Chapter 18. Nerve Blocks for the Head & Neck

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.

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

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 dural 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).

The second division of the trigeminal nerve, the maxillary nerve, exits the middle cranial fossa via the foramen rotundum. 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).

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.

Complications

Complications associated with local anesthetic block of the trigeminal ganglion include direct intravascular injection into the carotid artery, persistent paresthesia, and total spinal anesthesia due to local anesthetic deposition within the cerebrospinal fluid over the ventral surface of the brainstem. Complications associated with neurolysis are more common. Facial numbness occurs in nearly all patients and may be profound. Other complications include anesthesia dolorosa (pain and numbness), reduced corneal reflex, abolition of the corneal reflex, keratitis, and masticatory weakness. Percutaneous trigeminal neurolysis (using either glycerol or radiofrequency lesioning) remains an effective, minimally invasive treatment for patients with trigeminal neuralgia.

Indications

Greater palatine block is useful for paranasal sinus anesthesia and vasoconstriction during endoscopic sinus surgery.

Technique

Via the oral cavity the greater palatine groove is finger palpated, and the needle is inserted into the groove and advanced to contact the bone at which point 2–3 mL of local anesthetic is injected (Figures 18–6 and 18–7).6,10,11

Indications

Occipital nerve block is most often used in the diagnosis and treatment of occipital neuralgia and cervicogenic headache. True occipital neuralgia typically follows blunt trauma to the nerves over the occiput and is characterized by pain in the distribution of the occipital nerves. Cervicogenic headache is more ill-defined, insidious in onset, and characterized by pain in the same distribution. Many patients with cervicogenic headaches have associated spondylosis of the cervical facet joints. When the pain is limited to the region overlying the occiput, occipital nerve blocks may be of some benefit in reducing the associated pain.

Anatomy

The greater occipital nerve arises from the posterior primary ramus of the second cervical nerve root (Figure 18–8). It travels deep to the cervical paraspinous musculature and becomes superficial just inferior to the superior nuchal line and lateral to the occipital protuberance of the skull; at this point, the nerve is just lateral to the occipital artery. The lesser occipital nerve and great auricular nerve are terminal branches of the superficial cervical plexus. Both arise from the posterior primary ramus of the second and third cervical nerve roots, travel through the cervical paraspinous musculature, and become superficial over the inferior nuchal line of the skull, just superior and medial to the mastoid and just inferior to the tragus of the ear, respectively. The lateral section of the posterior scalp is supplied by the lesser occipital and great auricular nerves.

Technique

Occipital nerve block is typically performed with the patient in the sitting position with the head and neck held in the flexed position.6,10,11 The occipital protuberance and mastoid process are identified, and an imaginary line connecting these two landmarks is made. The occipital artery is often palpable about a third of the distance from midline to the mastoid process and is the site of greater occipital nerve block. The lesser occipital nerve is blocked at a distance two thirds of the way from the midline to the mastoid process along this imaginary line. The block can be carried out by using a single skin entry point midway between the mastoid process and the occipital protuberance. Three to 5 mL of local anesthetic is infiltrated medially and another 3–5 mL laterally, both along this line. An effective block can be achieved by using two separate skin entry sites one third and two thirds of the way along this line. The local anesthetic is deposited within the skin and subcutaneous tissues in a fanwise fashion to create a subcutaneous wall along the imaginary line. A 25- or 27-gague 1½-in. needle is used.

Complications

Few complications are associated with occipital nerve blocks. The local anesthetic itself creates swelling of the scalp, and the patient should be warned that this is normal. Puncture of the occipital artery is not uncommon and can result in hematoma. Simple pressure by the patient may be applied. Patients with a history of blunt trauma to the area or prior posterior fossa intracranial surgery may have a defect in the bony cranium; in such cases, direct entry into the cranial vault may produce total spinal anesthesia.

