Joseph Catapano

Retrograde labeling of regenerating motor and sensory neurons using silicone caps.

BACKGROUND Retrograde labeling permits the investigation of the number, distribution and axonal projections of neurons in the peripheral nervous system. The well technique for labeling peripheral nerves consists of incubating the exposed peripheral nerve in a well for one hour, a time intensive technique. However, other techniques that inject tracers directly into the nerve or muscle may result in variable labeling depending on nerve preparation and location of injection. NEW METHOD We describe a method of retrograde labeling peripheral nerves that increases tracer uptake and improves labeling efficiency. This technique utilizes a silicone cap over the nerve that is kept in place with fibrin glue, permitting closure of the incision with the cap in place, mitigating the need to wait one hour for back-labeling as with the standard well technique. RESULTS In the rat common peroneal nerve, the new silicone cap technique, compared to the standard well technique, labeled 405±11 (SEM) vs. 378±21 motoneurons and 953±40 vs. 948±57 sensory neurons. These counts were not statistically different. Labeling intensity was greater in DRG neurons with the silicone cap technique, but this difference was not evident in motoneurons. COMPARISON WITH EXISTING METHOD Retrograde-labeling with silicone caps labels an equal number of motor and sensory neurons in comparison with the standard well technique and labels sensory neurons with greater intensity. CONCLUSIONS Retrograde-labeling with silicone caps reliably labels neurons and significantly decreases the time required for labeling, reducing anesthetic exposure and improving the efficiency of the technique.

Restoration of Trigeminal Cutaneous Sensation with Cross-Face Sural Nerve Grafts: A Novel Approach to Facial Sensory Rehabilitation.

UNLABELLED Although treating facial palsy is considered debilitating for patients, trigeminal nerve palsy and sensory deficits of the face are overlooked components of disability. Complete anesthesia leaves patients susceptible to occult injury, and facial sensation is an important component of interaction and activities of daily living. Sensory reconstruction is well established in the restoration of hand sensation; however, only one previous report proposed a surgical strategy for sensory nerve reconstruction of the face with use of nerve transfers. Nerve transfers, when used alone, have limited application because of their restricted arc of rotation in the face; extending their arc by adding nerve grafts greatly expands their utility. The following cases demonstrate the early results after V2 and V3 reconstruction with cross-face nerve grafts in three patients with acquired trigeminal nerve palsy. Cross-face nerve grafts using the sural nerve permit more proximal reconstruction of the infraorbital and mental nerves, which allows reinnervation of their entire cutaneous distribution. All patients demonstrated improved sensation in the reconstructed dermatomes, and no patients reported donor-site abnormalities. Cross-face nerve grafts result in minimal donor-site morbidity and are promising as a surgical strategy to address sensory deficits of the face. CLINICAL QUESTION/LEVEL OF EVIDENCE Therapeutic, V.

In Vivo Confocal Microscopy Reveals Corneal Reinnervation After Treatment of Neurotrophic Keratopathy With Corneal Neurotization

Purpose: To document the presence and location of new sensory nerve fibers after corneal neurotization using in vivo confocal microscopy (IVCM) in 2 patients with neurotrophic keratopathy (NK). Methods: Two patients with unilateral advanced NK received corneal neurotization to surgically reinnervate the cornea. IVCM was used to identify subbasal nerve fibers and document corneal reinnervation. In 1 patient (case 1), IVCM was performed before and after corneal neurotization; in the second patient (case 2), IVCM was performed after neurotization and corneal transplantation. Results: In case 1, who had hand motion visual acuity due to NK-associated corneal perforation that necessitated cyanoacrylate gluing, preoperative IVCM identified no subbasal nerves; however, subbasal nerves were identified 6 months after corneal neurotization, and there were no further episodes of persistent epithelial defects. In case 2, in whom NK with a total absence of corneal sensation was the result of treated basal skull meningioma, corneal sensation, visual acuity, and ocular surface health improved after corneal neurotization. Deep anterior lamellar keratoplasty was performed 2.5 years after corneal sensation was reestablished. IVCM demonstrated corneal reinnervation at the stromal and subbasal level in a pattern different from the normal cornea. Conclusions: Corneal neurotization restores corneal sensation by reinnervating the stromal and subbasal layers of the cornea. In doing so, corneal neurotization may halt the process of NK and prevent further visual loss.

