Suprazygomatic maxillary nerve block: an ultrasound and cadaveric study to identify correct sonoanatomical landmarks.

​PURPOSE: Suprazygomatic maxillary nerve blocks (SMB) are used in adult and pediatric patients to provide analgesia for midface surgery and chronic maxillofacial pain syndromes. The ultrasound-guided SMB technique ensures visualisation of the needle tip, avoidance of the maxillary artery and confirmation of local anesthetic spread. The goal of this study was to correctly identify SMB sonoanatomical landmarks to ensure the nerve block is performed safely and effectively. METHODS: Following an ultrasound-guided SMB with dye injection on 2 embalmed cadavers, pre-tragal face-lift style incision with a full thickness flap dissection was performed allowing accurate visualization of the bony landmarks being used for sonography and identification of the location of the injected dye. RESULTS: This study identifies the correct sonoanatomic landmarks as the maxilla and the coronoid process of the mandible which suggests that the block needle tip and local anesthetic injection are within the infratemporal fossa as opposed to the previously reported pterygopalatine fossa. CONCLUSION: An improved understanding of the sonoanatomy will aid clinicians who are learning, performing and teaching the ultrasound-guided suprazygomatic approach to the maxillary nerve block.

A morphometric analysis of the immature human infraorbital canal.

PURPOSE: The importance of the infraorbital canal in the growth of the maxilla and associated mid-facial region has significance for innervation of this region as well as the associated dentition, yet little is known about the development of the canal. An analysis of its dimensions and morphology during the late prenatal and early postnatal periods was thus undertaken. The aim of this study was to describe changes in the morphology, size and branching pattern of the infraorbital canal during the late prenatal and early postnatal stages of human growth. METHODS: Fifty human fetal and neonatal maxillae were analyzed. The sample included 27 late prenatal individuals (30 gestational weeks and birth) and 23 early postnatal individuals (birth and 1 year). Maxillae were scanned using a Nikon XTH 225 L micro-CT unit and analyzed using VG studiomax v3.2. Measurements included the maximum width, height and surface area of each foramen associated with the infraorbital canal and the total length of the canal, bilaterally. RESULTS: All the measurements of the canal were greater in the early postnatal group than in the late prenatal group, while the walls and branching pattern of the canal were better developed in the postnatal group. Bone development occurred within the walls as development proceeded. Variations in the branching pattern of the canal were found. CONCLUSION: The morphology of the infraorbital canal reflected the developmental stage of associated structures such as the dentition, maxillary sinus and orbit.

Ultrasound-guided maxillary nerve block: an anatomical study using the suprazygomatic approach.

PURPOSE: Although a maxillary nerve (MN) block reportedly provides satisfactory analgesia for midface surgery and chronic maxillofacial pain syndromes, a safe and reliable MN block technique has not been reported. The goal of this anatomical study was to quantify the various angles and depth of the block needle, as well as to evaluate the impact of volume on the extent of injectate spread that might influence anesthetic coverage and block-related complications. METHODS: Following an ultrasound-guided suprazygomatic MN block with dye injection, a dissection was performed in the pterygopalatine fossa (PPF) of four lightly embalmed cadaveric specimens. Half of the specimens were injected with 5 mL of dye, and the other half with 1 mL of dye. The needle depth was measured from the ultrasound images and using rubber markers. Following injection, dissection was performed to map the area of dye spread. RESULTS: The median [interquartile range (IQR)] distance from the skin to the PPF was 37 [36-43] mm and 47 [40-50] mm by ultrasound and rubber marker methods, respectively. The median [IQR] needle orientation was 14 [11-32] degrees inferiorly and 15 [10-17] degrees posteriorly. The PPF was consistently dyed in the 5 mL group, but sporadically dyed in the 1 mL group. In the 5 mL group, spread outside of the PPF was seen. CONCLUSIONS: We showed that 5 mL of injectate far exceeds the capacity of the PPF, leading to drug spread outside of the PPF. Moreover, we found that 1 mL of injectate largely covered the nerve, suggesting a more efficacious and safer block procedure. This finding will need confirmation in future clinical studies.

