University of Khartoum

Modulation of Brainstem-Reflexes by Pain in Patients with Myofascial Temporomandibular Disorders

Modulation of Brainstem-Reflexes by Pain in Patients with Myofascial Temporomandibular Disorders

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Title: Modulation of Brainstem-Reflexes by Pain in Patients with Myofascial Temporomandibular Disorders
Author: Mohammed, Ishraga Ali Elhag
Abstract: Background: Myofascial Temporomandibular Disorders (M-TMD) are common chronic orofacial pain disorders. The underlying nociceptive mechanisms in muscles and joints are still unsettled, largely due to scarcity of studies on peripheral and central neural mechanisms affecting craniofacial musculoskeletal tissues. Trigeminal brainstem reflexes are suitable tools for assessment of trigeminal nerve fibers and their central connections in brainstem. The study aim was to use brainstem reflexes (blink reflex (BR) and masseter inhibitory reflex (MIR)) to investigate craniofacial mechanisms in M-TMD. Methods: This study was quasi experimental study, conducted at the Department of Physiology, Faculty of Medicine, University of Khartoum. A total of 66 subjects were included in the study, comprising two groups: 33 M-TMD patients and 33 controls, who were strictly matched for age and sex. Each group was formed of 14 males and 19 females with average age of 37.3 years ±10.3SD. BR and MIR were elicited using two types of stimulating electrodes; nociceptive specific and conventional paediatric electrodes. For nociceptive reflexes, stimulating current (mA) was predetermined for all participants. BR was tested by stimulation of supraorbital and mental nerves from both sides of the face using the two types of stimulating electrodes and recorded with disposable surface electrodes on both orbicularis oculi muscles. Response area (mV/ms) and latency (ms) of ipsi- and contralateral R2 component of BR were calculated. MIR was tested by stimulation of the mental nerve bilaterally using the two electrodes and recorded from both masseter muscles. The onset latency (ms) of early (SP1) and late silent periods (SP2) were measured from ipsi- and contralateral sides. Recorded data was stored for offline analysis using PC-based program. Results: Data was analysed with one way analyses of variance (ANOVA) and unpaired students T test , significance level was set (P value= 0.05). BR results: No significant differences were observed between patients and controls for supraorbital BR parameters with both conventional and nociceptive stimulation methods (P>0.05). Mental nerve BR with conventional stimulation showed nearly same results for patients and controls with P value close to 1.0 in all comparative calculations. Nociceptive mental BR latencies showed highly significant differences between patients and controls; in patients, R2 onset latencies were significantly prolonged compared with controls (P values < 0.05), response area (mV/ms) for R2 was significantly reduced in patients compared with controls (P values ≤ 0.05). MIR results: No significant differences on SPs were observed between the two groups upon conventional method (P values > 0.05). nMIR was elicited in 12 out of 33 patients, SP1 appeared in 15/33 controls, while SP2 appeared in 31/33 of them. SP2 was significantly prolonged in patients compared to controls. (P values < 0.05). Conclusion: These findings are consistent with recent clinical and experimental pain studies and suggested that chronic craniofacial pain in TMD patients may be associated with dysfunction of the trigeminal nociceptive system. These results might be helpful to improve knowledge for the diagnosis and management of M-TMDs and to explore the usefulness of brainstem reflexes in assessing various orofacial pain conditions.
Description: 131 Pages
URI: http://khartoumspace.uofk.edu/123456789/27405
Date: 2018


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