The effects of intrathecally administered baclofen on function in patients with spasticity.

Key Words: Baclofen, Central nervous system, Pharmacology, Spinal cord injuries.

In 1980, neuroscientists developed a consensus that spasticity should be defined as a

... motor disorder characterized by a

velocity-dependent increase in tonic

stretch reflexes ("muscle tone") with

exaggerated tendon jerks, resulting

from hyperexcitability of the stretch

reflex, as one component of the upper

motor neuron syndrome.[1(p485)]

We will use this definition of spasticity. When clinicians use the term "spasticity," however, they are typically referring to a wider constellation of abnormal reflexes and neuromuscular signs associated with impaired movement. Research continues to clarify these characteristics and how they differ across neurologic conditions. For example, when supraspinal control of spinal cord function is lost as a result of spinal cord injury (SCI), there is altered motor unit activity in response to either sensory or central inputs that lead to co-contractions, mass movements, and abnormal postural control.[2] Polysynaptic flexion reflexes (spasms) are also characteristic. Hyperexcitability of motoneurons and abnormalities of supraspinal control of reciprocal inhibition of antagonist muscles during voluntary agonist activation are characteristic of movement in individuals with cerebral palsy (CP).[3] As a result, voluntary movement is characterized by extensive co-activation of muscle activity that often includes muscles in a variety of segments. The characteristics of the motor disorder following cerebrovascular accidents (CVAs) change over the course of recovery,[4] and, over time, peripheral changes in the mechanical properties of muscle contribute to resistance to voluntary movement in both CVA and CP.[4,5] We will use the term "abnormal postural tone" to refer to the wider constellation of spasticity and abnormal neuromuscular signs that are associated with impaired movement in these conditions.

The reduction of abnormal postural tone with the aim of improving the functional performance of clients with central nervous system (CNS) dysfunction has long been a goal of physical therapy. Physicians and therapists have continued to search for ways to reduce spasticity, and one of the recent implements in the armamentarium of approaches to this problem is intrathecally administered baclofen, a pharmacologic antispasticity agent. In this approach to reducing spasticity, the drug is infused into the subarachnoid space overlying the dorsal spinal cord by a subcutaneously implanted pump and catheter system. Intrathecally administered baclofen has been shown to effectively reduce spasticity and involuntary spasms in clients with spinal injury, such as SCI and multiple sclerosis (MS),[6-18] but investigation of effects in patients with brain damage leading to spasticity, such as CP and traumatic brain injury (TBI), continues.[19-23]

Despite evidence from the literature that spasticity can be reduced with surgical, pharmacologic, or physical modalities such as augmented sensory feedback, doubts have been expressed that the reduction of spasticity automatically results in improved function.[5,24,25] For example, children with CP in whom spasticity has been reduced by selective posterior rhizotomy continue to move using abnormal movement synergies.[26]

The purpose of this article is to review the documented effects of intrathecally administered baclofen and to address the question of whether spasticity reduction results in improved functional performance or primarily acts to decrease bothersome positive symptoms of CNS dysfunction, such as spasms, without improving coordination or other movement characteristics. We will first present a framework for summarizing the results of applying new treatments such as intrathecally administered baclofen, and we will then review the literature within the structured format provided by this framework. Finally, brief mention will be made of a protocol we have developed for studying the effects of intrathecally administered baclofen on functional outcomes in clients with supraspinal causes of spasticity.

A Framework for Evaluation of The Results of New Treatments

The National Center for Medical Rehabilitation Research (NCMRR) of the National Institute of Child Health and Human Development suggests that new methods of treatment should be evaluated for effects on multiple dimensions of the disabling process.[27] A model that describes the process at multiple levels of analysis would also be useful in improving the theoretical structure of research protocols and in designing new investigations.

