Spasticity

After damage to the brain or spinal cord, muscles can remain involuntarily contracted — tone increases and the muscle resists being stretched. Normal movement depends on muscles contracting and relaxing in turn; in spasticity the relaxation does not happen properly, so movement becomes stiff, effortful and sometimes impossible.

Left unmanaged it leads to permanent joint restriction, deformity, pain and loss of independence in daily activities.

Spasticity follows central nervous system damage: stroke, traumatic brain injury, spinal cord injury, multiple sclerosis and cerebral palsy. The level and pattern depend on the site and severity of the damage.

It is graded with the Modified Ashworth Scale, which scores resistance to passive movement. Because grading depends on the examiner and on the speed of movement, serial measurements should be taken by the same assessor wherever possible.

Some patients stand and walk on spastic tone, and reducing it removes the stiffness they were relying on. This is the reason we never report a tone measurement without a function measurement beside it — so a fall in tone that costs walking is visible rather than presented as progress.

The aim is controlled, pain-free, usable movement. Sometimes that means reducing tone; sometimes it means working around it.

Positioning and stretching as part of daily care, although in trials lasting up to seven months stretching alone made no clinically important difference to joint range 3. Guided and robotic movement to keep joints moving through their full arc. Splinting where indicated. Manual therapy. Gait and functional training so that any gain in range is converted into something the person can do.

Where tone is focal and blocking a specific function, injection therapy is considered as part of a plan rather than as a treatment on its own — the injection creates a window, and the therapy has to use it.

Tone is scored with the Modified Ashworth Scale, but the score alone decides nothing. What matters is what the tightness prevents: washing a hand, clearing the floor when walking, sitting comfortably, sleeping without pain.

Both are recorded before treatment and after, because a tone score that improves while nothing functional changes is not a result worth repeating.

Spasticity that is left long enough stops being a neurological problem and becomes a mechanical one: the muscle shortens permanently and no injection will lengthen it.

That transition is why the window for tone management is not open indefinitely. Stretching alone does not prevent it: in trials of stretch lasting up to seven months, high-quality evidence showed no clinically important effect on joint mobility 3.

It depends on the goal. A meta-analysis of 40 randomised trials with 2,718 people after stroke found robust evidence that botulinum toxin reduces resistance to passive movement and improves self-care of the affected hand and arm 4. It also reduced spasticity-related pain and involuntary movements, and improved passive range of motion 4.

What it did not do was improve active use: there was robust evidence of no effect on the arm and hand's capacity for tasks at follow-up 4. That is why the injection is planned around a specific goal, and why a goal of better active use is pursued through training rather than expected from the injection itself.