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PubMed1986

Correlation of the main peripheral branches of the facial nerve with the cytoarchitectonic subdivisions of the facial nucleus in the guinea pig.

Correlation of the main peripheral branches of the facial nerve with morphological subdivisions of the facial nucleus was examined in the guinea pig by the retrograde horseradish peroxidase method. The facial nucleus of the guinea pig was divided cytoarchitectonically into the dorsolateral, lateral, intermediate, medio-intermediate, medial, and ventromedial divisions; the ventromedial division was further divided into the major, dorsal and lateral parts. Six main branches of the facial nerve were identified; the zygomatico-orbital, cervical, posterior auricular, anterior auricular, superior labial, and inferior labial branches. After applying HRP to the main branches of the facial nerve, the pattern of distribution of HRP-labelled neuronal cell bodies within the facial nucleus was examined: the dorsolateral division, dorsal part of the ventromedial division, major part of the ventromedial division, lateral part of the ventromedial division, or medial division contained the cell bodies of respectively the zygomatico-orbital, cervical, posterior auricular, anterior auricular, or superior labial branches, while each of the lateral, intermediate, and medio-intermediate divisions contained the cell bodies of both the superior labial and inferior labial branches.

Animals↗
PubMed1998

Preoperative electroneurography (ENoG) in parotid surgery: assessment of facial nerve outcome and involvement by tumor--a preliminary study.

BACKGROUND: Facial electroneurography (ENoG) is an established and reliable method for assessing neural degeneration in various conditions affecting the facial nerve. The facial nerve may be subclinically involved by parotid tumors, but estimating such involvement preoperatively may be difficult when facial function is normal. The hypothesis that preoperative ENoG: (1) can detect subclinical facial nerve degeneration as a measure of involvement by parotid tumors and (2) can predict facial nerve function following parotidectomy was prospectively evaluated in the present study. METHODS: Twenty-two patients undergoing parotidectomy for tumors were tested preoperatively with ENoG, and their facial nerve function was graded pre- and postoperatively (House-Brackmann system). Eight patients had malignant tumors and 14 benign tumors. RESULTS: In patients with malignant tumors, lower percentage of preoperative ENoG response indicated nerve involvement that was not evident on clinical examination and correlated significantly (p = .035) with postoperative facial nerve dysfunction. Preoperative ENoG reduction of greater than 80% was found in all patients whose facial nerve was infiltrated by tumor. In 14 patients with benign tumors, preoperative ENoG results had no correlation with postoperative facial function. CONCLUSIONS: In malignant tumors, even when facial function is clinically intact, a low preoperative ENoG response may predict facial nerve involvement by the tumor. The lower the preoperative ENoG response, the poorer is the expected postoperative facial nerve function. There was no such correlation in benign parotid tumors.

Action Potentials↗
PubMed1997

Plasticity of the extracranial facial nerve.

Although the expansion properties of peripheral nerves have been a matter of considerable study in recent years, investigations of the plasticity of cranial nerves, including the facial nerve, have been lacking. Clinicians, however, have long recognized the tenacity of facial nerve function in patients with slow-growing benign tumors that enormously distort the nerve. An experimental study was designed to assess whether tissue expansion techniques can be applied to the extracranial portion of the facial nerves of cats. In eight cats the frontozygomatic branch of the facial nerve was expanded by stages in seven sessions over a period of 40 days. The length of the nerve increased an average of 95% without significantly impairing nerve function. Pressure changes in the expander averaged 75 mm Hg during each stage of expansion. Electroneurography was performed after each injection of the expander. Statistical analysis of these data did not show consistent evidence of demyelination or denervation, and all but one cat exhibited a normal blink reflex and had normal electromyographic findings at the end of the experiment. Histologic examination of the expanded nerves, however, did show inflammatory changes, intraneural edema, and occasional demyelination.

Animals↗
PubMed1989

Magnetic stimulation of the facial nerve.

Electrical testing of the facial nerve has evolved into an important means of assessing neural injury. However, the inability to stimulate the intratemporal facial nerve electrically results in a delay in diagnosis, because axonal degeneration must progress distal to the stylomastoid foramen before testing can be meaningful. To circumvent this problem, we began an investigation of magnetic stimulation of the facial nerve, because pulsed magnetic fields can pass unattenuated through all body structures, including bone. Normal volunteers and one patient with acute facial paralysis were studied with both magnetic and electric stimulation of the facial nerve. The results indicate that (1) magnetic stimulation was more comfortable because high current levels were not required at the skin surface to assure indepth stimulation, (2) magnetic and electric stimulation of the extratemporal facial nerve resulted in nearly identical compound muscle action potentials, indicating that the sites and mechanisms of neural depolarization are similar, and (3) transtemporal magnetic stimulation appears to allow depolarization of the proximal intratemporal nerve. These preliminary results are encouraging and indicate that magnetic stimulation of the facial nerve warrants further investigation.

