Electrical activation of the orbicularis oculi muscle does not increase the effectiveness of botulinum toxin type A in patients with blepharospasm

Botulinum toxin modulates the blink reflex via the trigeminal afferent system in hemifacial spasm: an early and late-term effect

BACKGROUND

There is growing evidence that botulinum neurotoxin (BoNT) can mediate changes at the central level through peripheral mechanisms, leading to alterations in central sensorimotor integration. However, the effect of BoNT on brainstem excitability in patients with hemifacial spasm(HFS) is not yet fully understood, and its long-term effects remain unknown.

OBJECTIVE

This study aims to investigate the impact of BoNT on the excitability of the facial nucleus in patients with idiopathic HFS.

METHODS

In order to evaluate the peripheral effect of the toxin, the amplitude of compound muscle action potential (CMAP) of orbicularis oculi (OOc) muscles was evaluated. To investigate the effects of locally injected BoNT on the brainstem, particularly the facial motor nucleus, we evaluated the amplitude and latency of the blink reflex (BR), the synkinetic responses (SR) and the ratio of contralateral R2 (cR2) amplitude of BR/CMAP amplitude in 16 patients with HFS. These measurements were performed before and after the 1 and 4 month BoNT injection.

RESULTS

Following BoNT therapy there was a significant amplitude reduction and latency prolongation of R1, iR2, cR2 and SR elicited by the stimulation of the side of BoNT injection. The mean CMAP amplitude of OOc muscle was significantly lower after BoNT injection. The ratio of cR2 amplitude/CMAP amplitude of OOc showed a significant decline after BoNT therapy.

CONCLUSION

Our study demonstrated that BoNT suppresses the excitability of facial motor neurons in idiopathic HFS via the trigeminal afferent mechanism. These effects persisted during the fourth month, despite BoNT's diminished activity.

Application of facial neuromuscular electrical stimulation (fNMES) in psychophysiological research: Practical recommendations based on a systematic review of the literature

Facial neuromuscular electrical stimulation (fNMES), which allows for the non-invasive and physiologically sound activation of facial muscles, has great potential for investigating fundamental questions in psychology and neuroscience, such as the role of proprioceptive facial feedback in emotion induction and emotion recognition, and may serve for clinical applications, such as alleviating symptoms of depression. However, despite illustrious origins in the 19th-century work of Duchenne de Boulogne, the practical application of fNMES remains largely unknown to today's researchers in psychology. In addition, published studies vary dramatically in the stimulation parameters used, such as stimulation frequency, amplitude, duration, and electrode size, and in the way they reported them. Because fNMES parameters impact the comfort and safety of volunteers, as well as its physiological (and psychological) effects, it is of paramount importance to establish recommendations of good practice and to ensure studies can be better compared and integrated. Here, we provide an introduction to fNMES, systematically review the existing literature focusing on the stimulation parameters used, and offer recommendations on how to safely and reliably deliver fNMES and on how to report the fNMES parameters to allow better cross-study comparison. In addition, we provide a free webpage, to easily visualise fNMES parameters and verify their safety based on current density. As an example of a potential application, we focus on the use of fNMES for the investigation of the facial feedback hypothesis.

Cannabidiol as an Adjunct to Botulinum Toxin in Blepharospasm - A Randomized Pilot Study

Purpose

The purpose of this study was to evaluate the safety and efficacy of low dose cannabidiol (CBD; Epidiolex) as adjunctive therapy for idiopathic adult-onset blepharospasm (BPS), as well as develop a novel objective assessment methodology to gauge response.

Methods

Prospective, randomized, double-masked, placebo-controlled crossover design of 6 months duration of 12 patients with BPS undergoing routine maximal botulinum toxin (BTX) therapy and experiencing breakthrough symptoms. Participants received their standard BTX every 3 months and were randomized to group A = CBD daily in cycle 1, followed by placebo in cycle 2 or group B = placebo followed by CBD. Videos recorded at days 0, 45, and 90 of each cycle were analyzed to quantify eyelid kinematics. The Jankovic Rating Scale (JRS) was used to provide a clinical rating.

