Extracranial Facial Nerve Research Articles

The long thoracic nerve as a donor for facial nerve reanimation procedures: cadaveric feasibility study

Injury of the facial nerve with resultant facial muscle paralysis may result in other significant complications such as corneal ulceration. To the authors' knowledge, neurotization to the facial nerve using the long thoracic nerve (LTN), a nerve used previously for neurotization to other branches of the brachial plexus, has not been explored previously. In an attempt to identify an additional nerve donor candidate for facial nerve neurotization, 8 adult human cadavers (16 sides) underwent dissection of the LTN, which was passed deep to the clavicle and axillary neurovascular bundle. The facial nerve was localized from the stylomastoid foramen onto the face, and the distal cut end of the previously dissected LTN was tunneled to this location. Measurements were made of the length and diameter of the LTN. Long thoracic nerve innervation to the first and second digitations of the serratus anterior was maintained on all sides. All specimens were found to have an LTN with more than enough length to be tunneled superiorly, tension-free to the extracranial facial nerve. Connections remained tensionless with left and right head rotation of up to 45 degrees . The mean length of this part of the LTN was 18 cm with a range of 15-22 cm. The overall mean diameter of this nerve was 2.5 mm. No evidence of injury to the surrounding neurovascular structures was identified on gross examination. To the authors' knowledge, the LTN has not been previously examined as a donor nerve for facial nerve reanimation procedures. Based on the results of this cadaveric study, the use of the LTN may be considered for such surgical maneuvers.

Suprascapular nerve as a donor for extracranial facial nerve reanimation procedures: a cadaveric feasibility study

Facial nerve injury with resultant facial muscle paralysis is disfiguring and disabling. To the authors' knowledge, neurotization of the facial nerve using a branch of the brachial plexus has not been previously performed. In an attempt to identify an additional nerve donor candidate for facial nerve neurotization, 5 fresh adult human cadavers (10 sides) underwent dissection of the suprascapular nerve distal to the suprascapular notch where it was transected. The facial nerve was localized from the stylomastoid foramen onto the face, and the cut end of the suprascapular nerve was tunneled to this location. Measurements were made of the length and diameter of the supra-scapular nerve. In 2 of these specimens prior to transection of the nerve, a nerve-splitting technique was used. All specimens were found to have a suprascapular nerve with enough length to be tunneled, tension free, superiorly to the extracranial facial nerve. Connections remained tensionless with left and right head rotation of up to 45 degrees . The mean length of this part of the suprascapular nerve was 12.5 cm (range 11.5-14 cm). The mean diameter of this nerve was 3 mm. A nerve-splitting technique was also easily performed. No gross evidence of injury to surrounding neurovascular structures was identified. To the authors' knowledge, the suprascapular nerve has not been previously explored as a donor nerve for facial nerve reanimation procedures. Based on the results of this cadaveric study, the authors believe that use of the suprascapular nerve may be considered for surgical maneuvers.

FACIAL REANIMATION BY MEANS OF THE HYPOGLOSSAL NERVE

The goal of this study was to determine the various anatomical and surgical relationships between the facial and hypoglossal nerves to define the required length of each for a nerve transfer, either by means of a classical hypoglossal-facial nerve anastomosis or combined with any of its variants developed to reduce tongue morbidities. Five adult cadaver heads were bilaterally dissected in the parotid and submaxillary regions. Two clinical cases are described for illustration. The prebifurcation extracranial facial nerve is found 4.82 +/- 0.88 mm from the external auditory meatus, 5.31 +/- 1.50 mm from the mastoid tip, 15.65 +/- 0.85 mm from the lateral end of C1, 17.19 +/- 1.64 mm from the border of the mandible condyle, and 4.86 +/- 1.29 mm from the digastric muscle. The average lengths of the mastoid segment of the facial nerve and the prebifurcation extracranial facial nerve are 16.35 +/- 1.21 mm and 18.93 +/- 1.41 mm, respectively. The average distance from the bifurcation of the facial nerve to the hypoglossal nerve turn is 31.56 +/- 2.53 mm. For a direct hypoglossal-facial nerve anastomosis, a length of approximately 19 mm of the hypoglossal nerve is required. For the interposition nerve graft technique, a 35 mm-long graft is required. For the technique using a longitudinally dissected hypoglossal nerve, an average length of 31.56 mm is required. Exposure of the facial nerve within the mastoid process drilling technique requires 16.35 mm of drilling. This study attempts to establish the exact graft, dissection within the hypoglossal nerve, and mastoid drilling requirements for hypoglossal to facial nerve transfer.

