Histologic features of human orbicularis oculi treated with botulinum A toxin

Contribution of Single-Fiber Evaluation on Monitoring Outcomes Following Injection of Botulinum Toxin-A: A Narrative Review of the Literature

Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and is widely used for neuromuscular disorders (involuntary spasms, dystonic disorders and spasticity). However, its therapeutic effects are usually measured by clinical scales of questionable validity. Single-fiber electromyography (SFEMG) is a sensitive, validated diagnostic technique for NMJ impairment such as myasthenia. The jitter parameter (µs) represents the variability of interpotential intervals of two muscle fibers from the same motor unit. This narrative review reports SFEMG use in BoNT-A treatment. Twenty-four articles were selected from 175 eligible articles searched in Medline/Pubmed and Cochrane Library from their creation until May 2020. The results showed that jitter is sensitive to early NMJ modifications following BoNT-A injection, with an increase in the early days’ post-injection and a peak between Day 15 and 30, when symptoms diminish or disappear. The reappearance of symptoms accompanies a tendency for a decrease in jitter, but always precedes its normalization, either delayed or nonexistent. Increased jitter is observed in distant muscles from the injection site. No dose effect relationship was demonstrated. SFEMG could help physicians in their therapeutic evaluation according to the pathology considered. More data are needed to consider jitter as a predictor of BoNT-A clinical efficacy.

Rectus Femoris Characteristics in Post Stroke Spasticity: Clinical Implications from Ultrasonographic Evaluation

In stroke survivors, rectus femoris (RF) spasticity is often implicated in gait pattern alterations such as stiff knee gait (SKG). Botulinum toxin type A (BoNT-A) is considered the gold standard for focal spasticity treatment. However—even if the accuracy of injection is crucial for BoNT-A efficacy—instrumented guidance for BoNT-A injection is not routinely applied in clinical settings. In order to investigate the possible implications of an inadequate BoNT-A injection on patients’ clinical outcome, we evaluated the ultrasound-derived RF characteristics (muscle depth, muscle thickness, cross-sectional area and mean echo intensity) in 47 stroke survivors. In our sample, we observed wide variability of RF depth in both hemiparetic and unaffected side of included patients (0.44 and 3.54 cm and between 0.25 and 3.16 cm, respectively). Moreover, our analysis did not show significant differences between treated and non-treated RF in stroke survivors. These results suggest that considering the inter-individual variability in RF muscle depth and thickness, injection guidance should be considered for BoNT-A treatment in order to optimize the clinical outcome of treated patients. In particular, ultrasound guidance may help the clinicians in the long-term follow-up of muscle quality.

Over 25 Years of Pediatric Botulinum Toxin Treatments: What Have We Learned from Injection Techniques, Doses, Dilutions, and Recovery of Repeated Injections?

Botulinum toxin type A (BTXA) has been used for over 25 years in the management of pediatric lower and upper limb hypertonia, with the first reports in 1993. The most common indication is the injection of the triceps surae muscle for the correction of spastic equinus gait in children with cerebral palsy. The upper limb injection goals include improvements in function, better positioning of the arm, and facilitating the ease of care. Neurotoxin type A is the most widely used serotype in the pediatric population. After being injected into muscle, the release of acetylcholine at cholinergic nerve endings is blocked, and a temporary denervation and atrophy ensues. Targeting the correct muscle close to the neuromuscular junctions is considered essential and localization techniques have developed over time. However, each technique has its own limitations. The role of BTXA is flexible, but limited by the temporary mode of action as a focal spasticity treatment and the restrictions on the total dose deliverable per visit. As a mode of treatment, repeated BTXA injections are needed. This literature reviewed BTXA injection techniques, doses and dilutions, the recovery of muscles and the impact of repeated injections, with a focus on the pediatric population. Suggestions for future studies are also discussed.

Orbicularis Oculi Morphological Alterations in Affected and Nonaffected Sides in Hemifacial Spasm

BACKGROUND

Although the nonaffected side appears to be clinically normal in hemifacial spasm (HFS), it is not known whether this side can be considered normal regarding histopathological findings. The purpose of this study was to objectively evaluate and compare orbicularis oculi samples of patients with HFS (not previously treated with botulinum toxin) and control patients undergoing cosmetic upper eyelid blepharoplasty.

METHODS

Orbicularis oculi samples from 22 eyelids were evaluated. There were 7 samples from the affected and 7 samples from the nonaffected sides of patients with HFS who had not been previously treated with botulinum toxin, and 8 samples from normal control patients. Muscle samples were prepared using hematoxylin and eosin staining, and a digital image analysis software was used for objective analyses.

RESULTS

When compared with normal controls, endomysial and perimysial connective tissue areas were significantly increased (P = 0.015) on the affected side in HFS, suggesting that this disorder is associated with chronic alterations that lead to muscle degeneration. Cell density was significantly reduced on the affected (P = 0.028) and also on the nonaffected sides in HFS (P = 0.003) compared with normal controls. This was observed, although, clinically, there were no signs or symptoms of increased muscular contraction on the nonaffected sides in any of the patients with HFS studied.