Action Potentials↗
PubMed1981

Percutaneous radiofrequency facial nerve coagulation in the management of facial spasm.

The authors have developed a fluoroscopy-assisted technique of percutaneous radiofrequency facial nerve coagulation at or near the stylomastoid foramen for management of facial spasm. The details of the procedure and the operative results in the initial series of 27 cases of facial spasm are described. The series included six men and 21 women, aged from 16 to 73 years. Twenty-four patients had classical, intractable, persistent hemifacial spasm, one had an unusual bilateral facial spasm, and one a postparalytic facial spasm. The age of onset varied from 16 years to 70 years. The duration of the symptoms ranged from 3 months to 11 years. Ten patients had undergone previous blunt-needle compression of the facial nerve from one to 10 times. The operative results in the 27 patients have so far been excellent. The longest follow-up has been 1 1/2 years. Although partial facial weakness was present in 60% of the cases, it invariably disappeared within 1 to 4 months. Only three patients experienced recurrence of spasm. In two of them, recurrence followed low-temperature coagulation. The procedure is simple, easy to perform, and extremely effective. It can be performed under local anesthesia in the outpatient clinic.

Adolescent↗
PubMed1994

Facial nerve demyelination and vascular compression are both needed to induce facial hyperactivity: a study in rats.

It is generally assumed that hemifacial spasm (HFS) is caused by vascular compression of the facial nerve at the root exit zone (REZ), but the mechanism for the development of HFS is not known. Evidence has been previously presented that the signs of HFS are caused by hyperactivity of the facial motonucleus that is caused by the irritation to the facial nerve from the vascular contact. This assumption has been supported by the finding that daily electrical stimulation of the facial nerve in the rat facilitates the development of an abnormal muscle response that is a characteristic sign of HFS in man and is an indication of an abnormal cross-transmission that makes it possible to elicit a contraction of muscles innervated by one branch of the facial nerve by electrically stimulating another branch of the facial nerve. In the present study we show that close contact between a peripheral branch of the facial nerve and an artery also facilitates the development of an abnormal muscle response, but only if the facial nerve has previously been slightly injured (by a chromic suture) at the location of the arterial contact. We also show that blocking neural conduction in the facial nerve proximal to the artificial vascular compression abolishes the abnormal muscle contraction, which supports the assumption that the anatomical location of cross-transmission that is causing the abnormal muscle response is central to the vascular compression, most likely in the facial motonucleus. These findings may explain why the facial nerve is only susceptible to vascular compression near its REZ, where an injury to its myelin is more likely to occur than where the nerve is covered with schwann cell myelin.

Animals↗
PubMed1994

[Value of the monitoring of the facial nerve in the evaluation of facial function in translabyrinthine surgery for acoustic neuroma].

Amongst the 62 patients operated for acoustic neuroma using a translabyrinthine approach, the authors study post operatory results at one month of the facial function according to the "House-Brackmann" classification. The analysis consists in 2 homogeneous and comparable series of 34 and 28 patients having benefited or not of a per operatory monitoring of the facial nerve with "NIM 2" neuro monitor. Without distinction of the tumoral sizes 76% of patients show a good facial result when monitorized against 60.7% when not. According to the tumoral size monitoring becomes more interesting: also you will find better results in the monitorized serial (71%) against 29% without. Other factors concerning the facial post operatory functions are also analysed by authors. To the very important part of per operatory monitoring, the anatomical status, microvascularization and physiological state of the nerve al as well as the operator's experience are to be added. All above factors must be considered when evaluating the final post operatory facial result.

Adult↗
PubMed2000

High-resolution computed tomography using multiplanar reconstruction for the facial nerve canal.

