Rehabilitation after Spinal Cord Injury: Approaches and Caveats

h1 class=”calibre8″>24 Rehabilitation after Spinal Cord Injury: Approaches and Caveats

George M. Ghobrial and Allan D. Levi

Abstract

Given an increase in the prevalence of acute traumatic cervical spinal cord injury (SCI) in the United States, the need for the development of effective rehabilitation strategies is concomitantly rising. Rehabilitation, however, is a multifaceted process which requires a cogent understanding of the pathophysiology of SCI. It is essential to institute this rehabilitation process expeditiously following the initial trauma to maximize recovery, to improve functional outcomes, and to prevent further deconditioning. Numerous technological advances resulting from increased research and clinical trials into effective rehabilitation strategies, such as the use of epidural stimulation, various cellular replacement therapies, and exoskeletons, have provided clinicians with a wider armamentarium of tools with which to approach the rehabilitation process following acute traumatic cervical SCI. Nonetheless, an optimized rehabilitation program can drastically improve quality of life and can significantly enhance recovery in patients with cervical SCI.

Keywords: spinal cord injury, rehabilitation, clinical trials, quality of life, Charcot arthropathy, syringomyelia, epidural stimulation, exoskeleton, cellular replacement therapy

24.1 Introduction

The development of effective rehabilitative strategies for acute traumatic spinal cord injury (SCI) in the past several decades has been an ongoing pursuit as experimental therapies proposed by physicians and scientists have not demonstrated efficacy in altering the natural disease course. ¹^,² The post-World War II era saw a paradigm shift in rehabilitation led by Munro and Guttmann, who directed all efforts toward the individual’s achievement of independence, obtaining his or her previous standard of living, ³ and integrating sporting activities into rehabilitation. ⁴ Approximately 30 people sustain an SCI in the United States each day, and the likelihood of recovery of functional independence from a complete cervical motor injury, classified as American Spinal Injury Association (ASIA) Impairment Scale Grade A, is very uncommon. ⁵ One rough approximation has been that 10% of patients with cervical ASIA Impairment Scale (AIS) Grade A injuries will improve to an incomplete motor injury (AIS C or AIS D). ⁶ Moreover, because of improvements in the long-term care of patients with SCI and increased long-term survival, the nationwide prevalence of patients with SCI in the United States alone has surpassed 2 million. ⁶ As such, these numbers are estimated to increase, and the relevance and renewed interest of the public in SCI rehabilitation for those with complete and incomplete SCI has steadily grown. Research advances in epidural stimulation, ⁷ cellular replacement therapy, ⁵ and exoskeleton use ⁸^,⁹^,¹⁰^,¹¹ have encouraged novel rehabilitation measures. ⁵ As a clinician, understanding the importance of appropriate rehabilitation for a patient with traumatic cervical SCI is paramount. This aspect of care is likely to have a broader impact on maximizing quality of life (QOL) in the long term. The process of developing curative therapies via clinical trials, meanwhile, will be slow and arduous in comparison.

24.1.1 The Importance of the Postoperative Recovery Period of SCI on Long-Term Quality of Life

The impact of the spinal surgeon on patient QOL extends beyond acute decompression and stabilization of traumatic cervical SCI, and the initial inpatient stay. ¹²^,¹³ These patients tend to score lower on self-reported health-related QOL (HRQOL) surveys. The scores, themselves, are influenced by increasing degrees of disability. ¹⁴^,¹⁵^,¹⁶^,¹⁷ Patients with SCI undergo significant negative changes in body composition characterized by muscle atrophy with fat replacement, increasing the risk for comorbid conditions such as neuropathic pain, depression, obesity, osteoporosis, diabetes, heart disease, and life-threatening pneumonia. ¹⁸^,¹⁹^,²⁰ Physical activity has been shown to reduce cardiovascular disease risk, obesity, diabetes, and osteoporosis in the general public, and increasingly so in patients with SCI. ²¹^,²² These changes in body composition have been demonstrated in several ways. Castro et al performed serial muscle biopsies in adults with complete SCI and found significant increases in fat composition as early as 6 months postinjury. ²³ Less invasively, these results have been similarly confirmed with magnetic resonance imaging (MRI) ²³ and bone densitometry ²⁴ studies. Reversibility of these changes has been demonstrated by noninvasive means with targeted rehabilitative measures tailored for the motor-impaired patient. ¹⁵^,¹⁶^,¹⁷^,²⁵^,²⁶ Therefore, it behooves the spinal surgeon to understand that spinal surgery is just the beginning of a lifetime of increased health care needs and societal expenses for these patients.

