Distal Facial Nerve Research Articles

The hypoglossal–facial nerve repair as a method to improve recovery of motor function after facial nerve injury

Nerve repair after facial nerve injury provides neural input to the distal facial nerve and facial musculature via a variety of motor nerves such as hypoglossal, spinal accessory, masseteric branch of the trigeminal nerve and motor branches of the cervical plexus. The most commonly used procedure is the hypoglossal-facial nerve transfer. This cross-nerve paradigm is a unique nerve repair method as one motor nerve takes over the function of another motor nerve. The hypoglossal-facial nerve repair was reviewed by means of history, terminology, technical variations, and its capacity for recovery of function.

Bilateral bifid labyrinthine facial nerve anomalies associated with agenesis of the oval window: Case report and review of the literature

Formation of the nerve commences early in gestation with the facioacoustic primordium (derived from the neural crest and otic vesicle) separating into facial and acoustic components at the end of the 4th week. By the end of the 5th gestational week, the chorda tympani has differentiated from the distal facial nerve. By the 8th week, the orientation of the facial nerve within the temporal bone has been established, with the nerve’s ultimate position and bony covering determined by development of the stapes and membranous labyrinth.

An objective assessment of proximal and distal facial nerve exploration during superficial parotidectomy

Aim:This study was undertaken to compare the proximal and distal facial nerve exploration approach during superficial parotidectomy.Materials and Methods:A retrospective analysis of patients who underwent superficial parotidectomy at our center was conducted. Cases were divided into those who underwent superficial parotidectomy using distal facial nerve exploration and those who underwent standard proximal facial nerve exploration. Statistical comparisons of intraoperative blood loss and margin status (negative, focally, positive) were conducted between these two approaches.Results:A total of 39 patients underwent superficial parotidectomy at our center between 2008 and 2010. The technique used in most of the cases was conventional proximal nerve exploration technique (29 cases). Distal exploration of the buccal branch was undertaken only in 10 cases, on account of difficulty in locating the main trunk intraoperatively due to the presence of postinflammatory fibrosis. The average patient age was 48 years with a female preponderance (67%). Both the techniques consumed almost same average operative time (2.4 hours) and average intraoperative blood loss (68.0 cc vs 25.4 cc) was more in the cases where proximal nerve exploration was resorted (S.E (d) = 0.89). No significant difference in surgical margin status was noticed between the two techniques (P > 0.05).Conclusion:Both the techniques are efficient without compromising the surgical margins, but the average intraoperative blood loss is less in distal facial nerve exploration technique.

Repair of Whole Rabbit Facial Nerve Defects Using Facial Nerve Allografts

To investigate the feasibility of repairing whole facial nerve defects with chemically extracted acellular whole facial allografts nerves and its effect on motor conductivity recovery. Whole nerve defects (branches and trunk) were made in 4 rabbit groups (n = 18), and the nerve defect was bridged using 1) acellular facial nerve allografts, 2) facial nerve isografts, 3) acellular peroneal nerve allografts, and 4) peroneal nerve isografts. Six months later, cell morphology, nerve microbeam distribution, angiogenesis, and collagen were observed in the distal and center of the grafts with special trichrome staining. The regenerated nerve fibers and Schwann cells in the anastomosis site were immunohistochemically stained. Nerve axon numbers and passing rates were analyzed with computer-captured images. The regenerated nerve ultrastructure was analyzed by transmission electron microscopy. Regenerated nerve fibers and vessels were found in the grafts, with no differences between groups A and B. Groups C and D had poor nerve continuity with little vascular regeneration. The distal segments of nerve transplants in groups A and B showed strong positive neurofilament staining, higher than in groups C and D. In groups A and B, many long spindle-shaped Schwann cells proliferated longitudinally in the nerve transplant, but less in groups C and D. Myelinated nerve fibers were found in the distal facial nerve. There were no differences between groups A and B in fiber number and myelin sheath thickness, which were much lower than normal, whereas little myelin sheath regeneration was observed in groups C and D. Chemically extracted acellular whole facial nerve allografts are feasible for repairing whole facial nerve defects.

