By Joshua Vova, M.D., FAAP, FAAPMR
The most common accepted definition of spasticity was characterized in 1980 by James Lance, who defined it as “a motor disorder characterized by a velocity dependent increase in (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex.(1)” In addition to increased muscle tone and hyperactive reflexes, spasticity can also contribute to weakness and poor coordination(2).
Spasticity results from an imbalance between the excitatory or inhibitory input from the alpha motor neurons and causes an increase in activation of the antagonist muscle due to damage to the central nervous system. Spasticity can also cause secondary changes to occur to muscle, tendon and collagen tissue properties such as stiffness, fibrosis and atrophy(3). Potential causes of spasticity include: spinal cord injury, traumatic brain injury, cerebral palsy, stroke, neoplastic syndromes and multiple sclerosis.
Uncontrolled spasticity may interfere with mobility, exercise, range of motion and activities of daily living as well as cause chronic pain and contribute to contractures and/or pressure sores(4). However, there are some positive effects associated with spasticity. It may may help maintain muscle tone in patients who are unable to ambulate, help support circulatory function, may prevent formation of deep venous thrombosis and may assist in ambulation or transfers(5).
When managing spasticity, the clinician must balance both the positive and negative effects of increases in muscle tone. Typically, spasticity does not increase over time. However there are external factors that can effect tone such as: infection, impaction, pressure sores, pain, deep vein thrombosis, increased intracranial pressure, stress, fatigue, sleep deprivation, environmental changes or even psychological factors.
Treatment of spasticity can be non-pharmacologic, pharmacologic or surgical. There are several factors that may influence the approach in treating spasticity: severity, chronicity, severity, distribution, locus of injury and co-morbidiites(6).
Spasticity may not necessarily develop immediately after an upper motor neuron injury, it may takes weeks or months to occur. Spasticity may improve as neurological recovery takes place. Spasticity of short-term duration may require a less aggressive approach than the patient who has had and contractures. However, one must address spasticity reduction immediately in order to maximize recovery during the period of CNS plasticity in the rehabilitation process.
An interdisciplinary team to design a treatment plan will often consist of physical therapists, occupational therapists, orthotists, physiatrists, neurologists, orthopedic surgeons and or neurosurgeons(4).
The cornerstone of treating all patients with spasticity is physical and occupational therapy. The goals of therapy are to help improve and maintain range of motion around a joint and strengthen muscles to improve function(4). When muscle become spastic, there is an imbalance of the muscle forces around a joint, which can lead to contracture and deformity. Techniques such as stretching, motor learning, strengthening exercises and constraint-induced therapy are often used to improve the properties of the muscle tendon units.
Serial casting can also be utilized to immobilize a spastic limb in a stretched position. Serial casting uses a series of casts in order to stretch the muscle and improve the passive range of motion. By using a cast, the muscle remains under slow, constant tension, which can modulate the muscles response to sensory stimulus and has also shown to improve the length and number of muscle fibers (sarcomeres), as well as the amount of connective tissue(7). Other possible techniques to help improve spasticity include kinesiotaping, which uses proprioceptive feedback and tension to influence movements, vibratory stimulation and electrical stimulation(4).
The use of orthotics, or braces, are frequently utilized in the treatment plan of spasticity. The goals of orthotics are to reduce pain, prevent contracture, improve function, compensate for loss of strength and sensation and reduce spasticity. An appropriately fitted orthotic can help to modify tone and reflexes to help a patient improve function and prevent deformity(4). Decisions regarding orthotic care are often a collaborative process between the physcian, therapist and orthotist to determine the appropriate design to help a patient accomplish a function and prevent further deformity.
Oral medications have demonstrated proven efficacy by inhibiting excitatory neurotransmitters or enhancing inhibitory neurotransmitters at the level of the spinal cord(3). Oral medications provide some advantages in the treatment of spasticity. They are noninvasive, not permanent and have proven to be clinically effective. However, some may be accompanied by side effects, including weakness and drowsiness, that may limit their effectiveness.
Many of the excitatory cortical spinal pathways that lead to spasticity are believed to be influenced by Gamma-aminobutyric acid (GABA), which is the main rationale for some of the pharmacologic options of treatment(5). There are currently two recognized GABA receptors: GABAA and GABAB. Benzodiazepines, medications like diazepam (Valium®) and clonazepam (Klonopin®) are the most common and oldest class of medications utilized medications to treat spasticity. Benzodiazepines act near the GABAA receptor to hyperpolarize the cell membrane and thus cause a presynaptic inhibition of polysynaptic and monosynaptic reflexes(2-4).
