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Background: The facial nerve, a seventh cranial nerve, is typically assessed using electrodiagnostic tests such as nerve conduction studies, electromyography, and blink reflex. When diagnosing disorders affecting the muscles and peripheral nerves, neuromuscular ultrasonography is quickly becoming an integral part of the process. This study aimed to assess if facial nerve Ultrasonography (US) could be used for better evaluation of Bell's palsy. Methods: This matched case-control study was conducted on forty patients suffering from unilateral Bell's palsy Detailed history. The facial muscle's function was assessed clinically every visit using the House-Brackman Classification of Facial function. All were subjected to evaluation by electroneurography, blink reflex test, direct facial nerve conduction studies, and Ultrasound imaging. The evaluation was done within 14 days of the onset. Results: As regards ultrasound cross-sectional area (CSA) among studied groups, there was a high statistical difference in facial nerve thickness between the diseased and healthy group regarding proximal (p<0.001), midway (p<0.001), and distal (p<0.001) sites. The facial CSA area at the proximal site could considered a good discriminator of facial nerve palsy with an area under curve (0.84) with 71% sensitivity 83.9% specificity and a cutoff point of 17 mm. There is a significant correlation between facial nerve CSA at the proximal side and latency of the ipsilateral R2 wave of blink reflex (r=0.4, p=0.02). There is a significant correlation between facial nerve ultrasound CSA at the proximal site and latency of ipsilateral R2 (r=0.4, p=0.02). Conclusion: Establishing normal values of facial nerve nerves may be greatly aided by using ultrasound in conjunction with neural electrophysiology. In the early stages of Bell's palsy, ultrasonography could be useful for evaluating the condition's structural integrity and functional assessment. [ABSTRACT FROM AUTHOR]

• This is the first report of a vestibular prepulse inhibition of the blink reflex. • A vestibular prepulse inhibits the R2 and R2c area in healthy subjects but not in patients with bilateral peripheral vestibular failure. • Vestibular PPI is a potential neurophysiological marker of vestibulo-motor integration at the brainstem level. Auditory and somatosensory prepulses are commonly used to assess prepulse inhibition (PPI). The effect of a vestibular prepulse upon blink reflex excitability has not been hitherto assessed. Twenty-two healthy subjects and two patients with bilateral peripheral vestibular failure took part in the study. Whole body yaw rotation in the dark provided a vestibular inertial prepulse. Blink reflex was electrically evoked after the end of the rotation. The amplitude of R1 and the area-under-the-curve (area) of the blink reflex R2 and R2c responses were recorded and analysed. A vestibular prepulse inhibited the R2 (p < 0.001) and R2c area (p < 0.05). Increasing the angular acceleration did not increase the R2 and R2c inhibition (p > 0.05). Voluntary suppression of the vestibulo-ocular reflex did not affect the magnitude of inhibition (p > 0.05). Patients with peripheral vestibular failure did not show any inhibition. Our data support a vestibular gating mechanism in humans. The main brainstem nucleus mediating PPI – the pedunculopontine nucleus (PPN) – is heavily vestibular responsive, which is consistent with our findings of a vestibular-mediated PPI. Our technique may be used to interrogate the fidelity of brain circuits mediating vestibular-related PPN functions. Given the PPN's importance in human postural control, our technique may also provide a neurophysiological biomarker of balance. [ABSTRACT FROM AUTHOR]

Introduction/Aims: Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is caused by RFC1 expansions. Sensory neuronopathy, polyneuropathy, and involvement of motor, autonomic, and cranial nerves have all been described with RFC1 expansions. We aimed to describe the electrodiagnostic features of patients with RFC1 expansions through multimodal electrophysiological investigations. Methods: Thirty‐five patients, with a median age of 70 years, and pathologic biallelic repeat expansions in the RFC1 gene, were tested for motor and sensory nerve conduction, flexor carpi radialis (FCR) and soleus H‐reflexes, blink reflex, electrochemical skin conductance, sympathetic skin response (SSR), and heart rate variability with deep breathing (HRV). Results: Only 16 patients (46%) exhibited the full clinical CANVAS spectrum. Distal motor amplitudes were normal in 30 patients and reduced in the legs of five patients. Distal sensory amplitudes were bilaterally reduced in a non‐length dependent manner in 30 patients. Conduction velocities were normal. Soleus H‐reflexes were abnormal in 19/20 patients of whom seven had preserved Achilles reflexes. FCR H‐reflexes were absent or decreased in amplitude in 13/14 patients. Blink reflex was abnormal in 4/19 patients: R1 latencies for two patients and R2 latencies for two others. Fourteen out of 31 patients (45%) had abnormal results in at least one autonomic nervous system test, either for ESC (12/31), SSR (5/14), or HRV (6/19). Discussion: Less than half of the patients with RFC1 expansions exhibited the full clinical CANVAS spectrum, but nearly all exhibited typical sensory neuronopathy and abnormal H‐reflexes. Involvement of small nerve fibers and brainstem neurons was less common. [ABSTRACT FROM AUTHOR]

Background: Several studies have shown the prognostic value of the blink reflex (BR) test in facial nerve palsy (FNP); however, they are limited by small sample sizes and lack of long-term follow-up. To validate the diagnostic value of the BR test in FNP, a large number of patients were followed up for 1 year. Methods: Medical records of 796 patients with FNP who received an integrative traditional Korean medicine treatment were retrospectively reviewed. The BR test was performed 14 (± 2) days after onset, and recovery was evaluated using House-Brackmann (HB) grading until complete recovery or 1 year after onset. Results: Multivariable Cox regression analysis showed that the presence of ipsilateral early response (R1; hazard ratio [HR], 2.41; p < 0.001) was a significant independent predictive factor for better recovery to HB grade II. R1 (HR, 2.21; p = 0.001) and ipsilateral late response (IR2; HR, 1.88; p = 0.006) were significant independent predictive factors for a higher recovery rate to HB grade I. Conclusion: These findings confirm that the BR test is a valuable tool for prognostic prediction in FNP.

