What is spasticity?

The term “spasticity” is derived from the Greek word “spasmos” (Greek: “spasm”). Spasticity is defined by increased muscle tone resulting from the nervous system’s malfunction in controlling the affected muscles. All muscles in the human body that can be moved voluntarily (voluntary motor function) are controlled by motor neurons located in the spinal cord (second motor neuron).

It is crucial that the motor neurons in the spinal cord are under the control of neurons located in the brain that are connected to the spinal cord via nerve pathways (first motor neuron). If the first motor neuron is damaged, this control function is lost, resulting in uncontrolled, excessive, and spasmodic movements known as spasticity. In simple terms, the second motor neuron (the connection between the spinal cord and the muscles) is responsible for generating force, while the first motor neuron (the connection between the brain and the spinal cord) is responsible for coordinating and controlling motor function. Spasticity is a symptom of impaired muscle control caused by damage to the first motor neuron.