Baiting the cross-face nerve graft with temporary hypoglossal hookup

Electrophysiological assessment of a peptide amphiphile nanofiber nerve graft for facial nerve repair

Facial nerve injury can cause severe long-term physical and psychological morbidity. There are limited repair options for an acutely transected facial nerve not amenable to primary neurorrhaphy. We hypothesize that a peptide amphiphile nanofiber neurograft may provide the nanostructure necessary to guide organized neural regeneration. Five experimental groups were compared, animals with (1) an intact nerve, (2) following resection of a nerve segment, and following resection and immediate repair with either a (3) autograft (using the resected nerve segment), (4) neurograft, or (5) empty conduit. The buccal branch of the rat facial nerve was directly stimulated with charge balanced biphasic electrical current pulses at different current amplitudes whereas nerve compound action potentials (nCAPs) and electromygraphic responses were recorded. After 8 weeks, the proximal buccal branch was surgically reexposed and electrically evoked nCAPs were recorded for groups 1-5. As expected, the intact nerves required significantly lower current amplitudes to evoke an nCAP than those repaired with the neurograft and autograft nerves. For other electrophysiologic parameters such as latency and maximum nCAP, there was no significant difference between the intact, autograft, and neurograft groups. The resected group had variable responses to electrical stimulation, and the empty tube group was electrically silent. Immunohistochemical analysis and transmission electron microscopy confirmed myelinated neural regeneration. This study demonstrates that the neuroregenerative capability of peptide amphiphile nanofiber neurografts is similar to the current clinical gold standard method of repair and holds potential as an off-the-shelf solution for facial reanimation and potentially peripheral nerve repair.

Bilateral Facial Paralysis: A 13-Year Experience

BACKGROUND

Bilateral facial palsy is a rare clinical entity caused by myriad disparate conditions requiring different treatment paradigms. Lyme disease, Guillain-Barré syndrome, and leukemia are several examples. In this article, the authors describe the cause, the initial diagnostic approach, and the management of long-term sequelae of bilateral paralysis that has evolved in the authors' center over the past 13 years.

METHODS

A chart review was performed to identify all patients diagnosed with bilateral paralysis at the authors' center between January of 2002 and January of 2015. Demographics, signs and symptoms, diagnosis, initial medical treatment, interventions for facial reanimation, and outcomes were reviewed.

RESULTS

Of the 2471 patients seen at the authors' center, 68 patients (3 percent) with bilateral facial paralysis were identified. Ten patients (15 percent) presented with bilateral facial paralysis caused by Lyme disease, nine (13 percent) with Möbius syndrome, nine (13 percent) with neurofibromatosis type 2, five (7 percent) with bilateral facial palsy caused by brain tumor, four (6 percent) with Melkersson-Rosenthal syndrome, three (4 percent) with bilateral temporal bone fractures, two (3 percent) with Guillain-Barré syndrome, one (2 percent) with central nervous system lymphoma, one (2 percent) with human immunodeficiency virus infection, and 24 (35 percent) with presumed Bell palsy. Treatment included pharmacologic therapy, physical therapy, chemodenervation, and surgical interventions.

CONCLUSIONS

Bilateral facial palsy is a rare medical condition, and treatment often requires a multidisciplinary approach. The authors outline diagnostic and therapeutic algorithms of a tertiary care center to provide clinicians with a systematic approach to managing these complicated patients.

The Spinal Accessory Nerve for Functional Muscle Innervation in Facial Reanimation Surgery: An Anatomical and Histomorphometric Study

INTRODUCTION

Facial reanimation surgery is performed in severe cases of facial palsy to restore facial function. In a 1-stage procedure, the spinal accessory nerve can be used as a donor nerve to power a free gracilis muscle transplant for the reanimation of the mouth. The aim of this study was to describe the surgical anatomy of the spinal accessory nerve, provide a guide for reliable donor nerve dissection, and analyze the available donor axon counts.

METHODS

Dissections were performed on 10 nonembalmed cadavers (measurements of 20 nerves). Surgical anatomy of the spinal accessory nerve was described and distances to important landmarks were measured. Nerve biopsies were obtained of the main nerve trunk distal to the skull base, caudoposterior to the sternocleidomastoid muscle, proximal to the trapezius muscle and at the level of donor nerve harvest to analyze the myelinated axon count throughout the course of the spinal accessory nerve. The donor nerve length and available donor nerve axon count were the primary outcome parameters in this study.

RESULTS

The mean donor nerve length was 11.6 cm. The spinal accessory nerve was transferred to the mandibular angle without tension for ideal coaptation to the free muscle transplant. After retraction of the trapezius muscle, a small distal nerve branch that leaves the main nerve trunk at a 90-degree angle medially was used as a landmark to indicate the level of donor nerve transection. On average, 1400 myelinated donor axons were available for innervation of the gracilis muscle transplant.

CONCLUSIONS

This study gives a practical guide for spinal accessory nerve dissection for its application in facial reanimation as a motor source for the innervation of a free muscle transplant.

Cross-Face Nerve Grafting with Infraorbital Nerve Pathway Protection: Anatomic and Histomorphometric Feasibility Study

Smiling is an important aspect of emotional expression and social interaction, leaving facial palsy patients with impaired social functioning and decreased overall quality of life. Although there are several techniques available for facial reanimation, staged facial reanimation using donor nerve branches from the contralateral, functioning facial nerve connected to a cross-face nerve graft (CFNG) is the only technique that can reliably reproduce an emotionally spontaneous smile. Although CFNGs provide spontaneity, they typically produce less smile excursion than when the subsequent free functioning muscle flap is innervated with the motor nerve to the masseter muscle. This may be explained in part by the larger number of donor motor axons when using the masseter nerve, as studies have shown that only 20% to 50% of facial nerve donor axons successfully cross the nerve graft to innervate their targets. As demonstrated in our animal studies, increasing the number of donor axons that grow into and traverse the CFNG to innervate the free muscle transfer increases muscle movement, and this phenomenon may provide patients with the benefit of improved smile excursion. We have previously shown in animal studies that sensory nerves, when coapted to a nerve graft, improve axonal growth through the nerve graft and improve muscle excursion. Here, we describe the feasibility of and our experience in translating these results clinically by coapting the distal portion of the CFNG to branches of the infraorbital nerve.

