Infraorbital canal variants and its clinical and surgical implications. A systematic review

BACKGROUND

Recent literature highlights anomalous cranial nerves in the sinonasal region, notably in the sphenoid and maxillary sinuses, linked to anatomical factors. However, data on the suspended infraorbital canal (IOC) variant is scarce in cross-sectional imaging. Anatomical variations in the sphenoid sinuses, including optic, maxillary, and vidian nerves, raise interest among specialists involved in advanced sinonasal procedures. The infraorbital nerve's (ION) course along the orbital floor and its abnormal positioning within the orbital and maxillary sinus region pose risks of iatrogenic complications. A comprehensive radiological assessment is crucial before sinonasal surgeries. Cone-beam computed tomography (CBCT) is preferred for its spatial resolution and reduced radiation exposure.

OBJECTIVE

The aim of this study was to describe the prevalence of anatomical variants of the infraorbital canal (IOC) and report its association with clinical condition or surgical implication.

METHODS

We searched Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS databases from their inception up to June 2023. Two authors independently performed the search, study selection, data extraction, and assessed the methodological quality with assurance tool for anatomical studies (AQUA). Finally, the pooled prevalence was estimated using a random effects model.

RESULTS

Preliminary results show that three types are prevalent, type 1: the IOC does not bulge into the maxillary sinus (MS); therefore, the infraorbital foramen through the anterior wall of MS could be used for identification of the ION. Type 2: the IOC divided the orbital floor into medial and lateral aspects. Type 3: the IOC hangs in the MS and the entire orbital floor lying above the IOC. From which the clinical implications where mainly surgical, in type 1 the infraorbital foramen through the anterior wall of MS could be used for identification of the ION, while in type 2, since the lateral orbital floor could not be directly accessed an inferiorly transposition of ION is helpful to expose the lateral orbital wall directly with a 0 scope; or using angled endoscopes and instruments, however, the authors opinion is that direct exposure potentially facilitates the visualization and management in complex situations such as residual or recurrent mass, foreign body, and fracture located at the lateral aspect of the canal. Lastly, in type 3, the ION it's easily exposed with a 0° scope.

CONCLUSIONS

This systematic review identified four IOC variants: Type 1, within or below the MS roof; Type 2, partially protruding into the sinus; Type 3, fully protruding into the sinus or suspended from the roof; and Type 4, in the orbital floor. Clinical recommendations aim to prevent nerve injuries and enhance preoperative assessments. However, the lack of consistent statistical methods limits robust associations between IOC variants and clinical outcomes. Data heterogeneity and the absence of standardized reporting impede meta-analysis. Future research should prioritize detailed reporting, objective measurements, and statistical approaches for a comprehensive understanding of IOC variants and their clinical implications. Open Science Framework (OSF): https://doi.org/10.17605/OSF.IO/UGYFZ .

A rare variation of the infraorbital nerve, entrapping the infraorbital artery

Anatomical variations are a common feature of the human anatomy. Variation can explain some pathological conditions and is important to keep them in mind during surgical procedures. The relations between nerves and their adjacent arteries have been proposed to play a role in the generation of peripheral trigger migraines. Close opposition between nerves and arteries can lead to vascular compression of the nerve that triggers episodes of pain. We did a routine dissection of the infratemporal fossa and orbital floor by opening the maxillary sinus. Here we report a case where the infraorbital nerves form a nervous loop entrapping the infraorbital artery in the infraorbital channel. Similar cases of close nervous and arterial apposition are described for the auriculotemporal and occipital nerves. We think that accumulating knowledge of these rare variations could expand our understanding of rare conditions such as primary infraorbital neuralgia.

Assessment of canalis sinuosus, rare anatomical structure using cone-beam computed tomography: A prospective study

Objectives

This prospective study was performed with cone-beam computed tomography (CBCT) images for evaluating canalis sinuosus (CS), determine its location and diameter in relation to gender, age, and distances from important structures, including floor of nasal cavity, incisive foramen, edge of buccal cortical bone, and palatal cortical bone.

Material and Methods

The scans of 650 patients in total were included in this prospective analysis. Gender, age, the position of the CS, its presence or absence, diameter, and its location in reference to the adjacent teeth were the factors that were noted.

Results

The study had 301 female participants and 349 male participants, with a mean age of 42.19. Compared to females, males had a statistically higher frequency of CS. Higher age groups showed a higher presence of CS in comparison to the other age groups. The mean distances of these parameters on the left and right side did not differ significantly. Nonetheless, the distance on both sides between CS and nasal cavity floor for males and females, as well as the diameter and border of buccal-palatal cortical bone on the right side, were statistically significant different. On the left side, both genders demonstrated significance in buccal cortical margin and nasal cavity floor. IIn addition, in females, the diameter of the CS on the right and left sides differed on average. The associations between age and number of CS, CS diameter, and number of CS versus sex were all extremely weak. Overall, the study findings showed that CS is a typical anatomical feature in anterior maxillary region, irrespective of age, or gender.