However, the effect that these medications have on the central nervous system is a limiting factor. These medications have the potential to cause sedation that can exacerbate potential cognitive deficits. Benzodiazepam overdose may also lead to somnolence, coma or death. These medications also carry the risk of physiologic addiction as well as a life-threatening withdrawal syndrome if they are abruptly weaned or discontinued. There also has been clinical evidence to demonstrate that these medications may interfere with neurologic recovery after brain injury and stroke, limiting their use as well(5).
Baclofen is a GABAB agonist. Baclofen acts both presynaptically and postsynaptically by crossing the blood brain barrier and acting at the spinal cord. Because of these properties, it is recommended for spasticity that is a result of cerebral and spinal cord origin(2).
Potential side effects can also include sedation, confusion, dizziness and nausea. Baclofen can also lower seizure threshold in patients who have seizures. Abrupt withdrawal can also lead to seizures, mental status changes or cardiovascular collapse. Gabapentin (Neurontin®) is an anticonvulsant with a chemical structure very similar to GABA. Although most commonly used now for neuropathic pain, it has shown some efficacy for decreasing spasticity at very high doses.(5) Its side effects include ataxia, headaches, tremors, somnolence, fainting and nystagmus(2, 3).
Another class of medications that has been used in treating spasticity is the imidazolines, alpha-2 adrenergic agents. These include the medications clonidine (Catapres®), which is known as a blood pressure medication, and tizanidine (Zanaflex®). These medications are believed to inhibit presynaptic afferents at the level of the spinal cord as well as inhibit the release of glutamate, an excitatory neurotransmitter(2). These agents are less utilized than the other medications mentioned above due to side effect profile and clinical efficacy(3, 5). Potential side effects include hypotension, sedation, dizziness, hallucinations, fatigue and hepatotoxicity(2, 3).
Dantrolene sodium is the only medication utilized for spasticity that does have its sight of action within the central nervous system but instead works directly on the muscle peripherally(3). Its mechanism of action is to block calcium release from the sarcoplasmic reticulum that results in decreased contractility of the muscle. Some clinicians feel that this may be better tolerated for patients who have spasticity of cerebral origin because it does not act centrally; lethargy and fatigue remain known side effects(2). Because it limits muscle contraction in all muscles, generalized weakness can also be a potential side effect. The major concern regarding dantrolene is that it has significant higher risks of hepatotoxicity compared with the other medications discussed. Risks for hepatotoxicity with dantrolene are increased at higher doses and in women older than 40(3).
Injectable medications also play a significant role in spasticity management. There is an abundance of literature supporting their efficacy for treatment. Neuromuscular blocks are used to restore the balance between agonists and antagonist muscles. The spastic muscle can be come shortened and contracted as noted above. However, the antagonist muscle can become over lengthened and weakened, further contributing to the imbalance. There are several injectable medications that can be employed to provide neuromuscular blockades. Botulinum toxin will decrease spasticity by working directly on the muscle(8). Alcohol and phenol produce their effect through direct neural destruction(9).
The FDA first approved botulinum toxin in 1989 for use in blepharospasm. Commercially, there are three different types of botulinium toxin A available and one type of botulinum toxin B. When injected into a muscle, botulin toxin interferes with the release of acetylcholine at the neuromuscular junction. This will cause the muscle to become weaker, allowing the patient to potentially exert more control over the muscle, strengthen antagonist muscles and/or tolerate orthotics/casting.
It is strongly recommended that localization of muscles to be injected utilize a localization technique such as EMG, electrostimulation or ultrasound(8). Failure to utilize localization techniques even in experienced physicians can decrease accuracy by 25 percent to 50 percent in lower extremities and 40 percent to 70 percent in upper extremities(10). Injections can only be repeated after three months to reduce the risk of systemic effects and antibody formation. Four to 10 percent of patients will develop antibodies to botulin toxin over time, reducing the effectiveness of repeat injections(5). To maximize effectiveness and limit potential complications, I strongly recommend that a patient is referred to a physician who is knowledgeable on dosing, types and frequency of side effects and methods of localizing muscles for injections. Potential side effects can include bleeding, infection, pain, undesired weakness, swallowing problems, breathing problems and a flu-like illness(8).