Enhancement of facial nerve motoneuron regeneration through cross-face nerve grafts by adding end-to-side sensory axons

BACKGROUND

In unilateral facial palsy, cross-face nerve grafts are used for emotional facial reanimation. Facial nerve regeneration through the grafts takes several months, and the functional results are sometimes inadequate. Chronic denervation of the cross-face nerve graft results in incomplete nerve regeneration. The authors hypothesize that donor axons from regional sensory nerves will enhance facial motoneuron regeneration, improve axon regeneration, and improve the amplitude of facial muscle movement.

METHODS

In the rat model, a 30-mm nerve graft (right common peroneal nerve) was used as a cross-face nerve graft. The graft was coapted to the proximal stump of the transected right buccal branch of the facial nerve and the distal stumps of the transected left buccal and marginal mandibular branches. In one group, sensory occipital nerves were coapted end-to-side to the cross-face nerve graft. Regeneration of green fluorescent protein-positive axons was imaged in vivo in transgenic Thy1-green fluorescent protein rats, in which all neurons express green fluorescence. After 16 weeks, retrograde labeling of regenerated neurons and histomorphometric analysis of myelinated axons was performed. Functional outcomes were assessed with video analysis of whisker motion.

RESULTS

"Pathway protection" with sensory axons significantly enhanced motoneuron regeneration, as assessed by retrograde labeling, in vivo fluorescence imaging, and histomorphometry, and significantly improved whisker motion during video analysis.

CONCLUSION

Sensory pathway protection of cross-face nerve grafts counteracts chronic denervation in nerve grafts and improves regeneration and functional outcomes.

Alternatives to sural nerve grafts in the upper extremity

BACKGROUND

The sural nerve is the most common nerve graft donor despite requiring a second operative limb and causing numbness of the lateral foot. The purposes of this study were to review our experience using nerve autografts in upper extremity nerve reconstruction and develop recommendations for donor selection.

METHODS

A retrospective case series study was performed of all consecutive patients undergoing nerve grafting procedures for upper extremity nerve injuries over an 11-year period (2001-2012).

RESULTS

Eighty-six patients received 109 nerve grafts over the study period. Mean patient age was 42.9 ± 18.3 years; 57 % were male. There were 51 median (59 %), 26 ulnar (30 %), 14 digital (13 %), 13 radial (16 %), and 3 musculocutaneous (4 %) nerve injuries repaired with 99 nerve autografts (71 from upper extremity, 28 from lower extremity). Multiple upper extremity nerve autograft donors were utilized, including the medial antebrachial cutaneous nerve (MABC), third webspace branch of median, lateral antebrachial cutaneous nerve (LABC), palmar cutaneous, and dorsal cutaneous branch of ulnar nerve. By using an upper-extremity donor, a second operative limb was avoided in 58 patients (67 %), and a second incision was avoided in 26 patients (30 %). The frequency of sural graft use declined from 40 % (n = 17/43) to 11 % (n = 7/64).

CONCLUSIONS

Our algorithm for selecting nerve graft material has evolved with our growing understanding of nerve internal topography and the drive to minimize additional incisions, maximize ease of harvest, and limit donor morbidity. This has led us away from using the sural nerve when possible and allowed us to avoid a second operative limb in two thirds of the cases.

A system for delivering mechanical stimulation and robot-assisted therapy to the rat whisker pad during facial nerve regeneration

Functional recovery is typically poor after facial nerve transection and surgical repair. In rats, whisking amplitude remains greatly diminished after facial nerve regeneration, but can recover more completely if the whiskers are periodically mechanically stimulated during recovery. Here we present a robotic "whisk assist" system for mechanically driving whisker movement after facial nerve injury. Movement patterns were either preprogrammed to reflect natural amplitudes and frequencies, or movements of the contralateral (healthy) side of the face were detected and used to control real-time mirror-like motion on the denervated side. In a pilot study, 20 rats were divided into nine groups and administered one of eight different whisk assist driving patterns (or control) for 5-20 minutes, five days per week, across eight weeks of recovery after unilateral facial nerve cut and suture repair. All rats tolerated the mechanical stimulation well. Seven of the eight treatment groups recovered average whisking amplitudes that exceeded controls, although small group sizes precluded statistical confirmation of group differences. The potential to substantially improve facial nerve recovery through mechanical stimulation has important clinical implications, and we have developed a system to control the pattern and dose of stimulation in the rat facial nerve model.

A novel method of head fixation for the study of rodent facial function

The rodent vibrissial system offers an excellent model for the study of both sensory and motor function. It has been widely employed to gather data pertaining to sensory and motor function involving the 5th and 7th cranial nerves and the central nervous system. Existing methods of head fixation for precise measurements of ocular and vibrissial function involve exposing the cranium and applying dental cement from which two or more threaded rods emerge. This common approach is suboptimal, requiring a relatively complicated implantation procedure, and results in a large, chronic interface between the scalp and environmentally exposed implant material attached to the skull. Here we describe a head fixation device that is inexpensive, easy to build, less prone to infection, preserves access to the cranial midline, and permits repeated measurements over many months.