CONCLUSIONS

Significant morphological differences in the orbicularis oculi muscle in patients with HFS were observed on both the affected and nonaffected sides. Our findings suggest a potential role for muscle homeostasis disturbances on both sides for patients with HFS. Affected sides in patients with HFS did, however, demonstrate muscle degeneration that was not present on the nonaffected sides.

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.

Muscle histopathology in children with spastic cerebral palsy receiving botulinum toxin type A

INTRODUCTION

Botulinum toxin A (BoNTA) is routine treatment for hypertonicity in children with cerebral palsy (CP).

METHODS

This single-blind, prospective, cross-sectional study of 10 participants (mean age 11 years 7 months) was done to determine the relationship between muscle histopathology and BoNTA in treated medial gastrocnemius muscle of children with CP. Open muscle biopsies were taken from medial gastrocnemius muscle and vastus lateralis (control) during orthopedic surgery.

RESULTS

Neurogenic atrophy in the medial gastrocnemius was seen in 6 participants between 4 months and 3 years post-BoNTA. Type 1 fiber loss with type 2 fiber predominance was significantly related to the number of BoNTA injections (r = 0.89, P < 0.001).

CONCLUSIONS

The impact of these changes in muscle morphology on muscle function in CP is not clear. It is important to consider rotating muscle selection or injection sites within the muscle or allowing longer time between injections.

Botulinum toxin injection for the treatment of epiphora in lacrimal outflow obstruction

PURPOSE

To describe our experience with the use of botulinum toxin (BoNTA) for the symptomatic treatment of lacrimal outflow obstruction.

METHODS

We retrospectively reviewed the case notes of patients with epiphora due to lacrimal outflow obstruction who chose to have injections of botulinum toxin into the palpebral lobe of the lacrimal gland instead of surgery between 2009 and 2014. Epiphora was graded subjectively with Munk scores obtained before and after treatment as well as qualitative degree of improvement reported by the patients. Severity and duration of side effects were also noted.

RESULTS

Seventeen patients (22 eyes, mean age 70.3, 4 males and 13 females) were identified. A mean of 3.5 (range; 1-10) injections of BoNTA (Botox, Allergan; 1.25-7.5 units) were given per eye. The mean interval between injections was 3.9 months (range 3-6). The mean Munk score (3.4, range 2-4) improved significantly after treatment to 1.6 (range: 0-3, P=0.0001 paired two-tailed t-test). Epiphora completely resolved in a fifth, improved by up to 60-90% in a half and only 'a little better' in a further fifth. Temporary bruising and diplopia (lasting 2 weeks) was reported in 12% (2/17).

CONCLUSION

We report our outcomes for BoNTA to the palpebral lobe of the lacrimal gland in patients with lacrimal outflow obstruction epiphora seeking alternatives to surgery. This data provide further evidence for informed consent and for commissioning organisations considering the funding of this treatment.

Intraglandular injection of botulinum toxin a reduces tear production in rabbits

PURPOSE

To develop an animal model and investigate the dose-dependent effect of an intraglandular injection of botulinum toxin A (BTX-A) on tear production.

METHODS

In a volume of 0.1-ml, 0.625-, 1.25-, or 2.5-U BTX-A was injected transconjunctivally in the superolateral lobe of the lacrimal gland of adult New Zealand white female rabbits. In the contralateral lacrimal gland, 0.1 ml of 0.9% sodium chloride was injected. Prior to injection and at 1-week postinjection, photographs were taken to evaluate pre- and postoperative eyelid position. Fluorescein and Rose Bengal stain were used to evaluate the corneal surface, and Schirmer test was used to assess tear production.

RESULTS

Glands injected with the intermediate (1.25 U) and the highest (2.5 U) doses of BTX-A displayed a statistically significant decrease in tear production (p = 0.002 and 0.007, respectively) compared with the contralateral saline-injected glands at 1 week. No corneal pathologic factors from excessive dryness were observed following the injection. While postinjection ptosis was observed (p = 0.025), no difference was seen between BTX-A and saline-injected eyes.

CONCLUSIONS

In rabbits, intraglandular injection of BTX-A resulted in decreased tear production at 1 week. No additional reduction in tear production was seen with a BTX-A dose greater than 1.25 U, suggesting glandular receptor saturation at this dose. Despite suppression of tear production, no corneal pathologic factors were observed. Further studies are needed to refine this animal model with the ultimate goal of determining optimum delivery route and concentration to reduction in tear production while minimizing side effects in patients.

Factors associated with symptom response to pyloric injection of botulinum toxin in a large series of gastroparesis patients

Case series report symptom reductions after pyloric botulinum toxin injection in gastroparesis, but small controlled trials show no benefit. Factors that enhance response to therapy are undefined. A retrospective analysis of 179 gastroparetics undergoing pyloric botulinum toxin injection from 2001 to 2007 assessed responses relating to drug dosing, demographic factors, comorbidities, and gastric function. Overall, there was a decrease in gastroparetic symptoms 1-4 months after pyloric botulinum toxin injection in 92 patients (51.4%). Increasing the botulinum toxin dose significantly improved clinical responses of patients who provided information on symptoms after therapy (100 units: 54.2%; 200 units: 76.7%; P=0.02). Other factors that improved response to botulinum toxin included female gender, age <50 years, and nondiabetic nonpostsurgical etiology (all P<0.05). Eighty-seven patients received 307 follow-up injections. A clinical response to a second injection was observed in 73.4% of evaluable patients. In conclusion, responses to pyloric botulinum toxin depended on dose and were maintained on repeat injection. Subgroup analyses defined subgroups likely to benefit. These findings provide the foundation for large, controlled trials of high-dose botulinum toxin in selected gastroparesis subsets.

