Evaluation of serum neuron specific enolase levels among patients with primary and secondary burning mouth syndrome.

Introduction: Burning mouth syndrome is a painful condition of the oral cavity with ambiguous pathogenesis and diagnosis. Neuron-specific enolase is increased in several conditions including peripheral neuropathy of diabetes, ophthalmopathies, spinal cord injuries and tumors. Evidence on association of burning mouth syndrome and neuron-specific enolase is limited.

Aim: This study aims to evaluate neuron-specific enolase levels in primary and secondary burning mouth syndrome patients and compare the levels of neuron-specific enolase with associated conditions in secondary burning mouth syndrome.

Methods: One hundred and twenty-eight patients of more than 18 years of age with no gender predilection and having clinical symptoms of burning mouth syndrome and 135 healthy subjects were included. All the patients fulfilled Scala's criteria for the diagnosis of burning mouth syndrome, including "primary" (idiopathic) and "secondary" (resulting from identified precipitating factors) burning mouth syndrome patients. Blood samples were obtained from burning mouth syndrome patients. Serum neuron-specific enolase was evaluated using enzyme-linked immunosorbent assay. To compare means and standard deviations, among primary and secondary burning mouth syndrome, data was analysed with analysis of variance and multiple comparisons test.

Results: The mean age of the study participants for burning mouth syndrome and healthy subjects was 53.30 and 51.6 years, respectively. Amongst the secondary burning mouth syndrome group, 32 (25%) of the patients had menopause, 15 (11.7%) had diabetes, eight (6.2%) of the patients had nutritional deficiency, seven (5.4%) had combined diabetes, menopause, and depression, six (4.6%) had combined diabetes and depression, four (3.1%) were diagnosed with Sjögren's syndrome. A minor percentage of 2.3% (three) had gastroesophageal reflux disease, while the remaining three (2.3%) patients in the secondary burning mouth syndrome group were on anti-depressants. There was a statistically significant increase in the levels of neuron-specific enolase in primary burning mouth syndrome as compared to the secondary burning mouth syndrome and healthy groups. Among the subgroups of secondary burning mouth syndrome, diabetic individuals showed a significant increase in neuron-specific enolase level when compared with other conditions in the secondary burning mouth syndrome patients.Discussion and conclusion: The raised serum neuron-specific enolase levels in patients suffering from primary burning mouth syndrome highlight a possible neuropathic mechanism. It was also increased in the sub-group of secondary burning mouth syndrome patients having diabetes. Although it cannot be ascertained whether the deranged values in the diabetic group were due to burning mouth syndrome or due to diabetes, the raised quantity of neuron-specific enolase in the primary burning mouth syndrome group is a reliable diagnostic indicator. Future studies on the assessment of neuron-specific enolase levels as a diagnostic tool for onset and management of primary and secondary burning mouth syndrome are recommended.