Multiplanar reconstruction (MPR) images along the facial nerve canal were prepared with high-resolution computed tomography (HRCT) and their clinical usefulness was evaluated. Over a period of 6 years, temporal bone HRCT was performed on 628 cases. Of these cases, 6 patients exhibited facial nerve lesions, including facial nerve schwannoma (n = 3), traumatic facial nerve palsy (n = 2) and congenital facial nerve palsy (n = 1). Thirty patients without facial nerve lesions, such as chronic otitis media, were randomly selected as controls. Two types of MPR image were composed. One was along the labyrinthine and tympanic segment, and the other was along the tympanic and mastoid segment. Other MPR images, such as those along the facial nerve canal and bone fracture line, were composed as needed. All MPR images were prepared with real-time observation of delicate angles. In all cases, MPR images delineated the labyrinthine and tympanic segment in one image, and the tympanic and mastoid segment in another image. In two patients with traumatic facial nerve palsy, the MPR images revealed a relationship between the facial nerve canal and the bone fracture. In conclusion, MPR images of the facial nerve canal are easy to obtain and are useful in detecting facial nerve schwannoma, traumatic facial nerve palsy and congenital facial nerve palsy.

Adolescent↗
PubMed1999

Facial nerve function after petrosectomy.

OBJECTIVES: Evaluation of facial nerve function after petrosectomy in a patient series with facial nerve denudation-decompression, forward or backward rerouting, and facial nerve suture and grafting. STUDY DESIGN: Fifty-six patients with petrosectomies performed for 24 benign and 9 malignant tumors of the petrous bone, 13 malignant tumors of the parotid gland or of the infratemporal spaces with infiltration of the petrous bone, 8 traumatic facial nerve disruptions, and 2 osteoradionecroses were retrospectively evaluated with respect to facial nerve function. Sixteen cases involved a partial, 25 a subtotal, and 15 an extended subtotal petrosectomy. METHODS: The treatment of the facial nerve included 15 denudation-compressions, 23 denudation-compressions with rerouting, 4 primary sutures, and 14 nerve grafts. The House-Brackmann grading system was used for facial nerve evaluation. RESULTS: Normal or nearly normal facial nerve function was obtained in facial nerve denudation-decompression with and without rerouting (House-Brackmann Grade I or II) except in cases of malignant tumors and osteoradionecrosis, where preoperative impaired function remained. Satisfactory results were obtained with nerve suturing and nerve grafting after petrous bone fracture (Grade III or IV, in one case practically Grade II) except in a case of late repair 3 years after the trauma (Grade V). Variable results were obtained with nerve grafting in cases with tumor infiltration: Satisfactory results (5 of Grade III or IV) were obtained when the tumor was healed and also when postoperative radiotherapy was applied; poor results were obtained in the case of tumor recurrence (6 of Grade V or VI). CONCLUSIONS: Our results show that petrosectomy with denudation-decompression of the facial nerve with or without rerouting usually results in a normal mimic of the face. When the facial nerve is disrupted by trauma or when the nerve is infiltrated by tumor, early reconstruction with nerve suture or grafting mostly leads to a partial and quite acceptable reinnervation of the face.

Adult↗
PubMed2005

Facial nerve rerouting in skull base surgery.

Facial nerve rerouting techniques were developed to facilitate re-section of extensive tumors occupying the skull base. Facial nerve rerouting has its own limitations and risks, requiring microsurgical expertise, additional surgical time, and often some degree of facial nerve paresis. This article presents different degrees of anterior and posterior facial nerve rerouting, techniques of facial nerve rerouting, and a comprehensive review of outcomes. It then reviews anatomic and functional preservation of the facial nerve in acoustic neuroma resection, technical aspects of facial nerve dissection, intracranial facial nerve repair options, and outcomes for successful acoustic neuroma surgery.

Cranial Fossa, Middle↗
PubMed2002

Facial reanimation by cross-facial nerve grafting: report of five cases.

Facial nerve repair is a dynamic reanimation technique. Direct nerve repair by suturing or grafting can provide good results within a specific time frame. Immediate nerve repair has been successful in cases of laceration injuries, but nerve grafting techniques are typically delayed when it is clear that direct suturing to the nerve trunk cannot be achieved without tension. Delayed nerve grafting is also employed following ablative procedures and in cases of trauma that cause segmental nerve deficits. Cross-facial nerve grafting is particularly useful when the peripheral branches are intact and the main trunk of the facial nerve is inaccessible. This method is also typically performed in a delayed fashion. Rehabilitation of the facial nerve and subsequent reinnervation of the mimetic motor endplates are achieved through axonal growth. In this article, we describe a consecutive series of five patients who developed facial paralysis following cranial surgery for acoustic neuroma. Each underwent successful cross-facial nerve grafting during the first week following their initial surgery. Each received a sural nerve graft to at least two main divisions of the VIIth cranial nerve. We discuss our operative technique and the degree of restored nerve function.

Adult↗
PubMed1989

Effect of electrical stimulation of the superior laryngeal nerve on respiratory-modulated facial nerve activity in cats.

