Post Polio Syndrome - Case Study

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Abstract

This article presents a fictional case study which follows a middle-aged man recently diagnosed with post polio syndrome (PPS), referred to physiotherapy from his family physician. This case features an initial physiotherapy assessment highlighting the patient's physical and functional limitations while outlining patient centered goals. It also notes the patient's rehabilitation program and a 6 month follow up to discuss outcomes. During initial assessment, the patient expressed having difficulty standing and ambulating for more than 10 minutes at a time due to right lower extremity weakness, Additional concerns included progressive levels of fatigue and dyspnea. These impairments prevented the patient from enjoying his typical activities with his wife and son that include property maintenance, leisure walks, coaching soccer, and woodworking. The patient also reported a supportive home environment, a high level of anterolateral shoulder pain, and a preference to not use a gait aid at this time. Mild muscular atrophy in the right lower extremity was immediately apparent upon observation, and further testing revealed decreased strength, ROM deficits, and hyporeflexia in the same lower limb. Also noted during observation was an abnormal gait pattern characterized by right foot drop and compensatory clearance related movements. MMT and ROM of the upper extremities were provocative but confirmed impairments in the patient's right shoulder. Self-reported and functional outcome measures supported the patient's claims of unsteadiness and fatigue, classification under higher risk for falls, and indicated that he is experiencing a high level of shoulder related disability. Education focused on lifestyle modification and gait aid use in order to help the patient understand the nature and extent of his condition, as well as support independence and participation. Rehabilitation focused on recovery and maintenance of strength, ROM, and function in the patient's right lower extremity and shoulder. This was achieved through strengthening and stretching programs in conjunction with hydrotherapy in order to limit fatigue and pain during treatment. Finally, aerobic recovery and function was addressed through arm ergometry and graded exercise while taking care not to compound symptoms. Reevaluation of preliminary assessments confirmed that the patient was able to recover strength and function in his lower extremity, as well as his shoulder. The use of a cane and AFO were critical in helping the patient regain balance and mobility throughout the early stages of care. Currently, the patient has graduated from using an AFO and no longer requires a cane for short distances. A continued plan of care is critical in maintaining the patient's condition and as such, the patient will be continuing aquafit weekly, be referred to an occupational therapist, and enrolled in the March of Dimes Canada post-polio support program. Finally, the patient has been discharged from PT caseload, but is encouraged to have follow ups every 3 months to monitor his condition. 

Introduction

This case study aims to aid physiotherapists in understanding the current state of the literature regarding PPS and elucidate potential strategies available in the treatment of this population.

Current experts in the field have developed the March of Dimes diagnostic criteria to assist in identifying the syndrome[1]. This list describes a patient with a history of paralytic poliomyelitis, a period of stable neuromuscular function (typically 15+ years), the gradual onset of new weakness or fatiguability, associated symptomatology that follows a minimal course of one year, and finally the ruling out of alternative explanations for the presentation[1]. Presentation of this syndrome can span neuromuscular, sensory, speech, and respiratory categories of symptoms[1]. Clinical tests focused on motor disability should encompass impairments in strength, endurance, function, tone, gait, and balance whereas non-motor tests should consider quality of life particularly with respect to fatigue, sleep, and psychosocial factors[1].

PPS is grossly underrepresented in scientific literature which translates to a gap in knowledge concerning diagnosis and management[2]. A lack of validated diagnostic and prognostic indicators reinforces the need for highly individualized assessment and rehabilitation approaches that emphasize strategies for lifestyle modification and energy conservation[3].

Client Characteristics

The patient is a 40 year old male substitute teacher who immigrated to Canada, from Nigeria, when he was 25 years old. The patient contracted poliomyelitis when he was 15 years old, and was recently diagnosed with post-polio syndrome by his family doctor. During the period of stability between polio and onset of post-polio syndrome, the patient was healthy and active enjoying spending time outdoors with his wife and son, and woodworking. The patient complains of difficulty staying on his feet and ambulating for an extended period of time due to unsteadiness, right lower extremity weakness and foot drop, as well as worsening fatigue and dyspnea. He also reports several near-falls, but prefers not to use a cane at this time. Additionally, the patient has developed a chronic overuse, compensatory injury in his right shoulder secondary to post-polio syndrome causing a high level of pain. Fortunately, the patient does not report any lower extremity or truncal pain at this time.  Finally, the patient is a heavy smoker and has expressed a desire to quit in order to improve his health. The patient has been referred to physiotherapy from his family doctor to address body structure and function impairments, activity limitations, and participation restrictions.