Drug Insight: biological effects of botulinum toxin A in the lower urinary tract

Botulinum toxins can effectively and selectively disrupt and modulate neurotransmission in striated muscle. Recently, urologists have become interested in the use of these toxins in patients with detrusor overactivity and other urological disorders. In both striated and smooth muscle, botulinum toxin A (BTX-A) is internalized by presynaptic neurons after binding to an extracellular receptor (ganglioside and presumably synaptic vesicle protein 2C). In the neuronal cytosol, BTX-A disrupts fusion of the acetylcholine-containing vesicle with the neuronal wall by cleaving the SNAP-25 protein in the synaptic fusion complex. The net effect is selective paralysis of the low-grade contractions of the unstable detrusor, while still allowing high-grade contraction that initiates micturition. Additionally, BTX-A seems to have effects on afferent nerve activity by modulating the release of ATP in the urothelium, blocking the release of substance P, calcitonin gene-related peptide and glutamate from afferent nerves, and reducing levels of nerve growth factor. These effects on sensory feedback loops might not only help to explain the mechanism of BTX-A in relieving symptoms of overactive bladder, but also suggest a potential role for BTX-A in the relief of hyperalgesia associated with lower urinary tract disorders.

Botulinum neurotoxins: fundamentals for the facial plastic surgeon

The most commonly performed nonsurgical cosmetic procedure in the facial plastic surgery armamentarium involves the various commercial preparations of botulinum neurotoxins. These drugs have undergone a transformation from public health scourge to near ubiquitous therapeutic modality across the entire medical spectrum. Herein, the history of botulinum neurotoxins is reviewed, including an exploration of their pharmacology, neuromuscular junction physiology, a description of the commercially available preparations, and the recent research concerning the practicalities of their clinical use.

Is it Reasonable to Treat Refractory Voiding Dysfunction in Children With Botulinum-A Toxin?

PURPOSE

We present our results with botulinum-A toxin transperineal pelvic floor/external sphincter injection combined with behavioral and biofeedback reeducation in children with voiding dysfunction who had been resistant to previously applied therapies.

MATERIAL AND METHODS

Eight boys and 12 girls between 7 and 12 years old (mean age 9) with recurrent urinary tract infection, an interrupted or fractional voiding pattern and high post-void residual urine in whom behavioral, short biofeedback and alpha-blocker therapies had failed were included in the study. They were treated with botulinum-A toxin at a dose of 50 to 100 U. Botulinum-A toxin was injected transperineally into the pelvic floor and/or external sphincter in all patients. In boys the sphincter was localized endoscopically before injection (endoscopically assisted transperineal approach). Behavioral and biofeedback reeducation started 15 days after injection.

RESULTS

Followup was between 9 and 14 months. All patients were without urinary tract infection and fever, while 5 were still on chemoprophylaxis. Six months after treatment residual urine decreased in 17 of 20 patients by 0 to 130 ml (mean +/- SD 45.75 +/- 32.17 ml, t = 6.360, p <0.001). Nine patients reestablished a normal voiding curve and 8 showed improvement. Three did not manifest any significant improvement. In 1 girl transitory incontinence resolved spontaneously within 48 hours. There were no other complications.

CONCLUSIONS

The effect of botulinum is transitory. However, it can break the circle of detrusor-sphincter dyssynergia and the period when it is sustained can be used for retraining the patient in normal voiding. At this moment botulinum-A toxin is one of last options in refractory cases of voiding dysfunction.

Versatility of Botulinum Toxin: A Use in Stabilization of Pedicled Muscle Flaps

BACKGROUND

In this study, botulinum toxin A was used to secure the stabilization of muscle flaps without denervation atrophy.

METHODS

Thirty adult female Wistar rats were divided into a control group (group I, n = 10), a denervation group (group II, n = 10), and a botulinum toxin A group (group III, n = 10). In all of the groups, pedicled pectoralis major muscle flaps were elevated from the sternal attachment on the right side. In the second group, muscle flaps were denervated by transsecting the pectoralis major nerve after flap elevation; in the third group, botulinum toxin A (1.4 U of Dysport; Ipsen, Maidenhead, United Kingdom) was injected into the prepared muscle flap before flap replacement. The distance between the medial side of the muscle and the midline was measured at 4 weeks. Histopathological examination was performed 10 weeks after the first operation. The diameter of the muscle fibers was measured, and the degree of atrophy in the muscle flaps was evaluated in all groups.

RESULTS

Mean distances from the midline were statistically significantly different in all of the groups (p = 0.000, p < 0.01). There was a significant difference in muscle fiber diameter among the groups (p = 0.000, p < 0.01). Temporary denervation by botulinum toxin A and irreversible denervation with transsection of the motor nerve caused the reduced diameters of the muscle fibers. In addition, moderate to severe muscle atrophy in group II and mild to moderate muscle atrophy in group III were observed.

