Download Thyroarytenoid muscle

EMG OF INTRINSIC
LARYNGEAL MUSCLES
•
•
•
•
•
Electrodes
Bipolar hooked wire
electrodes, 75 µm diameter
bifilar stainless steel wires
(preferred for purely
diagnostic work)
Bipolar concentric needle
electrode
Unipolar wire electrode
Unipolar needle electrode
Unipolar injection needle
electrode
EMG OF INTRINSIC
LARYNGEAL MUSCLES
• No sedation necessary
• Oxygen by nasal cannula available
• 1% lidocaine with 1:100,000
epinephrine for injection with 27gauge needle
• Equipment for and personnel
experienced in airway management
readily available (crash cart, 14gauge angiocatheter, trach set)
EMG OF INTRINSIC
LARYNGEAL MUSCLES
• Elevate back to near 90 degrees if
necessary to improve
videolaryngoscopy (most can be done
with patient supine)
• Necessary to extend neck for
exposure and placement of needles
• 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).
EMG OF INTRINSIC
LARYNGEAL MUSCLES
Palpate structures of anterior neck to definitively
identify midline, cricoid cartilage, lower border of
thyroid cartilage, thyroid notch, and hyoid bone.
Difficult in obese patients
Avoid excessive injection of local anesthetic to
allow continued palpation of structures after
injection.
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
EMG OF INTRINSIC
LARYNGEAL MUSCLES
Cricothyroid muscle
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 .
a.Too superficial: sternohyoid
b.Too deep: lateral cricoarytenoid
EMG OF INTRINSIC
LARYNGEAL MUSCLES
Cricothyroid muscle
Confirm placement with maneuvers
a.Cricothyroid: activity varies
responsively with diminished activity
with phonation at low pitch and
increased activity at high pitch
b.Sternohyoid: activity with elevation of
head (glottis open to keep LCA activity
silent)
c.Lateral cricoarytenoid: burst of
activity associated with initiation of
phonation
EMG OF INTRINSIC
LARYNGEAL MUSCLES
Thyroarytenoid muscle
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.
Too superficial: sternohyoid or cricothyroid
Too deep: through vocal fold into posterior
cricoarytenoid
Too medial: enter laryngeal lumen with EMG
recording "air" (60 cycle burst of noise)
EMG OF INTRINSIC
LARYNGEAL MUSCLES
Thyroarytenoid muscle
Confirm placement with maneuvers
a.Marked thyroarytenoid activity with
breath holding, glottal stop, and
phonation
b.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.