Conclusion

The bony canal, CS is an obscure feature located in the frontal region of the maxilla. Surgeons can avoid complications by being aware of the auxiliary canals derived from this structure. With the use of CBCT, it is now feasible to examine the course of CS as it passes through the maxillary sinus's anterolateral wall with better radiological accuracy has already been documented.

Does mandibular osteotomy affect the infraorbital nerve? a prospective study

OBJECTIVES

The aim of this study was to evaluate the sensory function of the infraorbital nerve after orthognathic surgery (OS).

MATERIALS AND METHODS

Patients who underwent Le Fort I osteotomy with or without BSSO for dentofacial deformity treatment were studied. Two groups were created according to whether BSSO was performed. Class A tests were performed to determine the degree of peripheral nerve damage. The Class B test was performed if decreased sensation was detected in at least one of these tests. A Class C test was performed if abnormal sensation was detected.

RESULTS

Twenty-eight patients (n=56) who underwent OS were included in this prospective study. Of the patients, 57.1% were female, 42.9% were male, and the mean age was 24.6 (±3.8). Seven patients were in group 1 (n=14), and 21 patients were in group 2 (n=42). In both groups, there were statistically significant differences between T1 and T2 (p<0.001), and the mean NSD score at T2 was higher than that at T1. The mean NSD score in the single jaw group was higher than that in the double jaw group at all time points.

CONCLUSIONS

Bimaxillary surgeries had a negative effect on the somatosensory changes that developed in the early period. The upper lip's somatosensorial recovery was faster than IOR and single jaw recovery was faster than double jaw.

CLINICAL RELEVANCE

Maxillofacial surgeons performing orthognathic surgery should be aware that in double jaw operations, changes in the somatosensory function of the ION are more severe.

Pediatric Infraorbital Nerve schwannoma-A Rare Case Report

Infraorbital nerve schwannoma is an infrequent entity that is rarely reported in the paediatric population. This case report is a summed-up report of this infrequent diagnosis, its presentation, and management from an otorhinolaryngologist's perspective. It is reported here for its rarity, inherent surgical challenge, and academic interest. We report a case of a 13-year-old boy with infraorbital nerve schwannoma arising from its two terminal branches. We performed its surgical excision without any disabling deformity. The peculiarity of this case gives insight into the varied presentation of schwannoma. It is important to identify such cases with a high degree of suspicion and treat them accordingly.

The relationship between orbital floor fracture patterns around the infraorbital groove and development of infraorbital nerve hypoesthesia: a computed tomographic study

PURPOSE

To examine the relationship between patterns of orbital floor fracture around the infraorbital groove and development of infraorbital nerve hypoesthesia.

METHODS

This retrospective, observational study included 200 patients (200 sides) of pure orbital floor fracture with or without medial orbital wall fracture. Data on the presence or absence of infraorbital nerve hypoesthesia were collected from medical records. Based on coronal computed tomographic images, patients were classified into 3 groups: a fracture extending medially to (medial group), into (in-groove group), and laterally to the infraorbital groove (lateral group).

RESULTS

Infraorbital nerve hypoesthesia was found in 72 patients (36.0%). A fracture extended into or laterally to the infraorbital groove in 86.2% of patients with infraorbital nerve hypoesthesia, while a fracture was limited to the portion medial to the infraorbital groove in 77.3% of patients without infraorbital nerve hypoesthesia (P < 0.001). A logistic regression analysis demonstrated that patients in the lateral and in-groove groups were highly associated with development of infraorbital nerve hypoesthesia, with an odds ratio of 134.788 in the lateral group (95% confidence interval, 30.496-595.735; P < 0.001) and that of 20.323 in the in-groove group (95% confidence interval, 6.942-59.499; P < 0.001) with the medial group as the reference.

CONCLUSIONS

This study indicates that patients with orbital floor fracture extending into or laterally to the infraorbital groove have a high risk of infraorbital nerve hypoesthesia, compared to those with orbital floor fracture limited to the portion medial to the infraorbital groove.

Sublabial Approach Versus Modified Denker's Procedure: A Comparative Study of Pre-maxillary Tissue Clearance in Covid-Associated Mucormycosis

To compare the efficacy of the sublabial and modified Denker's procedure in clearance of fungal disease from the anterior wall of maxilla and the pre-maxillary area i.e. the difficult areas of maxillary sinus. A prospective observational study was conducted over a period of 2 months (April 21-June 21) in the ENT department of Sawai Man Singh hospital, Jaipur. All the patients with clinical involvement of the premaxilla or the cheek abutting the anterior wall of maxilla were included in the study population. Cases matched in both groups were subjected to debridement either by the sublabial or the modified denker's approach. Outcomes were measured by assessing the daily CRP values, post-operative DNE every 3 days after pack removal, and imaging at the end of 1 month. Repeat biopsies were performed in patients that still had persistent symptoms after getting operated on. 16 of the 60 patients (26.6%) operated on by the endoscopic approach showed evidence of residual disease on follow-up whereas only 5 patients (9.6%) in the other category had a similar outcome. Most of the recidivism was seen in the anterior maxilla. Lower rates of complications were found following debridement by the sublabial approach. Since the sublabial approach is the most direct approach for the key areas of fungal involvement of maxillary sinus, it is recommended over the modified Denker's procedure for disease clearance from pre maxilla and the anterior wall of maxillary sinus. This view is also supported by the lower rates of complications encountered following the former.

