hooked wires of a single electrode (ie, samples the electrical activity in a small area of the muscle, able to record single motor unit activity at low levels of activity).
         2. Far-field recordings measure the voltage difference that exists between the single hooked wire in each of two separate electrodes placed in the same muscle (ie, samples a larger area of the muscle, useful in confirming paralysis).
      5. The electrodes are removed.

POSTOPERATIVE CARE

1. Observe for approximately one-half hour following procedure before discharging.
   1. May eat immediately thereafter.
   2. If any question of laryngeal injury, perform indirect or fiberoptic endoscopy to confirm adequate airway and document degree of injury.
2. Data Analysis
   1. Unilateral vocal fold paralysis
      1. Levels of EMG activity in the paralyzed (thyroarytenoid and/or cricothyroid) muscle and the contralateral muscle are measured during sustained phonation (see Figure IC-7, PDF).
   2. Vocal tremor
      1. Identify laryngeal muscles that exhibit rhythmic bursts of EMG activity during sustained phonation.

REFERENCES

Hirano M, Ohala J. Use of hooked-wire electrodes for electromyography of the intrinsic laryngeal muscles. J Speech Hear Res. 1969;12:362-273.

Hiroto I, Hirano M, Toyozumi Y, Shin T. Electromyographic investigation of the intrinsic laryngeal muscles related to speech sounds. Ann Otol Rhinol Laryngol. 1967;76:861-872.

Hirano M, Koike Y, von Leden ## The sternohyoid muscle during phonation: Electromyographic studies. Acta Otolaryngol. 1967;64:500-507.

Hoffman H, Brunberg J, Winter P, Sullivan M, Kileny P. Arytenoid subluxation: diagnosis and treatment. Ann Otol Rhinol Laryngol. 1991;100:1-9.

Thumfart W## Electromyography of the larynx and related techniques. Acta Oto Rhino Laryngol Belgic#### 1986;40:358-376.

Jaffe DM, Solomon NP, Robinson RA, et al. Comparison of concentric needle versus hooked wire electrodes in the canine larynx. Otolaryngol Head Neck Surg. 1998; 118:655-662.

Meyer TK, Hillel AD, and Blitzer A: pp 41-53 Chapter 5 "Electromyography of Laryngeal and Pharyngeal Muscles" in Neurologic Disorders of the Larynx eds Blitzer A, Brin MF, and Ramig LO Thieme Medical Publishers NY, NY 2009

Min YB, Finnegan EM, Hoffman HT, et al. A preliminary study of the prognostic role of electromyography in laryngeal paralysis. Otolaryngol Head Neck Surg. 1994;111:770, 775.

Min YB, Luschei ES, Finnegan EM, McCulloch TM, Hoffman HT. Portable telemetry system for electromyography. Otolaryngol Head Neck Surg. 1994;111:849-852.

Luschei ES, Finnegan EM. Electromyographic techniques for the assessment of motor speech disorders. In: McNeil MR, e#### Clinical Management of Sensorimotor Speech Disorders. New York.

Blitzer A, Crumley RL, Dailey SH, Ford CN, Floeter MK, Hillel AD, Hoffmann HT, Ludlow CL, Merati A, Munin MC, Robinson LR, Rosen /c, Saxon KG, Sulica L, Thibeault SL, Titze I, Woo P, Woodson GE: Recommendation of the Neurolaryngolgoy study Group on Laryngeal Electromyography. Otolaryngol Head Neck Surg. 2009 Jun;140(6):782-293 Otolaryngol Head Neck Surg. 2009 Jun;140(6):782-793.