Objective: Headache during childhood is a common condition. Although recent studies have shown that the autonomic nervous system (ANS) in adult migraine patients is affected, there are few studies evaluating this relationship in children. Adult migraine patients demonstrate no abnormal ANS function in either the sympathetic or parasympathetic nervous system but there can be sympathetic/parasympathetic hypofunction/hyperfunction. The aim of this study is to investigate autonomic dysfunction in pediatric migraine patients. Method: The study evaluated tests for autonomic functions such as the orthostatic test, 30: 15 ratio, cold-pressor test, heart-rate responses to deep and normal breathing, valsalva ratio (VR), blink reflex (BR), and sympatheticskin-response with thirty pediatric migraine patients in interictal period. Patients in control group were selected from children that had not any other disease or headhache. Results: Consistent with sympathetic hypofunction, there was more frequent orthostatic hypotension in migraine group (p=0.019) and negative correlation between average disease duration, migraine attack duration and orthostatic tests results. Consistent with parasympathetic hyperfunction, the migraine group had higher VRs (p=0.035). There was a negative correlation between analgesic use rate and normal respiratory-RR-interval variability and between attack rate and deep and normal-R-R interval (R-wave peak to R-wave peak in electrocardiograms) variability. There was a positive correlation between average disease duration and BR R2 and R2’ latency in migraine group (p=0.028 and p=0.027). Conclusion: Our study revealed that ANS functions are affected in pediatric migraine and balance between sympathetic and parasympathetic nervous system is distrupted.Our study demonstrates decreased sympathetic responsiveness during the interictal period. Our results suggest hypofunction in the parasympathetic nervous system of migraine patients as attack rate and pain density elevate.

Prepulse inhibition (PPI) of the startle reflex serves as a pre‐cognitive marker of sensorimotor gating, and its deficit may predict cognitive impairments. Startle reflex is modulated by many factors. Among them, stress has been a topic of interest, but its effects on both pre‐cognitive and cognitive variables continue to yield divergent results. This study aims to analyze the effect of acute stress on PPI of the startle reflex and cognitive function (working memory, attention, inhibition, and verbal fluency). Participants were exposed to the MAST stress induction protocol or a stress‐neutral task: stress group (n = 54) or control group (n = 54). Following stress induction, participants' startle responses were recorded, and cognition was assessed. The results revealed that participants in the stress group exhibited greater startle magnitude, lower PPI, and lower scores in working memory tests compared with the control group. Additionally, a correlation was found between working memory and PPI across all the participants, independent of stress group. These findings support the notion that after stress, both greater startle magnitude and diminished PPI could play an adaptive role by allowing for increased processing of stimuli potentially dangerous and stress‐related. Similarly, our results lend support to the hypothesis that lower PPI may be predictive of cognitive impairment. Considering the impact of stress on both pre‐cognitive (PPI) and cognitive (working memory) variables, we discuss the possibility that the effect of stress on PPI occurs through motivational priming and emphasize the relevance of considering stress in both basic and translational science. Our findings revealed that acute stress increased startle response magnitude, while reducing prepulse inhibition (PPI) and working memory scores. These results align with the notion that following stress, reduced PPI could play an adaptive role by enhancing the processing of stimuli potentially dangerous for survival. Similarly, the outcomes support the hypothesis that lower PPI may predict cognitive impairment. The impact of stress on pre‐cognitive and cognitive variables emphasizes its significance in clinical and research settings. [ABSTRACT FROM AUTHOR]

Objective: Headache during childhood is a common condition. Although recent studies have shown that the autonomic nervous system (ANS) in adult migraine patients is affected, there are few studies evaluating this relationship in children. Adult migraine patients demonstrate no abnormal ANS function in either the sympathetic or parasympathetic nervous system but there can be sympathetic/parasympathetic hypofunction/hyperfunction. The aim of this study is to investigate autonomic dysfunction in pediatric migraine patients. Method: The study evaluated tests for autonomic functions such as the orthostatic test, 30: 15 ratio, cold-pressor test, heart-rate responses to deep and normal breathing, valsalva ratio (VR), blink reflex (BR), and sympatheticskin-response with thirty pediatric migraine patients in interictal period. Patients in control group were selected from children that had not any other disease or headhache. Results: Consistent with sympathetic hypofunction, there was more frequent orthostatic hypotension in migraine group (p=0.019) and negative correlation between average disease duration, migraine attack duration and orthostatic tests results. Consistent with parasympathetic hyperfunction, the migraine group had higher VRs (p=0.035). There was a negative correlation between analgesic use rate and normal respiratory-RRinterval variability and between attack rate and deep and normal-R-R interval (R-wave peak to R-wave peak in electrocardiograms) variability. There was a positive correlation between average disease duration and BR R2 and R2’ latency in migraine group (p=0.028 and p=0.027). Conclusion: Our study revealed that ANS functions are affected in pediatric migraine and balance between sympathetic and parasympathetic nervous system is distrupted.Our study demonstrates decreased sympathetic responsiveness during the interictal period. Our results suggest hypofunction in the parasympathetic nervous system of migraine patients as attack rate and pain density elevate. [ABSTRACT FROM AUTHOR]

