Stressing out! Effects of acute stress on prepulse inhibition and working memory

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.

A measure of the blink reflex to parametric variation of mechanical stimulation of the trigeminal nerve

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.

Combined cortical thickness and blink reflex recovery cycle to differentiate essential tremor with and without resting tremor

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.

The Role of Neurophysiology in Managing Patients with Chiari Malformations

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.

Blink Reflex Examination in Patients with Amyotrophic Lateral Sclerosis Compared to Diseases Affecting the Peripheral Nervous System and Healthy Controls

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.

Evaluating Headache and Facial Pain in a Headache Diagnostic Laboratory: Experiences from the Danish Headache Center

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.

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 1.4 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.

Eyelid myokymia caused by a trigeminal schwannoma as determined by the trigeminal-evoked blink reflex

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.

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

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) × 100%].

Results

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.

Conclusion

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.

Impaired Pain Processing at a Brainstem Level Is Involved in Maladaptive Neuroplasticity in Patients with Chronic Complex Regional Pain Syndrome

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.

Prospective Assessment of Risk Factors Influencing Facial Nerve Paresis in Patients after Surgery for Parotid Gland Tumors

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.

EVAULATION OF BLINK REFLEX BETWEEN PATIENTS WITH IDIOPATHIC TRIGEMINAL NEURALGIA AND HEALTHY VOLUNTEERS

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 peak latency prolongation of the blink reflex in a patient with trigeminal neuralgia of Meckel's cave mass]

The blink reflex test of the trigeminal nerve can provide valuable information about lesions site. However it may not find small compressive lesions. We observed peak latency prolongation of the blink reflex test in a patient with trigeminal neuralgia caused by a small Meckel's cave mass, in whom the onset latency was normal. Conclusion - We suggest peak latency of the blink reflex might be a valuable aid for discerning small mass in patients with trigeminal neuralgia. This is the first case report of compressive trigeminal neuralgia showing peak latency prolongation of the blink reflex test.

COVID-19 can cause blink reflex abnormalities

BACKGROUND AND PURPOSE

Neurological symptoms and complications associated with coronavirus 2019 (COVID-19) are well known. It was aimed to evaluate the brainstem and trigeminal/facial nerves and the pathways between these structures in COVID-19 using the blink reflex test.

METHODS

Thirty patients with post COVID-19 (16 males, 14 females) and 30 healthy individuals (17 males, 13 females) were included in this prospective study. Individuals who previously had a positive nose swap polymerase chain reaction test for severe acute respiratory syndrome coronavirus 2 and whose previously clinical features were compatible with COVID-19 were included in the post COVID-19 patient group. Neurological examination of the participants should be normal. Blink reflex test was performed on all participants. R1, ipsilateral R2 (IR2), and contralateral R2 (CR2) waves obtained from the test were analyzed.

RESULTS

The mean ages of healthy individuals and post COVID-19 patients were 34.0±6.4 and 38.4±10.6 years, respectively. Both age and gender were matched between the groups. R1, IR2, and CR2 latencies/amplitudes were not different between the two groups. The side-to-side R1 latency difference was 0.5±0.3 and 1.0±0.8 ms in healthy individuals and post COVID-19 patients, respectively (p=0.011). One healthy individual and 12 patients with post COVID-19 had at least one abnormal blink reflex parameter (p=0.001).

CONCLUSION

This study showed that COVID-19 may cause subclinical abnormalities in the blink reflex, which includes the trigeminal nerve, the seventh nerve, the brainstem, and pathways between these structures.

Blink reflex: A practical test to evaluate the trigeminal nerve injury following percutaneous balloon compression for the treatment of trigeminal neuralgia

OBJECTIVE

To evaluate the blink reflex (BR) in estimating the potential injury of trigeminal nerve following percutaneous balloon compression (PBC) surgery, and to determine the association between BR alterations and early surgical outcomes.

METHODS

In this single-center, prospective before-and-after study, a total of 74 patients who had primary trigeminal neuralgia and scheduled for PBC between October 2020 and June 2021 were prospectively included. BR testing and facial sensory assessment were performed pre- and post-PBC. The latency and the area under the curve (AUC) of pre- and postoperative R1 (R1_pre /R1_post ) and R2 (R2_pre /R2_post ) were measured.

RESULTS

The BR components were noticeably delayed or diminished following PBC. R1_post was elicited in only 26 patients, and absent in 48 patients. The residual R1_post had markedly reduced AUC (median difference [Hodges-Lehmann]: -59.5, 95% confidence interval [CI]: -217.5 to -6.9, p = 0.023). Compared with R2_pre , the latency of R2_post was considerably delayed (mean difference: 4.3, 95% CI: 2.9 to 5.7, p < 0.001) and the AUC was greatly suppressed (median difference [Hodges-Lehmann]: -388.4, 95% CI: -548.4 to -259.5, p < 0.001). After PBC, 58 patients had immediate total pain relief, and 16 had partial relief. The absence of R1_post was found in 46 of 58 (79.3%) patients with complete remission, whereas in only 2 of 16 (12.5%) patients with partial relief. Association analysis showed that the absence of R1_post was strongly associated with total pain relief (46/58 [79.3%] vs. 2/16 [12.5%], odds ratio [OR]: 26.8, 95% CI: 5.4 to 134.5, Cramér's V: 0.6, p < 0.001). The latency of R2_post in patients with total relief was significantly delayed (mean difference: 2.5, 95% CI: 0.3 to 4.6, p = 0.028). Patients experienced graded facial numbness after PBC, of whom 31 reported mild numbness (Grades I-II) and 43 reported more severe numbness (Grades III-IV). The absence of R1_post was significantly associated with facial numbness severity, 33/43 (76.7%) in Grades III-IV vs. 15/31 (48.4%) in Grades I-II (OR: 0.284, 95% CI: 0.105 to 0.771, Cramér's V: 0.3, p = 0.012). In patients with more severe numbness, the latency of R2_post was significantly delayed (mean difference: 2.7, 95% CI: 0.1 to 5.3, p = 0.043), and the reduction of AUC was much greater (median difference [Hodges-Lehmann]: 17.2, 95% CI: 0.5 to 35.4, p = 0.041).

CONCLUSION

Both R1 and R2 were significantly diminished after PBC and these alterations were associated with early surgical outcomes, suggesting that the BR is useful in evaluating trigeminal injury following PBC and could provide objective information about early prognosis.