Infraorbital Foramen Decompression Surgery for the Infraorbital Nerve Hypoesthesia in Patients With Isolated Fracture of Maxillary Sinus Anterior Wall.

Isolated fracture of maxillary sinus anterior wall is relatively uncommon. If the extent of fracture is minimal, only conservative care is amenable, however, there is no agreement on whether infraorbital nerve dysfunction can be used as an indication for surgical intervention. This study was conducted to verify the effect of decompression surgery of infraorbital foramen for recovery of hypoesthesia. A total of 26 patients with unilateral fracture of maxillary sinus anterior wall were enrolled. Ten who received only conservative therapy were allocated in the control group, while sixteen patients were assigned to the decompression group. Pre- and post-treatment sensory assessment using visual analogue scale (VAS) was recorded. Overall treatment satisfaction was also evaluated by means of global assessment scale (GAS). Both absolute VAS value and score increment showed statistical difference only at 4 weeks (P = 0.010 and P = 0.021, respectively), but no significant difference at 1, 12, and 24 weeks. GAS score also showed no statistical significance (P = 0.386). Decompression surgery of infraorbital foramen does not have a significant effect on hypoesthesia recovery in isolated fracture of maxillary sinus anterior wall. Therefore, it is not recommended to perform the operation when the infraorbital nerve hypoesthesia is the only indication for the open reduction.

Revisiting major anatomical risk factors of maxillary sinus lift and soft tissue graft harvesting for dental implant surgeons.

The anatomical variations of the maxillary sinus septa, greater palatine artery, and posterior superior alveolar arteries might cause unexpected complications when they are damaged. Dentists who know these structures well might hope to learn more practical knowledge to avoid and assess injury preoperatively. Therefore, this review paper aimed to review the reported anatomy and variations of the maxillary sinus septa, greater palatine artery/nerve, and posterior superior alveolar artery, and to discuss what has to be assessed preoperatively to avoid iatrogenic injury. To assess the risk of injury of surgically significant anatomical structures in the maxillary sinus and hard palate, the operator should have preoperative three-dimensional images in their mind based on anatomical knowledge and palpation. Additionally, knowledge of the average measurement results from previous studies is important.

False and true accessory infraorbital foramina, and the infraorbital lamina cribriformis.

The infraorbital nerve (ION) and artery (IOA) course in the infraorbital canal (IOC) to exit through the infraorbital foramen (IOF). Few previous studies brought evidence of accessory IOF. Evaluation of the IOF in Cone Beam Computed Tomography (CBCT) is more accurate to determine whether or not foramina of maxilla are supplied by canaliculi deriving from the IOC. We performed a retrospective anatomical study of the CBCT files of 200 patients. An accessory infraorbital foramen located inferior to the infraorbital margin (AIOF) was found in 18/200 right maxillae and in 13/200 left ones. Canaliculi deriving from the IOC supplied accessory foramina in the sutura notha- AIOF(SN) - in 15 maxillae. Noteworthy, the AIOF(SN)-negative maxillae displayed the SN and the vascular foramina of Macalister. In 94% of cases the AIOF were unique. A single maxilla (3%) had a double AIOF. In a different case (3%) were found three accessory infraorbital foraminules transforming the anterior wall of the antrum into a veritable lamina cribriformis infraorbitalis. A single prior study distinguished AIOF from AIOF(SN), while most of different other ones were performed on dry bones. Therefore, the reports of prevalence for the number and location of AIOF should be regarded with caution. Foramina of the SN could equally get intraosseous and extraosseous supply, this distinction being accurately made in CBCT.

Infraorbital Nerve Located Medially to Postoperative Maxillary Cysts: A Risk of Endonasal Surgery.

