Patient Selection

Patients appropriate for this block are those with facial neuralgias and those with significant cardiopulmonary disease who require a surgical procedure in the region innervated by the mandibular nerve.

Pharmacologic Choice

Because small volumes (5 mL) of local anesthetic will produce regional block of the mandibular nerve, virtually any local anesthetic agent is an acceptable choice.

Anatomy

The mandibular nerve is a mixed motor-sensory nerve, although it is primarily sensory. It exits from the cranium through the foramen ovale and parallels the posterior margin of the lateral pterygoid plate as it descends inferiorly and laterally toward the mandible (Figs. 22-1 and 22-2). The anterior division of the mandibular nerve is principally motor and supplies the muscles of mastication, whereas the posterior division is principally sensory and supplies the skin and mucous membranes overlying the lower jaw and skin anterior and superior to the ear (Fig. 22-3).

Figure 22-1. Mandibular block anatomy: peripterygoid relationships.

Figure 22-2. Coronal anatomy: peripterygoid relationships.

Figure 22-3. Mandibular nerve (V3): cutaneous innervation.

Sensory branches of the mandibular nerve are the buccal, auriculotemporal, lingual, and inferior alveolar nerves. The buccal nerve is exclusively sensory and supplies the mucous membranes of the cheek. The auriculotemporal nerve passes posterior to the neck of the mandible to supply the skin anterior to the ear and extends into the scalp’s temporal region. The lingual nerve is joined by the chorda tympani branch of the facial nerve, and together they supply taste and general sensation to the anterior two thirds of the tongue and sensation to the floor of the mouth, including the lingual aspect of the lower gingivae. The inferior alveolar nerve supplies the lower teeth and terminates as the mental nerve, which supplies sensation to the lower labial mucous membranes and skin of the chin.

Position

The patient is placed in the supine position, with the head and neck turned away from the side to be blocked. As in the approach used for maxillary block, the patient is asked to open and close his or her mouth gently while the anesthesiologist palpates the mandibular notch to identify it more clearly.

Needle Puncture

The needle is inserted in the midpoint of the mandibular notch and directed to reach the lateral pterygoid plate by taking a slightly cephalomedial angle through the notch, as shown in Figure 22-4. The 22-gauge, 8-cm needle will impinge on the lateral pterygoid plate at a depth of approximately 5 cm (needle position 1). The needle is then withdrawn and redirected in small steps to “walk off” the posterior border of the lateral pterygoid plate in a horizontal plane (needle position 2), as shown in Figure 22-4. The needle should not be advanced more than 0.5 cm past the depth of the pterygoid plate because the superior constrictor muscle of the pharynx is easily pierced; thus, the needle will enter the pharynx if it is inserted more deeply. Once the needle tip is appropriately positioned, 5 mL of local anesthetic is administered.

Figure 22-4. Mandibular block anatomy: needle insertion technique.