Chapter 19: Intervention Related to Hypertonia: Spastic and Rigid

Chapter Objectives

Upon completion of this chapter, the learner should be able to:

1. Discuss the development of spasticity and rigidity.

2. Discuss the possible impact of spasticity and/or rigidity on function.

3. Identify neuromuscular diagnoses which commonly have hypertonia as a related impairment.

4. Describe the implications of surgical and pharmacological interventions for spasticity.

5. Demonstrate interventions to influence spasticity or rigidity.

Introduction

Spasticity and rigidity are the two types of hypertonia detected in individuals with neurological disorders. Hypertonia, also called hypertonus, is any increase in muscle tone (i.e., an increase in resting muscle resistance while the resting muscle is passively elongated). Among the adult population, consensus regarding accurate definitions of the different types of hypertonia has not been reached.

In 2003, several researchers gathered to create operational definitions of different types of hypertonia in children: “Spasticity, or spastic hypertonia, is defined as hypertonia in which one or both of the following signs are present: (1) resistance to externally imposed movement increases with increasing speed of stretch (i.e., velocity-dependent; Lance, 1980) and varies with the direction of movement and/or (2) resistance to externally imposed movement rises rapidly above a threshold speed or joint angle (Fig. 19-1A). Dystonia is defined as a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both. Rigidity, or rigid hypertonia, is defined as hypertonia in which all the following are true: (1) the resistance to externally imposed joint movement is present at very low and high speeds of movement, does not depend on imposed speed or angle threshold, and is usually detected throughout the available range, not just at the end ranges of movement; (2) simultaneous cocontraction of agonists and antagonists may occur, and this is reflected in an immediate resistance to a reversal of the direction of movement about a joint; (3) the limb does not tend to return toward a particular fixed posture or extreme joint angle; and (4) voluntary activity in distant muscle groups does not lead to involuntary movements about the rigid joints, although rigidity may worsen” (Sanger, 2003). In addition to the previous definition, spasticity also tends to be greater at the end of range when the muscle is on greatest stretch. Decerebrate and decorticate rigidity, defined later in this chapter and illustrated in Figure 6-15AB, could be considered the most extreme forms of spasticity as the increased tone is predominant on one side of the joint and the limbs do tend to return toward a particular fixed posture due to the imbalanced resting muscle tone. Cogwheel rigidity (Fig. 19-1B) describes the motion of a limb that catches and releases as the limb is moved passively through the available range of motion. It is commonly seen in patients with Parkinson disease.