Measurement of the effect of a bolus dose of intrathecal baclofen by continuous measurement of force under fibreglass casts.

Abstract

Continuous intrathecal administration of baclofen with implanted programmable pump systems is recommended in the treatment of severe spasticity of cerebral origin. Prior to pump implantation, a baclofen bolus test (BBT) is used to assess the effectiveness of intrathecal baclofen using the modified Ashworth Scale (MAS) and Penn Spasm Frequency Scales (SFS). The result of a BBT may be difficult to interpret in patients with reduced joint mobility caused by contractures. The aim of this study was to apply a new spasticity measurement which would quantify and visualise the effect of a BBT in 10 patients with severe cerebral spasticity and contractures. Spasticity was recorded continuously by the measurement of force under circular fibreglass casts in 10 knee joint contractures. Force was recorded as net-torque by multiplying the force and distance between sensor and joint axis, thus allowing inter-individual comparison. MAS, SFS, and two three-hour time integrals of net-torque were determined before and after intrathecally administered baclofen. No significant changes in MAS (p = 0.1) and SFS (p = 0.07) were observed; however, a significant reduction of time integrals of net-torque after baclofen administration (p = 0.005) was found. The present study shows that the antispastic effect of intrathecally administered BBT can be quantitatively assessed and visualised using the described method. It also suggests that this method can be helpful in the assessment of the effectiveness of the BBT in patients with severe spasticity of cerebral origin and contractures.