Disorganization of the Facial Nucleus after Nerve Lesioning and Regeneration in the Rat: Effects of Transplanting Candidate Reparative Cells to the Site of Injury

After the facial nerve has been damaged, functional recovery is impaired by synkinesis: the abnormal movement of part of the face during voluntary movement of another part. This is primarily because of aberrant regenerating axons that fail to reach the correct distal targets. We studied the effects of transplanting Schwann cells, mixed olfactory ensheathing cells, and S-type olfactory ensheathing cells on the histological and functional organization of the connections between the facial nucleus and distal muscles. In a control group of adult rats (n = 18), the proximal part of the extracranial facial nerve was completely severed and immediately repaired by suture. In an experimental group (n = 34), a bolus of cultured cells was applied to the cut ends before suture (Schwann cells, n = 10; olfactory ensheathing cells, n = 18; S-type cells, n = 6). A period of regeneration was permitted, after which the animals were assessed functionally by measurement of eye closure in response to a puff of air. The site of lesion and the somatotopic organization of the facial nucleus were assessed histologically, after application of different retrograde fluorescent tracers simultaneously to the buccal and temporal divisions of the facial nerve. The rate of recovery of eye closure was increased by the use of the cell transplants, but the disorganization of the facial nucleus and aberrant nerve branching were unchanged. Perhaps regenerating axons become misguided throughout the whole length of the nerve, not only at the site of the lesion, and strategies aimed at improving axon path-finding solely at the lesion site will therefore be inadequate.

High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil

To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial facial nerve, compared with surgical findings. Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery. Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases. High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours.

Anomalous relationship of the facial nerve and the retromandibular vein: A case report

A major challenge encountered in surgery of the parotid gland is the identification and protection of the facial nerve. Successful removal of a parotid neoplasm with the oncologically appropriate preservation of the facial nerve requires a thorough understanding of the anatomy of the facial nerve. Although the course of the facial nerve is relatively constant within the parotid gland, surgeons must be familiar with possible anatomic variations that place the facial nerve at higher risk during parotid surgery. A case with such anatomic variation is presented, with a review of the literature on anatomic anomalies of the extracranial facial nerve.

The extracranial facial nerve is one tough structure

The extracranial facial nerve is one tough structure

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.

Enhancement along the normal facial nerve in the facial canal: MR imaging and anatomic correlation.

Normal facial nerves are reported to show no enhancement at magnetic resonance (MR) imaging, in contradiction to the authors' clinical experience. To investigate this inconsistency, the authors searched MR imaging files and clinical records to find patients who underwent MR imaging of the temporal bone (at 1.5 T) before and after intravenous administration of gadopentetate dimeglumine and who had bilateral clinically normal facial nerves. When the MR images of 93 patients (186 facial nerves) were analyzed subjectively, 142 nerves (76%) were visibly enhanced along at least one segment of the facial nerve within the facial canal; the nerves of 64 of the 93 patients (69%) showed right-left asymmetry in enhancement, which was inhomogeneously distributed along each nerve. The facial nerve in the cerebellopontine angle cistern and in the internal auditory canal, as well as in the visualized proximal portion of the extracranial facial nerve, showed no enhancement. Comparison with reference anatomic sections showed that this enhancement pattern corresponded exactly to the topography of the circumneural facial arteriovenous plexus and should not necessarily be considered a sign of anatomic abnormality.

