Anterior Ethmoidal Nerve Research Articles

A PROSPECTIVE STUDY OF ASSOCIATION OF ANTERIOR ETHMOIDAL NERVE SYNDROME (SLUDER'S NEURALGIA) WITH NASAL SEPTAL SPUR AND ITS MANAGEMENT

Background: Anterior ethmoidal nerve syndrome is headache resulting from irritation of the terminal branches of the anterior ethmoidal nerve. The headache arises when the septal spur compresses against the middle turbinate or the lateral nasal wall. Here we studied the association of anterior ethmoidal nerve syndrome (Sluder's neuralgia) with nasal septal spur and its management. Methods: A prospective observational study carried out on 31 patients who fullled the clinical diagnostic criteria. Results: The patients were treated surgically. The outcomes of surgical treatment were quite promising with 29 patients reporting in improvement in pain after surgery out of the 31 surgeries performed. Conclusion: The diagnosis requires a strong clinical suspicion and appropriate evaluation including nasal endoscopy, scan and anaesthesia of the suspected point of contact.

Anterior Ethmoidal Nerve Syndrome - An Under-diagnosed Cause of Headache

Introduction The anterior ethmoidal nerve syndrome is a group of symptoms resulting from irritation of the terminal branches of the anterior ethmoidal nerve. Middle turbinate compression against the septum or the lateral nasal wall may cause a neuropathic facial pain syndrome which is often confused with sinogenic headache or other causes of headache. The diagnosis of anterior ethmoidal nerve syndrome is based on clinical and radiologic findings and needs a high index of suspicion. Our objective is to determine the nasal cause of headache and to create awareness among young ENT surgeons about various local causes of craniofacial pain. Materials and Methods A retrospective observational study carried out in a tertiary care hospital of North India. 30 patients who fulfilled the clinical diagnostic criteria were selected for the study. Results All the patients were analysed, managed accordingly by conservative and surgical management and outcome analysed. All patients were managed with medical and surgical management. Out of 30 patients, 28 (93.33%) patients improved in which 2 patients improve by medical management and 26 patients by surgical management. Conclusion The diagnosis requires a strong clinical suspicion and appropriate evaluation including nasal endoscopy, scan and anesthesia of the suspected point of contact.

Voltage Stimulation of the Anterior Ethmoidal Nerve in Rats Produces a Cardiorespiratory Response Similar to the Diving Response

The diving response, initiated when animals submerge under water, includes a decrease in heart rate, peripheral vasoconstriction, and apnea. Electrical stimulation of the anterior ethmoidal nerve (AEN), the nerve that innervates the nasal passages, can produce similar reflex responses. The purpose of the present research in Sprague‐Dawley rats was to electrically stimulate the AEN using silver coated copper wire and a voltage stimulus supplied through an iWorx TA‐220 Control Module and Labscribe software. Our hypothesis was that increasing the intensity of the AEN electrical stimulation would increase the intensity of the resultant cardiorespiratory responses. Accordingly, we isolated the AEN at the base of the orbit, hooked the electrodes around the nerve, and insulated the nerve and orbit with dental impression material. While recording heart rate, arterial blood pressure and respiration, we varied 5 s of AEN electrical stimulation between 0.1 and 1.1 volts. Stimulation threshold of 0.2 volts would elicit slight bradycardia, slight alterations in BPa, and a slight decrease in respiratory rate. With increasing voltages, the response intensified. When maximally stimulated, HR decreased from 438 ± 28 to 181 ± 37 bpm, and BPa decreased from 127 ± 5 to 121 ± 14 mmHg. The respiratory rate decreased from 93 ± 3 to 0 breaths/min with an apnea duration of 5.0 ± 0.2 s. Our studies found that the intensity of the cardiorespiratory responses and the voltage of the AEN stimulation varied somewhat linearly. This technique and these findings can be used in future research to investigate the brainstem pathways of the mammalian diving response.

