Posterior Auricular Nerve Research Articles

The Anatomical Specificity Between Acupoints and the Facial Nerve: A Cadaveric Study.

This research was conducted to increase precision of point location and standardize acupoint targets in relation to the facial nerve (CN VII). A literature review, cadaver dissection, and electrostimulation of the CN VII were performed, focusing on the anatomical locations of the acupoints along the facial-nerve trajectory. The results were contrasted against established acupoint locations described in the 4th edition of Chinese Acupuncture and Moxibustion. Triple Energizer (TE)-17 targets the facial nerve at its cranial exit; Qian Zheng at the facial nerve trunk; Tai Yang at the frontotemporal branch; Gallbladder (GB)-3 at the zygomatic branch; Small Intestine (SI)-18 at the buccal branch; Stomach (ST)-5 at the marginal mandibular branch; SI-17 at the cervical branch; TE-18 at the posterior auricular branch; TE-19 at the posterior auricular nerve; TE-20 at the superior auricular nerve; and TE-22 at the anterior auricular nerve. This study demonstrated the specificity with which acupuncture points are located in relation to the facial nerve. Standardization of facial acupuncture points to distinct branches of the facial nerve will facilitate reproducible research designs and interpractitioner reproducibility.

Axonal Regeneration Through Autologous Grafts: Does the Axonal Load Influence Regeneration?

IntroductionTwo-stage free functional muscle transfers for long-standing facial palsy can yield unpredictable results. Earlier studies have demonstrated incomplete regeneration across neurorrhaphies in native nerve and higher donor axonal counts correlating with improved outcomes but axonal count in nerve grafts have not been as thoroughly reviewed. To investigate the impact of varying axonal counts in autologous grafts on functional outcomes of repair. Materials and methodsAnimals were allocated into three groups: Direct Nerve Repair (DNR, n = 50), Small Nerve Graft (SNG, n = 50), and Large Nerve Graft (LNG, n = 50). All grafts were inset into the Posterior Auricular Nerve with ear movement recovery (EMR) monitored as functional outcome. At various postoperative weeks (POWs), excised specimens were imaged with electron microscopy. Axonal counts were measured proximal to, distal (DAC) to, and within grafts. Total Success Ratio (TSR) was calculated. ResultsIn DNR, DAC was significantly lower than proximal axonal counts at all POWs, with maximum TSR of 80%. TSR for LNG and SNG were significantly lower at all POWs when compared to DNR, with maximums of 56% and 38%, respectively. LNG had a significantly larger DAC than SNG at POW12 and beyond. A direct relationship was present between DAC and EMR for all values. ConclusionsHigher native axonal count of autologous nerve grafts resulted in higher percentage of regeneration across neurorrhaphies.

POSTERIOR AURICULAR NERVE – A NOVEL LANDMARK FOR IDENTIFICATION OF THE FACIAL NERVE IN SUPERFICIAL PAROTIDECTOMY

ABSTRACT Background-Facial nerve identification and preservation is the most critical step in parotid surgery. Though there are described landmarks to locate the facial nerve trunk, they have individual variations. The posterior auricular nerve (PAN) is a branch of the facial nerve and is always present, it can be followed to reach the facial nerve trunk. MATERIALS AND METHODS A retrospective cohort study in which analysis of parotidectomy performed from January 2017 to November 2018 at our tertiary referral center was done. RESULTS A total of 23 parotidectomies were performed, of which 18 cases were pleomorphic adenoma. In four cases of pleomorphic adenoma we could clearly identify and preserve the PAN. Using PAN as the landmark the facial nerve trunk was located, all its peripheral branches were dissected and preserved. PAN identification narrows down the target area of dissection to identify the facial nerve trunk. CONCLUSION The posterior auricular branch of the facial nerve can be used as a standard landmark in parotid surgeries, that almost always leads to the facial nerve trunk. CLINICAL SIGNIFICANCE Though identification of PAN may be difficult in all cases, effort must be made to identify it under magnification. If done meticulously PAN can be an ideal landmark to identify facial nerve in parotid surgery. KEYWORDS Parotid surgery, Superficial Parotidectomy, Posterior auricular nerve, Facial nerve.

