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

Preservation of the Nerve to the Mylohyoid Muscle During Submental Island Flaps: An Anatomic Feasibility Study for Facial Nerve Reanimation Procedures

The submental island flap is an axial pattern pedicle flap widely used in head and neck surgery because of its ease and success. Indications of the submental island flap range from reconstruction for the malignant tumor resection to loss of temporal bone and facial skin due to trauma. Whereas, intraoperative facial nerve injury is not uncommon. We verified whether it was possible to localize the nerve to the mylohyoid muscle and reanimate the facial nerve during submental island flap procedures by preserving the mylohyoid muscle using human fresh cadaveric specimens. Six cadaveric heads were dissected and the position of the nerve to the mylohyoid muscle identified to the mylohyoid triangle documented. We identified the nerve to the mylohyoid muscle on all sides within the mylohyoid triangle and were able to separate the nerve from the submental island flap completely. Our results suggest that facial nerve reanimation using the nerve to the mylohyoid muscle can be used while reconstructing with a submental island flap in cases of intraoperative facial nerve injury.

Direct Hemi-Hypoglossal Nerve and Hypoglossal Nerve for Suprascapular Nerve/Proximal Brachial Plexus Neurotization: A Cadaveric Feasibility Study

Introduction Partial restoration of shoulder function is important in upper brachial plexus lesions, and the suprascapular nerve is often the target for such neurotization procedures. Although there is an extensive history of peripheral nerve surgeons using the hypoglossal nerve for various local nerve transfers, some have reported using this nerve as a donor for upper brachial plexus grafting procedures. We discuss our anatomical findings for the use of a direct hypoglossal to suprascapular nerve transfer. Materials and methods Fifteen adult cadavers (30 separate sides) were dissected to reveal the hypoglossal nerve in the neck and the supraclavicular brachial plexus in the supraclavicular region. On 15 sides, the hypoglossal nerve was dissected anteriorly to the midline, cut, and transposed toward the supraclavicular region in half of the dissections. On the remaining sides, the nerve was hemisected longitudinally into two equal parts, and the cut inferior portion also swung inferiorly toward the supraclavicular region. The cut end of the hypoglossal nerve was brought toward the proximal suprascapular nerve, the fifth (C5) and sixth (C6) cervical nerve roots, and the upper trunk. Measurements included the length and diameter of the cervical portion of the hypoglossal nerve and the diameter of the suprascapular nerve. Results The mean diameter and length of the hypoglossal nerve were 2.1 millimeters (mm) and 72.8 mm, respectively. The mean diameter of the proximal suprascapular nerve was 2.7 mm. Successful, tension-free transposition to the C5 and C6 nerve roots was achieved on all sides. The average extra length of the hypoglossal nerve for a C5 root transposition was 8 mm and 5.2mm for a C6 root transposition. The distal hypoglossal nerve reached the upper trunk on all but two sides (6.7%). The distal hypoglossal nerve reached the proximal suprascapular nerve on all but four sides (13.3%). Of the 87% of sides (n=26) where the hypoglossal nerve reached the proximal suprascapular nerve, 58% of these (n=15) required some manipulation of the suprascapular nerve from its origin at the upper trunk. This technique resulted in a mean additional length to the suprascapular nerve of 35 mm. No differences were found between the completely cut hypoglossal nerves and hemisected nerves in regard to working length. Conclusions To our knowledge, the use of the hypoglossal nerve as a transpositional graft for direct suprascapular nerve neurotization has not been previously described. Based on our study, we propose that the hypoglossal nerve, or hemi-hypoglossal nerve, should be considered as a donor nerve to restore suprascapular nerve function in the majority of patients. Additionally, the hypoglossal nerve may be transferred to the C5 and C6 roots and upper trunk of the brachial plexus for direct neurotization.

