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Regional anesthesia of the head and neck has become less popular as safer methods of general anesthesia have been developed. However, applications for these techniques still exist, especially in the postoperative and chronic pain settings. Airway anesthesia is often needed to facilitate endotracheal intubation.
The cutaneous innervation of the head and neck is provided by sensory fibers from the trigeminal nerve and the cervical plexus. Innervation of the airway comes from the vagus and glossopharyngeal nerves. Sympathetic blockade of the face and upper extremity is achieved by anesthetizing the stellate ganglion.
The trigeminal nerve divides into three main branches in the middle cranial fossa. These divisions—the ophthalmic, maxillary, and mandibular nerves—provide sensation to the eye and forehead, midface and upper jaw, and lower jaw, respectively ( Fig. 44-20A ). With the exception of the motor fibers to the muscles of mastication, carried by the mandibular nerve, these nerves are wholly sensory.
The gasserian ganglion block, approached classically through the foramen ovale, is infrequently used for producing surgical anesthesia. In the past, it was primarily applied to the diagnosis and treatment of trigeminal neuralgia; however, the increasing popularity and safety of thermocoagulation for ablation of the ganglion have rendered neurolytic blocks obsolete.
Blockade of the second and third divisions of the trigeminal nerve, as well as blockade of the peripheral branches, is occasionally useful in the diagnosis and management of pain syndromes and for discrete surgical procedures in selected patients (see Fig. 44-20B ).
The mandibular and maxillary nerves, two divisions of the trigeminal nerve, can be blocked through the same needle entry site (see Fig. 44-20B ). The maxillary nerve (i.e., second division) is blocked as it exits the skull through the foramen rotundum and crosses the pterygopalatine or infratemporal fossa between the skull and the upper jaw. The nerve terminates as the infraorbital nerve as it exits through the infraorbital foramen, where it can also be anesthetized.
The coronoid notch of the mandible is located, and with the patient's mouth closed, a 22-gauge, 8-cm needle is inserted at the inferior edge of the coronoid notch perpendicular to the skin entry site. The needle contacts the lateral pterygoid plate at a depth of about 5 cm. It is then withdrawn and redirected anteriorly and superiorly to walk off the plate and is advanced approximately 0.5 cm into the pterygopalatine fossa (see Fig. 44-20C ). Between 3 and 5 mL of local anesthetic solution produces anesthesia to the upper jaw and skin of the lower eyelid, cheek, and upper lip.
The mandibular nerve (i.e., third division) leaves the cranium through the foramen ovale and innervates the skin of the lower jaw and the skin anterior and superior to the ear by its posterior division. Peripheral sensory branches of cranial nerve V3 include the buccal, auriculotemporal, lingual, and inferior alveolar (terminating in the mental nerve) nerves. The anterior division supplies motor innervation to the muscles of mastication.
Figure 44-20
Anatomic landmarks and method of needle placement for
maxillary and mandibular nerve blocks. A, The ophthalmic,
maxillary, and mandibular nerves provide sensation to the eye and forehead, midface
and upper jaw, and lower jaw, respectively. B, The
mandibular and maxillary nerves can be blocked through the same needle entry site.
C, A needle is inserted at the inferior edge of the
coronoid notch perpendicular to the skin entry site, and after contacting the lateral
pterygoid plate, it is withdrawn and redirected anteriorly and superiorly to walk
off the plate (arrows). It is advanced approximately
0.5 cm into the pterygopalatine fossa. D, The mandibular
nerve is blocked through the same entry site as the maxillary nerve and by the same
method, except that the needle is withdrawn and redirected to walk off the posterior
border of the pterygoid plate (arrow). When it is
advanced to elicit paresthesia, the needle should not be inserted more than 0.5 cm
past the plate.
The mandibular nerve is blocked via the same entry site as the maxillary nerve. The needle is advanced along the inferior margin of the coronoid notch until the bone of the lateral pterygoid plate is contacted (about 5 cm). The needle is withdrawn and is redirected to walk off the posterior border of the pterygoid plate, and it is advanced in an attempt to elicit a paresthesia. The needle should not be inserted farther than 0.5 cm past the plate (see Fig. 44-20D ). Injection of 3 to 5 mL of anesthetic solution at this site is adequate.
The block of the maxillary nerve can be associated with hematoma formation and with the spread of the local anesthetic solution to the optic nerve, causing temporary blindness. Mandibular nerve block is not associated with major complications. If the needle is advanced past the pterygoid plate more than the recommended 0.5 cm, the pharynx may be entered, increasing the risk of contaminating the infratemporal fossa. Rarely, subarachnoid spread of local anesthetic may occur, resulting in brainstem anesthesia.[54]
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