Management of Infraorbital Rim Fracture Through Intraoral Approach

Purpose

The aim of our study was to evaluate the feasibility of an intraoral approach in the management of infraorbital rim fracture.

Patients and Methods

A total of 12 patients of which four were female and five were male with isolated unilateral zygomaticomaxillary complex (ZMC) fractures, essentially involving the infraorbital foramen (right or left), were included in this study. Indications for surgical intervention were cosmetic deformity, disturbance of vision, persistent paresthesia, or impaired mandibular movement. All the patients were subjected to thorough preoperative evaluation. A three-point fixation was performed in all the patients. Various parameters such as time required for exposure and the amount of accessibility were assessed intraoperatively, while the stability of the fixation and paresthesia pertaining to the distribution of the infraorbital nerve were assessed postoperatively.

Results

A total of 12 patients with a mean age of 35.75 ± 12.7 years were included in the study. The mean time recorded for exposure and fixation was 21.33 ± 2.8 min. The accessibility was rated as "excellent" in 92% (11 patients) of the operated cases and rated "satisfactory" in 8% (1 patient) of the operated cases. The fixation was found to be stable in 100% of the cases. By the end of 8 months, normal mechanoreceptor response was elicited in 42% (five patients) of the cases and normal nocireceptor response was elicited in 92% (11 patients) of the cases.

Conclusion

The intraoral approach for fixation of the infraorbital rim is versatile and can be mastered even by novice surgeons. The virtual lack of complications and short learning curve make this approach an invincible modus operandi in a surgeon's repertoire.

Evaluation of Infraorbital Nerve Recovery and its Effect on Quality of Life following Open Reduction and Internal Fixation of Zygomaticomaxillary Complex Fractures - An Evaluative Study

Introduction

The zygomaticomaxillary complex (ZMC) fractures are the second most common fractures affecting the midfacial skeleton. Neurosensory disturbances of the infraorbital nerve are one of the most common signs of ZMC fractures. The aim of the study was to evaluate the neurosensory recovery of the infraorbital nerve and its effect on the quality of life (QoL) following open reduction and internal fixation of ZMC fractures.

Methods

Thirteen patients clinically and radiologically diagnosed with unilateral ZMC fractures with neurosensory deficits of the infraorbital nerve were enrolled for this study. All patients were assessed presurgically for neurosensory deficits of the infraorbital nerve using the various neurosensory tests, followed by open reduction with two-point fixation under general anaesthesia. The patients were followed up at one, three and six months postoperatively to evaluate the recovery of neurosensory deficits.

Results

Recovery of tactile and pain sensation was relatively complete in 84.62% and 76.92% of patients respectively by the end of six months postoperatively. The spatial mechanoreception of the affected side improved significantly. 61.54% of patients led an excellent QoL six months postoperatively.

Discussion

The majority of the patients with ZMC fractures and neurosensory deficits of the infraorbital nerve, when treated with open reduction and internal fixation, have complete recovery of the neurosensory deficits by the end of six months postoperatively. However, some patients may continue to experience some long-term residual deficits, which can affect the patient's QoL.

Anti-nociceptive effects of ECa 233 a standardized extract of Centella asiatica (L.) Urban on chronic neuropathic orofacial pain in mice

ETHNOPHARMACOLOGICAL RELEVANCE

ECa 233 is a standardized extract of Centella asiatica (L.) Urban, a herb traditionally used to treat a number of diseases including neurological disorders. Accordingly, ECa 233 showed benefits on animal models of cognitive deficits, chronic stress and Parkinson's disease. Analgesic activity of ECa 233 was shown in Tail's flick test in rodent and relieving aphthous ulcer pain in man. Moreover, acute and sub-chronic toxicity testing in rodents and pharmacokinetic study in healthy volunteers, clinical trial phase I demonstrated good safety profiles of ECa 233.

AIM OF THE STUDY

This study aims to evaluate the anti-nociceptive effects of ECa 233 and its synergistic effect with gabapentin on chronic neuropathic orofacial pain after 3 weeks infraorbital nerve chronic constriction injury in mice. The peripheral and central nociceptive activities are also examined.

MATERIALS AND METHODS

Chronic neuropathic orofacial pain was induced by 3 weeks infraorbital nerve chronic constriction injury. Mice were treated with ECa 233 (30, 100 and 300 mg/kg) and gabapentin (10 mg/kg) by oral gavage starting on day 21 and going on for 14 consecutive days. Mechanical hyperalgesia and allodynia were measured on day 7, 14, 21, 28 and 35 after infraorbital nerve chronic constriction injury. At the end of the experiment, mice were observed for the sedative effect using the locomotor activity, the calcitonin gen-related peptide in trigeminal ganglion and c-fos expression in trigeminal nucleus caudalis were investigated after euthanasia.

