Supraorbital Nerve Stimulation Research Articles

Changes in blink reflex after simultaneous supraorbital and mental nerve stimulations in healthy subjects.

In this study, we investigated the blink reflex (BR) after simultaneous and asynchronous stimulation of two trigeminal nerve branches. The objective was to characterize the physiology of trigeminal and facial circuits. We performed three sets of experiments: recording BR response i. after supraorbital nerve stimulation (SON), after mental nerve stimulation (MN), and after simultaneous SON and MN stimulation (SON+MN) in 18 healthy individuals; ii. after MN (at an intensity eliciting BR response) preceding SON at various interstimulus intervals (ISIs) in seven healthy subjects; iii after MN (at sensory threshold) preceding SON at various ISIs. We compared the magnitudes of early and late responses. The R1 amplitude after simultaneous SON+MN stimulation was greater than responses after single stimulation of the same branches. After simultaneous stimulations, the R2 and R2c areas under the curve (AUC) were smaller than the arithmetic sums of R2 and R2c AUC obtained after single stimulations. The second experiment provided a recovery excitability curve. In the third step, we obtained facilitation of R1 and inhibition of late responses. The SON+MN stimulation caused an increased R1 circuit excitability compared to the arithmetic sum of the single stimulations; however, magnitudes of late responses did not potentiate. Thus, we have provided evidence for R1 circuit enhancement by simultaneous stimulation in humans, whereas modulation of late responses exhibited a recovery curve similar to that shown for paired SON stimulation.

Evaluation of mechanomyogram efficacy as a tool for assessing paired-pulse inhibition of blink reflex early R1 component.

Paired-pulse stimulation provides clinically useful information regarding sensory inhibition. When supraorbital nerve stimulation is repeated within a short interval, the response to the second stimulation is reduced to varying degrees. This magnitude of change in stimulation response can be monitored by electromyogram (EMG) or by mechanomyogram (MMG) as in this report. MMG has some advantages such as being less time consuming and lacking stimulus artifact. We compared the use of MMG and EMG to validate MMG as an effective method of assessing blink reflex paired-pulse inhibition. Eight volunteers participated. Participants received electrical stimulation to the supraorbital nerve of each side. A paired-pulse paradigm was employed, varying the conditioning-test interval between 5 and 800 ms. The R1 component of the induced blink reflex was simultaneously recorded by EMG using a pair of electrodes placed on the lower eyelid and by MMG using an accelerometer placed between the electrodes. The correlation coefficient of the R1 amplitude between MMG and EMG of the grand-averaged waveforms was 0.99. The average participant r value was .91 (range .76-.99). Similar analyses were performed for the amplitude variation of the second response relative to the first response. Results correlated well, yielding r values of .97 and .86 for the grand-averaged waveform and the average for each subject. The present results demonstrate that MMG could be an alternative to EMG in assessing paired-pulse inhibition of the electrical blink reflex R1 component.

A Systematic Review of Clinical Outcomes Utilizing Combined Occipital Nerve (ONS) and Supraorbital Nerve (SON) Stimulation in the Treatment of Chronic Migraine (P7-12.008)

A Systematic Review of Clinical Outcomes Utilizing Combined Occipital Nerve (ONS) and Supraorbital Nerve (SON) Stimulation in the Treatment of Chronic Migraine (P7-12.008)

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

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.

In the spotlight: How the brainstem modulates information flow

ObjectiveThe blink reflex (BR) to supraorbital nerve (SON) stimulation is reduced by either a low-intensity prepulse stimulus to digital nerves (prepulse inhibition, PPI) or a conditioning SON stimulus (SON-1) of the same intensity as the test (SON-2) stimulus (paired-pulse paradigm). We studied how PPI affects BR excitability recovery (BRER) to paired SON stimulation. MethodsElectrical prepulses were applied to the index finger 100 ms before SON-1, which was followed by SON-2 at interstimulus intervals (ISI) of 100, 300, or 500 ms. ResultsBRs to SON-1 showed PPI proportional to prepulse intensity, but this did not affect BRER at any ISI. PPI was observed on the BR to SON-2 only when additional prepulses were applied 100 ms before SON-2, regardless of the size of BRs to SON-1. ConclusionsIn BR paired-pulse paradigms, the size of the response to SON-2 is not determined by the size of the response to SON-1. PPI does not leave any trace of inhibitory activity after it is enacted. SignificanceOur data demonstrate that BR response size to SON-2 depends on SON-1 stimulus intensity and not SON-1 response size, an observation that calls for further physiological studies and cautions against unanimous clinical applicability of BRER curves.

