Head extensor reflex evoked by trigeminal stimulation in humans

The feasibility and technical aspects of trigemino-cervical reflex elicitation in humans under general anesthesia

OBJECTIVE

To analyze the feasibility, neurophysiological aspects, stimulation patterns, and topographic distribution of trigemino-cervical reflex (TCR) components in humans under general anesthesia.

METHODS

This prospective observational study enrolled 20 participants who underwent posterior fossa surgery, surgical proceduresin thecraniovertebral junction,or spinal cord surgery. TCR responses were simultaneously recorded in the sternocleidomastoid (SCM) and trapezius muscles after electrical stimulation of the supraorbital and infraorbital nerves. TCR responses were recorded preoperatively and intraoperatively using single-pulse and multipulse (trains of 2-7 electrical stimuli) stimulation, respectively. Two stimulus duration patterns were evaluated: 0.2-0.5 ms and 0.5-1.0 ms.

RESULTS

Intraoperatively, short- and long-latency TCR components were obtained in the SCM ipsilateral to the stimulation with variable recordability. Short-latency responses were the most commonly recorded components. A longer stimulus duration (0.5-1.0 ms) seems to favor the elicitation of TCR responses under general anesthesia.

CONCLUSIONS

Short-latency components recorded in the SCM ipsilateral to the stimulation could be regularly elicited under general anesthesia when a larger stimulus duration (0.5-1.0 ms) was applied.

SIGNIFICANCE

This is the first study to demonstrate the elicitation of TCR components in humans under general anesthesia. This neurophysiological technique can potentially optimize intraoperative neurophysiological monitoring during brainstem surgery.

Technical Aspects of Eliciting Trigeminocervical and Trigeminospinal Reflexes in Humans: A Scoping Review

SUMMARY

This scoping review aims to summarize the technical strategies for obtaining trigeminocervical reflex (TCR) and trigeminospinal reflex (TSR) responses. Studies published on TCR or TSR elicitation in humans through electrical stimulation of trigeminal nerve branches were eligible for this scoping review. The data of interest included stimulation parameters, site of stimulation, recording parameters, and the feasibility of TCR and TSR elicitation, in healthy participants. Short-latency TCR responses were regularly obtained in both anterior and posterior neck muscles after electrical stimulation of the supraorbital and infraorbital nerves under voluntary muscle activation. However, without voluntary muscle activation, we found evidence of elicitation of short-latency TCR components only in the posterior neck muscles after supraorbital or infraorbital nerve stimulation. Long-latency TCR responses were regularly obtained in the anterior and posterior neck muscles in studies that evaluated this technique, regardless of the trigeminal branch stimulation or muscle activation status. Short-latency TSR components were not obtained in the included studies, whereas long-latency TSR responses were regularly recorded in proximal upper limb muscles. This scoping review revealed key heterogeneity in the techniques used for TCR and TSR elicitation. By summarizing all the methodological procedures used for TCR and TSR elicitation, this scoping review can guide researchers in defining optimized technical approaches for different research and clinical scenarios.

Improvement in post-orthodontic chronic musculoskeletal pain after local anesthetic injections in the trigeminal area: a case series

Orthodontic treatment has been associated with chronic extraoral pain that is often resistant to common treatments such as drugs or physiotherapy, adversely affecting patients' quality of life. In this case series, we discuss the potential impact of orthodontics on chronic cervical spine pain or gonalgia and explore the long-term effect of local anesthetic injections as a possible therapeutic intervention. Six orthodontic patients with chronic cervical spine pain or gonalgia that substantially affected their quality of life were treated with injections of 0.5% procaine into individual lesions and at palpable points of tissue tension in the oral mucosa and extraoral myofascial areas. All patients in this case series reported significant improvement in their chronic pain, with no residual pain recorded at the 6-month follow-up. Injecting local anesthetic at stress points in the oral mucosal and extraoral myofascial regions may be an effective treatment for post-orthodontic neck and knee pain. Further research is required to better understand the potential benefits of this intervention for patients experiencing orthodontic-related musculoskeletal pain.

Prepulse modulation and recovery of trigemino-cervical reflex in normal subjects

OBJECTIVE

In this study, we analyzed the inhibitory control on the trigemino-cervical reflex (TCR), and whether or not prepulse modulation (PPM) has an effect on TCR. Thus, we studied the PPM of TCR. We hypothesized that TCR would presumably be under the modulatory effect after the prepulse stimulus similar to blink reflex (BR). We also studied the recovery of TCR which was previously shown.

