The LSUHSC New Orleans Emergency Medicine Interest Group Presents The Student Procedure Manual

Nerve Blocks in the Head and Neck

by Chris Gaffga

General information
Blocking the Ear
-Indications
-Review of Anatomy
-Procedure
Blocking Cervical Plexus Innervation to the Ear
-Procedure
Block of Supraorbital, Supratrochlear Nerves
-Indications
-Review of Anatomy
-Procedure
References

General information

Most of the cranial nerves including IX and X can be blocked, as can the cervical plexus, but these are difficult procedures with limited usefulness and high risk. A few blocks in the head and neck do have emergency department applications.

Blocking the Ear

Indications

Repair of the external ear, not including the external auditory meatus.

Review of anatomy

• The external ear is innervated by branches of the cervical plexus posteriorly (lesser occipital n. and great auricular n.) and anteriorly by the auriculotemoral nerve,, a branch of the trigeminal nerve.
• The external auditory meatus innervated by the auriculotemporal nerve as well as cranial nerves VII, IX, and X, but this block does not include these nerves.

Warning: Particularly note that high pressure in a syringe can drive anesthetic into (low pressure) veins which communicate with the cranial fossa. Since anesthetic in the CNS can cause convulsions and respiratory failure, go slowly and use low pressures.

Procedure

1. Use a 10 mL syringe, a 27-gauge needle with a beveled tip.
   
2. Consult with the attending regarding dosage.
   
3. Place the patient in a supine position, tilt the head so that the ear to be anesthetized is exposed.
   
4. Locate the superficial temporal artery by feeling its pulse just anterior to the auricle. Recall that the auriculotemporal nerve wraps around the posterior surface of the ramus of the mandible to join this artery.
   
5. Position the needle at the superior border of the zygomatic arch, just anterior to the artery. Angle the needle inferiorly and insert it parallel to the nerve and artery.
   
6. Push the needle through the derrnis and into the subcutaneous layer, but keep it above the zygoma.
   
7. Push the needle down along the ramus of the mandible for about 3 cm, keeping it superficial, but subcutaneous.
   
8. Aspirate the needle to ensure that it does not lie in a vessel. Inject the anesthetic very slowly. Remember that high pressures can drive anesthetic into nearby structures (pterygoid plexus) which communicate with the cranial fossa.
   
9. Continue injecting the anesthetic as you withdraw the needle.

The Cervical Plexus Innervation to the ear is anesthetized.

Procedure

Use a 10 mL syringe, 27 gauge needle with a beveled tip
Dosage: 5-8 mL of 1% Lidocaine without epinephrine

1. Prepare the skin for aseptic injection.
   
2. Angle the needle inferiorly and pierce the skin posterior to the ear (over the mastoid process), about halfway up the height of the ear.
   
3. Moving in a plane just below the dermis, push the needle inferiorly and anteriorly (toward the angle of the mandible).
   
4. Continue pushing the needle 1.5 cm past the mastoid process. It is very important to keep the needle very superficial to avoid damaging several important structures in this area (CN VII, external carotid artery)
   
5. At a point 1.5 cm past the mastoid process, aspirate the needle.
   
6. Begin injecting very slowly. Continue injecting while withdrawing the needle.

Block of Supraorbital, Supratrochlear Nerves

Indications

• This block gives an anesthetic area extending from the eyebrow ridge to the vertex of the head, so it is useful in repairing scalp lacerations or removing cysts.

Review of anatomy

• The supraorbital and supratrochlear nerves are terminal branches of CN V The supraorbital nerve emerges from the skull above the iris, slightly medial to the pupil when the patient is looking straight ahead. The supratrochlear nerve comes out of the orbit above the medial "comer" of the eye (medial canthus).

Warning: Note that high pressure in a syringe can drive anesthetic through the supraorbital vein, or the emissary veins of the scalp. Since anesthetic in the cranial fossa can cause convulsions and respiratory failure, go slowly and use low pressures.

*A block in this region of the head is comparatively simple. However, depending on the state of vasoconstriction, this may still be a fairly vascular area, so be careful to aspirate the syringe to avoid intravascular injection.

Procedure for a supraorbital block

1. Use a 10 mL syringe with 27 gauge needle, about 7 cm long with beveled tip.
   
2. Dosage: 2-4 mL of 1% Lidocaine with out epinephrine for each side.
   
3. Prepare an area for injection just above the plane of the eyebrows in the midline of the body. An insertion below the level of the eyebrows increases the risk of periorbital hematoma
   
4. Insert the needle just deep to the dermis, and push it laterally to a point just past the vertical plane of the pupil.
   
5. Aspirate the needle to make sure that the injection will not be intravascular.
   Slowly inject anesthetic in the region of the supraorbital nerve, withdraw the needle to a point over the supratrochlear nerve and block this nerve.
   
6. Both sides of the scalp can be anesthetized with a single insertion of the needle. When finished injecting one side withdraw the needle only enough to reorient it toward the other side. The needle can then be pushed subdermally to anesthetize the other supraorbital and supratrochlear nerves.

References

Cousins, Michael J. and Bridenbaugh, Phillip O. Neural Blockade in Clinical Anesthesia and Management of Pain. J.B. Lippincott and Company, 1991.

Ferrera, Peter C and Chandler, Richard. Anesthesia in the Emergency Setting: Parts I and II; American Family Physician (1994;50: 569, 570) Sept I and 15 1994.

Orlinsky, Micheal and Dean, Edward. Anesthetic and Analizesic Techniques in Clinical Procedures in Emergency Medicine, second edition. Roberts, James and Hedger, Jerris, eds. W.B. Sanders Company. 1991