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.

Conscious agency vs. pre-conscious sensory filtering: Disparate suppression of trigeminal blink reflex by self-stimulation and by prepulses.

Modulation of the blink reflex (BR) to supraorbital nerve (SON) stimulation by a weak somatosensory prepulse (sPP) consists of inhibition of R2 and facilitation of R1. Similar BR changes occur with self-stimulation. Our aim was to compare neurophysiological processes underlying both effects. We assessed BR parameters in 18 healthy participants following right SON stimulation either performed by an experimenter (experiment 1A) or following self-stimulation (experiments 1B, 1C). In experiments 1A and 1C, sPPs to digit 2 preceded SON stimuli by 40, 100, 200 and 500 ms. In experiment 1B: self-stimulation was delayed by 40, 100, 200, and 500 ms. In experiment 2, BRs were elicited by an experimenter randomly during a 2-s period before participants applied self-stimulation. In experiment 1, as expected, sPPs caused facilitation of R1 and inhibition of R2, which peaked at 100 ms ISI, similarly in experiments 1A and 1C. Self-stimulation caused a decrease of R2, which was evident in a broad range of time intervals. In experiment 2, R2 was already inhibited at the onset of the 2-s period, while R1 began to rise significantly 1.4s before self-stimulation. Both effects progressively increased until self-triggering. The results concur with a time-locked gating mechanism of prepulses at brainstem level, whereas self-stimulation modulates BR in a tonic manner, reflecting a cognitive influence due to self-agency.

Using of transcutaneous supraorbital nerve stimulation in the treatment of chronic tension type headache

BACKGROUND. The clinical study was carried out as part of the scientific work Non-drug treatment methods and optimization of coping strategies for chronic tension type headache.&#x0D; AIM. To evaluate the effectiveness of the use of transcutaneous neurostimulation of the supratrochlear and supraorbital nerves in patients with chronic tension type headache.&#x0D; MATERIAL AND METHODS. The clinical study was conducted from February to August 2021. In total, 50 patients with chronic tension type headache took part in the study, which were divided into two groups: the main group (40 participants) and the control group (10 participants). In the main group, patients received transcutaneous neurostimulation of the supratrochlear and supraorbital nerves with low-frequency (60 Hz) impulses. In the control group, participants received only drug therapy. One month after the end of the course of treatment, the intensity, frequency of headache, the amount of drugs taken, and the effect of headache on work ability were assessed. Statistical processing was performed in the IBM SPSS program using tests for nonparametric data and tests of signs and Wilcoxon. The results of the data were taken as significant at p 0.05.&#x0D; RESULTS. In the main group, there was a statistically significant (p 0.05) decrease in the frequency of headache episodes by 1.8 times, the number of analgesics consumed by 2.8 times, and the intensity of headache by 50%. We also observed a decrease in the effect of headache on the ability to work of patients from 79 to 47.3%. At the same time, there were patients whose headache did not affect their ability to work. In the control group we did not notice significant dynamics in the frequency of episodes and the intensity of headache.&#x0D; CONCLUSION. In our opinion, non-invasive percutaneous neurostimulation of the supratrochlear and supraorbital nerves is an additional option for preventive treatment in patients with chronic tension type headache.