A proposed model developed at the NCMRR by the center's National Advisory Board combines aspects of the World Health Organization's system for classifying impairments, disabilities, and handicaps[28] with the model developed by Nagi.[29] The Nagi model includes a category of functional limitations in total body activities that addresses an important aspect of intervention by physical therapists. The first four dimensions of the NCMRR model are (1) pathophysiology, (2) impairments, (3) functional limitations, and (4) disabilities. These dimensions include both primary and secondary effects on bodily functions of the person with a disabling condition and ability to perform appropriate social roles. The final dimension of the NCMRR model is societal limitations. Social limitations are barriers to full participation in society of persons with disabilities because of attitudes, architectural barriers, and social policies, and this dimension of the NCMRR model will not be discussed further in this article. Each of the first four dimensions will be defined, followed by a review of the literature on intrathecally administered baclofen pertaining to that dimension.

Review of the Literature

Baclofen's Effects on Pathophysiology

Pathophysiology in the NCMRR model encompasses the cellular and molecular processes of injury or disease pertinent to a particular condition.[27] In spastic conditions, sensory inputs and abnormal supraspinal mechanisms result in excessive activation of alpha motoneurons controlling muscle contraction.[30] The pathophysiology of abnormal postural tone and movement varies among clients with nervous system dysfunction caused by different conditions, such as SCI, MS, and CP, but they all share the problem of hyperactive stretch reflexes. Baclofen (Lioresal, B-[4-chlorophenyl]-GABA) is a gamma-aminobutyric acid (GABA) agonist (ie, a drug capable of combining with membrane receptors that are normally influenced by GABA), but baclofen only partially mimics the effects of the natural neurotransmitter.

Two types of GABA receptors, called A and B types, are found on neurons in the brain and spinal cord, and baclofen selectively affects only the GABA-B receptors, thereby inhibiting neurotransmitter release.[14,31] In animal models, GABA-B receptor numbers are increased after SCI. In humans with SCI, a defect in the GABA-B receptors is presumably involved in the production of both involuntary spasms and increased tone. Baclofen reduces the influx of calcium in presynaptic terminals of afferent fibers and can affect the postsynaptic membrane by increasing potassium influx and by stabilizing or increasing the membrane potential to inhibit neuron firing. Through this mechanism, baclofen reduces hyperactivity of both monosynaptic and polysynaptic muscle stretch reflexes, clonus, and culaneous reflexes eliciting muscle spasms.[30,32] By comparison, diazepam, the other centrally active antispastic medication, works by binding to the presynaptic membrane and facilitating GABA-induced chloride channel opening, which involves GABA-A receptors.[30,33] Diazepam works only when GABA is released, whereas baclofen directly activates the membrane receptors.

The intrathecal route involves surgical implantation of a pump, which bears the risks of infection and local anesthetic exposure. The pump is inserted into a subcutaneous pocket in the abdominal area; the catheter is threaded into the subarachnoid space, and in some pump systems a radio transmitter can be used to adjust the dosage when needed. Current pump designs have a reported failure rate of 3% to 7% due to faulty mechanisms; improved new systems are expected to reduce the failure rate. The pump must be replaced when the batteries fail after 3 to 5 years.[34] Catheter kinks and other disruptions occur more frequently but can be readily corrected surgically under local anesthesia. Overdoses can occur but are rare.35

Clients involved in the research on the efficacy of intrathecally administered baclofen are those who have found orally administered baclofen to be unsuccessful in controlling symptoms of spasticity or have experienced disabling side effects such as drowsiness or mental confusion because of high dosages. Intrathecal administration of the drug is more successful because smaller doses can be used to achieve relatively large cerebrospinal fluid (CSF) concentrations of baclofen in localized spinal cord areas with only a small systemic effect. For example, with lumbar infusion at L4-5, the concentration of drug at T-2 is only about 43% of that at T-12 and is still lower in brain CSF.[36] Spasticity in the lower extremities, therefore, can be relieved without affecting the upper parts of the body or the brain. Oral doses would need to be a hundred times larger to produce a 10th of the concentration achieved intrathecally.[37]