Examination Findings

Subjective

Pain and Discomfort
Body diagram showing pain localized to right anterolateral shoulder, absent of referral[4]
  • Site: right anterolateral shoulder
  • Onset: gradual, intermittent
  • Character: dull
  • Radiation: remains local
  • Associations: generalized fatigue
  • Timing: worsens throughout the day
  • Exacerbating/Relieving Factors: worsens with activity, particularly with elevation of the right arm and improves with rest
  • Severity: VAS = 6/10 (average), 7/10 (worst), 0/10 (best)

Objective

Observation
Posture:
  • Upper Extremity Alignment (standing) = landmarks are level
  • Pelvic Alignment (standing) = ASIS/PSIS level, Right iliac crest slightly higher vs Left
  • Lower Extremity Alignment (standing) = Right greater trochanter, tibial tuberosity, fibula, lateral malleolus are slightly higher vs Left
  • Spinal Alignment (standing) = slight left lumbar curve
  • Tone: Mild atrophy noted in right lower extremity compared to left lower extremity
Gait analysis:

Overall the patient exhibits a reduced gait speed with a short step length on the right side. It is accompanied by a right foot drop during left leg single limb support, particularly evident from initial swing to the loading response of the right limb. It is followed by a slight compensatory left-sided trunk lean, right pelvic hiking, and circumduction gait of the right hip in order to assist with foot clearance. There is an occasional but infrequent foot slap observed in the right foot between initial contact and loading response. The patient is cognizant of the abnormalities in his gait and the compensatory strategies that he is employing.

Respiratory assessment:

The patient exhibits a largely normal diaphragmatic breathing pattern with some recruitment of apical muscles noted. Auscultation was unremarkable with some reduced breath sounds and fine inspiratory crackles in the lower lobes.

Neurological Testing
  • Dermatomes and sensory testing (superficial and cortical) normal bilaterally
  • Myotomes
    • C4 Shoulder Elevation: Left 5/5, Right 3/5
    • C5 Shoulder Abduction: Left 5/5, Right 2+/5
    • L3 Knee Extension: Left 5/5, Right 3+/5
    • L4 Ankle Dorsiflexion: Left 5/5, Right 3/5
    • All other myotomes normal
  • Reflexes:
    • U/E LMN reflexes: All 2 (normal)
    • L/E LMN (Left): All 2(normal)
    • L/E LMN (Right): Patellar and Achilles Hyporeflexia 1
    • UMN: Negative Babinski and Hoffman's sign
  • Cranial Nerve Testing:
    • Cranial nerve testing revealed no abnormalities
Range of Motion (ROM)
  • Shoulder
    • Flexion = AROM: 95° on Right vs 174° on Left / PROM: 110° on Right vs 180° on Left
    • Abduction = AROM: 80° on Right vs 170° on Left / PROM: 102° on Right vs 176° on Left
    • Extension/Internal Rotation/External Rotation= WNL bilaterally
  • Elbow + Wrist + Hip
    • All Joint ROM = WNL bilaterally
  • Knee
    • Flexion = WNL bilaterally
    • Extension = AROM: -10° on Right vs 0° on Left / PROM: WNL bilaterally
  • Ankle
    • Dorsiflexion = AROM: 5° on Right vs 18° on Left / PROM: WNL bilaterally
    • Plantarflexion/Eversion/Inversion = WNL bilaterally
Manual Muscle Testing (MMT)
  • Shoulder
    • Flexion = 2+/5 on Right vs 5/5 on Left
    • Abduction = 2+/5 on Right vs 5/5 on Left
    • Extension/Internal Rotation/External Rotation= 5/5 bilaterally
  • Elbow + Wrist + Hip
    • All Joint ROM = 5/5 bilaterally
  • Knee
    • Flexion = 5/5 bilaterally
    • Extension = 3+/5 on Right vs 5/5 on Left
  • Ankle
    • Dorsiflexion = 3/5 on Right vs 5/5 on Left
    • Plantarflexion/Eversion/Inversion = 5/5 bilaterally
Special Tests
Self-Reported Outcome Measures
Functional Outcome Measures

Clinical Impression

Physiotherapy Diagnosis

Patient is a 40 year old male with post-polio syndrome experiencing weakness and fatigue in the lower extremities resulting in moderate disability as indicated by an ABC scale score of 40.62%, FSS of 48/63, and TUG score of 18s. This is affecting his ability to stand for long periods of time (>10 mins). Weakness of his right knee extensors is resulting in reduced participation in soccer, gardening, wood-working and driving of his car. He exhibits ambulatory impairments as observed through reduced gait speed (10MWT = 13s), short right step length, right foot drop, and compensatory foot clearance strategies. Overuse of upper extremities resulted in a chronic secondary injury to the right shoulder affecting his ability to work (write on chalkboard). Although the patient has a supportive home environment, living in a rural community proves difficult due to high demands in property maintenance and walking around the large property. The patient is highly motivated but would benefit from education on lifestyle modification and energy conservation strategies as they relate to post-polio syndrome. He is an excellent candidate for physiotherapy.