A supportive donor nerve for long-term facial paralysis: Anatomical analysis of the posterior auricular nerve and micro-anatomical comparison with zygomatic nerve

The posterior auricular nerve (PAN) is an inspiring candidate for the additional axonal source in long-term facial paralysis to improve the functional results of the cross-facial nerve (FN) graft technique. However, no studies have analyzed the PAN's axonal load and its microscopic anatomy to assess its utilization in facial reanimation. The present study aims to examine the anatomical and microscopic features of the PAN to analyze its feasibility as a donor nerve. The bilateral facial side of 14 fresh frozen adult human cadavers was examined for the study. The PAN's anatomical course was recorded, and nerve specimens from the PAN and zygomatic nerve (ZN) were obtained to compare their microscopic anatomy and axon counts using a light microscope and transmission electron microscope. The PAN's average branching distance and its course length were 5.8±2.69mm and 59.2±5.85, respectively. The mean number of myelinated axons was 600.28±69.97 in the PAN and 728.85±166.31 in the ZN. This difference between the two nerves was statistically significant (p=0.002). However, considering the gender variable, the mean axon counts of PAN and ZN were statistically similar for face sides and their average. Furthermore, the ultrastructural anatomy of both nerves was similar in electron microscopic evaluation. The present study confirms that the PAN is a proper candidate to be a supportive donor nerve due to its isolated site, consistent anatomical course, convenient ultrastructural anatomy as well as axonal load.

Refractory neck pain due to Eagle syndrome.

Eagle syndrome, named after Watt W. Eagle, who described the first cases in 1937, is an uncommon syndrome (4-8/10,000 persons) resulting from the styloid process's elongation or mineralization of the stylohyoid ligament.1Badhey A. Jategaonkar A. Anglin Kovacs A.J. Kadakia S. De Deyn P.P. Ducic Y. et al.Eagle syndrome: a comprehensive review.Clin Neurol Neurosurg. 2017; 159: 34-38Crossref PubMed Scopus (54) Google Scholar The typical symptoms are throat and neck pain radiating into the ear, which can be wrongly attributed to various facial neuralgias. A 64-year-old woman had presented to the otolaryngology clinic with a slowly progressive intermittent dull pain in the upper neck of 10 years' duration. The pain was localized to the tonsillar fossa and radiated to the jaw, ear, neck, throat, and oropharynx. It was worsened by head movement and accompanied by dysphagia, a foreign body sensation, a sore throat, and voice changes. She had no history of trauma. The patient had undergone several consultations during the 10-year period, including otolaryngology, family practice, neurology, neurosurgery, psychiatry, and dentistry, with various interventions performed (ie, steroid injection in the temporomandibular joint, radiofrequency ablation, stellate ganglion block, lignocaine infusion, posterior auricular nerve block) without relief. A computed tomography angiogram demonstrated a 4-cm-long styloid process at the level of the mid-internal carotid artery (A and B). Cervical neck incision and styloidectomy were planned. We exposed the common carotid artery and cranial nerves and retracted the posterior belly of the digastric to peel the tendinous attachment around the styloid process toward the mastoid posteriorly and mandible anteriorly for easy separation. The distal end of the styloid process was found to lie close to the hypoglossal, glossopharyngeal, and vagus nerves (C). A 2.5-cm excision of the styloid process was performed. She had complete resolution of the symptoms postoperatively. She had provided written informed consent for the report of her case details and images. The styloid process normally measures 2.5 to 3 cm. However, when its length is >3 cm, the patient will become symptomatic owing to the subsequent pressure on the adjacent structures.1Badhey A. Jategaonkar A. Anglin Kovacs A.J. Kadakia S. De Deyn P.P. Ducic Y. et al.Eagle syndrome: a comprehensive review.Clin Neurol Neurosurg. 2017; 159: 34-38Crossref PubMed Scopus (54) Google Scholar Cervical neck surgery with styloidectomy is the definitive treatment. An alternative approach includes the intraoral transtonsillar route. However, this approach has been associated with high risks, including uncontrolled bleeding and cranial nerve injury because it limits visualization of the important structures.2Strauss M. Zohar Y. Laurian N. Elongated styloid process syndrome: intraoral versus external approach for styloid surgery.Laryngoscope. 1985; 95: 976-979Crossref PubMed Google Scholar

Anatomical Study of the Posterior Auricular Branch of the Facial Nerve: Application to Parotid Surgery.