A further advantage is that intrathecal delivery of baclofen can be individually regulated to allow infusion rates that can vary over a 24-hour period. Thus, clients who find their spasticity helpful in maintaining leg extension for standing and walking can have a lower infusion rate during daytime hours and a higher rate at night to reduce spasms that may disturb sleep. Reports on intrathecally administered baclofen have noted that increased dosage is needed over the first 6 to 12 months as the nervous system develops tolerance to the drug, but generally this difficulty can be overcome by increasing the dosage appropriately.[34]

Baclofen's Effects on Impairments

Impairments are derangements of organs and organ system functions that directly result from the injury or disease process.[27] Most studies of the effects of intrathecally administered baclofen in clients with spasticity have assessed effects at the level of impairment, specifically, effects on abnormal postural tone, including reflexes, spasms, and patterns of muscle activation (synergies), on spasm-induced pain and sleep disturbance, bladder function, and skin integrity. These findings are summarized in the Table. For each reviewed study, information is provided on the numbers of clients, the types of dysfunction represented in each sample, and the outcomes assessed.

[TABULAR DATA OMITTED]

Effects on spasticity, reflexes, and spasms. Coffey and colleagues[6] recently summarized the findings from double-blind, placebo-controlled studies of 75 patients in 15 centers in the United States. Virtually all patients included in these studies experienced decreased spasticity on clinical reflex activity (Ashworth scale[38,39]) assessment or as documented by decreased electromyographic (EMG) activity in response to passive stretch. Those patients who were troubled by spasms in response to tactile stimulation also experienced dramatic relief.

The largest series of cases with the longest follow-up time was summarized by Penn.[34] Among a total of 66 patients with severe spasticity or spasms, or both, and for whom oral antispasticity drug therapy had been ineffective, intrathecally administered baclofen reduced spasms and spasticity in 97% of the patients. One failure was in a patient with lateral sclerosis of 17 years' duration. The other failure occurred in a patient with MS whose spasticity was effectively reduced following infusion of baclofen, revealing severe fixed contractures that presented a contraindication to long-term pump implantation because the drug cannot be expected to alter fixed soft tissue hypoextensibility. Of the 64 responders, 62 elected to receive long-term intrathecally administered baclofen and were followed for an average of 30 months (the first 3 patients were followed for 81 months). At the time of reporting, 52 patients continued to be treated for spasticity and 3 patients had voluntarily discontinued therapy. Two of these patients withdrew because they preferred to have spasticity to aid leg extension for standing. Of the remaining patients, 4 had died of underlying disease and 3 had recurrence of spasms or increased tone after 2 to 3.5 years of successful management. The latter were considered poor long-term responders.

Along with reduced spasticity, clonus and Babinski responses are controlled by baclofen. Decreases in clonus duration, lower amplitude of individual bursts of EMG activity, and increased intervals between bursts have been reported in ankle muscles.[30]

Albright and colleagues[19,20] explored the question of whether upper-extremity, as well as lower-extremity, spasticity could be influenced by lumbar infusion. A short-term study resulted in a report of no effect on upper-extremity reflexes,[19] but in a more recent study of 37 children with CP, reflex response of the arm musculature was reported to be reduced when continuous infusion was used over a period of 3 to 48 months.[20] Although the reason for these different results is unknown, the different effects in the long-term study may indicate that prolonged treatment leads to effects on control of upper-extremity activity through reorganization of spinal circuits over time. Because long-term treatment typically involves changing dosages, use of different dosages may also explain the results.

Effects on spasm-associated sleep impairment and pain. The sleep of clients with SCI and MS is frequently disturbed by spasm. As Kravitz and colleagues[10] note, about 50% of patients with SCI have their most frequent problems with spasm at night. If patients awake, spasms tend to prevent their return to sleep, leading to a secondary sleep impairment. That is, sleep patterns as assessed with electroencephalography are not impaired, but brief periods of arousal that occur normally during sleep are likely to be associated with increased spasm that may lead to awakening and difficulty returning to sleep. Eighty-two percent of those with incomplete lesions and 50% of those with complete lesions have reported interference with sleep, and baclofen has been reported to successfully decrease these spasms and improve sleep continuity.

