Cerebral palsy (CP) is a non-progressive brain disorder characterized by insufficient development of postural reflexes (i.e. head control), prolonged retention of primitive patterns of activity, abnormal coordination and muscle patterning.
As a result, those with cerebral palsy have delayed motor development and impaired patterns of movement.”1,2 It is a chronic disabling condition of childhood. It is occurs in 1.5/1,000 to 3/1,000 live births with spasticity as a prevalent disabling clinical symptom.3
When evaluating infants, physicians should be aware there are two signs that suggest the possibility of cerebral palsy as a diagnosis. One sign is the presence of hyperactive deep tendon reflexes in a hypertonic or hypotonic child. The other sign is a unilateral or bilateral persistence of neonatal reflexes beyond the time that they should have disappeared or been absorbed into a more sophisticated reflex.4
Spasticity is a form of cerebral palsy in which pyramidal system dysfunction leads to an inhibitory imbalance. This loss of inhibitory control contributes to an exaggerated spinal stretch reflex. As a result, patterns of voluntary movement are altered because this loss of inhibitory control leads to concurrent firing of muscle groups such as adductors and abductors.
Although cerebral palsy causes a variety of upper motor neuron dysfunctions, spasticity is the most common and typically results in asymptomatic foot dysfunction. As the child grows, longstanding imbalances between agonist and antagonist muscle groups can lead to fixed deformities of the foot such as muscle contractures and bony deformities, some of which may require surgery to correct.
It is typical of the spastic individual to have concomitant abnormalities in the superstructure such as the hip and knee that may have an impact on closed-chain foot position and function. Conversely, one must consider the retrograde role of abnormal foot postures on hip and knee position and function as well.
Keys To The Clinical Exam
In regard to the lower extremity assessment for these patients, it is important to correlate restricted joint range of motions with gait abnormalities. For example, one should take care during the clinical exam of ankle dorsiflexion to avoid a forceful slow stretch that tends to overestimate the functional range of motion actually available at the joint one is evaluating. Standing and walking tend to increase spasticity and the two-finger method of assessing joint range of motion offers a more approximate assessment of the motion actually available in gait.
Further complicating the assessment of ankle range of motion is that clinical assessment of the gastroc and soleus muscles as separate units can be difficult in this population. Traditional comparison of ankle dorsiflexion with the knee extended and knee flexed to distinguish the two muscles proves difficult as the position of adjacent joints affect spasticity.
However, examining ankle dorsiflexion in both knee positions is still valuable as children with increased dorsiflexion to 10 to 15 degrees with the knee flexed versus extended is suggestive of greater gastrocnemius involvement. These patients tend to have plantarflexion of the ankle in swing and early stance phase, but can achieve dorsiflexion in midstance.
There is growing enthusiasm for the role of instrumental gait analysis in evaluating patients with spasticity. It is helpful in determining exact information on abnormal muscle firing in such patients. It has been documented that preoperative gait analysis does alter surgical decision-making.5 One should seriously consider this when planning surgery.
Physical therapy, orthoses and/or manipulation are first line options for patients with spasticity. Even for those children who may eventually require surgery, the use of these modalities to delay surgery until the age of 6 to 8 years is considered advantageous.
How Referrals To Physical Therapy Can Be Beneficial
When working to help children with spasticity, physical therapists first seek to establish head control. Then they work on balance of the trunk for sitting and proceed to the reciprocal lower-extremity motion needed for locomotion beginning with crawling, pulling up to stand and eventually walking. Current physical therapy options include neurodevelopmental therapy, sensory integration therapy, pressure-point stimulation, bracing, stretching and recreation-based therapies.6
According to Morrissey and Weinstein, a review of the literature yields a wide variety of conclusions on the efficacy of many of these approaches.7 While some studies report impressive results, others offer more modest outcomes. Problems with research techniques employed in some of these studies make it difficult to point to definitive outcomes with evidence of efficacy.