The posterior auricular nerve (PAN) is the first branch of the facial nerve after it leaves the stylomastoid foramen. The literature describing the anatomy of the PAN is very sparse. Therefore, the purpose of this study was to clarify the detailed anatomical features of the PAN and consider its clinical and surgical applications. The authors examined 10 sides from 6 fresh frozen adult cadaveric Caucasian heads. The PAN was observed as the first branch of the facial nerve in all specimens. During the dissection of the PAN, the posterior auricular artery was constantly near the PAN. Moreover, the PAN was located under the investing layer of deep cervical facia covering the sternocleidomastoid and mastoid process in all specimens. The diameter of the PAN was 0.82 ± 0.21 mm (range from 0.55 to 1.21). The distance from the stylomastoid foramen to where the PAN branched from the facial nerve was 0.40 ± 1.25 mm (range from 0 to 4.35). The distance from the location of this branching point of the PAN to the entering point of the PAN to any muscles was 28.03 ± 5.51 mm (range from 19.71 to 38.75). Understanding the anatomical features of the PAN is essential for performing surgical procedures in this region.

Imaging Peripheral Nerve Regeneration: A New Technique for 3D Visualization of Axonal Behavior

BackgroundPeripheral nerve assessment has traditionally been studied through histological and immunological staining techniques in a limited cross-sectional modality, making detailed analysis difficult. A new application of serial section electron microscopy is presented to overcome these limitations. MethodsDirect nerve repairs were performed on the posterior auricular nerve of transgenic YFP-H mice. Six weeks postoperatively the nerves were imaged using confocal fluorescent microscopy then excised and embedded in resin. Resin blocks were sequentially sectioned at 100 nm, and sections were serially imaged with an electron microscope. Images were aligned and autosegmented to allow for 3D reconstruction. ResultsBasic morphometry and axonal counts were fully automated. Using full 3D reconstructions, the relationships between the axons, the Nodes of Ranvier, and Schwann cells could be fully appreciated. Interactions of individual axons with their surrounding environment could be visualized and explored in a virtual three-dimensional space. ConclusionsSerial section electron microscopy allows the detailed pathway of the regenerating axon to be visualized in a 3D virtual space in comparison to isolated individual traditional histological techniques. Fully automated histo-morphometry can now give accurate axonal counts, provide information regarding the quality of nerve regeneration, and reveal the cell-to-cell interaction at a super-resolution scale. It is possible to fully visualize and “fly-through” the nerve to help understand the behavior of a regenerating axon within its environment. This technique provides future opportunities to evaluate the effect different treatment modalities have on the neuroregenerative potential and help us understand the impact different surgical techniques have when treating nerve injuries.

Development of the interscutularis model as an outcome measure for facial nerve surgery

IntroductionAnimal models for the study of facial paralysis have been well developed, but concern has arisen regarding the accuracy of eye closure and whisker movement as outcome measures due to new data regarding interconnectivity between facial nerve branches and autonomic innervation. The posterior auricular nerve (PAN) is an isolated branch of the facial nerve which has been confirmed as the sole motor innervat or of the interscutularis muscle. This study was designed to develop a model for facial nerve palsy utilizing the PAN and interscutularis muscle. MethodsA custom-made automated video capture system was built into a poly methyl methacrylate cage using a high definition monochrome digital camera and image sensor to record the animal as it drank from a water feeder. A copper floor pad and copper collar around the water feeder were connected to an electrical circuit for automatic saving of the video recording 10 s prior to and 30 s following the drinking event. A pre-operative baseline recording of ear movement during drinking was captured. Female YFP-16 mice at 6 weeks were assigned to sham (Sh, n = 5), nerve excision (Ex, n = 10), or nerve crush (Cr, n = 10) groups with all interventions performed on the right PAN. Sh mice were irrigated with 10 ml normal saline as were the Ex and Cr mice following operative intervention. In Ex mice, a 3 mm section of the PAN was sharply excised and nerve gap was confirmed with fluorescent microscopy. In Cr mice, the PAN was crushed 3 mm from the origin of the facial nerve trunk with size 5 jeweler’s forceps for two periods of 20 s. Post-operative video recordings were collected on post-operative days (POD) 1, 10, 20, and 30. To determine the change in ear movement, the right ear was graphically compared to the left control side. ResultsSh animals exhibited a statistically significant reduction in ear movement at POD01 compared to other POD recordings (p < 0.05), but no significant change in right ear movement following POD05. Ex animals had a significant reduction in right ear movement at all PODs in comparison to the left ear (p < 0.05) with no significant change in right ear movement during the study period (p = 0.94). Cr animals showed a significant reduction in right ear movement compared to the left at POD01, POD10, and POD20 (p < 0.05). At POD30, there was no significant difference between ear movement on either side (p = 0.35). There was a significant change in right ear movement during the data collection period (p < 0.05). ConclusionThe results show that significant differences were demonstrated between the experimental groups and that significant changes within the crush group were identifiable making this an acceptable model to develop as an accurate outcome measure following rodent facial nerve surgery.