Patients who experience severe spasms frequently have associated pain, and use of baclofen may bring dramatic relief. In a study using only bolus doses, Herman and colleagues[8] reported that only pain associated with spasms or dysesthetic pain intensity was reduced by baclofen. Their double-blind, placebo-controlled study indicated no change in pinch-induced or musculoskeletal low back pain.

Effects on strength, passive mobility, and active movement Along with reduction of spasticity, some clients have complained of a sensation of decreased strength accompanying baclofen use, although a finding of decreased strength has not been corroborated by muscle testing.[11-13] In most instances, these effects were temporary, but, as Penn[34] noted, they have occasionally been disabling in clients who find spasticity useful in maintaining the upright position. Some patients stop treatment or decline chronic implantation as a result.[34]

Albright and colleagues[19] studied short-term changes in grip strength or timed hand function tests in 20 clients with CP, 2 clients with SCI, and 1 client with mucopolysaccharidosis. No improvement in grip strength was observed. Two patients, however, had reductions in the time required to insert dowels in a board or cubes in a cup. In a more recent report on 37 children with CP who received continuous infusion of baclofen for 3 to 48 months, Albright et al[20] reported effects on both upper-extremity function and hamstring muscle extensibility.

Increased passive mobility has been anecdotally reported following intrathecal introduction of baclofen,[14] but only one other study systematically evaluated the effects on active voluntary movement. A single case was described by Ladish and associates[40] in which a client with TBI increased the peak velocity of voluntary movement twofold (Figure). Associated with improved single-joint movement was decreased antagonist muscle co-activation and irradiation of activation to distant flexor and extensor muscles upon passive and active movement. Presumably, increased velocity was made possible primarily by reduction of restraint from co-acitivated antagonists to the prime mover. Three other clients who also achieved more selective activation of muscle groups had levels of voluntary activation too low to allow for useful function.

These findings, although limited to small numbers of clients, suggest that spasticity reduction can be associated with improved voluntary movement. Presumably, this effect has not been pursued more vigorously by researchers because the vast majority of clients who have used intrathecally administered baclofen have been those with paralysis and little voluntary movement. Such studies are also difficult to conduct and demand extensive time commitments on the part of subjects. As studies continue to expand the investigation of baclofen's effects by including more patients with head injury, CP, and other CNS disorders associated with spasticity and various degrees of voluntary control of movement, it is imperative that protocols include investigation of effects on coordination, speed, and other aspects of movement that could conceivably be affected, either positively or negatively.

Research is needed to carefully distinguish the separate and combined effects of alterations in spasticity, strength, passive range of motion, and patterns of muscle activation on the kinematics and kinetics of voluntary movement. For clients with both upper- and lower-extremity impairment, the effects on use of the arms and hands when lower-extremity spasticity is reduced must be more thoroughly evaluated.

Urologic, cutaneous, and other effects. Several studies[8,9,11,22,41] have documented the effects of baclofen use on bladder function. Improvements have been reported as a result of normalization of bladder pressure, increased bladder capacity, and a decrease in spasms. Reduction in penile erections,[42] often temporary, and increased numbers of bladder infections also have been reported. Other effects include improved skin integrity; one patient, however, experienced an increase in pressure sores that was discovered to be related to the fact that, as a result of newfound ease of mobility, he had driven across the country without taking proper skin precautions.[43] Finally, four clients in a study by Meythaler and associates[12] reported orthostatic hypotension.