Anterior Ethmoidal Nerve Block In Prevention of Post-Operative Agitation Following Nasal Surgeries with Nasal Packs Under General Anesthesia: An Experimental Study

INTRODUCTION
 Postoperative agitation or emergence agitation during recovery from anesthesia is an important complication of General Anesthesia (GA) especially in otolaryngological surgeries, and nasal surgery in particular. It is potentially harmful to the patients resulting in fall from the operation table, self-extubation, self-removal of nasal pack, hemorrhage etc. Several methods and medications have been tried to reduce it. We studied the effect of anterior ethmoidal nerve block for reducing post-operative agitation for nasal surgeries with nasal packs as it falls in the same operative field.
 MATERIAL AND METHODS
 A total of 100 participants undergoing nasal surgeries with nasal pack under GA in the Department of Otolaryngology, Lumbini Medical College, Palpa, Nepal, were randomized into cases and controls by block randomization. The study was done from June 2018 till February 2020. Anterior ethmoidal nerve was blocked with lidocaine injection at the end of surgery in cases. Controls were injected with normal saline. Post-operative agitation was studied with Riker Sedation-Agitation Scale (SAS) and was compared between the two groups.
 RESULTS
 There were 50 participants in each group. Emergence agitation in cases and controls at extubation, 30 minutes post-extubation and the next morning was present in 32% and 52%, 4% and 18%, and 0 and 2% respectively. SAS score rapidly decreased in 30 minutes after extubation in controls but was still significantly higher than that of cases.
 CONCLUSION
 Anterior ethmoidal nerve block was effective in reducing post-operative agitation significantly during emergence in nasal surgeries with nasal packs.

Location of the Ciliary Ganglion within the Orbit

The ciliary ganglion (CG) is a parasympathetic ganglion located in the orbit that controls pupil contraction, accommodation, ocular blood flow, intraocular pressure, and aqueous humor production. Micro and macro‐surgical lesions to the CG can affect nearby structures and lead to Adie’s Tonic Pupil or Argyll Robertson Pupil. This study was performed to better understand the CG location within the orbit. Few studies have analyzed the distance from the CG to neighboring structures with evident variation in the mean distance between the posterior globe (PG) and the CG, which can prove clinically significant in orbital floor surgical procedures. Besides direct clinical impact, this research would be beneficial in medical education by enabling a more accurate depiction of the CG in anatomical illustrations. Lastly, this is a novel study in that it measures the distance in relation to a relatively immobile structure, rather than to a more dynamic and variable neural or vascular structure.MethodsNine cadaver heads were bisected for a total of 18 samples, and two additional bisected half heads were used. The calvaria, brain, cranial fossa dura matter, frontal bone, and lesser wing of sphenoid bone were removed. Once orbital contents were visualized, dissection began by identifying the anterior and posterior ethmoidal nerves that run superior to the upper border of the medial rectus muscle. Blunt dissection was used to trace them back to the nasociliary nerve, an ophthalmic nerve division. The nasociliary nerve sends a sensory root to the CG. The oculomotor nerve (CN III) passes through the common tendinous ring, which was dissected open to allow better visualization of CN III inferior and superior divisions. The inferior division of CN III, which carries parasympathetic contribution to the CG, was dissected. The CG was confirmed by tracing the sensory nasociliary branch and the parasympathetic root from the inferior division of CN III to CG. Once identified, the CG was pinned in the center, in its natural position. The distance from the PG at the optic nerve juncture and the pinned CG was measured three separate times, removing and placing the pin in the center for each measurement. The three measurements average was used. The second measurement was from the posterior clinoid process (PCP) to the pinned ganglion, measured three separate times, and the average was used for each ganglion.ResultsThe average distance range between PG and CG was 8.95 – 24.63 mm, with the average of the 20 mean measurements being 17.853 mm. The average distance range between CG and PCP was 28.23 – 39.58 mm, with the average of the 20 mean measurements being 35.135 mm.ConclusionThe distance from the PG to the CG center was 17.85 mm, and from CG center to PCP was 35.135 mm. This varies from other studies that have reported the distance between the PG and CG to be 12 mm, 2–3 mm, and 15–20 mm. The CG is 2.9 mm lateral to the optic nerve and could be damaged during lateral orbiotomy procedures. In terms of anatomical education, illustrations in Netter and Gray’s differ in the location of the CG. These results support Gray’s proposition that the CG is further posterior relative to the posterior globe rather than being closer to the globe as shown in Netter’s atlas. Ours is a novel study to clarify the position of the CG within the orbit.