BACKGROUND/AIMS: This study aimed to examine variations in the location of the infraorbital nerve relative to postoperative maxillary cysts to assess the potential risk of nerve injury during endonasal marsupialization. METHODS: Coronal computed tomography images of 130 patients (162 sides) with postoperative maxillary cysts who visited our clinic between 2003 and 2014 were reviewed from the viewpoint of the anatomical relationship between the infraorbital nerves and cysts. RESULTS: The proportions of the six locations were as follows: upside 45.1% (n = 73), separate 13.0% (n = 21), medial 5.6% (n = 9), lateral 14.2% (n = 23), in-between 7.4% (n = 12), and unevaluable 14.8% (n = 24). The proportion of the cases with a potential risk of infraorbital nerve damage during endoscopic marsupialization, including medial, in-between, and unevaluable locations, was 27.8%. Retrospective chart review revealed that 2 patients with a postoperative maxillary cyst that were unevaluable complained of persistent postoperative hypoesthesia of the cheek. CONCLUSION: The anatomical relationship between the infraorbital nerve and postoperative maxillary cysts varied among patients, with approximately one-fourth of the patients being at risk of infraorbital nerve injury even during endoscopic procedures.

Blind versus ultrasound-guided maxillary nerve block in donkeys.

OBJECTIVES: To describe the 'blind' and ultrasound-guided approaches to block the maxillary nerve in donkeys. To compare the success and complication rates between the 'blind' and ultrasound-guided techniques based on staining of nerves and other structures in cadavers and assessing level of analgesia in live animals. STUDY DESIGN: Prospective anatomical and experimental study. ANIMALS: Eighteen cadaver heads and nine adult live donkeys. METHODS: Phase 1: the anatomical characteristics of the maxillary nerve and its related structures were investigated within the pterygopalatine fossa in five cadavers. Phase 2: 0.1 mL of methylene blue dye was injected blindly and via ultrasound guidance in 13 cadavers to stain the left and right maxillary nerves, respectively. Nerve staining and dye spreading were evaluated through cadaver dissection. Phase 3: the former procedures were applied in nine live donkeys using lidocaine hydrochloride 2% and the onset of analgesia was verified through needle pricking at the naris. RESULTS: Ultrasound-guided deposition of methylene blue dye in cadavers and lidocaine injection in live animals were successful in all instances (accuracy = 100%) without inadvertent vascular penetration. Using the 'blind' technique, misdirection and intravascular deposition of dye were reported in four cadavers (accuracy = 69.2%) and neurovascular trauma was observed in live donkeys (five cases). Loss of cutaneous sensation in the ipsilateral naris was earlier in the ultrasound-guided approach (10.9 ± 1.8 minutes) than in the 'blind' technique (27.8 ± 3.2 minutes; p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: An ultrasound-guided maxillary nerve blockade proved very practical and can be used to block the maxillary nerve with a high degree of accuracy while avoiding vascular penetration. Further studies are mandatory to validate its analgesic effectiveness in clinical situations.

An anatomical variant: evaluation of accessory canals of the canalis sinuosus using cone beam computed tomography.

BACKGROUND: The anatomical variation of the anterior superior alveolar nerve described as canalis sinuosus (CS) is a less known structure of anterior maxilla. Due to the fact that it contains anterior superior alveolar nerve as well as veins and arteries, exact localisation of this structure will allow surgeons to avoid complications. Hence, the aim of this study was to verify the presence, reveal the frequency and characteristics of accessory canals of CS. MATERIALS AND METHODS: This study was based on retrospective evaluation of cone beam computed tomography (CBCT) scans. A total of 1460 CBCT images were analysed and collected data were noted. The following parameters were recorded: age, sex, presence or absence of CS, location in relation to the adjacent teeth and impaction of canine teeth. RESULTS: A total of 6668 accessory canals were found in 1460 CBCT images. Of these, 672 (46.0%) were from female patients, and 788 (54.0%) were from male patients. 1034 (70.8%) of 1460 images had at least one accessory canal of CS. Maxillary intercentral region is the area where accessory canals were seen most frequently (n = 653, 44.72%). CONCLUSIONS: Canalis sinuosus is a bony canal which is incidentally found and less known structure of anterior portion of maxilla. Knowing the accessory canals deriving from this structure will allow surgeons to avoid complications and non-integration after dental implant procedures. Conventional imaging modalities have limited value in detecting this neurovascular structures. Therefore CBCT may have an important role for accurate diagnosis to reveal anatomical variations.