Anatomy and clinical application of suprascapular nerve to accessory nerve transfer

BACKGROUND

Loss of motor function in the trapezius muscle is one complication of radical neck dissection after cutting the accessory nerve (AN) during surgery. Nerve repair is an effective method to restore trapezius muscle function, and includes neurolysis, direct suture, and nerve grafting. The suprascapular nerve (SCN) and AN are next to each other in position. The function of the AN and SCN in shoulder elevation and abduction movement is synergistic. SCN might be considered by surgeons for AN reanimation.

AIM

To obtain anatomical and clinical data for partial suprascapular nerve-to-AN transfer.

METHODS

Ten sides of cadavers perfused with formalin were obtained from the Department of Human Anatomy, Histology and Embryology, Peking University Health Science Center. The SCN (n = 10) and AN (n = 10) were carefully dissected in the posterior triangle of the neck, and the trapezius muscle was dissected to fully display the accessory nerve. The length of the SCN from the origin of the brachial plexus (a point) to the scapular notch (b point) and the distance of the SCN from the origin point (a point) to the point (c point) where the AN entered the border of the trapezius muscle were measured. The length and branches of the AN in the trapezius muscle were measured. A female patient aged 55 years underwent surgery for partial SCN to AN transfer at Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology. The patient suffered from recurrent upper gingival cancer. Radical neck dissection was performed on the right side, and the right AN was removed at the intersection between the nerve and the posterior border of the SCM muscle. One-third of the diameter of the SCN was cut off, and combined epineurial and perineurial sutures were applied between the distal end of the cut-off fascicles of the SCN and the proximal end of the AN without tension. Both subjective and objective evaluations were performed before, three months after, and nine months after surgery. For the subjective evaluation, the questionnaire included the Neck Dissection Impairment Index (NDII) and the Constant Shoulder Scale. Electromyography was used for the objective examination. Data were analyzed using t tests with SPSS 19.0 software to determine the relationship between the length of the SCN and the linear distance. A P value of < 0.05 was considered as statistically significant.

RESULTS

The whole length of the AN in the trapezius muscle was 16.89 cm. The average numbers of branches distributed in the descending, horizontal and ascending portions were 3.8, 2.6 and 2.2, respectively. The diameter of the AN was 1.94 mm at the anterior border of the trapezius. The length of the suprascapular nerve from the origin of the brachial plexus to the scapular notch was longer than the distance of the suprascapular nerve from the origin point to the point where the accessory nerve entered the upper edge of the trapezius muscle. The amplitude of trapezius muscle electromyography indicated that both the horizontal and ascending portions of the trapezius muscle on the right side had better function than the left side nine months after surgery. The results showed that the right-sided supraspinatus and infraspinatus muscles did not lose more function than the left side.

CONCLUSION

Based on anatomical data and clinical application, partial suprascapular nerve-to-AN transfer could be achieved and may improve innervation of the affected trapezius muscle after radical neck dissection.

Can anatomical feasibility studies drive neurosurgical procedures and reach patients faster than traditional translational research?

Often, surgical techniques are practiced and studied in the anatomy laboratory. Occasionally, new surgical methods are developed with cadaveric anatomical studies. Some cadaveric feasibility studies, if published, might go on to be used by surgeons from around the world for improved patient care. Herein, we review our experience with 37 published anatomical feasibility studies over an 18-year period (2002-2020) and analyze the literature for published examples of surgical application of these same anatomical studies. We found that, for cadaveric anatomical feasibility studies within 7 years of their publication date, approximately 22% will be used in neurosurgery with the clinical applications published. Of these studies awarded clinical citation within 7 years of publication, the median time to that citation was approximately 3.4 years. As the average time for translational research to reach patient care is 17 years, cadaveric anatomical studies in this series reached patient care much sooner than traditional translational research. Cadaveric anatomical studies, based on our experience, can drive neurosurgical procedures.

Anatomical Feasibility Study of the Digastric Branch of the Facial Nerve: A Potential Donor for Facial Nerve Reanimation

PURPOSE

The digastric branch is the second branch of the facial nerve after emerging from the stylomastoid foramen. To the best of our knowledge, few detailed anatomic studies of the digastric branch have been performed. Moreover, the use of the digastric branch for facial nerve reanimation has not been explored.

