Head and Neck Blocks

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Chapter 5 Head and Neck Blocks

Chapter Overview

Chapter Synopsis: This chapter deals with various cephalic nerve and ganglia block procedures. Difficult pain conditions, including cluster headache, other trigeminal autonomic cephalalgias, and persistent idiopathic facial pain, can be treated with block or radiofrequency ablation (RFA) of the sphenopalatine ganglion (SPG). This extracranial structure represents a confluence of autonomic nerve fibers, both sympathetic and parasympathetic. The details of its anatomy and physiology are considered here, which have ramifications for the treatment of these disorders. Potential complications of the procedure stem mainly from disruption of autonomic fibers or the nearby maxillary nerve. Block and neurolytic procedures at the trigeminal nerve and Gasserian ganglion can be used to treat patients with intractable trigeminal neuralgia as well as some orofacial pain syndromes. Although radiofrequency thermocoagulation seems to produce the best outcomes among similar techniques, it also carries a significant risk of complications. Maxillary and mandibular nerve block procedures are used primarily as diagnostic tools, but atlanto-axial and atlanto-occipital joint injections can be used for diagnostic, therapeutic, or prognostic procedures.

Important Points:

Clinical Pearls:

Clinical Pitfalls:

Sphenopalatine Ganglion Block and Radiofrequency Ablation

Indications

Cluster headache involves activation of the parasympathetic outflow from the superior salivary nucleus of the facial nerve, predominantly through the sphenopalatine ganglion (SPG).1 The SPG is a large extracranial structure that has rich autonomic innervation (both sympathetic and parasympathetic), which explains the autonomic features associated with cluster headache. SPG block and radiofrequency ablation (RFA) are indicated in the management of intractable medically-resistant cluster headaches, migraines, and other trigeminal autonomic cephalalgias, and intractable orofacial pain syndromes after exhausting other conservative treatment options (e.g., persistent idiopathic facial pain, “atypical facial pain”).

Sphenopalatine Ganglion Neuroanatomy

The SPG has rich parasympathetic (preganglionic axons and postganglionic cell bodies and axons) and sympathetic (postganglionic axons) components. The parasympathetic preganglionic cell bodies projecting to the SPG originate in the superior salivatory nucleus (SSN) of the facial nerve in the pons.

The efferent fibers of the SSN travel in the nervus intermedius and divide at the geniculate ganglion to become the greater petrosal nerve and chorda tympani nerve. The first-order parasympathetic neurons in the greater petrosal nerve are joined by the postganglionic sympathetic fibers from the deep petrosal nerve, forming the nerve to the pterygoid canal (vidian nerve). The preganglionic parasympathetic neurons then synapse with the second-order parasympathetic neuronal cell bodies located in the SPG.

The postganglionic parasympathetic fibers then run with branches of the maxillary nerve (V2) to reach their targets. Therefore, the only cell bodies located within the SPG are those of the second-order postganglionic parasympathetic neurons, which may explain the clinical observation that patients after RFA of the SPG usually notice improvement of the autonomic parasympathetic symptoms either earlier or even without improvement of the headache pain.

The sympathetic cell bodies projecting to the SPG originate in the upper thoracic spinal cord (T1-T2). The preganglionic sympathetic neurons then synapse in the cervical sympathetic ganglia, mainly the superior cervical ganglion. The postganglionic second-order sympathetic neurons form the carotid sympathetic plexus and reach the pterygoid canal through the deep petrosal nerve, where it joins the first-order parasympathetic neurons in the greater petrosal nerve, forming the nerve to the pterygoid canal (vidian nerve). Postganglionic sympathetic fibers pass through the SPG without synapsing and innervate mainly blood vessels.

Approaches to the Sphenopalatine Ganglion

The unique location of the SPG within the PPF, just posterior to the middle turbinate, makes it accessible transnasally as well as with the infrazygomatic approach.

Transnasal Endoscopic Approach

This endoscopic technique for transnasal injection and blockade of the SPG was first described by Prasanna and Murthy in 1993.5 This technique allows a needle to be inserted transnasally under vision through the sphenopalatine foramen into the PPF.