Conditioned Pain Modulation: Comparison of the Effects on Nociceptive and Non-nociceptive Blink Reflex

Although conditioned pain modulation (CPM) is considered to represent descending pain inhibitory mechanisms triggered by noxious stimuli applied to a remote area, there have been no previous studies comparing CPM between pain and tactile systems. In this study, we compared CPM between the two systems objectively using blink reflexes. Intra-epidermal electrical stimulation (IES) and transcutaneous electrical stimulation (TS) were applied to the right skin area over the supraorbital foramen to evoke a nociceptive or a non-nociceptive blink reflex, respectively, in 15 healthy males. In the test session, IES or TS were applied six times and subjects reported the intensity of each stimulus on a numerical rating scale (NRS). Blink reflexes were measured using electromyography (R2). The first and second sessions were control sessions, while in the third session, the left hand was immersed in cold water at 10 °C as a conditioning stimulus. The magnitude of the R2 blink and NRS scores were compared among the sessions by 2-way ANOVA. Both the NRS score and nociceptive R2 were significantly decreased in the third session for IES, with a significant correlation between the two variables; whereas, TS-induced non-nociceptive R2 did not change among the sessions. Although the conditioning stimulus decreased the NRS score for TS, the CPM effect was significantly smaller than that for IES (p = 0.002). The present findings suggest the presence of a pain-specific CPM effect to a heterotopic noxious stimulus.

Effects of Transcranial Ultrasound Stimulation on Trigeminal Blink Reflex Excitability

Recent evidence indicates that transcranial ultrasound stimulation (TUS) modulates sensorimotor cortex excitability. However, no study has assessed possible TUS effects on the excitability of deeper brain areas, such as the brainstem. In this study, we investigated whether TUS delivered on the substantia nigra, superior colliculus, and nucleus raphe magnus modulates the excitability of trigeminal blink reflex, a reliable neurophysiological technique to assess brainstem functions in humans. The recovery cycle of the trigeminal blink reflex (interstimulus intervals of 250 and 500 ms) was tested before (T0), and 3 (T1) and 30 min (T2) after TUS. The effects of substantia nigra-TUS, superior colliculus-TUS, nucleus raphe magnus-TUS and sham-TUS were assessed in separate and randomized sessions. In the superior colliculus-TUS session, the conditioned R2 area increased at T1 compared with T0, while T2 and T0 values did not differ. Results were independent of the interstimulus intervals tested and were not related to trigeminal blink reflex baseline (T0) excitability. Conversely, the conditioned R2 area was comparable at T0, T1, and T2 in the nucleus raphe magnus-TUS and substantia nigra-TUS sessions. Our findings demonstrate that the excitability of brainstem circuits, as evaluated by testing the recovery cycle of the trigeminal blink reflex, can be increased by TUS. This result may reflect the modulation of inhibitory interneurons within the superior colliculus.

Brainstem Reflexes in Idiopathic Cervical Dystonia: Does Medullary Dysfunction Play a Role?

Background

Neurophysiological markers in dystonia have so far not been sistematically applied in clinical practice due to limited reproducibility of results and low correlations with clinical findings. Exceptions might be represented by the blink reflex (BR), including its recovery cycle (BRRC) and the trigemino‐cervical reflex (TCR) which, compared to other neurophysiological methods, have shown more consistent alterations in cervical dystonia (CD). However, a comparison between the two techniques, and their possible correlation with disease symptoms, have not been thoroughly investigated.

Objectives

To assess the role of BR, BRCC and TCR in the pathophysiology of idiopathic cervical dystonia.

Methods

Fourteen patients and 14 age‐matched healthy controls (HC) were recruited. Neurophysiological outcome measures included latency of R1 and R2 components of the BR, R2 amplitude, BRRC, latency and amplitude of P19/N31 complex of TCR. Clinical and demographic features of patients were also collected, including age at disease onset, disease duration, presence of tremor, sensory trick and pain. The Toronto Western Spasmodic Torticollis Rating Scale was used to characterize dystonia.

Results

Compared to HC, CD patients showed increased latency of the BR R2 and decreased suppression of the BRRC. They also showed increased latency of the P19 and decreased amplitude of P19/N31 complex of TCR. The latency of P19 component of TCR was positively correlated with disease duration.

Conclusions

We propose that the increased latency of R2 and P19 observed here might be reflective of brainstem dysfunction, mediated either by local interneuronal excitability changes or by subtle structural damage.

[Hemifacial spasm]

Hemifacial spasm (HFS), or facial hemispasm, is a paroxysmal hyperkinetic disorder involving muscles innervated by the facial nerve, mainly on the one hand. The development of HFS is based on neurovascular conflict. However, it is impossible to explain the clinical manifestations of HFS only by nerve compression. Both peripheral and central mechanisms are involved in the generation of HFS, with the formation of ephaptic transmission, antidromic excitation, primary or secondary hyper-excitability of the nuclear and supranuclear level of innervation. Two treatment methods are pathogenetically justified: microvascular decompression (MVD) and botulinum toxin (BTX) injections. The effectiveness of MVD is 95.37% with full or partial recovery. The recurrence rate does not exceed 2.4%. Facial nerve paralysis (2.7-22.5%) and hearing loss (1.9-20%) are the most common complications of treatment with the use of the MVD for HFS with partial or complete cure in most cases. Botulinum toxin injection chemo-denervation is a first-line treatment of primary and secondary HFS. HFS is an officially registered indication for the drug dysport (abobotulotoxin) (ABO) in the Russian Federation. Total doses of ABO ranged from 25 to 150 units for one side depending on the severity of the clinical manifestations. Studies demonstrate the statistically significant benefits of HFC treatment with ABO. ABO is generally well-tolerated. Adverse events (up to 3.6%) are transient and include ptosis, lacrimation, blurred vision, double vision, dry eyes and weak facial muscles.

A Unique Shape of Brainstem Lesion that Caused Orthostatic Hypotension in Anti-NMDAR Encephalitis

After experiencing upper respiratory-tract symptoms, a 41-year-old woman developed encephalitis with consciousness disturbance and respiratory failure. She had external ophthalmoplegia and facial diplegia. Magnetic resonance imaging revealed a brainstem lesion with spared longitudinal pontine bundles. Abnormal findings of the brainstem auditory-evoked potentials and blink reflex supported brainstem damage. The patient was positive for anti-N-methyl-D-aspartate receptor (NMDAR) antibodies. Repeated immunological treatments improved her symptoms, but severe orthostatic hypotension emerged. A head-up tilt test revealed no arginine vasopressin response to hypotension. The atypical symptoms of this case highlighted that the brainstem is one of the pivotal regions in anti-NMDAR encephalitis.