In summary, the literature supports the contention that intrathecally administered baclofen is effective in reducing the positive signs of spasticity and other aspects of abnormal postural tone without the disabling central effects that have limited the use of orally administered baclofen. Improvements in sleep continuity, reduced pain, and improved bladder function have been experienced by some patients. The preponderance of the data give extensive support for a trial of intrathecally administered baclofen for clients who find their daily functioning to be impeded by spasms, with or without accompanying pain or sleep disturbance. Effects on strength and control of voluntary movement have been reported, but these outcomes need clarification by further research. Especially needed is study of clients who possess a degree of voluntary movement in the lower extremities but also have upper-extremity involvement as a result of CNS lesions, because effects on arm and trunk control have not been adequately documented and decreased spasticity in the lower extremities could impair arm function if removing it decreases stability in sitting. Certainly therapists working with such clients should assist them in identifying potential for functional improvements. Our clients tell us that they need to relearn how to do some activities as a result of increased mobility, so they should be thoroughly reevaluated to assess this potential. As we describe next, many clients have reported important effects on their daily functioning, but assessment of these outcomes has been largely anecdotal and needs to be supported by analysis at the level of the motor control system (eg, through demonstration of changes in muscle activation patterns).

Baclofen's Effects on Functional Limitations

Functional limitations are problems with activities of the total body or body segments as a result of impairments; they may or may not be permanent, depending on the course or resolution of the inciting process.[27] Changes in functional limitations resulting from use of intrathecally administered baclofen have been reported anecdotally numerous researchers. These changes include positive effects on gait and wheelchair locomotion, stair climbing, and self-care[11,12,20,43]; time required to complete hand function tests[19]; ease and efficiency of positioning, transfers, dressing, and other aspects of caregiving for dependent patients[7,11,18,21,44]; increased sitting time[11,44]; improved mentation and speech in patients with supraspinal lesions[22]; improved sleep continuity[10]; and improved bladder continence or catheter management.[7,9,14,21-23,41,43] Studies that have systematically quantified effects such as these, rather than merely commenting anecdotally on these effects, include those by Albright and colleagues[19,20] previously mentioned and several studies on activities of daily living (ADL), which will now be described.

Effects on activities of daily living.

Loubser and associates[11] studied the effects of intrathecally administered baclofen in nine patients with SCI over a 3- to 22-month period. Eight patients improved in mobility and self-care or reported decreased time and effort of caregivers, or both. Three of the patients increased their sitting time by 1, 2, and 6 hours, respectively. One patient became able to use a power wheelchair and write; another patient became able to use a mouthstick for writing. Finally, one patient was reported to have "discovered motor control in his legs, which had been masked by spasticity," but how this was defined was not described. on the negative side, one client experienced impaired locomotion because of weakness.

Parke and associates[43] used the Patient Evaluation Conference System (PECS) to assess improvements in ADL in four patients with MS and four patients with SCI who were followed for 6 months. In seven patients, PECS scores for performance of bowel and bladder programs improved; four patients achieved independence and one patient removed an indwelling catheter and remained continent. Those patients who were not previously independent in feeding and personal hygiene experienced improved scores in those areas. Six patients had improved PECS scores for dressing skills, and five patients became independent in this activity. One of the patients in this study was the individual shown by Latash and associates[40] to have improved voluntary movement as assessed by kinematics and EMG.

Hugenholtz and associates[9] also studied functional abilities in two patients with MS and four patients with SCI over a 30-day follow-up period after implantation of a baclofen pump. Effects after implantation were statistically analyzed by comparison with placebo, but changes were also classified by clinical meaningfulness. Five patients reported reduction in the effects of spasticity on their ADL using a visual analog scale; effects were rated as clinically meaningful for three of these individuals. Timed dressing and hand function tests did not change meaningfully, but one patient with an indwelling catheter became able to use intermittent catheterization, Finally, a disability index was calculated as a summary of all effects on tone, spasms, strength, bladder function, and ADL. The index changed for all patients with reduction from base-line of about 30% to 40%, but one patient had lessened effects over time. (Unlike most other investigations, doses were kept constant throughout the course of this study.) It is important to note that five of the six patients also demonstrated lesser and statistically significant placebo effects when compared with baseline, emphasizing the importance of performing studies in which both investigators and patients are masked and drug treatments are compared with placebo treatments.

