The Correlation between Trigeminal Neuralgia and Local Anesthetics Neurotoxicity Associated with Acute Inflammation: A Cross-sectional Study

Trigeminal neuralgia (TN) represents a subject of importance in oral medicine due to the large number of patients complaining of TN who are aware that the orofacial pain has a dental origin and therefore seek initial care from the dentist. The reasons for the majority of TN cases remain controversial, but nearly 10% of patients have an obvious pathological condition, such as intracranial pathology.

This study aimed to assess the correlation between idiopathic trigeminal neuralgia and local anesthetic overdose and/or repeated injections caused by dental malpractice.

An adequate sample of thirty-four patients was selected from the teaching clinic of oral medicine in the College of Dentistry, the University of Karbala, Iraq. All patients were fit for the inclusion criteria and subjected to a thorough oral examination to exclude any organic diseases that cause orofacial pain. Also, they were subjected to a medical examination by multiple neurologists using magnetic resonance imaging and other medical investigations to ensure that all patients did not suffer from intracranial pathology.

The patients were statistically distributed by their ages into two sub-groups. The first group (25-48 years old) represented 52.94% of all patients, and the second group (49-72 years old) included 47.06%. The percentage of disease according to sex was 79.4% in males and 20.6% in females. 3-6 dental carpules containing lidocaine (2%) with epinephrine were given to patients. The data of the studied sample were analyzed by using the statistical package of social sciences (SPSS) version 25. The chi-square test was used to test the effect of the type of dental procedure before pain in the two age groups and the two sex groups. For the age group, the difference was significant (p-value < 0.05), which indicated an increased incidence of nerve damage caused by local anesthesia in older patients. For the sex group, the chi-square test exhibited a value of 2.45, with no significant difference (p-value > 0.05). The main theory suggested for the occurrence of local neuropathies and the initiation of TN was the demyelination of nerve, which may be due to the neurotoxic effects of local anesthesia administered at high concentrations and for prolonged exposure times (repeated injections at the site of the dental infection after failure of LA) that may activate the intrinsic pathway of apoptosis through cytochrome C release. The local anesthetic-related neurotoxicity has thus been found to have harmful effects on the nerve tissue, including demyelination and axonal degeneration.

The malpractice of local anesthesia in dentistry may lead to dysesthesia, allodynia, and trigeminal neuralgia with different degrees and severity due to the neurotoxicity of the peripheral nerve fiber. The nerve damage may occur in many forms, such as demyelination, apoptosis, axonal degeneration, and hypoxia due to thrombosis. So, dentists should recognize the risk of repeated injections or high dose solution (4%) of LA in the inflamed tissues when inducing analgesia for their dental operations that might initiate the primary trigeminal neuralgia.