Chronic Spasticity

Chronic spasticity is a velocity-dependent increase in muscle tone caused by injury to the descending motor pathways in the brain or spinal cord — the upper motor neuron (UMN) pathways.^[1] It occurs as part of the broader UMN syndrome, alongside weakness, hyperreflexia, an extensor plantar (Babinski) response, and slowed voluntary movement, and it commonly coexists with spastic dystonia (tonic muscle activity at rest) and co-contraction of opposing muscle groups. Spasticity is not uniformly harmful: in a plegic limb it can provide enough passive tone and posture to allow weight-bearing during transfers or standing, so reducing tone pharmacologically can sometimes unmask underlying weakness and worsen function rather than improve it. Because of this, spasticity is treated only when it interferes with function, care, or causes pain — never simply to normalize a tone score — and every treatment plan starts from a specific, agreed functional goal rather than a target Ashworth grade.^[1] Management is typically multidisciplinary, involving pharmacists, neurology, physiatry, physiotherapy, and orthotics.

Examination findings

On examination, spasticity presents as a velocity-dependent resistance to passive muscle stretch — resistance that increases the faster the limb is moved — distinguishing it from the constant, velocity-independent resistance of rigidity. It is usually accompanied by hyperreflexia, clonus, an extensor plantar response, and weakness in the affected limb(s), together forming the upper motor neuron syndrome. Spastic dystonia (involuntary tonic muscle activity at rest, without a stretch stimulus) and co-contraction of agonist and antagonist muscles may also be present and contribute to abnormal posturing.

• Any established upper motor neuron lesion or disease — spinal cord injury, multiple sclerosis, stroke, cerebral palsy, traumatic brain injury, or another structural spinal cord disease.
• New-onset spasticity without a previously diagnosed UMN condition is itself a signal of possible undiagnosed structural pathology, not a benign finding — see Assessment & Diagnosis.
• Immobility and prolonged static positioning, which both promote spasticity and increase the risk of secondary contracture.
• Any painful or noxious stimulus in a patient with an already-established UMN condition — pressure injury, urinary tract or other infection, bladder distension or urolithiasis, constipation, deep vein thrombosis, or an unrecognized fracture — can acutely worsen spasticity in an otherwise stable patient.

Investigations

No investigations are needed when spasticity is recognized as part of an already-diagnosed UMN condition, such as spinal cord injury, stroke, or multiple sclerosis. Spasticity occurring in isolation, without a known UMN diagnosis, needs investigation for the underlying cause — refer to neurology and obtain MRI of the brain and/or cervical and/or thoracic spine, guided by the specific pattern of signs and symptoms present.

Grading spasticity: the Modified Ashworth Scale

The Modified Ashworth Scale is a clinician-administered ordinal scale that grades resistance to passive stretch at a single joint; it is not a patient-completed questionnaire and does not produce a summed numeric score across multiple joints, so it is reported and tracked as a per-joint grade rather than a calculator-style total.

Other assessment tools

• Penn Spasm Frequency Scale — grades the frequency of spontaneous spasms, useful when spasms rather than resting tone are the main problem.
• Numeric Rating Scale for Spasticity (NRS-S) — a simple patient-reported 0-10 severity rating.
• Patient-Reported Impact of Spasticity Measure (PRISM) — a patient-reported measure of the functional impact of spasticity on daily activities.

• Improve functional movement and gait.
• Improve or preserve range of motion and limit contracture formation.
• Reduce pain and spasm frequency.
• Improve seating, positioning, and skin integrity — reduce pressure-related skin breakdown.
• Improve caregiving tasks, such as perineal care and catheterization.
• Define the specific functional goal in every patient before starting treatment — the target determines both the treatment chosen and how success is judged.