The physical therapist should document motor function at regular intervals during early development in order to record improvements resulting from therapy. Systems available to the clinician for such documentation include Movement Analysis of Infants, Gross Motor Performance Measure and Pediatric Evaluation of Disability Inventory.8
The benefits of referrals for physical therapy include:
• postoperative rehabilitation to maximize the benefits of surgery;
• prevention of joint contractures with supervision of daily range of motion programs, often provided by other family members or caregivers;
• having a primary resource for selecting adaptive and therapeutic equipment;
• family education on potential and limitations of the child;
• advice on home and community modifications;
• acting as a liaison with schools and other healthcare professions; and
• the fabrication of select splints and orthoses.9
What About Orthotic Management?
In regard to the use of orthoses in patients with spasticity, Drennan maintained that orthoses can “ … prevent deformity, correct a passively correctable deformity, provide stability and enhance function.” However, he emphasized that “bracing cannot correct a fixed deformity and failure to recognize this will lead to orthotic failure.”10
Additional uses for orthoses in this patient population may include improving positioning of the extremity, modulating tone and improving function by substituting for a weakened muscle or protecting a weakened part.7,11 The primary use for daytime lower extremity orthoses in patients with spasticity is when the ankle is in dynamic equinus or there is a varus preposition of the rearfoot in swing.7
When patients have spastic diplegia, lower-extremity orthoses almost never have to extend above the knee.12 At the foot level, a University of California Biomechanics Lab (UCBL) orthosis is the device of choice to provide subtalar and forefoot alignment of the non-rigid foot but control of the ankle is not necessary.
Leung, et al., found that the use of UCBL orthoses by eight individuals had a significant effect on the orientation and movements of the subtalar joint, ankle joint and knee joint. This included an immediate effect of reducing the degree and duration of abnormal pronation during the stance phase.13
AFOs: Can They Have An Impact?
In regard to facilitating ankle level control via ankle foot orthoses (AFOs), the most common device physicians utilize is the solid ankle type of AFO. These AFOs allow control of the foot. They eliminate plantarflexion during the swing phase with increased ankle dorsiflexion at the time of contact, enhance medial and lateral stability, and helps maintain plantigrade foot-ground contact. This facilitates continued plantarflexion knee extension coupling.
The solid ankle type of AFO also allows an increased late stance ankle moment that is reflected in a more normal center of pressure transition from midfoot to forefoot. It also increases the weightbearing area of stance, which may provide an increase in gait stability in a typical patient who has spastic diplegia and a classic scissor or crouch gait with exaggerated stance phase knee flexion, increased hip adduction and internal rotation.12
Be aware that these foot abnormalities may shift ground reaction forces posteriorly and laterally, thus increasing the flexion, valgus and external rotation moments. Correction of these foot deformities should reduce these abnormal ground reaction forces.14
In one study, researchers documented the effect of AFOs in children with spastic diplegia by analyzing their gait with and without AFOs. They found the orthoses reduced the high impact forces one may see in early stance phase and increased the vertical ground reaction forces in the late stance phase.
The authors concluded that AFOs improved the ability to support the body weight and to generate more appropriate push-off.14
In another study involving 35 patients with spastic diplegia, Abel et al., found significant increases with AFOs when it came to velocity, stride length and the percentage of single limb support versus barefoot. They further concluded that AFOs enhanced gait function as a result of eliminating premature plantarflexion forces and improving progression of foot control during stance.15
Radtka, et al., studied the effect of solid and dynamic (hinged) AFOs on patients with spastic cerebral palsy and found that both orthoses increased stride length, decreased cadence and reduced excessive ankle plantarflexion in comparison to a control group with no orthosis.16
The posterior-leaf spring (PLS) variation of the solid AFO allows some plantarflexion and dorsiflexion from neutral while preventing foot drop in swing. However, this variation sacrifices medial and lateral stability. It may have its widest application in the population when there is minimal spasticity. Ounpuu, et al., have shown that a PLS device contributes to an improved ankle modulation.17 It is flexible enough to allow dorsiflexion in midstance and allow minimal plantarflexion in the pre-swing phase.