Modern clinical trials and investigational studies have been predominantly pharmacological and have focused on mitigating the damaging effects of inflammation on the spinal cord (i.e., limiting the pervasive effects of secondary injury to the volume of at-risk spinal cord tissue). ²⁷ Pharmacologic treatments and clinical trials targeting novel disease mechanisms to cure SCI will be discussed in subsequent chapters.

In this chapter, the rehabilitative care of the SCI patient with acute, cervical, traumatic SCI will be discussed. The focus of this care begins during the transition from the inpatient setting to long-term rehabilitation. It is possible that advances in the rehabilitation of SCI patients may outpace therapies targeting primary and secondary injury, given the greater technological knowledge gap among other numerous hurdles that hamper progress toward enrollment in clinical studies. In the final section of this chapter, the authors discuss several rehabilitative technologies that surgeons may see with increased frequency in the future, such as electrical stimulation and exoskeleton use.

24.2 Initial Assessment, Defining Goals of Rehabilitation, and Maximizing Quality of Life

The general rehabilitation plan is tailored toward the neurologic status of the individual by a physician with a specialization in rehabilitative medicine, a physical therapy team, and an occupational therapist. The goal of this plan is to aid the patient independently, achieve the patient’s activities of daily living (ADLs), achieve reintegration into one’s preinjury occupation, and help develop a plan for the patient to define ADLs and those ADLs requiring assistance. ¹⁴ It is apparent to the health care provider that tetraplegic patients and those with severe cervical SCI will not have similar goals and requirements as the ambulatory cervical SCI patient. It has been increasingly more common for patients in the United States with SCI to be employed preinjury. Hence, the return to work is a major motivational factor for the patient, and can give him or her personal satisfaction, a sense of purpose in society, and an improved QOL. ²⁸ Ferdiana et al evaluated predictors of return to work at 5 years in wheelchair-dependent SCI individuals. ²⁹ The median return to work time was 13 months and was 51% for patients with work rates ≥ 1 hour/week and 43% in patients paid for ≥ 12 hour/week. Intuitively, the most significant return-to-work predictor identified was the level of physical intensity. ²⁹ Wood-Dauphinee and Küchler’s strategy for maximizing well-being is multifaceted. ¹⁴ Ultimately, the patient’s perspective is the most important facet of well-being and is dependent on physical, social, and psychological well-being. The physical component includes all patient-specific ADLs in addition to recreation, sexual functioning, and sleep quality. Social components include, but are not limited to, patient independence, family contacts, role fulfillments, and intimate relationships. Lastly, psychological components include mood, affect, emotional stability, memory, reasoning, and comprehension.

A full physical and detailed neurologic exam should be performed at standardized interim periods with an SCI-specific graded assessment tool such as the “Graded Redefined Assessment of Strength, Sensibility, and Prehension” (GRASSP) ³⁰^,³¹ and the International Standards for Neurological Classification of SCI (ISNCSCI) assessments. ³² Both these tools are helpful for serial assessments when implemented by a trained assessor. The consistent inclusion of GRASSP, ISNCSCI, and any other instruments for measuring SCI rehabilitation progress and the reliability of these assessments are dependent on the availability of trained staff. ³⁰ It is important to understand the accuracy, reliability, and interrater reliability of each test being utilized, so as not to misinterpret small incremental changes in scoring. Moreover, rehabilitation considerations include an assessment of sensory modalities, prehension, range of motion, balance, ambulation and gait, weight-bearing capacity, occupational and domestic needs for carrying out ADLs, and endurance level for each of these activities. Severe SCI limits aerobic and anaerobic conditioning, and a rehabilitation regimen should include cardiovascular as well as strength training for all patients. ³³ Rehabilitation for SCI also requires an understanding of tandem orthopedic injuries in polytrauma that affect ambulation or limb functioning. A training program should take any orthopedic injuries and limitations into account, and they should not be neglected. Traumatic brain injury (TBI) can significantly complicate reintegration of the patient within society and interactions with their care team and family. It is important that this not be overlooked, as concurrent TBI can present in up to 20% of SCI patients and can often be missed. ³⁴ With increases in survival and return to higher standards of living, other issues become more prevalent over time in patients with chronic cervical SCI. These needs must be addressed and given equal importance, and can include musculoskeletal injuries and chronic pain, bowel, bladder, and sexual dysfunction, as well as muscle spasticity requiring surgical intervention. ³⁵