Blink reflex (BR) is an oligosynaptic reflex that involves the ophthalmic branch of the trigeminal nerve (TN), ipsilateral main sensory and trigeminospinal nuclei, bilateral facial nuclei, and the facial nerves (FNs). Theoretically, as BR tests the function of both TN and FNs simultaneously, it is an ideal tool for monitoring the status of TN and FNs during skull base surgeries. Nevertheless, it has been used only recently in surgeries as the use of anesthesia limits its use. For this systematic review, 2 authors input the search terms [(Blink Reflex) AND (Intraoperative Neuromonitoring OR Neuro Intraoperative Monitoring OR Intraoperative OR NIOM OR IONM) AND (skull base surgery OR Facial Nerve OR Trigeminal Nerve OR Microvascular Decompression OR Hemifacial Spasm)] in MEDLINE through its PubMed interface and other search engines. Articles that fulfilled the inclusion and exclusion criteria were obtained and scrutinized. Seven observational articles with a total of 437 participants were included. All 5 studies that described the use of BR in FN surgery noted that intraoperative BR is beneficial, safe, sensitive, specific, and predictive of outcomes, while 2 articles describing patients with trigeminal neuralgia recommended use of BR in microvascular decompression of TN. Intraoperative BR is a sensitive, specific, and safe monitoring technique that has good predictability of facial paresis and paresthesia among patients undergoing MVD for trigeminal neuralgia and primary hemifacial spasm and patients undergoing cerebellopontine angle tumor resection. [ABSTRACT FROM AUTHOR]

The primary goal of this study was to develop a parametric model that relates variation in stimulation of the trigeminal nerve to properties of the blink response. We measured blink responses in 17 healthy, adult participants to air puffs directed at the lateral canthus of the eye at five different, log‐spaced intensities (3.5–60 PSI). Lid position over time was decomposed into amplitude and velocity components. We found that blink amplitude was systematically related to log stimulus intensity, with the relationship well described by a sigmoidal function. The parameters of the model fit correspond to the slope of the function and the stimulus intensity required to produce half of a maximal blink response (the half‐response threshold). There was a reliable increase in the half‐response threshold for the contralateral as compared to the ipsilateral blink response. This increase was consistent across participants despite substantial individual differences in the half‐response threshold and slope parameters of the overall sensitivity function, suggesting that the laterality effect arises in the neural circuit subsequent to individual differences in sensitivity. Overall, we find that graded mechanical stimulation of the somatosensory trigeminal afferents elicits a graded response that is well described by a simple parametric model. We discuss the application of parametric measurements of the blink response to the detection of group differences in trigeminal sensitivity. There has been limited study of how variation in stimulus intensity influences the cutaneous blink response. We describe how variation in the intensity of an air puff stimulus relates to the amplitude of the blink response using a two‐parameter model. The parameters of the model capture individual differences in response, which may be used in future studies to identify population differences in trigeminal sensitivity. [ABSTRACT FROM AUTHOR]

• Blink reflex (BR) amplitude deterioration can be used to predict postoperative facial nerve function, especially eyelid closure function. • Patients with BR amplitude deterioration ≥51.0% have a higher risk of postoperative eyelid closure deficits. • Patients with facial corticobulbar MEP (FCoMEP)(O. oris) amplitude deterioration ≥50.3% have a higher risk of postoperative facial paralysis. The current study examined the efficacy of the facial corticobulbar motor evoked potentials (FCoMEPs) and blink reflex (BR) on predicting postoperative facial nerve function during cerebellopontine angle (CPA) tumor surgery. Data from 110 patients who underwent CPA tumor resection with intraoperative FCoMEPs and BR monitoring were retrospectively reviewed. The association between the amplitude reduction ratios of FCoMEPs and BR at the end of surgery and postoperative facial nerve function was determined. Subsequently, the optimal threshold of FCoMEPs and BR for predicting postoperative facial nerve dysfunction were determined by receiver operating characteristic curve analysis. Valid BR was record in 103 of 110 patients, whereas only 43 patients successfully recorded FCoMEP in orbicularis oculi muscle. A reduction over 50.3% in FCoMEP (O. oris) amplitude was identified as a predictor of postoperative facial nerve dysfunction (sensitivity, 77.1%; specificity, 83.6%). BR was another independent predictor of postoperative facial nerve deficit with excellent predictive performance, especially eyelid closure function. Its optimal cut-off value for predicting long-term postoperative eyelid closure dysfunction was was 51.0% (sensitivity, 94.4%; specificity, 94.4%). BR can compensate for the deficiencies of the FCoMEPs. The combination of BR and FCoMEPs can be used in CPA tumor surgery. The study first proposed an optimal cut-off value of BR amplitude deterioration (50.0%) for predicting postoperative eyelid closure deficits in patients undergoing CPA tumor surgery. [ABSTRACT FROM AUTHOR]