The Feasibility of Using the Posterior Auricular Branch of the Facial Nerve as a Donor for Facial Nerve Reanimation Procedures: A Cadaveric Study

Facial nerve paralysis can result in critical complications, including those to the visual, respiratory, and digestive systems. The facial nerve has been reanimated using various nerves, but the posterior auricular nerve (PAN) branching off the facial nerve has not been explored for this purpose. Ten sides from 6 fresh-frozen adult cadavers were used for dissection of the PAN to explore its potential as a donor for facial nerve reanimation. The facial nerve trunk (FNT) and PAN were consistently and readily identified by deep dissection using the tragal cartilage and tragal pointer as landmarks. The PAN was transected at the point of insertion of its innervated muscles. Its length and diameter were measured, and it was transposed anteriorly to the FNT and its 2 major extracranial divisions. The PAN was observed on all sides. Its available length was 27.11±5.02mm and its mean diameter was 0.85±0.20mm. In all specimens, the PAN readily reached the FNT and its 2 major divisions without tension. No previous study has explored the use of the PAN as a donor for facial nerve reanimation. Based on the present cadaveric study, surgeons might consider it for this purpose.

A new method for tracing the facial nerve trunk using the posterior auricular nerve.

Tracing the facial nerve trunk is an essential action in parotid surgery, because of the implications of injury to the nerve or its branches. More than a few landmarks that may help the surgeon in this task have been proposed (e.g., the posterior belly of the digastric muscle, the tragal pointer, among others), under the assumption that additional access methods improve the surgical technique and reduce the possibility of harmful post-operative consequences. Here we present evidence that the posterior auricular nerve may be used to trace the facial nerve trunk. We dissected 75 cadaveric heminecks, exposed the auricularis posterior muscle and adnexa, and attempted to follow the posterior auricular nerve to the facial nerve trunk. The auricularis posterior muscle, nerve, and artery were identified in all heminecks, securing an anatomically reliable route to the facial nerve trunk. Average length of the nerve from the auricularis posterior muscle to the facial nerve trunk was 28 mm (±6.2 mm). The angle between the posterior auricular nerve and the vertical segment of the FN trunk was 39.5° (±7.7°). We conclude that the posterior auricular nerve may be used as a landmark to trace the facial nerve trunk. It is advantageous due to the relatively simple and consistent regional anatomy, and also because manipulation of this nerve does not present a risk given that the auricularis posterior muscle is vestigial. The proposed landmark is particularly important in revision surgery, where the pre-auricular anatomy may have been distorted and scarred by previous operations. Clin. Anat. 32:453-457, 2019. © 2019 Wiley Periodicals, Inc.

Morphological study of the occipital belly of the occipitofrontalis muscle and its innervation.