Historically, spring-loaded dorsiflexion AFOs aided in ground clearance during swing phase. However, this kind of AFO is contraindicated in a patient with cerebral palsy who has a pathologic stretch reflex. Conversely, in this population, inhibition of excessive plantarflexion is the desired goal. Modern articulated AFOs generally have hinged ankles and plantarflexion stops designed to prevent this equinus and extensor thrust while encouraging ankle dorsiflexion. They may also provide for more tibialis anterior muscle function.8
Advantages of the articulated AFO include improved dorsiflexion activities such as bending and stair climbing. Disadvantages include less medial and lateral ankle support, increased bulk around the ankle (which may make shoe fit challenging), and an increased risk of soft tissue irritation around the heel and malleoli. Other potential negatives include a blocked plantarflexion-knee extension couple and triggering of the gastrocnemius stretch reflex, making the patient more likely to fight the brace.8
Researchers have also shown that hinged AFOs have a beneficial effect on gait in children with cerebral palsy.13 In one case study comparing the effect of fixed versus hinged AFOs in a child with spastic diplegia, Middleton, et al., found the child’s pattern of ankle dorsiflexion was more normal and the knee muscle movements were lower during the stance phase of gait with the hinged design in comparison to a fixed AFO.18
In 2004, Lam, et al., studied the biomechanical and electromyographic effects of solid and hinged AFOs on gait in patients with spastic cerebral palsy.19 They concluded that both devices led to longer stride length, permitted pre-positioning for initial contact and successfully controlled the excessive plantarflexion during swing phase. The hinged AFOs allowed a significantly larger total ankle range of motion.
The researchers found a median frequency of electromyography (EMG) signal in these patients’ lower limbs that resulted in tiredness.19 Solid AFOs reduced this median frequency and hinged AFOs did not. This would suggest an improved walking endurance with solid AFOs.
In another study, Rathlefson, et al., concluded that articulated AFOs allow more normal ankle kinematics and kinetic pattern during gait than fixed AFOs do without affecting the knee position during stance, leading to an improved plantarflexion moment. They concluded that an articulated AFO might be appropriate for patients who have varying degrees of calf spasticity as long as passive range of motion to at least neutral is available at the ankle.20
A final option worth considering is the floor reaction AFO that uses the plantarflexion–knee extension couple to reduce knee-flexion crouch and improve stance phase knee extension during gait with a plantigrade foot. It works best when less than 10 degrees of knee flexion contracture is present, hip extension is full and no major rotational malalignments are present in the lower extremity.7 This is an example of an orthosis enhancing function, in this case, the absence of normal quadriceps function.8
Pertinent Points On Inhibitory Casting And Tone Reducing Orthoses
The tone-reducing ankle-foot orthosis (TRAFO) emerged as an extension from the popular but controversial strategy of inhibitory casting as an adjunctive treatment for children with cerebral palsy.
The procedure for casting is to apply carefully molded bilateral below-knee casts in an attempt to inhibit normal tonic plantar reflexes, particularly the grasp reflex, resulting in reduced tone. Further, casting and tone reducing orthoses both provide a reflex inhibitory position of the splinted limb to prevent abnormal postural patterns and minimize the spasticity associated with increased muscle tone.13
The principles behind inhibitory casting/positioning include:
• positioning of the ankle plantarflexors and long toe flexors to provide a prolonged stretch on tendons of the long toe flexors;
• prevention of reflexes induced by tactile stimulation;
• influence on proprioceptors through joint compression provided by weightbearing in proper alignment; and
• altered muscle length, resulting in a change in resistance to passive stretch, improved recruitment and sequencing of muscle activity.21
One study of tone-reducing casts found a significant improvement in stride length for a casted group of children in comparison with an uncasted group.22 In a single-subject research design with the patient serving as his or her own control, Harris and Riffle reported improved standing balance in a child with cerebral palsy when the child wore a TRAFO.23 However, researchers have noted a caveat concerning the use of these methods, noting that a child may not maintain any improvement in tone for a long period of time. This raises questions about the long-term benefit of this modality.24
A study comparing the effect of stretch casting on children with spastic cerebral palsy and idiopathic toe walking found both groups had increased dorsiflexion range and decreased resistance to passive stretch. Immediately after casting, no children exhibited toe walking but two children with cerebral palsy resumed a digitigrade pattern six weeks later.25
Weighing The Pros And Cons Of Intramuscular Injections
In addition to the aforementioned conservative modalities, there are emerging therapeutic options that may be helpful in the modulation of spasticity. These modalities include oral medications, intramuscular injections, intrathecal injections and selective dorsal rhizotomy.