Spinal trigeminal subnucleus pars muralis: An interface for apneic reflex

Noxious stimulation of the nasal cavity elicits protective reflexes for the upper respiratory tract, including sneezing, mucus secretion, apnea and cardiovascular reflexes. Yet, no studies have shown the full circuit responsible for the apneic response upon noxious stimulation of the nasal mucosa. Here, we show that injection of cholera toxin beta subunit into the nasal mucosa leads to terminal labeling in the transition zone between the interpolaris and caudalis subnuclei of the trigeminal sensory complex, i.e. subnucleus muralis (SpVm). We also provide physiological evidence that ammonia vapor delivered into the nasal cavity induces an apneic reaction and activates some SpVm cells. Subnucleus muralis cells also respond to mechanical stimulation of the narial pad and the nasal mucosa. Yet, none of the muralis cells responded to vibrissa deflection. Electrolytic lesion of SpVm or unilateral transection of the anterior ethmoidal nerve prevent apnea induced by ammonia delivery to the nasal epithelium, demonstrating their crucial role in the apneic reflex. We also found direct projections from SpVm to the respiratory centers, particularly the preBötzinger complex (preBötC). Inhibition of inspiratory preBötC cells and increased firing of expiratory preBötC cells are associated with ammonia‐induced apnea.Anatomical and physiological data presented here support the hypothesis that nasal induced apnea may be mediated by direct projections from nasal innervated Subnucleus muralis neurons to the PreBötC complex.

An unusual arrangement of the neurovascular structures in one ethmoidal foramen of the human orbit

The anatomical landmarks of the medial orbital wall are vital for orbital surgeries. Understanding of the medial orbital wall, the number, morphology and location of ethmoidal foramina, is important in order to help reduce intraoperative risks. It is also important for proper identification of all anatomical structures during sinus surgery. The reported incidence rate of both minor and major orbital surgical complications varies between 0.5 and 30%. The aim of this study is to report the morphology of a rare variation of the ethmoidal foramen present in the left orbit of one body. Both orbits were studied of which one revealed a rare variation. The eyeballs were exenterated from the orbits with part of the optic nerve, leaving the vascular supply and extraocular muscles intact. A further dissection was performed in both orbits to remove excess orbital tissue for a proper visualisation of the orbital blood supply and their points of exit. Digital photographs were taken and stored on a computer. The arterial system was traced on a computer using Microsoft PowerPoint tools to highlight their route on the medial orbital. Ethical approval was granted for the main study with reference: 469/2018. The medial orbital wall of the left orbit was concluded to have a single ethmoidal foramen. Two blood vessels were identified emerging from this single foramen and one blood vessel entering in an unusual way. The right orbit did not show a similar observation. Few previous studies found a single foramen in orbits, however, there was only one blood vessel that was seen passing through the foramen. Knowledge of the medial orbital wall foramina may serve as a guide to clinicians while treating haemorrhages of ethmoidal vessels and anterior ethmoidal nerve syndrome. In addition, this knowledge will help reduce intraoperative risks and injury to the neurovascular bundle. Further research will be conducted to investigate the frequency of this variation in a South African context.

New landmarks in endonasal surgery: from nasal bone to anterior cribriform plate including branches of anterior ethmoidal artery and nerve and terminal nerve.

Despite the development of anterior skull base surgery, the anatomy of the nasal bone and anterior cribriform plate remains unclear. A recent study confirmed 2 distinct foramina in the anterior part of cribriform plate: the ethmoidal slit (ES) and the cribroethmoidal foramen (CF). The aim of this study was to specify their content, their anatomic relationship to the frontal sinus and skull base, and their potential value in skull base surgery. Dissections were performed on 36 cadaver heads. Macro- and microscopic examinations were carried out. Microcomputed tomography scans contrasted with osmium were performed to identify vessels and nerves. Histology with neural, meningeal, or luteinizing hormone-releasing hormone immunomarkers was performed on the content of the foramina. Finally, endonasal surgical dissections were carried out. The ES and the CF were observed in all cases. They measured a mean of 4.2 and 1.6 mm, respectively. The ES contained dura mater, arachnoid tissues, lymphatics, and the terminal nerve. The CF contained the anterior ethmoidal nerve and artery. This foramen continued forward with the cribroethmoidal groove,which measured a mean of 2.5 mm. This groove was under the frontal sinus and in front of the skull base. We also described a "cribroethmoidal canal" and a "nasal bone foramen." The clinical applications of this new anatomic description concern both cribriform plate and frontal sinus surgeries. Identifying the terminal nerve passing through the ES is a step forward in understanding pheromone recognition in humans.

