Blink Reflex In Patients Research Articles

Характеристика полисинаптической рефлекторной возбудимости ствола головного мозга у больных с экзогенно-конституциональным ожирением

The purpose — to study the characteristics of polysynaptic reflex excitability of the brain stem based on an electroneuromyographic research of the blink reflex in patients with exogenous constitutional obesity (ECO). Material and methods. 288 women (mean age 37.5 (2.8) years) with ECO and 45 healthy women of the same age group were examined. All patients underwent a clinical and anthropometric examination, including quantitative indicators of body size and weight and electroneuromyographic study of the blink reflex (BR). Results. The anthropometric study revealed the presence of two variants of fat deposition topography — android (AT) and gynoid (GT) types. The ratio of ECO-AT and ECO-GT in this sample was 41.28% and 58.72%, respectively. Patients with ECO-GT showed a significant increase in the duration of the R2 component of the BR (44.1 (1.5) ms) (p <0.01), a reduction in its latency (35.5 (0.8) ms) (p < 0.05) and a decrease in the threshold (1.9 (0.1) mA) (p < 0.01) compared to the indicators of healthy subjects. A direct significant correlation was found between the level of polysynaptic reflex excitability and the level of obesity (r = 0.75, p < 0.05). The data obtained characterize the role of a lack of inhibition processes in the central nervous system and a functional deficit of the sensorimotor component in the ECO development mechanisms, with a disorder of autonomic nervous system and behavioural and emotional disorders, including eating behavior. As the degree of obesity increases, as well as with a more unfavorable pathogenetic type of ECO, the severity of changes in polysynaptic reflex excitability of the brain stem also increases. Conclusions. The study of polysynaptic reflex excitability of the brain stem by electroneuromyographic BR testing shows the role of dysfunction of the CNS suprasegmental parts in the ECO development and progression.

Investigating the Blink Reflex Abnormality in Dry Eye Patients.

Introduction Dry eye is an ocular surface disorder caused by increased evaporation, decreased tear production, or mixed form. Tears are secreted by the lacrimal gland after lacrimal nerve stimulation connected to the facial nerve.In nerve damage, tear secretion decreases, and dry eye develops. Our aim is to investigate the presence of pathology in the facialtrigeminal nerveand neuronal pathways that provide reflex connections between these nerves by measuring the blink reflex in patients with dry eyes. Methods Schirmer test and tear breakup time were performed. Tear breakup time measurement was repeated three times, and the average of three was accepted. Tear breakup time<10 secondsand Schirmer test <10 mm without local anesthesia were accepted as dry eye. Patients having traumatic corneal pathology, ectatic corneal disease, inflammatory and microbial keratitis, previous ocular surgery, glaucoma, diabetic retinopathy, and chronic neurological diseases were excluded. The control group was randomly formed from 42 eyes of 21 healthy volunteers. Blink reflex was measured in both groups, and the R1 and R2 responses of the two groups were compared. Written consent was obtained from the patient (or legal guardian) so that her medical data could be published. Results There was no significant difference between the two groups in R1 and R2 responses in both eyes. There was no significant difference in terms of gender between the two groups (p=0.100). The mean age in the patient group was significantly higher than in the control group (p<0.000).The mean Schirmer test in the patient group was 8.6±1.1 mm in the right eye and 8.97±1.0 mm in the left eye. Conclusion There was no central pathology observed in terms of reflex blinking in dry eye disease.However, in future studies, brainstem fiesta sequence magnetic resonance imaging (MRI) can be planned to evaluate central pathologies in more detail.

Elucidation of the mechanism underlying impaired sensorimotor gating in patients with primary blepharospasm using prepulse inhibition.

We aimed to analyze prepulse inhibition (PPI) impairment of the blink reflex in patients with primary blepharospasm (BSP). We recruited 30 BSP patients and 20 gender- and age-matched healthy controls (HCs). Weak electrical stimulation was applied to the right index finger at interstimulus intervals (ISIs) of 120, 200, and 300 ms before the supraorbital nerve stimulation to investigate PPI size [PPI size = (1 - R2 area at prepulse trials/R2 area at baseline trials) × 100%]. The prepulse stimulus significantly inhibited the R 2 component at the three ISIs in both groups, but less inhibition was shown in the BSP group (p < 0.05). In HCs, the prepulse stimulus induced prolonged R 2 and R 2c latencies at the three ISIs and increased the R 1 amplitude at ISIs of 120 ms; these changes were absent in BSP patients. In the BSP group, patients with sensory tricks showed better PPI than patients without sensory tricks. Disease duration and motor symptom severity showed no significant correlation with PPI size. In BSP patients, PPI was impaired while R 1 facilitation was absent. PPI size did not correlate with the motor symptom severity and disease duration. Patients with sensory tricks showed better PPI than those without sensory tricks.