Proximal and distal Facial nerve exploration during superficial parotidectomy

One of the most technique sensitive surgeries in the maxillofacial region is the parotid gland surgery owing to the close relation between the gland and the extra-cranial course of facial nerve. Facial nerve is generally located by means of a proximal surgical identification technique aimed at identifying the facial nerve at its point of exit from the stylomastoid foramen to its entry into the posteromedial surface of parotid gland. There are reports in the literature on distal nerve identification techniques, either as a choice or in cases where proximal nerve identification is difficult. The present report deals with personal clinical experience, describing both the techniques for detection of the facial nerve in 17 cases reported. The technique mainly chosen was conventional proximal nerve identification technique in 16 cases. Distal exploration of the buccal branch was undertaken only in one case, on account of difficulty in locating the main trunk intraoperatively, due to the presence of a post inflammatory fibrosis. The decision to resort to the identification of the buccal nerve is supported by the regular course and adequate size of this branch of facial nerve in its peripheral area co-located with stenson's duct, which enable it to be easily identified during surgery.

High‐resolution ultrasound in the evaluation and prognosis of Bell’s palsy

Bell's palsy is a commonly encountered paralysis of the facial nerve occurring worldwide. Prognosis for Bell's palsy is good, but the proportion of patients with poor outcomes may reach 30%. Ultrasound (US) may provide a novel approach for evaluating and prognosticating Bell's palsy, in comparison with known electrophysiological techniques. In this study, we measured the diameter of the distal facial (VII) nerve using US in patients with Bell's palsy treated with prednisolone, in comparison with healthy controls. Blink reflex and VII nerve conduction studies were also performed. Studies were prospective and performed within 1 week of disease onset. Our results have shown that diameter of the distal VII nerve is a good predictor of favorable (positive predictive value: 100%) and bad outcomes (negative predictive value: 77%) in Bell's palsy at 3 months after clinical presentation. Furthermore, we also noted the lack of correlation of VII diameter with conventional VII nerve conduction studies (NCS) and blink reflex studies. US was superior to VII nerve conduction and blink reflex studies in outcome prediction. This first study utilizing US in Bell's palsy highlights its role in outcome prediction and contributes to our understanding of recovery processes in this common neurological disorder.

Distal facial nerve exposure: A key to partial parotidectomy

Objectives 1) Compare outcomes of distal facial nerve identification with antegrade exposure in partial parotidectomy; 2) Be able to incorporate other modifications of parotidectomy including preservation of the great auricular nerve, superficial musculo-aponeurotic system (SMAS), and parotid duct. Study Design Case series with chart review of partial parotidectomy for benign neoplasms and intraparotid lymph nodes, using antegrade (Group 1) or distal (Group 2) facial nerve exposure, and those conserving the great auricular nerve, SMAS, and parotid duct (Group 3). Subjects and Methods Outcomes for the three groups were reviewed. The great auricular nerve, parotid duct, and SMAS were preserved when possible. Outcomes examined included postoperative facial nerve function, earlobe sensation, allograft use for SMAS defects, surgical duration, sialocele, or salivary fistula. Results No difference in facial nerve function was found between the groups. Group 3 had better ear lobule cutaneous sensation. No sialoceles occurred in the 10 of 14 Group 3 cases in which parotid ducts were preserved. Conclusions Partial parotidectomy utilizing distal facial nerve exposure can reduce the extent of surgical dissection, facilitate preservation of the parotid duct and great auricular nerve, and allow greater flexibility in the choice of skin and SMAS incisions.

Neurovascular compression findings in hemifacial spasm

It is generally accepted that hemifacial spasm (HFS) is caused by pulsatile vascular compression upon the facial nerve root exit zone. This 2-3 mm area, considered synonymous with the Obersteiner-Redlich zone, is a transition zone (TZ) between central and peripheral axonal myelination that is situated at the nerve's detachment from the pons. Further proximally, however, the facial nerve is exposed on the pontine surface and emerges from the pontomedullary sulcus. The incidence and significance of neurovascular compression upon these different segments of the facial nerve in patients with HFS has not been previously reported. The nature of neurovascular compression was determined in 115 consecutive patients undergoing their first microvascular decompression (MVD) for HFS. The location of neurovascular compression was categorized to 1 of 4 anatomical portions of the facial nerve: RExP = root exit point; AS = attached segment; RDP = root detachment point that corresponds to the TZ; and CP = distal cisternal portion. The severity of compression was defined as follows: mild = contact without indentation of nerve; moderate = indentation; and severe = deviation of the nerve course. Success in alleviating HFS was documented by telephone interview conducted at least 24 months following MVD surgery. Neurovascular compression was found in all patients, and the main culprit was the anterior inferior cerebellar artery (in 43%), posterior inferior cerebellar artery (in 31%), vertebral artery (in 23%), or a large vein (in 3%). Multiple compressing vessels were found in 38% of cases. The primary culprit location was at RExP in 10%, AS in 64%, RDP in 22%, and CP in 3%. The severity of compression was mild in 27%, moderate in 61%, and severe in 12%. Failure to alleviate HFS occurred in 9 cases, and was not related to compression location, severity, or vessel type. The authors observed that culprit neurovascular compression was present in all cases of HFS, but situated at the RDP or Obersteiner-Redlich zone in only one-quarter of cases and rarely on the more distal facial nerve root. Since the majority of culprit compression was found more proximally on the pontine surface or even pontomedullary sulcus origin of the facial nerve, these areas must be effectively visualized to achieve consistent success in performing MVD for HFS.