Neurostimulation for tear production.

Dry eye disease (DED) is a chronic multifactorial disease that affects millions of people worldwide. Despite ongoing research, treatment for DED remains a challenge. Neurostimulation for tear production is a rapidly evolving field that culminated in the development of the intranasal tear neurostimulator (ITN). In this article, we review the neuroanatomy and pathophysiology of tear production and the evolution of neurostimulation for the treatment of DED. The ITN was approved for commercial use in April 2017. This innovation stemmed from the success of lacrimal nerve and anterior ethmoid nerve stimulation animal studies. Since then, numerous pilot studies and multicenter randomized controlled trials demonstrate increased aqueous tear production, improved DED-related symptoms, and device safety. Recent studies also report the positive effects of intranasal stimulation on mucin and lipid secretion. Neurostimulation for enhanced tear production is a promising new treatment option for DED. Stimulation of the lacrimal nerve and anterior ethmoid nerve both effectively increase tear volume. The ITN is a noninvasive device that effectively increases aqueous tear volume and may improve tear composition, including mucin and lipid concentrations. Further studies are needed to determine proper patient selection and the long-term efficacy of neurostimulation for DED.

Chronic Electrical Stimulation for Tear Secretion: Lacrimal vs. anterior ethmoid nerve

PurposeTo evaluate and compare the effect of lacrimal nerve stimulation (LNS) and anterior ethmoid nerve stimulation (AENS) on aqueous tear secretion, and tissue condition following chronic implantation. MethodsA neurostimulator was implanted in rabbits adjacent to the (1) lacrimal nerve, and (2) anterior ethmoid nerve. Tear volume was measured with Schirmer test strips after stimulation (2.3–2.8 mA pulses at 30 Hz for 3–5 min), and scores were compared to sham stimulation. Lacrimal gland and nasal septal tissue were evaluated histologically after chronic stimulation (2 weeks–7 months). ResultsLNS increases tear volume by 32% above sham (p < 0.05, n = 5), compared with 133% for AENS (p ≤ 0.01, n = 6). AENS also significantly increases tear secretion in the fellow, non-stimulated eye (p ≤ 0.01, n = 6), as expected from the tearing reflex pathway. Histologically, chronic LNS is well tolerated by surrounding tissues while chronic AENS results in nasal mucosal fibrosis and implant extrusion within 3 weeks. ConclusionsAENS is significantly more effective than LNS at enhancing aqueous tear secretion, including the fellow eye. The lacrimal implant is well tolerated, while the nasal implant requires further design optimization to improve tolerability.

Central Terminals of Trigeminal Nerves that Innervate the Nose and Nasal Passages Colocalize with Medullary Dorsal Horn Neurons Activated during Voluntary Diving in Rats

Underwater submersion in mammals initiates the diving response, an autonomic cardiorespiratory reflex that includes apnea, a parasympathetically‐mediated bradycardia, and a sympathetically‐mediated increase in total peripheral resistance. The initial synapse of this reflex occurs within the ventral medullary dorsal horn (MDH) of the spinal trigeminal nucleus caudalis. The anterior ethmoidal and nasopalatine nerves, trigeminal nerves that innervate the internal nasal passages, also send their central terminations to the ventral MDH. The objective of this research was to detect colocalization of secondary MDH neurons activated by voluntary diving with the central terminations of the trigeminal nerves innervating the internal nasal passages. MDH activated neurons were identified by Fos protein production, while central terminals of the trigeminal nerves were located by the transganglionic tracer Wheat Germ Agglutinin (WGA). Sprague‐Dawley rats (N=12) were trained to voluntarily dive through a 5 m underwater Plexiglas maze. After training, 6 rats then received WGA injections into the anterior ethmoidal nerve, while 6 rats received WGA injections into the nasopalatine nerve. Four days post‐WGA injection, 3 rats from each nerve injection group performed 12 dive trials over 1 hour to activate brainstem neurons and initiate Fos production; 3 rats from each nerve injection group were non‐diving controls. Brainstem tissue from all rats was immunohistochemically processed to visualize both Fos and WGA, and was inspected using a Nikon C1 confocal microscope and Nikon Eclipse Ti2 inverted fluorescent microscope. Results indicate repetitive voluntary diving increases the number of Fos‐positive neurons within the ventral tip of the superficial MDH and adjacent paratrigeminal nucleus. WGA results show central termination sites from both the anterior ethmoidal and nasopalatine nerves within this same MDH location. Additionally, MDH Fos‐positive neurons from diving animals show extensive colocalization with WGA injected into both the anterior ethmoidal nerve and nasopalatine nerve compared to non‐diving control rats. We conclude both the anterior ethmoidal and nasopalatine nerves can provide afferent information necessary to activate MDH neurons during initiation of the mammalian diving response.Support or Funding InformationSupported by MWU Intramural funding (PFM) and CGS MBS program (MM)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Nervus terminalis and nerves to the vomeronasal organ: a study using human fetal specimens.