CONCLUSIONS

In the pedicled muscle flaps, botulinum toxin A can be used easily and reliably for stabilization. It was concluded that detachment of the muscle flap might be prevented and operative morbidity decreased using this method.

Acute botulinum toxin-induced muscle weakness in the anterior cruciate ligament-deficient rabbit

We established botulinum type-A toxin (BTX-A) injections as a powerful tool to cause knee extensor weakness in New Zealand White (NZW) rabbits. The purpose of this study was to determine if BTX-A induced quadriceps weakness causes muscle dysfunction beyond that caused by anterior cruciate ligament (ACL) transection in the knee of NZW rabbits. Twenty animals were randomly divided into four study groups (n=5 each); uninjected controls, BTX-A injection alone, ACL transection alone, BTX-A injection and ACL transection combined. Isometric knee extensor torque, quadriceps muscle mass, and vertical and anterior-posterior ground reaction forces were measured four weeks post single (BTX-A and ACL), unilateral intervention. Muscle weakness, muscle atrophy and decrease in ground reaction forces were all significantly greater for the experimental compared to the untreated contralateral legs. BTX-A injection produced a greater deficit in quadriceps mass and knee extensor torque than ACL transection alone, but produced smaller deficits in the ground reaction forces. ACL transection superimposed on BTX-A injection did not change either knee extensor torque production or muscle mass. Together these results suggest that BTX-A injection causes great force and muscle mass deficits, and affects functional gait in a significant manner, but it has no measurable functional effect when superimposed on ACL transection, at least not in the acute protocol tested here. Hopefully, BTX-A injection for acutely enhancing the degree of muscle weakness in otherwise untreated animals, or in experimental models of osteoarthritis, will help in investigating the role of muscle weakness in joint degeneration.

Proposed model of botulinum toxin-induced muscle weakness in the rabbit

Osteoarthritic patients show only a weak association between radiographic signs of joint disease and joint pain and disability. Conversely, muscle weakness is one of the earliest and most common symptoms of patients with osteoarthritis (OA). However, while many experimental models of osteoarthritis include a component of muscular weakness, no model has isolated this factor satisfactorily. Therefore, the purpose of this study was to develop and validate an experimental animal model of muscle weakness for future use in the study of OA. Botulinum Type-A toxin (BTX-A) was uni-laterally injected into the quadriceps musculature of New Zealand white rabbits (3.5 units/kg). Isometric knee extensor torque at a range of knee angles and stimulation frequencies, and quadriceps muscle mass, were quantified for control animals, and at one- and six-months post-repeated injections, in both, the experimental and the contralateral hindlimb. Ground reaction forces were measured in all animals while hopping across two force platforms. Isometric knee extension torque and quadriceps muscle mass was systematically decreased in the experimental hindlimb. Vertical ground reaction forces in the push off phase of hopping were also decreased in the experimental compared to control hindlimbs. We conclude that BTX-A injection into the rabbit musculature creates functional and absolute muscle weakness in a reproducible manner. Therefore, this model may be used to systematically study the possible effects of muscle weakness on joint degeneration, either as an isolated intervention, or in combination with other interventions (anterior cruciate ligament transection, meniscectomy) known to create knee joint degeneration.

Endoscopic pyloric injection of botulinum toxin A for the treatment of refractory gastroparesis

BACKGROUND

Botulinum toxin A injected into the pyloric sphincter has been reported in small case series to treat gastroparesis. This study reviews the use of this treatment in a large number of patients with gastroparesis.

METHODS

Patients who underwent pyloric botulinum injection for treatment of gastroparesis were identified. Response was defined as improvement or resolution of the patient's major symptom and/or two minor symptoms for 4 weeks.

RESULTS

Of 115 patients treated, 63 patients met the study criteria. There were 53 women, 10 men, mean age 42 years. Most patients (56%) had idiopathic gastroparesis. Twenty-seven of 63 (43%) patients experienced a symptomatic response to treatment. By stepwise logistic regression, male gender was associated with response to treatment (OR 3.27: 95% CI[1.31, 8.13], p = 0.01). Vomiting as a major symptom was associated with a lack of response (OR 0.16: 95% CI[0.04, 0.67], p = 0.01). Despite the association of male gender with response, the mean duration of response for those patients responding, with a minimum of 3 months' follow-up was 4.9 months (+/-2.7 months) for women and 3.5 months (+/-0.71 months) for men (p = 0.59). The corresponding medians and interquartile ranges (IQR) were 5 (IQR 3-6) for females and 3.5 (IQR 3-4) for males.

CONCLUSIONS

Of the patients, 43% had a response to botulinum toxin treatment that lasted a mean of approximately 5 months. Male gender was associated with a response to this therapy; however, durability of response was unrelated to gender. Vomiting as a major symptom predicted no response.

Lack of ultrastructural detrusor changes following endoscopic injection of botulinum toxin type a in overactive neurogenic bladder

INTRODUCTION

Endoscopical injections of Botulinum toxin type A into the detrusor muscle are gaining clinical acceptance in the treatment of neurogenic detrusor overactivity. Structural effects of Botulinum toxin type A are only known from studies on striated muscles, where a widespread nerve sprouting occurs temporarily. The aim of this study was to evaluate the ultrastructural effects of Botulinum toxin type A injections on the human detrusor.

