Ultrasound-guided selective maxillary nerve block via the suprazygomatic approach provides an alternative approach to selective maxillary nerve block. The simplicity and safety of this technique lend itself to the diagnosis and treatment of a variety of painful conditions subserved by the maxillary 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, and the pain of acute herpes zoster (Fig. 9.1). The suprazygomatic approach may also be used intraoperatively as an adjunct to anesthesia during cleft palate repair. It can be used in the setting of chronic pain to help manage atypical facial pain including temporomandibular joint dysfunction and postherpetic neuralgia.

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. 9.2). 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 (Fig. 9.3). 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. 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 maxillary nerve block via the suprazygomatic approach is a straightforward technique if attention is paid to the clinical relevant anatomy. To perform ultrasoundguided selective maxillary nerve block via the suprazygomatic approach, the patient is placed in supine position with the cervical spine in the neutral position. The anteroinferior border of the zygoma and the posterior rim of the orbit are identified. At the angle where these two boney landmarks join, the examiner should feel a small depression (Figs. 9.4 and 9.5). A high-frequency linear ultrasound transducer is then placed in a transverse position in the infrazygomatic area with the posterior margin of the transducer aimed toward the tip of patient’s ipsilateral earlobe (Fig. 9.6). Under continuous ultrasound imaging, the transducer is slowly rotated until the pterygopalatine fossa


is clearly visualized. The acoustic shadow of the sphenoid will be identified anteriorly. Posteriorly, the acoustic shadow of the greater wing of the sphenoid will be evident (Fig. 9.7). Color Doppler should then be utilized to identify the internal maxillary artery and vein (Fig. 9.8). The skin overlying the injection site is prepped with antiseptic solution and under real-time ultrasound guidance, a 22-gauge, 3½-inch needle is inserted at the previously identified depression at the point where the anteroinferior border of the zygoma and the posterior rim of the orbit join (Fig. 9.9). The needle is advanced toward the greater wing of the sphenoid and reoriented until the needle enters the pterygopalatine fossa and impinges on the lateral pterygoid plate. The tip of the needle is then withdrawn slightly out of the periosteum of the lateral pterygoid plate and redirected toward the pupil of the eye until it slips past the anterosuperior margin of the lateral pterygoid plate into the pterygopalatine fissure and in proximity to the maxillary nerve. A paresthesia may be elicited, and the patient should be warned of such. After careful aspiration, 4 to 5 mL of local anesthetic and 2 to 4 mg of nonparticulate containing steroid such as dexamethasone are injected in incremental doses (Fig. 9.10). During the injection procedure, the patient must be observed carefully for signs of local anesthetic toxicity. Because of the proximity of the sphenopalatine ganglion, the patient may also experience partial blockade of this structure. The needle is removed and pressure is placed on the injection site to avoid ecchymosis.