The human nervus terminalis (terminal nerve) and the nerves to the vomeronasal organ (VNON) are both associated with the olfactory nerves and are of major interest to embryologists. However, there is still limited knowledge on their topographical anatomy in the nasal septum and on the number and distribution of ganglion cells along and near the cribriform plate of the ethmoid bone. We observed serial or semiserial sections of 30 fetuses at 7–18 weeks (crown rump length [CRL], 25–160 mm). Calretinin and S100 protein staining demonstrated not only the terminal nerve along the anterior edge of the perpendicular lamina of the ethmoid, but also the VNON along the posterior edge of the lamina. The terminal nerve was composed of 1–2 nerve bundles that passed through the anterior end of the cribriform plate, whereas the VNON consisted of 2–3 bundles behind the olfactory nerves. The terminal nerve ran along and crossed the posterior side of the nasal branch of the anterior ethmoidal nerve. Multiple clusters of small ganglion cells were found on the lateral surfaces of the ethmoid's crista galli, which are likely the origin of both the terminal nerve and VNON. The ganglions along the crista galli were ball-like and 15–20 µm in diameter and, ranged from 40–153 in unilateral number according to our counting at 21-µm-interval except for one specimen (480 neurons; CRL, 137 mm). An effect of nerve degeneration with increasing age seemed to be masked by a remarkable individual difference.

Innervation of the Nose and Nasal Region of the Rat: Implications for Initiating the Mammalian Diving Response.

Most terrestrial animals demonstrate an autonomic reflex that facilitates survival during prolonged submersion under water. This diving response is characterized by bradycardia, apnea and selective increases in peripheral vascular resistance. Stimulation of the nose and nasal passages is thought to be primarily responsible for providing the sensory afferent signals initiating this protective reflex. Consequently, the primary objective of this research was to determine the central terminal projections of nerves innervating the external nose, nasal vestibule and nasal passages of rats. We injected wheat germ agglutinin (WGA) into specific external nasal locations, into the internal nasal passages of rats both with and without intact anterior ethmoidal nerves (AENs), and directly into trigeminal nerves innervating the nose and nasal region. The central terminations of these projections within the medulla were then precisely mapped. Results indicate that the internal nasal branch of the AEN and the nasopalatine nerve, but not the infraorbital nerve (ION), provide primary innervation of the internal nasal passages. The results also suggest afferent fibers from the internal nasal passages, but not external nasal region, project to the medullary dorsal horn (MDH) in an appropriate anatomical way to cause the activation of secondary neurons within the ventral MDH that express Fos protein during diving. We conclude that innervation of the anterior nasal passages by the AEN and nasopalatine nerve is likely to provide the afferent information responsible for the activation of secondary neurons within MDH during voluntary diving in rats.

Restoration of the nasopharyngeal response after bilateral sectioning of the anterior ethmoidal nerve in the rat.