Infrazygomatic Approach

Neuroablation techniques are only feasible with this infrazygomatic approach. Needle placement is usually guided by fluoroscopy; however, computed tomography guidance is reported as well.7

The infrazygomatic approach could be either anterior to the mandible or through the coronoid notch of the mandible.

Anterior Approach

The needle entry is inferior to the zygomatic arch, just anterior to the mandible, between the mandibular ramus and the posterior border of the zygomatic bone. The author prefers this approach because the needle can be advanced in a target view toward the PPF without the need to walk the needle off the lateral pterygoid plate (which is usually very painful) (Fig. 5-1). Also, it is much easier to steer the needle (cephalad–caudad or anterior–posterior) within the fossa to selectively target different structures within the fossa. However, this approach is not feasible in all patients because there might not be enough room between the mandible and the zygoma to insert the needle.

image

Fig. 5-1 Sphenopalatine ganglion block with the anterior approach.

(Reproduced with permission from the Ohio Pain and Headache Institute.)

Technique of Sphenopalatine Ganglion Block (Infrazygomatic Approach)

With the patient in the supine position and the head inside the C-arm, a lateral view is obtained and either the C-arm or the head of the patient is rotated until both pterygoid plates are superimposed on each other to better visualize the PPF. The skin entry site overlying the fossa is marked just inferior to the zygomatic arch either anterior to the mandible or through the coronoid notch. A 22-gauge, 3.5-inch blunt needle with a slight bend at the tip is used. The needle is first introduced in the lateral view and advanced medially and superiorly toward the PPF using real-time fluoroscopy. When in a proper direction, an anteroposterior (AP) view is obtained, and the tip of the needle is advanced to be just lateral to the nasal wall (Fig. 5-3). If the lateral pterygoid plate is encountered, the needle should be walked off the bone anteriorly and cephalad to slip into the fossa (the curved tip will help to guide the needle). A total of 0.1 to 0.2 mL of contrast agent is injected under real-time fluoroscopy to rule out intravascular spread because the PPF contains the maxillary artery and its branches (mainly the sphenopalatine artery). After negative aspiration of blood or air (the needle tip is too advanced into the nasal cavity or the maxillary sinus), 1 to 2 mL of 0.5% bupivacaine with or without steroids is injected slowly.

Radiofrequency Ablation Technique

With the patient in the supine position and the head inside the C-arm, a lateral view is obtained and either the C-arm or the head of the patient is rotated until both pterygoid plates are superimposed on each other to better visualize the PPF. The skin entry site overlying the fossa is marked just inferior to the zygomatic arch either anterior to the mandible or through the coronoid notch. A 22-gauge, 10-cm, blunt RFA needle with a 2- or 5-mm active tip with a slight bend at the tip is used (Fig. 5-4). The needle is first introduced in the lateral view and advanced medially and superiorly toward the PPF using real-time fluoroscopy. When in a proper direction, an AP view is obtained, and the tip of the needle is advanced to be just lateral to the nasal wall. If the lateral pterygoid plate is encountered, the needle should be walked off the bone anteriorly and cephalad to slip into the fossa (the curved tip will help to guide the needle). Sensory stimulation is obtained with 50 Hz to look for deep paresthesias behind the root of the nose at less than 0.5 V (Table 5-1). After proper stimulation is achieved and before lesioning, 0.1 to 0.2 mL of contrast agent is injected under real-time fluoroscopy to rule out intravascular spread. Then 0.5 mL of lidocaine 2% is injected, and two radiofrequency lesions are carried out at 80° C for 60 seconds each. After lesioning, 0.5 mL of bupivacaine 0.5% and 5 mg of triamcinolone is injected with the aim of preventing postprocedure neuritis.8

Efficacy of Sphenopalatine Ganglion Radiofrequency Ablation

In a retrospective analysis of patients with refractory cluster headache treated by RFA of the SPG, 56 patients with episodic cluster headache and 10 patients with chronic cluster headache were followed over a period of 12 to 70 months.5 In the episodic cluster headache group, 60.7% experienced complete pain relief, but only three of 10 patients with chronic cluster headache had the same result. This report showed that RFA of the PPG may improve episodic cluster headache but not chronic cluster headache. Recently, however, Narouze and colleagues8 reported a favorable outcome after intractable chronic cluster headache as well. They reported significant improvement in both mean attack intensity and mean attack frequency for up to 18 months in 15 patients. Of these patients, 20% (three of 15) reported no change or increase in the headache intensity or frequency during the first few postprocedure weeks before noticing improvements in their headache pattern. However, 46.7% (seven of 15) of the patients reported a change in the headache pattern with return to the episodic form of cluster headache at a mean follow-up period of 18 months. Three patients remained headache free and off medications for the duration of the follow-up (18 to 24 months).