• Search for and treat aggravating factors whenever a previously stable patient's spasticity worsens — pressure areas, infection (urinary tract, ingrown toenail, and others), bladder stones or distension, constipation, and deep vein thrombosis are common triggers.
• Daily stretching and range-of-motion exercises are recommended for essentially every patient with chronic spasticity, alongside any pharmacologic treatment chosen.
• Active stretching and joint mobilization can increase joint range of motion, improve gait parameters, and reduce spasticity, particularly at the ankle.^[4]
• Positioning orthoses/splints may help treat spasticity at a specific joint (for example, wrist-flexor spasticity), but routine splinting alone is not recommended as a general spasticity treatment.^[4]
• Transcutaneous electrical nerve stimulation (TENS) is an increasingly used adjuvant physical therapy, typically applied for about 30 minutes daily to the affected nerve or muscle; benefit is greatest when combined with an exercise program and supervised initially by an experienced physiotherapist.
• Permanent selective neurotomy may be considered for refractory focal spasticity; other surgical procedures for spasticity itself are reserved for the most refractory cases.
• Orthopedic procedures (tendon lengthening, release, or transfer) do not treat the underlying spasticity but can optimize function and help prevent contracture in selected patients.

Breastfeeding

Baclofen is compatible with breastfeeding, with very low amounts detected in breast milk. Tizanidine is lipid-soluble and may pass into breast milk — use with caution. Gabapentin is present in breast milk, but maternal doses under 2.1 g/day are associated with low infant serum levels; use caution when combining with other sedating medications. Benzodiazepines transfer into breast milk in small amounts generally considered compatible with breastfeeding — monitor the infant for sedation if a benzodiazepine is required. Botulinum toxin does not pass into breast milk and may be used at standard doses while breastfeeding.

Pediatrics

Baclofen is not established as safe or effective under 12 years of age. Dantrolene oral capsules are approved for chronic spasticity in children 5 to 18 years old, with insufficient experience to recommend use under 5. Tizanidine has not been established as safe and effective under 18 years of age. Diazepam is contraindicated under 6 months of age; from 6 months onward, start at the lowest dose and titrate gradually. OnabotulinumtoxinA is approved for upper and/or lower limb spasticity in children 2 years of age and older and is considered a relatively safe option with few serious side effects in this population, making it a reasonable choice for pediatric focal spasticity, particularly in cerebral palsy.^[1]

Renal and hepatic impairment

Baclofen requires dose reduction in renal impairment; patients on hemodialysis typically need only about 5 mg/day. No baclofen dose adjustment is needed for hepatic impairment. Tizanidine needs lower individual titration doses in creatinine clearance under 25 mL/min or in hepatic impairment. Gabapentin requires renal dose reduction, with a supplemental dose after hemodialysis. Dantrolene's hepatotoxicity risk means it should be used with particular caution, and with close liver function monitoring, in any patient with pre-existing hepatic impairment.

Older adults

Baclofen and tizanidine are both cleared more slowly in older adults, who are also more susceptible to dose-related side effects — start at a lower dose and titrate more cautiously than in younger adults. Benzodiazepines carry an increased risk of cognitive impairment, delirium, falls, fractures, and motor vehicle accidents in older adults, and long-term use should be avoided where possible. Fatal hepatic adverse events with oral dantrolene have been reported more often in older adults — use the lowest effective dose with close liver function monitoring.

Record a clinician-administered (Modified Ashworth Scale, Penn Spasm Frequency Scale) or patient-reported (NRS-S, PRISM) spasticity outcome measure at baseline and again 10-14 days after every dose change, and judge benefit against the specific functional goal set at treatment initiation, not the score alone.^[1] Assess strength and function at every baclofen dose increase, particularly in ambulatory patients — spasticity-related bracing can be lost as tone falls, and a treatment that reduces tone can still worsen function if it unmasks underlying weakness. Obtain baseline and periodic liver function tests for tizanidine and dantrolene. Monitor renal function where relevant (baclofen, gabapentin) and adjust dose accordingly as it changes. For a previously stable patient whose spasticity suddenly worsens, look for an aggravating trigger — infection, pressure injury, a bladder or bowel problem, or other noxious stimulus — before assuming disease progression or treatment failure.^[4] Patients with an intrathecal baclofen pump need scheduled refill visits tracked closely, since a missed refill is a preventable cause of the withdrawal emergency described in Red Flags & Refer.