Background/aim: 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. Materials and methods: 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. Results: 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. Conclusion: 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. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to evaluate the functionality of the brainstem structures through the blink reflex (BR) test in patients with obstructive sleep apnoea (OSA) and to assess the effects of continuous positive airway pressure (CPAP) treatment on BR responses. Methods: Patients with moderate-severe OSA and controls underwent BR testing. Patients with OSA who were adherent to CPAP therapy repeated BR testing at 6 months follow-up. CPAP adherence was defined as CPAP use for ≥ 4 hour per night on > 5 nights per week with residual apnoea-hypopnea index less than 5 events per hour. Results: A total of 22 patients with OSA (86% male, mean age 57.8 ± 10.6 years) and 20 controls (60% male, mean age 55.3 ± 9.3 years) were included. Patients with OSA showed longer right and left R1 latency, as well as delayed right ipsilateral and contralateral R2 latencies compared to controls. Patients with OSA who were compliant with CPAP treatment (n = 16; 88% men, mean age 58.8 ± 9.7 years) showed a significant decrease in latency of the right ipsilateral and contralateral R2 responses at 6 months. Conclusion: This study showed an abnormal pattern of BR responses in patients with OSA, consistent with a significant impairment of brainstem functionality in OSA. CPAP treatment partially improved the BR responses, suggesting the importance of treating OSA. [ABSTRACT FROM AUTHOR]

Objective: To investigate the performance of structural MRI cortical and subcortical morphometric data combined with blink-reflex recovery cycle (BRrc) values using machine learning (ML) models in distinguishing between essential tremor (ET) with resting tremor (rET) and classic ET. Methods: We enrolled 47 ET, 43 rET patients and 45 healthy controls (HC). All participants underwent brain 3 T-MRI and BRrc examination at different interstimulus intervals (ISIs, 100--300 msec). MRI data (cortical thickness, volumes, surface area, roughness, mean curvature and subcortical volumes) were extracted using Freesurfer on T1-weighted images. We employed two decision tree-based ML classification algorithms (eXtreme Gradient Boosting [XGBoost] and Random Forest) combining MRI data and BRrc values to differentiate between rET and ET patients. Results: ML models based exclusively on MRI features reached acceptable performance (AUC: 0.85--0.86) in differentiating rET from ET patients and from HC. Similar performances were obtained by ML models based on BRrc data (AUC: 0.81--0.82 in rET vs. ET and AUC: 0.88--0.89 in rET vs. HC). ML models combining imaging data (cortical thickness, surface, roughness, and mean curvature) together with BRrc values showed the highest classification performance in distinguishing between rET and ET patients, reaching AUC of 0.94 ± 0.05. The improvement in classification performances when BRrc data were added to imaging features was confirmed by both ML algorithms. Conclusion: This study highlights the usefulness of adding a simple electrophysiological assessment such as BRrc to MRI cortical morphometric features for accurately distinguishing rET from ET patients, paving the way for a better classification of these ET syndromes. [ABSTRACT FROM AUTHOR]

Previous studies have identified a 'defensive graded field' in the peripersonal front space where potential threatening stimuli induce stronger blink responses, mainly modulated by top–down mechanisms, which include various factors, such as proximity to the body, stimulus valence, and social cues. However, very little is known about the mechanisms responsible for representation of the back space and the possible role of bottom–up information. By means of acoustic stimuli, we evaluated individuals' representation for front and back space in an ambiguous environment that offered some degree of uncertainty in terms of both distance (close vs. far) and front–back egocentric location of sound sources. We aimed to consider verbal responses about localization of sound sources and EMG data on blink reflex. Results suggested that stimulus distance evaluations were better explained by subjective front–back discrimination, rather than real position. Moreover, blink response data were also better explained by subjective front–back discrimination. Taken together, these findings suggest that the mechanisms that dictate blink response magnitude might also affect sound localization (possible bottom–up mechanism), probably interacting with top–down mechanisms that modulate stimuli location and distance. These findings are interpreted within the defensive peripersonal framework, suggesting a close relationship between bottom–up and top–down mechanisms on spatial representation. [ABSTRACT FROM AUTHOR]

ObjectiveTo investigate the performance of structural MRI cortical and subcortical morphometric data combined with blink-reflex recovery cycle (BRrc) values using machine learning (ML) models in distinguishing between essential tremor (ET) with resting tremor (rET) and classic ET.MethodsWe enrolled 47 ET, 43 rET patients and 45 healthy controls (HC). All participants underwent brain 3 T-MRI and BRrc examination at different interstimulus intervals (ISIs, 100–300 msec). MRI data (cortical thickness, volumes, surface area, roughness, mean curvature and subcortical volumes) were extracted using Freesurfer on T1-weighted images. We employed two decision tree-based ML classification algorithms (eXtreme Gradient Boosting [XGBoost] and Random Forest) combining MRI data and BRrc values to differentiate between rET and ET patients.ResultsML models based exclusively on MRI features reached acceptable performance (AUC: 0.85–0.86) in differentiating rET from ET patients and from HC. Similar performances were obtained by ML models based on BRrc data (AUC: 0.81–0.82 in rET vs. ET and AUC: 0.88–0.89 in rET vs. HC). ML models combining imaging data (cortical thickness, surface, roughness, and mean curvature) together with BRrc values showed the highest classification performance in distinguishing between rET and ET patients, reaching AUC of 0.94 ± 0.05. The improvement in classification performances when BRrc data were added to imaging features was confirmed by both ML algorithms.ConclusionThis study highlights the usefulness of adding a simple electrophysiological assessment such as BRrc to MRI cortical morphometric features for accurately distinguishing rET from ET patients, paving the way for a better classification of these ET syndromes.