The purpose of the present study was to evaluate the response of respiratory-modulated facial nerve to electrical activation on the superior laryngeal nerve (SLN). The experiments were performed on fifteen cats which were anesthetized with pentobarbital, vagotomized, paralyzed and artificially ventilated. The animals were maintained at different levels of carbon dioxide in hyperoxia. Parameters of electrical stimulation were 20 Hz of frequency, 0.5 mSec of duration and a variety of intensity (30, 50, 100 and 150 microA). Facial activity increased significantly (P less than 0.05) in response to SLN activation. This augmentation of facial discharge was proportional to the intensity of electrical activation on the SLN. Phrenic response to SLN stimulation was either decreased or not changed. Total duration of respiratory cycle after activation of the SLN was increased. The results showed that facial activity may play a role in the regulation of nasal resistance.

Animals↗
PubMed1993

Rabbit facial nerve regeneration in NGF-containing silastic tubes.

Previous reports suggest that exogenous nerve growth factor (NGF) enhanced nerve regeneration in rabbit facial nerves. Rabbit facial nerve regeneration in 10-mm Silastic tubes prefilled with NGF was compared to cytochrome C (Cyt. C), bridging an 8-mm nerve gap. Three weeks following implantation, NGF-treated regenerates exhibited a more mature fascicular organization and more extensive neovascularization than cytochrome-C-treated controls. Morphometric analysis at the midtube of 3- and 5-week regenerates revealed no significant difference in the mean number of myelinated or unmyelinated axons between NGF- and cytochrome-C-treated implants. However, when the number of myelinated fibers in 5-week regenerates were compared to their respective preoperative controls, NGF-treated regenerates had recovered a significantly greater percentage of myelinated axons than cytochrome-C--treated implants (46% vs. 18%, respectively). In addition, NGF-containing chambers reinnervated a higher percentage of myelinated axons in the distal transected neural stumps (49% vs. 34%). Behavioral and electrophysiologic studies demonstrated spontaneous and induced activities in the target muscles when approximately one third of the myelinated axons were recovered in the midchamber (1280 axons). Horseradish peroxidase (HRP) studies demonstrated retrograde axonal transport to the midchamber and proximal transected neural stump. PC12 bioassay demonstrated persistent NGF activity in the intrachamber fluids at 3 (5:1 dilution) and 5 (2:1 dilution) weeks of entubation. Electrophysiologic tests demonstrated a slow conduction velocity of a propagated electrical impulse (43.5 m/s-1 vs. 67 m/s-1) and shallow wide compound action potential. In wider defects (15-mm chambers) and longer entubation periods (7 weeks), no regeneration or NGF activity was seen. Therefore, exogenous NGF provides an early but limited neurotrophic effect on the regeneration of the rabbit buccal division of the facial nerve and a limited behavioral and physiological improvement in the target muscles.

Animals↗
PubMed1995

Use of botulinum toxin to prevent facial nerve stimulation following cochlear implantation.

Facial nerve stimulation can develop because of the electric fields generated from an activated cochlear implant. This problem can usually be ameliorated by reducing or eliminating the current through the electrodes causing the undesirable stimulation. Occasionally there may be numerous electrodes that have to be deactivated in order to eliminate the facial nerve stimulation, and this may result in a marked reduction of auditory benefit to the cochlear implant user. Botulinum toxin causes transient neuromuscular blockade and has been shown to be effective in reducing or eliminating facial nerve hyperactivity due to a variety of causes. This report details the use of botulinum toxin in a patient with a cochlear implant who developed excessive facial nerve stimulation that necessitated the deactivation of 15 of the implant's 22 electrodes. After treatment with botulinum toxin, twice as many electrodes could be comfortably activated without causing facial nerve stimulation. The dynamic range was increased in 4 of the remaining 6 electrodes that were activated prior to treatment. The patient reported a marked improvement in sound quality and understanding of speech without lipreading as compared to her pretreatment performance. Treatment with botulinum toxin appears to be useful for patients who have excessive facial nerve stimulation after cochlear implantation.

Botulinum Toxins↗
PubMed1996

Laser decompression of the facial nerve.

Laser decompression of the facial nerve is an experimental approach to evaluating the parameters for laser usage at a nerve-bone interface. This article summarizes the anatomic considerations and indications for facial nerve decompression, and the advantages and disadvantages of laser decompression of the facial nerve. Preliminary studies using the Vanderbilt free electron laser are described, and future directions for research are outlined.

Electrons↗