n -acetylcysteine Prevents Retrograde Motor Neuron Death after Neonatal Peripheral Nerve Injury

Background: Neuronal death may be an overlooked and unaddressed component of disability following neonatal nerve injuries, such as obstetric brachial plexus injury. N-acetylcysteine and acetyl-L-carnitine improve survival of neurons after adult nerve injury, but it is unknown whether they improve survival after neonatal injury, when neurons are most susceptible to retrograde neuronal death. The authors’ objective was to examine whether N-acetylcysteine or acetyl-L-carnitine treatment improves survival of neonatal motor or sensory neurons in a rat model of neonatal nerve injury. Methods: Rat pups received either a sciatic nerve crush or transection injury at postnatal day 3 and were then randomized to receive either intraperitoneal vehicle (5% dextrose), N-acetylcysteine (750 mg/kg), or acetyl-L-carnitine (300 mg/kg) once or twice daily. Four weeks after injury, surviving neurons were retrograde-labeled with 4% Fluoro-Gold. The lumbar spinal cord and L4/L5 dorsal root ganglia were then harvested and sectioned to count surviving motor and sensory neurons. Results: Transection and crush injuries resulted in significant motor and sensory neuron loss, with transection injury resulting in significantly less neuron survival. High-dose N-acetylcysteine (750 mg/kg twice daily) significantly increased motor neuron survival after neonatal sciatic nerve crush and transection injury. Neither N-acetylcysteine nor acetyl-L-carnitine treatment improved sensory neuron survival. Conclusions: Proximal neonatal nerve injuries, such as obstetric brachial plexus injury, produce significant retrograde neuronal death after injury. High-dose N-acetylcysteine significantly increases motor neuron survival, which may improve functional outcomes after obstetrical brachial plexus injury.

Corneal Neurotization Improves Ocular Surface Health in a Novel Rat Model of Neurotrophic Keratopathy and Corneal Neurotization

Purpose Corneal neurotization is a novel surgical procedure to reinnervate the cornea in patients with neurotrophic keratopathy (NK). We developed a rat model of NK and corneal neurotization to further investigate corneal neurotization as a treatment to improve maintenance and healing of the corneal epithelium. Methods Thy1-GFP+ Sprague Dawley rats were used to develop the model. Corneal denervation was performed via stereotactic electrocautery of the ophthalmomaxillary branch of the trigeminal nerve. Corneal neurotization was performed by guiding donor sensory axons from the contralateral infraorbital nerve into the cornea via two nerve grafts. Corneal imaging, including nerve density measurements and retrograde labeling were performed to validate the model. In vivo assays of corneal maintenance and repair were used to examine whether treatment with corneal neurotization improved healing in rats with NK. Results Corneal neurotization significantly increased corneal axon density in rats with NK (P < 0.01). Retrograde labeling of the cornea in rats with corneal neurotization labeled 206 ± 82 neurons in the contralateral trigeminal ganglion, confirming axons reinnervating the cornea derived from the contralateral infraorbital nerve. Corneal reinnervation after corneal neurotization improved corneal epithelial maintenance and corneal healing after injury (P < 0.01). Conclusions Donor nerve fibers reinnervate the insensate cornea after corneal neurotization and significantly improve corneal maintenance and repair. This model can be used to further investigate how corneal neurotization influences epithelial maintenance and repair in the context of NK.