Problem list

  • Impaired gait as observed through reduced gait speed (10MWT = 13s), short right step length, right foot drop, and compensatory foot clearance strategies
  • Muscle weakness with knee extension (3+/5) and ankle dorsiflexion (3/5)
  • Dyspnea associated with heavy smoking
  • Painful shoulder (VAS = 6/10 on average)
  • Decreased right shoulder range of motion (flexion AROM/PROM = 95°/110°, abduction AROM/PROM = 80°/102°, strength (flexion + abduction = 2+/5), and function (DASH score = 75)
  • Low endurance with standing (can only maintain <10 minutes)
  • Impaired balance and confidence indicating increased falls risk (ABC Scale= 40.62%, TUG score = 18 seconds, overall cautious movement)

Intervention

Short term goals:

  • Be able to stand and do woodworking for 30 minutes by two months into treatment
  • Reduce number of cigarettes smoked from one pack a day, to 6 cigarettes per day within the first two weeks of treatment
  • Fit and teach the use of an Ankle Foot Orthosis (AFO) by the second week of treatment
  • Improve the score on the TUG test by 5 seconds with a cane and/or AFO by the 4th week of treatment
  • Increase strength from 3/5 in the right dorsiflexor to 4/5, and from 3+/5 with the right knee extensor to ⅘ two months into treatment

Long-term goals:

  • Maintain smoking cessation program for at least 1 year
  • Transition patient to the use of a cane for long distance walks >500 meters (as determined by 12 MWT), while decreasing reliance on the use of his AFO by three months after initial treatment
  • Maintain any levels of functional improvement achieved through therapy as determined during 1 year follow up (as measured by the TUG test/ Fatigue severity scale
  • Maintain 4/5 MMT scores for both dorsiflexion and knee extension at the 1 year follow up
  • Abolish or decrease pain to < 2/10 (as measured by VAS) with any right shoulder movement, and improve function (DASH score <10)

Gait Aid Fitting

Our patient has indicated that he would rather not use a cane due to the associated stigma of being perceived as “old”, however, we will need to convince him to use it on a temporary basis to improve his functional abilities by allowing him to walk faster and decrease his risk of falling given his recent perceived instability. Canes have been recommended for PPS to maximize mobility and reduce fatigue[2], especially considering our patient likely experiences a higher cognitive demand for maintaining his balance which likely contributes to his fatigue. Our long-term goal for our patient is to limit the use of the cane only when ambulating longer distances such as for 15 minutes or longer, or in unfamiliar environments with difficult terrain or open environments including navigating around other people in crowded shopping malls 6 months into our physiotherapy treatment. In the short-term, we will encourage the use of the cane as much as possible given the initial weakness of the right knee extensors, right ankle dorsiflexors, and mild balance impairment.

Using an AFO for the first two months of our therapy with our patient will also be important to compensate for his weak ankle dorsiflexion in his right leg. Our goal is to increase strength in his right ankle dorsiflexor from a 3/5 at baseline to 4/5 in two months. Thus, during time in between the AFO will be helpful in compensating and improving gait speed and overall balance by preventing our patient from tripping over his toes[2].

Hydrotherapy

An excellent way to attenuate the effect of fatigue from prolonged standing while allowing increased energy to be focused on performing the stretching, strengthening and aerobic fitness exercises is using water[5]. Water based activities have been shown to decrease fatigue and improve exercise endurance[6]. Furthermore, exercising in warm water is effective at reducing the pain experienced for patients with post-polio syndrome[5][1]. As such, once a week our patient will attend an aquafit session at his local community centre for 20 minutes, with a 5 minute break in the middle of the session to allow time for rest to reduce fatigue. We will reserve time once a week during our PT sessions to discuss how he is tolerating the water based exercise and adjust the work and rest times accordingly. The goal will be to increase the time of aquafit training by 5 minutes each week, eventually reaching a level where our patient can attend an entire aquafit session (typically 50 minutes) with two short breaks during the session by the 6 month follow-up. Our long-term goal is to leave our patient with this activity as a new tool to enable him to maintain his aerobic capacity over his lifespan.

Strength Training

Based on the patient's reported levels of fatigue as well as weakness noted in the right knee extensors and right ankle dorsiflexors,  a measured approach to lower body strengthening should be used in treatment planning. All treatment will take place within a clinic setting, and efforts will be made to have the patient perform these exercises in a context that’s significant to the patient. Evidence suggests that  performing sub-maximal bouts of strength exercises should be done to avoid excessive fatigue in post-polio patients[2][1]. As a result, general guideline parameters for exercise prescription will be kept at lower intensities and at fewer repetitions per set, but more sets. We will begin with isometric knee extension and ankle dorsiflexion (5 secs x 2-3 sets). If well tolerated, treatment will progress  to gravity-eliminated isotonic single limb exercises  including both concentric and eccentric contractions (5-6 reps at 2-3 sets) and eventually working towards functional exercises that will be performed in full weight bearing (that may or may not include the use of an assistive device). Aside from improving levels of strength, the patient’s goals related to participation in being a coach for his son’s soccer team will be important to keep in mind throughout the rehabilitation process. As such, we will incorporate sessions of passing a ball back and forth once a week or as tolerated, beginning with 2 minutes,  increasing weekly by 1 minute, in order to keep our patient engaged and performing activities relevant to his hobbies.

