Pain, Spasticity, and Assistive Technology: Treat the Goal, Not the Number
Measure spasticity, treat the goal
Spasticity is velocity-dependent hyperreflexia from loss of descending inhibition; rigidity is velocity-independent. The Modified Ashworth Scale grades resistance at a single speed (0 to 4) and does not capture function, whereas the Tardieu scale assesses the angle of catch at slow and fast velocities and better reflects dynamic spasticity. Treat only when tone impairs function, hygiene, or comfort - not to normalize the number. The ladder: remove noxious triggers (infection, constipation, ingrown toenail), then therapy, positioning, and oral agents (baclofen, tizanidine, dantrolene), then focal chemodenervation with botulinum toxin or phenol, then intrathecal baclofen or surgery. Botulinum toxin weakens injected muscles, is dosed by muscle mass, and peaks at 2–6 weeks. Intrathecal baclofen withdrawal is an emergency with rigidity, fever, and autonomic instability.
Pain questions require separating nociceptive from neuropathic pain; neuropathic pain responds to gabapentinoids, tricyclics, and SNRIs. Complex regional pain syndrome uses the Budapest criteria - disproportionate pain, autonomic and trophic changes, and no better explanation. Phantom limb pain is real and treatable, and preemptive analgesia is unproven.
Assistive technology: match the device to the goal. AFOs control foot drop and plantarflexion; KAFOs address knee instability; wheelchair prescription considers seat width, pressure mapping, and tilt-in-space for pressure relief. Prosthetic K-levels (K0–K4) describe ambulation potential and drive component choice.
Worked example
A patient on intrathecal baclofen presents with fever, rigidity, and labile blood pressure after a pump alarm: treat as withdrawal, give oral baclofen, and contact the pump team urgently.
Rule of thumb
Treat tone only when it causes a problem, and always hunt the noxious trigger before escalating medication.