Over the past decade, botulinum toxins (BT) have been extensively used to treat any number of diverse disorders, including functionally significant, focal spasticity in the arm and leg of persons with injury/disease of the central nervous system. Spasticity is an involuntary muscle stiffness that limits movement of an extremity and often leads to pain, hygiene problems, difficulty in bed or wheelchair positioning, and functional deficits in self-care and mobility.
There are three BT products on the market: MyoBloc®, Botox®, and Dysport®. FDA approval for use of Botox® in spasticity is anticipated sometime during 2010. In the Weill Cornell Division of Rehabilitation Medicine alone, nearly 50,000 units of Botox® were injected for the treatment of spasticity during the 2008-2009 academic year. (Note: The vast majority of the BT market share in the US rests with Botox®.)
There is excellent evidence supporting the effectiveness of BT in decreasing tone and modest clinical evidence supporting functional improvement. Despite the frequent use, however, there is astonishingly little evidence delineating the impact on diffusion of dosing, dilution, approach to muscle localization, or serotype of BT. To better study these relationships we will be using advanced imaging to develop a model to characterize the physical characteristics of BT diffusion in human skeletal muscle.