Occipital belly (OB) of occipitofrontalis muscle (epicranius) is a muscle which covers the occipital part of the skull. The posterior auricular nerve (PAN) is the first extracranial branch of the facial nerve, which supplies the OB. The PAN is one of the structures used to identify the facial nerve during surgeries such as parotidectomy and mastoidectomy. In the present report, we provide detailed anatomical knowledge of the OB and its innervation. Twenty-six hemifaces from 14 Korean cadavers were dissected. The mastoid tip, external occipital protuberance (EOP), a horizontal line that is parallel to the Frankfurt horizontal plane (x-axis), and a vertical line through the EOP (y-axis) were used as reference points and lines. The OB demonstrated a variety of features and was mostly asymmetrical. The muscle bellies were observed to angle toward the temporoparietalis muscle laterally, with the aponeurosis angled at approximately 55°-65°. The mean width and height were 60.9±8.7 and 31.7±7.5mm, respectively. Muscle bellies were located at a mean distance of 7.1±2.5mm superior to the x-axis and 29.6±6.4mm lateral to the y-axis. The mean vertical distance from the origin of the PAN at the anterior border of the mastoid process (MP) to the mastoid tip was 6.1±2.1mm. The mean nerve angle between the PAN and the x-axis was 55.7°±6.8°. The entry point of the PAN that innervates the OB was positioned at a mean distance of 9.0±3.5mm superior to the x-axis and 79.0±8.1mm lateral to the y-axis. Understanding the morphometrical characteristics of the OB and its innervation may potentially improve surgical outcomes to assist in locating the posterior auricular branch of the facial nerve.

Posterior auricular nerve found anterior to the cartilage of the external auditory meatus—a previously unreported variant

We describe a previously unreported anatomical variant of the posterior auricular nerve found during parotidectomy, and discuss its clinical implications.

Hmx1 is required for the normal development of somatosensory neurons in the geniculate ganglion

Hmx1 is a variant homeodomain transcription factor expressed in the developing sensory nervous system, retina, and craniofacial mesenchyme. Recently, mutations at the Hmx1 locus have been linked to craniofacial defects in humans, rats, and mice, but its role in nervous system development is largely unknown. Here we show that Hmx1 is expressed in a subset of sensory neurons in the cranial and dorsal root ganglia which does not correspond to any specific sensory modality. Sensory neurons in the dorsal root and trigeminal ganglia of Hmx1dm/dm mouse embryos have no detectable Hmx1 protein, yet they undergo neurogenesis and express sensory subtype markers normally, demonstrating that Hmx1 is not globally required for the specification of sensory neurons from neural crest precursors. Loss of Hmx1 expression has no obvious effect on the early development of the trigeminal (V), superior (IX/X), or dorsal root ganglia neurons in which it is expressed, but results in marked defects in the geniculate (VII) ganglion. Hmx1dm/dm mouse embryos possess only a vestigial posterior auricular nerve, and general somatosensory neurons in the geniculate ganglion are greatly reduced by mid-gestation. Although Hmx1 is expressed in geniculate neurons prior to cell cycle exit, it does not appear to be required for neurogenesis, and the loss of geniculate neurons is likely to be the result of increased cell death. Fate mapping of neural crest-derived tissues indicates that Hmx1-expressing somatosensory neurons at different axial levels may be derived from either the neural crest or the neurogenic placodes.

Variations in the anatomy of the posterior auricular nerve and its potential as a landmark for identification of the facial nerve trunk: a cadaveric study

The posterior auricular nerve (PAN) is the first extracranial branch of the facial nerve trunk. It innervates the posterior belly of the occipitofrontalis and the auricular muscles and contributes cutaneous sensation from the skin covering the mastoid process and parts of the auricle. This study was carried out to provide a detailed account of its anatomy and to ascertain its reliability as a surgical landmark for the facial nerve. Eleven facial sides from six formalin-fixed cadavers were dissected. The course and arborisation pattern of the PAN was observed, and its position of emergence from the facial nerve trunk (FNT) was measured. The PAN arose from the posterolateral aspect of the FNT 1.6-11.1 mm from the stylomastoid foramen (5.4 ± 3.3 mm). It arose as a single branch (45.4%), or from a common trunk that divided into two (36.4%) or three branches (18.2%), with the other branches passing into the parotid gland. The PAN continued deep (63%), or lateral to the mastoid process (9.1%), or through the tissue of the parotid gland (27.3%). In all cases the PAN ran in a consistent, superficial location posterior to the external auditory meatus. The PAN takes a variable course; however, its consistent location behind the external auditory meatus makes it easily identifiable in superficial dissection, and therefore a potential surgical landmark for identifying the FNT.