The Three Nociceptive Responses of the Orbicularis Oculi Reflex in Alzheimer's Disease: State of the Evidence and Meta-analysis

There is an emerging belief that electrically elicited blink reflexes (BR) may distinguish Alzheimer's disease (AD) from other disorders characterized by memory dysfunction. To qualitatively and quantitatively distinguish the effects that electrical stimulation has over the blink reflex (eBR) recorded from patients with AD and healthy controls (HCs), we did a systematic review of the literature, and conducted a meta-analysis. Following our selected criteria, 94 AD patients and 97 HCs were identified from articles published in English between 1950 and 2017. Although the 3 responses (R1, R2 and R3) of the eBR were studied in a number of patients, only the R2 response was quantified in all studies. Thresholds and stimulation intensities parameters were found to be used in a miscellaneous form, and the majority of times, such parameters deviated from validated guidelines. The stimulation frequencies used to elicit the BR responses ranged between 0.14 and 0.2 Hz. These frequencies favored HCs compared with AD patients (odds ratio = 1.08; 95% CI = 0.30-1.85), I² = 0% [P = .99]; Q = 271.89 [df = 7, P < .000]). Egger's regression test suggested publication bias (intercept = 32.38; 95% CI = -8.98 to -3.2; P = .001). Our results unveiled key shortcomings in the data reported; such shortcomings need to be corrected in future AD research looking for obtaining more reliable and reproducible eBR studies; otherwise, interventions may be misleading.

Electroneurography value as an indicator of high risk for the development of moderate-to-severe synkinesis after Bell's palsy and Ramsay Hunt syndrome

Background: The degree of distress caused by the sequelae of peripheral facial nerve palsy usually depends on the severity of synkinesis. Objective: To clarify whether electroneurography (ENoG) can predict the severity of synkinesis after peripheral facial nerve palsy. Materials and methods: One-hundred and fourteen patients treated for facial nerve palsy at our hospital from April 2014-September 2016 were retrospectively reviewed. ENoG was performed 10-16 days after symptom onset. Patients were classified into Groups A (ENoG value 10%-20%, n = 9) and B (ENoG value <10%, n = 21). Eight months after symptom onset, electrophysiological and symptomatic outcomes were evaluated as the aberrant regeneration ratio of the blink reflex and the total synkinesis score of the Sunnybrook facial grading system, respectively. The outcomes of the groups were compared. Results: Group B had a significantly higher median aberrant regeneration ratio (0% versus 87%, p=.015), median total synkinesis score (1 versus 3, p < .001), and incidence of moderate-to-severe synkinesis (0% versus 57.2%, p=.003) than did Group A. Conclusions and significance: Patients with an ENoG value of <10% have higher risks of aberrant regeneration and moderate-to-severe synkinesis than those with an ENoG value of 10%-20%. Patients with ENoG values of <10% may require rehabilitation to prevent synkinesis.

Disease progression in blepharospasm: a 5-year longitudinal study

BACKGROUND AND PURPOSE

The clinical manifestation of dystonic spasms in blepharospasm (BSP) patients may be heterogeneous. Whether the varying phenomenology of eyelid spasms becomes manifest sequentially during the course of the disease or aggregates in separate clusters according to different disease courses is still unclear. For this purpose, the clinical features in BSP patients were evaluated longitudinally over a 5-year period and also the blink reflex recovery cycle was tested in a subgroup of BSP patients.

METHODS

Sixty BSP patients were videotaped at time 0 and after approximately 5 years of follow-up. Two experts in movement disorders, who were blinded to the video order, reviewed the videotapes and scored the severity of BSP using the Blepharospasm Severity Rating Scale. Changes in the R2 recovery index were also evaluated in 18 patients twice, i.e. upon enrolment and at the follow-up.

RESULTS

The severity of BSP worsened significantly over the 5-year follow-up period owing to the appearance or the increased duration and frequency of prolonged spasms. It was also found that the blink reflex recovery cycle worsened at follow-up in comparison with the baseline.

CONCLUSIONS

This study shows that the disease progression of BSP is characterized by the appearance or worsening of prolonged spasms. Prolonged spasms are accompanied by changes in the excitability of brainstem interneurons. Aging-related effects may exacerbate the pathophysiological mechanisms underlying spasms.

Electrophysiological Characteristics of the Migraine Brain: Current Knowledge and Perspectives

BACKGROUND

Despite pain being its most prominent feature, migraine is primarily a disorder of sensory processing. Electrophysiology-based research in the field has consistently developed over the last fifty years.

OBJECTIVE

To summarize the current knowledge on the electrophysiological characteristics of the migraine brain, and discuss perspectives.

METHODS

We critically reviewed the literature on the topic to present and discuss articles selected on the basis of their significance and/or novelty.

RESULTS

Physiologic fluctuations within time, between-subject differences, and methodological issues account as major limitations of electrophysiological research in migraine. Nonetheless, several abnormalities revealed through different approaches have been described in the literature. Altogether, these results are compatible with an abnormal state of sensory processing.

PERSPECTIVES

The greatest contribution of electrophysiological testing in the future will most probably be the characterization of sub-groups of migraine patients sharing specific electrophysiological traits. This should serve as strategy towards personalized migraine treatment. Incorporation of novel methods of analysis would be worthwhile.

Blink R1 latency utility in diagnosis and treatment assessment of polyradiculoneuropathy-organomegaly-endocrinopathy-monoclonal protein-skin changes and chronic inflammatory demyelinating polyradiculoneuropathy

INTRODUCTION

In polyradiculoneuropathy-organomegaly-endocrinopathy-monoclonal protein-skin changes (POEMS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), limb nerve conduction studies (NCSs) are limited in identifying demyelination and in detecting treatment effects in severely affected patients. Blink R1 latency may improve these assessments.

METHODS

POEMS and CIDP patients who had undergone NCS and blink reflex were identified. Correlations among R1 latency, limb NCS, and neuropathy impairment scores (NIS) were compared.

