Flaccidity is an example of a point in the poststroke arc of recovery with consequences as bad, or worse, than spasticity. Spasticity carries with it the potential for contracture, pressure sores, pain, joint problems and deformities. Flaccidity, too, carries obvious physical risks (i.e., subluxation, muscle atrophy, etc.). But flaccidity also provides an ominous window onto the prognosis of the limb. Flaccidity says 2 things: “Recovery will have to wait” and/or “Recovery may have ended”.
There are two kinds of paralysis; flaccid paralysis and spastic paralysis. Most of the patients therapists see fall into neither category. Part of the reason that therapists typically don't see truly paralyzed patients is because, traditionally at least, little can be done to help. With the advent and broadening use of intrathecal baclofen, injectable neurolytics and the dorsal root rhizotomy, etc., the potential for treatment has broadened. Still, most of the people that are candidates for treatments that aim to improve limb movement are not going to be hemiplegic (paralyzed) -- they'll be hemiparetic (weak). The question becomes, is there more potential and somebody who has near flaccid or spastic?
We can look to pioneering physical therapist Signe Brunnström for insight. Brunnström’s six stages (Thanks “Pink House On The Corner” blog!) of recovery provide the ultimate template for recovery from stroke. Stage I is flaccid (although reflexes are available), stage II is harkened by the emergence of spasticity and synergies, and in stage III synergies and spasticity are at their zenith. So the progression is clear; flaccidity to spasticity. And as with much of Brunnström’s work there is an underlying wisdom; spasticity, as disdained and dangerous as it is, is preferable to flaccidity. This is especially true early after stroke. A patient with emergent spasticity can work in a repetitive and demanding fashion very early in the arc of recovery. And when it comes to stroke recovery, early is better. This is as true in rat models as it is in clinical trials involving human participants. But if somebody's flaccid, how you begin rehab? Although most patients do not remain flaccid, the delay that flaccidity creates provides a much more shallow recovery trajectory.
Spasticity may have another advantage over flaccidity with regard to issues outside of the progression towards recovery. Often the flaccid limb, whose dearth of sensation usually parallels its dearth of movement, is at risk of injury. Bluntly, the world can be a dangerous place to a flaccid limb. Like a weakling in a neighborhood of bullies, the flaccid limb is surrounded by walls, corners, countertops and other unforgiving surfaces. In the lower extremity is usually less of an issue because the flaccid limb can be controlled within the confines of a wheelchair. In the upper extremity the limb is often put in a trough and/or sling to protect the limb. These forms of stabilizing the upper extremity protect the limb in two ways; keeping the arm from flailing with the potential for injury; protecting the shoulder from subluxation.
Spasticity manages to protect the limb from these “bullies.” In the upper extremity the spastic posture brings the arm across the body, internally rotated and flexed at the elbow wrist and fingers. This posture is dictated by the overwhelming strength of the flexors and internal rotators. For an unprotected arm spasticity can be seen as a good thing, simply because it keeps the limb out of trouble.
Beyond providing an immature protection mechanism, spasticity may do other beneficial things as well. Spasticity may induce Wolf’s law, which states that bone will remodel through osteoblastic activity dependent on the loads it’s placed under. That is, the pull of muscle on bone is what keeps bones from becoming osteoporotic. This is particularly important issue because stroke survivors tend to fall towards the affected side. Because there is less bone strength on that side there is a higher chance of fracture. Spasticity may also improve circulation because of the activity in the triceps surae (gastroc, soleus). The primary way blood is delivered from the extremities back to the heart and lungs is the muscle contraction. With regard to the circulatory system spasticity is preferential to flaccidity, because the blood gets shunted towards the heart and lungs. Spasticity also maintains muscle bulk because, as pathologic as it is, at least the muscle is contracting.
Most importantly, spasticity provides a crude template for future recovery. But despite its advantage over flaccidity, all is not rosy with regard to spasticity. As the first line of defense, therapists are tasked with interrupting the march towards contracture. Tools in neurology and physiatry are helping with that task. Serial casting and a dedicated stretching program are also essential tools. The bottom line is, as much as spasticity is a welcome visitor it is best when it is exactly the: a visitor. Spasticity allows for at least the chance of its visit being shortened by allowing for movement in some planes and pivots. Take what spasticity give as you usher it out the door.