Ectopic Infra Orbital Nerves: Case Series of a Dangerous Normal Variant.

Normal variations in the paranasal sinus region are well documented in literature. We present five cases of a little known normal variant, which can have serious implications for the patient as well as the operating surgeon. An ectopic infra orbital nerve canal coursing through the maxillary sinus has rarely been described in imaging literature. This may sometimes be mistaken for a simple septum in the maxillary sinus and may cause serious complications during Functional Endoscopic sinus surgery (FESS) surgeries. We describe the imaging findings and present a brief review of the previous publications on the same subject.

Three-Dimensional Reconstruction of the Distribution of Neurons Contributing to Ophthalmic, Maxillary, and Mandibular Nerves in the Trigeminal Ganglion of Experimental Model.

The authors introduce a new method to build a three-dimensional (3D) model of the 3 branches of the trigeminal nerve in the trigeminal ganglion of rabbit with 3 different kinds of fluorescence. Ten adult New Zealand rabbits of both sexes weighing between 2.0 and 3.0 kg were used in the experiment. Then through an operation under general anesthesia, the maxillary and mandibular nerves were exposed, and red and gold fluorescence were applied to investigate the neurons of the maxillary and mandibular nerves. Subsequently, DiI was used as a marker for the ophthalmic neuron for the other side of the same rabbit. After receiving images of the 3 branches under a fluorescence microscope, a 3D model of the 3 branches of the trigeminal nerve could be built. The authors obtained an image of the 3 branches of neurons in the trigeminal ganglion, and a 3D model of the 3 branches of the trigeminal nerve in the trigeminal ganglion was reconstructed. In the trigeminal ganglion, ophthalmic neurons were concentrated in the anteromedial section, the maxillary division in the middle, and the mandibular division posterolaterally. Overlap was observed between the ophthalmic and maxillary neurons, and also for the maxillary and mandible neurons.

Maxillary nerve blocks in horses: an experimental comparison of surface landmark and ultrasound-guided techniques.

OBJECTIVE: The aim of this preliminary proof-of-concept study was to evaluate and compare the success and complication rate of infiltration of the maxillary nerve of cadaver heads using previously described surface landmarks, standard ultrasound and a novel needle guidance positioning ultrasound system (SonixGPS). STUDY DESIGN: Prospective, anatomical, method-comparison study. ANIMALS: Thirty-eight equine cadaver heads. METHODS: Twenty-six veterinary students performed the three methods consecutively on cadaver heads using an 18 gauge, 8.9 cm spinal needle and 0.5 mL iodinated contrast medium. Computed tomography was used to quantify success (deposition of contrast in contact with the maxillary nerve) and complication rate (contrast identified within surrounding vasculature or periorbital structures) associated with each method. RESULTS: Perineural injection of the maxillary nerve was attempted 76 times, with an overall success rate of 65.8% (50/76) and complication rate of 53.9% (41/76). Success rates were 50% (13/26) with surface landmark, 65.4% (17/26) with standard ultrasound guidance and 83.3% (20/24) with SonixGPS guidance approaches (Fisher's exact test, p=0.046). No significant difference in complication rate was found between the three methods. CONCLUSIONS: Ultrasound-guided maxillary nerve blocks were significantly more successful than surface landmark approaches when performed by inexperienced operators, and the highest success rate was achieved with guidance positioning system (GPS) needle guidance. CLINICAL RELEVANCE: Local anaesthesia of the equine maxillary nerve in the fossa pterygopalatina is frequently used for diagnostic and surgical procedures in the standing sedated horse. Due to vague superficial landmarks with various approaches and the need for experience via ultrasound guidance, this block remains challenging. GPS guidance may improve reliability of maxillary and other nerve blocks, and allow a smaller volume of local anaesthetic solution to be used, thereby improving specificity and reducing the potential for side effects.