RESULTS

Among 182 patients (124 POEMS, 58 CIDP) who were identified, R1 prolongation (>13 ms) occurred in 64.3% (65.3% POEMS, 62.1% CIDP). R1 prolongation correlated with more severely affected NCS in both POEMS (ulnar CMAP 2.6 mV vs. 4.5 mV, P = 0.001) and CIDP (2.0 mV vs. 6.1 mV, P < 0.001). In severely affected patients (ulnar CMAP ≤0.5 mV [10%:18/182]), R1 (>13 ms) helped establish demyelination. In 31 patients (16 POEMS, 15 CIDP), the R1 latency changes were concordant with NIS changes in 94% of patients with POEMS and 60% of patients with CIDP.

DISCUSSION

Blink R1 latencies are valuable in defining demyelination and detecting improvement in severely affected POEMS and CIDP patients. Muscle Nerve 57: E8-E13, 2018.

Effect of combined opioid receptor and α2-adrenoceptor blockade on anxiety and electrically evoked startle responses

The R3 component of the electrically evoked blink reflex may form part of a startle reaction. Acoustic startle responses are augmented by yohimbine, an α₂-adrenoceptor antagonist that blocks α₂-autoreceptors, and are potentiated by opioid receptor blockade. To investigate these influences on electrically evoked startle responses, 16 mg yohimbine, with (16 participants) or without 50 mg naltrexone (23 participants), was administered in separate double-blind placebo-controlled cross-over experiments. In each experiment, R3 (a probable component of the startle response) was examined before and after high-frequency electrical stimulation of the forearm, a procedure that initiates inhibitory pain controls. Anxiety and somatic symptoms were greater after yohimbine than placebo, and were potentiated by naltrexone. Pain ratings for the electrically evoked startle stimuli decreased after high-frequency electrical stimulation in the placebo session but remained stable after drug administration. Yohimbine with naltrexone, but not yohimbine alone, also blocked an inhibitory effect of high-frequency electrical stimulation on electrically evoked sharp sensations and R3. Together, the findings suggest that adding naltrexone to yohimbine potentiated anxiety and blocked inhibitory influences of high-frequency electrical stimulation on electrically evoked sensations and startle responses. Thus, opioid peptides could reduce activity in nociceptive and startle-reflex pathways, or inhibit crosstalk between these pathways. Failure of this inhibitory opioid influence might be important in chronically painful conditions that are aggravated by startle stimuli.

Approaching threatening stimuli cause an expansion of defensive peripersonal space

When sudden environmental stimuli signaling threat occur in the portion of space surrounding the body (defensive peripersonal space), defensive responses are enhanced. Recently Bisio et al. (Bisio A, Garbarini F, Biggio M, Fossataro C, Ruggeri P, Bove M. J Neurosci 37: 2415-2424, 2017) showed that a marker of defensive peripersonal space, the defensive hand-blink reflex, is modulated by the motion of the eliciting threatening stimulus. These results can be parsimoniously explained by the continuous monitoring of environmental threats, resulting in an expansion of defensive peripersonal space when threatening stimuli approach.

Serial neurophysiological and neurophysiological examinations for delayed facial nerve palsy in a patient with Fisher syndrome

The patient was a 47-year-old man who presented with diplopia and gait instability with a gradual onset over the course of three days. Neurological examinations showed ophthalmoplegia, diminished tendon reflexes, and truncal ataxia. Tests for anti-GQ1b antibodies and several other antibodies to ganglioside complex were positive. We made a diagnosis of Fisher syndrome. After administration of intravenous immunoglobulin, the patient's symptoms gradually improved. However, bilateral facial palsy appeared during the recovery phase. Brain MRI showed intensive contrast enhancement of bilateral facial nerves. During the onset phase of facial palsy, the amplitude of the compound muscle action potential (CMAP) in the facial nerves was preserved. During the peak phase, the facial CMAP amplitude was within the lower limit of normal values, or mildly decreased. During the recovery phase, the CMAP amplitude was normalized, and the R1 and R2 responses of the blink reflex were prolonged. The delayed facial nerve palsy improved spontaneously, and the enhancement on brain MRI disappeared. Serial neurophysiological and neuroradiological examinations suggested that the main lesions existed in the proximal part of the facial nerves and the mild lesions existed in the facial nerve terminals, probably due to reversible conduction failure.

The Effects of Attention on the Trigeminal Blink Reflex

During top-down processing, higher cognitive processes modulate lower sensory processing. The present experiment tested the effects of directed attention on trigeminal reflex blinks in humans (n = 8). In separate sessions, participants either attended to blink-eliciting stimuli or were given no attentional instructions during stimulation of the supraorbital branch of the trigeminal nerve. Attention to blink-eliciting stimuli significantly increased reflex blink amplitude and duration and shortened blink latency compared with the no attention condition. These results suggested that higher processes such as attention can modify the trigeminal blink reflex circuit.

Assessment of Blink Reflex in Genetic Generalized Epilepsy Patients With Eyelid Myoclonia

Eyelid myoclonia (EM) with or without absences are a rare type of generalized seizures associated with a variety of epilepsy syndromes with an unknown pathophysiology. The aim of this study was to investigate the possible contribution of the brainstem structures in this underrecognized special type of seizures. Sixteen consecutive patients with EM, diagnosed with genetic generalized epilepsy (GGE) according to International League Against Epilepsy 2010 criteria were included. Brainstem excitabilities were examined by blink reflex (BR) studies. The results of BR studies in GGE patients with EM were statistically compared with 2 control groups; namely age- and gender-matched healthy volunteers and juvenile myoclonic epilepsy (JME) patients without any absences and using similar antiepileptic drugs. There were no statistical differences between the thresholds of the BR studies and the BR recovery curves in terms of amplitudes and areas of healthy subjects, JME patients and GGE patients with EM. Our findings do not support a profound interictal hyperexcitability in the BR-related brainstem structures of the GGE patients with EM. It can be considered that EM may be associated with excitability changes of the occipital cortex and other cortical areas.