Results

All 12 patients completed the study without adverse events. CBD decreased median eyelid closure amplitude by 19.1% (-1.66 mm, confidence interval [CI] = -3.19 to -0.14 mm, P = 0.03), decreased median eyelid closure duration by 15.8% (-18.35 ms, CI = -29.37 to -7.32 ms, P = 0.001), and increased the maximum eyelid closure velocity by 34.8% (-13.26 mm/ms, CI = -20.93 to -5.58 mm/ms, P = 0.001). The JRS showed a 0.5 reduction in severity and frequency, which was not statistically significant.

Conclusions

Low dose CBD was safely tolerated and improved several BPS kinematic parameters. The clinical scale suggested a direction of effect but may have been underpowered. Further studies are needed to better quantify the clinical relevance.

Translational Relevance

This work describes a novel assessment methodology and therapeutic approach to bBPS.

How does botulinum toxin really work?

Over the past 30 years, Botulinum toxin (BoNT) has emerged as an effective and safe therapeutic tool for a number of neurological conditions, including dystonia. To date, the exact mechanism of action of BoNT in dystonia is not fully understood. Although it is well known that BoNT mainly acts on the neuromuscular junction, a growing body of evidence suggests that the therapeutic effect of BoNT in dystonia may also depend on its ability to modulate peripheral sensory feedback from muscle spindles. Animal models also suggest a retrograde and anterograde BoNT transportation from the site of injection to central nervous system structures. In humans, however, BoNT central effects seem to depend on the modulation of afferent input rather than on BoNT transportation. In this chapter, we aimed to report and discuss research evidence providing information on the possible mechanisms of action of BoNT in relation to treatment of dystonia.

Eliciting blinks by transcutaneous electric nerve stimulation improves tear fluid in healthy video display terminal users: A self-controlled study

We aimed to elicit strong blinks among healthy video display terminal (VDT) users by periorbital transcutaneous electric nerve stimulation (TENS) and evaluate its impact on the tear fluid and visual task. Appropriate TENS conditions were evaluated to evoke strong blinks under minimum discomfort. Seventeen healthy VDT users with noninvasive Keratograph first breakup time (NIKf-BUT) 5-15 s and Ocular Surface Disease Index (OSDI) scores < 15 were recruited in this study. Before the trial, noninvasive Keratograph average breakup time (NIKa-BUT), tear meniscus height (TMH) and OSDI scores were evaluated. Before each TENS session, the volunteers played Tetris while the corresponding blink rate and Tetris scores were recorded. Then, the participants underwent 30 minutes of TENS, which evoked blinking of their right eye 20 times per minute. Tetris scores were evaluated again during TENS. The Tetris scores and corresponding blink rate were assessed after each TENS session while NIKa-BUT, TMH and OSDI scores were recorded after the third and sixth TENS sessions. We found that OSDI scores declined significantly after the sixth TENS (P = .003). The NIKa-BUT of the right eye was promoted after the sixth TENS (P = .02), and the TMH was higher after the third and sixth TENS in both eyes (P = .03, P = .03 for right eyes respectively, P = .01, P = .01 for left eyes respectively). There was no significant difference between the adjusted Tetris scores before and during TENS (P = .12). The blink rate before and after TENS were unaffected after 6 sessions (P = .61). The results indicated that periorbital TENS effectively ameliorated ocular irritation and improved tear secretion and tear film stability by eliciting strong blinks in healthy VDT users without disturbing the visual task.

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.

Abnormal Neural Responses During Reflexive Blinking in Blepharospasm: An Event-Related Functional MRI Study

BACKGROUND

The neurophysiological disruptions underlying blepharospasm, a disabling movement disorder characterized by increased blinking and involuntary muscle spasms of the eyelid, remain poorly understood.