In response to stimulation of the nasal passages with volatile ammonia vapors, the nasopharyngeal reflex produces parasympathetically mediated bradycardia, sympathetically mediated increased peripheral vascular tone, and apnea. The anterior ethmoidal nerve (AEN), which innervates the anterior nasal mucosa, is thought to be primarily responsible for providing the sensory afferent signals that initiate these protective reflexes, as bilateral sectioning causes an attenuation of this response. However, recent evidence has shown cardiovascular responses to nasal stimulation with ammonia vapors are fully intact 9 days after bilateral AEN sectioning, and are similar to control animals without bilaterally sectioned AENs. To investigate this restoration of the nasopharyngeal response, we recorded the cardiorespiratory responses to nasal stimulation with ammonia vapors immediately after, and 3 and 9 days after, bilateral AEN sectioning. We also processed brainstem tissue for Fos to determine how the restoration of the nasopharyngeal response would affect the activity of neurons in the medullary dorsal horn (MDH), the part of the ventral spinal trigeminal nucleus caudalis region that receives primary afferent signals from the nose and nasal passages. We found 3 days after bilateral AEN sectioning the cardiorespiratory responses to nasal stimulation are partially restored. The bradycardic response to nasal stimulation is significantly more intense 3 days after AEN sectioning compared to Acute AEN sectioning. Surprisingly, 3 days after AEN sectioning the number of Fos‐positive neurons within MDH decreased, even though the cardiorespiratory responses to nasal stimulation intensified. Collectively these findings indicate that, besides the AEN, there are alternate sensory pathways that can activate neurons within the trigeminal nucleus in response to nasal stimulation. The findings further suggest trigeminal neuronal plasticity involving these alternate sensory pathways occurs in as few as 3 days after bilateral AEN sectioning. Finally, activation of even a significantly reduced number of MDH neurons is sufficient to initiate the nasopharyngeal response.

Enhanced Tearing by Electrical Stimulation of the Anterior Ethmoid Nerve.

PurposeElectrical neurostimulation enhances tear secretion, and can be applied to treatment of dry eye disease. Using a chronic implant, we evaluate the effects of stimulating the anterior ethmoid nerve on the aqueous, lipid, and protein content of secreted tears.MethodsNeurostimulators were implanted beneath the nasal mucosa in 13 New Zealand white rabbits. Stimulations (2.3–2.8 mA pulses of 75–875 μs in duration repeated at 30–100 Hz for 3 minutes) were performed daily, for 3 weeks to measure changes in tear volume (Schirmer test), osmolarity (TearLab osmometer), lipid (Oil-Red-O staining), and protein (BCA assay, mass spectrometry).ResultsStimulation of the anterior ethmoid nerve in the frequency range of 30 to 90 Hz increased tear volume by 92% to 133% (P ≤ 0.01). Modulating the treatment with 50% duty cycle (3 seconds of stimulation repeated every 6 seconds) increased tear secretion an additional 23% above continuous stimulation (P ≤ 0.01). Tear secretion returned to baseline levels within 7 minutes after stimulation ended. Tear film osmolarity decreased by 7 mOsmol/L, tear lipid increased by 24% to 36% and protein concentration increased by 48% (P ≤ 0.05). Relative abundance of the lacrimal gland proteins remained the same, while several serum and corneal proteins decreased with stimulation (P ≤ 0.05).ConclusionsElectrical stimulation of the anterior ethmoid nerve increased aqueous tear volume, reduced tear osmolarity, added lipid, and increased the concentration of normal tear proteins. Human studies with an intranasal stimulator should verify these effects in patients with aqueous- and lipid-deficient forms of dry eye disease.

Do Trigeminal Nerves that Innervate the Nose and External Nares Project to Medullary Dorsal Horn Locations Activated during Voluntary Diving in Rats?