THE USE OF TRANSCUTANEOUS SUPRAORBITAL NERVE STIMULATION IN THE TREATMENT OF ASTHENIC SYNDROME AFTER COVID-19

Resume. Aim: to assess the efficacy of Transcutaneous Supraorbital Nerve Stimulation (t-SNS) with the Cefaly® Device on the parameters of asthenia and anxiety, as the main components of psychosomatic changes after suffering COVID-19. Materials and methods: an open prospective study in parallel groups was conducted. 60 patients, 30 men and 30 women, average age (61,3 ± 4,1) years, after a coronavirus infection (COVID-19) more than 6 months ago, meeting the following criteria: age from 60 to 75 years old, presence of asthenic syndrome, no contraindications to supraorbital neurostimulation was included. By the envelope method, patients were randomized into two groups. In the Cefaly® group (30 people), patients underwent 10 procedures (3 times a week) of t-SNS with the Cefaly® Device (Cefaly Technology sprl, Herstal, Belgium) in combination with restorative treatment according to temporary methodological guidelines for medical rehabilitation for a new coronavirus infection (COVID-19), in the control group (30 people), patients received only rehabilitation treatment. The results were evaluated using the Multidimensional Fatigue Inventory (MFI-20) and the Hamilton Anxiety Rating Scale (HAM-A) at baseline and after 24 days of therapy. Results: Cefaly® in addition to the standard rehabilitation program effectively reduces the severity of asthenia symptoms -in the Cefaly® group it was 33,6 %, in the control group - 14,4 %. The use of Cefaly® affects all components of the asthenic syndrome (reduced activity, reduced motivation, physical and mental asthenia). The standard rehabilitation program had an effect only on physical asthenia and reduced activity, but not on parameters of reduced motivation and mental asthenia. The reduction in total score from baseline on the HAM-A anxiety scale in the Cefaly® group was 55,16%, in control group -19,74 %. Cefaly® therapy had the greatest effect on insomnia and tension. It should be noted that the standard rehabilitation program has little effect on anxiety scores. However, after treatment, both groups maintained a high mean total asthenia score (MFI-20 - 42,5 points in the Cefaly® group, 63 points in the control group), which once again confirms that post-COVID changes (Long COVID) are long-term in nature even with availability of adequate therapy. Conclusions: The use of transcutaneous supraorbital nerve stimulation can more effectively reduce the severity of symptoms of asthenia and anxiety in people who have recovered from COVID-19.

Devices for Episodic Migraine: Past, Present, and Future.

Historically, therapies for migraine have generally involved pharmacological treatments using non-selective or selective analgesics and preventive treatments. However, for many patients these treatments are not effective, while others prefer to use non-pharmacological-based therapies. To fill this need, over the last 15years, neuromodulatory devices have entered the market for migraine treatment. Here, we will review the most recent findings for the use of these devices in the treatment of migraine. Non-invasive vagus nerve stimulation and spring-pulse transcranial magnetic stimulation are both cleared for the treatment of migraine, supported by preclinical studies that validate efficacy and mechanism of action, and complemented with clinical trial data. Other options also authorized for use include transcutaneous supraorbital nerve stimulation and remote electrical neuromodulation. Various options are available to treat migraine using authorized neuromodulatory devices. These data support their efficacy in the treatment of episodic migraine, although further studies are necessary to elucidate their mechanism of action and to provide rigor to clinical trial data.

Effect of Cervical Mobilization and Transcutaneous Supraorbital Nerve Stimulation in Migraine Without Aura

Migraine is one of the most common disabling headache disorders which is categorized into two broad types based on the number of headache days. It is called episodic or general migraine if the attacks occur less than 15 days per month, and it is categorized as chronic or transformed migraine if headache occur on 15 or more days per month. This study was conducted to find out the effect of strategy for pain using a modality and strategy using mobilization in reducing disability, frequency and pain in migraine without aura. Thirty-Two subjects were selected based on diagnostic criteria for migraine and divided into two groups. Group A received Cervical Mobilization and Myofascial Release with home exercise program and Group B received Transcutaneous Supraorbital Nerve Stimulation with home exercise program. Visual Analogue Scale, Questionnaire (HIT-6) were recorded as outcome on baseline and after 3 weeks. Results showed significant improvements in both the groups with, p&lt;0.01. Between group comparisons elicited non-significant differences with p˃ 0.05. Following the results, it can be concluded that cervical mobilization and Transcutaneous Supraorbital nerve stimulation can be added as a valuable adjunct to medical management in the treatment of migraine without aura.

Effects of sagittal split osteotomy on brainstem reflexes.

This prospective study was designed to assess whether patients with skeletal deformities show characteristic masseter inhibitory reflex (MIR) and blink reflex (BR) patterns. A secondary aim was to investigate whether these reflexes change following bilateral sagittal split osteotomy (BSSO). Fourteen consecutive patients who underwent single-jaw BSSO and 14classI subjects who constituted the control group were enrolled into the study. MIR and BR, obtained by the stimulation of supraorbital (SBR) and mental nerves (MBR), were electrophysiologically recorded. Sensory impairment in the mental nerve distribution was clinically tested. Three evaluation periods were specified as immediately before (T0), 1month (T1) and 6months (T2) after surgery. MIR early silent period duration was significantly shorter in the patients at T0 (p < 0.001). Sensory deficits developed on 23sides after BSSO, of which, 17recovered after 6months. At T1, MBR was inelicitable bilaterally in 3patients and unilaterally in 2patients. These responses were still unrecordable bilaterally in 1patient, and unilaterally in 4patients at T2. MIR were unrecordable on 18sides at T1 and recovered on 11sides at T2. There were no parallels between the clinical sensory deficits and the abnormal results of the reflexes. Shorter MIR in patients with dentofacial abnormalities may be areflection of an adapted trigeminal reflex mechanism. Although MBR and MIR abnormalities do not develop parallel to the clinical sensory deficits, their course might provide insights into the disturbed trigeminal reflex pathways.