Habituation deficit study in patients with episodic migraine thru nociceptive blink reflex

Lack of habituation is the most reproducible interictal neurophysiological phenomenon in episodic migraine. The aim of this study is to evaluate the habituation phenomenon by examining the nociceptive blink reflex in patients with episodic migraine. We conducted a cross-sectional observational case-control study. Patients with episodic migraine were selected consecutively and studied during the interictal phase. The nociceptive blink reflex was examined and a study was conducted comparing symmetry, analysis of the Euclidean distances and assessment of latency prolongation between stimulation blocks. Thirty-one patients and 16 healthy controls were included, their mean ages being 32.25 and 32.35 years, respectively. The controls displayed left-right symmetry. The Euclidean and Manhattan distances showed that the means of the block latencies of the groups are different and increase according to the number of blocks being compared. The means of the block latencies do not differ significantly in the migraine patient group, in contrast to what is seen in the healthy group. Habituation deficit was observed in the interictal phase in patients with episodic migraine compared to controls, as measured by the absence of latency prolongation in the nociceptive blink reflex.

Changes of Blink Reflex in Type 2 Diabetes Mellitus.

Blink reflex provides an objective assessment of the cranial and central nervous systems. However, the relationships between body mass index, dizziness, and BR have not been explored in patients with type 2 diabetes mellitus (T2DM). Moreover, R2 duration, one of the parameters of the blink reflex, has not been studied to date. In the present study, we aimed to investigate the characteristics and influencing factors of blink reflex in patients with T2DM. We included 45 healthy subjects and 105 hospitalized patients with T2DM. The relationships between these parameters and sex, age, body mass index, duration of T2DM, hemoglobin A1c, distal symmetrical polyneuropathy (DSPN), and dizziness symptoms were analyzed. The results showed that blink reflex latencies (including R1, ipsilateral R2, and contralateral R2 latency) were negatively associated with body mass index but were positively correlated with the duration of T2DM. There were no correlations between blink reflex parameters and sex, age, and hemoglobin A1c. Patients with DSPN had longer blink reflex latencies and shorter R2 durations than those without DSPN. Patients with dizziness had longer latencies (including R1, ipsilateral R2, and contralateral R2 latencies) and shorter R2 durations (including ipsilateral R2 and contralateral R2 durations) than those without dizziness. R2 duration was also a predictive factor for blink reflex abnormality. R2 latency was the most sensitive factor and the optimal predictor of dizziness. These results demonstrate that patients with T2DM with low body mass index, longer duration of T2DM, DSPN, and dizziness-related symptoms had more abnormal blink reflex parameters, indicating more serious injuries to the cranial nerves or the central nervous system.

Performance of blink reflex in patients during anesthesia induction with propofol and remifentanil: prediction probabilities and multinomial logistic analysis

BackgroundThe amount of propofol needed to induce loss of responsiveness varied widely among patients, and they usually required less than the initial dose recommended by the drug package inserts. Identifying precisely the moment of loss of responsiveness will determine the amount of propofol each patient needs. Currently, methods to decide the exact moment of loss of responsiveness are based on subjective analysis, and the monitors that use objective methods fail in precision. Based on previous studies, we believe that the blink reflex can be useful to characterize, more objectively, the transition from responsiveness to unresponsiveness. The purpose of this study is to investigate the relation between the electrically evoked blink reflex and the level of sedation/anesthesia measured with an adapted version of the Richmond Agitation–Sedation Scale, during the induction phase of general anesthesia with propofol and remifentanil. Adding the blink reflex to other variables may allow a more objective assessment of the exact moment of loss of responsiveness and a more personalized approach to anesthesia induction.ResultsThe electromyographic-derived features proved to be good predictors to estimate the different levels of sedation/anesthesia. The results of the multinomial analysis showed a reasonable performance of the model, explaining almost 70% of the adapted Richmond Agitation–Sedation Scale variance. The overall predictive accuracy for the model was 73.6%, suggesting that it is useful to predict loss of responsiveness.ConclusionsOur developed model was based on the information of the electromyographic-derived features from the blink reflex responses. It was able to predict the drug effect in patients undergoing general anesthesia, which can be helpful for the anesthesiologists to reduce the overwhelming variability observed between patients and avoid many cases of overdosing and associated risks. Despite this, future research is needed to account for variabilities in the clinical response of the patients and with the interactions between propofol and remifentanil. Nevertheless, a method that could allow for an automatic prediction/detection of loss of responsiveness is a step forward for personalized medicine.