Two patients reported complete relief of their usual unilateral headache symptoms, and instead they developed episodic cluster headache on the contralateral side.8

Complications of Radiofrequency Ablation

Epistaxis is more frequent after the traditional intranasal topical application of local anesthetic; however, it can occur with this infrazygomatic approach if the needle is advanced too far medially through the lateral nasal wall.9

Intravascular injection and hematoma formation can occur after maxillary artery injury, which lies within the PPF (Fig. 5-5). Cheek hematoma is the most common complication. Infection is always a possibility, especially if the oral or nasal mucosa was accidentally penetrated.9

image

Fig. 5-5 Sphenopalatine ganglion block with the anterior approach showing intravascular spread.

(Reproduced with permission from the Ohio Pain and Headache Institute.)

Reflex bradycardia was reported during radiofrequency lesioning, which could be explained by the rich parasympathetic connections to the SPG.10 Radiofrequency lesioning of the SPG may result in permanent or, more commonly, temporary hypesthesia or dysesthesia in the palate, maxilla, or posterior pharynx.2,3,8 Pulsed radiofrequency would seem to be safer; however, there are limited data for its efficacy.11

Dryness of the eye as a result of interruption of the parasympathetic supply is also common; however, it is usually only temporary. Temporary diplopia is more common after local anesthetic injections rather than RFA and can be explained by the spread of the injectate from the PPF to the inferior orbital fissure containing the abducent nerve.12 The author has noticed that most of the patients develop temporary diplopia if the needle tip is really inside the PPF, which is why the volume should be limited to only 1 to 2 mL (Fig. 5-6).

A thorough understanding of the anatomy allows the clinician to predict correct needle placement during RFA according to the result of the stimulation and hence can reduce the incidence of complications (Table 5-1).9

Trigeminal Nerve and Gasserian Ganglion Block and Neurolytic Procedures

Percutaneous Gasserian Ganglion Neurolytic Procedures

Gasserian Ganglion Anatomy

The Gasserian ganglion lies within Meckel’s cavity in the middle cranial fossa close to the petrous bone. It is surrounded medially by the cavernous sinus, superiorly by the inferior surface of the temporal lobe, and posteriorly by the brainstem.20 Gasserian ganglion has three divisions with a characteristic somatotopic arrangement, in that the ophthalmic division (V1) is the most craniomedial and the mandibular division (V3) is the most caudolateral. The maxillary branch (V2) lies in between. The ophthalmic nerve exits through the superior orbital fissure, the maxillary nerve through the foramen rotundum, and the mandibular nerve through the foramen ovale.

The Technique of Gasserian Ganglion Block

The procedure is usually performed with intravenous conscious sedation. The patient is in the supine position with the head inside the C-arm. After rotating the C-arm to obtain a submental view, the C-arm is slightly tilted to the affected side (oblique submental view) until the foramen ovale is best visualized (Fig. 5-8). It usually projects medially to the mandibular process. The point of the needle is about 2 cm lateral to the corner of the mouth on the ipsilateral side. A 3.5-inch, 22- to 25-gauge blunt nerve-stimulating needle is then advanced toward the foramen ovale under real-time fluoroscopy first in the AP submental view and then in the lateral view.

image

Fig. 5-8 Oblique submental view showing the needle tip inside the foramen ovale.

(Reproduced with permission from the Ohio Pain and Headache Institute.)

It is important to place a finger in the mouth to prevent or detect oral mucosa penetration. After the needle is inside the foramen ovale, motor stimulation is started, and muscle twitches should be observed in the mastication muscles (V3). There is no need to advance the needle farther inside the foramen ovale unless cerebrospinal fluid (CSF) will be aspirated from the needle. A total of 0.5 to 1 mL of contrast should be injected under real time fluoroscopy with digital subtraction, if available, to rule out intravascular spread (Fig. 5-9). After negative aspiration for CFS and blood, 1 to 2 mL of bupivacaine 0.5% with or without steroids can be injected slowly with close observation of the patient’s hemodynamics and vital signs.

image

Fig. 5-9 Gasserian ganglion block. Lateral view showing intravascular spread (arrows).