Long-Term Experience with Occipital and Supraorbital Nerve Stimulation for the Various Headache Disorders—A Retrospective Institutional Case Series of 96 Patients

We have provided long-term data on clinically meaningful pain alleviation for drug-refractory headache disorders using occipital (ONS) and supraorbital nerve stimulation (SONS). We performed a retrospective review of 96 patients with migraine, cervicogenic headache, cluster headache, neuropathic pain of the scalp, tension-type headache, and new daily persistent headache who had undergone ONS (61.5%), SONS (11.5%), or combined ONS plus SONS (27.1%) trial implantation and definitive implantation from 2007 to 2017. Changes in pain perception over time were monitored using the visual analog scale (VAS) for pain. The cohort consisted of 60.4% women and 39.6% men, with a mean age of 46.9 ± 11.5 years and pain duration of 14 ± 14.1 years. Of the 96 patients, 65 (67.7%) were treatment responders to a trial (≥30% amelioration in the average or maximum VAS score for pain and/or number of headache days) that had lasted 22.5 ± 8.8 days. The reduction in their average VAS score for pain was to 37% ± 24.4% of baseline compared with 99.1% ± 24.1% of baseline for those without a response (P < 0.01). Of the 56 patients who had undergone implantation and had long-term follow-up data available for ≤10 years, 32 (57.1%) reported a ≥50% reduction in their average VAS score for pain. Four patients (6.5%) had requested hardware explantation. Stage II complications included 1 infection (1.6%) and 6 electrode dislocations (9.7%). The study limitations included the retrospective nature, lack of controls receiving placebo intervention, and randomization. After careful patient selection according to a positive response to a trial of ONS and/or SONS, clinically meaningful long-term benefit was achieved in 57.1% of our patients with various chronic headache conditions.

The bottom-up approach: Non-invasive peripheral neurostimulation methods to treat migraine: A scoping review from the child neurologist's perspective.

Migraine is a common and invalidating disorder worldwide. Patients of all ages experience the disorder as very impairing regarding their personal and occupational lives. The current approach in migraine therapy is multimodal including lifestyle management, psychoeducation and, if available, psychotherapeutic interventions, and pharmacotherapy. The lack of non-pharmacological and non-invasive treatment options call for new and innovative therapeutic approaches. Peripheral neurostimulation is a relatively new method in migraine management offering a painless and non-pharmacological way of targeting specific mechanisms involved in migraine. This review summarizes 15 recent randomized clinical trials to provide an overview of non-invasive peripheral neurostimulation methods currently available for the treatment of migraine. Efficacy, tolerability, and safety of the different interventions and their feasibility in the pediatric setting are evaluated. Vagal nerve stimulation (VNS), remote electrical neuromodulation (REN) and supraorbital nerve stimulation (SNS) are considered effective in treating acute migraine attacks, the latter being more pronounced in migraine without aura. Regarding migraine prevention, occipital nerve stimulation (ONS) and supraorbital nerve stimulation (SNS) demonstrated efficacy, whereas repetitive neuromuscular magnetic stimulation (rNMS) may represent a further effective option in episodic migraine. REN and rNMS were found to be well-accepted with fewer patients discontinuing treatment than those receiving direct cranial nerve stimulation. In summary, peripheral neurostimulation represents a promising option to complement the multimodal therapy concept for pediatric migraine. In particular, rNMS opens a new field for research and treatment fitting the requirements of "non-invasiveness" for children. Given the reported efficacy, safety, and feasibility, the therapy decision should be made on an individual level.

Non-Pharmacological Approaches to Headaches: Non-Invasive Neuromodulation, Nutraceuticals, and Behavioral Approaches.