Orbital Floor Thickness in Adult Patients With Isolated Orbital Floor Fracture Lateral to the Infraorbital Nerve.

Orbital floor fractures commonly occur just medial to the junction of the infraorbital nerve and the inferior orbital fissure because the bone is thinner posteromedial to the infraorbital nerve than that lateral to the nerve. The authors previously reported 2 pediatric patients with an isolated orbital floor fracture lateral to the infraorbital nerve. The authors showed that, on the unaffected side of these patients, the lateral portion of the orbital floor was thinner than the medial portion. In the present study of 5 adult patients with an isolated orbital floor fracture lateral to the infraorbital nerve, the authors compared the thickness of the medial and lateral portions of the orbital floor with that of the infraorbital nerve on the unaffected side. Computed tomographic images showed that the bone lateral to the infraorbital nerve was somewhat thinner than bone in the medial portion. Because the orbital structures are generally symmetrical, our findings suggest that these 5 patients had partial anatomical weakness in the lateral portion of the infraorbital nerve on the affected side, resulting in an isolated orbital floor fracture lateral to the infraorbital nerve.

Posttraumatic Midface Pain: Clinical Significance of the Anterior Superior Alveolar Nerve and Canalis Sinuosus.

BACKGROUND: Posttraumatic midface pain secondary to injury of the anterior superior alveolar nerve (ASAN) is characterized as pain localized to the central and lateral incisors, canines, and maxilla. This nerve is susceptible to injury and subsequent formation of neuromas after midface trauma. Surgical intervention requires an accurate and precise understanding of the course of the ASAN. METHODS: Dissections of 12 human cadaver heads were conducted to identify the course of the ASAN through the canalis sinuosus (CS). Fifty 1-mm slice face computed tomographic scans were evaluated to document the dimensions and course of the CS. RESULTS: The ASAN branched laterally from the infraorbital nerve before reaching the infraorbital rim in all cadavers. The bifurcation occurred 18 mm posterior to the infraorbital rim (range, 10-30 mm). At a point 25 mm inferior to the infraorbital rim, the ASAN is found 3.4 mm lateral to the piriform aperture (range, 3-4 mm). Radiographic analysis demonstrated a 12.9-mm horizontal length of the CS across the anterior maxilla (SD, 2.2 mm), a distance of 4.8 mm between the piriform aperture and the CS (SD, 1.2 mm), and 11.7 mm vertical length of the CS along the piriform aperture (SD, 3.0 mm). CONCLUSIONS: The ASAN maintains consistent coordinates at specific points along its course through the midface. An improved understanding of the course of the ASAN will guide future diagnosis of injury to this nerve and surgical intervention for patients with posttraumatic midface pain secondary to ASAN injury.

Branch of the canalis sinuosus: a rare anatomical variation--a case report.

The canalis sinuosus (CS) is a neurovascular canal, a branch of the infraorbital canal through which the anterior superior alveolar nerve passes. There are no studies or case reports of anatomical variations related to this canal. A rare case of anatomical variation in the CS is reported that was detected by cone beam computed tomography done in a 47-year-old female as a pre-operative workup before dental implants. In this case, in the region slightly medial to tooth 23, a wide accessory branch from the CS was observed, running an intraosseous course in the inferior and posterior direction up to a foramen located in the hard palate, slightly medial in relation to tooth 23. The location of this branching, as well as its neurovascular component, is important for dental implant planning because of its proximity to the upper teeth. Identification of neurovascular bundles is fundamental to avoid complications for the patient.

Canalis Sinuosus Mimicking Periapical Pathology on, Radiographic Assessment.

