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