Underwater diving initiates the diving response, an autonomic cardiorespiratory reflex that includes parasympathetically‐mediated bradycardia, a sympathetically‐mediated increase in total peripheral resistance, and apnea. The initial afferent node of the reflex circuitry includes the ventral tip of the medullary dorsal horn (MDH), between the pyramidal decussation and obex. This region is also the location of the central terminations of trigeminal nerves that innervate the nose and external nares. Accordingly, the objective of this research was to compare the pattern of neuronal activation of secondary neurons activated by voluntary diving, as determined by neuronal Fos production, with the central terminations of specific trigeminal nerves that innervate the nose and external nares, as determined by the transganglionic tracer Wheat Germ Agglutinin (WGA). Sprague‐Dawley rats (N=12) were trained to voluntarily dive through a 5 m underwater maze. Six rats then received bilateral AEN sectioning, while 6 rats received sham surgery. Nine days post‐surgery all rats had 24 dive trials over 2 hours to activate brainstem neurons to produce Fos. Other rats had 1 μl of 100% WGA injected into the anterior ethmoidal nerve (AEN; N=4), the main orbital branch of the infraorbital nerve (ION; N=7), terminal branches of the ION that innervate the nasal region (N=9), or supratrochlear nerve (N=8). Results indicate Fos was primarily located within the ventral tip of the superficial MDH and adjacent paratrigeminal nucleus, between the pyramidal decussation caudally and the obex rostrally. The Fos labeling was heaviest when the area postrema was present, especially when Spinal Trigeminal Nucleus Interpolaris displaces the ventral MDH medially. This pattern of Fos labeling within the MDH was similar in rats both with and without intact AENs. Within the MDH WGA central termination sites showed varying degrees of overlap with the location of Fos‐positive neurons. The AEN WGA labeling had the best overlap with Fos‐positive neurons. The main orbital branch of the ION had extensive WGA labeling throughout the MDH, both ventrally and dorsally, and did partially overlap the MDH Fos labeling. The WGA labeling from both nasal branches of the ION and supratrochlear nerve were located more caudally within the MDH near the pyramidal decussation, thus showing poor overlap with the Fos labeling. We conclude that the AEN, and possibly the ION, provides the anatomical pathway that provides the afferent information necessary to initiate the mammalian diving response. However, in the absence of the AEN, it is not clear whether the ION can actually provide this afferent information.Support or Funding InformationSupported by MWU Intramural funding (PFM), CCOM Suarez Summer Research Fellowships (BDP and KAL), and CHS MBS program (EAW).

Repetitive Diving in Trained Rats Still Increases Fos Production in Brainstem Neurons after Bilateral Sectioning of the Anterior Ethmoidal Nerve.

This research was designed to investigate the role of the anterior ethmoidal nerve (AEN) during repetitive trained diving in rats, with specific attention to activation of afferent and efferent brainstem nuclei that are part of this reflexive response. The AEN innervates the nose and nasal passages and is thought to be an important component of the afferent limb of the diving response. Male Sprague-Dawley rats (N = 24) were trained to swim and dive through a 5 m underwater maze. Some rats (N = 12) had bilateral sectioning of the AEN, others a Sham surgery (N = 12). Twelve rats (6 AEN cut and 6 Sham) had 24 post-surgical dive trials over 2 h to activate brainstem neurons to produce Fos, a neuronal activation marker. Remaining rats were non-diving controls. Diving animals had significantly more Fos-positive neurons than non-diving animals in the caudal pressor area, ventral medullary dorsal horn, ventral paratrigeminal nucleus, nucleus tractus solitarius, rostral ventrolateral medulla, Raphe nuclei, A5, Locus Coeruleus, and Kölliker-Fuse area. There were no significant differences in brainstem Fos labeling in rats diving with and without intact AENs. Thus, the AENs are not required for initiation of the diving response. Other nerve(s) that innervate the nose and nasal passages, and/or suprabulbar activation of brainstem neurons, may be responsible for the pattern of neuronal activation observed during repetitive trained diving in rats. These results help define the central neuronal circuitry of the mammalian diving response.

Transorbital endoscopic identification of supernumerary ethmoid arteries.

Background:Anterior and posterior ethmoid arteries supply the paranasal sinuses, septum, and lateral nasal wall. Precise identification of these arteries is important during anterior skull base procedures, endoscopic sinus surgery, and ligation of ethmoid arteries for epistaxis refractory to standard treatment. There is controversy in the literature regarding the prevalence of supernumerary ethmoid arteries.Objective:This study examined the prevalence of supernumerary ethmoid arteries by using direct visualization after transorbital endoscopic dissection.Methods:Nineteen cadaveric specimens were evaluated by using a superior lid crease (blepharoplasty) incision and an endoscopic approach to the medial orbital wall. Ethmoid arteries were identified as they pierced the lamina papyracea coplanar with the skull base and optic nerve. The distances from the anterior lacrimal crest to the ethmoid arteries and optic nerve were measured with a surgical ruler under endoscopic guidance.Results:Thirty-eight cadaveric orbits were measured. Overall, there were three or more ethmoid arteries (including anterior and posterior arteries) in 58% of orbits, with 8% of the total sample that contained four or more ethmoid arteries. The average number of ethmoid arteries was 2.7. Bilateral supernumerary ethmoid arteries were noted in 42% of the specimens. The distance between the anterior lacrimal crest and the anterior ethmoid, posterior ethmoid, and optic nerve averaged 20, 35, and 41 mm, respectively. The average distance to the supernumerary or middle ethmoid artery was 29 mm.Conclusion:This study found supernumerary ethmoid arteries in 58% of cadaveric specimens, a prevalence much higher than previously reported. Recognition of these additional vessels may improve safety during endoscopic sinus surgery and skull base surgery, and may permit more effective ligation for refractory epistaxis originating from the ethmoid system.