RESULTS

Infraorbital nerve chronic constriction injury gradually induced marked ipsilateral mechanical hyperalgesia and allodynia. The maximum hyperalgesia and allodynia response presented on day 21 and the response was remained constant until day 35. Treatment with either 300 mg/kg ECa 233 or 10 mg/kg gabapentin were able to attenuate mechanical hyperalgesia and allodynia. The downregulation of calcitonin gen-related peptide on ipsilateral trigeminal ganglion were observed in ECa 233 at 100 and 300 mg/kg and 10 mg/kg gabapentin-treated groups. The c-fos expression on ipsilateral trigeminal nucleus caudalis was also decreased in 300 mg/kg ECa 233 and 10 mg/kg gabapentin-treated groups.

CONCLUSION

ECa 233 reduced hyperalgesia and allodynia by modulating the peripheral calcitonin gen-related peptide expression consequently alleviate the nociceptive activity in trigeminal nucleus caudalis. Further clinical trial to proof ECa 233's efficacy in neuropathic pain in man as well as possible attributable mechanism of action should be further investigated.

Percutaneous Trigeminal Nerve Stimulation Induces Cerebral Vasodilation in a Dose-Dependent Manner

BACKGROUND

The trigeminal nerve directly innervates key vascular structures both centrally and peripherally. Centrally, it is known to innervate the brainstem and cavernous sinus, whereas peripherally the trigemino-cerebrovascular network innervates the majority of the cerebral vasculature. Upon stimulation, it permits direct modulation of cerebral blood flow (CBF), making the trigeminal nerve a promising target for the management of cerebral vasospasm. However, trigeminally mediated cerebral vasodilation has not been applied to the treatment of vasospasm.

OBJECTIVE

To determine the effect of percutaneous electrical stimulation of the infraorbital branch of the trigeminal nerve (pTNS) on the cerebral vasculature.

METHODS

In order to determine the stimulus-response function of pTNS on cerebral vasodilation, CBF, arterial blood pressure, cerebrovascular resistance, intracranial pressure, cerebral perfusion pressure, cerebrospinal fluid calcitonin gene-related peptide (CGRP) concentrations, and the diameter of cerebral vessels were measured in healthy and subarachnoid hemorrhage (SAH) rats.

RESULTS

The present study demonstrates, for the first time, that pTNS increases brain CGRP concentrations in a dose-dependent manner, thereby producing controllable cerebral vasodilation. This vasodilatory response appears to be independent of the pressor response induced by pTNS, as it is maintained even after transection of the spinal cord at the C5-C6 level and shown to be confined to the infraorbital nerve by administration of lidocaine or destroying it. Furthermore, such pTNS-induced vasodilatory response of cerebral vessels is retained after SAH-induced vasospasm.

CONCLUSION

Our study demonstrates that pTNS is a promising vasodilator and increases CBF, cerebral perfusion, and CGRP concentration both in normal and vasoconstrictive conditions.

Endoscopic endonasal approach for repairing an outwardly herniated blow-out fracture lateral to the infraorbital nerve

BACKGROUND

To repair a blow-out fracture, the endonasal approach is indicated when the center of the fracture occurs in the orbital floor medial to the infraorbital nerve, or when the orbital tissue is herniated inwards; additionally, the combined endonasal and transmaxillary approach is indicated for fractures of the anterior and lateral parts of the orbital floor.

METHOD AND CONCLUSION

The use of endoscopic modified medial maxillectomy and special instruments enabled the surgeon to repair an outwardly herniated blow-out fracture by the endonasal approach alone, despite the center of the fracture being in the orbital floor lateral to the infraorbital nerve.

Minimally Invasive Oral Surgery Induction of the FRICT-ION Chronic Neuropathic Pain Model

An easily induced preclinical trigeminal neuropathic nerve injury model is described here for the study of chronic pain, the model acronym FRICT-ION (Foramen Rotundum Inflammatory Constriction Trigeminal InfraOrbital Nerve). In patients, neuropathic pain is thought to be related to vascular alignment or multiple sclerosis along this small trigeminal nerve branch (V2) innervating the maxillary teeth and middle third of the face. With no detectable outward physical signs, the FRICT-ION model is ideal for blinded studies. The acronym FRICT-ION applied relates to the persistence of the trigeminal neuropathic pain model likely due to sliding irritation with normal chewing in the mice. A step-by-step method to induce the mild chronic rodent neuropathic pain model is described here. The surgery is performed orally through a tiny surgical slit inside the cheek crease to align a chromic gut suture irritant along the nerve as it passes into the skull. The model allows testing of non-evoked subjective measures and evoked quantitative mechanical hypersensitivity (allodynia) testing with von Frey filaments through at least 10-14 weeks (100 days). Anxiety and depression behaviors develop within 3-6 weeks relevant to the affective component of chronic pain. While many pain drugs have failed based on testing performed in the acute animal models available, the more stable and easily replicated trigeminal inflammatory compression model is the better suited for understanding both mechanistic and affective components of nerve injury-induced chronic neuropathic pain states as well as the more ideal for preclinical trials of novel non-opioid pain relief therapies.