Distal Facial Nerve Exposure: A Key to Partial Parotidectomy

Objective 1) Learn techniques and outcomes of distal facial nerve identification compared with antegrade exposure in partial parotidectomy. 2) Be able to incorporate other modifications of parotidectomy facilitated by distal facial n. isolation including preservation of the greater auricular nerve, superficial musculo-aponeurotic system (SMAS), and parotid duct. Methods 29 parotidectomies done using antegrade facial nerve trunk exposure (Group 1) and 13 consecutive partial parotidectomies done with distal facial nerve branch dissection (Group 2) for benign neoplasms and intraparotid lymph nodes were reviewed from 2001 to 2008. The greater auricular nerve and SMAS were preserved when possible. Branches draining to the main parotid duct from the lesion were incised rather than the main parotid duct whenever feasible. Outcomes examined include postoperative facial nerve function, cutaneous sensation, SMAS preservation, sialocele or salivary fistula. Logistic Regression was used to determine if select variables (age; antegrade vs. retrograde nerve exposure; and size of tumor) significantly affected outcomes. A series of univariate analysis of variance with Bonferroni post hoc tests were subsequently used to confirm findings of the logistic regression. Results No difference in facial nerve function was found between the groups. Group 2 had better cutaneous sensation and SMAS preservation. More salivary fistulas and parotid swelling were associated with parotid duct transection in Group 1. There were no tumor recurrences. Conclusions Partial parotidectomy utilizing distal facial nerve exposure can reduce the extent of surgical dissection, facilitate preservation of the parotid duct and greater auricular nerve, improve contour with primary SMAS closure, and allow greater flexibility in skin incisions.

Elektrophysiologische Diagnostik der Fazialisparesen und des Hemispasmus fazialis

We summarise the electrophysiolgical techniques used to investigate the central cortico-facial projections and the facial nerve. These include transcranial magnetic stimulation of the primary motor cortex and the proximal facial nerve, direct electrical stimulation of the distal facial nerve, blink reflex and electromyography. We also describe the lesion patterns in peripheral facial nerve palsy and hemifacial spasm.

Re-activation of atrophic motor Schwann cells after hypoglossal-facial nerve anastomosis

Facial nerve lesions are common in humans and often require surgical intervention. If repair is delayed, reinnervation can be facilitated by transposing the freshly cut hypoglossal nerve end-to-end directly to the distal facial nerve, allowing for uncompromised hypoglossal axons to reinnervate the denervated facial musculature (hypoglossal-facial anastomosis, HFA). Schwann cells (SCs) in the distal nerve stump have an important function in promoting axonal regeneration by expressing multiple regeneration-associated proteins. Chronically denervated SCs cease to express those factors, but it is unknown whether they can be reactivated by fresh axonal sprouts and regain part of their function. We evaluated SC function and viability in distal facial nerve stump of rats at various time points after chronic denervation as well as following immediate or delayed HFA by assessing their expression of growth-associated protein 43 kDa (GAP-43) and the neuregulin receptors erbB2 and erbB4. Our results show that maximal upregulation of those factors in denervated SCs occurred a few weeks after nerve transection, indicating that a short period of denervation might even be beneficial before nerve repair. Motor SCs denervated for 32 weeks had downregulated their activity and ceased to express the regeneration-associated factors. SCs immediately re-expressed GAP-43, erbB2, and erbB4 following contact with fresh hypoglossal motor axons, demonstrating they are competent to promote regeneration even after long-term denervation.

Axonal excitability properties in hemifacial spasm

Hemifacial spasm (HFS) is characterized by involuntary, irregular contractions of muscles innervated by the facial nerve. Whether the facial nerve has a relative predisposition for ectopic activity has not been clarified. Nerve excitability techniques, which provide information about membrane potential and axonal ion channel function, were initially measured in 12 control subjects looking for biophysical differences that may predispose the facial nerve to generate ectopic activity. In a second series of studies, facial nerve excitability was assessed in nine HFS patients. In both series, stimulus-response behavior, threshold electrotonus, a current threshold relationship, and the recovery of excitability following supramaximal stimulation were recorded following stimulation of the facial nerve. When compared to normative data from nerves in the upper and lower limbs, there was a relative "fanning-in" of threshold electrotonus, reduced superexcitability, and increased subexcitability in facial nerve studies from control subjects (P < 0.05), consistent with relative axonal depolarization. These findings may underlie the propensity for the facial nerve to develop ectopic impulse activity in motor axons. In the HFS patient study, there were no significant differences in distal facial nerve excitability properties from the affected side in HFS patients when compared either to the unaffected side or to normative facial nerve data. It is concluded that the impulse generator underlying HFS must consequently be sited more proximally and does not cause a generalized disturbance of motor axon excitability.

