Permanent nerve involvement resulting from inferior alveolar nerve blocks.

Background: This is a prospective study of patients referred to a tertiary care center with permanent alteration in sensation of the inferior alveolar nerves, lingual nerves or both that could have resulted only from an inferior alveolar nerve block.
Methods: Working with a subject pool of 83 patients, the researchers outlined and photographed the area of altered sensation on each patient, tested it with von Frey's hairs and two-point discrimination and tested temperature sensation and direction sense.
Results: Among a study population of 55 women and 28 men with a mean age of 41.2 years, the lingual nerve was affected in 79 percent of patients and the inferior alveolar nerve in 21 percent of patients. In 47 patients, the causative inferior alveolar nerve block was painful when administered, but to the other 36 patients [corrected], it felt like a normal injection. Of the local anesthetic agents used, prilocaine was found to be more frequently linked to cases of nerve involvement in this study.
Discussion: Occasionally, an inferior alveolar nerve block can result in permanent involvement of the inferior alveolar nerve, lingual nerve or both. The incidence and exact mechanism of involvement still are unknown. By extrapolation from this study, an incidence of anywhere between 1:26,762 and 1:160,571 inferior alveolar nerve blocks can be surmised to result in this complication. A difference in referral rates for male and female patients is difficult to explain. The 34 percent [corrected] incidence of dysesthesia in the patients in this study is of concern.
Conclusion: Permanent nerve involvement after receiving an inferior alveolar nerve block is a documented but very rare complication of the inferior alveolar nerve block, and the exact mechanism involved is still unknown.
Clinical Implications: Permanent nerve damage can very occasionally occur as a result of an inferior alveolar nerve block. The exact mechanism is unknown, and there is no means of prevention. Knowledge of the risks and complications of local anesthesia is essential.