Peripheral trigeminal branch stimulation for refractory facial pain: A single-center experience

OBJECTIVE

Facial pain refractory to medical treatments may benefit from neurosurgical interventions. Only a few studies have reported on the efficacy of peripheral trigeminal stimulation and more specifically supraorbital nerve (SON) and infraorbital nerve (ION) stimulation for the treatment of facial pain.

PATIENTS AND METHODS

In the present study, we identified all patients at our institution who underwent SON and/or ION stimulation for treatment of facial pain due to post-herpetic, traumatic or idiopathic etiology. Relevant pre and post-operative outcomes were analyzed.

RESULTS

We identified 15 patients who underwent SON and/or ION stimulation. Among them, 12 (80 %) endorsed >50 % pain relief during the trial stimulation period. After a median follow-up of 5.8 months with permanent implantation, 1 patient (8.3 %) was diagnosed with lead erosion and IPG migration, two patients had lead infections (16.7 %) and one (8.3 %) had wound dehiscence. No lead migrations were identified during the long-term follow-up. The VAS score showed a statistically significant reduction from a median pre-operative score of 7 to a post-operative score of 1.8 (p = 0.011), which corresponded to a 74.3 % average pain reduction.

CONCLUSION

SON and/or ION stimulation can be an effective treatment for intractable facial pain due to post-herpetic, traumatic or idiopathic etiology; however the complication rate is relatively high. Future prospective studies with longer follow-up periods are warranted.

Bilateral activation of glial cells and cellular distribution of the chemokine CCL2 and its receptor CCR2 in the trigeminal subnucleus caudalis of trigeminal neuropathic pain model

Glial cells activated by peripheral nerve injury contribute to the induction and maintenance of neuropathic pain by releasing neuromodulating cytokines and chemokines. We investigated the activation of microglia and astrocytes as well as the cellular distribution of the chemokine CCL2 and its receptor CCR2 in the trigeminal subnucleus caudalis (TSC) ipsilateral and contralateral to infraorbital nerve ligature (IONL). The left infraorbital nerve was ligated under aseptic conditions, and sham controls were operated without nerve ligature. Tactile hypersensitivity was significantly increased bilaterally in vibrissal pads of both sham- and IONL-operated animals from day 1 to 7 and tended to normalize in sham controls surviving for 14 days. Activated microglial cells significantly increased bilaterally in the TSC of both sham- and IONL-operated animals with a marked but gradual increase in the ipsilateral TSC from 1 to 7 days followed by a decrease by day 14. In contrast, robust activation of astrocytes was found bilaterally in the TSC of IONL-operated rats from 3 to 14 days with a transient activation in the ipsilateral TSC of sham-operated animals. Cellular distribution of CCL2 varied with survival time. CCL2 immunofluorescence was detected in neurons within 3 days and in astrocytes at later time points. In contrast, CCR2 was found only in astrocytes at all time points with CCR2 intensity being dominant in the ipsilateral TSC. In summary, our results reveal bilateral activation of microglial cells and astrocytes as well as changes in the cellular distribution of CCL2 and its receptor CCR2 in the TSC during the development and maintenance of orofacial neuropathic pain.

Air spaces neighbouring the infraorbital canal

OBJECTIVE

The infraorbital canal (IOC) courses through the roof of the maxillary sinus (MS). Different grading systems concerning the topography of the IOC have been proposed. Further, it has been suggested that a transantral IOC would be morphologically related to Haller's cells (HCs). However, we hypothesized that this is not necessarily the case. Hence, we aimed to study the anatomical possibilities of the air spaces located medially to the IOC.

MATERIALS AND METHODS

The cone-beam computed tomography (CBCT) files of 40 adult patients were retrospectively evaluated.

RESULTS

The transantral type of IOC was found in 32.5% of patients. The infraorbital recesses of the MS were found medial to the IOC in 20% of patients. As referred to the nasolacrimal canal, these recesses were either prelacrimal (appearing as false isolated air cells) or retrolacrimal (appearing as false HCs). True HCs were found in 10% of patients. They were located medial to the IOC and they drained into the ethmoidal infundibulum (EI), which was distinct from the MS drainage. In 15% of patients, aerated nasolacrimal ducts (NLDs) were found anterior to the EI and medial to the antral angle. They were capable of masquerading either a HC or an infraorbital recess of the MS.

CONCLUSION

Previous classifications of the IOC, which related it to HCs, were reviewed and the evidence was found to be insufficient to assess the HC-related topography of the IOC. Therefore, to achieve the accurate anatomical identification of the air spaces neighbouring the IOC, the infraorbital recesses of the MS, the HCs, and the aerated NLDs should be carefully discriminated within the antero-supero-medial antral angle.

A case of traumatic infraorbital neuroma

A 53-year-old Afghan man presented with a 12-month history of left proptosis, diplopia and facial swelling 20 years after a bomb blast injury. Magnetic resonance and computed tomography imaging revealed a well-circumscribed lesion centred within the left inferior orbit/superior maxillary sinus along with left orbital fracture. Histopathology and immunostaining of the debulked lesion were consistent with traumatic neuroma of the infraorbital nerve. Infraorbital neuromas have developed following orbital decompression surgeries but have not been reported previously following non-surgical trauma.