MATERIAL AND METHODS

30 detrusor biopsies were obtained from 24 patients with neurogenic detrusor overactivity. Patients were divided into two groups: Group I included 13 biopsies from patients before the first Botulinum toxin type A injection. Group II included 6 biopsies from patients within 3 months after the first injection and 11 biopsies at the time of decreasing efficacy of Botulinum toxin type A. The biopsies were processed by standard procedure for detailed electron microscopic study and evaluated by 2 examiners without prior knowledge of clinical/urodynamic data.

RESULTS

No statistically significant detrusor changes have been found concerning muscle cell fascicle structure (p = 0.445), width of intercellular space (p = 0.482) and number/kind of muscle cell junctions (p = 0.443). A median of 70% of intrinsic axon terminals presented with signs of degeneration in group I, a median of 66% in group II (p = 0.840). Out of 309 evaluated axon terminals in both groups, 1 sprouting axon was found in group I, 3 sprouting axons in group II (p = 0.864). Specimen from group I and group II showed only limited collagen deposits within the detrusor. No changes in the ultrastructure of the detrusor have been observed in those biopsies obtained before and after the Botulinum toxin type A injection of the same patient.

CONCLUSION

This study verifies our earlier report of severe intrinsic axon degeneration in the detrusor of patients with neurogenic detrusor overactivity. It also shows nearly no structural differences of the detrusor before and after Botulinum toxin type A injections. Contrary to reports of striated muscle, axonal sprouting within the detrusor was very limited after Botulinum toxin type A injections indicating pathophysiologically different reactions to the toxin either between striated muscle and smooth muscle or between different treated diseases.

Botulinum toxin therapy in pain management

BTs seem to be a useful treatment in refractory MPS and headache. Presumably BTs work by breaking the spasm or pain cycle giving the patient a "window of opportunity" for traditional conservative measures to have a greater beneficial impact, but several studies suggest that a direct antinociceptive effect distinct from any reduction in muscle spasm may be at play. The major benefit of BTs compared with standard therapies is duration of response. We do not advocate that BTs be used as a first line treatment for MPS or headache. However, in refractory cases where nothing else has worked, it may offer a chance for improvement or cure not otherwise available. For now, it remains an off label, but increasingly accepted, approach in-patients with refractory myofascial pain and headache, who despite multidisciplinary approaches, continue to suffer.

Histology of nerves and muscles in adductor spasmodic dysphonia

To elucidate the etiology and pathophysiology of spasmodic dysphonia, we examined the adductor branch of the recurrent laryngeal nerve and the lateral cricoarytenoid muscle from 9 consecutive patients with this disorder who were previously treated with botulinum toxin. Histologic examination revealed average muscle fiber diameters ranging from 21 to 57 microm. Botulinum toxin treatment-related muscle atrophy was observed up to 5 months after injection. Endomysial fibrosis was present in all samples. Histochemical analysis in 8 patients revealed type 2 fiber predominance in 7 patients and fiber type grouping in 2. Type-specific muscle fiber size changes were not present. Nerve samples were examined in plastic sections. In 8 patients the nerves contained homogeneous, large-diameter myelinated nerve fibers and sparse small fibers. One patient had a relatively increased proportion of small myelinated nerve fibers. Overall, the nerve fiber diameter was slightly larger in patients than in controls. These findings may implicate the central nervous system in the pathophysiology of adductor spasmodic dysphonia.

Botulinum toxin type A induces apoptosis in nasal glands of guinea pigs

Nasal hypersecretion is predominantly caused by overaction of nasal glands, which are mainly under cholinergic control. In this work, we investigated the influence of botulinum toxin A (BTA) on the nasal mucosal tissue of the maxillary sinus turbinates of guinea pigs (n = 10) that were painlessly sacrificed 10 days (short-term group) or 3 months (long-term group) after local treatment with 20 units of BTA (Botox) or 0.2 mL of 0.9% sodium chloride (control). Histologic investigation of the nasal mucosal tissue of the BTA-treated animals (short-term group) showed degeneration of glands and ducts and apoptotic nuclei on TUNEL staining of these structures. The control animals revealed normal glandular tissue and no apoptosis. The animals of the long-term group showed almost normal glandular tissue and only a few apoptotic nuclei. In conclusion, BTA induces temporary apoptosis in the nasal glandular compartment of guinea pigs.

Botulinum toxin therapy for pain and inflammatory disorders: mechanisms and therapeutic effects

Botulinum toxin (BTX) injections are a well-recognised therapeutic modality for the treatment of regional involuntary muscle disorders and recently BTX has been used for treatment of pain and inflammatory disorders. The primary purpose of this review is to discuss the mechanism of action of therapeutic BTX in light of both the traditional understanding of BTX pharmacological effects as well as new observations. The review will deal with clinical observations and relevant animal experimentation. The data and hypotheses presented are not only relevant to botulinum toxin technology but will certainly prove important in the basic mechanisms of some of the diseases where botulinum toxin has been successfully applied. BTX used clinically comprises botulinum neurotoxin (BoNT) complexed with non-toxic proteins. The non-toxic components of the BTX complexes stabilise the labile BoNT during purification and formulation as a therapeutic. The complex proteins may also have unrecognised clinical significance such as slowing diffusion in tissues or imparting stability. The mechanisms of BTX formulations acting on SNARE proteins are briefly reviewed providing a basis for BTX clinical applications. The potential for design of improved botulinum toxins and formulations is addressed.