Schwannomas from Olfactory Nerve: A Rare Type.

Dear Editor, I have read with curiosity the article entitled BA large extra cranial cystic trigeminal schwannoma of the parapharyngeal space – exploring the right approach^ published in the Indian Journal of Surgical Oncology [1]. Krishnamurthy and his colleagues skillfully reported a 41 year old male with extracranial cystic schwannoma in the parapharyngeal space. This case-report is a helpful article for showing the rare type of the trigeminal schwannomas. The authors indicated that schwannomas may originate from cranial, autonomic or peripheral nerve with the exception of the olfactory nerve. However, I would like offer the authors that 48 cases with olfactory schwannoma have been reported in the world literature until date. Here I provide comments about olfactory schwannoma on different points. The occurrence of schwannoma is approximately 8 % of all intracranial tumors and usually arise from any nerve containing Schwann cell layer of the vestibular portion of the eight cranial nerve and less commonly from the fifth nerve and lower cranial nerves. Nevertheless, olfactory nerve is not prone to schwannoma due to the lack of Schwann cell layer. On the other hand, anterior cranial fossa schwannoma are exceedingly rare lesion among several locations of schwannoma [2]. In this regard, several theories have been put forth about how anterior cranial fossa schwannoma occurs. The developmental hypotheses advocate these tumors primarily origin from aberrant Schwann cells within the central nervous system or arise from multipotential mesenchymal pial cells and transformation of neural crest cells into the brain parenchyma. On the other hand, non-developmental theories advocate that anterior cranial fossa schwannomas origin from Schwann cells normally represent in the anterior ethmoidal nerve, meningeal branches of the trigeminal nerve, perivascular nerve plexus, and olfactory groove. Moreover, reactive change after injury, for example, Schwann cell formation from multipotential mesenchymal cells in pateints with pathological changes like infarction or multiple sclerosis has been described [3, 4]. On the other hand, neural structures in the cribiform plate and olfactory groove include anterior ethmoidal nerves, branches of trigeminal nerve, nerve plexus of dural vessels, fila olfactoria, and olfactory nerve and bulb. Thus, they represent the possible origin of this subset of schwannomas. And, it has been suggested that olfactory schwannomas arise from the olfactory nerve and bulb [5]. As is obvious from above discussion, olfactory schwannomas are very rare tumors with 48 cases described so far [6]. Hence, their infrequency may partially represent that they have been underreported, overlooked, or misdiagnosed.

Activation of Brainstem Neurons in Voluntarily Diving Rats after Bilateral Sectioning of the Anterior Ethmoidal Nerve

This project was designed to investigate the functional role of the anterior ethmoidal nerve (AEN) during underwater diving in rats. The AEN innervates the nasal passages and is thought to be an important component of the afferent pathway that initiates the mammalian diving response. However recent evidence suggests that other nerves that innervate the nasal passages are also able to provide an afferent signal sufficient to initiate the autonomic responses to diving. To study this and the role of the AEN, 24 male Sprague‐Dawley rats were trained to swim and dive through a 5m underwater maze. Rats were subjected to either bilateral sectioning of the AENs (N=12) or a sham surgery (N=12). Twelve rats (6 surgical and 6 sham) had 24 post‐surgical dive trials over 2 hours to activate brainstem neurons to produce Fos, a neuronal activation marker. Twelve rats (6 surgical and 6 sham) were non‐diving controls. Brainstem tissues from all animals were immunohistochemically processed and analyzed for Fos and compared between the 4 groups. Brain regions inspected included the medullary dorsal horn, nucleus tractus solitarius, ventrolateral medulla, A5, and parabrachial region. This study further elucidates the afferent pathway(s) of the diving response and helps clarify the central integrative pathways involved in the mammalian diving response.