• Multi-electrode tDCS might help steering the electric field, also at deep level. • Bilateral motor tDCS with extracephalic reference might induce significant electric fields at deep brain level. • Bilateral motor anodal tDCS with cathode over right hemisphere might selectively affect brainstem reflexes. To assess whether monopolar multi-electrode transcranial direct current stimulation (tDCS) montages might selectively affect deep brain structures through computational predictions and neurophysiological assessment. Electric field distribution in deep brain structures (i.e., thalamus and midbrain) were estimated through computational models simulating tDCS with two monopolar and two monopolar multi-electrode montages. Monopolar multi-electrode tDCS was then applied to healthy subject, and effects on pontine and medullary circuitries was evaluated studying changes in blink reflex (BR) and masseter inhibitory reflex (MIR). Computational results suggest that tDCS with monopolar multi-electrode montages might induce electric field intensities in deep brain structure comparable to those in grey matter, while neurophysiological results disclosed that BR and MIR were selectively modulated by tDCS only when cathode was placed over the right deltoid. Multi-electrode tDCS (anodes over motor cortices, cathode over right deltoid) could induce significant electric fields in the thalamus and midbrain, and selectively affect brainstem neural circuits. Multi-electrode tDCS (anodes over motor cortices, cathode over right deltoid) might be further explored to affect brainstem activity, also in the context of non-invasive deep brain stimulation. [ABSTRACT FROM AUTHOR]

Chiari malformation type 1 (CM1) includes various congenital anomalies that share ectopia of the cerebellar tonsils lower than the foramen magnum, in some cases associated with syringomyelia or hydrocephalus. CM1 can cause dysfunction of the brainstem, spinal cord, and cranial nerves. This functional alteration of the nervous system can be detected by various modalities of neurophysiological tests, such as brainstem auditory evoked potentials, somatosensory evoked potentials, motor evoked potentials, electromyography and nerve conduction studies of the cranial nerves and spinal roots, as well as brainstem reflexes. The main goal of this study is to review the findings of multimodal neurophysiological examinations in published studies of patients with CM1 and their indication in the diagnosis, treatment, and follow-up of these patients, as well as their utility in intraoperative monitoring. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a fatal form of neuromuscular disease. The aim of this study was to assess changes in the blink reflex (BR) parameters as a valid and easy-to-use tool in ALS patients. We assessed the BR test in patients with a definitive diagnosis of ALS, healthy volunteers, and patients with diseases affecting the peripheral nervous system. The BR was studied in 29 patients who met the Awaji criteria. Latencies were compared with our healthy controls (N = 50) and other diseases of the peripheral nervous system (N = 61). The ALS Functional Rating Scale—Revised (ALSFRS-R) was used to evaluate functional status. Significantly prolonged R2i and R2c latencies were found in the ALS group compared with the healthy control group (p < 0.001). The latencies of R1, R2i, R2c were all increased in the bulbar subtype compared to the limb-onset subtype (p < 0.05). According to our results, BR examination might be a promising tool to monitor the course of the disease or serve as a prognostic biomarker in patients with ALS, but it should be assessed in further studies. The abnormalities detected through BR might help perform earlier interventions in ALS patients and might be useful in other diseases affecting the peripheral nervous system. [ABSTRACT FROM AUTHOR]

AbstractBlink reflex assessment has been suggested as a potential marker for sport-related concussions (SRCs) screening. However, exertion level is known to affect the blink reflex, which may affect the clinical utility of sideline screening and post-concussion monitoring. This validation study of 44 male college-aged athletes found significant differences in several blink reflex parameters between baseline and active play. In assessing the differences between mild and moderate/higher intensity, as a function of heart rate, the number of oscillations was the only significantly different parameter between the two groups. When combining the two groups (mild and moderate/higher intensity) and comparing to baseline values of the blink reflex, there were significant differences in latency, initial velocity, time to open, and lid excursions. Using baseline data, the EyeStat provides a greater understanding of its application during baseline, and exercise monitoring.

Trigeminal neuralgia is a common condition among the adult population. Its diagnosis is primarily clinical and simple enough in typical cases featuring brief, electric-shock like paroxysmal pain triggered by harmless gestures within the trigeminal nerve territory. Laboratory and imaging tests are not available to confirm its occurrence. In addition to the paroxysmal pain forms, there are also other atypical forms featuring continuous background pain between paroxysms. In these cases, differential diagnosis with other neuropathic and non-neuropathic facial pain can be challenging. Trunk functional tests, such as the blink reflex, have been shown in some circumstances to be decisive in arriving at a correct diagnosis, as in the clinical case we present.

Background: Diagnostic tests are not routinely used for the diagnosis of primary headaches. It is possible that laboratory tests could be developed and implemented at tertiary headache centers to be an integrated part of the diagnosis and management of headache patients, and laboratory tests that can be used on-site at headache centers could help in evaluating patients with secondary headache disorders. Methods: In this narrative review, we present some of the studies that have been made so far at the Headache Diagnostic Laboratory at the Danish Headache Center that aim to investigate and phenotype primary headaches and investigate secondary headaches as well as improve management. Results: Semi-structured interviews and deep phenotyping, quantitative sensory testing, and provocation studies have been shown to be valuable in categorizing primary and secondary headache subtypes, possible pathophysiology, and defining needs for further research. In patients suspected of increased intracranial pressure, transorbital ultrasound with measurement of the optic sheath diameter may be useful in monitoring patients. The management of headache patients needs to be critically evaluated to optimize treatment continuously. Conclusion: A Headache Diagnostic Laboratory is very useful and should be an integrated part of headache care and management at tertiary headache centers. [ABSTRACT FROM AUTHOR]

The article presents the discussion on effect of greater occipital nerve block (GONB) in migraine. Topics include Prepulse inhibition (PPI) of the BR is a decrease in BR excitability due to the conditioning stimulus and representing sensory gating at the brainstem; and analyzing the electrophysiological findings in patients with the clinical response after GONB.