OBJECTIVE

To investigate the neural substrates underlying reflexive blinking in blepharospasm patients compared to healthy controls using simultaneous functional MRI and surface electromyography.

METHODS

Fifteen blepharospasm patients and 15 healthy controls were recruited. Randomly timed air puffs to the left eye were used to induce reflexive eye blinks during two 8-minute functional MRI scans. Continuous surface electromyography and video recordings were used to monitor blink responses. Imaging data were analyzed using an event-related design.

RESULTS

Fourteen blepharospasm patients (10 female; 61.6 ± 8.0 years) and 15 controls (11 female; 60.9 ± 5.5 years) were included in the final analysis. Reflexive eye blinks in controls were associated with activation of the right hippocampus and in patients with activation of the left caudate nucleus. Reflexive blinks in blepharospasm patients showed increased activation in the right postcentral gyrus and precuneus, left precentral gyrus, and left occipital cortex compared to controls. Dystonia severity negatively correlated with activity in the left occipital cortex, and disease duration negatively correlated with reflexive-blink activity in the cerebellum.

CONCLUSIONS

Reflexive blinking in blepharospasm is associated with increased activation in the caudate nucleus and sensorimotor cortices, suggesting a loss of inhibition within the sensorimotor corticobasal ganglia network. The association between decreasing neural response during reflexive blinking in the cerebellum with disease duration suggests an adaptive role. © 2020 International Parkinson and Movement Disorder Society.

Central Effects of Botulinum Neurotoxin-Evidence from Human Studies

For more than three decades, Botulinum neurotoxin (BoNT) has been used to treat a variety of clinical conditions such as spastic or dystonic disorders by inducing a temporary paralysis of the injected muscle as the desired clinical effect. BoNT is known to primarily act at the neuromuscular junction resulting in a biochemical denervation of the treated muscle. However, recent evidence suggests that BoNT’s pharmacological properties may not only be limited to local muscular denervation at the injection site but may also include additional central effects. In this review, we report and discuss the current evidence for BoNT’s central effects based on clinical observations, neurophysiological investigations and neuroimaging studies in humans. Collectively, these data strongly point to indirect mechanisms via changes to sensory afferents that may be primarily responsible for the marked plastic effects of BoNT on the central nervous system. Importantly, BoNT-related central effects and consecutive modulation and/or reorganization of the brain may not solely be considered “side-effects” but rather an additional therapeutic impact responsible for a number of clinical observations that cannot be explained by merely peripheral actions.

The Use of Botulinum Toxin for Treatment of the Dystonias

Dystonias are characterized by involuntary muscle contractions, twisting movements, abnormal postures, and often tremor in various body regions. However, in the last decade several studies have demonstrated that dystonias are also characterized by sensory abnormalities. While botulinum toxin is the gold standard therapy for focal dystonia, exactly how it improves this disorder is not entirely understood. Neurophysiological studies in animals and humans have clearly demonstrated that botulinum toxin improves dystonic motor manifestations by inducing chemodenervation, therefore weakening the injected muscles. In addition, neurophysiological and neuroimaging evidence also suggests that botulinum toxin modulates the activity of various neural structures in the CNS distant from the injected site, particularly cortical motor and sensory areas. Concordantly, recent studies have shown that in patients with focal dystonias botulinum toxin ameliorates sensory disturbances, including reduced spatial discrimination acuity and pain. Overall, these observations suggest that in these patients botulinum toxin-induced effects encompass complex mechanisms beyond chemodenervation of the injected muscles.

Effect of Botulinum Toxin A Treatment on Eyelid Pressure in Eyes with Blepharospasm

OBJECTIVE

To determine the effect of botulinum toxin A (BTX-A) on the eyelid pressure in patients with benign essential blepharospasm (BEB).

