Suprazygomatic Maxillary Nerve Block
Indications: Cleft lip & palate repair, Maxillary osteotomies for orthognathic surgery, Functional Endoscopic Sinus Surgery, Palatine Tonsillectomy (this is developing indication)
Complications:
Bleeding – either superficial bruising or more rarely deep infratemporal hematoma (secondary to injury to the maxillary artery or pterygoid venous plexus)
Consider the maxillary nerve block as a deep peripheral block and follow the corresponding ASRA guidelines on patients receiving antithrombotic or thrombolytic therapy
Infection
Cranial nerve palsies
The proximity of the infraorbital fissure to the pterygopalatine fossa (PPF) enables possible orbital spread (untoward peribulbar/retrobulbar block?)
Literature limited to case reports, but likely underreported
Anecdotally, abducens nerve and cranial nerve III palsies have been reported, all of which resolved after resolution of intended nerve blockade
Nasal drip
Nasal drip has also been seen a handful of times immediately after injection. Likely etiology is local anesthetic passing down a pressure gradient from the PPF through the sphenopalatine foramen during injection. It presents as a scant, immediate unilateral rhinorrhea.
Dosing
The optimal volume, type, and concentration of local anesthetic is unclear.
However, 0.15 ml/kg/side (to a maximum of 5 ml per side) of local anesthetic (ropivacaine 0.2-0.5% or bupivacaine 0.25%) is frequently cited in the literature
Adjuvants: Commonly, alpha2-agonists are added to prolong or “enhance” the block. A typical dose is 0.5 mcg/kg/side blocked of dexmedetomidine.
Expected Coverage
A field block of the maxillary nerve at the pterygopalatine fossa (PPF) in theory will also anesthetize its distal branches, including:
Infraorbital (terminal branch) nerve
Zygomaticofacial and Zygomaticotemporal nerves
Greater and Lesser Palatine nerves
Pharyngeal nerve
Superior alveolar nerves
Medial superior posterior nasal branches
Nasopalatine nerve
Expected Sensory Coverage
Technique
Landmark-based Approach
Locate the frontozygomatic angle (formed by the intersection of the posterior orbital rim and the superior edge of the zygomatic arch). This will be your site of needle insertion (Figure 1).
Advance the block needle perpendicular to the skin (Figure 2a) surface towards the PPF, with a trajectory towards a point anterior to the tragus of the contralateral ear (Figure 2b). You may feel some slight resistance from the tough temporalis muscle fascia as you advance.
Fig. 1
Fig. 2a
Fig. 2b
Fig. 3
Fig. 4
Your first bony contact will likely be the greater wing of the sphenoid bone. If so, walk off the lateral “rim” of the sphenoid caudally and dive into the infratemporal fossa. Optimal needle insertion and favorable anatomy may allow needle insertion directly into the PPF without any early bony contact along the way (Figure 3).
Continue advancing towards the PPF via the pterygomaxillary fissure (the narrow groove formed by the maxilla anteriorly and the lateral pterygoid plate posteriorly). The distance from the skin to PPF is approximately 4-5cm, depending on age. Avoid bony contact at the PPF in awake patients, as this can be uncomfortable. (Figure 4)
Ultrasound-Guided Approach
Use landmark-based approach as described above + ultrasonography to visualize local anesthetic spread (precise needle visualization may not be possible)
Place a small-footprint linear probe parallel to and under the zygomatic arch, then angle the probe towards the PPF at approximately 45° to the sagittal plane (Figure 5)
Note the acoustic shadowing from the maxilla and sphenoid, and the pterygopalatine fossa/pterygomaxillary fissure between (Figure 6)
Align your image such that bony shadows are on the image edges and the pterygopalatine fossa/pterygopalatine fissure is in the center. Between the bone shadows you may visualize the lateral pterygoid plate as a small hyperechoic line around 4 centimeters in depth.
Often you can visualize pulsations from the maxillary artery or its branches in the infratemporal fossa/pterygomaxillary fissure
Aspirate for heme and inject in divided doses As you inject, observe the “bloom” of tissue displacement from your injectate.
Fig. 5
Fig. 6
The maxillary nerve block is a versatile regional anesthetic technique. Familiar to anesthesiologists who provide care on mission trips for cleft palate repair, the technique has gained traction as a useful technique for a variety of surgical procedures performed in other practice settings.