Blepharospasm: Update on Epidemiology, Clinical Aspects, and Pathophysiology

Blepharospasm (BSP) is a rather distressing form of focal dystonia. Although many aspects of its pathophysiological mechanisms are already known, we lack fundamental evidence on etiology, prevention, and treatment. To advance in our knowledge, we need to review what is already known in various aspects of the disorder and use these bases to find future lines of interest. Some of the signs observed in BSP are cause, while others are consequence of the disorder. Non-motor symptoms and signs may be a cue for understanding better the disease. Various cerebral sites have been shown to be functionally abnormal in BSP, including the basal ganglia, the cortex, and the cerebellum. However, we still do not know if the dysfunction or structural change affecting these brain regions is cause or consequence of BSP. Further advances in neurophysiology and neuroimaging may eventually clarify the pathophysiological mechanisms implicated. In this manuscript, we aim to update what is known regarding epidemiology, clinical aspects, and pathophysiology of the disorder and speculate on the directions of research worth pursuing in the near future.

Reversible cerebral and brain stem dysfunction in n: Hexane neuropathy

A 18-year-old male, screen printer by profession developed sensory motor polyneuropathy, change in his behavior, bilateral 6^th and 7^th cranial nerve palsies, down beat nystagmus and cerebellar dysarthria. He had bilaterally prolonged P100 latency; left: 137 ms; right: 144 ms. P 37 was not recordable on either side while N 20 was normal. The inter latency difference between Ipsilateral R2 and Contralateral R2 was 6.15 ms, on the left side and normal on the right side. In the follow-up, there was normalization of the blink reflex study, improvement in P100 latency [left: 114 ms; right: 120 ms.] but worsening of peripheral nerve conductions. The sequential clinical recovery was of the behavioral dysfunction, down beat nystagmus, 6^th nerve, 7^th nerve involvement and ataxia, in that order. Sural nerve biopsy showed loss of large diameter myelinated fibers.

Clinical and electrophysiological aspects of tics in children

BACKGROUND

Tics are diverse in nature inappropriate movements or vocalizations. They significantly degrade patients' quality of life, lead to social difficulties, and disturbance of learning especially during exacerbations. The prevalence of tics among children ranges from 4% to 24%, thus emphasizing the relevance of the problem.

OBJECTIVE

To study clinical and electrophysiological features of tics in children with development of new treatment methods.

METHODS

We conducted a comprehensive clinical and electrophysiological examination of 50 patients with tics, aged 5 to 15 years. The control group consisted of 20 healthy children. The research included a thorough study of the history, neurological examination, manual testing of skeletal muscles, psychological testing. Electrophysiological examination included a review of the functional state of corticospinal tract (CST) by the method of magnetic stimulation (MS), study of polysynaptic reflex excitability (PRE) according to a late component of the blink reflex (BR). Statistical analysis included parametric and nonparametric methods of data processing.

RESULTS

All children of the study group showed signs of minimal brain dysfunction (MBD), they had complicated antenatal and postnatal history (trauma, disease, occurring with intoxication). There was a trend towards the increase of MBD signs with worsening of tics. Manual diagnosis in patients identified functional blockade at different levels of the vertebral column, sacroiliac joints, we identified latent myofascial trigger points (MFTP) mainly in the cervical-collar zone, in the area of the paravertebral muscles, periosteal triggers in the area of the sacroiliac joints.The research allowed determining decrease in propagation velocity of excitation (PVE) throughout CST in patients with tics. Correlation analysis revealed a negative correlation between the severity of tics and PVE (r = -0.38; p < 0.001).When studying polysynaptic reflex excitability (PRE) a significant predominance of hyper-excited types of blink reflex (BR) (90% of cases) was revealed. However, in 10% of patients there was a moderate decrease in propagation velocity of excitation (PVE), which allowed us to identify two subgroups of patients with tics: I - low and moderate type of reflex responses; and II - high type of reflex responses. Collation of data of MS and BR revealed a significant decrease of PVE in patients of the subgroup I, which probably reflects a deeper disturbance of the neuro-motor apparatus. The presence of numerous myofascial trigger points (MFTP) in patients of the subgroup I with moderately low polysynaptic reflex excitability (p < 0.05) was characteristic.

CONCLUSIONS

The data show extraordinary sensitivity of neuromuscular system of children to various physiological and pathological stimuli, occurring in the body in the ontogenesis or diseases, and multifactorial origin of the pain syndrome in tics.The results suggest that one of the main mechanisms of development of pathological process is dysfunction of descending inhibitory control. However, further clarification of the type of polysynaptic reflex excitability in a certain patient is needed, that will allow to develop individualized approach to the choice of therapeutic interventions.

A geometric model of defensive peripersonal space

Potentially harmful stimuli occurring within the defensive peripersonal space (DPPS), a protective area surrounding the body, elicit stronger defensive reactions. The spatial features of the DPPS are poorly defined and limited to descriptive estimates of its extent along a single dimension. Here we postulated a family of geometric models of the DPPS, to address two important questions with respect to its spatial features: What is its fine-grained topography? How does the nervous system represent the body area to be defended? As a measure of the DPPS, we used the strength of the defensive blink reflex elicited by electrical stimulation of the hand (hand-blink reflex, HBR), which is reliably modulated by the position of the stimulated hand in egocentric coordinates. We tested the goodness of fit of the postulated models to HBR data from six experiments in which we systematically explored the HBR modulation by hand position in both head-centered and body-centered coordinates. The best-fitting model indicated that 1) the nervous system's representation of the body area defended by the HBR can be approximated by a half-ellipsoid centered on the face and 2) the DPPS extending from this area has the shape of a bubble elongated along the vertical axis. Finally, the empirical observation that the HBR is modulated by hand position in head-centered coordinates indicates that the DPPS is anchored to the face. The modeling approach described in this article can be generalized to describe the spatial modulation of any defensive response.

Clinical and electrophysiological studies of botulinum toxin type A to treat hemifacial spasm complicated with auricular symptoms

OBJECTIVE

To investigate the involvement of posterior auricular muscle (PAM) and the effect of botulinum toxin type A (BTX-A) injection into PAM in patients with hemifacial spasm (HFS) complicated with auricular symptoms.

METHODS

Sixty-three consecutive HFS patients complicated with auricular symptoms such as tinnitus or murmur, "ticking" or a "clicking" sound and discomfort on the same side, who were referred to our department between July 2009 and January 2010, were enrolled. The diagnosis of idiopathic HFS was made clinically. The patients were largely randomized into two BTX-A treatment groups according to the order of referral. The first group included 33 cases where the injection sites were routinely located at the frontal, orbicularis oculi, zygomaticus and buccinator muscles while the other was the PAM group, which included 30 cases, where 4 units of BTX-A were additionally injected into the PAM prior to injection at other sites. A test of blink reflex was performed and the lateral spread of blink reflex to the orbicularis oris (OO) and PAM, i.e. abnormal muscle response (AMR), was recorded and the peak-peak amplitude of AMR was measured. The patients were followed up clinically and electrophysiologically for at least 4 weeks (29.47 ± 2.53 days).

