18.1 Introduction

Spasticity is described as velocity-dependent resistance to passive movement of a joint, due to hyper-excitability of the stretch reflex and loss of inhibition from ascending efferent pathways. It can be a compensatory tool for loss of motor function, and may be useful in certain instances. Thus, the presence of spasticity itself should not be a trigger for surgical intervention unless it is causing significant pain, functional loss, or significant decrease in quality of life. ¹

In patients with functional losses attributable to the patient’s spastic musculature, surgical approaches may be an effective adjunct to medical or physical therapy treatment modalities. The goal of intervention in these scenarios is to re-calibrate a balance between paretic and spastic muscles, providing relief from debilitation due to excess tone. ¹ Appropriate treatment should leave the patient with enough motility and tone to be useful during the activities of daily living. For patients with poor baseline functionality, surgery may also help to correct progressive orthopedic deformities and appearance. ²

Spasticity treatments range from minimally invasive to open surgical interventions. Options include botulinum toxin injection, selective peripheral neurotomy intrathecal baclofen, dorsal rhizotomy, and various orthopedic surgeries designed to correct deformities that result from increased tone. ³ In all cases, a multimodality and disciplinary approach should be adopted. ^{1 , 4}

18.2 Evaluation

There are two core components to spasticity, or muscle “stiffness” as patients often describe it. First, velocity-dependent or dynamic muscle shortening due to increased tone may manifest as hyperreflexia, clonus, and resistance to movement. Second, fixed muscle shortening can occur and cause contractures that persist even under anesthesia or nerve block. Contractures must be approached differently than the former category. From a surgical perspective, should medical management fail, orthopedic and neurosurgical procedures may need to be done in tandem to achieve success. ⁵

When evaluating the spastic patient for intervention, the first steps are to obtain a thorough history and do a physical exam. It is essential to take time for a period of observation, to assess the patient’s range of motion and degree of contracture at individual joints. Next is a qualitative clinical evaluation in which response to deep tendon reflex testing and resistance to passive stretch is measured. The response strength is not as important as whether there is symmetry to the responses. The patient’s position during the examination is important. Resistance may be more pronounced when the patient is upright or in a wheelchair. ¹ Also, spasticity changes after stress and muscle fatigue.

A number of manual and electrophysiological testing options are available to measure passive quantifiable motion. These efforts measure the gradual increase in resistance present during movement. That resistance may subside when limits to the motion are reached. The change is proportional to the velocity and position-dependent resistance. The measurement of spasms with electrophysiology may also be useful in planning. ^{1 , 6}

To best document clinical status and progression and compare pre and post-operative function, spasticity should be graded using the Ashworth scale (▶ Table 18.1). Numerous other outcomes measures have also been reported. Treatment can have a placebo effect and has been reported in up to 50% of patients, so an objective measurement tool is crucial.

Lastly, it is important to develop a good understanding of whether a patient’s spasticity is causing pain or discomfort and thus affecting their quality of life. These determinations will help in the choice of intervention.