METHODS

Twenty normal volunteers (10 men, 10 women; average age 59.7 ± 11.3 years) and 33 patients (12 men, 21 women; average age 61.1 ± 14.7 years) with BEB were studied. The upper and lower eyelid pressures were measured with a blepharo-tensiometer in the normal subjects (N group). The eyelid pressures and intraocular pressures (IOP) were measured before and after the BTX-A injections in the BEB patients (B group).

RESULTS

The mean eyelid pressure in the N group was 31.0 ± 6.8 mmHg for the upper eyelid and 29.9 ± 6.5 mmHg for the lower eyelid (P > 0.05). The mean eyelid pressure in the B group before treatment was 35.3 ± 7.0 mmHg for the upper eyelid and 37.8 ± 6.6 mmHg for the lower eyelid. The eyelid pressure in the B group was significantly higher than in the N group for the upper and lower eyelids (both P < 0.001). The eyelid pressure was significantly decreased after BTX-A treatment for the upper (29.9 ± 7.5 mmHg) and the lower (32.8 ± 7.0 mmHg) eyelids (both P < 0.001). The mean IOP was 15.1 ± 2.9 mmHg before, and it significantly decreased to 14.5 ± 2.8 mmHg (P = 0.020) after the BTX-A injections. The IOP was significantly correlated with the lower eyelid pressure (P = 0.0435), but not with the upper eyelid pressure (P = 0.175).

CONCLUSION

The eyelid pressure was higher in the patients with BEB. The eyelid pressure and the IOP were significantly reduced after the BTX-A injections. In addition, the IOPs were significantly correlated with the eyelid pressure of the lower eyelid.

INCREASED BLINKING MAY BE A PRECURSOR OF BLEPHAROSPASM: A LONGITUDINAL STUDY

OBJECTIVE

The aim of this five-year longitudinal study was to investigate whether patients with increased blinking develop orbicularis oculi muscle spasms.

METHODS

Eleven patients who initially manifested increased blinking alone were clinically and neurophysiologically re-evaluated five years later.

RESULTS

By the five-year follow-up assessment, nine of the 11 patients had developed orbicularis oculi muscle spasms. The blink reflex recovery cycle became abnormal whereas somatosensory temporal discrimination, already abnormal at the first evaluation, did not significantly change.

CONCLUSIONS

Our longitudinal study demonstrates that increased blinking may precede blepharospasm and that an abnormal blink reflex recovery cycle reflects the development of orbicularis oculi muscle spasms.

Blepharospasm 40 years later

Forty years ago, C.D. Marsden proposed that blepharospasm should be considered a form of adult-onset focal dystonia. In the present paper, we provide a comprehensive overview of the findings regarding blepharospasm reported in the past 40 years. Although prolonged spasms of the orbicularis oculi muscles remain the clinical hallmark of blepharospasm, patients with blepharospasm may be characterized by various types of involuntary activation of periocular muscles. In addition to motor features, blepharospasm patients may also have nonmotor manifestations, including psychiatric, mild cognitive, and sensory disturbances. The various motor and nonmotor symptoms are not present in all patients, suggesting that blepharospasm is phenomenologically a heterogeneous condition. This emphasizes the need for tools for severity assessment that take into account both motor and nonmotor manifestations. The cause of blepharospasm remains elusive, but several lines of evidence indicate that blepharospasm is a multifactorial condition in which one, or several, as yet unknown genes together with epigenetic and environmental factors combine to reach the threshold of the disease. Although blepharospasm was originally believed to be solely a basal ganglia disorder, neurophysiological and neuroimaging evidence point to anatomical and functional involvement of several brain regions. The contribution of multiple areas has led to the hypothesis that blepharospasm should be considered as a network disorder, and this might reflect the varying occurrence of motor and nonmotor manifestations in blepharospasm patients. Despite advances in the aetiology and pathophysiology, treatment remains symptomatic. © 2017 International Parkinson and Movement Disorder Society.

