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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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PLACEMENT

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 ). 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.

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Figure 22-1  Mandibular block anatomy: peripterygoid relations.


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Figure 22-2  Coronal anatomy: peripterygoid relations.


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


Position.

The patient is placed in the supine position, with the head and neck turned away from the side to be blocked. As with the approach used for maxillary block, the patient is asked to open and close the 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 then 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 then impinges on the lateral pterygoid plate at a depth of approximately 5 cm (needle position 1). The needle is withdrawn and redirected in small steps to “walk off” the posterior border of the lateral pterygoid plate in a horizontal plane (see Fig. 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, and the needle would enter the pharynx if inserted more deeply. Once the needle tip is appropriately positioned, 5 mL of local anesthetic is administered.

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


Potential Problems.

As with maxillary nerve block, the lateral approach to the mandibular nerve requires needle insertion through a vascular region. Thus, hematoma formation is possible. If a hematoma does occur, most often watchful waiting is all that is required. Although it is more difficult to enter the cerebrospinal fluid (CSF) through the foramen ovale from the lateral approach, one must be constantly aware that if a needle is inserted through the foramen ovale into Meckel’s cave small doses of local anesthetic in the CSF can produce unconsciousness.

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