In the past, there were a number of oral medications that were suggested for modulating spasticity. They included muscle relaxants, antispasmodics and neuroinhibitory medications. However, there has been little success with these modalities, mostly because the large therapeutic dose required with these agents leads to serious side effects, most notably severe drowsiness.26
The use of intramuscular or perineural injections in the management of spasticity has gained a foothold in recent years. One of the goals of this therapy is to weaken a muscle temporarily to see how a change in the muscle dynamic across a joint may change function. Although the effect is temporary, it may be useful in directing future care, including surgical planning, for the child.
Other objectives of performing these injections include:
• determining if spasticity or fixed joint contracture is the cause of reduced range of motion;
• isolating the muscle responsible for a postural or gait abnormality; and
• assessing the function of antagonistic muscles.27
These injections may range from a simple local anesthetic agent to observe the effect of a nerve block to the use of longer-acting agents to try to create a sustained change. One may use agents such as phenol on nerve fibers in an attempt to make the effect permanent. Injection of 45% alcohol into muscle fibers to inhibit nerve transmission and muscle contraction has gained some popularity in the management of spasticity. A major drawback of intramuscular alcohol injections is that they are painful and therefore require general anesthesia. While the duration of effect for a successful alcohol injection varies, it is usually about six weeks.28
One may use botulinum-A toxin (BTA) (Botox, Allergan) for intramuscular injection to block the release of acetylcholine from presynaptic vesicles at the myoneural junction. Physicians usually inject BTA into the muscle belly located by palpation. One can do this without the use of anesthesia as they diffuse rapidly although topical anesthetics can reduce local discomfort. In some cases when one must identify deep muscles, electromyographic guidance and electrical stimulation may help.29
Botulinum-A is expensive and there is some variability on optimal dosing. The effect begins 12 to 72 hours after injection and usually lasts for three to six months or longer. One may repeat injections after two or more weeks, and administer up to six injections at any one site.30 Take care not to use this method when fixed joint contractures are present.
Botulinum-A seems to have its best indication in very young patients with select muscle involvement and may prove valuable as a strategy to delay surgical intervention. Several studies have shown improvement with this therapy in children with equinovarus or equinovalgus feet.31,32
Research has shown BTA to be safe at high doses. Goldstein reported no serious adverse effects in children weighing < 45 kg who received BTA doses of 15 to 22 U/kg of body weight or in young adults > 45 kg who received BTA doses of 800 U to 1,200 U in a single injection protocol.33
In the first randomized control of BTA to report outcomes globally across all domains of the National Centers for Medical Rehabilitation Research (NCMRR), Bjornson, et al., documented significant reduction in spasticity, significant changes in mechanical efficiency and motor function at six months after treatment.34
They concluded that the physiologic and mechanical effects of BTA are “genuine and measurable in youth with spastic CP. However, these effects may not create enough change in the patient’s function or the families’ perception of the function to register as a meaningful improvement in their societal participation.”
They postulate further that “it is possible that these changes were too subtle to be recognized with conventional atisfaction measures.” The study authors also encourage providers to temper patient and family expectations about this modality before they consider its use.