1. Confirm the titration schedule was actually followed and that a maximally tolerated dose was reached before concluding an agent has failed.
2. Before escalating treatment, screen for an aggravating or triggering factor — infection, pressure injury, a bladder or bowel problem, or other noxious stimulus — causing acute-on-chronic worsening rather than true treatment failure.
3. If an agent is not tolerated, switch to an alternative with a different mechanism (for example, baclofen to tizanidine, or the reverse).
4. If there is a partial response but more tone reduction is needed, add a second oral agent acting at a different site rather than pushing a single agent past its tolerated dose — baclofen plus tizanidine is a standard combination.
5. If oral therapy at maximally tolerated doses over 1-3 months still gives an inadequate functional benefit, taper and discontinue rather than continuing indefinitely on faith.
6. For spasticity that is predominantly focal, or of cerebral origin (stroke, traumatic brain injury) and poorly responsive to oral therapy, refer for focal chemodenervation rather than continuing to escalate oral agents.
7. For severe generalized spasticity refractory to optimized oral combination therapy, or with intolerable oral side effects, refer for intrathecal baclofen pump evaluation.

• Treating a tone score numerically without a defined functional goal — over-treatment can worsen function by unmasking weakness in a patient who was using spasticity for standing or transfers.
• Stopping oral or intrathecal baclofen abruptly — always taper; abrupt discontinuation risks a life-threatening withdrawal syndrome.
• Attributing sudden worsening of spasticity to disease progression without first ruling out an aggravating trigger such as infection, pressure injury, or a bladder or bowel problem.
• Defaulting to dantrolene as a routine first-line choice despite its real hepatotoxicity risk and comparatively weak efficacy evidence — reserve it rather than reaching for it first.
• Presenting gabapentin or nabilone as approved spasticity treatments rather than off-label options — counsel patients accordingly.
• Assuming botulinum toxin type A products are interchangeable unit-for-unit across brands, or confusing a cosmetic-only formulation (marketed for facial lines) with the corresponding therapeutic product used for spasticity — dosing is brand- and indication-specific.
• Delaying referral for focal or cerebral-origin spasticity, both of which are less likely to respond adequately to oral agents alone.
• Not tracking a validated spasticity outcome measure before and after each dose change, making it impossible to judge whether a change in therapy actually helped.

How to use this table: Doses are adult doses unless a pediatric line is shown, and require patient-specific confirmation, including renal/hepatic adjustment. Select any drug name to open its complete Pharmasist Drug Database page.

GABA-B receptor agonist

Standard first-line agent for generalized spasticity.

Alpha2-adrenergic agonist

Benzodiazepines

Most useful when spasms are problematic specifically at night; daytime sedation limits routine use.

Direct-acting skeletal muscle relaxant

Other oral adjuncts (off-label for spasticity)

Cannabinoid buccal spray

Botulinum toxin (focal spasticity)

Specialist-administered; requires referral to an experienced injector. Botulinum toxin type A products are not interchangeable unit-for-unit across brands — each has its own dosing.

Evidence note: Botulinum toxin dosing, adverse effects, and comments reflect standard Canadian specialist practice, cross-checked against current consensus and stroke-rehabilitation guidance.^[1][4][5]

Intrathecal baclofen

Delivered by a programmable pump, usually implanted in the anterior abdominal wall, as a continuous or bolus infusion directly into the spinal fluid. Because the drug acts locally at the spinal cord, systemic and cognitive side effects are minimal compared with oral dosing, and the effect on spasticity can be profound — though it is generally more effective for lower-limb than upper-limb tone because of the lumbar-to-cervical concentration gradient. There is no standard oral-to-intrathecal dose conversion; intrathecal dosing is individualized by specialist titration, usually starting with a screening bolus trial before permanent pump implantation.^[2] Abrupt interruption of intrathecal delivery — from a missed refill, pump malfunction, or catheter problem — causes the same life-threatening withdrawal syndrome as abrupt oral discontinuation and is a medical emergency (see Red Flags & Refer).^[3]

Other focal procedures

Phenol-alcohol nerve or motor-point blocks are an alternative focal chemodenervation technique to botulinum toxin, injected around the nerve supplying a specific spastic muscle group and typically repeated around every 6 months as needed; injections can be uncomfortable and carry a risk of dysesthesia and infection. This is a specialist-administered procedure using a compounded chemical rather than a distinct retail drug product, and is not listed in the Drug Database.