Blockade of the Glossopharyngeal Nerve
The oropharynx, soft palate, posterior portion of the tongue, and the
pharyngeal surface of the epiglottis are innervated by the glossopharyngeal
nerve. Blockade of the glossopharyngeal nerve facilitates endotracheal
intubation by blocking the gag reflex associated with direct laryngoscopy as
well as facilitating passage of a nasotracheal tube through the posterior
pharynx. The glossopharyngeal nerve travels anterior along the lateral
surface of the pharynx, and its three branches provide sensory innervation
to the posterior third of the tongue, the vallecula, the anterior surface of
the epiglottis (lingual branch), the walls of the pharynx (pharyngeal
branch), and the tonsils (tonsillar branch). Logically, blockade of this
nerve bilaterally would result in anesthesia of those structures.
The glossopharyngeal nerve can be anesthetized using either intraoral or
extraoral (peristyloid) approaches. For the intraoral approach, the mouth is
opened the overlying mucosa is anesthetized with topical anesthetic. A
3⅓-in., 22-gauge needle is used to place 2–5 mL of local anesthetic
solution submucosally at the base of the palatoglossal fold (Figure 19–5). To perform the peristyloid
approach to the glossopharyngeal block, the patient is placed supine and a
line is drawn between the angle of the mandible and the mastoid process.
Using deep pressure, the styloid process is palpated just posterior to the
angle of the jaw along this line, and a short, small-gauge needle is seated
against the styloid process. The needle is then withdrawn slightly and
directed posteriorly off the styloid process. As soon as bony contact is
lost, 5–7 mL of local anesthetic solution are injected after careful
aspiration for blood. Both approaches involve deposition of local anesthetic
in close proximity to the carotid artery, and careful aspiration before
injection is essential.
The applications of this block are limited by the specific anatomic regions
that are innervated by the glossopharyngeal nerve. It is essential to ablate
deep pressure symptoms from the tongue base during direct laryngoscopy.
Blockade of the glossopharyngeal nerve is an integral part of effective
block combinations, which is discussed later in the text.5
Because of the high vascularity of the palatoglossal arch, accidental
vascular injection is an ever-present risk. Careful aspiration helps to
reduce this risk, but it cannot be avoided entirely. In addition,
significant absorption of local anesthetic can be expected in this region.
The addition of epinephrine to the local anesthetic solution helps to
vasoconstrict the blood vessels in the region, reducing absorption as well
as assisting in the diagnosis of intravascular injection by heart rate
monitoring. As with any injection into a highly vascular region, this
technique may be contraindicated in patients with coagulopathies or
- The glossopharyngeal nerve provides sensory innervation to the
posterior third of the tongue, the vallecula, the anterior surface of the
epiglottis (lingual branch), the walls of the pharynx (pharyngeal branch),
and the tonsils (tonsillar branch).
- It is most easily blocked where it crosses the palatoglossal arch.
- It can be blocked using one of three methods: topical spray application,
direct mucosal contact of soaked pledgets, or direct infiltration by
- Glossopharyngeal nerve block is not adequate as a solo technique to
facilitate intubation, but in combination with other techniques it is highly
Superior Laryngeal Nerve Block
The internal branch of the superior laryngeal nerve (a branch of the
vagus nerve) provides sensory innervation to the base of the tongue,
posterior surface of the epiglottis, aryepiglottic fold, and the arytenoids.
Blockade of the sensory input to this branch can often be accomplished by
mucosal saturation with local anesthetic by the inhalational and direct
topical application techniques described above. In some patients, however,
this may not provide timely adequate anesthesia for a comfortable awake
intubation. In these cases, a direct regional blockade of the superior
laryngeal nerve is desired. Regional anesthesia of the superior laryngeal
nerve can be accomplished by exploiting the anatomic course of the nerve as
it arises from the vagus nerve and descends to the larynx. The internal
branch originates from the superior laryngeal nerve lateral to the greater
cornu of the hyoid bone. In most patients, the nerve should pass
approximately 2–4 mm inferior to the greater cornu of the hyoid
bone.15 From here, it pierces the thyrohyoid membrane and
travels under the mucosa in the pyriform recess.16
After topicalization, the most popular technique for superior laryngeal
nerve block involves bilateral injections at the level of the greater cornu
of the hyoid bone. The patient is placed supine with the head extended as
much as possible. The patient's skin is cleaned with an appropriate
antimicrobial solution (eg, betadine). The cornu of the hyoid bone is
located below the angle of the mandible. It is easily identified
(particularly in men) by palpating outward from the thyroid notch along the
upper border of the thyroid cartilage until the greater cornu is encountered
just superior to its posterolateral margin (Figure 19–6). The
nondominant hand is used to displace the hyoid bone with contralateral
pressure, bringing the ipsilateral cornu and the internal branch of the
superior laryngeal nerve toward the anesthesiologist. The anesthesiologist
can then appreciate the pulsation of the carotid artery being displaced deep
to the palpating finger tip.