(Reproduced with permission from the Ohio Pain and Headache Institute.)

The Technique of Gasserian Ganglion Radiofrequency Thermocoagulation

The procedure is usually performed under monitored anesthesia care with propofol or dexmedetomidine. The patient is in the supine position with the head inside the C-arm. After the C-arm is rotated so a submental view can be obtained, the C-arm is slightly tilted to the affected side (oblique submental view) until the foramen ovale is best visualized (Fig. 5-8). It usually projects medially to the mandibular process. The point of the needle is about 2 cm lateral to the corner of the mouth on the ipsilateral side. A 100-mm 22-gauge radiofrequency needle with a 2-mm active tip is then advanced toward the foramen under real-time fluoroscopy first in the AP submental view and then in the lateral view.

It is important to place a finger in the mouth to prevent or detect oral mucosa penetration. After the needle is inside the foramen ovale, testing stimulation is started. When motor stimulation (masseter muscle, V3) is encountered, the needle needs to be slightly advanced into the foramen carefully about 2 mm to stimulate V2. V1 is even deeper. In the lateral view, the needle tip should be deep into the foramen, overlying the petrous bone (Fig. 5-10). Some practitioners advocate that the patient should be covered with a broad-spectrum antibiotic if CSF is aspirated from the needle. The patient is then allowed to wake up, and sensory stimulation can be carried out with 50 Hz. Paresthesia should be felt between 0.05 and 0.1 V in the painful areas. V3 stimulation is encountered superficial and lateral in the foramen, then V2, and V1 is the deepest toward the pons and more medially. After appropriate paresthesia is obtained at the desired sites, a 60° C thermo lesion is carried out for 60 seconds. The corneal reflex and the treated dermatome may be tested for hypoesthesia. If intact, a second lesion is made at 65° C for 60 seconds, and if there is still no hypoesthesia, then a third lesion can be made at 70° C for another 60 seconds.

Efficacy of Radiofrequency Thermocoagulation of the Gasserian Ganglion

The first application of radiofrequency in pain medicine was for the treatment of trigeminal neuralgia with reported excellent results. Kanpolat et al21 evaluated the effectiveness of percutaneous radiofrequency trigeminal rhizotomy in 1600 patients with idiopathic trigeminal neuralgia with a follow-up period of 1 to 25 years. Acute pain relief was accomplished in 97.6% of patients. Pain relief was reported in 92% of patients with a single procedure or with multiple procedures 5 years later. At 10-year follow-up, 52.3% of the patients who underwent a single procedure and 94.2% of the patients who underwent multiple procedures had experienced pain relief. At 20-year follow-up, 41% and 100% of these patients, respectively, had experienced pain relief. After the first procedure was performed, early pain recurrence (<6 mo) was observed in 123 patients (7.7%), and late pain recurrence was observed in 278 patients (17.4%). The authors concluded that percutaneous radiofrequency trigeminal rhizotomy is a minimally invasive, low-risk technique with a high rate of efficacy and the procedure may safely be repeated if pain recurs.

Wu et al22 also reported their results in 1860 patients with refractory trigeminal neuralgia. The outcome was excellent in 78.8%, good in 17.5%, and poor in 3.7% of cases. Pain recurrence was reported in 11.1% of cases during the first 12 months and 24.8% after 24 months.

Complications of Gasserian Ganglion Block and Neurolysis

The Gasserian (trigeminal) ganglion lies within Meckel’s cave, which is formed by a dura mater fold that surrounds the posterior two-thirds of the ganglion. Meckel’s cave contains CSF, so local anesthetic deposited in this area may spread to other cranial nerves and can potentially cause brainstem anesthesia.20 Meticulous attention should be paid to avoid intravascular injection.17 Negative aspiration is unreliable, and injection of the contrast agent should be performed under real-time fluoroscopy with digital subtraction, if available, before injection of the local anesthetic.