PR29 MASSETERIC‐FACIAL NERVE COAPTATION – AN ALTERNATIVE TECHNIQUE FOR FACIAL NERVE REINNERVATION

Introduction Facial nerve paralysis can be a disabling condition functionally, psychologically and aesthetically. When there has been an acquired proximal injury to the facial nerve in the presence of previously functional facial musculature, such as in acoustic neuroma surgery, neurotisation of the distal facial nerve is an appropriate choice of management. The hypoglossal nerve is most commonly used. However this is not without its limitations, notably subsequent hemilingual atrophy and facial synkinesis. We present an alternative technique of facial reinnervation utilising a motor branch of the trigeminal nerve, the nerve to masseter. We believe this technique has the potential to overcome problems encountered with use of other extra‐facial nerves.Methods Three patients with acquired facial nerve palsy following tumour resection underwent transfer of the ipsilateral masseteric nerve to facial nerve. In two patients the nerve was directly coapted to the trunk of the facial nerve while the third patient had transfer to the buccal branch.Results By twelve months postoperatively all three patients demonstrated significant improvement in facial muscle tone and symmetry at rest. All patients were able to produce a symmetrical smile with minimal synkinesis. Two of the three patients also had evidence of occasional spontaneous movements.Conclusion Use of the ipsilateral motor nerve to masseter offers an alternative technique for neurotisation of the facial nerve. The advantages of this technique include ease of dissection, constant and reliable anatomy, powerful innervation of the facial muscles, minimal donor site morbidity and the potential for return of spontaneous facial movements.

Perineural Invasion of the Facial Nerve by a Cutaneous Squamous Cell Cancer: A Case Report

We report a case of perineural invasion of the facial nerve by a cutaneous squamous cell carcinoma in a 59-year-old man who presented with a slowly progressive facial paralysis. We performed a distal facial nerve dissection and a simple mastoidectomy with facial recess exposure for resection to negative margins. We also performed a simultaneous facial reconstruction and reanimation procedure with excellent results. External-beam radiation completed the treatment regimen. In addition to describing this case, we review current concepts in diagnosis and therapy, as well as the historical background of malignant perineural invasion of the cranial nerves.

Intraoperative facial motor evoked potential monitoring with transcranial electrical stimulation during skull base surgery

Objective: To address the limitations of standard electromyography (EMG) facial nerve monitoring techniques by exploring the novel application of multi-pulse transcranial electrical stimulation (mpTES) to myogenic facial motor evoked potential (MEP) monitoring. Methods: In 76 patients undergoing skull base surgery, mpTES was delivered through electrodes 1 cm anterior to C1 and C2 (M1–M2), C3 and C4 (M3–M4) or C3 or C4 and Cz (M3/M4–Mz), with the anode contralateral to the operative side. Facial MEPs were monitored from the orbicularis oris muscle on the operative side. Distal facial nerve excitation was excluded by the absence of single pulse responses and by onset latency consistent with a central origin. Results: M3/M4–Mz mpTES ( n=50) reliably produced facial MEPs while M1–M2 ( n=18) or M3–M4 ( n=8) stimulation produced 6 technical failures. Facial MEPs could be successfully monitored in 21 of 22 patients whose proximal facial nerves were inaccessible to direct stimulation. Using 50, 35 and 0% of baseline amplitude criteria, significant facial deficits were predicted with a sensitivity/specificity of 1.00/0.88, 0.91/0.97 and 0.64/1.00, respectively. Conclusions: Facial MEPs can provide an ongoing surgeon-independent assessment of facial nerve function and predict facial nerve outcome with sufficiently useful accuracy. Significance: This method substantially improves facial nerve monitoring during skull base surgery.