Effects of infraorbital nerve's anatomical course on the fracture pattern of the orbital floor

In this study, details of the infraorbital nerve's (ION's) anatomical course variants were compared using computed tomography (CT), and relationships between the variants and fracture patterns in the orbital floor were investigated. Fifty-two normal individuals and 50 patients with unilateral isolated orbital floor fractures were enrolled in this study. Four measurements in normal individuals and five measurements in fracture patients were obtained in parasagittal sections. The anatomical variations of the ION were categorized into three types according to the classification by Ferences et al. Among the normal individuals, 42 orbits were classified as type 1 ION, 48 orbits as type 2, and 14 orbits as type 3. The distance from the inferior orbital rim to the upper border of the inferior orbital foramen and the length of descension portion of the ION in type 1 ION were significantly shorter than in type 2 and type 3 IONs. In patients with orbital floor fractures, the distance from the inferior orbital rim to the upper border of the inferior orbital foramen was positively correlated with herniation level of bone and soft tissue. The ION had three anatomical variants according to the degree of descension in the anterior portion of the orbit. When fracture of the orbital floor occurs in patients with type 1 ION, inferior displacement of the fractured orbital bone and orbital soft tissue may be less severe than in patients with other ION types.

Effect of Pregabalin and Diclofenac on tactile allodynia, mechanical hyperalgesia and pro inflammatory cytokine levels (IL-6, IL-1β) induced by chronic constriction injury of the infraorbital nerve in rats

The present study evaluated the effects of systemic pregabalin (PG) and diclofenac (Dic) on neuropathic orofacial pain induced by chronic constriction injury (CCI) of the infraorbital nerve (ION) and on the pro-inflammatory cytokines levels in the affected nerve. Fifty-four rats underwent left infra orbital nerve CCI, and 7 days after the procedure as the pain developed, the rats were randomly assigned to one of the treatment groups: PG 300, 30 or 10 mg/kg, Dic 10, 5 or 1 mg/kg or saline group (Sal) (n/group = 8). Addiitonal 8 rats served as naïve control group. Tactile-allodynia and Mechano-hyperalgesia were tested before the surgical procedure and at days 7, 8, and 9 postoperatively. On the 9th day, the rats were euthanized and the affected and contralateral sciatic nerves were harvested to assess IL-6 and IL-1β nerve levels employing enzyme linked immunosorbent assay (ELISA). Daily injection of PG (all doses) significantly reduced tactile-allodynia and mechano-hyperalgesia (p < .05) while Dic did not. On the 9th day, the ipsilateral nerve IL-6 levels were significantly decreased (p < .05) in the PG and DIC groups compared to the Sal group. IL-1β levels demonstrated a significant reduction (p < .05) in the PG group when compared to saline. These results suggest that PG but not Dic may be effective in reducing neuropathic orofacial pain. The mechanisms of action may be associated to some extent with reduction in IL-1β levels in the affected nerve.

Oxytocin is implicated in social memory deficits induced by early sensory deprivation in mice

Early-life sensory input plays a crucial role in brain development. Although deprivation of orofacial sensory input at perinatal stages disrupts the establishment of the barrel cortex and relevant callosal connections, its long-term effect on adult behavior remains elusive. In this study, we investigated the behavioral phenotypes in adult mice with unilateral transection of the infraorbital nerve (ION) at postnatal day 3 (P3). Although ION-transected mice had normal locomotor activity, motor coordination, olfaction, anxiety-like behaviors, novel object memory, preference for social novelty and sociability, they presented deficits in social memory and spatial memory compared with control mice. In addition, the social memory deficit was associated with reduced oxytocin (OXT) levels in the hypothalamus and could be partially restored by intranasal administration of OXT. Thus, early sensory deprivation does result in behavioral alterations in mice, some of which may be associated with the disruption of oxytocin signaling.

Long-term sensory disturbances after orbitozygomatic fractures

BACKGROUND

Orbitozygomatic fractures often lead to infraorbital nerve (ION) injury, and affected sensibility is a common long-term complaint within this patient group. We present a long-term follow-up study where the validated von Frey filament system was used for testing ION sensibility. Furthermore, we examined the incidence of persistent nerve injury and whether more complex fractures led to more pronounced ION sensibility disturbances.

METHODS

Patients treated for facial fractures involving the orbitozygomatic complex were included and the follow-up time was 3 years or more. Depending on the location and severity of the fractures, the patients were divided into 4 groups. The patients answered a questionnaire before ION sensibility testing with von Frey filaments.

RESULTS

Eighty-one patients were examined: 65 males (80%) and 16 females (20%). Examinations were conducted between 3.0 and 7.6 years (mean 4.9 years) after injury. Sixteen patients (20%) had affected and 6 patients (7.4%) had severely affected ION sensibility according to von Frey testing. No statistically significant differences were found in terms of questionnaire score between the groups. There was also no statistically significant correlation between questionnaire results and log von Frey values. Although the effect of groups could not be statistically verified using the log von Frey values, a larger proportion of patients with complex fractures had higher log von Frey values than the other groups.