In theory, a truncal block of the maxillary nerve at the pterygopalatine fossa (PPF) may provide anesthesia and analgesia for the majority of the midface. It is at the level of the PPF where many important branches of the maxillary nerve supply sensory afferent input from various structures of the midface. Note that the sphenopalatine ganglion (SPG) is in close proximity within the PPF; thus, any local anesthetic injected within/around the PPF may additionally block the SPG and the autonomic fibers that synapse within.
Both suprazygomatic and infrazygomatic approaches have been described; however, the suprazygomatic route appears safer without significantly diminishing feasibility. The vast majority of pediatric literature concerns the suprazygomatic route.
Blockade of the maxillary nerve is an old concept; the first descriptions were in the 1920s dental/oral surgery literature, where blockade of the maxillary nerve was performed by injection of local anesthetics via the greater palatine foramen and canal. Extra-oral alternatives to this approach surfaced in the 1970s and 80s, the majority of which were infrazygomatic, with or without fluoroscopic image guidance. These infrazygomatic approaches were not without their potential complications, including injection or injury to the maxillary artery, and needle penetration into the orbit (inferior orbital fissure) or skull base (via the foramen rotundum). The difficulty in identifying the requisite intraoral anatomical landmarks, and the need for a safer extraoral technique prompted clinical investigations of a suprazygomatic approach to the maxillary nerve (SZAMN) block for infants and children.
Captier et al first characterized the needling distances and angular redirections (approximately 20° anterior, 9° inferiorly) required to enter the pterygopalatine fossa (PPF) via the suprazygomatic, extraoral route in infants using available CT scan data. The needling technique was further refined by infant cadaver studies by Prigge et al, where they described the frontozygomatic angle as the optimal needle insertion site and that “…the needle should be advanced in a posterior direction, toward a point just anterior to the tragus of the contralateral external ear (this should be approximately between 8° and 15°) to reach the pterygopalatine fossa”. The application of ultrasound guidance introduced by Sola et al described the sonoanatomy of the infratemporal fossa, and the patterns of injection during SZAMN blockade. However, it is still unclear if ultrasound use (real-time guidance or assistance) predicts efficacy, improves safety, or both. A brief review on the use of ultrasonography for both infra- and suprazygomatic approaches to the maxillary nerve block can be found in an article by Anugerah et al.
Cleft Palate repair
Mesnil et al first published a non-randomized prospective study describing their experience with the SZAMN block for cleft palate repair; patients receiving the block demonstrated less intraoperative and postoperative opioid consumption and modestly improved time to feeding. What followed over the next few years were several studies assessing the effectiveness of SZAMN blockade for cleft palate repair analgesia, as well as other outcome measures such as pain scores, oral feeding readiness, and hospital length of stay. Although most studies demonstrating positive results in one or more outcome measures, many were inconsistent between studies. One of these was the landmark paper by Chiono et al – a randomized, double-blinded placebo-controlled (saline vs. ropivacaine) trial in children demonstrating a nearly 50% reduction in post-operative opioid consumption with SZAMN blockade, although post-operative pain scores were similar between groups. A few follow-up studies in the 2010s explored the usage of alpha2-agonists as adjuvants to enhance blockade, with dexmedetomidine being the most studied. The latest PROSPECT recommendations for cleft palate surgery pain management includes SZAMN blockade with the inclusion of perineural or IV dexmedetomidine as adjuvants.
Other/emerging indications The use of SZAMN blocks for orthognathic surgery has also been studied, although not to the extent as for cleft palate repair. Nores et al published a prospective, non-randomized study of SZAMN blockade for Le Fort I osteotomies demonstrating significant reductions in opioid requirements on postoperative days (POD) 1 and 2, as well as almost a full day reduction in length of stay. Pain scores were also statistically reduced with SZAMN block on POD1, but clinical significance is questionable. Another retrospective cohort study showed similar results for SZAMN blocked patients. Higher quality studies are still required to examine the roll of maxillary nerve blockade for orthognathic surgery.
Maxillary nerve blockade for postoperative analgesia after palatine tonsillectomy is an emerging indication. First described in a case series by Smith et al on adult patients, a few case studies followed in pediatrics showing promise for early analgesia, one of which by Zoghbi et al demonstrated good pain control through POD3, with rebound pain on POD4. Again, high quality studies are lacking.
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