In a systematic review of ablative neurosurgical techniques for the treatment of trigeminal neuralgia, Lopez et al16 concluded that although radiofrequency thermocoagulation (RFT) seems to provide the highest rates of sustained complete pain relief, it is the technique that is associated with the greatest number of complications.

A total of 29.2% of the patients in the analyzed series developed some complications, mostly transient, with RFT, and the rate of complications from glycerol rhizolysis was 24.8%. Stereotactic radiosurgery was the safest technique; only 12.1% of the patients experienced complications, mostly dysesthesias (Table 5-2).

Table 5-2 Complications of Percutaneous Gasserian Ganglion Neuroablative Procedures

  Radiofrequency Thermocoagulation Glycerol Rhizolysis
Complications rate (%) 29.2 24.8
Masticatory weakness (%) 11.9 3.1
Dysesthesia (severe) (%) 3.7 8.7
Anesthesia dolorosa 1.6 2.3
Corneal numbness 9.6 8.1
Keratitis 1.3 2.1
Cranial nerve deficits 0.9 0.2
Meningitis 0.2 0.7

Modified from Lopez BC, Hamlyn PJ, Zakrzewska JM: Systematic review of ablative neurosurgical techniques for the treatment of trigeminal neuralgia, Neurosurgery 54:973-982; discussion 982-983, 2004.

Postoperative trigeminal sensory loss affects virtually all patients treated with RFT, and it is considered a side effect rather than a complication. However, in a prospective study, 30% of these patients may experience permanent sensory loss.23

Maxillary Nerve Block and Mandibular Nerve Block

Blockade of the maxillary and mandibular nerves or their branches is usually performed as a diagnostic block when more selective nerve block is needed for the diagnosis of various orofacial pain syndromes.

Mandibular Nerve Block

The mandibular nerve exits through the foramen ovale. The mandibular division (V3) is the most caudad and lateral part of the Gasserian ganglion.

Technique of Mandibular Nerve Block

There are two approaches for blockade of the mandibular nerve.

Atlanto-Axial and Atlanto-Occipital Joint Injections

Atlanto-Axial Joint Injection

The lateral atlanto-axial joint (AAJ) may account for up to 16% of patients with occipital headache.24 Clinical presentations suggestive of pain originating from the lateral AAJ include occipital or suboccipital pain, focal tenderness over the suboccipital area, restricted painful rotation of C1 on C2, and pain provocation by passive rotation of C1. These clinical presentations are not specific and therefore cannot be used alone to establish the diagnosis.25 The only means of establishing a likely diagnosis is a diagnostic block with intraarticular injection of local anesthetic.24

Anatomy of the Atlanto-Axial and Atlanto-Occipital Joints

AAJ and atlanto-occipital joint (AOJ) intraarticular injections have the potential for serious complications, so it is crucial to be familiar with the anatomy of the joint in relation to the surrounding vascular and neural structures (Fig. 5-15). The vertebral artery is lateral to the AAJ as it courses through the C2 and C1 foramina. Then it curves medially to go through the foramen magnum, crossing the medial posterior aspect of the AOJ. The C2 dorsal root ganglion and nerve root with its surrounding dural sleeve crosses the posterior aspect of the middle of the joint. Therefore, during AAJ injection, the needle should be directed toward the posterolateral aspect of the joint. This will avoid injury to the C2 nerve root medially and the vertebral artery laterally (Fig. 5-15).24,27 On the other hand, the AOJ should be accessed from the most superior posterior lateral aspect to avoid the vertebral artery medially.

Technique of Atlanto-Axial Joint Injections

Every effort should be made to make the injection a true intraarticular and not periarticular injection. Those procedures are mainly used in the diagnosis of pain stemming from the joints, and periarticular injection is not target specific because the local anesthetic may contaminate the C2 nerve root, which crosses the posterior aspect of the AAJ. Intraarticular injection is more target specific because it selectively anesthetizes the joint.

