CC
A 59-year-old female presents to your office for evaluation of numbness of her lower lip with pain that she reports as “consistent with episodes of very severe pain.”
HPI
The patient had root canal therapy (RCT) on tooth #29 completed about 4 months earlier. She said that the dentist performed it in two visits, and after the first visit, she developed a painful sensation, which worsened over the first several days. The dentist prescribed her antibiotics and a steroid course and completed the root canal treatment several weeks later. The painful sensation was never relieved, but instead the patient developed numbness in her lower teeth, lower lip, and chin area on the right side. She describes the painful sensation as always present at some basal level, which changes daily but also has episodes of very severe pain she describes as “stabbing” and “electrical.” The frequency of these severe pain episodes varies on a day-to-day basis and she has not been able to figure out any particular factors that may exacerbate it. She is very worried about what may happen without any treatment because she has had no improvement. Her primary care physician prescribed her gabapentin and tapered her up to a dosage of 300 mg three times daily, but she could not tolerate the side effects for only modest improvement in her discomfort.
PMHX/PDHX/medications/allergies/SH/FH
The patient reports only hypothyroidism, which is being controlled using levothyroxine, and osteoporosis, for which she is only taking vitamin D and calcium supplementation. Her surgical history is only significant for breast augmentation and hysterectomy. She has no drug allergies. She is a nonsmoker and only drinks alcohol socially.
Examination
General. The patient is a well-developed, well-nourished adult female with a nontoxic appearance. She has normal mentation and shows moderate signs of distress because today is a “bad day.”
Vital signs. Temperature is 98.9°F, blood pressure is 116/72 mm Hg, pulse rate is 85 bpm, and respiratory rate is 12 breaths per minute.
Maxillofacial. No significant extraoral edema or erythema noted. Her neck shows full range of motion. There is no remarkable lymphadenopathy on palpation. The inferior border and angle of the mandible are easily palpable and nontender. No abnormalities in facial animation and no gross asymmetries are noted.
Cranial Nerves
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Level A: Right side brush stroke: 0 of 4. Left side brush stroke: 4 of 4. Two-point discrimination: Right: Unable to feel. Two-point discrimination: 3 mm
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Level B: Right: 4.56. Left: 1.65
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Level C: Right: no response; left: normal response
For a surgeon evaluating the status of a nerve, a set of standardized tests can be used to quantify level of nerve dysfunction, and they should be done comparing the affected nerve with an unaffected nerve as similar as possible (e.g., testing the affected right inferior alveolar nerve [IAN] should be compared with the unaffected left IAN). These tests differentiate between injuries affecting different nerve fibers because the different fibers transmit various stimuli. Painful sensation is difficult to quantify because interpretation of painful sensation is very subjective: what stimulus evokes a response in one person may not evoke the same response in another person. This is contrasted with diminished normal sensation in that the standardized set of tests can quantify the level of sensation present.
Imaging
The patient’s panoramic radiograph shows a speckled radiopacity surrounding the mandibular canal and apex of tooth #29 ( Fig. 30.2 ). Panoramic radiograph is a good initial screening for IAN injuries, but further characterization may be obtained using cone-beam computed tomography. The role for magnetic resonance neurography shows promise in evaluating injuries to the peripheral trigeminal nerve, however the widespread use is limited by the abilities for this imaging protocol to be performed at local facilities.
Labs
Evaluation of a patient with an injury to the peripheral trigeminal nerve has no requirement for lab work. If surgical intervention is indicated, preoperative labs may be necessary.
Assessment
Anesthesia dolorosa secondary to endodontic IAN injury.
Treatment
This patient was treated with exploration of the right IAN, with the surgeon finding revealing a neuroma-in-continuity ( Fig. 30.3 ). The neuroma was resected, direct neurorrhaphy was performed, and the repair was entubulated ( Fig. 30.4 ) with an amnion-chorion membrane (Axoguard, Axogen Inc.). Surgical access was achieved through a buccal vestibular incision followed by a buccal corticotomy to access the proximal IAN, and the mental foramen was removed to allow for full access to this injury. Often if the injury is more proximal along the nerve, then the mental foramen will not need to be accessed ( Fig. 30.5 ). By releasing the nerve from the foramen, it may allow for direct coaptation and neurorrhaphy without an interposition nerve allograft.
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