Our informal analysis of the overall results of these studies suggests that about two thirds of patients can be expected to have improved function as a result of their reduced spasticity. Because improved hand function has typically not been found, it seems fair to assume that most of the improvements noted are a result of increased mobility, or ease of mobilization, of the lower extremities along with reduction of spasms that interfere with voluntary movements. For dependent patients, these effects are likely to ease the burden of care for personal assistants or family members.

Baclofen's Effects on Disability in Role Functions

When functional limitations are permanent, disabilities may result. In the NCMRR model, disabilities are defined as difficulties in fulfilling the typical role functions of daily life in the home, school, workplace, and community.[27] None of the studies reviewed have attempted to quantify changes in quality of life or reduction of disability in carrying out life roles in the home and community. Anecdotal reports, however, include the findings that a number of subjects were able to return to work or begin vocational training, or became able to drive independently.[11,12,43] One patient reported increased sexual satisfaction.

Among dependent subjects, only one subject who had been totally bedridden and stuporous was reported to have become fully conscious and able to walk with canes.[22] No other subjects who were dependent on caregivers before the use of intrathecally administered baclofen became independent, but numerous reports indicate that the burden of caregiving was reduced through increased case of transferring, dressing, and otherwise caring for nonambulatory individuals.[11,14,18,21,22,43] Muller and associates[44] reported that two patients became able to sit in a chair and were discharged from institutions, one after 5 years in a nursing home. Finally, one patient achieved greater community mobility when use of portable ventilation was facilitated by spasm reduction.

Delhaas and Verhagen[45] reported a case study of a patient with incomplete C6-7 SCI who decided to become pregnant as a result of the improvement in her condition resulting from use of intrathecally administered baclofen. Baclofen was successfully used to depress spasticity and spasms until the 35th week of gestation. At this point, continuous muscular contractions occurred, with severe autonomic dysreflexia, and an elective cesarean section was followed by the birth of a healthy child. Successful control of spasticity was once again established after delivery. Based on informal analysis of overall results, from 10% to 30% of the subjects in the studies in which quality of life was mentioned appear to have experienced major improvements in access to meaningful personal and community experiences.

Clearly, intrathecally administered baclofen has been demonstrated to reduce impairments in muscle tone and reflexes for the majority of individuals with SCI and MS in these studies. Improved mobility and reduced interference with function by spasms and pain appear to result in significantly improved quality of life for many of these patients. We must go beyond documenting the effects at the level of impairment, however, if we want to further our understanding of the effects of intrathecally administered baclofen on patients with spasticity. Furthermore, the more complex combination of paresis, voluntary movement, and abnormal tone and reflexes demonstrated by individuals with supraspinal lesions may be more difficult to improve without unwanted effects.

For example, one intriguing point concerning intrathecally administered baclofen is the trade-off between strength and voluntary movement mentioned by several patients and by some anecdotal reports. Decreased impairments will not necessarily lead to improvement in function if spasticity is a useful adaptation to disability (eg, by contributing to stability in standing).[5] In this sense, a decrease in strength when baclofen is used may cause further deterioration in functional performance. Although not formally studied, however, our clinical experience suggests that many clients are able to increase their strength over time to overcome this initial effect. Strengthening protocols have not been formally studied as adjuncts to baclofen treatment. We believe that therapists should consider implementing formal programs for clients using baclofen and that research should be done to evaluate the efficacy of these programs in facilitating functional improvements.