Anesthesia of the nasal septum and the lateral wall of the nasal cavity facilitates nasotracheal intubation. Sensation to the superior portions of both the septum and lateral wall of the nasal cavity are supplied by the anterior ethmoidal nerve, a terminal branch of the ophthalmic division of the trigeminal nerve (Figure 18–9). The inferior and posterior portions of the septum and the lateral wall of the nasal cavity are innervated by branches arising from the sphenopalatine ganglion. These terminal branches lie superficially just beneath the nasal mucosa and can be anesthetized by direct topical application of local anesthetic (Figure 18–10).12

The supraorbital nerve emerges from the supraorbital foramen, which can be palpated along the upper border of the orbit, approximately 2.5 cm lateral to the midline of the face.13 The supraorbital nerve exits along the upper border of the orbit, approximately 1 cm medial to the supraorbital foramen.

Indications

A supraorbital block is primarily used for the surgery on lower forehead and upper eyelid.

Technique

The supraorbital notch is palpated by the finger (Figure 18–11) and the needle is inserted along the upper orbital margin, approximately 1 cm medial to the supraorbital foramen where 2–3 ml of local anesthetic is injected (Figure 18–12).

An infraorbital block anesthetizes the anterior and middle maxillary alveolar nerves, inferior palpebral, lateral nasal, and superior labial nerves, resulting in anesthesia of the maxillary incisors, canines and premolars, including their vestibular osseous support and the soft tissues which cover them (Figure 18–13). In addition, mesiovestibular root of the maxillary first molar, part of the maxillary sinus, nose, superior labial, and inferior palpebral areas are also partly or completely anesthetized.

Anatomy

The second division of the trigeminal nerve, maxillary branch, exits the skull through the foramen rotundum, passes the pterygomaxillar fossa, enters the infraorbital canal, becomes the infraorbital nerve, and runs along the orbital floor (Figure 18–14). In other words, the infraorbital nerve is an extension of the maxillary nerve as it reaches the infraorbital fossa. The nerve emerges at the anterior side of the maxilla through the infraorbital foramen, ending in three terminal branches: lateral nasal, superior labial, and inferior palpebral (see Figure 18–13). About 5 to 6 mm before the foramen, the infraorbital nerve supplies the anterior maxillary alveolar nerve, whose branches descend by narrow canals in the maxilla, running between the sinus mucosa and the bony wall, penetrating through the radicular apices, to innervate the pulp of maxillary incisors and canines. Its branches also go to the outer bone plate, periosteum, and other lining structures in the region of these teeth.

The middle superior alveolar nerve leaves the infraorbital nerve at the posterior part of the floor of the infraorbital canal and continues in a downward frontal direction until the premolar apices. At other times, it separates near the infraorbital foramen and descends by the anterior wall or the anterolateral maxillary sinus until the superior premolars, innervating the dental pulp, the external alveolar lamina, the periosteum and the mucosa.

Technique

The infraorbital foramen is located with a finger beneath the middle of the inferior margin of the orbit, just above the centered pupil.14,15 The needle is inserted into the superior buccal groove and directed upward and outward, until contact with the finger, ie, injection site. A hypodermic needle (typically 25–27 gauge, 25 mm) is used. Lidocaine (1% or 2%), 0.25% bupivacaine, or 0.5% ropivacaine are all commonly used. In infants, 0.5–1 mL is used, 1–2 mL in children and 5 mL in adults.

For surgery on the upper lip, a bilateral infraorbital nerve block is always needed. For labiomaxillary fissure repair, this block should be combined with a nasopalatine nerve block.

Another technique of blocking the infraorbital nerve is by inserting the needle into the nasal vestibule and directing it lateral and superior in the direction of the infraorbital nerve. This is particularly useful for nasal work, such as nasal fractures.

Several nerve block technique for head and neck applications can be used to provide successful anesthesia and analgesia for a variety of procedures performed on the head and neck. The same techniques are also used in the pain management practice either as diagnostic or therapeutic procedures. We suggest the reader consult Chapters 19, 20, and 21 and 55 for more information on nerve block techniques for the head and neck surgery.