Chemodenervation for facial dystonias and wrinkles

Noncosmetic periocular therapeutic applications of botulinum toxin

Botulinum toxin blocks acetylcholine release at the neuromuscular junction. The drug which was initially found to be useful in the treatment of strabismus has been extremely effective in the treatment of variety of conditions, both cosmetic and noncosmetic. Some of the noncosmetic uses of botulinum toxin applications include treatment of spastic facial dystonias, temporary treatment of idiopathic or thyroid dysfunction-induced upper eyelid retraction, suppression of undesired hyperlacrimation, induction of temporary ptosis by chemodenervation in facial paralysis, and correction of lower eyelid spastic entropion. Additional periocular uses include control of synchronic eyelid and extraocular muscle movements after aberrant regeneration of cranial nerve palsies. Cosmetic effects of botulinum toxin were discovered accidentally during treatments of facial dystonias. Some of the emerging nonperiocular application for the drug includes treatment of hyperhidrosis, migraine, tension-type headaches, and paralytic spasticity. Some of the undesired side effects of periocular applications of botulinum toxin inlcude ecchymosis, rash, hematoma, headache, flu-like symptoms, nausea, dizziness, loss of facial expression, lower eyelid laxity, dermatochalasis, ectropion, epiphora, eyebrow and eyelid ptosis, lagophthalmos, keratitis sicca, and diplopia.

Profile of Xeomin® (incobotulinumtoxinA) for the treatment of blepharospasm

Even though conventional botulinum neurotoxin (BoNT) products have shown successful treatment results in patients with benign blepharospasm (BEB), the main, potential long-term side effect of BoNT use is the development of immunologic resistance due to the production of neutralizing antibody to the neurotoxin after repeated injections. Xeomin^® (incobotulinumtoxinA), a unique botulinum neurotoxin type A (BoNT/A) drug free of complexing proteins otherwise contained in all conventional BoNT/A drugs, was recently approved by US Food and Drug Administration for the treatment of cervical dystonia or blepharospasm in adults. The newly approved BoNT/A drug may overcome this limitation of previous conventional products, since it contains pure neurotoxin (150 kDa) through a manufacturing process that separates it from complexing proteins such as hemagglutinins produced by fermentation of Clostridium botulinum. Many studies have also shown that Xeomin^® has the same efficacy and safety profile as complexing protein-containing products such as Botox^® and is exchangeable with Botox^® using a simple 1:1 conversion ratio. Xeomin^® represents a new treatment option for the repeated treatment of patients with blepharospasm in that it may reduce antibody-induced therapy failure. But, long-term comparative trials in naïve patients between Xeomin^® and conventional BoNT/A drugs are required to confirm the low immunogenicity of Xeomin^®.

The effect of the Botulinum toxin-A on craniofacial development: an experimental study

In this study, we developed a novel experimental model to evaluate muscular action on bone formation and remodeling by the help of Botulinum toxin-A (BTX). Forty-nine 15-day-old male Wistar rats were put into 4 groups randomly. Group 1 was the control group. BTX 0.4 IU (0.05 mL) was injected into the right masseter muscle in group 2 and into right temporalis muscle in group 3. The same volume of sterile saline was given into the both above-mentioned muscles in group 4. At the end of the fourth month, all animals were killed. Histology and weight of the masseter and temporalis muscles were studied. Thirty different osteometric measurements were also taken from skulls. Significant atrophy in BTX injected muscles was observed in groups 2 and 3. In group 4 (saline injection), only few osteometric measurements were significantly reduced, indicating the effect of the injection itself. Both groups 2 and 3 have apparent decrease in nasal bone, premaxilla, maxilla, and zygomatic dimensions on the injected side. When masseter group was compared with control and saline groups, no significant difference was found in skull base dimensions and mandibular length. In contrast, temporal group has also shown significant decrease in skull base dimensions. Our conclusions are as follows: (1) With this model, it is possible to study muscular action on bone formation and modeling without any surgical intervention, that is, by avoiding surgical artifacts, such as scar and contracture; (2) denervation of the skeletal muscles with BTX during the growing phase does effect bone development in a negative way; (3) pediatric use of the BTX deserves reevaluation under the light of these findings.

Thyroid eye disease presenting after cosmetic botulinum toxin injections

A 53-year-old woman with left periorbital swelling 4 days after botulinum toxin injection in the lateral canthal area presented after noticing left eye prominence. Physical examination demonstrated proptosis and eyelid retraction. Computed tomography of the orbits confirmed extraocular muscle enlargement consistent with thyroid eye disease. In this case, the patient had development of proptosis after receiving botulinum toxin injections. Although the proptosis may represent progression of the patients' thyroid eye disease, it is worthwhile to consider incitation by botulinum toxin as a possible cause given its widespread use.

Myotoxic effects of the skeletal muscle-specific immunotoxin, ricin-mAb35, on orbicularis oculi muscle after eyelid injections in rabbits

PURPOSE

The authors recently demonstrated that a single injection of the immunotoxin ricin-mAb35 has potent and long-lasting myotoxic effects in extraocular muscles. The myotoxicity of injected ricin-mAb35 was tested in the eyelids of rabbits to determine its potential for use in the treatment of benign essential blepharospasm and other dystonias.

METHODS

The immunotoxin ricin-mAb35 was injected in one eyelid of adult rabbits. After 1 week, 1 month, or 6 months, the rabbits were euthanized, and the eyelids were prepared for histologic examination of inflammatory cell infiltrate with immunohistochemical localization of cd11b and myosin heavy chain isoform expression. Muscle loss was quantified by analysis of muscle fiber cross-sectional area and total myofiber number.

RESULTS

Within the first week after a single injection of ricin-mAb35, some edema developed, which resolved by the second week. Otherwise, the eyelids were normal in appearance. A short-lived inflammatory response was seen at 1 week, but this resolved 1 month after treatment. One week after injection, there was a significant decrease in the total number of orbicularis oculi myofibers in the ricin-mAb35-treated eyelids. This myofiber loss remained significant 1 month later and was maintained 6 months after the initial injection.

CONCLUSIONS

Direct injection of the immunotoxin ricin-mAb35 resulted in significant, acute muscle loss in the orbicularis oculi of rabbits that was maintained for up to 6 months. Physiologic studies are needed to demonstrate concomitant loss of muscle strength, but these results suggest that ricin-mAb35 injection holds promise as a muscle-weakening agent in the eyelid.