The patient is placed in the prone position with a pillow under the chest to allow for slight neck flexion. The fluoroscopy C-arm is brought to the head of the table in an AP direction. Under fluoroscopic guidance, the C-arm is rotated in the sagittal plane until the lateral atlanto-axial joint is better visualized. Using a marking pen, the needle insertion site is marked on the skin overlying the lateral third of the atlanto-axial joint. The skin is prepped and draped in the usual sterile fashion and a skin wheel is raised with local anesthetic at the insertion site. Then a 22- to 25-gauge, 3.5-inch blunt needle is advanced in anterior and medial direction toward the posterolateral aspect of the inferior margin of the inferior articular process of the atlas. This will avoid contact with the C2 nerve root and dorsal ganglion, which crosses the posterior aspect of the middle of the joint (Fig. 5-15). After touching the bone to safely establish the correct depth, the needle is withdrawn slightly; directed toward the posterolateral aspect of the lateral atlanto-axial joint; and advanced for couple of millimeters and usually a distinctive pop is felt, signaling entering the joint cavity. At this point, a lateral view is obtained, which shows the tip of the needle in the middle of the joint anterior to the posterior margin of the joint. Careful attention should be paid to avoid the vertebral artery that lies lateral to the lateral atlanto-axial joint as it courses through the C1 and C2 foramina. After careful negative aspiration for blood or cerebrospinal fluid, 0.2 mL of water-soluble nonionic contrast agent (Omnipaque 240) is injected to verify intraarticular placement of the tip of the needle.

Injection of the contrast agent is done under direct real-time fluoroscopy to check for inadvertent intraarterial injection, which is manifest by rapid clearance of the contrast agent. AP and lateral views are obtained to ensure that the contrast agent remained confined to the joint cavity without escape to the surrounding structures, especially the epidural space or posteriorly to the C2 ganglion, which will adversely affects the specificity of the block (Figs. 5-16 and 5-17). The AP view usually demonstrates the bilateral concavity of the joint with the contrast material inside the joint space (Fig. 5-16), and sometimes it shows that the lateral AAJ space may communicate with that of the median AAJ space (Fig. 5-18) and the contralateral AAJ space (Fig. 5-19). After careful negative aspiration, 1.0 mL of a mixture of bupivacaine 0.5% and 10 mg of triamcinolone is injected.27

Technique of Atlanto-Occipital Joint Injections

This procedure is rarely performed for few reasons. Isolated pain stemming from the AOJ is very rare, and the patient usually has localized occipital pain that is aggravated mainly by head nodding. Therefore, activity modification and conservative management are usually all that is needed. Also, the vertebral artery curves from lateral to medial, crossing the posterior aspect of the C1 body, which makes it vulnerable to injury while the needle is advanced toward the AOJ, especially with improper positioning of the patient.

The positioning and approach are similar to those for AAJ injection. The patient needs to flex his or her head over the neck as much as possible (chin on chest) to open the suboccipital space posteriorly. The AOJ should be accessed from the most superior posterior lateral aspect to avoid the vertebral artery (Figs. 5-20 and 5-21).

image

Fig. 5-20 Atlanto-occipital joint injection, anteroposterior view.

(Reproduced with permission from the Ohio Pain and Headache Institute.)

image

Fig. 5-21 Atlanto-occipital joint injection, lateral view.

(Reproduced with permission from the Ohio Pain and Headache Institute.)

More recently, ultrasound-assisted AOJ injection in conjunction with fluoroscopy was described. With real-time sonography, the vertebral artery is identified as it curves medially behind the C1 body and accordingly can be avoided from the needle path, and then the procedure can be continued with fluoroscopy to confirm intraarticular placement of the needle (Fig. 5-22).30

Efficacy of Atlanto-Axial and Atlanto-Occipital Joint Injections

Narouze and colleagues27 studied 115 patients with cervicogenic headache. Thirty-two patients had a clinical picture suggestive of AAJ pain, and the diagnosis was confirmed in 15 patients with complete abolition of the headache (pain score of 0) after AAJ injection. The prevalence of AAJ pain among patients with cervicogenic headache was 13% (15 of 115 patients). At 1, 3, and 6 months after AAJ intraarticular steroid injection, the mean pain scores dropped from a baseline of 6.8 to 1.9, 3.6, and 3.7 respectively. The authors concluded that intraarticular steroid injection is effective for short-term relief of pain originating from the lateral AAJ.

No data are available to demonstrate the efficacy of AOJ intraarticular steroid injections.

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