Article Text
Abstract
Background and objectives Blockade of the trigeminal nerve and its branches is an effective diagnostic tool and potential treatment of facial pain. Ultrasound-guided injections in the pterygopalatine fossa (PPF) to block the trigeminal nerve divisions and sphenopalatine ganglion have been described but a consensus has yet to be reached over the ideal approach. We sought to delineate and compare the various approaches to the ultrasound-guided trigeminal divisions blockade via the PPF.
Methods The literature search was performed by searching the National Library of Medicine’s PubMed database, the Cochrane Database of Systematic Reviews and Google Scholar within the date range of January 2009–March 2019 for keywords targeted toward “trigeminal nerve,” “maxillary nerve,” or “pterygopalatine fossa,” “ultrasound,” and “nerve block,” using an English language restriction. Six papers were included in the final review: one prospective double-blinded randomized controlled trial, one prospective descriptive study, one case series, two case reports, and one cadaveric study.
Results There are three main approaches to the ultrasound-guided trigeminal nerve branches blockade via the PPF: anterior infrazygomatic in-plane, posterior infrazygomatic in-plane, and suprazygomatic out-of-plane approaches. Each showed injectate spread to the PPF in cadaver, adult and pediatric patients, respectively.1–5 Injectate used varied from 3 to 5 mL to 0.15 mL/kg.
Conclusions These studies demonstrated that the PPF is a readily accessible target for the ultrasound-guided maxillary nerve block via three main approaches.2 The ideal approach is yet to be determined and must be further explored.
- chronic pain: head and neck
- chronic pain: imaging
- chronic pain: diagnostic pain procedures
- interventional pain management
- ultrasound in pain medicine
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- chronic pain: head and neck
- chronic pain: imaging
- chronic pain: diagnostic pain procedures
- interventional pain management
- ultrasound in pain medicine
Introduction
Blockade of the maxillary (V2) branch of the trigeminal nerve is an effective diagnostic tool and potential treatment of facial pain.1 2 Initially, the maxillary nerve block was described using a landmark technique by contacting the lateral pterygoid plate, entering the pterygopalatine fossa (PPF), and advancing the needle into the fossa to elicit a paresthesia in the V2 distribution. The standard approach is performed using fluoroscopic guidance or CT by targeting the PPF, redirecting off bone as needed, and observing for the absence of intravascular contrast spread prior to injecting local anesthetic with or without steroid.2 The limitations of fluoroscopy include reliance on bony landmarks which are difficult to visualize, radiation exposure, and inability to visualize vasculature during needle placement.3 Although there is currently a lack of clinical outcome data with ultrasound-guided approaches, ultrasound has emerged as a highly accurate imaging tool for the trigeminal nerve block. Ultrasound-guided procedures have a more favorable safety profile and no radiation exposure compared with fluoroscopy providing real-time visualization of soft tissues, vasculature, and bony structures, optimal needle visualization, and direct observation of injectate spread (table 1).1 3 6
Ultrasound-guided injections in the PPF to block the maxillary nerve and sphenopalatine ganglion have been described but a consensus has yet to be reached over the ideal approach.1 3–13 We sought to delineate and compare the various approaches to the trigeminal nerve block via the PPF.
Methods
Patient informed consent was obtained for the ultrasound image. Publications describing ultrasound-guided maxillary nerve blocks were searched for using the National Library of Medicine’s PubMed database, the Cochrane Database of Systematic Reviews, and Google Scholar within the date range of January 2009–March 2019. Free text and Medical Subject Headings terms “trigeminal nerve,” “maxillary nerve,” “pterygopalatine fossa,” “ultrasound,” and “nerve block” were used individually and in various combinations. An English language restriction was used. Six publications were included in the final review: one prospective double-blinded randomized controlled trial, one prospective descriptive study, one case series, two case reports, and one cadaveric study (Appendix A).
