Case 2 – Facial nerve lesion and anastomosis of the marginal mandibular nerve
Keywords: Facial trauma, nerve lesion, anastomosis, mandibular marginal nerve
Authors: Magnus Avnstorp, Specialist Plastic Surgeon, Zealand University Hospital
59 years old patient sustained a blunt trauma på the left side of his face from a sliding container door. The patient sustained a deep, larger lesion to his cheek on the mandibular that was explored in the Emergency Room by a resident ortopedic surgeon and a ENT specialist surgeon. The patient described dificulties moving his mount, and the left commisura and had a changed voice. A lesion of the marginal mandibular nerve (Part of the Facial nerve) was suspected.
The attending specialist Plastic Surgeon was called for guidance. The patient was admitted for specialist care with exploration and eventually anastomosis of the marginal mandibular nerve.
The patient had a CAT scan of the face performed before admission to Plastic Surgery. The CAT scan showed no signs of bone fracture.
Before and after
Patient examination
The trauma had inflicted a deep wound with lesion through the skin, subdermal tissue and all the way into the submandubular gland. Lesion of the marginal mandibulae nerve, a part of the facial nerve wound found. We found several intact mandibular nerves and one larger nerve with a lesion.
The patient did not sustain any facial fractures, as found by CAT scan.
Pre-Operative Considerations
The wound must be throughly assessed during general anaesthesia and under a microscope or loupes to ensure all debris is removed, blood vessels are hemostasised correctly, nerves are anastomosed and the wound closed correctly in correct layers. It must be considered to use high magnification microscope in case of the need for nerve anastomosis with a 10-0 nylon suture, but loupes may be used in a less advanced setup. Other lesions and fractures must be ruled out before surgery.
Step 1: The superficial part of the trauma wound
Throughly assessment of the wound must be performed when planning for surgery. Size of the lesion is 10 x 6 cm with several skin flaps, still bleeding, indicating intact blood supply.
- Undermining of the wound with a flap covering 4-5 cm. The blood supply is found sufficient to the margin of the flap, but must be carefully assessed.
- As a thumb rule you do not excise trauma tissue in the face if any chance of tissue survival.
Step 2: Assessment under microscope
The wound is assessed in layers. Here we found both intact and severed facial nerves (marginal mandibulae nerve fibers). Recommended instruments to be used would be microinstruments, as here jewelers forceps and microsurgical needle driver.
- The wound was throughly assessed and explored in depth finding a deep lesion strecthing 5 cm in the depth to the mandibular bone and submandibular glandula. Also a deep undermining anteriorly of 3 cm was found.
- We found both antact and severed nerve fibers from the marginal mandibular nerve. All nerves were handled very carefully and spared in the further assessment.
Step 3: A lesion of the marginal mandibular nerve
In the depth of the wound a severed marginal mandibular nerve was found. The diameter is 1mm. using contrast plastic layer the an anastomisis was performed. First the nerve had to be prepared and was cut using microsurgical scissors. The anastomosed using 10-0 nylon sutures.
- Using contrast a severed nerve is found and is ready for anastomosis.
- When performing nerve anastomosis it is important to har sharp nerve ends and if possible olny suture in the perineural fascia instead of through the nerve.
- In this case there was no overstrecthing of the nerve. In case of strecthing one must consider af nerve sheath either artificial or a vein covering the suturered nerve. The nerve will over time grow and reconnect fibers.
Step 4: Anastomosis of the marginal mandibular nerve done
The nerves can be seen following anastomosis.
- We sutures the marginal mandibular nerve using nylon 10-0 sutures under a microscope with 4x magnification.
- Above both a sutures nerve and an intact nerve can be seen.
- We changed the contract to green.
Step 5: Closure in 3 layers
The wound was first closed in the SMASH plane using absorbale vicro 4-0 sutures, to avoid dead space and to protect the anastomosed nerves.
- The wound was closed in three layers. The smash was closed using vicryl 4-0 to ensure no dead space and to secure the nerve branches.
Step 6: Closure of dermal layer
Using vicryl 4-0 and 5-0 the dermal layer was sutured.
- The dermal layer was closed using vicryl 5-0 inverted sutures. The skin was sutures so it fit with the wound edges.
Step 7: Final skin closure
Using nylomn 5-0 the surviving skin flaps were sutures into correct place. Both single sutures and running suturees were used.
- The epidermal layer was closed using nylon 5-0 both single sutures and running sutures.
Post-Operative Plan
The patient started antibiotic treatment.
- When assessing wound facial wound on the mandible, always clinically assess for lesion of the marginal mandibular nerve always.
- In case of exploration and eventually suturing – always use loupes or microscope.
- Always assess for fractures and lesion of other important structures such as the parotic ductus stenosis, nerves and muscle
- Be aware not to damage the intact nerves when assessing the depth of the wound.
References
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