Topographic anatomy of the peripheral branches of the facial nerve

Objective: The facial nerve and close relationship between its branches and parotid duct were investigated. Methods: This study was performed on 31 half heads of 16 fixed cadavers. The extracranial course of the nerve was exposed. The posterior auricular nerve origined from facial nerve and branches forming the parotid and buccal plexuses were investigated. The parotid duct and anastomoses between branches of the nerve were also investigated. Results: We observed differences in the course of the branches of the facial nerve. The posterior auricular nerve was arised directly from the facial nerve before entering the parotid gland in 20 sides, arised from onset of cervicofacial ramus in 10 sides and arised from temporofacial ramus in one side. Pattern differences of parotid and buccal plexuses and especially anastomoses between the branches were identified. Conclusion: We are in the opinion that the knowledge of courses and relationships of the branches of the facial nerve will actually provide a great benefit in preventing surgical complications.

Effects of sympathetic histamine on vasomotor responses of blood vessels in rabbit ear to electrical stimulation

To investigate the effects of histamine receptor antagonists on vasoconstriction induced by electrical stimulation (ES) on posterior auricular nerve, and to explore the pre- and post-synaptic effects of sympathetic histamine on the vasomotor responses of vascular smooth muscle in rabbit ear. ES was applied to posterior auricular nerves of the whole rabbit ear at 10 Hz, 20 Hz and 40 Hz, respectively. Besides, the whole ear was perfused with different histamine receptor antagonists under constant perfusion pressure, and the changes in the flow rate of perfusate were observed. The flow rate of venous outflow was decreased by ES at all the 3 frequencies. The ES-induced vasoconstriction at 20 Hz and 40 Hz could be partly inhibited by H(1) receptor antagonist chlorpheniramine (P < 0.05). After exhaustion of histamine in mast cells by pretreatment with specific mast cell degranulator compound 48/80, chlorpheniramine could still inhibit the ES-induced flow rate reduction. In contrast, H(2) receptor antagonist cimetidine could enhance the 40-Hz ES-induced flow rate reduction (P < 0.05). Moreover, ES-induced vasoconstriction at the 3 frequencies could all be enhanced by H(3) receptor antagonist thioperamide (P < 0.05). Stimulation on the auricular nerve may evoke histamine release from sympathetic nerves rather than from mast cells. Moreover, the functions of sympathetic histamine vary from pre-synaptic modulation to post-synaptic vasoconstriction or vasodilatation, via activation of different histamine receptors.

Neurologic Sequelae After Interscalene Brachial Plexus Block for Shoulder/Upper Arm Surgery: The Association of Patient, Anesthetic, and Surgical Factors to the Incidence and Clinical Course

We determined the incidence, distribution, and resolution of neurologic sequelae and the association with anesthetic, surgical, and patient factors after single-injection interscalene block (ISB) using levobupivacaine 0.625% with epinephrine 1:200,000 in subjects undergoing shoulder or upper arm surgery, or both, in 693 consecutive adult patients. After a standardized ISB, assessments were made at 24 and 48 h and at 2 and 4 wk for anesthesia, hypesthesia, paresthesias, pain/dysesthesias, and motor weakness. Symptomatic patients were monitored until resolution. Subjects reporting pain or discomfort >3 of 10 and those with motor or extending sensory symptoms received diagnostic assessment. Six-hundred-sixty subjects completed 4 wk of follow-up. Fifty-eight neurologic sequelae were reported by 56 subjects. Symptoms were sensory except for two cases of motor weakness (lesions identified distant from the ISB site). Thirty-one sequelae with likely ISB association were reported by 29 subjects, including 14 at the ISB site, 9 at the distal phalanx of thumb/index finger, 7 involving the posterior auricular nerve, and 1 clinical brachial plexopathy. Sequelae not likely associated with the ISB were reported by 27 subjects with symptoms reported in the median (n = 9) and ulnar (n = 4) nerves, surgical neuropraxias (n = 12), and motor weakness (n = 2). Symptoms resolved spontaneously (median 4 wk; range, 2-16 wk) except in the two patients with motor weaknesses and the patient with clinical brachial plexopathy, who received therapeutic interventions. Variables identified as independent predictors of neurologic sequelae likely related to ISB were paresthesia at needle insertion and ISB site pain or bruising at 24 h. In contrast, surgery preformed in the sitting position, as well as ISB site bruising, was identified as a predictor of neurologic sequelae not likely related to ISB. In conclusion, neurologic sequelae after single-injection ISB using epinephrine mainly involve transient minor sensory symptoms.

