Managing Spasticity in PLS

Spasticity is the defining symptom of Primary Lateral Sclerosis. It shapes nearly every aspect of daily life — how you walk, how tired you feel, how your muscles respond to movement. Managing it well is not just about comfort; it is one of the most important things you and your care team can work on together.

What spasticity is

Spasticity is a velocity-dependent increase in muscle tone caused by damage to upper motor neurons (UMNs) — the nerve cells that run from the motor cortex down the spinal cord. When those neurons are damaged, the spinal cord's natural braking system loses some of its control, and muscles stay in a state of heightened excitability. The faster you try to move a limb, the more it resists. This is what makes walking feel effortful and stiff rather than weak in the way ALS feels — you are fighting your own muscles.

In PLS, UMN damage is diffuse and bilateral, affecting the legs most prominently but also the arms, trunk, and bulbar muscles (jaw, tongue, throat) in many patients. The result is a pattern of stiffness, scissoring gait, muscle spasms, and sometimes painful cramps that can occur at any time but are often worse at night or after exertion.

What it feels like day to day

People with PLS describe spasticity in different ways depending on how severe it is and which muscles are most affected. Common experiences include:

• Legs that feel like they are made of wood first thing in the morning, requiring time and movement to loosen up
• Sudden muscle spasms — sometimes painful, sometimes just startling — particularly at night when the nervous system is less actively suppressing them
• A feeling of being pulled forward or to one side when walking, requiring conscious effort to maintain balance
• Feet that do not clear the floor properly, creating a tripping hazard on uneven surfaces
• Arms that resist movement during fine motor tasks, making handwriting, typing, and buttoning clothes slow and exhausting
• Fatigue that comes not from muscle weakness but from the constant extra effort of moving against your own tone

Cold temperatures typically worsen spasticity. Many people notice that warm showers, heated blankets, or warm pools bring temporary relief — a useful piece of practical knowledge that influences how to structure your day.

Oral medications

There is no medication that cures spasticity or reverses it. What medications can do is reduce the level of muscle tone enough to improve function, reduce spasm frequency, and make physical therapy more effective. All of the oral options involve trade-offs between spasticity reduction and side effects.

Baclofen

Baclofen is the most widely prescribed antispasticity medication and the first-line choice for most PLS patients. It works as a GABA-B receptor agonist — essentially mimicking an inhibitory neurotransmitter to quiet the overactive spinal pathways driving spasticity. In clinical use, it is genuinely effective for many people, but the dosing range matters enormously.

The main limitation of oral baclofen is weakness. A randomized crossover trial comparing baclofen and tizanidine in spasticity patients found that baclofen was judged superior by clinicians on overall efficacy, but caused significantly more muscle weakness than tizanidine. In PLS — where the problem is already stiffness rather than weakness — adding drug-induced weakness creates its own functional problems. The practical goal is finding the dose that softens tone without making it harder to move.

Baclofen is started low (typically 5 mg two or three times daily) and titrated slowly upward over weeks. The sedative effect, particularly at higher doses, can be significant. Abrupt discontinuation is dangerous and must be avoided — it can cause seizures, hallucinations, and severe rebound spasticity.

Tizanidine

Tizanidine is an alpha-2 adrenergic agonist that reduces spasticity through a different mechanism than baclofen. The same crossover trial found comparable overall patient-rated effectiveness between the two drugs. Tizanidine causes less muscle weakness than baclofen — making it a useful alternative or addition when baclofen's weakness side effect is limiting function.

The trade-off is a different side-effect profile: tizanidine more commonly causes somnolence and dry mouth, and it requires monitoring of liver enzymes (liver enzyme elevation occurs in a small percentage of patients and usually resolves with dose reduction). Tizanidine is shorter-acting than baclofen, which can be used to advantage — dosing it around specific activities (before physical therapy, for example) while avoiding daytime sedation.

Clonazepam

Clonazepam is a benzodiazepine that is particularly useful for nocturnal muscle spasms — the involuntary jerking that disrupts sleep. It is not typically used as a primary daytime antispasticity agent because of its sedating effects, but a low dose at bedtime can meaningfully reduce night spasms and improve sleep quality. As with all benzodiazepines, tolerance develops over time and it should be used thoughtfully.

Dantrolene

Dantrolene acts directly on muscle rather than on the nervous system, reducing the calcium release that triggers muscle contraction. This peripheral mechanism means it can reduce spasticity without the same level of CNS sedation as baclofen or tizanidine. However, it also reduces the force of voluntary muscle contraction — causing weakness — and requires regular liver function monitoring due to hepatotoxicity risk. It is less commonly used in PLS than baclofen or tizanidine, but it is a useful option for patients who cannot tolerate centrally acting agents.

Intrathecal baclofen pump

For people whose spasticity is not adequately controlled with oral medications — or whose side effects from oral medications are limiting — an intrathecal baclofen (ITB) pump is a significant step up in treatment intensity. The pump delivers baclofen directly into the cerebrospinal fluid, bypassing the blood-brain barrier. This achieves effective concentrations at the spinal cord level at doses 100 to 1000 times lower than oral administration, dramatically reducing systemic side effects.