Phenol and alcohol are neurolytic agents that are employed to reduce spasticity. The mechanism of action is reducing neural transmission by chemically denaturing nerve fibers. It requires the clinician to be able to localize the nerve using electrostimulation and/or ultrasound and slowly injecting the nerve directly until response to the stimulation abates(4).
The effects of phenol and alcohol have a longer duration of action than botulin toxin, but there are the risks for potentially more side effects. Injections can be very painful and especially in children require sedation. Other risks include dysesthesias, blood vessel sclerosis, compartment syndrome, venous thrombosis and skin necrosis(11). Commonly, these injections are used in conjunction with botulinum toxin. Due to dosing imitations of botulinum toxin, multiple injection sites may limit efficacy of the medication. The clinician can use phenol or alcohol to target larger muscles (i.e. adductors and hamstrings) that would normally require large doses of botulinum toxin and focus their botulinum toxin injection sites(9). Failure to recognize these limitations may result in under dosing of medication and subsequent failure of the treatment plan.
Intrathecal Baclofen Pump. Intrathecal baclofen is used to treat spasticity by surgically implanting a mechanical device that directly infuses baclofen through a catheter into the intrathecal space around the spinal cord. Flexibility of the site of catheter implantation allows this to be an effective strategy for treating both upper and/or lower extremity spasticity.
This strategy is utilized when spasticity is refractory to the methods discussed above. The advantage is that higher concentrations of baclofen can be directly infused into the area of action around the spinal cord without the systemic side effects that accompany the oral medication. This allows for either a consistent dose of medication to be delivered or flexible programming based on a patient’s needs(12).
Although the initial implantation of the device requires a surgical procedure, adjustment to dosing and medication refills can be done noninvasively in a physician’s office. As with all medications, dosing requires an experienced physician to avoid potential side effects from overdose. In addition, risks from the surgical implantation include infection, headache from cerebrospinal fluid leak, catheter migration, disconnection or blockage(13).
Selective Dorsal Rhizotomy. Selective Dorsal Rhizotomy is a surgical intervention that targets lower extremity spasticity. This procedure is performed by a neurosurgeon who will perform a laminectomy orlaminotomy and selectively separate the L2-S2 motor and sensory nerve roots. Electrical stimulation of the individual sensory nerve roots is performed, and the ones that demonstrate abnormal patterns of sensory feedback are selectively ablated(14). The goal is to maintain a balance between reductions of spasticity and preservation of function.
Potential risks of this surgery include hyperesthesia, loss of bladder function and loss of previous ability to walk. Typically, in order to have the most benefit from his procedure, candidates for selective dorsal rhizotomy have to demonstrate some form of independent ambulation prior to surgery and not have any damage to the basal ganglia in the brain. Following this procedure, a patient must be able to participate in an extensive rehabilitation program usually requiring therapy four to five times a week for three to six months to maximize functional return.
Orthopedic Surgery. Orthopedic intervention for spasticity is mainly used to correct the effects of spasticity or balance the forces caused by the spastic muscles. Over time, spasticity may cause muscle and soft tissues contracture or bony deformity. By releasing muscles that cause a deformity, a more favorable balance can be achieved. Orthopedic surgeons may functionally lengthen a short muscle by tenotomy, lengthening the tendon alone or in- tramuscular lengthening of the fascia around the muscle. They may also consider transferring a muscle to compen- sate for a weaker antagonist muscle. Bones may also be repositioned or reshaped to help maintain motion(15).
The care for individuals with spasticity may be a complex process. Although the neurologic condition is usually static, the changes to muscle, bone, tendon and ultimately function over time is a dynamic process that needs to be actively managed. Appropriate management of the patient with spasticity requires a multidisciplinary team of experienced physicians and allied health professionals who are able to work together.
Joshua Vova, M.D., FAAP, FAAPMR, is a pediatric physiatrist. He graduated from University of South Florida Medical School in 2000 and completed his residency in pediatric at Jacobi Medical Center in New York. Following his pediatric residency, he completed a residency in physical medicine and rehabilitation at the Rehabilitation Institute of Chicago and a fellowship in Pediatric Rehabilitation Medicine at The Children’s Hospital in Denver. Dr. Vova currently serves as a pediatric physiatrist at Children’s Healthcare of Atlanta and fellowship director for the Pediatric Rehabilitation Medicine fellowship through Emory University and Children’s Healthcare of Atlanta.
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