What Is Spasticity?
Spasticity is a type of abnormal, high muscle tone that is velocity-dependent. High muscle tone essentially means that there is significant tension and tightness in the muscle that makes it challenging to lengthen and stretch. Velocity-dependent means that this tension and tightness is worse with quick movements versus only being present with slow stretching.
Change in muscle tone often occurs after a stroke or traumatic brain injury.
Why Does It Happen?
To understand why spasticity and abnormal muscle tone happen, we have to understand some of the structures and functions of our nervous system.
The Rubber Band & The Spindle
Picture a rubber band. It’s elastic and can lengthen and shorten. Now imagine that rubber band being stretched to its breaking point. What happens?
It either snaps back to its shortened form or it breaks.
We have different types of sensors in our muscles that provide our brain with information about the status of the muscles. These sensors let our brain know that we’re right-side-up (proprioception) and act as a security system to make sure the muscles aren’t being damaged.
The specific sensor that plays a role in spasticity is the muscle spindle. These detect changes in muscle stretch and length. The muscle spindles cause our muscles to contract if they sense the muscles are stretching too far. It’s a protective mechanism called the stretch reflex.
In the rubber band example, the muscle spindle would tell the band to snap back to its shortened form in order not to break.
Because the stretch reflex needs to happen almost instantaneously to avoid muscle damage, the signal doesn’t travel all the way to the brain. Instead, it travels to the spinal cord and back to the muscle.
Spasticity results from two different issues after a stroke or traumatic brain injury.
- Muscle spindles become hyperexcited and cause the stretch reflex to be abnormally triggered. This results in abnormal muscle contractions leading to increased muscle tone and spasticity.
- The injured area of the brain is unable to successfully communicate with the spinal cord and peripheral nervous system. It becomes unable to inhibit these hyperexcited muscle spindles at the spinal cord level, which is what it would normally do. So instead of the brain telling the muscle spindles to calm down, they stay hyperexcited and continue telling the muscle to contract.
The Soap Dispenser Analogy
Have you ever been in a public bathroom and noticed that one of the automatic soap dispensers has gone haywire? Instead of doing its normal job (hand underneath, squirt of soap), it’s unloading a mountain of soap on the counter or floor.
The computer in the soap dispenser has messed up. It’s no longer telling the dispenser to start and stop when there’s a hand underneath. Instead, the sensor says, “I think there’s a hand under here all the time!” And then it releases all the soap.
When spasticity and high muscle tone occur, it’s because of those two underlying issues: hyperexcited muscle spindles and lack of inhibition from the brain.
In this analogy, think of the sensor as the hyperexcitable muscle spindles. The sensor thinks there is a hand present all the time so it continues to dispense soap. The spindles are so excited they think that the muscles are being stretched too far all of the time, so they shout to the spinal cord to turn on the stretch reflex.
Think of the brain as the computer in the automatic soap dispenser. The computer is unable to communicate effectively with the sensor to say, “Stop dispensing the soap! There’s no hand under there!” In the same way, the brain is unable to quiet the hyperexcited muscle spindles, so the stretch reflex continues to be activated which leads to continual contraction of the muscle.
The Stages of Recovery
A physical therapist, Signes Brunnstrom, developed the Brunnstrom Approach back in the 1960s to help medical professionals and survivors better understand muscle tone changes and recovery after a stroke.
Typically, we’d see someone move through these stages until they reached normal muscle tone and movement, but often survivors get stuck in one of these stages.
Stage 1: Flaccidity
This stage happens right after a brain injury. There’s usually no voluntary movement and recovering limbs may be limp. The brain cannot communicate with the muscles due to brain injury and nerve damage.
The goal is to protect the limb in this stage. Use positioning strategies to protect joints and avoid subluxation at rest or with activity. Remember, it’s never too early to start using mental practice techniques.
Stage 2: Spasticity Develops
A small amount of spasticity and basic limb synergies develop. Limb synergies mean that there are multiple unwanted muscle movements at once. The brain isn’t able to get the correct signals to muscles. Muscles begin to move but it’s usually involuntary. This is when you might see elbows, wrists, and fingers bend without trying.
Even though there is little motor control, keep trying to move your recovering limb as much as possible. It’s common to develop learned non-use (where you don’t use your recovering limb because of limited movement). Avoid this in preparation for future recovery. Self-stretch or have someone help you stretch daily to maintain muscle length.
Stage 3: Increased Spasticity
Damage to neural pathways from the brain to muscles causes the muscles to contract too often, as I explained earlier. This leads to tight, stiff, and sometimes painful muscles resulting in limited movement.
You can use splints to prevent contractures, which is a shortening and hardening of muscles or tendons. Continue to self-stretch or have someone help you stretch your recovering limb every day. Talk to your doctor about medications, Botox injections, or acupuncture that may help relieve stiffness and pain. Try to limit stress, as it can increase spasticity.
Stage 4: Decreased Spasticity
Spasticity finally begins to reduce in this stage. Some voluntary movement returns with improved control.
Capitalize on this stage. You can use functional e-stim, just make sure to get approval and instruction from a medical professional first. Move your recovering limb as much as possible with either assisted (someone helps) or active (just you moving) range of motion. Incorporate your recovering limb as much as you can in daily activities.
Stage 5: Minimal Spasticity
In this stage, brain signals to recovering limbs improve. You can start to perform more complex movements voluntarily.
Start moving towards active range of motion and strengthening exercises. Focus on controlled movements. Continue to use your recovering arm as much as possible in everyday activities. Repetition and consistency are key!
Stage 6: No Spasticity & Return of Coordination
Spasticity completely resolves. Motor control is almost fully restored in this stage except for some lingering coordination issues.
Continue to focus on active range and strengthening but include exercises or activities focused on fine motor and dexterity skills. This is where you hone in on more deliberate movements.
Stage 7: Typical Movement
Spasticity is not present. The brain and muscles are communicating effectively. Typical movement returns.
Keep actively moving and strengthening your whole body.
It’s important to understand that there are no specific timelines for moving through these stages. Every survivor’s experience is different, but improving your understanding of what stage you’re in can help you to advocate for appropriate treatment.