From another perspective, decreased muscle tone may allow better movement control. Corcos et al[46] reported that clonus can provoke an actual reversal of direction of a fast voluntary movement as a result of rapid reflex activation in the antagonist muscle. The report by Latash and colleagues[40] showed that the reduction of the positive signals of spasticity can allow the production of an improved pattern of muscle activation and control of voluntary movement. These ideas need further clarification through research because of the great impact their resolution may have on clinical practice. Clarification of the effects of spasticity reduction on voluntary movement in those with some preservation of function can be provided by more studies such as those of Latash and associates.[40]

If clients are able to obtain improved function, the implication is that physical therapy following the introduction of intrathecally administered baclofen might be useful in helping clients to both recognize their newfound abilities and maximize the use of these abilities. Anecdotally, we can report that a child with CP was pleased that he could get off a bench onto the floor more easily, cross his legs during position changes without using his hands, walk without orthoses because of the reduction of clonus during gait, and walk further with less fatigue. Therapists should be aware, however, that these functional gains were not without drawbacks. Without orthoses, ankle plantar flexors tightened slightly. Lack of reduction of hip adductor spasticity (or perhaps walking with hip abductor weakness) caused these muscles to become more hypoextensible over time, which may result in increased risk of hip subluxation and should be monitored. Clients who discard previously used orthoses or have a different balance of spasticity in various joints need careful attention to the possibility of altered forces leading to contracture development. The clinical implications are that therapists should monitor changes in body function and range of motion and assist clients with establishing new goals for function while also warning them about the potential for altered mechanics. The experience of the patient in the study by Parke and colleagues, who developed pressure sores as a result of driving across the country also suggests that clients with impaired sensation need counseling about vigilance in monitoring skin integrity.

To better characterize the overall effects of intrathecally administered baclofen, we must go beyond the impairment dimension and studies that assess movement using single-joint paradigms. More study is needed of effects on functional limitations and disability because it is in these two dimensions that clients face the reality of their impairments. An informal analysis of the summary results across the entire group of research studies we reviewed indicates that about 60% to 70% of clients may expect improved function and that 10% to 30% may experience significant improvements in quality of life through reduction of disability. Of great importance

is quantifying the impact of decreased impairment on the function and disability dimensions so that information from these three dimensions of the disability spectrum can be integrated to deepen our understanding of both the problem of spasticity and the effects of its resolution.

In a subsequent article, we will present a single-case report based on evaluating the effects of intrathecally administered baclofen according to the multiple dimensions of disability. A client with supraspinal causes of spasticity was selected because voluntary movements are better preserved in this population, allowing assessment of the question of the relationship between spasticity, strength, and functional performance. Our goal will be to present a study of a client with CP in which we offer suggestions for structuring research protocols for addressing the multiple dimensions of the disabling process.

References

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SK Campbell, PhD, PT, FAPTA, is Professor and Director of Graduate Studies, Department of Physical Therapy (M/C 898), College of Associated Health Professions, University of Illinois at Chicago, 1919 W Taylor St, 4th Floor, Chicago, IL 60612-7251 (USA). Address all correspondence to Dr Campbell.

GL Almeida, PhD, PT, is Assistant Professor, Instituto de Reabilitacao de Campinas, Universidade Estadual de Campinas, R Dr Quirino, 1856, Campinas, Sao Paulo, Brazil.

RD Penn, MD, is Professor, Neuroscience Institute, Neurosurgery Division, Rush-Presbyterian-St Luke's Medical Center, 1725 W Harrison St, Ste 755, Chicago, IL 60612.

DM Corcos, PhD, is Associate Professor, School of Kinesiology, College of Associated Health Professions, University of Illinois at Chicago, 154 PEB (M/C 194), Chicago, IL 60608- 1516.

At the time this manuscript was written, Dr Corcos was partially supported by Grants K 04-NS 01508 and R 01-NS 28127, National Institutes of Health. Dr Campbell is partially supported by Grant MCJ IL 179590, Maternal and Child Health Bureau, US Public Health Service. Dr Penn's research on intrathecally administered baclofen has been partially supported by Medtronics Inc.