Microsurgical anatomy of the facial nerve trunk.

Dissection and manipulation of the facial nerve (FN) trunk between its exit from the cranial base through the stylomastoid foramen (SMF) and its bifurcation is a critical step in various otologic, plastic and neurosurgical procedures. This study demonstrates the anatomical relationships and variability of the FN trunk with emphasis on some important morphometric data, particularly with relevance to hypoglossal-facial nerve anastomosis (HFA). Bilateral microsurgical dissection was performed on twenty-three human cadavers fixed with formalin. The whole trunk of the FN was exposed, its diameter at the SMF and its length were measured, its branches were observed and the site of its bifurcation was determined. Anastomotic connections with other nerves and blood supply of the trunk were studied. The FN invariably emerged from the cranial base through the SMF. Its diameter upon its emergence from the foramen was 2.66 +/- 0.55 mm. Two branches consistently originated from the trunk: the posterior auricular nerve and the nerve to the digastric muscle. Less consistent were the communicating branch with the glossopharyngeal nerve and the nerve to the stylohyoid muscle. The bifurcation of the FN occurred before its penetration into the parotid gland in 15% of cases and within the gland in 85%. The length of the FN trunk was 16.44 +/- 3.2 mm. Anastomoses between the FN and other nerves were observed in one-third of the dissections. The blood supply to the FN trunk was provided by the stylomastoid artery that was identified in 91% of cases. Understanding the microsurgical anatomy of the FN trunk is essential for performing any surgical procedure in the relevant region. Surgical implications of this study are presented with emphasis on HFA surgery.

Die neurogene Entzündung im Ausbreitungsgebiet des Nervus facialis der Ratte*

Antidromic electrical stimulation of sensory nerves produces vascular hyperpermeability, plasma protein extravasation and oedema. The initial phase of this inflammatory reaction is induced by the release of the neuropeptides CGRP, SP and NKA; the later phase is induced by mast cells. In previous investigations we were able to show that the facial nerve of the rat contains CGRP, SP and NKA as well as mast cells. The same mechanism--increased vascular permeability--plasma extravasation--oedema--is thought to be part of the pathogenesis of Bell's palsy. Hence, we tried to produce neurogenic inflammations in the facial nerves of six adult Wistar rats. To assess plasma extravasation we used Evans blue, a dye which binds to serum albumin, according to the method described by Brokaw and White (1992). Having cut the facial nerve distal of the stylomastoid foramen we induced a neurogenic inflammation by the application of an electrical stimulus to the distal part of the nerve. In comparison to the contralateral, non-stimulated side, we recognized that the inflammatory reactions were limited to the area of the skin innervated by the posterior auricular nerve. So far, we can transfer this "neurogenic inflammation model" the well-known relationship between nerves and inflammatory reactions to this limited area innervated by the facial nerve.

Proximal communication between the glossopharyngeal and facial nerves.

The facial nerve branch termed Ramus communicans cum nervo glossopharyngeo in the current Nomina anatomica was investigated in 245 Japanese, especially as regards the frequency and pertinence as an approved definition. The communication was found in only 18.8%. It runs, if present, either medially, laterally or through the digastric posterior muscle. Teasing examination reveals that it always originates from the ninth nerve instead of the seventh and that it is destined to the back of the pinna. Its terminal bundle leaves the seventh nerve somewhat distally than the posterior auricular nerve in many examples, but the communication is likely to represent the auricular branch of the ninth nerve. As an offshoot of the seventh nerve, it is ill-defined, and should be affiliated to the ninth nerve in the Nomina anatomica. If it pierces the digastric muscle, half examples certainly give additional innervation to this muscle, but the fundamental disposition of the communication itself is not affected.