Pharmacology of botulinum toxin

BACKGROUND

Botulinum toxin has a well-defined role among dermatologists for the treatment of facial wrinkling, brow position, and palmar and axillary hyperhidrosis.

OBJECTIVE

The purpose of this study is to educate dermatologists on the pharmacology of botulinum toxin.

METHODS

A retrospective review of the literature on botulinum toxin from 1962 to the present was conducted. We examined the clinical applications of botulinum toxin, cholinergic neuromuscular transmission, the toxin's structure and molecular actions, drug and disease interactions at the neuromuscular junction, toxin assays, determinants of clinical response, and adverse side effects.

RESULTS

Botulinum toxin blocks the release of acetylcholine from the presynaptic terminal of the neuromuscular junction. Several drugs and diseases interfere with the neuromuscular junction and the effects of botulinum toxin. The mouse bioassay, the most sensitive and specific measurement of toxin activity, is the gold standard for botulinum toxin detection and standardization. The major determinants of clinical response to treatment are the toxin preparation, individual patient's anatomy, dose and response relationships, length of toxin storage after reconstitution, and immunogenicity. To minimize potential antibody resistance, one should use the smallest effective dose, utilize treatment intervals of more than 3 months, and avoid booster injections. Uncommon adverse effects include ptosis, ectropion, diplopia, bruising, eyelid drooping, hematoma formation, and temporary headaches.

CONCLUSION

Botulinum toxin is a safe and effective treatment. Knowledge of the pharmacologic basis of therapy will be useful for standardizing techniques and achieving consistent therapeutic results in the future.

The effects of tetanus toxin on the orbicularis oculi muscle

PURPOSE

Tetanus toxin can cause localized neuromuscular weakness, but it also can produce systemic tetany. The action of tetanus toxin on the orbicularis muscle has not been studied in animals immunized to prevent systemic tetany. Our objective was to determine whether tetanus toxin could be used to treat orbicularis oculi muscle spasms.

METHODS

We analyzed the clinical, electrophysiologic, and histopathologic effects of tetanus toxin injected into the orbicularis oculi muscle of rabbits with passive immunity to tetanus toxin. In six rabbits, the orbicularis oculi function in both eyes was assessed clinically, and the baseline orbicularis oculi muscle action potential was measured physiologically with electromyography (EMG). The rabbits then were immunized against tetanus toxin with tetanus immunoglobulin for immediate and definitive immunity. Tetanus toxin was injected into the left orbicularis oculi muscles, leaving the right eyes as controls. Ten days later, the rabbits were again assessed by clinical examination and with EMGs on both the injected side and the noninjected side. The animals were killed at 14 days, and the orbicularis muscle was removed from both sides. The injected and control tissues were examined microscopically for signs of neuromuscular denervation.

RESULTS

All six rabbits showed weakness in eye closure on the side injected with tetanus toxin. In addition, four rabbits developed complete ear ptosis on the tetanus toxin injected side because of spread of the toxin to adjacent ear muscles. EMGs showed both a denervation of the orbicularis oculi muscle and a poor blink potential on the side injected with tetanus toxin. Histopathologic studies of the orbicularis oculi muscle injected with tetanus toxin showed angulation of both slow and fast types of muscle fibers compatible with neuromuscular denervation.

CONCLUSIONS

Tetanus toxin can cause localized orbicularis oculi weakness, as documented clinically, physiologically, and microscopically, without producing systemic tetany in immunized rabbits. Tetanus toxin may have a potential application in the treatment of blepharospasm and hemifacial spasm.

Effects of botulinum toxin on pathophysiology in spasmodic dysphonia

To determine the mechanism of symptom relief with treatment by botulinum toxin injection in persons with adductor spasmodic dysphonia (ADSD), we evaluated the effects of unilateral thyroarytenoid muscle injections on both injected and noninjected muscles in 10 subjects with ADSD, using electromyography on both sides of the larynx before and after treatment. The subjects' speech symptoms were reduced (p = .005) 2 weeks following injection, when the electromyographic study occurred. Muscle activation levels and the numbers of spasmodic muscle bursts decreased significantly (p < or = .03) postinjection in both the injected and noninjected muscles. The reductions in laryngeal muscle bursts correlated with symptom reduction (r > or = .7) in all muscles. Reductions in laryngeal muscle bursts did not relate to either absolute or normalized levels of muscle activity before or after botulinum toxin injection. The results suggest that changes in the central pathophysiology are responsible for changes in speech symptoms following treatment.

