Ultrasound-guided selective mandibular nerve block via the coronoid approach allows selective blockade of the mandibular nerve as it passes through the pterygopalatine space. The simplicity and safety of this technique lend itself to the diagnosis and treatment of a variety of painful conditions subserved by the mandibular division of the trigeminal nerve. This technique is useful in the setting of acute pain secondary to trauma, pain of malignant origin, postsurgical pain, dental pain, breakthrough pain of trigeminal neuralgia, atypical facial pain, trismus, and the pain of acute herpes zoster. It can be used in the setting of chronic pain to help manage atypical facial pain including chronic dental pain and postherpetic neuralgia (Fig. 10.1).

The trigeminal nerve is the fifth cranial nerve, and it derives its name from its three branches, the ophthalmic (V1), the maxillary (V2), and the mandibular (V3). The ophthalmic and maxillary nerves are comprised solely of sensory fibers, while the mandibular nerve has both sensory and motor fibers. The trigeminal nerve exits the pons as a single nerve root on each side of the pons. These bilateral nerve roots travel forward and laterally from the pons to form the gasserian ganglion (also known as the trigeminal ganglion), which is located in Meckel cave in the middle cranial fossa. The canoe-shaped gasserian ganglion is bathed in cerebrospinal fluid and is surrounded by dura mater.

Three sensory divisions exit the anterior convex portion of the gasserian ganglion, the ophthalmic (V1), the maxillary (V2), and the mandibular divisions, with as small motor root coalescing with the V3 division sensory fibers as the mandibular nerve leaves the middle cranial fossa via the foramen ovale (Fig. 10.2). The sensory fibers of the trigeminal nerve provide afferent light touch and proprioceptive and nociceptive functions, while the motor fibers of the mandibular nerve provide efferent innervation of the muscles of mastication, the mylohyoid muscle, the anterior belly of the digastric muscle, and the tensor tympani and tensor veli palatini muscles. While the mandibular nerve is responsible for the light touch, proprioception, and pain and temperature sensation within its area of innervation, it does not transmit taste sensation, which is transmitted by the chorda tympani.

The ophthalmic division (V1) of the trigeminal nerve exits the cranial fossa via the superior orbital fissure and transmits sensory information from the scalp, forehead, upper eyelid, the conjunctiva and cornea of the eye, most of the nose except the nasal ala, the nasal mucosa, the frontal sinuses, and the dura and some intracranial vessels. The maxillary division of the trigeminal nerve (V2) exits the cranial fossa via the foramen rotundum and transmits sensory information from the lower eyelid and cheek; the nasal ala; the upper lip, upper dentition, and gingiva; the nasal mucosa; the palate and roof of the pharynx; the maxillary, ethmoid, and sphenoid sinuses; and portions of the meninges. The mandibular division of the trigeminal nerve (V3) exits the cranial fossa via the foramen ovale and transmits sensory information from the lower lip, the lower dentition and gingiva, the chin and jaw (except the angle of the jaw, which is supplied by C2-C3), parts of the external ear, and parts of the meninges (Fig. 10.3). The nerve also transmits sensory information from the dorsal aspect of the anterior two-thirds of the tongue and associated mucosa of the oral cavity.

Ultrasound-guided selective mandibular nerve block via the coronoid approach is a straightforward technique if attention is paid to the clinical relevant anatomy. To perform ultrasound-guided selective mandibular nerve block via the coronoid approach, the patient is placed in the supine position with the cervical spine in the neutral position. The coronoid (mandibular) notch provides easy access to the pterygopalatine fossa and the maxillary and mandibular nerves (Fig. 10.4). The coronoid notch of the mandible is identified by asking the patient to open and close his or her mouth several times while palpating the area just anterior and slightly inferior to the acoustic auditory meatus (Fig. 10.5). Once the coronoid notch is identified, the patient is asked to hold his or her mouth open in a relaxed, neutral position.