Facial Motoneuronal Death after Proximal or Distal Facial Nerve Transection

Facial Motoneuronal Death after Proximal or Distal Facial Nerve Transection

Experimental Study on Facial Nerve Regeneration With or Without Geniculate Ganglionectomy

To investigate regeneration of the distal facial nerve following nerve grafting within the tympanic segment with geniculate ganglion preservation or dissection. Randomized controlled trial. Twenty-three adult New Zealand albino rabbits were used in this study. A 2-mm tympanic segment of the facial nerve was removed, and the greater auricular nerve was harvested for grafting in all animals. In group 1 (10 rabbits), the geniculate ganglion was preserved. In group 2 (13 rabbits), the geniculate ganglion was dissected. Mastoidal and extratemporal segments of the facial nerve were harvested 3 months postoperatively for histological examination by electron microscopy. The number of myelinated axons in normal facial nerves was 1819.6 +/- 535.6. In group 1, the number of myelinated axons was 123.6 +/- 31.1, and, compared with normal facial nerves, the diameter of the regenerative axons was decreased and the sheath thickness in the regenerative fiber was diminished. In group 2, the number of myelinated axons was 515.1 +/- 103.1, while the myelin sheath thickness was proportionate to axon diameter. (Data are given as mean +/- SD.) Geniculate ganglionectomy may improve motor axon regeneration.

Study on facial motoneuronal death after proximal or distal facial nerve transection.

Among the cranial nerves, the facial nerve is most liable to be damaged. Pathologic changes in the facial motor nucleus (FMN) after nerve injury are not well recognized, and the optimal time for facial nerve reconstruction after axotomy is controversial. In this study, to clarify the pathologic change in the FMN after axotomy and to determine the best time for surgery, facial motoneuronal death was investigated after facial nerve injury. Sixty Wistar rats were divided into proximal and distal groups. In the proximal group, the right facial nerve was transected at the porus of internal acoustic meatus. In the distal group, the nerve was cut at the stylomastoid foramen. The animals were sacrificed from day 3 to day 60 after surgery, and the brainstem was fixed with 4% paraformaldehyde. The FMN were then examined in serial sections stained with Cresyl Violet, and facial motoneurons were counted under a light microscope. The death rate of facial motoneurons in the animals that underwent proximal axotomy was found to be higher and cell death occurred earlier than in the distal axotomy animals at every time point. Moreover, neuron death increased with time and peaked at 15 days after surgery. The results indicate that the injury site was correlated with facial motoneuronal death, and suggest that reconstructive surgery should be performed as early as possible.

Facial reanimation with microneurovascular free flaps.

Numerous options are available for rehabilitation of chronic facial nerve paralysis, ranging from simple slings to complex procedures such as microneurovascular tissue transfer. Microneurovascular muscle transfer is generally indicated: 1) if the patient desires dynamic facial reanimation, particularly restoration of involuntary emotional facial expressions; 2) in the absence of distal facial nerve fibers or motor endplate function; 3) with an associated large soft tissue defect in the cheek; and 4) when other dynamic reanimation procedures have not been successful. The most commonly used free flaps for facial reanimation are gracilis, latissimus dorsi and inferior rectus abdominus muscle. When successfully performed free flaps yield excellent functional and aesthetic results in facial reanimation.

Effects of facial nerve injury on mouse motoneurons lacking the p75 low-affinity neurotrophin receptor

When motoneuron axons in peripheral nerves are injured, the expression of the p75 low-affinity neurotrophin receptor (p75) increases in their cell bodies and axons, as well as in the Schwann cells undergoing Wallerian degeneration in the distal excised nerve segment. To understand the role of p75 in the events following nerve injury, we have examined the survival and regeneration of motoneurons in mice lacking the p75 receptor. In adult p75 (-/-) mice, functional recovery of whiskers movement following a facial nerve crush occurred slightly earlier than in p75 (+/+) mice, and some recovery of function over a 25-day interval following a nerve cut occurred more frequently in p75 (-/-) mice. Motoneuron profile numbers were slightly reduced in p75 (-/-) mice, and there were correspondingly fewer axons in the facial nerve. At 25 days following axotomy, profile survival in the adult p75 (-/-) mice was significantly improved compared to p75 (+/+) mice (mean 85%+/-standard error of the mean 3%, n = 11 vs. 67+/-5%, n = 11 in CD-1 mice and 68.0+/-4%, n = 6 in balb/c mice), and significantly more regenerating axons were present in the distal facial nerve. After axotomy on postnatal day 1, there was almost total loss of motoneuron profiles in the lateral facial nucleus in p75 (+/+) mice (1.7+/-0.3% remained, n = 5), while significantly more survived in p75 (-/-) mice (17 +/-2.5 %, n = 6). We conclude that expression of p75 in motoneurons or Schwann cells following facial nerve injury is not necessary for motoneuron survival or prompt regeneration of their axons; rather, p75 may increase their risk of dying.