RESULTS

1) Before injection, the latencies of R1, R2, R2' were normal, there was no significant difference between uninjured and affected side; The amplitudes of R1, R2, R2' in affected side were higher. 2) After injection, there was no significant change of the R1, R2 and R2' latencies; The amplitudes of R1, R2 and R2' decreased significantly. 3) Patients reported that their auricular symptoms subsided after injection in both groups; The remission rate was 45.5% (15/33) and 76.7% (23/30) in the regular and PAM group, respectively, with a higher rate in the PAM group (χ(2) = 6.40, P = 0.011). 4) In both groups the AMR amplitude decreased significantly after injection. In the regular group, the respective OO amplitudes (μV) before and after injection were 304.00 ± 30.34 and 129.33 ± 9.59 (t = 5.820, P = 0.000), and for PAM the amplitudes were 298.00 ± 33.28 and 184.67 ± 20.21 (t = 2.818, P = 0.014); in the PAM group, the before and after injection OO amplitudes were 405.33 ± 66.71 and 116.00 ± 9.99 (t = 4.214, P = 0.001), and for PAM they were 390.00 ± 53.58 and 72.00 ± 9.67 (t = 6.011, P = 0.000), respectively. 5) PAM amplitudes in the PAM group decreased more significantly after BTX-A injection compared with those in the regular group (t = 4.237, P = 0.001).

CONCLUSIONS

The treatment on HFS with local injection of BTX-A is very effective. In HFS complicated with auricular symptoms patients, electrophysiological studies are helpful for guiding treatment plans, and the auricular symptoms could be improved by BTX-A injection into the PAM in addition to the regular injection sites.

Effects of subthalamic deep brain stimulation on blink abnormalities of 6-OHDA lesioned rats

Parkinson's disease (PD) patients and the 6-hydroxydopamine (6-OHDA) lesioned rat model share blink abnormalities. In view of the evolutionarily conserved organization of blinking, characterization of blink reflex circuits in rodents may elucidate the neural mechanisms of PD reflex abnormalities. We examine the extent of this shared pattern of blink abnormalities by measuring blink reflex excitability, blink reflex plasticity, and spontaneous blinking in 6-OHDA lesioned rats. We also investigate whether 130-Hz subthalamic nucleus deep brain stimulation (STN DBS) affects blink abnormalities, as it does in PD patients. Like PD patients, 6-OHDA-lesioned rats exhibit reflex blink hyperexcitability, impaired blink plasticity, and a reduced spontaneous blink rate. At 130 Hz, but not 16 Hz, STN DBS eliminates reflex blink hyperexcitability and restores both short- and long-term blink plasticity. Replicating its lack of effect in PD patients, 130-Hz STN DBS does not reinstate a normal temporal pattern or rate to spontaneous blinking in 6-OHDA lesioned rats. These data show that the 6-OHDA lesioned rat is an ideal model system for investigating the neural bases of reflex abnormalities in PD and highlight the complexity of PD's effects on motor control, by showing that dopamine depletion does not affect all blink systems via the same neural mechanisms.

Frequency matters: beta-band subthalamic nucleus deep-brain stimulation induces Parkinsonian-like blink abnormalities in normal rats

The synchronized beta-band oscillations in the basal ganglia-cortical networks in Parkinson's disease (PD) may be responsible for PD motor symptoms or an epiphenomenon of dopamine loss. We investigated the causal role of beta-band activity in PD motor symptoms by testing the effects of beta-frequency subthalamic nucleus deep-brain stimulation (STN DBS) on the blink reflex excitability, amplitude, and plasticity in normal rats. Delivering 16 Hz STN DBS produced the same increase in blink reflex excitability and impairment in blink reflex plasticity in normal rats as occurs in rats with 6-hydroxydopamine lesions and patients with PD. These deficits were not an artifact of STN DBS because, when these normal rats received 130 Hz STN DBS, their blink characteristics were the same as without STN DBS. To demonstrate that the blink reflex disturbances with 16 Hz STN DBS were frequency specific, we tested the same rats with 7 Hz STN DBS, a theta-band frequency typical of dystonia. In contrast to beta stimulation, 7 Hz STN DBS exaggerated the blink reflex plasticity as occurs in focal dystonia. Thus, without destroying dopamine neurons or blocking dopamine receptors, frequency-specific STN DBS can be used to create PD-like or dystonic-like symptoms in a normal rat.

Lateralized nociceptive blink reflex habituation deficit in episodic cluster headache: Correlations with clinical features

BACKGROUND

We previously observed impaired habituation mechanisms of the conventional blink reflex (BR) in patients with episodic cluster headache (ECH) during the bout, studying only the affected side. Here, we have studied the nociceptive-specific BR (nBR) both on the affected and non-affected sides, and in relation to clinical features.

PARTICIPANTS AND METHODS

We recorded nBR in 18 ECH patients during the bout, and in 18 healthy volunteers (HVs). We compared pain threshold, area, and habituation of the nBR, recorded both for the affected and non-affected sides.

RESULTS

In patients, the pain threshold on the affected side was lower than that of the non-affected side (p = 0.009), and lower than in HVs (p = 0.038). Reflex area was decreased on both sides (p < 0.05) compared with HVs, whereas habituation was significantly impaired only on the affected side (p = 0.025 vs. HVs; p = 0.003 vs. non-affected). The habituation slope was positively correlated with the number of days since the onset of the bout and the daily attack frequency.

CONCLUSIONS

Our data reflect lateralized pathological variations in craniofacial nociception in ECH patients over the course of the cluster period. We hypothesized that this is due to malfunctioning of mechanisms that regulate hypothalamic activity and descending aminergic controls.

Nociception specific supraorbital nerve stimulation may prevent cluster headache attacks: serendipity in a blink reflex study

BACKGROUND

In cluster headache, neuromodulation is offered when patients are refractory to pharmacological prophylaxis. Non-invasive peripheral neuromodulatory approaches are of interest. We will focus on these and particularly on nociception specific, transcutaneous supraorbital nerve stimulation.