24.3 Therapy Considerations with High Spinal Cord Injury

In the first year after injury, patients with SCI are deconditioned: quadriplegics have a very limited capacity for physical fitness in the first 6 months after SCI. ³⁶^,³⁷ Additionally, patients with high and low cervical injuries have 30 and 60% of their upper body strength relative to paraplegics, respectively. ³⁸ There is a general lack of high-quality, detailed studies on the most efficient or efficacious strength-training or muscle development exercises in the context of SCI. Therefore, the most important step is the early adoption and consistency of a strength-training and aerobic program. Studies by Nilsson et al ³⁹ as well as Davis and Shephard ⁴⁰ have shown both strength and endurance improvements in as little as 8 to 16 weeks. Impairments in normal physiologic responses to exercise including both autonomic and somatic deinnervation affect respiration and respiratory reflexes. Pulmonary capacity has been shown to be diminished as well, observed experimentally by decreased forced vital capacity, forced expiratory volume, and maximal breathing capacity. ⁴¹^,⁴² These measures are also posturally dependent, as demonstrated by Estenne and De Troyer, who found a decrease in vital capacity in tetraplegics when they moved from a seated to supine posture. ⁴³ Work by Noreau and Shephard showed that the maximum oxygen uptake of paraplegics and quadriplegics was 15 and 10 mL/kg/min (VO_2max), respectively. ³⁷ This 50% change in reserve can be accounted for by the lack of sympathetic outflow. Paraplegic individuals can bring their heart rates to 90% of their theoretical maximum. In the context of a cervical injury, peak heart rates reaching only 100 to 120 beats per minute can be achieved. ⁴² Functional electrical stimulation (FES) allows for the transcutaneous stimulation of muscle fibers, promoting muscle fatigue and hypertrophy in patients otherwise unable to voluntarily activate these pathways. ⁴² This is increasingly being recognized as a tool for rehabilitation. With FES, desired upper heart rate ranges can be more easily achieved and maintained in paraplegics, limiting the stress of chronic high-intensity upper extremity cycling and related joint overuse. ⁴⁴^,⁴⁵^,⁴⁶ However, conflicting data show that while FES is helpful, it is still unable to overcome the lack of sympathetic modulation in patients with complete injury above the third thoracic vertebrae. ⁴⁶ The use of FES in pilot studies shows promise, but is early in development. McBain et al demonstrate augmentation of cough muscles during the expiratory phase, raising promise for a future means to prevent aspiration and pneumonia, two major life-threatening conditions affecting patients with chronic cervical SCI. ⁴⁶^,⁴⁷ One more commonly utilized FES implementation is by improving respiratory function through timed stimulation of abdominal muscles, resulting in increased contraction of the rectus muscle and secondary muscles of respiration. ⁴⁸ In one meta-analysis by McCaughey et al, FES was shown to increase respiratory function in a preponderance of the included studies. ⁴⁸ However, these findings are mired by low study quality, with the majority of studies being cohort studies with small sample sizes.

While there are difficulties with demonstrating efficacy of FES for respiratory functional recovery, FES has demonstrated substantial promise for improving recovery for SCI. Sadowsky et al evaluated FES in chronic SCI patients, comparing two cohorts matched by age, gender, and SCI level and severity, finding a significantly greater recovery in the cohort receiving FES cycling. ⁴⁹ In fact, while a composite score consisting of ASIA motor and sensory components was shown to decrease by 9 points in the observational period, there was a 20-point increase (improvement) in the FES cohort. A clinical trial of physical therapy in chronic (>18 months postinjury) ASIA C and D grade SCI patients, with and without FES walking, demonstrated a greater benefit for the FES group. ⁵⁰ Finally, while the quality of many studies in FES in SCI are limited by low enrollment, clear benefits have been shown for stroke rehabilitation where there is clearly a much higher disease prevalence. ⁵¹^,⁵²