Significant side effects or drug interactions can make pharmacological management of headache disorders very difficult. Non-conventional and non-pharmacological treatments are becoming increasingly used to overcome these issues. In particular, non-invasive neuromodulation, nutraceuticals, and behavioral approaches are well tolerated and indicated for specific patient categories such as adolescents and pregnant women. This paper aims to present the main approaches reported in the literature in the management of headache disorders. We therefore reviewed the available literature published between 2010 and 2020 and performed a narrative presentation for each of the three categories (non-invasive neuromodulation, nutraceuticals, and behavioral therapies). Regarding non-invasive neuromodulation, we selected transcranial magnetic stimulation, supraorbital nerve stimulation, transcranial direct current stimulation, non-invasive vagal nerve stimulation, and caloric vestibular stimulation. For nutraceuticals, we selected Feverfew, Butterbur, Riboflavin, Magnesium, and Coenzyme Q10. Finally, for behavioral approaches, we selected biofeedback, cognitive behavioral therapy, relaxation techniques, mindfulness-based therapy, and acceptance and commitment therapy. These approaches are increasingly seen as a valid treatment option in headache management, especially for patients with medication overuse or contraindications to drug treatment. However, further investigations are needed to consider the effectiveness of these approaches also with respect to the long-term effects.

Noninvasive Neuromodulation in Headache: An Update.

Migraine is a common disabling primary headache condition. Although strives have been made in treatment, there remains an unmet need for safe, effective acute, and preventative treatments. The promising concept of neuromodulation of relevant neuronal targets in a noninvasive fashion for the treatment of primary headache disorders has led to the trial of numerous devices over the years. We aimed to review the evidence on current neuromodulation treatments available for the management of primary headache disorders. Randomized controlled trial as well as open-label and real-world studies on central and peripheral cephalic and noncephalic neuromodulation modalities in primary headaches were critically reviewed. The current evidence suggests a role of single-pulse transcranial magnetic stimulation, supraorbital nerve stimulation, and remote noncephalic electrical stimulation as migraine abortive treatments, with stronger evidence in episodic rather than in chronic migraine. Single-pulse transcranial magnetic stimulation and supraorbital nerve stimulation also hold promising evidence in episodic migraine prevention and initial positive evidence in chronic migraine prevention. More evidence should clarify the therapeutic role of the external vagus nerve stimulation and transcranial direct current stimulation in migraine. However, external vagus nerve stimulation may be effective in the acute treatment of episodic but not chronic cluster headache, in the prevention of hemicrania continua and paroxysmal hemicrania but not of short-lasting neuralgiform headache attacks. The difficulty in setting up sham-controlled studies has thus far prevented the publication of robust trials. This limitation along with the cost of these therapies has meant that their use is limited in most countries. Neuromodulation is a promising nonpharmacological treatment approach for primary headaches. More studies with appropriate blinding strategies and reduction of device cost may allow more widespread approval of these treatments and in turn increase clinician's experience in neuromodulation.

Peripheral trigeminal branch stimulation for refractory facial pain: A single-center experience

ObjectiveFacial pain refractory to medical treatments may benefit from neurosurgical interventions. Only a few studies have reported on the efficacy of peripheral trigeminal stimulation and more specifically supraorbital nerve (SON) and infraorbital nerve (ION) stimulation for the treatment of facial pain. Patients and methodsIn the present study, we identified all patients at our institution who underwent SON and/or ION stimulation for treatment of facial pain due to post-herpetic, traumatic or idiopathic etiology. Relevant pre and post-operative outcomes were analyzed. ResultsWe identified 15 patients who underwent SON and/or ION stimulation. Among them, 12 (80 %) endorsed >50 % pain relief during the trial stimulation period. After a median follow-up of 5.8 months with permanent implantation, 1 patient (8.3 %) was diagnosed with lead erosion and IPG migration, two patients had lead infections (16.7 %) and one (8.3 %) had wound dehiscence. No lead migrations were identified during the long-term follow-up. The VAS score showed a statistically significant reduction from a median pre-operative score of 7 to a post-operative score of 1.8 (p = 0.011), which corresponded to a 74.3 % average pain reduction. ConclusionSON and/or ION stimulation can be an effective treatment for intractable facial pain due to post-herpetic, traumatic or idiopathic etiology; however the complication rate is relatively high. Future prospective studies with longer follow-up periods are warranted.

Jendrassik maneuver effect on spinal and brainstem reflexes.