Blink reflex changes and sensory perception in infraorbital nerve-innervated areas following zygomaticomaxillary complex fractures.

BackgroundInfraorbital nerve dysfunction is commonly reported after zygomaticomaxillary complex fractures. We evaluated sensory changes in four designated areas (eyelid, nose, zygoma, and lip) innervated by the infraorbital nerve. This evaluation was conducted using the static two-point discrimination test and the vibration threshold test. We assessed the diagnostic significance of the blink reflex in patients with infraorbital nerve dysfunction.MethodsThis study included 18 patients, all of whom complained of some degree of infraorbital nerve dysfunction preoperatively. A visual analog scale, the infraorbital blink reflex, static two-point discrimination, and the vibration threshold were assessed preoperatively, at 1 month postoperatively (T1), and at a final follow-up that took place at least 4 months postoperatively (T4). The results were analyzed using a multilevel generalized linear mixed model.ResultsScores on the visual analog scale significantly improved at T1 and T4. The infraorbital blink reflex significantly improved at T4. Visual analog scale scores improved more rapidly than the infraorbital blink reflex. Two-point discrimination significantly improved in all areas at T4, and the vibration perception threshold significantly improved in the eyelid at T4.ConclusionsRecovery of the infraorbital blink reflex reflected the recovery of infraorbital nerve dysfunction. We also determined that the lip tended to recover later than the other areas innervated by the infraorbital nerve.

Predictive value of neurophysiological monitoring in facial nerve function after cerebellopontine angle tumor surgery

Objective To investigate the predictive value of preoperative and intraoperative electrophysiological parameters in facial nerve (FN) function after cerebellopontine angel (CPA) tumor surgery. Methods A total of 58 patients with CPA tumor underwent operations from August 2016 to March 2017 at Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University and were enrolled into this retrospective study. Preoperative blink reflex (BR) and FN F wave response were tested in all patients. The R1 component latency and mean F wave latency were determined. Intraoperative facial motor evoked potentials (FMEP) was applied to monitor the FN function and the amplitude ratio of FMEP was documented. According to the House-Brackmann (H-B) grading system, the functional classification of FN was determined preoperatively, at 1 week, 3 months and 6 months postoperatively. Multiple logistic regression analysis was applied to explore the predictor of postoperative FN function. Results A total of 58 cases of CPA tumor underwent microsurgical excisions by retrosigmoid approach. Total and subtotal resections were performed in 55 (94.8%) and 3 cases, respectively. Single factor Logistic regression analysis showed that the results of blink reflex in patients with good FN outcome were better than those in the group with poor outcome at 3 follow-up time points (P<0.05). The results of F wave response in patients with good FN outcome were better than those in poor outcome group at 6 months post operation (P<0.05). At 3 and 6 months post surgery, the maximal tumor diameters in the good outcome group were (31.9±10.2) mm and (31.9±9.3) mm, respectively, which were smaller than those in the poor outcome group [(37.8±9.7) mm and (40.0±10.0) mm, respectively] (both P<0.05). At 1 week, 3 and 6 months post surgery, the FMEP amplitude ratios in the good outcome group were (84.6±21.3)%, (83.0±19.0)% and (81.0±19.1)%, respectively, which were higher than those in the poor outcome group [(66.2±27.0)%, (63.4±29.0)% and (59.6±31, 2)%] (all P<0.05). Multivariate Logistic regression analysis showed that FMEP amplitude ratio was the independent predictor of FN outcome at 1 week, 3 and 6 months post operation (P<0.05). The maximal tumor diameter was the independent predictor of FN outcome at 3 and 6 months post operation (P<0.05). BR classification was the independent predictor of FN outcome at 6 months after operation (P<0.05). ROC (receiver operating characteristic) curve analysis showed that the FMEP amplitude ratio cut-off values of 89.2% [AUC (area under the curve)=0.709], 58.2% (AUC=0.706) and 58.2% (AUC=0.713) predicted good FN function at 1 week, 3 and 6 months after surgery, respectively. Conclusions BR and maximal tumor diameter have certain predictive values for postoperative FN function. The FMEP amplitude ratio is a valuable predictor for postoperative FN function and its value of at least 60% is predictive of favorable long-term postoperative FN function. Key words: Cerebellopontine angle; Brain neoplasms; Facial nerve; Electrophysiology; Forecasting