Background: Previous findings indicate that the blink reflex is useful to distinguish between primary (classical/idiopathic) and secondary trigeminal neuralgia. No prior studies have investigated whether the blink reflex could identify differences in electrophysiological responses between classical and idiopathic trigeminal neuralgia. With this in mind, we investigated the blink reflex in a cohort of classical and idiopathic trigeminal neuralgia patients. Methods: Participants were consecutively enrolled in the study. According to magnetic resonance imaging findings, the patients were subgrouped into either classical or idiopathic trigeminal neuralgia. Assessors were blinded to the subgroup and pain side, and the blink reflex was examined to assess R1 and R2 latencies, as well as the area under the curve. Results: The study group constituted of 55 patients with primary trigeminal neuralgia: 25 patients with classical trigeminal neuralgia and 30 patients with idiopathic trigeminal neuralgia. None of the blink reflex latencies (R1 and R2) or the area under the curve significantly differed between the two subgroups when adjusted for age and sex (p > 0.05). Conclusions: Our findings suggest that the blink reflex cannot be used to differentiate classical and idiopathic trigeminal neuralgia patients, and that both subgroups may share common pathophysiological mechanisms. Trial Registration: ClinicalTrials.gov Identifier: NCT05328661. [ABSTRACT FROM AUTHOR]

• 23 of 104 CIDP or MMN patients showed blink reflex R1 latency prolongation, yet only 5 had apparent cranial nerve impairment. • Prevalence of R1 latency prolongation in our treated cohort was lower compared to previously reported untreated CIDP cohorts. • In preliminary follow-up assessments under continuous immunoglobulin treatment, prolonged R1 latencies partially improved. This study aimed to assess cranial nerve involvement in a large adult cohort of patients with immune-mediated neuropathy undergoing immunoglobulin treatment by measuring blink reflex R1 latency prolongation in correlation with clinical findings and nerve conduction studies. 104 patients underwent blink reflex examination and ulnar nerve conduction studies and were assessed by the Inflammatory Neuropathy Cause and Treatment disability score, the revised Amyotrophic lateral sclerosis functional rating scale (ALSFRS-R) and focused clinical examination. Prolonged R1 latencies were identified in 23 of 104 patients (22.1 %). These patients had more severe functional impairments according to the ALSFRS-R, yet only five clinically presented with bulbar dysfunction, facial- or trigeminal nerve impairment. Overall R1 latency was inversely correlated to ulnar motor conduction velocity. In preliminary follow-up assessments under continuous immunoglobulin treatment, prolonged R1 latencies partially improved. Cranial nerve involvement is a common feature in immune-mediated neuropathies and is associated with a more severe disease stage. Here, R1 prolongation was detected less frequently compared to previously reported untreated cohorts. Blink reflex studies can detect subclinical cranial nerve involvement in immune-mediated neuropathies. Further studies are needed to evaluate the clinical utility of measuring R1 latency. [ABSTRACT FROM AUTHOR]

A 57‐year‐old man had trigeminal schwannoma in Meckel's cave with eyelid myokymia only. The evaluation of the trigeminal‐evoked blink reflex was useful for confirming eyelid myokymia and contributed to surgical decision‐making. In patients with persistent eyelid myokymia, neurophysiological and imaging evaluations may be useful for determining the underlying pathophysiology. [ABSTRACT FROM AUTHOR]

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 1.4 s 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. The blink reflex undergoes modulation if self‐elicited or preceded by prepulses. The influence of self‐stimulation begins already before the act of triggering, during the phase of preparation to act. Prepulses exert their maximum effect at an interstimulus interval of 100 ms, when self‐delivered or when applied by an examiner. [ABSTRACT FROM AUTHOR]

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Objective: We aimed to analyze prepulse inhibition (PPI) impairment of the blink reflex in patients with primary blepharospasm (BSP). Methods: 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) x 100%]. Results: The prepulse stimulus significantly inhibited the R2 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 R2 and R2c latencies at the three ISIs and increased the R1 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. Conclusion: In BSP patients, PPI was impaired while R1 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. [ABSTRACT FROM AUTHOR]