Surface anatomy of the larynx: (1) Cricoid cartilage;
(2) thyroid cartilage; (3) hyoid bone; (4) cornu of the hyoid bone.
A ⅝-in., 25-gauge needle is inserted in an anteroinferomedial
direction until the lateral aspect of the greater cornu is contacted
(Figure 19–7). If the needle is then walked downward toward the
midline (1–2 mm) off the inferior border of the greater cornu, the
thyrohyoid membrane is pierced and the internal branch alone is blocked. If
the needle is retracted slightly after contacting the hyoid, both the
internal and external branches of the superior laryngeal nerve are blocked.
The syringe is then aspirated, and if aspiration is negative for air and
blood, 2 mL of local anesthetic (2% lidocaine) with or without
epinephrine (1:300,000) are then injected. If aspiration results in air, the
needle tip is likely in the larynx and needs to be retracted. If blood is
encountered, the needle may have encountered a blood vessel. Given the
proximity of the carotid artery, it is advisable to withdraw the needle,
reassess the landmarks, and reattempt the procedure.
Superior laryngeal block.
Two milliliters of local anesthetic should reliably bathe the internal
branch of the superior laryngeal nerve, given its proximity to the hyoid
bone. If this volume is injected outside the thyrohyoid membrane, it is
likely to block the external branch of the superior laryngeal nerve as well.
Isolated external superior laryngeal nerve branch blockade may result in
cricothyroid muscle weakness, which eliminates its function as an airway
dilator.17 The motor input of the recurrent laryngeal
nerve is spared, however, and therefore does not result in clinically
significant change in laryngeal inlet diameters.18
The superior laryngeal nerve can also be approached in the pre-epiglottic
space. The pre-epiglottic space is accessed at a point 2 cm lateral to the
thyroid notch. The needle is advanced 1–1.5 cm superoposteriorly to pierce
the thyrohyoid membrane, and the nerve can be blocked. Alternatively, using
the thyroid cornu as a landmark and walking the needle superoanteromedially
can accomplish this block.
Some patients may be unwilling or unable to undergo such injections. Common
reasons include patient refusal, anticoagulation, and distorted anatomy due
to tumors, arteriovenous malformations, surgical deformities, or
reconstruction. In patients in whom injection is contraindicated or overly
challenging, a less invasive technique for blocking the superior laryngeal
nerve can be accomplished by using soaked pledgets. After topicalization,
the patient is asked to stick the tongue out. The tongue is then grasped
using a gauze pad. With a right-angled forceps (Jackson-Krause forceps) the
anesthetic-soaked pledgets are placed in the pyriform fossae located on
either side of the root of the tongue. After 5–10 minutes, a sufficient
degree of anesthesia should be present for intubation.19
- The superior laryngeal nerve innervates the base of the tongue,
posterior surface of the epiglottis, aryepiglottic fold, and the arytenoids.
- Blockade is usually inadequate as a solo technique for intubation.
- Noninvasive blockade involves topicalization of the oral cavity, but this
technique often proves inadequate.
- Direct infiltration is accomplished at the level of the thyrohyoid membrane
inferior to the cornu of the hyoid bone. A reliable block with a definite
endpoint is effected by retracting the needle marginally after contacting
the greater cornu and injecting 2 mL of local anesthetic after negative
- Less invasive blockade can be accomplished by placing anesthetic-soaked
cotton pledgets into the pyriform fossae bilaterally.
Recurrent Laryngeal Nerve Block
The recurrent laryngeal nerve provides sensory innervation to the vocal
folds and the trachea. Blockade of this nerve is necessary to provide
comfort and prevent coughing while the endotracheal tube is being passed
between the vocal cords. Sufficient blockade of the recurrent laryngeal
nerve can often be accomplished using the inhalational technique previously
described. Again, some patients may not achieve a sufficient amount of
anesthesia to facilitate intubation.
Another technique for blocking the sensory input of the recurrent
laryngeal nerve is the transtracheal block. In
this technique, the cricothyroid membrane is located in the midline of the
neck. It can be located by palpating the thyroid prominence and proceeding
in a caudad direction. The cricothyroid membrane is identified as the spongy
fibromuscular band between the thyroid and cricoid cartilages
(Figure 19–8). After sterile skin preparation, the overlying skin
is anesthetized by raising a small skin wheal of local anesthetic. Then a
22- or 20-gauge needle on a 10-mL syringe with 4 mL of 4% lidocaine is
passed perpendicular to the axis of the trachea and pierces the membrane.