METHODS

In a study using the nociception specific blink reflex, we made a serendipitous discovery, notably the potential prophylactic effect of bilateral, time contingent, nociception specific, transcutaneous stimulation of the supraorbital nerve.

RESULTS

We report on a case series of seven cluster headache patients, in whom attacks seemed to disappear during repeated stimulation of the supraorbital nerves. Three patients stopped experiencing attacks since study participation.

CONCLUSIONS

Bilateral, time contingent, nociception specific, transcutaneous supraorbital nerve stimulation may have a prophylactic effect in episodic and chronic cluster headache. Given its limited side effects and its non-invasive nature, further studies to investigate this potential peripheral neuromodulatory approach for both episodic and chronic cluster headache are warranted.

Pearls and pitfalls: electrophysiology for primary headaches

BACKGROUND

Primary headaches are functional neurological diseases characterized by a dynamic cyclic pattern over time (ictal/pre-/interictal). Electrophysiological recordings can non-invasively assess the activity of an underlying nervous structure or measure its response to various stimuli, and are therefore particularly appropriate for the study of primary headaches. Their interest, however, is chiefly pathophysiological, as interindividual, and to some extent intraindividual, variations preclude their use as diagnostic tools.

AIM OF THE WORK

This article will review the most important findings of electrophysiological studies in primary headache pathophysiology, especially migraine on which numerous studies have been published.

RESULTS

In migraine, the most reproducible hallmark is the interictal lack of neuronal habituation to the repetition of various types of sensory stimulations. The mechanism subtending this phenomenon remains uncertain, but it could be the consequence of a thalamocortical dysrythmia that results in a reduced cortical preactivation level. In tension-type headache as well as in cluster headache, there seems to be an impairment of central pain-controlling mechanisms but the studies are scarce and their outcomes are contradictory. The discrepancies between studies might be as a result of methodological differences as well as patients' dissimilarities, which are also discussed.

CONCLUSIONS AND PERSPECTIVES

Electrophysiology is complementary to functional neuroimaging and will undoubtedly remain an important tool in headache research. One of its upcoming applications is to help select neurostimulation techniques and protocols that correct best the functional abnormalities detectable in certain headache disorders.

Is There a Relation between Reticular Formation and Storage Symptoms in Men

OBJECTIVE

To reveal brainstem originated pathology in men with different types of lower urinary tract symptoms blink reflex latency times were assessed.

METHODS

A total of 32 men, 16 with storage and 16 with voiding symptoms, were enrolled in the study. Blink reflex latency times were analyzed through electrical stimulation of the supraorbital nerve. Two responses in the orbicularis oculi muscle were recorded: the latency times for the early ipsilateral response, R1, and the late bilateral responses, R2.

RESULTS

The mean ages of the patients with storage and voiding symptoms were 57.31 ± 6.87 and 58.06 ± 6.29 years, respectively. The R2 latency times were significantly longer in men with storage symptoms. However, the R1 latency times were similar for the two groups.

CONCLUSION

Late blink latency times were long only in patients who had storage symptoms. An oligosynaptic path through the trigeminal nuclei, which includes one or two interneurons, is responsible for early response; however, late response is relayed through a polysynaptic path, including neurons in the reticular formation. It has also been shown that stimulation of the pontine reticular formation inhibits the micturition contraction. In some patients, storage symptoms may result from pathology that originates with the reticular formation and this pathology may lead to increases in late blink latency times. Additional studies are needed on other reflexes that are mediated through reticular formation, in order to show the possible dysfunction of the reticular formation in men with storage symptoms.

A case of cluster headache treated with rotigotine: clinical and neurophysiological correlates

BACKGROUND

Chronic cluster headache (CCH) is characterized by recurrent bouts of facial pain lasting up to 180 minutes in the absence of a long remission period.

CASE

We report the case of a 43-year-old male patient with treatment-resistant CCH, who improved with administration of transdermal rotigotine. We also evaluated the nociceptive blink reflex habituation that was reduced before the treatment (as is usual in CH patients) and normalized by transdermal rotigotine.

CONCLUSIONS

We suggest that rotigotine could represent a further therapeutic option in the treatment of drug-resistant CCH.

Cluster headache attacks and multiple sclerosis

We report the case of a patient who developed typical cluster headache attacks and was diagnosed as having multiple sclerosis (MS) at the same time. The headache attacks resolved after i.v. treatment with methylprednisolone. MR imaging showed a pontine demyelinating lesion involving the trigeminal nerve root inlet area, on the same side as the pain. The association between cluster headache and MS has been rarely described before. This case suggests that in patients with cluster headache neuroimaging is often useful in order to exclude structural lesions.

Abnormal muscle responses in hemifacial spasm: F waves or trigeminal reflexes?

OBJECTIVE

In patients with hemifacial spasm (HFS), abnormal muscle responses (AMR) are frequently present. The objective of this study was to investigate whether the afferent input of AMR is mediated by antidromic facial nerve stimulation or orthodromic trigeminal nerve stimulation.

METHODS

AMR in the orbicularis oris muscle were recorded in 28 patients with HFS. When AMR were present, they were recorded after subthreshold stimulation of the facial nerve and weak stimulation delivered to the skin.

RESULTS

AMR were recordable in 24 (86%) of the patients, and usually consisted of the early constant component (mean onset latency, 10.0 ms) and late variable component (35.3 ms), similar to R1 and R2 of the blink reflex. The early or late components of AMR, or both, were frequently elicited after subthreshold stimulation of the facial nerve (43%) and skin stimulation (88%).

CONCLUSIONS

AMR are likely to be mediated by trigeminal afferent inputs, rather than antidromic activation of the facial nerve, and are a type of trigeminal reflex.