Botulinum toxin and blink rate in patients with blepharospasm and increased blinking

OBJECTIVE

The aim of the study was to investigate the effect of botulinum toxin (BoNT) on blink rate (BR) in patients with blepharospasm (BSP) and increased blinking (IB).

METHODS

37 patients with a clinical diagnosis of primary BSP (19 patients had tonic orbicularis oculi (OO) spasms and 18 patients had clonic OO spasms) and 8 patients with IB were included in this case-control study. All subjects underwent a standardised video protocol and clinical evaluation with a validated questionnaire designed to identify eye symptoms and Blepharospasm Disability Index (BSDI) before and 1 month after BoNT injection. BR was measured from the video recording before and after BoNT. BR in BSP and IB patients was compared with that from a group of healthy subjects and from a group of patients with hemifacial spasm (HFS). BR in HFS was also measured before and after BoNT.

RESULTS

BR was increased in patients with IB and in BSP patients with clonic spasms but not in BSP patients with tonic spasms. BoNT reduced BR in patients with IB and in patients with clonic spasms, but not in patients with tonic spasms. BoNT left BR in patients with HFS unchanged. Changes in BR after BoNT were also independent of the presence of ocular symptoms. Despite the differential response of BR, BoNT significantly reduced BSDI in patients with BSP and IB.

CONCLUSIONS

BoNT differentially modulates BR in patients with BSP and IB depending on the baseline BR. BoNT injection reduces BR only when the blink generator is overactive, possibly influencing tear film retention.

Toward sophisticated basal ganglia neuromodulation: Review on basal ganglia deep brain stimulation

This review presents state-of-the-art knowledge about the roles of the basal ganglia (BG) in action-selection, cognition, and motivation, and how this knowledge has been used to improve deep brain stimulation (DBS) treatment of neurological and psychiatric disorders. Such pathological conditions include Parkinson's disease, Huntington's disease, Tourette syndrome, depression, and obsessive-compulsive disorder. The first section presents evidence supporting current hypotheses of how the cortico-BG circuitry works to select motor and emotional actions, and how defects in this circuitry can cause symptoms of the BG diseases. Emphasis is given to the role of striatal dopamine on motor performance, motivated behaviors and learning of procedural memories. Next, the use of cutting-edge electrochemical techniques in animal and human studies of BG functioning under normal and disease conditions is discussed. Finally, functional neuroimaging studies are reviewed; these works have shown the relationship between cortico-BG structures activated during DBS and improvement of disease symptoms.

Treatment with botulinum toxin: An update

Botulinum neurotoxin (BoNT) is a potent toxin produced by the anaerobic bacterium clostridium botulinum. It causes flaccid, long-lasting, local and reversible paralysis. In addition, BoNT inhibits the secretion of the exocrine glands and could have properties in the control of pain. Thus, BoNT is useful in the treatment of many neuromuscular conditions where an increase of muscle tone is associated with the pathogenic mechanism. Furthermore, BoNT is recommended in the treatment of some hypersecretion disorders of the exocrine gland and could play a role in the treatment of migraine and other chronic pain conditions. In the BoNT therapy adverse effects are usually mild and reversible. However, repeated injections of BoNT can lead to the development of neutralizing antibodies that can subsequently inhibit the biological activity of the toxin. In this sense, many factors can influence the immunogenicity of the BoNT, such as product-related factors, the dose of BoNT used, the frequency of injection and the previous exposure to the toxin. In this review, we are going to discuss the current clinical applications of BoNT with a special focus on evidence, doses, injection technique and adverse effects for those applications more frequently used in neurology, namely spasticity, blepharospasm, hemifacial spasm, cervical dystonia and other focal dystonias, as well as chronic migraine, tremor, sialorrhea, facial palsy, neurogenic bladder and many other neurological condition.

Is increased blinking a form of blepharospasm?

OBJECTIVE

The aim of this study was to investigate whether increased blink rate (BR) is part of the clinical spectrum of primary blepharospasm (BSP).

