Treatment of spasticity with botulinum toxin

Spasticity is a complex disorder characterized by a velocity-dependent increase in muscle tone associated with exaggerated deep tendon reflexes. It can be caused by numerous diffuse or focal cerebral and spinal pathologic conditions. Spasticity indicates upper motor neuron dysfunction and if severe, can lead to considerable motion restriction and eventually to more serious disability. The therapeutic interventions available to treat spasticity are often of limited benefit. In the last decade, many open-label and several double-blind, placebo-controlled, studies have demonstrated the effectiveness of intramuscular botulinum toxin (BTX) injections for the management of spasticity caused by multiple sclerosis, brain / spinal cord injury, cerebral palsy, and stroke. BTX can also be beneficial in the treatment of spasticity, or a mixture of spasticity and rigidity, in many neurodegenerative conditions; including Parkinson disease, progressive supranuclear palsy, corticobasal degeneration, frontotemporal dementia and parkinsonism linked to chromosome 17, and in various sporadic and familial spinocerebellar ataxia syndromes. Currently, two BTX serotypes, which are serologically different but share a common subunit structure, are commercially available: type A (Botox(R), manufactured by Allergan, Inc, Irvine, California, USA; and Dysport(R), distributed by Beaufour-Ipsen Pharmaceuticals, Paris, France); and type B (manufactured by Elan Corporation, Dublin, Ireland, and available in the United States as MyoBloc(R) and in Europe as NeuroBloc(R)). BTX primarily affects the neuromuscular junction by inhibiting acetylcholine release. Dosages vary considerably depending on the particular preparation used, the muscle injected, the severity of the condition, and the duration of treatment.