Timing of conditioned eyeblink responses is impaired in cerebellar patients

In the present study, timing of conditioned eyeblink responses (CRs) was investigated in cerebellar patients and age-matched controls using a standard delay paradigm. Findings were compared with previously published data of CR incidences in the same patient population (Gerwig et al., 2003; Timmann et al., 2005). Sixteen patients with pure cortical cerebellar degeneration (spinocerebellar ataxia type 6 and idiopathic cerebellar ataxia), 14 patients with lesions within the territory of the superior cerebellar artery, and 13 patients with infarctions within the territory of the posterior inferior cerebellar artery were included. The affected cerebellar lobules and possible involvement of cerebellar nuclei were determined by three-dimensional magnetic resonance imaging (MRI) in patients with focal lesions (n = 27). Based on a voxel-by-voxel analysis, MRI lesion data were related to eyeblink conditioning data. CR incidence was significantly reduced, and CRs occurred significantly earlier in patients with cortical cerebellar degeneration and lesions of the superior cerebellum compared with controls. Incidence and timing of CRs was not impaired in patients with lesions restricted to the posterior and inferior cerebellum. Voxel-based MRI analysis revealed that cortical areas within the anterior lobe (Larsell lobule HV) were most significantly related to timing deficits, whereas reduced CR incidences were related to more caudal parts (lobule HVI) of the superior cerebellar cortex. The present data suggest that different parts of the superior cerebellar cortex may be involved in the formation of the stimulus association and appropriate timing of conditioned eyeblink responses in humans. Extracerebellar premotoneuronal disinhibition, however, is another possible explanation for changes in CR timing.

Eyeblink-related areas in human cerebellum as shown by fMRI

Classical eyeblink conditioning is used frequently to study the role of the cerebellum in associative learning. To understand the mechanisms involved in learning, the neural circuits that generate the eyeblink response should be identified. The goal of the present study was to examine cerebellar regions that are likely to control the human eyeblink response using event-related functional magnetic resonance imaging (fMRI). In 14 healthy volunteers eyeblinks were evoked by unilateral air-puff stimulation (total of 30 stimuli, inter-trial interval 27-44 sec). With eyes closed throughout the experiment, eyeblinks were recorded using a video-based system with infrared reflecting markers being attached to the upper eyelids. From each subject 500 scans were taken (TR = 2.2 sec, 22 slices per scan, slice thickness = 3 mm) using an echo planar imaging sequence (EPI). The statistical parametric maps of the experimental volume images were estimated with SPM99 specifying an appropriate event-related design matrix. Two main regions of significant activation were found in the ipsilateral posterior lobe of the cerebellar hemisphere. In the more anterior region the maxima of activation were located in hemispheral lobules VI and Crus I, and in the more posterior region in hemispheral lobules VIIb, Crus II and VIIIa (nomenclature according to Schmahmann et al. [2000]: MRI Atlas of the Human Cerebellum). Although less pronounced, activity was found also in corresponding areas of the contralateral cerebellar hemisphere. These eyeblink-related areas agree with trigeminal projection areas and blink reflex control areas shown in previous animal studies.

Value of blink reflex in assessing V and VII nerve function in patients with C. P. Angle tumours- a prospective study of 75 patients

This propsective study analyses the role of blink reflex (BR) in 75 patients with Cerebellopontine Angle (CPA) tumours. The aim was to find out the subclinical involvement from the blink reflex findings. Fifth nerve was clinically involved in 82.7% patients while, BR was able to detect afferent abnormality only in 54% patients. The seventh nerve was clinically involved in 74.7% and blink reflex could detect the efferent abnormality is 72% patients. Thus, clinicoelectrophysiological correlation was 56.4% and 72% for V and VII nerve respectively. In the patients in whom there was no V or VII nerve involvement BR showed VII nerve involvement in 12% patients. The subclinical involvement of the V nerve and the brainstem were detected by BR in 4% patients each. In conclusion BR is good test for the assessment of VII nerve function as compared to V nerve function. BR could pick of subclinical involvement in 20% patients.

An explanation for reflex blink hyperexcitability in Parkinson's disease. I. Superior colliculus

Hyperexcitable reflex blinks are a cardinal sign of Parkinson's disease. We investigated the neural circuit through which a loss of dopamine in the substantia nigra pars compacta (SNc) leads to increased reflex blink excitability. Through its inhibitory inputs to the thalamus, the basal ganglia could modulate the brainstem reflex blink circuits via descending cortical projections. Alternatively, with its inhibitory input to the superior colliculus, the basal ganglia could regulate brainstem reflex blink circuits via tecto-reticular projections. Our study demonstrated that the basal ganglia utilizes its GABAergic input to the superior colliculus to modulate reflex blinks. In rats with previous unilateral 6-hydroxydopamine (6-OHDA) lesions of the dopamine neurons of the SNc, we found that microinjections of bicuculline, a GABA antagonist, into the superior colliculus of both alert and anesthetized rats eliminated the reflex blink hyperexcitability associated with dopamine depletion. In normal, alert rats, decreasing the basal ganglia output to the superior colliculus by injecting muscimol, a GABA agonist, into the substantia nigra pars reticulata (SNr) markedly reduced blink amplitude. Finally, brief trains of microstimulation to the superior colliculus reduced blink amplitude. Histological analysis revealed that effective muscimol microinjection and microstimulation sites in the superior colliculus overlapped the nigrotectal projection from the basal ganglia. These data support models of Parkinsonian symtomatology that rely on changes in the inhibitory drive from basal ganglia output structures. Moreover, they support a model of Parkinsonian reflex blink hyper-excitability in which the SNr-SC target projection is critical.

An explanation for reflex blink hyperexcitability in Parkinson's disease. II. Nucleus raphe magnus

Hyperexcitable reflex blinks are a cardinal sign of Parkinson's disease. The first step in the circuit linking the basal ganglia and brainstem reflex blink circuits is the inhibitory nigrostriatal pathway (Basso et al., 1996). The current study reports the circuits linking the superior colliculus (SC) to trigeminal reflex blink circuits. Microstimulation of the deep layers of the SC suppresses subsequent reflex blinks at a latency of 5.4 msec. This microstimulation does not activate periaqueductal gray antinociceptive circuits. The brainstem structure linking SC to reflex blink circuits must suppress reflex blinks at a shorter latency than the SC and produce the same effect on reflex blink circuits as SC stimulation, and removal of the structure must block SC modulation of reflex blinks. Only the nucleus raphe magnus (NRM) meets these requirements. NRM microstimulation suppresses reflex blinks with a latency of 4.4 msec. Like SC stimulation, NRM microstimulation reduces the responsiveness of the spinal trigeminal nucleus. Finally, blocking the receptors for the NRM transmitter serotonin eliminates SC modulation of reflex blinks, and muscimol inactivation of the NRM transiently prevents SC modulation of reflex blinks. Thus, the circuit through which the basal ganglia modulates reflex blinking is (1) the substantia nigra pars reticulata inhibits SC neurons, (2) the SC excites tonically active NRM neurons, and (3) NRM neurons inhibit spinal trigeminal neurons involved in reflex blink circuits.