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

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.

The pathogenesis of blepharospasm

Blepharospasm is a focal dystonia characterized by involuntary tetanic contractions of the orbicularis oculi muscle, which can lead to functional blindness and loss of independent living ability in severe cases. It usually occurs in adults, with a higher incidence rate in women than in men. The etiology and pathogenesis of this disease have not been elucidated to date, but it is traditionally believed to be related to the basal ganglia. Studies have also shown that this is related to the decreased activity of inhibitory neurons in the cerebral cortex caused by environmental factors and genetic predisposition. Increasingly, studies have focused on the imbalance in the regulation of neurotransmitters, including dopamine, serotonin, and acetylcholine, in blepharospasm. The onset of the disease is insidious, and the misdiagnosis rate is high based on history and clinical manifestations. This article reviews the etiology, epidemiological features, and pathogenesis of blepharospasm, to improve understanding of the disease by neurologists and ophthalmologists.

Quantitative assessment of botulinum toxin injection on blink rate in blepharospasm

PURPOSE

To objectively measure the blink rate in patients with blepharospasm managed by botulinum toxin type-A injections.

METHODS

In this prospective, non-interventional case series, the complete blink rates of subjects were measured before incobotulinumtoxina injection and at follow-up within 4 weeks using slow-motion video-taping. Additionally, subjects graded the frequency of blinking, the severity of light-sensitivity, and the severity and frequency of dry eye symptoms on a categorical visual analog scale. The results are reported as median (range).

RESULTS

Ten subjects were enrolled, with nine females. The total duration of treatment was 70 (5-116) months with total of 27.5 (2-51) injections. The subjects were grouped as short-time (<52w) or long-time (>52w) treatments. The median age, follow-up time, and injected doses were 73.5 (49-81) years, 21 (14-28) days, and 38 (8-47) units, respectively, with no significant difference between groups. The total complete blinks per minute before incobotulinumtoxina injection was 39 (23-64) which decreased to 18.5 (1-60) at follow-up (p = 0.004). The average change in complete blink rate was -67.4 ± 23.7% in long-time and -45.2 ± 31.2% in short-time groups (mean ± SD, p = 0.01). The total self-graded frequency of blinking and light-sensitivity decreased significantly at follow-up (p = 0.004, p = 0.047, respectively). Similar patterns of subject reported grades were seen in both groups.

CONCLUSION

Videotaping is a low-cost method for objective measurement of blink rate in blepharospasm patients after incobotulinumtoxina injection. There was a significant reduction in blink rate after incobotulinumtoxina injections with higher percentage of change in the long-time treatment group. Incobotulinumtoxina injection also significantly improves subjective photophobia.

Dry eye disease and blinking behaviors: A narrative review of methodologies for measuring blink dynamics and inducing blink response

Dry eye disease (DED) is a leading cause of ophthalmology clinical encounters with prevalence ranging from 8.7% to 64% in various populations. Blinking is an endogenous process to refresh the tear film, clear debris and maintain quality vision. Altered blinking behavior is a common feature of DED and is implicated in the pathology of the disease. However, lack of a comprehensive review on the relationship between altered blinking behavior and DED is notable in the literature. Blinking behavior may be an effect of DED due to an unstable tear film sensitizing a motor response or be its cause due to destabilization of the tear film in conditions such as benign essential blepharospasm. In this comprehensive review, we summarize the current models and theories of tear film dynamics and blinking behavior to better understand their connection to DED and introduce contemporary technologies and measurement tools used in the evaluation and induction of blinking behavior. We also describe future directions of research to better understand the relationship between DED and blinking and explore therapies that address the abnormal blinking component of DED.

Video analysis of patients with blepharospasm and lower face dystonias

Background

Blepharospasm (BSP) is a focal dystonia. There is a lack of standardization in the length of time necessary to get a measure of BSP severity for rating scales.

Objectives

1) Determine the difference between evaluating the number of eye closures in patients with blepharospasm in 1 vs. 2 min. 2) Characterize the prevalence, phenomenology and concordance of sensory trick in subjects with only blepharospasm compared to those with blepharospasm associated with other dystonias of the head.