The effect of Jendrassik Maneuver (JM) has been extensively studied on monosynaptic reflexes in numerous muscles below the level at which the maneuver was performed. Here we hypothesize that the effect of JM could be observed also on other reflexes, indicating a widespread influence of performing a motor act such as the JM. We examined polysynaptic reflexes caudal (i.e., the withdrawal reflex of the lower extremities) and rostral (i.e., the blink reflex to supraorbital nerve stimulation) to the level of JM contraction. We have assessed soleus tendon (T) reflex; withdrawal reflex in tibialis anterior and soleus muscle; blink reflex (BR), blink reflex excitability recovery curve (BR-ER) and prepulse inhibition of the blink reflex. Our results showed that (1) T-reflex amplitude increased during JM and decreased just after and 15min after JM; (2) no change in the withdrawal reflex; (3) R2 area of BR reduced significantly just after or 15min after JM; (4) Prepulse inhibition in BR reduced significantly during JM; (5) no change in BR-ER. Our results indicate that JM leads to generalized effects on neural excitability at both caudal and rostral levels. Furthermore, JM has a selective effect on excitability of reflex circuitries.

Influence of posture on blink reflex prepulse inhibition induced by somatosensory inputs from upper and lower limbs

BackgroundPrepulse inhibition (PPI) is a neurophysiological phenomenon whereby a weak stimulus modulates the reflex response to a subsequent strong stimulus. Its physiological purpose is to avoid interruption of sensory processing by subsequent disturbing stimuli at the subcortical level, thereby preventing undesired motor reactions. An important hub in the PPI circuit is the pedunculopontine nucleus, which is also involved in the control of posture and sleep/wakefulness. ObjectiveTo study the effect of posture (supine versus standing) on PPI, induced by somatosensory prepulses to either upper or lower limb. PPI was measured as the percentage inhibition of the blink reflex response to electrical supraorbital nerve (SON) stimulation. MethodsSixteen healthy volunteers underwent bilateral blink reflex recordings following SON stimulation either alone (baseline) or preceded by an electrical prepulse to the median nerve (MN) or sural nerve (SN), both in supine and standing. Stimulus intensity was 8 times sensory threshold for SON, and 2 times sensory threshold for MN and SN, respectively. Eight stimuli were applied in each condition. ResultsBaseline blink reflex parameters did not differ significantly between the two postures. Prepulse stimulation to MN and SN caused significant inhibition of R2. In supine but not in standing, R2 was significantly more inhibited by MN than by SN prepulses. In standing, SN stimulation caused significantly more inhibition of R2 than in supine, while the inhibition caused by MN prepulses did not differ significantly between postures. SignificancePPI induced by lower limb afferent input may contribute to postural control while standing.

O-13 Control over supraorbital nerve stimulation overrules the facilitation of blink reflex in defensive peripersonal space

Background The blink reflex (BR) to electrical supraorbital nerve stimulation (SON-S) is a protective reflex. Knowledge about imminent SON-S via acoustic prepulse, verbal forewarning, or self-delivery of stimulation, causes R2 suppression. The BR following median nerve stimulation increases when elicited in the defensive peripersonal space of the face (DPPS-F). Here we studied modulation of BR to SON-S by self-stimulation or visual control over hetero-stimulation in or outside the DPPS-F. Methods Twenty-three subjects participated in two sets of BR recordings following SON-S (E1, n = 10; E2, n = 17). Conditions either involved hetero-stimulation by the experimenter (E1A, E1C, E2A, E2B) or self-stimulation by subjects (E1B, E2C, E2D), with the stimulator probe in (E1B, E1C, E2B, E2D) or outside (E1A, E2A, E2C) their DPPS-F, and with subjects being aware (E1B, E2B, E2C, E2D) or unaware (E1A, E1C, E2A) about imminent stimulation. Results Compared to baseline (standard BR, E1A, E2A), R2 was facilitated with the probe held in the DPPS-F, but being unaware of stimulus triggering (E1C). Visual control of imminent stimulation (seeing the experimenter’s finger triggering the probe: E2B) and self-triggering (E1B, E2C, E2D) facilitated R1 and inhibited R2. With self-triggering, there was no difference between the probe in (E2C) or outside (E2D) the DPPS-F. Conclusion BR-R2 is facilitated in a threatening situation (probe in DPPS-F) without control (hetero-stimulation unseen by subject). R1 is facilitated and R2 inhibited when subjects have visual control or full initiative over stimulation, irrespective of seeing the probe in the DPPS-F or not.