24.4 Pain following Traumatic SCI

Numerous sources of chronic pain can limit rehabilitation in patients with SCI. ⁵³ The diagnostic process is often time-consuming and rarely straightforward, due to a multifactorial etiology in the more than 75% of patients with SCI that ultimately seek treatment for chronic pain. ⁵⁴ The earliest type of pain is the most common and least severe type: musculoskeletal. Pain from mechanical instability most commonly occurs after cervical SCI and least commonly in the thoracic and lumbar spine, often presenting in a delayed fashion due to discoligamentous, facet, or bony injuries not surgically addressed in the acute setting. ⁵⁴ This is usually due to traumatic injury in the first 6 months, which resolves, and then is followed by pain that peaks at 5 years and is likely due to orthopedic injury from overuse. ⁵⁵ Orthopedic injuries are common in patients with SCI for several reasons. ⁵⁶ Musculoskeletal pain often results from the recruitment of joints and preserved muscle groups in a compensatory manner that can often exceed the normal tolerances of these joints and musculature. In severe cervical SCI patients, the prevalence of musculoskeletal shoulder pain is high, approaching more than 50%. ³³ In addition to the traumatic injuries inflicted at the onset of SCI, overuse of functioning muscles and joints can result in accelerated arthropathy. ⁵⁷ Joint arthropathy is further accelerated when stabilized by atrophic muscle groups. This is especially the case with muscles lacking antagonist muscle pairs which could ordinarily counterbalance forces during joint movements. Shortening of ligaments, tendons, and atrophic musculature will further contribute to joint arthropathy and pain following SCI. ⁵⁶ In a review of the literature evaluating effective treatments for shoulder pain secondary to chronic wheelchair use, three randomized controlled trials found exercise in the form of arm ergometry, resistive strengthening either with or without electromyographic biofeedback, and routine shoulder girdle stretch exercises to be efficacious therapeutic interventions. ⁵⁶

24.5 Neuropathic Pain, Delayed-Onset Pain, and Cord Lesioning

Aside from early-onset musculoskeletal pain, early “at-level” neuropathic pain is a condition developing within days to weeks of injury and is most frequently described by the patient as severe or excruciating pain. ⁵⁵ This pain is thought to be due to increased hyperactivity of nociceptive afferent C-fibers. The exact cause of posttraumatic neuropathic pain after SCI can often be difficult to isolate, but nonetheless, up to two-thirds of these patients develop chronic neuropathic pain. Sadly, these painful symptoms will persist, and are refractory to oral analgesics. ⁵⁸^,⁵⁹^,⁶⁰ Intrathecal administration, however, has proven to be efficacious in double-blinded, randomized controlled trial of morphine and clonidine for the treatment of neuropathic pain. Intrathecal administration allows the concentration of analgesics to greatly exceed the concentration that can safely be given orally. ⁶¹ Late, “below-level” neuropathic pain occurs both below the level of injury and at a later time point (2 years) after injury. ⁵⁵^,⁶² This type of pain is severe and poorly responsive to pain medications, and is hypothesized to be the result of deafferentation of rostral targets originating from spinothalamic tract projections. ⁶³

Somatic pain refers to pain mediated by the spinothalamic tract. While visceral pain and somatic pain are mediated through discrete spinal cord pathways, visceral pain can be alternatively mediated by the autonomic system. Therefore, given the reliable anatomy of somatic pain mediation, this problem has been amenable to cord lesioning procedures. ⁶⁴ A full discussion of the types of pain and various cord lesioning techniques is beyond the scope of this chapter.

Visceral pain occurs in a very small percentage of the SCI population, occurring relatively late among the types of pain encountered in the context of SCI, and is thought to occur as a result of bowel, bladder, and kidney dysfunction. ⁵⁵ Numerous pain drivers exist and an aggressive workup is important, so as not to delay diagnosis of a serious medical condition. A full physical exam, history, and diagnostic imaging workup should be promptly obtained. Three neurosurgical conditions can present with neuropathic pain, and will be subsequently discussed in this chapter due to the potential for operative intervention including posttraumatic syringomyelia (PTS), neuropathic pain secondary to nerve root avulsion, and Charcot spinal arthropathy. ⁶⁵^,⁶⁶

24.6 Charcot Spinal Arthropathy

Posttraumatic Charcot spinal arthropathy from cervical SCI typically affects the thoracolumbar and lumbosacral spine due to the loss of the protective feedback mechanisms provided by the innervation of the mobile spine. ⁶⁶^,⁶⁷^,⁶⁸^,⁶⁹^,⁷⁰^,⁷¹ Jacobs et al, in a review of 23 patients with a mean age of 43 years, found that the average length of time between SCI and symptomatic presentation of Charcot spinal arthropathy was 20 years. ⁶⁶ In another study by Haus et al, the average duration between SCI and onset of Charcot spinal arthropathy diagnosis was 7.6 years. ⁷² The typical computed tomography (CT) findings are characterized by bony erosion of the vertebral body and posterior elements with reactive bone formation in the facets and adjacent vertebral bodies. Charcot arthropathy of the cervicothoracic spine is exceedingly rare, and limited to small case series. ⁷³