CONCLUSIONS

Patients with complex fractures report more permanent sensory disturbance of the ION after surgery than those with isolated orbitozygomatic fractures, although this could not be verified statistically with von Frey filament testing at several locations. Hence, a validated method for testing facial sensibility such as von Frey filaments, although sensitive, is inadequate to determine all aspects of sensory malfunction after orbitozygomatic fractures. This suggests that the patient's experience of long-term sensation after trauma may not be correlated with objective measures.

How Far Have We Come in the Field of Nerve Regeneration After Trigeminal Nerve Injury?

Patients suffering from nerve injury with sensory disturbances or orofacial pain have greatly reduced quality of life, and it is a big cost for the society. Abnormal sensations caused by trigeminal nerve injury often become chronic, severely debilitating, and extremely difficult to treat. In general, non-invasive treatment such as drug treatment has been insufficient, and there are currently few available effective treatments. Surgical interventions such as end-to-end connection or nerve grafting have disadvantages such as donor site morbidity or formation of neuroma. There is need for optimizing the technique for nerve repair, especially for the trigeminal nerve system, which has so far not yet been well explored. Recently, tissue engineering using biodegradable synthetic material and cell-based therapies represents a promising approach to nerve repair and it has been reported that mesenchymal stem cell (MSC) has an anti-inflammatory effect and seems to play an important role in nerve healing and regeneration.

Location of the infraorbital foramen with reference to soft tissue landmarks

PURPOSE

The location of the infraorbital foramen and its variations are important during periorbital, dental, plastic, and oromaxillofacial surgeries. The aim of this study is to document the most practical anatomical soft tissue landmarks for defining the location of infraorbital foramen and infraorbital nerve for effective nerve blockade and to decrease its risk of injury during periorbital surgeries.

METHODS

Forty sides from 20 adult fixed cadavers were used for this study. The position of the infraorbital nerve was determined in reference to the lateral edge of the ala of the nose, medial and lateral palpebral commissures. All these three soft tissue landmarks were then connected to each other forming a triangular shaped region.

RESULTS

In 75 % of the cases the infraorbital foramen was located on the line which is connecting the lateral palpebral commissure to the ala of the nose. The closest distance of infraorbital foramen to the inferior orbital margin and to facial midline was also measured. The infraorbital foramen was located outside the previously defined triangular region in 20 % and inside the triangle in 5 %. The closest mean distance between the infraorbital foramen and the infraorbital margin was measured as 8.8 ± 1.0 mm and the distance between the medial wall of the infraorbital foramen and the facial midline was measured as 30.3 ± 2.7 mm.

CONCLUSION

The triangular region and the soft tissue landmarks we offered in this study may facilitate prediction of the locations of the infraorbital foramen thus, the infraorbital nerve.

Neonatal sensory nerve injury-induced synaptic plasticity in the trigeminal principal sensory nucleus

Sensory deprivation studies in neonatal mammals, such as monocular eye closure, whisker trimming, and chemical blockade of the olfactory epithelium have revealed the importance of sensory inputs in brain wiring during distinct critical periods. But very few studies have paid attention to the effects of neonatal peripheral sensory nerve damage on synaptic wiring of the central nervous system (CNS) circuits. Peripheral somatosensory nerves differ from other special sensory afferents in that they are more prone to crush or severance because of their locations in the body. Unlike the visual and auditory afferents, these nerves show regenerative capabilities after damage. Uniquely, damage to a somatosensory peripheral nerve does not only block activity incoming from the sensory receptors but also mediates injury-induced neuro- and glial chemical signals to the brain through the uninjured central axons of the primary sensory neurons. These chemical signals can have both far more and longer lasting effects than sensory blockade alone. Here we review studies which focus on the consequences of neonatal peripheral sensory nerve damage in the principal sensory nucleus of the brainstem trigeminal complex.

Perineural Spread in Squamous Cell Carcinoma of the Face: An Overlooked Facet of Information on Imaging

A case of malignant cutaneous lesion of the face diagnosed initially as sebaceous carcinoma, subsequently proven to be squamous cell carcinoma is presented. Patient was initially evaluated at an outside institution by computed tomography, which indicated extension of lesion to the maxillary sinus. Patient underwent local resection. Further imaging by magnetic resonance imaging was done for recurrent tumour. Examination revealed extensive, large volume, perineural extension of the disease via infraorbital nerve to the cavernous sinus. Patient was managed with extensive lesion resection, including the skull base component followed up by radiation. Patient showed recurrence despite aggressive management. This case highlights the crucial role of performing an optimal MR imaging of the target region, including skull base, to exclude a perineural extension, as part of assessment of oro-facial malignancy.

Infraorbital canal bilaterally replaced by a lateroantral canal

The infraorbital canal (IOC) normally courses above the maxillary sinus in the orbit floor. During a retrospective study of cone beam computed tomography (CBCT) scans, we found a previously unknown variant of the IOC. The IOCs were absent, being replaced by lateroantral canals coursing around and not above the maxillary sinus to open at infraorbital foramina which were located above the second upper premolar teeth. On coronal multiplanar reconstructions, the lateroantral canals were located anatomically at the outer limit of the zygomatic recess of each maxillary sinus, while the upper wall of the sinus was devoid of any canal. Such rare variant should be kept in mind by dental practitioners and surgeons, as it can determine modifications of common procedures. In this regard, the anatomy of maxilla, as well as mandible, should be evaluated in CBCT on a case-by-case basis.