Nociceptive blink reflex in patients with myofascial tempromandibular disorders (M-TMD) and healthy controls

Background: M-TMD is a common chronic orofacial pain disorder affecting tempromandibular region. The underlying nociceptive mechanisms in muscles and joints are still unsettled.

Sensory Ganglionopathy and the Blink Reflex: Electrophysiological Features.

Sensory ganglionopathy (SG) is characterised by asymmetrical sensory fibre degeneration, with the primary pathology occurring at the level of the dorsal root ganglion. It is seen in the context of autoimmune, paraneoplastic, and degenerative disorders. There is limited literature examining the electrophysiological correlate of the trigeminal ganglion and associated pathways, the blink reflex (BR), in cases of SG. Previous work has suggested that the BR is preserved in cases of SG associated with paraneoplasia. The local clinical neurophysiology database was searched for patients diagnosed with SG from peripheral nerve conduction studies in whom the BR was performed. Twenty-six patients were included in the final analysis. Sjögren's syndrome constituted the most common SG aetiology (8/26), followed by idiopathic cases (7/26) and paraneoplasia (5/26). BR abnormalities were seen in 9 of the 26 patients (34.6%) across all aetiologies. No patients reported sensory disturbance in the distribution of the trigeminal nerve, indicating that the changes noted are subclinical. Three patients showed abnormality of the R1 response; in the remaining six patients, only R2 responses were affected. Subclinical abnormalities of both R1 and R2 can be seen in the context of SG of varying aetiologies, including paraneoplasia. Performing the BR in patients with suspected of having SG may be helpful in providing additional evidence of patchy sensory fibre involvement that is characteristic of the disease.

Delay of the Blink Reflex in Patients Receiving Platinum-Analogue Chemotherapy.

ObjectiveTo investigate the presence of cranial neuropathy in patients with platinum-analogue chemotherapy using electrodiagnostic evaluations.MethodsThirty-nine patients whose chemotherapy was completed within a month and 40 control subjects were enrolled in the study. Electrodiagnostic evaluation was performed using sensory and motor nerve conduction studies and blink reflex studies, in addition to the two-point discrimination test.ResultsThe chemotherapy group had significantly longer latencies of bilateral R1 responses (left p<0.001; right p<0.001) and greater distance in two-point discrimination (p<0.001) compared to the control group. In the subgroup with peripheral polyneuropathy, the left R1 (p=0.01), both R2i (left p=0.02; right p=0.03) and the left R2c (p=0.02) were prolonged relative to those without the polyneuropathy, and both R1 (left p<0.001; right p<0.001), R2i (left p=0.01; right p=0.03), and the left R2c (p=0.01) were prolonged relative to the controls. On the other hand, the subgroup without the polyneuropathy showed only prolongation of both R1 (left p=0.006; right p<0.001) relative to the controls.ConclusionIn the present study, comparison of blink reflex and two-point discrimination showed the likelihood of subclinical cranial neuropathy following platinum-analogue chemotherapy. Cranial neuropathy caused by platinum agents was more profound in patients with peripheral polyneuropathy and may be dependent on the cumulative dose of the drug. The blink reflex may be of value in detecting subclinical cranial neuropathy in patients undergoing platinum-analogue chemotherapy.

