INTRODUCTION- SEROTYPES AND MECHANISM OF ACTION

Botulinum Toxin happens to be one of the most potent neurotoxins comprising of a 50 kDa light chain and a 100kDa heavy chain, which are linked by a disulphide bond. 7 serotypes ranging from A to G have been identified. Botulinum toxin (BoNT) is one of the most potent neurotoxins and consists of a 50 kDa light chain and a 100 kDa heavy chain linked with a disulfide bond. It exists in seven serotypes, A through G. It has been seen the Botulinum Toxin is responsible for interference with the expression of various neuropeptides such as Substance P and calcitonin gene- related protein (CGRP), which are key mediators of neurogenic inflammation. Botulinum toxin A(BoNT/A) injections have been seen to reduce paw edema in formalin treated rat cadavers, lower the tissue glutamate release and obtund spinal cord excitability. In all, it has been recognised that Botulinum is an inhibitor of cytokines, neuropeptides and other inflammatory mediators. Lot of clinical studies support the proposed anti- nociceptive mechanism of action o0f Botulinum Toxin.

APPLICATIONS

The neuromuscular blockade brought about by BOTOX has been seen to give good relief of pain and improvement of function in patients souring with painful and chronic musculoskeletal ailments.

Osteoarthritis

BOTOX is being increasingly used in the non invasive management of arthritis of the knee, hip, shoulder and other joints as well. Significant improvement in pain scores and quality of life was seen in a lot of patients. Moore and colleagues saw marked improvement in patients of knee arthritis, injected with BOTOX.

Plantar Fascitis

One of the commonest foot and ankle condition encountered in the society, BoNT injections are helpful in resistant cases (failure of physical therapy and steroid injections). Significant improvement of pain and the near absence of side e¬ects has made it popular amongst the Musculoskeletal practitioners today.

Temperomandibular Joint Pain

Pain over the temperomandibular region which is secondary to overactivity of the masticatory muscles responds well to intramuscular BOTOX injections. Injections are usually given via an oral route. Studies have shown that the usual preferred dose is 50 units into the masseter and 25 units injected into the temporalis. Studies have reported upto 80% of patients experiencing lasting pain relief upto 10-12 months.

Tennis Elbow/ Lateral Epicondylitis

Probably the most common cause of tennis elbow, studies have reported reduced pain and improvement in daily activities after BoNT-A injection. Care has to be taken to monitor the dosage as reductions in finger movement and grip strength have occurred due to the motor e¬ects of BoNT-A, although the motor block is only temporary in nature.

Chronic Exertional Compartment Syndrome

A condition resulting in compression symptoms due to increased pressure in an osteofascial muscle compartment, usually after exercise. Based on limited evidence, BoNT-A injections may be a safe and effective treatment, in some cases avoiding the need for surgery.

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References

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