MATERIALS AND METHODS

Nine sides of 5 fresh frozen cadavers were dissected for anatomic observation of the digastric branch and exploration of the feasibility of the digastric branch as a donor for facial nerve reanimation. The facial nerve trunk (FNT) and digastric branch were readily found by dissection using the tragal cartilage and tragal pointer as landmarks. The length and diameter of the digastric branch were measured, and the digastric branch was repositioned anterior to the FNT and the 2 major extracranial divisions of the FNT.

RESULTS

On all sides, the digastric branch existed as a single branch and innervated only the posterior belly of the digastric muscle. The available length of the digastric branch was 13.28 ± 2.47 mm (range, 8.87 to 16.38 mm), and the mean diameter was 0.98 ± 0.31 mm (range, 0.64 to 1.64 mm). The digastric branch reached the FNT and its 2 major divisions without tension.

CONCLUSIONS

The results of the present study have clarified the anatomic findings of the digastric branch in detail and the feasibility of using the digastric branch as a potential donor for facial nerve reanimation. The surgeon might consider the use of the digastric branch as a feasible donor for facial nerve reanimation based on the findings from our cadaveric study.

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

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

The PAN was observed on all sides. Its available length was 27.11 ± 5.02 mm and its mean diameter was 0.85 ± 0.20 mm. In all specimens, the PAN readily reached the FNT and its 2 major divisions without tension.

CONCLUSION

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.

The contralateral long thoracic nerve as a donor for upper brachial plexus neurotization procedures: cadaveric feasibility study

Object

Various donor nerves, including the ipsilateral long thoracic nerve (LTN), have been used for brachial plexus neurotization procedures. Neurotization to proximal branches of the brachial plexus using the contralateral long thoracic nerve (LTN) has, to the authors' knowledge, not been previously explored.

Methods

In an attempt to identify an additional nerve donor candidate for proximal brachial plexus neurotization, the authors dissected the LTN in 8 adult human cadavers. The nerve was transected at its distal termination and then passed deep to the clavicle and axillary neurovascular bundle. This passed segment of nerve was then tunneled subcutaneously and contralaterally across the neck to a supra- and infraclavicular exposure of the suprascapular and musculocutaneous nerves. Measurements were made of the length and diameter of the LTN.

Results

All specimens were found to have a LTN that could be brought to the aforementioned contralateral nerves. Neural connections remained tension free with left and right neck rotation of ~ 45°. The mean length of the LTN was 22 cm with a range of 18–27 cm. The overall mean diameter of this nerve was 3.0 mm. No gross evidence of injury to surrounding neurovascular structures was identified in any specimen.

Conclusions

Based on the results of this cadaveric study, the use of the contralateral LTN may be considered for neurotization of the proximal musculocutaneous and suprascapular nerves.

Comparison of facial nerve paralysis in adults and children

PURPOSE

Facial nerve injury can occur in the regions ranging from the cerebral cortex to the motor end plate in the face, and from many causes including trauma, viral infection, and idiopathic factors. Facial nerve paralysis in children, however, may differ from that in adults. We, therefore, evaluated its etiology and recovery rate in children and adults.

MATERIALS AND METHODS

We retrospectively evaluated the records of 975 patients, ranging in age from 0 to 88 years, who displayed facial palsy at Kyung Hee Medical Center between January 1986 and July 2005.

RESULTS

The most frequent causes of facial palsy in adults were Bell's palsy (54.9%), infection (26.8%), trauma (5.9%), iatrogenic (2.0%), and tumors (1.8%), whereas the most frequent causes of facial palsy in children were Bell's palsy (66.2%), infection (14.6%), trauma (13.4%), birth trauma (3.2%), and leukemia (1.3%). Recovery rates in adults were 91.4% for Bell's palsy, 89.0% for infection, and 64.3% for trauma, whereas recovery rates in children were 93.1% for Bell's palsy, 90.9% for infection, and 42.9% for trauma.

CONCLUSION

These results show that causes of facial palsy are similar in adults and children, and recovery rates in adults and children are not significantly different.