Effects of thoraco-lumbar electric sensory stimulation on knee extensor spasticity of persons who survived cerebrovascular accident (CVA)

Spasticity is mostly due to an excess of impulses to alpha motor neurons pa rtly resulting from a change of interneuron activity. Low threshold afferen t has been reported to change the activity in interneuron. The purpose of t his study is to investigate the effects of surface spinal paravertebral sti mulation on knee extensor spasticity. Ten survivors of stroke, with knee ex tensor spasticity, received electric stimulation for five 45-minute periods through surface electrodes applied to the skin in the twelfth thoracic and first lumbar areas. The electric stimulations had an amplitude modulated a lternating current (AC), with a carrier frequency of 2500 Hz, modulated to "beats" frequency of 20 Hz. Stimulation amplitude was raised to elicit sens ory stimulation. The pre- and post-treatment evaluation included the modifi ed Ashworth scale, active torque during controlled knee movements at variou s velocities, and electromyographic (EMG) activity during the torque measur ements. Our results indicate that nine of ten subjects demonstrated a decre ase in the modified Ashworth scale posttreatment. The EMG activity of the s pastic quadriceps during active knee flexion was decreased post-treatment a s compared with the value before treatment. The active torque value of knee flexion or extension at 30 degrees, 60 degrees, or 90 degrees /sec of angu lar velocity did not change significantly post-treatment. A trend of increa sing spastic quadriceps EMG activity with respect to the angular velocity d uring an active knee flexion was established, with Ashworth scale considere d. The level of EMG activity is higher when the Ashworth scale is higher. A ccording to our results, the surface paravertebral sensory stimulation was effective in reducing quadriceps muscle spasticity of the subjects. Both th e modified Ashworth scale and the EMG activity of spastic quadriceps during eccentric contraction are suggested as sensitive tools for measuring spast icity of persons who survived cerebrovascular accident (CVA).