Association between regional idiopathic neuropathy and salivary involvement as the possible mechanism for oral sensory complaints

The idiopathic sensorial disturbances of burning mouth syndrome (BMS), taste disturbances (dysgeusia), and dry mouth (xerostomia) have recently been recognized as one entity and given the generic name of oral sensorial complaints (OSC). However, not all patients with OSC complain of all three disturbances, and the underlying mechanism of OSC has not yet been elucidated. This study sought to determine whether OSC was associated with the alteration of oral sensory perception, salivary profile and/or personality traits. It examined 35 patients with OSC and 19 controls. Sensory perception was assessed by Quantitative Sensory Testing (QST) applied to the tongue, including thresholds for thermal sensations and pain, and the magnitude estimation of tonic suprathreshold heat pain stimuli. The salivary profile included flow rate and compositional analysis. Personality traits were examined by both state and trait anxiety and somatization scoring. Results showed significantly elevated thermal sensory thresholds and decreased pain scores for tonic heat pain. In addition, there was an increased level of somatization in the OSC group as compared to the control group (15.1 ± 1.5 vs. 6.6 ± 2.1, respectively; P = .003). Concomitantly, altered salivary composition (elevated Na, K, Cl, Ca, IgA, and amylase concentrations) - but not salivary flow rate reduction - was observed in those patients despite their complaints of oral dryness. All parameters were similar among the patients with OSC regardless of their type of complaint. Linear regression analysis revealed that an elevated warm sensory threshold was associated with higher levels of salivary K and Cl concentrations in the patients with OSC. These findings may be attributed to a regional small fiber idiopathic neuropathy affecting oral sensation and salivary secretion in OSC. Alternatively, a primary idiopathic salivary dysfunction might cause sensory neural dysfunction at the receptor level by changing the oral cavity milieu.