METHODS

We included 13 healthy individuals. All subjects underwent recordings of TCR, TCR-PPM, and recovery of TCR. For TCR-PPM, a subthreshold stimulus to second finger 50 or 100 ms before the test stimulus was applied. For recovery of TCR, two stimuli at the infraorbital nerve were applied at 300, 500, and 800 ms interstimulus intervals (ISIs).

RESULTS

There was an inhibition of bilateral late responses of TCR at the ISIs of both 50 ms and 100 ms. There was no change of latencies. Full recovery of TCR did not develop even at the ISI 800 ms.

DISCUSSION

We have provided an evidence for the TCR-PPM in healthy subjects for the first time in this study. The prepulse inhibition is attributed to the functions of the pedunculopontine tegmental nucleus. Our study provides a strong indication that there are connections between pedunculopontine tegmental nucleus and trigemino-cervical circuit, which produces TCR.

Chiropractic Manipulation Increases Maximal Bite Force in Healthy Individuals

Recent research has shown that chiropractic spinal manipulation can alter central sensorimotor integration and motor cortical drive to human voluntary muscles of the upper and lower limb. The aim of this paper was to explore whether spinal manipulation could also influence maximal bite force. Twenty-eight people were divided into two groups of 14, one that received chiropractic care and one that received sham chiropractic care. All subjects were naive to chiropractic. Maximum bite force was assessed pre- and post-intervention and at 1-week follow up. Bite force in the chiropractic group increased compared to the control group (p = 0.02) post-intervention and this between-group difference was also present at the 1-week follow-up (p < 0.01). Bite force in the chiropractic group increased significantly by 11.0% (&plusmn;18.6%) post-intervention (p = 0.04) and remained increased by 13.0% (&plusmn;12.9%, p = 0.04) at the 1 week follow up. Bite force did not change significantly in the control group immediately after the intervention (&minus;2.3 &plusmn; 9.0%, p = 0.20), and decreased by 6.3% (&plusmn;3.4%, p = 0.01) at the 1-week follow-up. These results indicate that chiropractic spinal manipulation can increase maximal bite force.

Effects of cervical mobilization and exercise on pain, movement and function in subjects with temporomandibular disorders: a single group pre-post test

Objective

To investigate the effect of a rehabilitation program based on cervical mobilization and exercise on clinical signs and mandibular function in subjects with temporomandibular disorder (TMD). Material and Methods: Single-group pre-post test, with baseline comparison.

Subjects

Twelve women (22.08±2.23 years) with myofascial pain and mixed TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders.

Outcome measures

Subjects were evaluated three times: twice before (baseline phase) and once after intervention. Self-reported pain, jaw function [according to the Mandibular Functional Impairment Questionnaire (MFIQ)], pain-free maximum mouth opening (MMO), and pressure pain thresholds (PPTs) of both masseter and temporalis muscles were obtained. Baseline and post-intervention differences were investigated, and effect size was estimated through Cohen’s d coefficient.

Results

Jaw function improved 7 points on the scale after the intervention (P=0.019), and self-reported pain was significantly reduced (P=0.009). Pain-free MMO varied from 32.3±8.8 mm to 38±8.8 mm and showed significant improvement (P=0.017) with moderate effect size when compared to the baseline phase. PPT also increased with moderate effect size, and subjects had the baseline values changed from 1.23±0.2 kg/cm² to 1.4±0.2 kg/cm² in the left masseter (P=0.03), from 1.31±0.28 kg/cm² to 1.51±0.2 kg/cm² in the right masseter (P>0.05), from 1.32±0.2 kg/cm² to 1.46±0.2 kg/cm² in the left temporalis (P=0.047), and from 1.4±0.2 kg/cm² to 1.67±0.3 kg/cm² in the right temporalis (P=0.06).

Conclusions

The protocol caused significant changes in pain-free MMO, self-reported pain, and functionality of the stomatognathic system in subjects with myofascial TMD, regardless of joint involvement. Even though these differences are statistically significant, their clinical relevance is still questionable.

Inter-Rater Reliability of Neck Reflex Points in Women with Chronic Neck Pain

BACKGROUND

Neck reflex points (NRP) are tender soft tissue areas of the cervical region that display reflectory changes in response to chronic inflammations of correlated regions in the visceral cranium. Six bilateral areas, NRP C0, C1, C2, C3, C4 and C7, are detectable by palpating the lateral neck. We investigated the inter-rater reliability of NRP to assess their potential clinical relevance.