METHODS

We enrolled 40 patients (16 patients with an increased BR but without typical orbicularis oculi [OO] spasms, and 24 patients with typical involuntary OO spasms) and 18 healthy subjects. The BR, blink reflex recovery cycle, and somatosensory temporal discrimination threshold (STDT) were tested in patients and controls.

RESULTS

Patients who had typical OO spasms had an altered R2 recovery cycle whereas those who had an increased BR alone had a normal blink reflex recovery cycle. STDT values were higher in patients than in healthy subjects and no difference was found in the STDT abnormalities in the 2 groups of patients.

CONCLUSIONS

Our study shows that, despite the similar STDT abnormalities, the different changes in the R2 recovery cycle in patients with BSP and those with increased BR alone suggest that these disorders arise from different pathologic mechanisms.

Kinematic and diffusion tensor imaging definition of familial Marcus Gunn jaw-winking synkinesis

Background

Marcus Gunn jaw-winking synkinesis (MGJWS) is characterized by eyelid ptosis, which disappears during jaw movement. Familial MGJWS is an extremely rare condition. Some authors suggested that MGJWS is due to neural misdirection in the brainstem whereas others suggested that aberrant reinnervation or ephapse may be responsible for synkinetic activity. Pathogenesis of this condition is therefore still unclear.

Methodology/Principal Findings

To investigate pathogenetic mechanism in familial MGJWS we performed neurophysiological (EMG, Blink Reflex, Recovery cycle of the R2 component of the blink reflex, Masseter inhibitory reflex, BAEPS and kinematic analysis) and neuroradiological (MRI, Diffusion Tensor Imaging) investigations in a member of a multigenerational family with autosomal dominant Marcus Gunn jaw-winking synkinesis (MGJWS). Kinematic analysis of eyelid and jaw movements disclosed a similar onset and offset of the eyelid and jaw in both the opening and closing phases. The excitability of brainstem circuits, as assessed by the blink reflex recovery cycle and recovery index, was normal. Diffusion Tensor Imaging revealed reduced fractional anisotropy within the midbrain tegmentum.

Conclusions/Significance

Kinematic and MRI findings point to a brainstem structural abnormality in our familial MGJWS patient thus supporting the hypothesis of a neural misdirection of trigeminal motor axons to the elevator palpebralis muscle.

Botulinum toxin physiology in focal hand and cranial dystonia

The safety and efficacy of botulinum toxin for the treatment of focal hand and cranial dystonias are well-established. Studies of these adult-onset focal dystonias reveal both shared features, such as the dystonic phenotype of muscle hyperactivity and overflow muscle contraction and divergent features, such as task specificity in focal hand dystonia which is not a common feature of cranial dystonia. The physiologic effects of botulinum toxin in these 2 disorders also show both similarities and differences. This paper compares and contrasts the physiology of focal hand and cranial dystonias and of botulinum toxin in the management of these disorders.

Neurophysiological changes after intramuscular injection of botulinum toxin

Botulinum toxin (BT) acts peripherally by inhibiting acetylcholine release from the presynaptic neuromuscular terminals and by weakening muscle contraction. Therefore, its clinical benefit is primarily due to its peripheral action. As a result, local injection of BT has become a successful and safe tool in the treatment of several neurological and non-neurological disorders. Studies in animals have also shown that the toxin can be retrogradely transported and even transcytosed to neurons in the central nervous system (CNS). Further human studies have suggested that BT could alter the functional organisation of the CNS indirectly through peripheral mechanisms. BT can interfere with and modify spinal, brainstem and cortical circuits, including cortical excitability and plasticity/organisation by altering spindle afferent inflow directed to spinal motoneurons or to the various cortical areas. It is well demonstrated that the distant CNS effects of BT treatment parallel the peripheral effect, although there is limited evidence as to the cause of this. Therefore, further studies focussed on central changes after BT treatment is needed for a better understanding of these non-peripheral effects of BT.