The canalis sinuosus is an anatomical variation whereby the infraorbital canal sometimes generates a small, lateral branch (canal) close to its midpoint, to allow the passage of the anterior superior alveolar neurovascular bundle in the anterior maxilla. This article focuses on an incidental finding of this variant, in a 74-year-old Trinidadian female of Afro-Caribbean descent with an endodontic presenting complaint. The canalis sinuosus shadow on conventional radiography resulted in uncertainty as to the offending tooth until a 3-dimensional scan was undertaken in this region. This report will discuss the implications of the presence of this canal from radiologic, endodontic, and surgical perspectives.

Ultrasound guidance characteristics and efficiency of suprazygomatic maxillary nerve blocks in infants: a descriptive prospective study.

BACKGROUND: Bilateral suprazygomatic maxillary nerve blocks approach improves pain relief after palate surgery. We report the feasibility and efficiency of ultrasound-guided suprazygomatic maxillary nerve blocks in cleft palate repair in children. METHODS: Twenty-five children scheduled to undergo surgical cleft palate repair were included. Ultrasound-guided suprazygomatic maxillary blocks were performed according to landmarks previously defined. The ultrasound probe was located optimally over the maxilla and under the zygomatic bone to visualize the pterygopalatine fossa. 0.15·ml·kg(-1) of 0.2% ropivacaine was injected bilaterally. Feasibility of block, spread of local anesthetic, pain scores and side effects were noted. RESULTS: Fifty ultrasound-guided suprazygomatic maxillary nerve blocks were performed in 25 children. The needle movement was seen in all cases using an out-of-plane approach. The spread of LA was clearly observed in 94% (47/50) of cases. A poor ultrasound imaging was found in 4% (2/50), and the spread of LA was not identified in 2% of case (1/50). The median time to perform the block was 56 s (35-120 s). The median pain scores and consumption of nalbuphine were low during the study period. 80% of patients did not require continuous opioid infusion. No complication related to maxillary blocks was reported. CONCLUSION: With a very low technical failure rate and a good clinical success rate, ultrasound appears to be a useful and simple tool to aid suprazygomatic maxillary nerve block in children.

Microanatomy of the infraorbital canal and its connecting canals in the maxilla using 3-D reconstruction of microcomputed tomographic images.

The current study investigated the anatomy of the infraorbital canal (IOC) and its related small canals in the maxilla. Twenty-eight hemimaxillae from human cadavers were studied. The samples were scanned using microcomputed tomography, and then images were three-dimensionally reconstructed using computer software. The branch point of the canal into the anterior superior alveolar nerve from the IOC occurred at about one third along the length of the IOC in the anterior direction. Just over half of the cases had 1 canal. The branch arose either laterally (21/28) or inferiorly (7/28) from the IOC. There was a canal located at the inferior lateral border of the piriform aperture in all cases. The distribution of the canals in the maxilla is represented indirectly by the course and distribution of the nerve and blood vessels therein. This distribution could explain various phenomena encountered in the clinical field.

Canalis sinuosus: a rare anatomical variation.

The infraorbital canal issues a small branch on its lateral face close to its midpoint to allow passage of the anterior superior alveolar nerve. This small canal, sometimes called the canalis sinuosus, runs forward and downward to the inferior wall of the orbit, lateral to the infraorbital canal and medially bent to the anterior wall of the maxillary sinus, passing below the infraorbital foramen. Anatomical variations in the maxilla are rarely described in the literature and, in most cases, are related to the nasopalatine canal. This article describes a rare anatomical variation of the presence of a bilateral accessory canal extending from the nasal cavity lateral wall to an accessory foramen located on the hard palate, adjacent to the maxillary lateral incisor observed in cone beam computed tomography (CBCT) images. This case is an anatomical variation of the anterior superior alveolar nerve (canalis sinuosus). Identification of individual anatomical variations, especially on CBCT, may help the surgeon to avoid injuries to nerves during implant placement.