Surgical anatomy and variations of the infraorbital nerve

OBJECTIVES/HYPOTHESIS

To assess relevant variations in the anatomical course of the infraorbital nerve (ION). This understanding may reduce the risk of surgical injury.

METHODS

A total of 100 consecutive computed-tomography sinus studies obtained in a tertiary referral center were reviewed, and measurements were made of the 200 IONs. Anatomic variants were classified into three types based on the degree to which (if any) the nerve's course descended from the maxillary roof into the sinus lumen.

RESULTS

A total of 60.5% of IONs were entirely contained within the sinus roof. In 27.0%, the nerve canal descended below the roof but remained juxtaposed to it. In 12.5%, the ION descended into the sinus lumen. The proportion of IONs descending into the sinus significantly increased to 27.7% when an infraorbital ethmoid cell was present (chi-square P < 0.001) and to 50% when the nerve was contained within a lamella of such a cell (chi-square P < 0.001). Descended nerves terminated in a foramen located an average of 11.9 ± 2.5 mm below the infraorbital rim, significantly further below the orbit than nondescended nerves (t test P < 0.001). Descended nerves were located a mean distance of 8.6 ± 2.9 mm below the sinus roof and traversed the sinus lumen diagonally for a mean length of 15.4 ± 3.1 mm.

CONCLUSIONS

Descent of the ION into the maxillary sinus is a common anatomic variant that is more prevalent in the setting of an ipsilateral infraorbital ethmoid cell. Descended nerves are associated with the foramen significantly further below the inferior orbital rim than those of nondescended nerves. These observations may help surgeons avoid iatrogenic ION injury.

LEVEL OF EVIDENCE

N/A.

[Malignant peripheral nerve sheath tumour of the infra-orbital nerve]

A malignant peripheral nerve sheath tumour (MPNST) is an uncommon neoplasm that rarely involves the head and neck region. It is even more infrequent for these tumours to affect cranial nerves. We report the case of a 53-year-old man who presented a MPNST involving the infra-orbital nerve, which extended through the orbit and the base of the skull, progressing intracranially. Histological studies identified the tumour as an MPNST. Response to radiotherapy was not complete and radical surgical resection was impossible, so the patient died 10months later. This rare case of MPNST with intracranial involvement illustrates the dismal prognosis for patients with these lesions. Prognosis is poor because of the difficulty of performing radical surgery with free margins in these locations.

The gap junction blocker carbenoxolone attenuates nociceptive behavior and medullary dorsal horn central sensitization induced by partial infraorbital nerve transection in rats

Glial cells are being increasingly implicated in mechanisms underlying pathological pain, and recent studies suggest glial gap junctions involving astrocytes may contribute. The aim of this study was to examine the effect of a gap junction blocker, carbenoxolone (CBX), on medullary dorsal horn (MDH) nociceptive neuronal properties and facial mechanical nociceptive behavior in a rat trigeminal neuropathic pain model involving partial transection of the infraorbital nerve (p-IONX). p-IONX produced facial mechanical hypersensitivity reflected in significantly reduced head withdrawal thresholds that lasted for more than 3weeks. p-IONX also produced central sensitization in MDH nociceptive neurons that was reflected in significantly increased receptive field size, reduction of mechanical activation threshold, and increases in noxious stimulation-evoked responses. Intrathecal CBX treatment significantly attenuated the p-IONX-induced mechanical hypersensitivity and the MDH central sensitization parameters, compared to intrathecal vehicle treatment. These results provide the first documentation that gap junctions may be critically involved in orofacial neuropathic pain mechanisms.

Evaluation of Neurosensory Changes in the Infraorbital Nerve following Zygomatic Fractures

PURPOSE

To evaluate the incidence and recovery of persistent sensory disturbances of the infraorbital (IO) nerve after isolated zygomatic complex fractures with various treatment methods.

METHODS AND RESULTS

The study was inclusive of isolated unilateral zygomatic complex fractures and fractures of IO rim .Tests performed were Pin prick and Electrical detection threshold test. The evaluation was done preoperatively, after 1 month and after 6 months of surgery. The results suggested that neurosensory disturbance was present in all the patients with zygomatic complex fractures. At 1 month post-operatively some sensory deficit was present in all the patients on the affected side. After 6 months all the patients showed near to normal improvement comparable to normal side.

CONCLUSION

Study shows that earlier the surgical intervention, more the recovery of the nerve injury is appreciable during the 1 and 6  months follow up period.

Giant tumour of the pterygopalatine fossa

Neurilemmomas are benign and slow growing tumours. Neurilemmomas of the pterygopalatine fossa are rare. In this paper we present a case of schwannoma arising in the pterygopalatine fossa with extension into infratemporal fossa and floor of the orbit. A transantral approach was used for excision of the tumor following which the defect in the floor of the orbit was reconstructed with the help of a temporoparietal flap.