Chapter 30. Nerve Blocks of the Face
What of the following statements is true regarding trigeminal nerve block?
A. It is a purely sensory block.
B. It is the primary therapy for patients with trigeminal neuralgia.
C. It can be performed distally and proximally.
D. It carries preganglionic and postganglionic fibers.
C is correct. The trigeminal nerve block can be performed either distally at the respective exit points from the facial bones (V1–V3) or proximally at their emergence from the cranium (V2–V3).
A is incorrect. The trigeminal nerve is a mixed sensory and motor nerve. While it is predominantly sensory, it does also carry the motor fiber for the muscles of mastication in its mandibular branch (V3).
B is incorrect. Blockade of the trigeminal ganglion is a treatment for patients with trigeminal neuralgia who failed pharmacological therapy. A blockade with local anesthetic (LA) is typically used as a diagnostic test prior to neurolysis.
D is incorrect. The trigeminal nerve is comprised of purely postganglionic fibers. Blockade of the trigeminal ganglion achieves blockade of preganglionic and postganglionic fibers.
What statement is true regarding landmark-based superficial trigeminal nerve blocks?
A. The ophthalmic nerve (V1) enters the orbit and divides into its branches prior to exiting the orbit.
B. 3–5 mL of local anesthetic (LA) should be injected per nerve.
C. The terminal branch of V2, the infraorbital nerve, can be blocked both intra- and extra-orally.
D. The most common complication of the superficial trigeminal nerve block is penetration of the foramen.
C is correct. In the extra-oral approach, the needle is inserted perpendicular to the skin while palpating the infraorbital foramen until bony resistance is encountered. The needle is then advanced in a caudal and medial direction while keeping a finger on the foramen to prevent cephalad advancement. For the intraoral approach, the target landmark is the intersection of a vertical line through the papilla and a horizontal line through the alae of the nose. The buccal mucosa is entered between the canine and first molar and the needle advanced in an upward and outward direction.
A is incorrect. The ophthalmic nerve divides into its three branches (lacrimal, frontal, and nasociliary) prior to entering the orbit.
B is incorrect. Only 0.5 mL are necessary to achieve a successful block; 3–5 mL carry a risk of generalized seizures and/or epidural and subarachnoid anesthesia given the proximity of blood vessels.