Comparison of magnetic resonance imaging and blink reflex in patients with multiple sclerosis

Despite many new developments and studies, multiple Sclerosis (MS) is still difficult to diagnose. Magnetic resonance imaging (MRI) is an important aid in the patients clinically diagnosed as MS. Functional assessment of the patient’s symptoms increases the importance of neurophysiological methods, especially in cases with negative MRI findings. Impulse conduction in MS as a result of demyelination in the central nervous system fibers changes and delays. In this study, we compared blink reflex (BR) which is a neuropsychological methods with MRI examination. We aimed to determine the relationship between the BR abnormalities and lesion localization and their values in the diagnosis of MS. We studied 21 patients (mean age 33 ± 9 years; 7 men and 14 women) and 33 age-matched healthy subjects (mean age 34 years, 19 females and 14 males). MRI and BR were studied in all the subjects. BR showed abnormalities in 66.7% of patients and these abnormalities were apparent in the brainstem lesion. We conclude that BR, which can be easily and rapidly performed in an EMG laboratory can provide useful and objective information about in particular the brainstem lesions.

P157: Contralateral synkinesis of blink reflex in patients with hemifacial spasm

P157: Contralateral synkinesis of blink reflex in patients with hemifacial spasm

The blink reflex test does not show abnormalities in a large group of patients with chronic migraine

The blink reflex - a simple, non-invasive and inexpensive test - may be indicative of lesions or dysfunctions of the brainstem, and particularly assesses the trigeminal-facial arch. Results from alterations of the blink reflex in patients with headaches have provided controversial data. Registration of the waves R1 and R2 (ipsilateral to the stimulus) and R2c (contralateral to the stimulus) by electroneuromyography. A large number of controls (n=160) and patients with chronic migraine (n=160) were studied. No significant differences were observed between the two groups. It is possible that this relatively simple and primitive reflex is not affected unless there is significant damage to the brainstem.

Variability of the blink reflex in patients with migraine

Background and purposeSensitization of brainstem trigeminal nuclei and activation of the trigeminovascular system are thought to play an important role in migraine. The blink reflex has become a valuable tool for investigating trigeminal nerve function. The aim of the study was to assess the differences in electrophysiological examinations of the trigeminal nerve (blink reflex) in a group of patients with migraine in comparison with a healthy control group. Material and methodsThe examination was conducted among 58 patients. Patients were diagnosed in the Polyclinic or hospitalized in the Department of Neurology of Warsaw Medical University in Bielański Hospital. The study group included 29 patients suffering from migraine (diagnosed according to the International Classification of Headache Disorders, 2nd edition) and 29 patients without headaches served as controls. All patients underwent neurological examination and magnetic resonance imaging to identify organic disorders. The blink reflex was tested among all patients in accordance with electrophysiological laboratory standards. ResultsThe latency of the R1 response was significantly shorter among patients with migraine. The latency of R2 and R2’ responses was similar in patients and controls. A significant inverse correlation was observed between latency of R2 and R2’ responses and frequency of migraine attacks. ConclusionsThe inverse correlation between the frequency of attacks and the latency of R2 and R2’ responses of the blink reflex confirms the abnormal eaxcitability induced by the high frequency of migraine attacks.

Blink reflex in patients with postparalytic facial syndrome and blepharospasm: Trigeminal and auditory stimulation

ObjectiveThe enhancement of blink reflex (BR) excitability was shown in patients with postparalytic facial syndrome (PFS) and essential blepharospasm (EB). We prospectively investigated patients with PFS and EB whether BR alterations demonstrated by trigeminal stimulation will similarly be observed upon auditory stimulation. MethodsFifteen patients with PFS, 15 patients with EB, and 30 healthy volunteers were involved. Electrically stimulated trigeminal BR and auditory BR were studied bilaterally. ResultsThe mean R2 amplitude and duration values were highest in EB patients, being significantly higher than PFS patients (p<0.05) and control group (p<0.01). The mean R2 duration in PFS patients were also significantly longer in compared to control group (p=0.025). EB patients showed a higher mean R (auditory) amplitude and duration than PFS patients (p<0.05) and controls (p<0.04). The mean R (auditory) duration was longer on symptomatic side of PFS patients in compared to controls (p=0.05). ConclusionsWe observed that there is an enhanced excitability of BR circuit in postparalytic facial syndrome and essential blepharospasm, which could be evoked by auditory stimulation in addition to trigeminal stimulation. SignificanceThe enhanced excitability in patients with EB and PFS probably originates from the final common pathway of BR circuit, namely facial motor or premotor neurons.