Before pump implantation, patients undergo a screening trial: a test bolus of intrathecal baclofen (typically 25–100 mcg) is injected to confirm that spasticity responds and that the patient tolerates the medication delivered this way. Only patients with a positive trial response proceed to implantation.

The pump itself is surgically implanted under the abdominal skin, connected by a catheter to the intrathecal space. It requires refilling every 1 to 6 months (depending on dose) and regular programming clinic visits to adjust dosing. Maintenance dosing is typically 300–800 mcg per day, titrated individually. A 2016 compliance-based study found that patients with consistent ITB use showed significantly better spasticity reduction than those with inconsistent use.

Complications to be aware of include catheter malfunction, pump failure, and infection. The most serious risk is baclofen withdrawal — if the pump fails or the catheter is dislodged without detection, abrupt loss of intrathecal baclofen can cause hyperthermia, dramatically increased spasticity, rhabdomyolysis, and multi-organ failure. Patients and caregivers need to know the warning signs and have a plan. This is an important consideration before committing to pump implantation.

Botulinum toxin injections

Botulinum toxin (Botox) injections produce localized, temporary muscle relaxation by blocking acetylcholine release at the neuromuscular junction. This is not a systemic treatment — it targets specific overactive muscles and lasts approximately three to four months before repeat injection is needed.

In PLS, botulinum toxin is useful for focal spasticity problems that are not well addressed by oral medications: a hand that will not open, an equinus foot (foot that is pulled into a plantar-flexed position causing toewalking), an overactive jaw muscle causing difficulty with chewing, or jaw clenching at night. A 2022 European expert consensus on spasticity management supports combined use of ITB and botulinum toxin for people with both widespread and focal spasticity patterns.

Physical therapy and stretching

Physical therapy is not optional in PLS spasticity management — it is central to it, in a way that no medication fully replaces. Spastic muscles that are not regularly stretched shorten over time, eventually becoming permanently shortened (contractures). Contractures are painful, disabling, and largely irreversible. Preventing them requires consistent stretching, not just when spasticity is bad, but as an ongoing daily practice.

The Spastic Paraplegia Foundation, which covers PLS and HSP management, recommends physical therapy for balance, gait retraining, spasticity management, and assistive device training. In clinical practice, PT goals for PLS include:

• Daily stretching of major spastic muscle groups (calf, hamstring, hip flexors, adductors)
• Positioning strategies to prevent contracture during sleep and seated rest
• Gait training to maintain as safe and efficient a walking pattern as possible
• Balance work to reduce fall risk — PLS patients are at genuinely elevated fall risk from both spasticity and toe-catching
• Instruction in adaptive techniques to reduce the energy cost of daily tasks

Aquatic therapy is particularly well-tolerated for spastic conditions. Warm water reduces tone directly, the buoyancy reduces fall risk, and the resistance provides a safe environment for strengthening and gait practice. Many people with PLS find that aquatic therapy sessions offer the best window of functional movement in their week.

Robot-aided gait training: the Lokomat case

In 2021, a case report published in Innovations in Clinical Neuroscience described the use of robot-aided gait training using the Lokomat-Pro system in a patient with PLS. The Lokomat is an exoskeleton that supports the patient's weight and guides leg movement through a normal walking pattern on a treadmill, providing consistent, repetitive input to the motor system.

In the PLS case, the combination of Lokomat training and conventional physical therapy produced significant improvements in walking speed, balance, lower limb strength, and spasticity measures. Conventional physiotherapy alone had not produced comparable functional improvement in this patient. This is a single case study and cannot be generalized, but it is meaningful for a rare disease with limited evidence: it demonstrates that intensive, technology-assisted gait rehabilitation can produce real functional gains in PLS, and that spasticity-driven disability is not entirely fixed.

Lokomat systems are available at some larger rehabilitation centers. If you are interested, asking your neurologist for a referral to a rehabilitation specialist familiar with neurological gait training is a reasonable step.

Cannabinoids: what CANALS showed

Cannabinoids are the most commonly asked-about investigational option for PLS spasticity, and for good reason. The CANALS trial — a 2019 Italian Phase 2 RCT of nabiximols (Sativex, a 1:1 THC:CBD oromucosal spray) in 60 patients with motor neuron disease, including PLS — found a modest but statistically significant reduction in spasticity over six weeks. Nabiximols was well tolerated and did not accelerate functional decline. The MS spasticity evidence base is much stronger and provides indirect support for the same mechanism.

There is a critical nuance that matters for PLS specifically. THC — the intoxicating compound — produces both the chronic spasticity benefit AND an acute impairment of motor coordination and balance. In someone whose upper motor neuron function is already compromised, the acute motor effects can be dramatic: a patient may find that walking becomes markedly worse for several hours after using recreational cannabis, even while the underlying chronic benefit is real. The distinction between THC and CBD — and between pharmaceutical preparations like nabiximols and recreational high-THC cannabis — is therefore not academic. It is the difference between a useful symptom management option and an intervention that makes daily function worse.

The full cannabis and PLS page walks through the CANALS evidence, the THC vs CBD distinction, the motor reserve problem, the withdrawal question after long-term daily use, and practical options for patients considering whether to continue, switch, or stop.