Supplemental material
Results
The three main approaches to the ultrasound-guided maxillary nerve block via the pterygopalatine fossa are detailed in tables 2 and 3, and illustrated in figures 1 and 2.1 3–13
A summary of the literature supporting the main approaches to the ultrasound-guided maxillary nerve block is described in table 4.1 3 4 6 7 10 Volume of injectate varied among cases from 3 to 5 mL. Two studies in pediatrics reported using weight-based dosing of 0.15 mL/kg.4 7 Local anesthetic used included both bupivacaine and ropivacaine with Nader et al also using dexamethasone.1 3 4 6 7 10
A posterior to anterior infrazygomatic in-plane approach was described in a case series of 15 patients with facial pain by Nader et al in 2013.3 5 The ultrasound probe was placed below the zygomatic process, just anterior to the mandibular condyle (figure 3). The needle was directed in a posterior-to-anterior and lateral-to-medial direction with the needle tip advanced, in plane to the probe, through the lateral pterygoid muscle stopping just above the lateral pterygoid plate at the pterygopalatine fissure at 4–5 cm depth (figure 1B). At this location, 4 mL of 0.25% bupivacaine and 4 mg of dexamethasone were injected. Using this technique, a patient with unsustained pain relief from ultrasound-guided trigeminal nerve block via the PPF was successfully treated with ultrasound-guided pulsed radiofrequency treatment in the PPF, reporting immediate pain relief lasting over 6 months.1
An anterior to posterior infrazygomatic in-plane approach was described in a cadaveric study by Kampitak et al in 2018. The ultrasound probe was placed below the zygomatic process, at the uppermost part of the lateral pterygoid plate. The needle was advanced in an anterior-to posterior and lateral-to-medial direction through the lateral pterygoid muscle until the top of the lateral pterygoid plate was contacted. The needle was then withdrawn and redirected medially and advanced 1–2 mm into the PPF. 3 mL of methylene blue dye was injected. Dye was found to have spread into the PPF and its structures, including maxillary nerve branch, pterygopalatine ganglion, greater and lesser palatine nerves and middle and posterior superior alveolar nerves, with additional spread into the infraorbital foramen.6 The zygomatic and buccal branches of the facial nerve within the parotid gland were superior and inferior to needle trajectory and the maxillary artery was below the needle pathway.6
A suprazygomatic out-of-plane approach has been described by Sola et al in infants and children undergoing cleft palate repair.4 7 The ultrasound probe was placed below the zygomatic process over the maxilla at a 45° angle of inclination at the frontal and horizontal planes. The needle was inserted perpendicular to the skin, in an out-of-plane approach, at the frontozygomatic angle in the area above the zygomatic process. The needle was advanced until the greater wing of the sphenoid was contacted at 20 mm depth. The needle was then withdrawn and reoriented caudal and posteriorly 35–45 mm deep into the PPF. 0.15 mL/kg of 0.2% ropivacaine was injected. The authors found that 70% of injectate spread to the intermediate (anterior) part of the PPF and 22% into the deep part of the PPF.4 7 This approach was used in a prospective double-blinded randomized control trial of 60 pediatric patients undergoing cleft palate repair and in a case report of 5 adult patients undergoing maxillary osteotomies, both showing decreased morphine consumption in the first 48 and 24 hours postoperatively, respectively.7 10
Discussion
These studies demonstrate that the PPF is a readily accessible target for the ultrasound-guided maxillary nerve block. The PPF is a pyramidal shaped space bounded by the maxillary bone anteriorly, lateral pterygoid plate of the sphenoid bone posteriorly, and orbital apex superiorly which contains the maxillary nerve (V2), maxillary artery, and sphenopalatine ganglion and communicates with the infratemporal fossa via the pterygomaxillary fissure. Injectate placed in the upper part of the PPF can travel posteromedially through the foramen rotundum into the middle cranial fossa which contains the gasserian ganglion, resulting in blockade of the branches of the trigeminal nerve (figures 4 and 5).1 3 5 14 This path was used by Huang et al who performed a V2 radiofrequency ablation through the upper part of the foramen rotundum using CT-scan guidance.15 The gasserian ganglion is the sensory ganglion of the trigeminal nerve (CN V) that lies within Meckel’s cave in the middle cranial fossa and gives rise to three branches—ophthalmic (V1), maxillary (V2), and mandibular (V3)—which exit the skull through three foramina: the superior orbital fissure, the foramen rotundum and the foramen ovale.5 16 In addition, all the contents of the PPF will be blocked, which includes the internal maxillary artery and its branches, the maxillary nerve, and the sphenopalatine ganglion and its afferent and efferent branches.3 17 18
The strengths and weaknesses of the approaches to the ultrasound-guided maxillary nerve blocks via the PPF and the studies describing them are described in tables 2 and 3.1 3–13 Sphenoid bone contact was often required in the anterior infrazygomatic and suprazygomatic approaches, which can cause significant pain.4 6 7 The parotid gland, facial nerve and artery lay superficial to the mandibular notch and are at risk during the posterior infrazygomatic approach (figure 5).3 Technical factors such as acute angle of insonation (anterior infrazygomatic) or out-of-plane approach (suprazygomatic) make real-time needle tip visualization difficult or impossible. With the out-of-plane approach (suprazygomatic), the needle cannot be evaluated at the entry point and can only be seen after it passes beneath the zygoma. This poses a risk of damage to surrounding soft tissues and neurovascular structures. Puncture of the maxillary artery is of chief concern due to its tortuous course in the PPF in a posterior–anterior and lateral–medial course.3 14 This risk can be minimized by placing the needle tip at the level of the pterygomaxillary fissure beneath the lateral pterygoid muscle, allowing the muscle to indirectly force injectate into the PPF, as in the posterior infrazygomatic approach.5
Traditionally, fluoroscopy is used to perform the maxillary nerve block due to user familiarity and ability to rule out intravascular injection with contrast. Ultrasound is a safe alternative due to real-time visualization of the needle tip and surrounding vasculature and soft tissues and lack of radiation exposure (see table 1). However, obtaining a high-quality ultrasound image can be technically challenging due to the deep location of the neurovascular structures in the PPF.
Conclusions
Approaches to the ultrasound-guided maxillary nerve blocks via the PPF have been successfully described each with unique challenges. Ultrasound offers significant safety and efficacy advantages related to real-time visualization of vasculature and soft tissues along with needle advancement as opposed to the standard fluoroscopy-guided approach, although there are challenges to the ultrasound-guided approach since the target structures are deep and visualization can be obscure at times. The ideal approach is yet to be determined and must be further explored.
Supplementary materials
Supplementary Data
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Footnotes
Contributors AN contributed to the conception and design of the research, and critical revision of the manuscript. AA contributed to the literature and drafting of the manuscript. All authors contributed to the final approval of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval IRB approval was not required for this review.
Provenance and peer review Not commissioned; externally peer reviewed.