Transcranial Magnetic Stimulation of the Facial Nerve: Recording Technique and Estimation of the Stimulated Site

Abstract We compared transcranial magnetic and conventional electrical stimulation in 20 facial nerves of 10 normal subjects. A magnetic coil was placed tangentially over T5 or T6 (10-20 electroencephalogram electrode placement system) and electrical stimulation was applied 1 cm below the anterior tragus. Compound muscle action potentials recorded from the ipsilateral nasalis muscle showed onset latencies (mean ± SD) of 4.48 ± 0.50 ms with magnetic stimulation and 3.15 ± 0.40 ms with electrical stimulation, a mean difference of 1.33 ± 0.14 ms. Stimulation of the extracranial facial nerve at two sites yielded a conduction velocity of 59.6 ± 4.5 m/s. Based on these findings, the magnetically stimulated site was estimated to fall 79.0 ± 8.6 mm proximal to the point of electrical stimulation. Taking the average length of the nerve trunk and histological specificity of the root exit zone into consideration, evidence indicates that the root exit zone of the facial nerve is the most likely initiating site of excitation with magnetic stimulation.

Transcranial magnetic stimulation of the facial nerve

We compared transcranial magnetic and conventional electrical stimulation in 20 facial nerves of 10 normal subjects. A magnetic coil was placed tangentially over T5 or T6 (10-20 electroencephalogram electrode placement system) and electrical stimulation was applied 1 cm below the anterior tragus. Compound muscle action potentials recorded from the ipsilateral nasalis muscle showed onset latencies (mean +/- SD) of 4.48 +/- 0.50 ms with magnetic stimulation and 3.15 +/- 0.40 ms with electrical stimulation, a mean difference of 1.33 +/- 0.14 ms. Stimulation of the extracranial facial nerve at two sites yielded a conduction velocity of 59.6 +/- 4.5 m/s. Based on these findings, the magnetically stimulated site was estimated to fall 79.0 +/- 8.6 mm proximal to the point of electrical stimulation. Taking the average length of the nerve trunk and histological specificity of the root exit zone into consideration, evidence indicates that the root exit zone of the facial nerve is the most likely initiating site of excitation with magnetic stimulation.

Postauricular (12 msec latency) responses to acoustic stimuli in patients with peripheral, facial nerve palsy.

The postauricular (12 msec latency) response to a loud click stimulation was investigated in 23 patients with facial nerve palsy. Of these patients 21 had an intracranial cause for the facial palsy and 2 had an extracranial cause. Only in those with the extracranial facial nerve damage could the response be obtained from both sides. When the nerve was damaged intracranially there was no response on the paralysed side. This seems to indicate that the posterior auricular muscle is the effector of the presumed sonomotor reflex arc involving the cochlea, cochlear nerve and nuclei, undetermined brainstem pathway, facial motor nucleus, facial nerve and the muscles supplied by it.

Red chorda tympani nerve and Bell's palsy.

AbstractThis is the first report of a red chorda tympani nerve observed in association with Bell's palsy. A prospective study was designed to determine the frequency and significance of this sign in association with Bell's palsy. Twenty‐eight patients were evaluated within two days of onset of paralysis. The red chorda tympani sign was correlated with alterations in chorda tympani function in terms of taste and submandibular salivary flow as well as response of the extracranial facial nerve to the maximal stimulation test. The chorda tympani was red in 10 of 20 patients (50 percent) where the nerve could be seen through the tympanic membrane. This finding is discussed in terms of a viral‐inflammatory involvement of the chorda tympani as part of the pathogenesis of Bell's palsy. In addition, the red chorda tympani sign was clinically significant. It indicated a more severe involvement of the chorda tympani than in those patients where the nerve was normal. The patients with the finding had a greater incidence of loss of taste by history and testing. In addition, 4 of the 10 patients with a red chorda tympani on the side of the facial paralysis had a salivary flow of less than 25 percent as compared to only 1 of 10 patients with a normal chorda tympani on the ipsilateral side. The study suggested a worse prognosis for patients with a red chorda tympani, although the difference was not statistically significant. The most important clinical significance of the red chorda tympani was its exclusive association with Bell's palsy and, therefore, may be an important diagnostic sign.