Methods

Thirty-eight, 2-min-long standardized videos of subjects with BSP without any other dystonias were reviewed (group1). Eye closure rate was measured in 0-60 s vs. 60-120 s. Wilcoxon signed-rank test and Spearman correlation coefficient were used to compare the eye closure rate between these two intervals. An additional 68 standardized videos of subjects with blepharospasm associated with dystonia of the head were reviewed (group2). Presence, phenomenology and concordance between what subjects verbally reported as their sensory trick and what they demonstrated was classified for both groups then qualitatively compared.

Results/conclusion

Eye closure rates between 0-60 s and 0-120 s were not statistically different. There is no added benefit of counting the number of eye closures in 2 min, compared to 1 min, in patients with BSP. Sensory trick was reported by 57% of subjects with BSP and 80% of subjects who have blepharospasm and other dystonias of the head. With 100% and 97% concordance, patients' self-reported sensory trick accurately describes the movements that alleviate their dystonic movements.

Blink index as a response predictor of blepharospasm to botulinum neurotoxin-A treatment

PURPOSE

We investigated the blink profiles and blink index using ocular surface interferometer in the patients with blepharospasm (BSP) and identified points to consider predictive factor after BSP treatment.

METHODS

In total, 117 eyelids of 59 elderly patients and 20 eyelids of 10 age-matched control group were studied. All BSP patients applied botulinum toxin-A (BoNT-A) injection for treatment of BSP. An ocular surface interferometer (LipiView; TearScience, Morrisville, NC, USA) was used to measure blink profile and blink index; total and incomplete blinks/20 s, and the partial blink ratio (PBR). Eyelid blink time (including lid closing time, closure time, lid opening time), interblink times (IBT), closing speeds (OS), and opening speeds (OS) were analyzed using 600 blinks recorded over 20 s.

RESULTS

Total blink rate was significantly higher in BSP patients compared to the age-matched control group (p = .029) but other time-related and speed-related index including interpalpebral fissure, PBR, blink time, closure time (CT), interblink time, CS, and OS were not significantly different. In the responder of BSP patients, the average age was higher, CT was shorter, CS was faster than nonresponder (age; p = .016, CT; p < .001, CS; p = .042).

CONCLUSION

The blink index by analyzing the blink profile using ocular surface interferometer, and this blink index may be used as a predictive factor for evaluating the clinical response after BoNT-A injection in blepharospasm patients.

Effect of Botulinum Toxin on Non-Motor Symptoms in Cervical Dystonia

Patients with cervical dystonia (CD) may display non-motor symptoms, including psychiatric disturbances, pain, and sleep disorders. Intramuscular injection of botulinum toxin type A (BoNT-A) is the most efficacious treatment for motor symptoms in CD, but little is known about its effects on non-motor manifestations. The aim of the present study was to longitudinally assess BoNT-A's effects on CD non-motor symptoms and to investigate the relationship between BoNT-A-induced motor and non-motor changes. Forty-five patients with CD participated in the study. Patients underwent a clinical assessment that included the administration of standardized clinical scales assessing dystonic symptoms, psychiatric disturbances, pain, sleep disturbances, and disability. Clinical assessment was performed before and one and three months after BoNT-A injection. BoNT-A induced a significant improvement in dystonic symptoms, as well as in psychiatric disturbances, pain, and disability. Conversely, sleep disorders were unaffected by BoNT-A treatment. Motor and non-motor BoNT-A-induced changes showed a similar time course, but motor improvement did not correlate with non-motor changes after BoNT-A. Non-motor symptom changes after BoNT-A treatment are a complex phenomenon and are at least partially independent from motor symptom improvement.