Botulinum toxin A for the treatment of facial hyperkinetic wrinkle lines in Koreans

There are a number of different causes for facial wrinkle lines, such as aging, gravity, and chronic pulling of mimetic muscles on the face. Among these, pulling by mimetic muscles on the skin not only involves facial expression but also has a great role in forming facial wrinkle lines as a result of repetitive action, such as dynamic or hyperkinetic wrinkle lines. Botulinum toxin A is currently being used for eliminating facial hyperkinetic wrinkles by causing paralysis of the underlying mimetic muscles. Because there are some histologic differences between Asians and Caucasians, such as thick dermis and more abundant collagen fiber, etc., the chronic pulling by mimetic muscles on the skin is expected to affect facial wrinkles differently. Therefore, the purpose of this study was to determine the efficacy of botulinum toxin A injection in eliminating facial hyperkinetic wrinkle lines among Korean patients. This study included 38 patients and 59 injection sessions from January of 1996 to April of 1997. We used Botox containing 100 U. Toxin was diluted with 4 ml of sterile normal saline and yielded 2.5 U for each 0.1 cc. A dose of 5 to 10 U was used in each muscle. Ages ranged from 26 to 56 years. There were 33 women and 5 men included in this study. Thirty-two of the patients were followed from 3 months up to 12 months after injections. The number of injection sessions that were performed on each patient was as follows: one session, 23 patients; two sessions, 10 patients; three sessions, 4 patients; four sessions, 1 patient. The number of injections per target site among these 38 patients was as follows: lateral canthal area, 33; glabellar area, 9; forehead, 9; nasal dorsum, 5. The most common duration of effective response was about 4 months, but in eight patients the period was over 5 months. After the response, complete recovery took about 1 or 2 months. Two patients felt unsatisfied, 5 patients felt slightly improved, and 25 patients retained only a slight line and were satisfied with the results. None of the patients experienced complete removal of wrinkle lines. Adverse effects included altered facial looks or appearances, mild local swelling, and ecchymosis at the injection sites. No systemic side effects were noted. Based on these results, the injection of botulinum toxin A seems to be an effective method of eliminating wrinkle lines on the upper third of the face in Korean patients, and it was a simple and effective nonsurgical procedure.

Botox-induced prostatic involution

BACKGROUND

A simple approach to induced prostatic atrophy was explored. Surgical denervation is known to produce profound atrophy of the rat prostate. Because Botulinum toxin type A (Botox) produces a long-term chemical denervation, the potential to induce atrophy of the rat prostate was explored.

METHODS

Thirty rat prostates were injected with varying doses of Botox. Single and serial injections were used, and rats were subsequently sacrificed after either 1 or 4 weeks, respectively. The prostate glands were harvested, weighed, and histologically studied for morphologic and apoptotic changes.

RESULTS

The total prostate volume and weight were found to be reduced in all Botox-injected animals. Histologically, a generalized atrophy of the glands was observed with the H&E stain. There was also diffuse glandular apoptosis evident with the Tunel stain. There were no significant complications (e.g., urinary retention, weight loss, or hind/limb weakness).

CONCLUSIONS

Botulinum toxin type A injection into the prostate gland induces selective denervation and subsequent atrophy of the prostate. Apoptosis was seen diffusely throughout the gland. It may be possible that in the future, this long-acting neurotoxin could be used for the treatment of common pathologies of the human prostate.

Increased acute and chronic mitotic activity in rat laryngeal muscles after botulinum toxin injection

OBJECTIVES

To characterize the acute and chronic cellular effects of botulinum toxin (BT) injection into rat laryngeal muscles. A complete characterization of these effects is important because patients with focal dystonias of the head and neck are commonly treated with BT injection. Further, potential muscular changes in the larynx must be carefully delineated owing to the critical phonatory and airway protective functions of these muscles.

STUDY DESIGN

The acute and chronic cellular effects of BT injection were studied using 5'-bromo 2'-deoxyuridine (BrdU) following single and repeated BT injection into rat laryngeal muscles. BrdU is incorporated into mitotically active nuclei such that changes in cell proliferative behavior following BT injection can be monitored.

RESULTS

Increased mitotic activity was detected in the tissue samples studied following BT injection. Differences in the times of the peak distribution of BrdU-labeled cells in each laryngeal muscle were observed. This may be related to the diffusion effects of BT. Prolonged muscle fiber changes, including splitting, were also observed as the result of repeated BT injection.

CONCLUSIONS

The results of this study suggest that BT may induce a proliferative response in muscle tissue.

Botulinum toxin for the temporary treatment of involutional lower lid entropion: a clinical and morphological study

PURPOSE

A prospective study was designed to evaluate the use of botulinum toxin as a temporary treatment in patients awaiting surgical repair for involutional entropion and to compare its use with lid taping.

METHODS

Botulinum toxin was administered to 30 patients with involutional entropion (35 eyelids). These patients had all previously been using lid taping and lubricant ointment as a temporary measure whilst awaiting lid surgery. Patients' symptoms and signs were assessed before and after toxin injection. The date of entropion recurrence was recorded. Eyelid tissue from 8 patients treated with toxin and 3 control patients who had not been given toxin was obtained after surgical entropion repair and examined histologically to ensure the botulinum toxin had no potential detrimental effects on the results of surgery.

RESULTS

The toxin was simple and quick to administer. Anatomical success was achieved in 33 of the 35 eyelids with significant improvements in symptoms and signs. The mean duration of action of the toxin was 12.5 weeks. Lower lid laxity was inversely correlated with duration of toxin action. There were no consistent changes in orbicularis oculi morphology after toxin injection.

CONCLUSION

Botulinum toxin is a highly effective temporary treatment for involutional entropion with few complications and no adverse effects on the results of surgical entropion repair.