Outcomes following coronary artery bypass grafting with microsurgery in paediatric patients

OBJECTIVES Paediatric coronary artery bypass grafting is indicated in cases of clinically significant and symptomatic coronary stenosis, with frequent complications occurring in the perioperative period. To reduce complications and improve outcomes of these procedures, surgical microscopes have been used at our centre with the anastomosis performed by a microvascular surgeon. The purpose of this article is to report our institutional experience in all patients who have undergone paediatric coronary artery bypass grafting procedures with and without microvascular techniques. METHODS Twenty-four patients who underwent coronary artery bypass grafting from January 2000 to May 2017 were retrospectively reviewed. RESULTS Eighteen patients underwent bypass without microvascular involvement and 6 patients required the use of microsurgical techniques. Median age at the time of operation was 9.79 and 2.02 years for the 2 groups, respectively. The median weight at the time of operation was 41.2 and 10.75 kg for the 2 groups, respectively. Procedures were performed emergently in 4 patients. Three major anastomotic complications occurred requiring reoperation, although none occurred in the microvascular group. The median follow-up was 3.40 years and 5.25 years for the 2 groups, respectively. Three patients were symptomatic at last follow-up and 2 deaths occurred, all in the non-microvascular group. All grafts were patent in both groups. There were no statistically significant differences between preoperative and postoperative ejection fraction between the groups. CONCLUSIONS Our results highlight the potential positive impact of collaboration between cardiac and microvascular surgeons during paediatric coronary artery bypass grafting procedures and the subsequent reduction in complications that may be expected.

Abstract 13: Documentation Of Improved Ocular Surface Health After Corneal Neurotisation And Reinnervation Using Magnetoencephalography And Histology

RESULTS: In vivo, Fmod mouse wounds representing a lost-of-function model presented markedly increased myofibroblasts after wound closure compared with wild-type (WT) controls. Intradermal injection of FMOD representing gain-of-function models led to significantly decreased myofibroblast accumulation in the wound areas of multiple animal species, including WT mice and Fmod mice, rats and pigs with high-mechanical loading wounds. Moreover, FMOD injection significantly stimulated Il1β expression, which likely contributed to the diminished number of myofibroblasts. In vitro, FMOD alone stimulated myofibroblast (but not fibroblast) apoptosis as effectively as IL1β. Remarkably, even in the presence of TGFβ1 that completely blocked the effect of IL1β, FMOD promoted myofibroblast apoptosis. Meanwhile, IL1 receptor antagonist (IL1RA) fully rescued myofibroblasts from FMOD-induced apoptosis and blocked FMOD-stimulated myofibroblast IL1β expression. Thus, FMOD selectively promoted apoptosis of myofibroblasts but not fibroblasts via an IL1β-dependent pathway.

Serial estimation of motor unit numbers using an implantable system following nerve injury and repair in rats

Motor unit number estimation (MUNE) is an established technique to assess recovery following peripheral nerve injury. In rats, where the vast majority of peripheral nerve research is conducted, assessing motor units at various time points requires a terminal procedure due to the invasive nature of current techniques. Here, we present an implanted system that was used to serially assess MUNE after peripheral nerve injury and repair in rats. This system significantly increases the efficiency of peripheral nerve research by negating the need for terminal procedures, allowing for serial MUNE assessment over time in the same rat. Our system utilizes a commercial implantable stimulator, custom designed cuff electrode, and corresponding custom software with automatic M-wave classification to quickly assess functional reinnervation up to 8 weeks following nerve injury and repair. The concepts presented in this paper are applicable to any implanted device with a transcutaneous radio frequency or inductive link that can be used to trigger nerve stimulation. The methodology is also applicable to researchers without access to implantable devices.Motor unit number estimation (MUNE) is an established technique to assess recovery following peripheral nerve injury. In rats, where the vast majority of peripheral nerve research is conducted, assessing motor units at various time points requires a terminal procedure due to the invasive nature of current techniques. Here, we present an implanted system that was used to serially assess MUNE after peripheral nerve injury and repair in rats. This system significantly increases the efficiency of peripheral nerve research by negating the need for terminal procedures, allowing for serial MUNE assessment over time in the same rat. Our system utilizes a commercial implantable stimulator, custom designed cuff electrode, and corresponding custom software with automatic M-wave classification to quickly assess functional reinnervation up to 8 weeks following nerve injury and repair. The concepts presented in this paper are applicable to any implanted device with a transcutaneous radio frequency or inductive link that can be used to trigger nerve stimulation. The methodology is also applicable to researchers without access to implantable devices.

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.