Damage to the brain’s motor control centers following a stroke can result in significant changes to muscle function, a condition known as hypertonia. This increased muscle stiffness presents a major challenge to recovery, often limiting mobility, interfering with daily activities, and contributing to pain. Implementing targeted interventions is necessary for improving movement and overall quality of life for stroke survivors.
Understanding Post-Stroke Hypertonia
Hypertonia, the pathological increase in muscle tone, is a common consequence of damage to the upper motor neurons within the brain or spinal cord. This neurological injury disrupts the signals that normally descend from the brain to inhibit spinal reflex activity. The loss of this inhibitory control leads to hyperexcitability of the spinal reflexes, causing muscles to become overly reactive to stretch and movement.
Spasticity is a specific type of hypertonia defined by a velocity-dependent resistance to passive stretching. This means the faster a limb is moved, the more the muscle resists movement, often resulting in sudden, involuntary muscle contractions or spasms. While treatment aims to reduce this pathological stiffness, completely eliminating all muscle tone is not desirable, as some tone is necessary to maintain posture and facilitate functional movement.
The resulting muscle imbalance often leads to abnormal posturing, such as the arm flexing at the elbow and wrist, or the leg extending stiffly. If left unmanaged, chronic hypertonia can cause muscles to shorten permanently, leading to fixed joint limitations known as contractures. Early identification and management of abnormal tone are important to prevent these secondary complications and maintain the potential for functional recovery.
Rehabilitative and Positioning Strategies
Physical and occupational therapists employ specific, non-pharmacological techniques to manage and decrease muscle tone. Stretching protocols are the foundation of this approach, focusing on slow, sustained stretches that hold the muscle at its maximum comfortable length for prolonged periods, often 30 minutes or more. This extended, low-load stretch helps to physically lengthen the muscle fibers and connective tissues, gradually reducing stiffness.
Therapeutic exercise also includes strengthening the muscle groups that oppose the spastic muscles, known as the antagonists. By activating muscles responsible for extension, such as the triceps, therapists leverage reciprocal inhibition, which naturally causes temporary relaxation in the opposing flexor muscles. This dual approach of stretching tight muscles and strengthening weak, opposing muscles helps restore a more balanced muscular environment around the joints.
Proper positioning is necessary to prevent contractures and minimize the effect of gravity on hypertonic limbs throughout the day and night. This involves positioning the affected arm and leg in neutral or slightly extended postures while the patient is sitting, standing, or lying down. Specialized seating systems and supportive surfaces help maintain these beneficial positions, preventing abnormal posturing that reinforces muscle stiffness.
Splinting and orthotics are mechanical supports used to maintain soft tissue length and provide a low-intensity, prolonged stretch to the affected limbs. Static splints hold the joint in a fixed, functional position, typically worn overnight to prevent shortening. When hypertonia has led to significant shortening, serial casting may be used. This involves applying a rigid cast to hold the limb at its maximum stretch for several days before replacing it with a new cast at a slightly increased range.
Other modalities provide temporary relief from muscle stiffness, allowing for more effective stretching or exercise sessions. Cold therapy, such as ice packs, can decrease nerve conduction velocity and reduce reflex excitability in the spastic muscle. Functional Electrical Stimulation (FES) or Transcutaneous Electrical Nerve Stimulation (TENS) may also be applied to the skin over the muscle to temporarily reduce muscle tone or facilitate contraction of the opposing muscles.
Medication and Injection Therapies
Pharmacological interventions are used alongside rehabilitation when hypertonia significantly impairs function or causes discomfort. Oral medications work systemically by acting on the central nervous system to reduce the excitability of the motor pathways. Baclofen is a commonly prescribed drug that acts as an agonist at the GABA-B receptor, enhancing inhibitory neurotransmission within the spinal cord.
Tizanidine, another oral muscle relaxant, is an alpha-2 adrenergic agonist that increases presynaptic inhibition of motor neurons in the spinal cord. Diazepam, a benzodiazepine, potentiates the inhibitory effects of GABA-A receptors, leading to generalized muscle relaxation. A major limitation of these oral agents is their systemic effect, which can cause side effects such as generalized weakness, sedation, and drowsiness, potentially hindering rehabilitation.
For patients experiencing focal spasticity—tightness concentrated in specific muscle groups—Botulinum Toxin (BoNT) injections are the standard targeted treatment. BoNT is a neurotoxin injected directly into the hypertonic muscle, where it blocks the release of acetylcholine at the neuromuscular junction. Since acetylcholine is the neurotransmitter required for muscle contraction, blocking its release chemically weakens the injected muscle.
The localized nature of the injection minimizes the systemic side effects seen with oral medications, allowing for muscle relaxation exactly where needed. The effect of the toxin is temporary, typically lasting between three and six months before nerve terminals begin to sprout and restore acetylcholine release. Injections are often timed to coincide with intensive physical therapy, utilizing this temporary window of reduced tone to maximize functional gains and range of motion.
Advanced Interventions for Severe Tone
When severe, generalized hypertonia does not respond adequately to oral medications or repeated focal injections, advanced interventions may be considered. The Intrathecal Baclofen (ITB) pump is a device implanted surgically to deliver Baclofen directly into the cerebrospinal fluid (CSF) surrounding the spinal cord. This targeted delivery bypasses the blood-brain barrier, allowing for a higher concentration of the drug at the site of action while minimizing systemic side effects like sedation.
An ITB pump is typically reserved for individuals with severe spasticity affecting multiple limbs that significantly interferes with positioning, hygiene, or comfort. The pump is programmable, allowing clinicians to adjust the precise dosage and delivery schedule to optimize tone management. This intervention provides relief from stiffness, although it requires surgical implantation and ongoing maintenance.
For cases where chronic hypertonia has resulted in fixed contractures that prevent movement, orthopedic or neurosurgical procedures may be necessary. Orthopedic surgeons perform procedures such as tendon lengthening (tenotomy) or tendon transfers to physically release tension and improve the range of motion around a joint. Neurosurgical options, like selective dorsal rhizotomy, involve cutting specific sensory nerve roots in the spinal cord to reduce the reflex input driving the spasticity. These surgical interventions aim to correct fixed deformities and alleviate pain when non-invasive measures have failed to maintain joint integrity.