(Alternatively, a 20-gauge angiocath can be passed.) While the needle is
being advanced, the syringe is continuously aspirated. The needle is
advanced until air is freely aspirated, signifying that the needle is now in
the larynx (Figure 19–9). Instillation of local anesthetic at this
point invariably results in coughing. Through coughing, the local anesthetic
is dispersed, diffusely blocking the sensory nerve endings of the recurrent
laryngeal nerve. Motor function remains completely unaffected. It is
advisable to use a larger-gauge needle for this block. A more rapid delivery
of local anesthetic reduces the risk of needle-induced trauma due to
Transtracheal Block. The needle is inserted into
the trachea transcutaneously.
Transtracheal Block. Appearance of an air bubble
in the syringe while the syringe is being aspirated during continuous
advancement indicates intratracheal placement.
Direct blockade of the recurrent laryngeal nerve is contraindicated. Bilateral blockade results in upper airway obstruction, since the recurrent
laryngeal nerve provides motor innervation for all the muscles of the larynx
except the cricothyroid. In contrast, unilateral blockade typically
manifests only as transient hoarseness.
- Recurrent laryngeal nerve provides sensory innervation to the trachea
and vocal folds. Blockade facilitates comfortable passing of the
endotracheal tube into the trachea.
- This nerve can be blocked by using topicalization techniques described
- Translaryngeal block of the recurrent laryngeal nerve is easily accomplished
at the level of the cricothyroid membrane. A 10-mL syringe with a 22- or
20-gauge needle is advanced until air is aspirated into the syringe. Four
milliliters of local anesthetic are then injected, inducing coughing that
disperses the local anesthetic.
- The recurrent laryngeal nerve can also be blocked by spraying local
anesthetic via the injection port of the fiberoptic bronchoscope.
- The block density diminishes rapidly in the distal tracheo-bronchial
tree so special care should be taken to maintain the tip of the fiberoptic bronchoscope and
endotracheal tube above the carina.
Blockade of the Palatine Nerves
To allow awake nasal fiberoptic intubation, one must also provide
sensory blockade to the nasal passages. The greater and lesser palatine
nerves innervate the nasal turbinates and the posterior two thirds of the
nasal septum. The sensory input of these nerves can be blocked by topical
application of the local anesthetic into nasal passages. If this proves
inadequate, however, regional blockade of the palatine nerves can be
accomplished by blocking the pterygopalatine ganglion from which both nerves
arise. This can be accomplished noninvasively by taking a cotton-tipped
applicator soaked in local anesthetic and passing it along the upper border
of the middle turbinate to the posterior wall of the nasopharynx, where it
is left for 5–10 minutes.20
An oral approach to the pterygopalatine ganglion is described with
needle passage through the greater palatine foramen into the pterygopalatine
fossa. A percutaneous approach via the mandibular notch is usual performed
under fluoroscopic guidance for pain management. Because of technical
difficulty and the high risk for vascular injury, these techniques are
rarely needed or used for nasal-passage anesthesia during fiberoptic
intubation. They are mentioned here only for the sake of completeness and
- Nasal intubation requires blockade of the nasal passages.
- Blockade of the greater and lesser palatine nerves blocks sensation to the
nasal turbinates and posterior two thirds of the nasal septum.
- Topicalization of these structures is typically effective for intubation.
- Alternatively, the pterygopalatine ganglion can be blocked by passing a
local anesthetic-soaked cotton applicator along the upper border of the
middle turbinate to the posterior wall of the nasopharynx, where it is left
for 5–10 minutes.
- Transoral and percutaneous approaches to the pterygopalatine ganglion can be
accomplished, but technical difficulty and an increased potential for
complications preclude their routine use.
Blockade of the Anterior Ethmoid Nerve
The remaining portions of the nasal passages to be blocked are
innervated by the anterior ethmoid nerve and is usually adequately blocked
by inhalational or spray topicalization. This nerve can be selectively
blocked by direct mucosal contact application with an anesthetic-soaked
cotton applicator passed along the dorsal surface of the nose until the
anterior cribiform plate is reached. The applicator is left in this position
for 5–10 minutes.
- The anterior ethmoid nerve innervates the remainder of the nasal
- Anesthetic-soaked cotton applicator is passed along the dorsal surface of
the nose until the anterior cribiform plate is reached to achieve selective
blockade after 5–10 minutes.