Blink reflex assessment has been suggested as a potential marker for sportrelated concussions (SRCs) screening. However, exertion level is known to affect the blink reflex, which may affect the clinical utility of sideline screening and postconcussion monitoring. This validation study of 44 male college-aged athletes found significant differences in several blink reflex parameters between baseline and active play. In assessing the differences between mild and moderate/higher intensity, as a function of heart rate, the number of oscillations was the only significantly different parameter between the two groups. When combining the two groups (mild and moderate/higher intensity) and comparing to baseline values of the blink reflex, there were significant differences in latency, initial velocity, time to open, and lid excursions. Using baseline data, the EyeStat provides a greater understanding of its application during baseline, and exercise monitoring. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate somatosensory function in Chinese patients with trigeminal neuralgia (TN) using a standard quantitative sensory testing (QST) battery and electrophysiological tests consisting of contact heat-evoked potentials (CHEPs) and blink reflex (BR). Twenty patients with TN and 20 sex- and age-matched healthy controls were recruited for this study. A standard QST protocol recommended by the German Research Network on Neuropathic Pain was carried out on the patients' painful and contralateral faces, the controls' right faces, and all participants' right hands. The CHEPs and BR were recorded at the Cz electrode and bilateral lower bellies of the orbicularis oculi, respectively, with thermal stimuli applied to both sides of the patient's face and the control's right face. The cold detection threshold, heat pain threshold, and mechanical pain threshold on the painful face were lower than those of healthy controls (P < 0.05), whereas the cold pain threshold and mechanical detection threshold were higher (P < 0.05) on the painful faces than those of the contralateral faces from patients or healthy controls. Mechanical pain sensitivity was higher in both test sites than in healthy controls (P < 0.05). Significantly longer N latencies (P < 0.05) and lower N–P amplitudes (P < 0.01) were detected in the patients' painful sites than in the contralateral sites and those of healthy controls. Comprehensive somatosensory abnormalities were found in painful facial sites in patients with TN, suggesting disturbances in the processing of somatosensory stimuli. Deficiencies in electrophysiological tests further revealed unilaterally impaired function of the trigeminal pathway in TN patients. [ABSTRACT FROM AUTHOR]

Background: Although the blink reflex (BR) is effective in objectively evaluating trigeminal neuropathy, few studies have demonstrated its effect on trigeminal neuralgia (TN). The authors report a patient with TN due to contralateral vestibular schwannoma (VS) functionally diagnosed by delayed R1 latency of the BR. Case Description: A 36-year-old man presented with left-sided deafness and paroxysmal facial pain in the right V1-3 area. Magnetic resonance imaging (MRI) showed a solid cystic mass compressing the right pons and left brainstem at the left cerebellopontine angle. Although preoperative BR evoked by right supraorbital nerve stimulation-induced delayed ipsilateral R1 latency and normal ipsilateral and contralateral R2 responses, the BR latency evoked by left supraorbital nerve stimulation was normal, indicating deficits in the principal nucleus of the trigeminal nerve in the right pons. The symptoms of TN disappeared after the removal of the VS. Postoperative MRI showed subtotal removal of the tumor and sufficient decompression of the pons and cerebellopontine cistern. The R1 latency returned to normal 50 days after surgery. Conclusion: The perioperative BR test was not only useful for objective evaluation of the localization of trigeminal neuropathy but also correlated with the symptoms of TN. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a fatal, multisystem neurodegenerative disease that causes the death of motoneurons (MNs) progressively and eventually leads to paralysis. In contrast, delayed onset muscle soreness (DOMS) is defined as delayed onset soreness, muscle stiffness, loss of force-generating capacity, reduced joint range of motion, and decreased proprioceptive function. Sensory deficits and impaired proprioception are common symptoms of both ALS and DOMS, as impairment at the proprioceptive sensory terminals in the muscle spindle is theorized to occur in both. The important clinical distinction is that extraocular muscles (EOM) are relatively spared in ALS, in contrast to limb skeletal muscles; however, the blink reflex goes through a gradual impairment in a later stage of disease progression. Noteworthy is, that, the stretch of EOM induces the blink reflex. The current authors suggest that the impairment of proprioceptive sensory nerve terminals in the EOM muscle spindles are partially responsible for lower blink reflex, beyond central origin, and implies the critical role of Piezo2 ion channels and Wnt-PIP2 signaling in this pathomechanism. The proposed microinjury of Piezo2 on muscle spindle proprioceptive terminals could provide an explanation for the painless dying-back noncontact injury mechanism theory of ALS.

The purpose of the study was to find differences in the parameters of the response to the blink reflex (BR) between patients with idiopathic trigeminal neuralgia (TN) and health volunteers. A prospective cohort study was conducted over 2 years. The TN-subgroup included 15 patients (mean age / SD 62.3 ± 10.7 years). Pain-free and healthy volunteers as a HV-subgroup (mean age / SD: 30.8 ± 8.1 years) were recruited from asymptomatic students of dental medicine. Diagnostic parameters were determined by measuring latency to the onset of the BR components from electric stimulation. The following branches of the trigeminal nerve were affected: maxillary branch only (26.7%), mandibular branch only (20%), combined: ophthalmic branch with maxillary branch (6.7 %), and ophthalmic branch with mandibular branch (6.7%) respectively, combined maxillary and mandibular branch (26.7%) and affected all three branches (13.4%). The latencies of the BR, left and right side together, between subgroups were significantly higher for values R1 (homolateral early response), R2 (homolateral late response), R2c latency (contralaterally expressed response) in the TN-subgroup (p < 0.05). On the basis of the presence of R1c and R3 latencies and upon considering the abnormal findings of the BR, no statistically significant differences were found between the examined subgroups (p > 0.05). Blink-reflex parameters (R1, R2 and R2c) were significantly abnormal comparing TN-patients with healthy volunteers. The R3 component of the BR was related to noxious stimuli, likewise by innocuous stimuli.

