• Geoffrey J. Pollack, MD

        INTRODUCTION

Regional anesthetic techniques have a well established role in head and neck surgery. Successful anesthesia and analgesia for a number of procedures can be accomplished with the proper application of these techniques. For example, regional blocks can be utilized during procedures such as endoscopic sinus surgery, facial plastic surgery, thyroidectomy, and parathyroidectomy surgery. Various ear nose and throat procedures are increasingly being performed in an office-based setting. These are often done using topical anesthesia of the airway or regional blockade. Because of the close proximity of many nerve and vascular structures in this region, practitioners should be familiar with possible complications of these techniques and means to prevent and treat them. This chapter will review the anatomy relevant to regional blocks of the head and neck and will highlight examples for use of each technique in current practice. Additional discussion on numerous regional anesthesia techniques and their application can be also found in Chapter 19 (Airway Blocks) and in Chapters 20 (Oral and Maxillofacial Regional Anesthesia) and 55 (Regional and Local Anesthesia in Pediatric General Dentistry). To avoid redundancy, this chapter will deal only with the anatomic and block techniques not covered in the aforementioned chapters.

        TRIGEMINAL (GASSERIAN) GANGLION BLOCK

Indications

Gasserian ganglion block is used primarily for treatment of trigeminal neuralgia, a relatively rare but devastating form of neuropathic facial pain.^1–3 Patients with trigeminal neuralgia typically present with the spontaneous onset of pain in one or more divisions of the trigeminal nerve. The most common presentation involves both V₂ and V₃; however, any or all divisions may be involved. Patients report paroxysmal lancinating pain in the face that is often severe. The pain usually has a specific area of trigger—pressure on this trigger area elicits the pain.⁴ Patients who present with new symptoms suggestive of trigeminal neuralgia should undergo a thorough neurologic evaluation, including imaging studies to rule out intracranial pathology. The majority of patients with trigeminal neuralgia will respond to oral neuropathic medications; carbamezapine remains the agent of choice.^4,5 Neural blockade is usually reserved for those with trigeminal neuralgia that do not respond to pharmacologic therapy.^1,6 Local anesthetic block of the trigeminal ganglion and its primary divisions is often used as a diagnostic test to predict response to neural blockade prior to proceeding with neurolysis.^7–9

Clinical Pearls

Anatomy

The trigeminal nerve, the fifth cranial nerve, supplies the majority of sensory innervation to the· face (Figure 18-1). Preganglionic fibers exit the brainstem and travel anteriorly to synapse with second-order neurons within the trigeminal (gasserian) ganglion (Figure 18-2). The ganglion lies within the cranial vault at the base of the petrous portion of the temporal bone in a durai invagination containing cerebrospinal fluid known as Meckel’s cave. Postganglionic fibers exit the ganglion to form the ophthalmic (V₁), maxillary (V₂), and mandubular (V₃) nerves (Figure 18-3). The three divisions of the trigeminal nerve and the functions they serve are detailed in Table 18-1. The first division, the ophthalmic nerve, is discussed in detail in Chapter 21 (Eye Blocks).

Figure 18-1. Cutaneous innervation of the head and neck.

        The second division of the trigeminal nerve, the maxillary nerve, exits the middle cranial fossa via the foramen ro- tundum. Outside the cranial vault, the maxillary nerve sends pterygopalatine branches to the pterygopalatine ganglion, zygomatic nerve, and the infraorbital nerve. The pterygopalatine branch supplies the pterygopalatine ganglion which, in turn, supplies sensory branches to the nasal septum, the lateral nasal wall, and the soft and hard palates. The zygomatic nerve supplies sensory innervation surrounding the zygomatic arch (zygomaticotemporal and zygomaticofacial nerves). The infraorbital nerve sends sensory branches to the upper teeth (superior alveolar nerves) and terminates in a small sensory branch over the maxillary prominence (infraorbital nerve; see Figure 18-3).

        The third division of the trigeminal nerve, the mandibular nerve, exits the middle cranial fossa via the foramen ovale and divides into anterior and posterior divisions (Figure 18-4). The anterior division supplies motor innervation to the masseter muscle and other muscles involved in mastication and a small terminal sensory branch to the cheek (the buccal nerve). The posterior division divides into the auriculotemporal nerve (cutaneous sensation in front of the ear), the lingual nerve (sensation to the tongue), and the inferior alveolar nerve (sensation to the lower teeth). The inferior alveolar nerve terminates in a small cutaneous nerve supplying sensation to the chin (the mental nerve).

Figure 18-2. Trigeminal ganglion: organization and divisions.

Block Technique

Block of the gasserian ganglion is performed with the patient in the supine position.⁶ Location of the foramen ovale is facilitated by the use of fluoroscopic guidance. When fluoroscopy is used, the C-arm is angled so that the axis of the x-ray beam is aligned to reveal the foramen ovale (oblique and caudal angulation). A skin wheal of local anesthetic is raised 2-3 cm lateral to the corner of the mouth and a 22-gauge, 10-cm spinal needle is advanced upward toward the mandibular condyle in a plane in line with the pupil (Figure 18-5). The surface of the greater wing of the sphenoid bone is typically contacted at a depth of 4 to 6 cm, and the needle is withdrawn and redirected in a more posterior direction until the foramen ovale is entered. Once the needle enters the foramen, it is advanced an additional 1-1.5 cm. As the foramen is entered, a paresthesia in the mandible is usually elicited. As the advancement continues, paresthesia in the maxilla and orbit are also typically reported. Injection volume of 1.0 mL is usually sufficient to produce dense analgesia. Paresthesia in the effected division is sought to guide needle placement prior to neurolysis.

Figure 18-3.Cutaneous innervation of the face, anterior view.

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Ultrasound-Assisted Nerve Blocks in Adults. Cutaneous Blocks for the Upper Extremity. Cervical Plexus Block.