Ethanol-Induced Cervical Sympathetic Ganglion Block Applications for Promoting Canine Inferior Alveolar Nerve Regeneration Using an Artificial Nerve

This method can help answer key questions about nerve regeneration in the artificial organ field using an artificial nerve conduit. The main advantage of this technique is that the piezoelectric surgery can be used for inferior alveolar nerve reconstruction to avoid nerve and blood vessel damage. The implications of this technique extend towards treatment of orofacial neuropathy, as it has the potential to promote nerve regeneration.

After confirming anesthesia by a lack of response to pedal reflex, apply gel over the anterior surface of the eyes to avoid corneal abrasion. Place the dog in the right lateral position. Use a 27-gauge needle to inject three milliliters of 1%lidocaine into the left mandibular gingiva.

Next, use a number 15 scalpel blade to make a five-centimeter transverse incision in the left mandibular gingiva to expose the mandibles. Use piezoelectric ultrasonic vibrations at a 28-to 32-kilohertz frequency to grind the proximal aspect of the mandible into a three-centimeter by eight-millimeter rectangle through the posterior mental foramen. As the inferior alveolar nerve is located within the mandibular canal and surrounded by bone, we use piezoelectric surgery which consists of ultrasonic waves for the bone processing to minimize the risk of nerve and vessel injury.

Remove the frontal part of the mandibular bone plate to expose the left inferior alveolar nerve. Use a scalpel to transect the inferior alveolar nerve to allow removal of a 10-millimeter segment. Insert the proximal and distal stumps of the severed nerve into a nerve tube to a depth of two millimeters.

Use 8-0 nylon sutures and a surgical microscope at an 8X magnification to suture the tube to the proximal and distal nerve ends. Then, return the bone plate to its original site in the mandible, and close the wound with 4-0 nylon sutures. One day after surgery, perform computed tomography imaging of the facial bone under anesthesia to confirm that the mandibular bone plate is in its proper position.

One week after the reconstruction procedure, shave the surgical field. Then, draw an incision line on the left side of the surgical area, and use a 21-gauge needle to inject five milliliters of 1%lidocaine into the shaved chest as a local anesthetic and analgesic. Using a number 10 scalpel blade, make an incision over the marked line, and use an electric scalpel to incise the fat layer to expose the muscle fascia.

Expose the serratus ventralis and scalenus muscles. Raise the muscles from ventral to dorsal to expose the second and third ribs. Perform a left lateral thoracotomy at the second and third intercostal space to expose the left cervical sympathetic ganglion.

Use a 30-gauge needle to inject 2 milliliters of 99.5%ethanol into the cervical sympathetic ganglion. The cervical sympathetic ganglion is degeneratively changed by ethanol. Then, close the intercostal space with interrupted 1-0 absorbable stitches.

Close the skin with interrupted 3-0 nylon stitches, and measure the facial skin temperature with infrared thermography one week after the cervical sympathetic ganglion block, or CSGB. At three months post-reconstruction, the polyglycolic acid-collagen tube at the reconstruction area is absorbed, and regeneration of the inferior alveolar nerve is observed in both the reconstruction-only and reconstruction-plus-CSGB groups. The sensory nerve action potential is also measurable in both reconstruction sides of the reconstruction-plus-CSGB and nerve reconstruction groups, with a significantly higher recovery index and sensory nerve conduction velocity observed in the reconstruction-plus-CSGB animals than in the reconstruction-only group.

Myelinated nerve fibers are observed at the central and distal segments of the regenerated inferior alveolar nerve in the reconstruction-only and reconstruction-plus-CSGB groups, although both groups demonstrated smaller regenerated myelinated nerve diameters compared to the normal control group. The presence of regenerated axons and Schwann cells is further confirmed at the central and distal segments of reconstruction-plus-CSGB groups by staining with anti-neurofilament and anti-S100 antibodies, respectively. Morphological analysis reveals a significantly higher myelinated nerve fiber density and nerve tissue percentage in both the center and distal segments of the regenerated left inferior alveolar nerve in the CSGB group compared to the reconstruction-alone animals, with a significantly smaller G-ratio observed with the CSGB procedure.

Cervical sympathetic ganglion block results in an improved nerve regeneration, suggesting that an increased blood flow effectively promote nerve regeneration. This technique contributes to the development of research in the field of in situ tissue engineering for exploring surgical treatment for the orofacial neuropathy using an artificial nerve.