METHODS

32 consecutive patients with chronic neck pain were examined for NRP tenderness by an experienced physician and an inexperienced medical student in a blinded design. A detailed description of the palpation technique is included in this section. Absence of pain was defined as pain index (PI) = 0, slight tenderness = 1, and marked pain = 2. Findings were evaluated either by pair-wise Cohen's kappa (ĸ) or by percentage of agreement (PA).

RESULTS

Examiners identified 40% and 41% of positive NRP, respectively (PI > 0, physician: 155, student: 157) with a slight preference for the left side (1.2:1). The number of patients identified with >6 positive NRP by the examiners was similar (13 vs. 12 patients). ĸ values ranged from 0.52 to 0.95. The overall kappa was ĸ = 0.80 for the left and ĸ = 0.74 for the right side. PA varied from 78.1% to 96.9% with strongest agreement at NRP C0, NRP C2, and NRP C7. Inter-rater agreement was independent of patients' age, gender, body mass index and examiner's experience.

CONCLUSION

The high reproducibility suggests the clinical relevance of NRP in women.

Nociceptive trigeminal reflexes in non-sedated horses

Electrically induced reflexes can be used to investigate the physiology and pathophysiology of the trigeminal system in humans. Similarly, the assessment of the trigemino-cervical (TCR) and blink reflexes (BR) may provide a new diagnostic tool in horses. The aim of this study was to evoke nociceptive trigeminal reflexes and describe the electrophysiological characteristics in non-sedated horses. The infraorbital (ION) and supraorbital nerves (SON) were stimulated transcutaneously in 10 adult Warmblood horses in separate sessions using train-of-five electrical pulses. The current was increased gradually until the TCR threshold was found. The stimulus-response curve of the TCR was evaluated. At the same time as TCR, the BR response was also assessed. Surface electromyographic (EMG) responses were recorded from the orbicularis oculi, splenius and cleidomastoideus muscles. Latency, duration, amplitude of the reflexes and behavioural responses were analysed. Noxious electrical stimulation of the ION or SON evoked reflex EMG responses, with similar features regardless of the nerve that had been stimulated. Stimulations of increasing intensity elicited reflexes of increasing amplitude and decreasing latency, accompanied by stronger behavioural reactions, therefore confirming the nociceptive nature of the TCR. These findings provide a reference for the assessment of dysfunction of the equine trigeminal system.

Immediate effects of atlanto-occipital joint manipulation on active mouth opening and pressure pain sensitivity in women with mechanical neck pain

OBJECTIVE

The purpose of this study was to investigate the effects of a spinal thrust manipulation directed to the upper cervical segments (atlanto-occipital joint) on active mouth opening and pressure pain sensitivity in a trigeminal nerve innervated region (sphenoid bone) in women with mechanical neck pain.

METHODS

Thirty-seven women, ages 21 to 50 years old (mean age, 35 +/- 8 years) with mechanical neck pain were recruited for this study. Participants were randomly assigned into 1 of 2 groups as follows: an experimental group that received a spinal manipulation of the atlanto-occipital joint and a control group that received a manual contact placebo intervention. Outcomes collected were assessed pretreatment and 5 minutes posttreatment by an assessor blinded to the treatment allocation and included active mouth opening and pressure pain thresholds (PPTs) over both sides of the sphenoid bone. A 2-way repeated measures analysis of variance (ANOVA) with time (pre-post) as the within subjects variable and group (control, experimental) as the between subjects variable was used to examine the effects of the intervention. The hypothesis of interest was group-time interaction.

RESULTS

The ANOVA showed a significant effect for time (F = 23.1; P < .001) and an interaction between group and time (F = 37.7; P < .001) for active mouth opening as follows: the experimental group showed a greater improvement when compared to the control group. A large positive within-group effect size (d > 1.5) for the experimental group, whereas a negative medium within-group effect size (d = -0.5) for the control group were identified. The ANOVA showed a significant interaction between group and time (F = 14.4; P < .001) for PPT levels at the sphenoid bone as follows: the experimental group showed a greater improvement when compared to the control group. A medium positive within-group effect size (d = -0.5) for the experimental group, whereas a negative medium within-group effect size (d = -0.5) for the control group was found.

CONCLUSIONS

Our findings suggest that the application of an atlantoaxial joint thrust manipulation resulted in an increase in active mouth opening and PPT over a trigeminal nerve distribution area (sphenoid bone) in women with mechanical neck pain.

