Fascicular turnover flap in the reconstruction of facial nerve defects: an experimental study in rats

Fascicular Turnover Flap: An Approach for Facial Nerve Reconstruction

ABSTRACT

Facial nerve injuries are a common complication associated with parotidectomy. These functionally debilitating injuries are conventionally treated with nonvascularized nerve grafting; however, this reconstructive modality produces moderate donor site morbidity and has limited efficacy for repairing large defects. In addition, nonvascularized nerve grafts are highly susceptible to radiotherapy and require a well-vascularized wound bed to produce adequate therapeutic results. The fascicular turnover flap, described by Koshima et al, utilizes a single fascicle to bridge two nerve endings that are in series with no donor site morbidity. Although studies have demonstrated this technique's efficacy, there is a paucity of data regarding its use in patients undergoing facial nerve reconstruction. Herein, we describe our early clinical experience using the fascicular turnover flap to reconstruct branches of the facial nerve in patients undergoing extensive parotidectomy. Our patients underwent successful reconstruction of the nerve defects produced by parotidectomy using the fascicular turnover flap. Despite postoperative radiotherapy, both patients demonstrated complete functional recovery at six months postoperatively. Although formal head-to-head studies are needed to compare the outcomes of this technique versus conventional nerve grafting for facial nerve reconstruction, our preliminary experiences suggest that the fascicular turnover flap is a viable modality of reconstruction with great potential.

Better nerve regeneration with distally based fascicular turnover flap than with conventional autologous nerve graft in a rat sciatic nerve defect model

The authors hypothesize that a fascicular turnover flap will achieve better nerve regeneration in nerve gap repair than a conventional nerve graft in a rat sciatic nerve defect model. Seven-millimeter-long sciatic nerve defects were repaired with an autologous nerve graft, a proximal fascicular turnover flap, or a distal fascicular turnover flap. Following walking footprint analysis 8 weeks after the surgery, the gastrocnemius-soleus muscles of the hind limbs, nerve graft, and flaps were harvested for wet muscle weight assessment, immunohistochemistry, and transmission electron microscopy. The distal fascicular turnover flap exhibited improvement in the sciatic function index similar as that observed for the autologous nerve graft. Histologically, cross sections showed a higher staining intensity for S-100 in the distal fascicular turnover flap group than for S-100 in the nerve graft group (p = 0.01). In the longitudinal sections, the staining intensity for NF-200 was higher in the distal fascicular turnover flap group than in the nerve graft (p = 0.009) and proximal fascicular turnover flap (p = 0.004) groups. More mature capillaries were observed in the proximal (p < 0.001) and distal (p = 0.029) fascicular turnover flap groups than in the nerve graft group. Transmission electron microscopy results showed a compact, regular myelin sheath around the myelinated nerve fibers in the distal fascicular turnover flap group, unlike observations in the nerve graft and proximal fascicular turnover flap groups. This study demonstrates better nerve regeneration in nerve gap repair with the distal fascicular turnover flap than with the conventional nerve graft.