Refinement in the rehabilitation of the paralyzed face using botulinum toxin

A number of surgical procedures exist to improve facial symmetry for patients with facial paralysis. Whereas static symmetry is often improved, dynamic asymmetry frequently persists because of the imbalance of complex coordinated movements of facial expression. The paralyzed face is often distorted by the excessive pull of the normal contralateral face during emotional expression. This study reports an expanded clinical indication for botulinum toxin in patients with unilateral facial paralysis. Ten patients with facial paralysis and markedly asymmetric smiles were treated with botulinum toxin A injections into the contralateral zygomaticus major, levators labii superioris and angulii oris, or risorius muscles. Eight of the 10 patients noted improvement in the symmetry of their smiles and underwent repeat injections. The onset and duration of effect averaged 5.9 days and 3 months, respectively. Botulinum toxin therapy provides a safe and efficacious modality for refining the appearance of the paralyzed face during mimetic activity.

Botulinum-A toxin in the treatment of craniocervical muscle spasms: short- and long-term, local and systemic effects

Botulinum toxin has become the initial treatment of choice for the management of essential blepharospasm, hemifacial spasm and other craniocervical dystonias. Numerous studies have confirmed a 90% to 95% response rate. Although a number of common side effects have been reported, the occurrence and incidence of rare local complications remains poorly understood. More importantly, the acute and chronic distant effects of botulinum toxin have not been clearly elucidated. A better understanding of such effects is essential if clinicians are to appropriately advise patients on the use of this therapeutic modality. This article is based on the Duke University experience in the management of over 500 patients with craniocervical spasm disorders, combined with a review of the published literature. These disorders include essential blepharospasm, oromandibular dystonia, hemifacial spasm, and torticollis. The incidence of side effects following more than 6000 treatments with botulinum toxin is presented. Pertinent research relating to the causes of these complications is also reviewed. The most common complications of treatment with botulinum toxin are related to acute local effects resulting from chemodenervation. The most important clinical effect in this group is weakening of the levator muscle resulting in ptosis, and the corneal consequences of lagophthalmos. The latter includes exposure keratitis, dry eyes, blurred vision, and hypersecretion epiphora. Less common local effects include facial numbness, diplopia, and ectropion. Some distant effects are being observed with increasing frequency. These include pruritus, dysphagia, nausea, and a flu-like syndrome. Most significant, however, are the rare reports of generalized weakness and the documentation of EMG abnormalities distant to the site of toxin injection. This has been seen with injections for both blepharospasm and torticollis. Until further studies on the long-term distant complications of botulinum toxin are available, it is recommended that patients receive as few life-time doses of toxin as possible, consistent with adequate management of their spasms. The practice of reinjecting patients routinely every three months, or at the first return of mild spasms should be discouraged.

Long-term effects of botulinum toxin injections in spasmodic dysphonia

The purpose was to examine whether physiological changes can be found in laryngeal muscles following repeated treatment with botulinum toxin injections in spasmodic dysphonia. Seven patients whose treatment consisted of multiple unilateral thyroarytenoid injections were examined more than 6 months following their most recent botulinum toxin injection fiberoptic laryngoscopy and electromyography. Comparisons were made between injected and contralateral noninjected muscles' motor unit characteristics, muscle activation patterns, and vocal fold movement characteristics. The results demonstrated that motor unit characteristics differed between injected and noninjected muscles and that these differences were greater in patients less than 12 months since last injection. Motor unit duration differences were reduced and motor unit amplitude and numbers of turns were increased in muscles sampled over 1 year after injection. These results suggest that while the physiologic effects of botulinum toxin are reversible, the reinnervation process continues past 12 months following injection.

Extraocular muscles: basic and clinical aspects of structure and function

Although extraocular muscle is perhaps the least understood component of the oculomotor system, these muscles represent the most common site of surgical intervention in the treatment of strabismus and other ocular motility disorders. This review synthesizes information derived from both basic and clinical studies in order to develop a better understanding of how these muscles may respond to surgical or pharmacological interventions and in disease states. In addition, a detailed knowledge of the structural and functional properties of extraocular muscle, that would allow some degree of prediction of the adaptive responses of these muscles, is vital as a basis to guide the development of new treatments for eye movement disorders.

Types and time course of the alterations induced in monkey blink movements by botulinum toxin

The alterations induced in eyelid movement metrics subsequent to unilateral injections of botulinum toxin type A into the orbicularis oculi muscle were studied in chronic alert monkeys using the search coil technique. Botulinum toxin caused rapid paralysis of blinks in the treated eyelid. The amplitude and peak velocity of blinks generated by this eyelid remained at or below 20% of that of the fellow, untreated eyelid for 10-20 days. Blink amplitude gain increased linearly thereafter, attaining control values by 40-60 days after injection. Recovery of blink peak velocity was slower. The adaptive alterations in blink duration that were observed during the acute phase of toxin paralysis suggest that the mechanisms responsible for blink reflex plasticity may produce bilateral adjustments in eyelid function. Taken together, these data establish a quantitative data base that can be exploited in order to: (1) better understand the neural adaptive mechanisms that operate during eyelid movements and (2) allow quantitative comparisons between current treatment protocols that employ botulinum toxin and protocols that may lead to improvements in the treatment of chronic eyelid spasm (blepharospasm).