Sphenopalatine ganglion block is useful in the treatment of acute migraine headache, acute cluster headache, and a variety of facial neuralgias, including Sluder, Vail, and Vidian neuralgias, as well as Gardner syndrome (Table 3.1). Rarely, tumors or masses that compress or irritate the sphenopalatine ganglion may cause symptoms that mimic these facial neuralgias (Fig. 3.1). The technique has also been utilized in the treatment of status migrainosus and chronic cluster headache. Anecdotal evidence suggests that sphenopalatine ganglion block may also play a role in the palliation of pain secondary to acute herpes zoster involving the trigeminal nerve as well as postdural puncture headaches in obstetrical patients. The lateral infrazygomatic approach to sphenopalatine ganglion block is indicated in patients who have anatomic abnormalities of the nose that would preclude the use of the transnasal approach to sphenopalatine ganglion block. The lateral infrazygomatic approach is the preferred route for neurodestructive procedures of the sphenopalatine ganglion. Neurodestruction of the sphenopalatine ganglion may be carried out by the injection of neurolytic agents, the use of radiofrequency lesioning, or the use of cryoneurolysis.

The sphenopalatine ganglion, which is also known as the pterygopalatine, nasal, or Meckel ganglion, is located deep within the pterygopalatine fossa lying just posterior to the middle turbinate beneath a thin layer of lateral nasal mucosa (Fig. 3.2). It lies just below the maxillary nerve as it traverses the pterygopalatine fossa, appearing suspended from the maxillary nerve by its two interconnecting branches (Fig. 3.3). It is the largest of the parasympathetic ganglion and provides innervation to the paranasal sinuses, the lacrimal glands, and the glands associated with the mucosa of the nasopharynx and hard palate. It also sends fibers to the carotid plexus, gasserian ganglion, and trigeminal nerves as well as to the facial nerve and the superior cervical ganglion. The sphenopalatine ganglion is triangular in shape and is 5 to 6 mm in size. The sphenopalatine ganglion can be blocked by the topical application of local anesthetic via the transnasal approach, by intraoral injection through the greater palatine foramen, or by the lateral infrazygomatic placement of a needle via the coronoid notch.

Ultrasound-guided sphenopalatine ganglion block via the lateral infrazygomatic approach is a straightforward technique if attention is paid to the clinically relevant anatomy. The success rate of the technique can be increased by the concurrent use of a nerve stimulator to help confirm exact needle placement. To perform ultrasound-guided sphenopalatine ganglion block via the lateral infrazygomatic approach, the patient is placed in supine position with the cervical spine in the neutral position. The mandibular notch provides easy access to the pterygopalatine fossa and the sphenopalatine ganglion (Fig. 3.4). The mandibular 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. Once the mandibular notch is identified, the patient is asked to hold his or her mouth open in a relaxed, neutral position.