Effect of Hypnosis on Pain and Blink Reflexes in Patients With Painful Temporomandibular Disorders

This study contrasted the effect of hypnosis on self-reported pain and changes in a nociceptive brainstem reflex, the blink reflex (BR), in 39 women with temporomandibular disorder. The patients were randomized to hypnosis or control (nonhypnotic relaxation). Pain intensity was assessed 3 times daily on a 0 to 10 numerical rating scale. BRs were elicited by electrical stimulation with a nociceptive-specific electrode and recorded before and after treatment at pain threshold (Ip) and supra threshold (2×Ip). Significant reduction of pain intensity was observed in the hypnosis group from 4.5±2.1 at baseline to 2.9±2.4 after treatment (P<0.001). The pain reduction was generally unrelated to changes in the BR, with the exception being a lowered ipsilateral R2 BR component at the right side supra threshold (P=0.034). Hypnosis thus seems to reduce complex temporomandibular disorder pain, most likely because of cortical changes with little, if any, involvement of brainstem reflex pathways.

Neurophysiological studies in alternating hemiplegia of childhood

Alternating hemiplegia of childhood (AHC) is a rare neurological disease characterised by recurrent paroxysmal attacks of hemiplegia affecting either side of the body. The clinical course is progressive, and patients develop fixed neurological deficits such as choreoathetosis, dystonia, ataxia and neurodevelopmental disturbances. The pathophysiology of this disorder is unknown, but an identifiable molecular basis, perhaps at the level of an ion channel defect, can be assumed. Diagnostic tests performed on patients and their families are usually normal. A few neurophysiological studies have yielded interesting but controversial results. Our aim was to review the results issuing from neurophysiological studies of AHC. Several reports have show that electroencephalograms are essentially normal both during the episodes and in the interhemiplegic period, except for electroencephalographic epileptic changes during seizures. The somatosensory evoked potential generated in the primary somatosensory area (N20) was absent or characterised by reduced amplitude and delayed latency during the ictal phase, but it recovered normal amplitude and latency during the interictal phase. Visual evoked potentials were decreased in the ictal phase. Motor evoked potentials and brainstem auditory evoked potentials were normal. Using blink reflex recording, several authors have reported abnormalities of both the ipsi- and contralateral R2 components of the blink reflex in patients with AHC during the interictal phase. In conclusion, neurophysiological studies have proved useful in demonstrating functional abnormalities in AHC, and thus may possibly add further elements to our present knowledge of the pathophysiology of AHC.

The application of blink reflex in diabetes mellitns

Objective To study the characteristics and clinical value of blink reflex in patients with diabetes mellitus. Methods Blink reflex were measured in 40 diabetes melletus and 30 normal adults. Results The result showed that diabetic group R1, R2 and R2' wave latency was significantly longer than the control group,meanwhile their amplitudes were significantly lower than that of control. And to 112 and R2' extended significantly,which showed that the damage to the central nervous system in diabetes can affect the brain stem. With the extension of duration of diabetes BR abnormal rate gradually increased. Conclusion It was concluded that BR provide an objective and sen-sitive index for the damage of the central nervous system in diabetes. Key words: Blinking; Diabetic neuropdthies

Blink reflexes in patients with atypical odontalgia and matched healthy controls

Atypical odontalgia (AO) is an orofacial pain condition which has been suggested to involve neuropathic pain mechanisms. The aim of this study was to use a brain stem reflex to investigate craniofacial nociceptive mechanisms in AO. In 38 AO patients and 27 matched healthy controls, the R2 component of the blink reflex (BR) was elicited using a "nociceptive-specific" electrode and recorded with surface electromyography electrodes on both orbicularis oculi muscles. The BR was tested by stimulation of both sides of the face of the participants before, during, and after an intraoral pain provocation test with capsaicin. The data were analyzed with three- and four-way mixed-model analyses of variance. The root mean square value of the ipsilateral R2 (R2i) was significantly reduced in patients compared with controls (P=0.046). No differences in R2 between stimulation sides were detected in either group (P>0.757). In all participants, R2 responses and the intensity of the pain evoked by the electrical stimulus were decreased during and after application of capsaicin compared with baseline (P<0.001). In patients, R2i onset latencies were significantly prolonged compared with controls (P=0.031). The present data show disturbances in the central processing of craniofacial information and that endogenous pain inhibitory systems in AO patients and healthy controls were activated to a similar degree by an acute intraoral nociceptive input. Additional clinical research with AO patients will be needed to determine to what extent neuropathic pain mechanisms are involved in this pain condition.