What You Should Know About Intrathecal Injections
Baclofen (Lioresal, Medtronic) is an agonist of the neuroinhibitor gamma-aminobutyric acid (GABA), which interferes with transmiiters that cause spasticity. Intrathecal injection of this agent acts on spinal cord synaptic reflexes to decrease lower extremity spasticity for about eight hours. Intrathecal administration is preferable to oral dosing using a refillable, subcutaneously implanted pump. Complications associated with the use of the pump system have been decreasing as experience with their use increases.
Currently, the indication for this therapy appears to be primarily for patients with dystonia and spasticity who have hygiene problems and difficulty with sitting.35 This modality may also be indicated for those who are ambulatory with underlying weakness. This weakness makes them poor candidates for selective posterior rhizotomy. It also has a potential application as a trial to determine if selective posterior rhizotomy would be appropriate for a particular patient.
A 2005 study of patients treated with intrathecal baclofen showed a significant reduction in tone after a bolus injection followed by an implanted pump for continued delivery of intrathecal baclofen.36 Those patients under the age of 18 showed significant improvement in gross motor function measures one year following pump implantation.
Should You Consider Referring The Patient For A Selective Posterior Rhizotomy?
Selective posterior rhizotomy is designed to reduce spasticity and improve muscle tone by changing the control exhibited by the anterior horn cells located in the spinal cord. In children with spasticity, normal inhibitory impulses from higher brain centers to the anterior horn cells are deficient. This effect is further exacerbated by inadequate coordination of movement from alpha motor neurons.
The selective rhizotomy attempts to limit stimulatory input arriving by afferent fibers in the dorsal roots. The general anesthesia procedure selectively sections dorsal rootlets with impulses exerting excessive influence on the anterior horn cell. Intraoperative electromyographic and physical responses to stimuli occur and surgeons divide those rootlets serving the involved muscles.
When considering whether to refer a patient for this procedure, selective posterior rhizotomy seems best suited for a young child (age 3 to 8 years) with spastic diplegia; voluntary muscle control; reasonable intelligence and motivation; an absence of fixed contractures; good trunk control; an ability to walk with good underlying strength and balance; and severe, pure spasticity. These patients may have also been born pre-term or had a low birth weight.
In the early postoperative period, intensive physical therapy is required as the patients are weaker than they were before the surgery. Studies have shown a reduction in spasticity; increased hip, knee and ankle range of motion; a plantigrade foot in stance; increased stride length and walking speed; and no increase in sensory deficits after a selective rhizotomy.13 Three randomized trials comparing rhizotomy and physical therapy have shown rhizotomy is more successful at reducing muscle tone and is often more successful at improving motor function.37-39
Adjunctive orthopedic surgeries to correct joint contractures or an overly contracted musculoskeletal unit are necessary after rhizotomy for up to 65 percent of patients.40-42
There often remain significant challenges for the spastic child even after a successful posterior rhizotomy. These challenges include persistence of many of the other issues that affected the child preoperatively. There are also occasional complications from the procedure including severe hip subluxation or dysplasia, an increase in sagittal plane anterior pelvic tilt in independent ambulators and the development of significant planovalgus deformities in up to 50 percent of cases, sometimes requiring surgical correction.42-45
Gul, et al., did a retrospective analysis of data collected prospectively to determine the long-term outcome of lumbosacral selective posterior rhizotomy (SPR) in children with cerebral palsy.46 They noted significant improvements in spasticity, range of motion and muscle strength at one year and at five years after SPR. They concluded that improvements in lower limb motor outcomes are present at one year after SPR and these improvements are generally maintained at five years.
Selective posterior rhizotomy has become an attractive option for many children and their families. However, it is expensive, long-term results have not been established and careful patient selection and surgical technique are essential to positive results.
Dr. Volpe is a Professor in the Department of Orthopedics and Pediatrics at the New York College of Podiatric Medicine. He is a Diplomate of the American Board of Podiatric Orthopedics and Primary Podiatric Medicine. He is in private practice in Farmingdale, N.Y. and New York City.