Spatial and Temporal Brain Responses to Noxious Heat Thermal Stimuli in Burning Mouth Syndrome

Abstract

Burning mouth syndrome (BMS) is an idiopathic orofacial pain condition. Although the pathophysiology of BMS is not clearly understood, central and peripheral neuropathic mechanisms are thought to be involved. The authors compared brain response to noxious heat stimuli in 16 right-handed women with primary BMS and 15 sex- and age-matched right-handed healthy female controls. A thermal stimulus sequence of 32 °C to 40 °C to 32 °C to 49 °C was repeated 4 times in a cycle. Warm and noxious heat stimuli were delivered with a Peltier thermode placed on the right palm or right lower lip for 32 s each in a session. Functional magnetic resonance imaging data were obtained by recording echoplanar images with a block design. Statistical Parametric Mapping 8 software was used to analyze the data. Patients and controls both reported feeling more pain during palm stimulation than during lip stimulation. Repetition of noxious heat stimulus on the lower lip but not on the palm induced habituation in brain activity in the cingulate cortex without reduction in pain perception. Multiple regression analysis revealed a correlation between perceived pain intensity and suppression of brain activity in the anterior cingulate cortex when the repeated thermal sequence was applied at the lower lip. Furthermore, the response of the parahippocampal area differed in BMS patients and controls when the same repeated thermal sequence was applied at the palm. The authors' findings indicate that BMS patients show specific brain responses due to impaired function of the central and peripheral nervous systems (clinical trial registration: UMIN000015002).

Cold thermal oral stimulation produces immediate excitability in human pharyngeal motor cortex

“…The effect of noxious thermal stimulation on brain region in humans has been well elucidated using functional magnetic resonance imaging (fMRI) in terms of perception of pain. Noxious heat stimulation on the hand area provokes functional changes in a number of brain regions including the cingulate gyrus, prefrontal cortex, and insula . On the other hand, trigeminal nerve heat stimulation on lower lip or on the skin of cheek strongly activates the anterior brain such as premotor cortex, anterior cingulate gyrus, insula, thalamus .…”

“…Noxious heat stimulation on the hand area provokes functional changes in a number of brain regions including the cingulate gyrus, prefrontal cortex, and insula. 37,38 On the other hand, trigeminal nerve heat stimulation on lower lip or on the skin of cheek strongly activates the anterior brain such as premotor cortex, anterior cingulate gyrus, insula, thalamus. 38,39 Similarly, there have been several studies with fMRI that The MEP waveform induced by TMS on somatosensory area is approximated as a combination of interactions between circuits of inhibitory and excitatory interneurons.…”

“…37,38 On the other hand, trigeminal nerve heat stimulation on lower lip or on the skin of cheek strongly activates the anterior brain such as premotor cortex, anterior cingulate gyrus, insula, thalamus. 38,39 Similarly, there have been several studies with fMRI that The MEP waveform induced by TMS on somatosensory area is approximated as a combination of interactions between circuits of inhibitory and excitatory interneurons. 45 Trigeminal conditioning transcutaneous (sensory) stimulation demonstrated increased amplitude changes in pharyngeal MEP using paired plus TMS.…”

Burning Mouth Syndrome –Latest update

“…Image-based functional evaluation of brain is a source of additional information to understand the neural mechanisms behind the etiopathology of BMS.The sensory changes suggest that both the CNS and the peripheral nervous system are involved in the manifestation of BMS 9,28,52 .The correlation between BR and BMS was similar to that observed between BR and Parkinson's disease, which is considered one of the causes of secondary BMS 9,28 . BMS patients exhibited higher thresholds for savory, sweet, sour, and olfaction stimuli, lending strength to the idea that central sensitization is involved in the physiopathology of the disease 53 .…”

Is it Sjögren's syndrome or burning mouth syndrome? Distinct pathoses with similar oral symptoms

“…Alterations in both the central and peripheral nervous systems of BMS patients are reported using a variety of neuro-exploratory investigations 121, 122 . There are 3 subclasses of neurophysiologic pain described for BMS patients: peripheral small fiber neuropathy, subclinical major trigeminal neuropathy, and central pain possibly related to deficient dopaminergic inhibition 121, 123, 124 .…”