Functional regeneration of the transected recurrent laryngeal nerve using a collagen scaffold loaded with laminin and laminin-binding BDNF and GDNF.

Recurrent laryngeal nerve (RLN) injury remains a challenge due to the lack of effective treatments. In this study, we established a new drug delivery system consisting of a tube of Heal-All Oral Cavity Repair Membrane loaded with laminin and neurotrophic factors and tested its ability to promote functional recovery following RLN injury. We created recombinant fusion proteins consisting of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) fused to laminin-binding domains (LBDs) in order to prevent neurotrophin diffusion. LBD-BDNF, LBD-GDNF, and laminin were injected into a collagen tube that was fitted to the ends of the transected RLN in rats. Functional recovery was assessed 4, 8, and 12 weeks after injury. Although vocal fold movement was not restored until 12 weeks after injury, animals treated with the collagen tube loaded with laminin, LBD-BDNF and LBD-GDNF showed improved recovery in vocalisation, arytenoid cartilage angles, compound muscle action potentials and regenerated fibre area compared to animals treated by autologous nerve grafting (p < 0.05). These results demonstrate the drug delivery system induced nerve regeneration following RLN transection that was superior to that induced by autologus nerve grafting. It may have potential applications in nerve regeneration of RLN transection injury.

The prognostic value of histopathology on lingual nerve neurosensory recovery after micro-neurosurgery.

OBJECTIVE: Micro-neurosurgical repair is considered in permanent nerve damage but the outcome is unpredictable. We examined if histopathologic parameters of traumatic neuromas have a prognostic value for recovery in relation to lingual nerve micro-neurosurgery. MATERIALS AND METHODS: Retrospective case study on neurosensory recovery after micro-neurosurgery. Outcome variables were as follows: pain perception, two-point discrimination, and sum score of perception, before and 12 months after micro-neurosurgery. Predictive histopathology variables included size, nerve tissue, and inflammation. Statistics are as follows: logistic and correlation analyses (P < 0.05). RESULTS: Sixty-five patients with lingual nerve damage were included in the study. Improved two-point discrimination was associated with small size of resected tissue (P = 0.0275). No normal appearing distal nerve tissue was associated with improved sum score of perception (P = 0.0185), higher final sum score of perception value (P = 0.0475) and final pain perception (P = 0.0324). Foreign body reaction was associated with no final pain perception (P = 0.0492). CONCLUSIONS: Small size, absence of distal nerve tissue, and no foreign body reaction were associated with improvement of the neurosensory functions. CLINICAL RELEVANCE: Histological parameters of the traumatic neuromas in routine preparation appeared to have some prognostic value for neurosensory functions as improvement of the neurosensory functions was associated with small size of resected tissue, no distal normal appearing nerve tissue, and no foreign body reaction.

Low risk of neurosensory dysfunction after mandibular third molar surgery in patients less than 30 years of age. A prospective study following removal of 1220 mandibular third molars.

OBJECTIVE: The study aims were to estimate the prevalence of neurosensory dysfunction (NSD) and identify risk factors for NSD after mandibular third molar (M3) removal. STUDY DESIGN: In this prospective cohort study 864 patients had their M3 removed. Age, gender, surgeon's experience, and radiographic findings were recorded and the outcome variables were NSD and data analyses. RESULTS: In 884 patients, 1220 M3 were removed. Fourteen patients reported NSD postoperatively; 10 inferior alveolar nerve (IAN) injury, 3 lingual nerve (LN) and 1 had injury to both. After 5 years the number of patients with NSD of the IAN had decreased to 5, but no change in the LN. CONCLUSION: Age and cortical line interruption were significantly associated with the risk of developing sensory dysfunction. All patients younger than 30, and 3 of 8 patients older than 30, had full recovery of the IAN injury. NSD of the LN persisted in all patients.

Fos protein-like immunoreactive neurons induced by electrical stimulation in the trigeminal sensory nuclear complex of rats with chronically injured peripheral nerve.

The rat trigeminal sensory nuclear complex (TSNC) was examined for Fos protein-like immunoreactive (Fos-LI) neurons induced by electrical stimulation (ES) of the lingual nerve (LN) at 2 weeks after injury to the LN or the inferior alveolar nerve (IAN). Intensity-dependent increase in the number of Fos-LI neurons was observed in the subnucleus oralis (Vo) and caudalis (Vc) of the spinal trigeminal tract nucleus irrespective of nerve injury. The number of Fos-LI neurons induced by ES of the chronically injured LN at A-fiber intensity (0.1 mA) was significantly increased in the Vo but not the Vc. On the other hand, in rats with chronically injured IAN, the number of Fos-LI neurons induced by ES of the LN at C-fiber intensity (10 mA) was significantly increased in the Vc but not the Vo. These results indicated that injury of a nerve innervating intraoral structures increased the c-Fos response of Vo neurons to A-fiber intensity ES of the injured nerve. A similar nerve injury enhanced the c-Fos response of Vc neurons to C-fiber intensity ES of a spared uninjured nerve innervating an intraoral territory neighboring that of the injured nerve. The present result show that nerve injury causes differential effects on c-Fos expression in the Vo and Vc, which may explain complexity of neuropathic pain symptoms in clinical cases.