Blepharospasm, Oromandibular Dystonia, and Meige Syndrome: Clinical and Genetic Update

Meige syndrome (MS) is cranial dystonia characterized by the combination of upper and lower cranial involvement and including binocular eyelid spasms (blepharospasm; BSP) and involuntary movements of the jaw muscles (oromandibular dystonia; OMD). The etiology and pathogenesis of this disorder of the extrapyramidal system are not well-understood. Neurologic and ophthalmic examinations often reveal no abnormalities, making diagnosis difficult and often resulting in misdiagnosis. A small proportion of patients have a family history of the disease, but to date no causative genes have been identified to date and no cure is available, although botulinum toxin A therapy effectively mitigates the symptoms and deep brain stimulation is gaining increasing attention as a viable alternative treatment option. Here we review the history and progress of research on MS, BSP, and OMD, as well as the etiology, pathology, diagnosis, and treatment.

Pretarsal blepharospasm: Clinical and electromyographic characteristics

OBJECTIVE

To describe the clinical and electromyographic characteristics of blepharospasm caused by selective involvement of the pars pretarsalis of the orbicularis oculi muscle.

METHODS

Clinical assessment and simultaneous electromyographic recordings from levator palpebrae superioris and pars orbitaria and pretarsalis of orbicularis oculi muscles were performed in patients with blepharospasm and primary failure to botulinum toxin injections. Patients with selective abnormal electromyographic activity of the pars pretarsalis of the orbicularis oculi muscle were identified and treated with selective pretarsal injections of botulinum toxin.

RESULTS

We found 24 patients with pretarsal blepharospasm confirmed by the electromyographic assessment. All of them were functionally blind. Three clinical-electromyographic patterns were identified: (a) Impairment of eyelid opening; (b) Increased blinking; (c) Spasms of eye closure combined with varying degrees of excessive blinking and impairment of eye-opening. Pretarsal injections of botulinum toxin induced a significant improvement in all patients and 50 % regained normal or near-normal vision. The clinical improvement was sustained after repeated pretarsal injections.

CONCLUSIONS

Pretarsal blepharospasm can be suspected on clinical grounds and it can be confirmed by electromyographic recordings.

SIGNIFICANCE

Recognition of this type of blepharospasm is important because of its excellent response to botulinum toxin injections applied into the pretarsal part of the orbicularis oculi muscle.

Increased pupillary constriction velocity in benign essential blepharospasm associated with photophobia

We evaluated whether the pupillary light reflex is altered in benign essential blepharospasm patients. Twenty-three patients with benign essential blepharospasm, 47 with reflex blepharospasm, and 29 dry eye disease controls were included. Pupillary light reflex-related parameters were measured under mesopic (10 lux) and photopic illuminance (200 lux) using an infrared pupillometer. Additionally, we assessed photophobia grade, eyelid function, and dry eye disease-related parameters. There were no differences in age, sex predominance, or dry eye disease-related parameters among the three groups, or in photophobia grade and eyelid function between benign essential blepharospasm and reflex groups. Constriction velocity and maximum constriction velocity in the mesopic condition were significantly greater in the benign essential blepharospasm group (3.26 ± 0.56 and 5.27 ± 0.90 mm/s) than in reflex (2.86 ± 0.62 and 4.59 ± 1.00 mm/s) or dry eye disease groups (2.96 ± 0.46 and 4.72 ± 0.67 mm/s). Constriction velocity and maximum constriction velocity in the mesopic condition positively correlated with photophobia grade (r = 0.525 and 0.617, P = 0.025 and 0.006) in the benign essential blepharospasm group. Pupillary light reflex may be related to the pathophysiology of benign essential blepharospasm with photophobia. Further studies are required to reveal connections among pupillary light reflex, photophobia, and focal dystonia in benign essential blepharospasm patients with photophobia.

Writing, reading, and speaking in blepharospasm

The aim of the study was to evaluate the effects of writing, reading, and speaking on orbiculari oculi (OO) muscle spasms and on the blink rate in patients with blepharospasm (BSP). Patients with hemifacial spasm (HFS) and healthy subjects (HS) acted as control subjects. Thirty patients with BSP, 20 patients with primary HFS and 20 age-matched healthy subjects were videotaped according to a standardized procedure: at rest with eyes open; while writing a standard sentence on paper; while writing a standard sentence on a blackboard keeping the head straight; during a conversation based on a simple topic (speaking task); and while reading a standard text aloud. Two independent movement disorders specialists reviewed the videotapes and measured the number of OO spasms and blinks in each segment. Writing and reading reduced the number of OO spasms in BSP patients, whereas speaking did not. On the other hand, writing, reading, and speaking did not modify spasms in HFS patients. These tasks modulated the blink rate in all the three groups of subjects (BSP, HFS, and HS). Our hypothesis is that the modulation of OO spasm in BSP during writing and reading depends on influences coming from occipital areas onto the brainstem circuits. Whether cognitive training with reading and writing may be used to improve OO muscle spasms is an issue that warrants further investigation.