Abnormal head nociceptive withdrawal reaction to facial nociceptive stimuli in Parkinson's disease

INTRODUCTION

Trigemino-cervical-spinal reflexes (TCSRs) are complex brainstem stereotyped nociceptive responses involved in a defensive withdrawal reaction of the head from facial nociceptive stimuli.

OBJECTIVE

The present study was undertaken to collect data on possible TCSR abnormalities in idiopathic Parkinson's disease (PD) and investigate any correlation with motor signs and L-DOPA administration.

METHODS

TCSRs were registered from the semispinalis capitis and biceps brachii muscles after electrical stimulation of the supraorbital nerve in 18 patients with PD and 24 controls. The latency (L) and area (A), as well as the sensory (ST), painful (PT) and reflex (RT) thresholds were measured during the 'off' and 'on' state, and possible correlations with the UPDRS III total score, selected subscores (tremor, neck rigidity, upper limb rigidity, akinesia, rising from a chair, posture and posture instability) and duration of illness were investigated.

RESULTS

Significant changes between controls and PD patients were found in the L, A, PT and RT of TCSRs. These results were not significantly influenced by L-DOPA treatment. A significant correlation was found between neck rigidity, postural instability scores and duration of illness and the TCSR L and A values in PD patients in the 'off' state.

CONCLUSIONS

TCSRs abnormalities, combined with dopamine resistance, are consistent with a primary loss of brainstem neurons mediating a complex sensory-motor integration including neck muscle tone and postural control as well as the head withdrawal reaction to the nociceptive stimuli.

SIGNIFICANCE

TCSRs may represent a useful tool for the assessment of brainstem sensory-motor function in PD as well as other movement and degenerative disorders.

Chronic neck pain and masticatory dysfunction

Chronic nonspecific neck pain is a common problem in rheumatology and may resist conventional treatment. Pathophysiological links exist between the cervical spine and masticatory system. Occlusal disorders may cause neck pain and may respond to dental treatment. The estimated prevalence of occlusal disorders is about 45%, with half the cases being due to functional factors. Minor repeated masticatory dysfunction (MD) with craniocervical asymmetry is the most common clinical picture. The pain is usually located in the suboccipital region and refractory to conventional treatment. The time pattern may be suggestive, with nocturnal arousals or triggering by temporomandibular movements. MD should be strongly suspected in patients with at least two of the following: history of treated or untreated MD, unilateral temporomandibular joint pain and clicking, lateral deviation during mouth opening, and limitation of mouth opening (less than three fingerbreadths). Rheumatologists should consider MD among causes of neck pain, most notably in patients with abnormal craniocervical posture, signs linking the neck pain to mastication, and clinical manifestations of MD. Evidence suggesting that MD may cause neck pain has been published. However, studies are needed to determine whether treatment of MD can relieve neck pain.

Trigemino-cervical-spinal reflexes in humans

INTRODUCTION

Electrical stimulation of the supraorbital nerve (SON) induces late reflex responses in the neck muscles; these responses are hypothesised to be polysynaptic reflexes participating in a defensive withdrawal retraction of the head from facial nociceptive stimuli. Such responses may extend to the proximal muscle of the arms.

OBJECTIVE

(1) to investigate reflexes in the upper limb muscles (trigemino-spinal responses, TSR) and their relationship with trigemino-cervical responses (TCR); and (2) to identify the nociceptive component of such reflexes and their functional significance.

METHODS

Reflex responses were registered from the semispinalis capitis and biceps brachii muscles after electrical stimulation of the SON in 12 healthy subjects. The sensory (ST), painful (PT) and reflex thresholds, the latency and area of the responses, the effect of heterotopic painful stimulation (HTP), the recovery cycle as well as the effect of the expected and unexpected stimuli were measured.

RESULTS

Stable reproducible TCR and TSR responses were identified at 2.5+/-0.4 x ST, which corresponded exactly to the PT in all the subjects. The TCR and TSR areas were markedly reduced after HTP. The recovery cycle of the TSR area was faster than that of the TCR. Repeated rhythmic stimulation failed to induce progressive reflex suppression.

CONCLUSIONS

These results confirm the nociceptive nature of the TCR and indicate that the biceps brachii response (TSR) has the same nocifensive significance as the posterior neck muscle responses. TCR and TSR are mediated different polysynaptic pathways The presence of trigemino-cervical-spinal responses in our study clearly indicates that there is a reflex interaction between nociceptive trigeminal afferents and both upper and lower cervical spinal cord motoneurons.