Chemosensory and somatosensory regeneration after lingual nerve repair in humans

Purpose: The objective of these studies was to measure the impact of Class IV and V lingual nerve injuries on taste sensitivity and taste receptor density of the anterior tongue before and after microneurosurgical repair. Materials and Methods: Citric acid detection threshold and suprathreshold magnitude response were measured on the anterior tongue in 12 adult volunteers with unilateral lingual nerve Class IV or V injuries. The right and left sides of the anterior tongue were tested at each session to assess the effect of nerve damage before and 1, 3, 6, and 12 months after repair. Whole-mouth threshold and suprathreshold scales of citric acid taste intensity were measured. The level of sensory impairment was scaled at each test session using a clinical neurosensory test algorithm. Finally, patients completed an 11-item instrument survey that queried the patient's perceived expectations of surgery on sensory, taste, and general health before surgery and the patient's perceived outcome of surgery at each postrepair session. The patient's perceived global satisfaction of surgery was also assessed. Results: All 12 patients failed to detect and scale citric acid and had complete or severe sensory impairment on the injured side of the anterior tongue. One year after repair, 50% of the patients demonstrated a substantial increase in the number of fungiform papillae, pores, and ratio of pores/papilla at the same time as they demonstrated the ability to detect and scale citric acid. After repair, patients perceived the greatest improvements in the categories of eating, chewing, feeling, and taste, and the least in speech. Conclusion: Lingual nerve repair may result in significant changes in somatosensory and chemosensory function and taste bud anatomy on the anterior tongue over time.