The goal of our study was to clarify the possible effect of increased intracranial pressure on electrophysiological blink reflex in idiopathic intracranial hypertension (IIH) pateints . Subjects & Methods: 40 females;20 IIH patients and 20 age matched controls , after through neurological examination , were subjected to electrically elicited blink reflex (BR) . Results: There was a significant delay in ipsilatral R2 (R2i) and contralateral R2 (R2c) latencies with 31.6 (±2.8) msec and 35.2 (±3.3) msec among cases when compared to controls with 29 (±2.6) msec and 32.2 (±2.8) msec respectively with (P-value

Abstract A 57‐year‐old man had trigeminal schwannoma in Meckel's cave with eyelid myokymia only. The evaluation of the trigeminal‐evoked blink reflex was useful for confirming eyelid myokymia and contributed to surgical decision‐making. In patients with persistent eyelid myokymia, neurophysiological and imaging evaluations may be useful for determining the underlying pathophysiology.

Neuroinflammatory mechanisms and maladaptive neuroplasticity underlie the progression of complex regional pain syndrome (CRPS), which is prototypical of central neuropathic pain conditions. While cortical maladaptive alterations are well described, little is known about the contribution of the brainstem to the pathophysiology. This study investigates the role of pain-modulatory brainstem pathways in CRPS using the nociceptive blink reflex (nBR), which not only provides a direct read-out of brainstem excitability and habituation to painful stimuli but may also be suitable for use as a diagnostic biomarker for CRPS. Thirteen patients with CRPS and thirteen healthy controls (HCs) participated in this prospective case-control study investigating the polysynaptic trigemino-cervical (R2) nBR response. The R2 area and its habituation were assessed following repeated supraorbital electrical stimulation. Between-group comparisons included evaluations of diagnostic characteristics as a potential biomarker for the disease. Patients with CRPS showed a substantial decrease in habituation on the stimulated (Cohen's d: 1.3; p = 0.012) and the non-stimulated side (Cohen's d: 1.1; p = 0.04). This is the first study to reveal altered nBR habituation as a pathophysiological mechanism and potential diagnostic biomarker in CRPS. We confirmed previous findings of altered nBR excitability, but the diagnostic accuracy was inferior. Future studies should investigate the nBR as a marker of progression to central mechanisms in CRPS and as a biomarker to predict treatment response or prognosis. [ABSTRACT FROM AUTHOR]

Differential diagnosis between Parkinson's disease (PD) and corticobasal syndrome (CBS) could be challenging at the early stage, due to the asymmetric onset of both diseases. Despite the clinical overlap, the anatomical circuits involved in these disorders are different. We evaluated R2 Blink Reflex Recovery Cycle (R2BRRC) and cortical thickness (CTh) in drug-naïve PD and CBS patients for characterizing pathophysiological mechanisms underlying these conditions. Patients with a clinically probable diagnosis of PD and possible CBS were recruited. R2BRRC was evaluated bilaterally at interstimulus intervals (ISIs) of 100–150–200–300–400–500–750 ms. Asymmetry index (AI) of R2BRRC for each ISI was computed. Patients underwent a structural brain MRI and hemisphere CTh and AI of MRI was calculated. Fourteen drug-naïve PD patients and 10 patients with early CBS diagnosis were enrolled. R2BRRC of PD patients showed an increased brainstem excitability for less affected side (LAS) stimulation at ISIs of 100 and 150 ms (p < 0.001) compared to most affected side (MAS), whereas no differences between LAS and MAS were found in CBS. AI of R2BRRC at ISI-100 ms showed significant difference, being higher in PD. CTh analysis showed significant differences between groups in hemisphere cortical volume contralateral to MAS, and, conversely, AI of MRI was significantly higher in CBS. PD patients exhibited an asymmetric pattern of brainstem excitability, compared to CBS. Conversely, CBS patients showed an asymmetric pattern of cortical atrophy. This opposite pattern of neurophysiological and structural abnormalities involving cortical and subcortical brain structures could highlight the different pathophysiological mechanisms underlying these disorders. [ABSTRACT FROM AUTHOR]

Background and objectives: Facial weakness is the most important complication of parotid gland tumor surgery. The aims of this study are as follows: (1) assessment of the prevalence of postparotidectomy facial nerve dysfunction; (2) clinical and electrophysiological assessment of the facial nerve function before parotidectomy and at 1 and 6 months postoperatively; (3) assessment of the association of postoperative facial palsy with selected risk factors; and (4) assessment of the correlation between the results of clinical and neurophysiological assessments of facial nerve function. Materials and Methods: This study comprised 50 patients (aged 24–75 years) who underwent parotidectomy at the Department of Otolaryngology and Laryngological Oncology in Zabrze, Poland between 2015 and 2017. The evaluation included neurological, clinical and electrophysiological assessments of the facial nerve prior to surgery and at 1 and 6 months postoperatively. Results: No facial palsy was found preoperatively or 6 months postoperatively. Facial nerve dysfunction was found in 74% of patients 1 month postoperatively. In most cases (54%), paresis was mild or moderate (House–Brackmann grades II and III). The results of electrophysiological tests before parotidectomy were either normal or showed some mild abnormalities. We found a statistically significant correlation between the clinical assessment of the facial nerve function (based on the House–Brackmann scale) one month postoperatively and the latency of the CMAP response from the orbicularis oculi and orbicularis oris muscles. In all three studies, a statistically significant correlation was found between the amplitude of the compound muscle action potential (CMAP) of the orbicularis oris muscle and the degree of facial nerve weakness. Conclusions: The factors that may influence the risk of postoperative facial nerve paralysis (prolonged surgical time and the size and location of the tumor other than in the superficial lobe only) may indirectly suggest that surgery-related difficulties and/or surgeon experience could be crucial to surgery safety. [ABSTRACT FROM AUTHOR]