A Review of Periocular Botulinum Neurotoxin on the Tear Film Homeostasis and the Ocular Surface Change

Clinical usage of botulinum neurotoxin (BoNT) in ophthalmology has dramatically increased since the 1980s and has become one of the most widely used agents for treating facial movement disorders, autonomic dysfunction and aesthetic wrinkles. Despite its high efficacy, there are some complications with periocular BoNT injections due to its chemodenervation effect. Among these, there is still controversy over the BoNT effect on tear film homeostasis and the ocular surface. A periocular BoNT injection could dry the eye by reducing tear production of the lacrimal gland and increase tear evaporation due to potential eyelid malposition and abnormal blinks. On the contrary, the injection of BoNT in the medial eyelids could treat dry eye disease by impairing lacrimal drainage. Regarding the ocular surface change, corneal astigmatism and high-order aberrations may decrease due to less eyelid tension. In conclusion, the entire awareness of the effect of BoNT and the patients' ocular condition is crucial for successful and safe results.

Increase lipid tear thickness after botulinum neurotoxin A injection in patients with blepharospasm and hemifacial spasm

The aim of this study was to investigate changes in the tear film lipid layer thickness (LLT) and aqueous tear production after botulinum neurotoxin A (BoNT) injection in patients with benign essential blepharospasm (BEB) and hemifacial spasm (HFS). Eleven and six patients with BEB and HFS, respectively, who received BoNT injection were consecutively enrolled in this prospective study. The blepharospasm disability index (BSDI), blink pattern, dry eye symptoms, Schirmer test 1 findings, LLT, eyelid performance, and corneal integrity were evaluated before and after treatment. Both BEB and HSF patients experienced remarkable relief from spasms and ocular discomfort after BoNT injection. LLT, the partial blink rate, the snap-back time, the lid distraction distance, and lateral canthal laxity were significantly increased at 1 month after treatment. There were no significant changes in Schirmer test 1 findings and meibomian gland dropout. Our findings suggest that LLT, a decisive factor for tear film stability, significantly increases at 1 month after BoNT injection for BEB and HFS. A decrease in BSDI and an increase in the snap-back time may contribute to the increase in LLT; this mechanism is probably responsible for the relief from dryness after BoNT injection in patients with facial movement disorders.

Objective, computerized video-based rating of blepharospasm severity

OBJECTIVE

To compare clinical rating scales of blepharospasm severity with involuntary eye closures measured automatically from patient videos with contemporary facial expression software.

METHODS

We evaluated video recordings of a standardized clinical examination from 50 patients with blepharospasm in the Dystonia Coalition's Natural History and Biorepository study. Eye closures were measured on a frame-by-frame basis with software known as the Computer Expression Recognition Toolbox (CERT). The proportion of eye closure time was compared with 3 commonly used clinical rating scales: the Burke-Fahn-Marsden Dystonia Rating Scale, Global Dystonia Rating Scale, and Jankovic Rating Scale.

RESULTS

CERT was reliably able to find the face, and its eye closure measure was correlated with all of the clinical severity ratings (Spearman ρ = 0.56, 0.52, and 0.56 for the Burke-Fahn-Marsden Dystonia Rating Scale, Global Dystonia Rating Scale, and Jankovic Rating Scale, respectively, all p < 0.0001).

CONCLUSIONS

The results demonstrate that CERT has convergent validity with conventional clinical rating scales and can be used with video recordings to measure blepharospasm symptom severity automatically and objectively. Unlike EMG and kinematics, CERT requires only conventional video recordings and can therefore be more easily adopted for use in the clinic.