Additionally exercises for right rotator cuff strengthening and range of motion will also be prescribed to address shoulder pain. By strengthening his rotator cuff, we may be able to positively affect limitations to his participation at work as a substitute teacher, as well as with IADLS (i.e. his woodworking hobby). The same stepwise approach to stretching will be taken, beginning with isometric exercises and gradually working towards functional activities (reaching overhead) without pain.

Aerobic Exercise

The specific parameters regarding aerobic exercises are not well documented in the literature and there is conflicting evidence regarding the intensity of aerobic exercise beneficial to PPS patients, though a recent study notes that high-intensity aerobic exercise should be avoided[1]. It has been suggested to perform aerobic training using large muscle groups less affected by the effects of PPS[2], and in the case of our patient his lower limbs are more affected than the upper limbs. Thus, aerobic training may involve the use of  an arm ergometer, modified rowing equipment, or functional exercises that are closely related to his hobby of woodworking. Similarly to the prescribed intensities for his strength training exercises, sub-maximal efforts will be encouraged in an effort to avoid excessive fatigue[2]. Training a muscle group that is involved in ADLs, in the case of our patient his hobby of woodworking, helping put dishes away to overhead cupboards at home, and writing on an overhead board at work in his classroom, will allow him to maintain the training benefits of our aerobic exercises[2]. Effort will be measured using the RPE scale and will target a score of 12/20 as RPE is a reliable measure of intensity[3]. In addition to upper extremity based aerobic activity, we will aim to incorporate a graded walking exercise program to this patient's home exercise routine. A hypothetical starting point  of two 5-minute bouts per day could be prescribed, depending on his tolerance and fatigue. Progress will also be tracked using the 12 MWT to evaluate improvements in aerobic capacity and walking tolerance.  Finally, to address our patient’s functional goal of standing for 30 minutes while woodworking by two months of treatment, we will introduce a graded activity plan that will involve weekly incremental increases in his continue standing time while woodworking in his shed twice a week. He will start with standing for 10 minutes, and adding 2 minutes of standing time every week until he can achieve 30 minutes of standing time.


Education

An important component in establishing our patient’s ability to self-manage his pain and fatigue is to educate him on the nature of post-polio syndrome. We will explain that the condition involves a slow progression of muscle weakness that may be attenuated with regular exercise at non-fatiguing levels, and that avoiding overexertion will be crucial to avoid muscle damage and limit functional disability[2]. Accordingly, we will need to equip our patient with some specific tools to structure his daily life to balance his functional demands and the nature of the PPS. One such tool is pacing, which involves scheduling time for rest throughout the day, and during activities such as prolonged standing or walking[2]. Another method to managing fatigue associated with PPS is alternating activities that involve different muscle groups and energy requirements every 15-20 minutes[2]. This will allow our patient to perform a specific activity without experiencing fatigue, and alternate between the activities, until the required daily tasks are complete[2]. For example, for 15 minutes our patient may stock the shelves in the kitchen with plates from the sink, alternating to performing standing woodworking for another 15 minutes, and for 15 minutes walking around his house and dusting, with a 15 minute break allocated for watching the news on the television. Likewise at work in the school, our patient can structure his lesson by allocating 15 minutes to writing on the board and teaching the class directly, followed by 15 minutes of independent study or working through problems, followed by 15 minutes of student presentations, as an example. Overall, fatigue management through these strategies will be important in limiting functional disability and attenuating the negative effects of PPS.

Outcome

Overall our patient was able to make significant impacts on key indicators including fatigue, levels of pain and disability, and improvements in upper and lower extremity strength.

Using a graded approach for exercise intervention, the patient was able to double his standing tolerance from 10 minutes to 30 minutes after 6 months. Additionally, the walking program increased his overall walking speed as indicated by significant improvements in the Timed Up and Go test (decrease from 18 seconds to 11 seconds, MCID 3.4 seconds[7]. A large part of this success can be attributed to the patient's proficiency in using the prescribed assistive devices, as he was able to graduate from the AFO to using the cane for longer distances  after the first 8 weeks of treatment. To date, the patient now reports not having to rely on the cane when ambulating short distances around the house or when navigating his property. Moreover, his ABC score improved from a 40.62% to a 12%, which is a clinically significant improvement in his balance based on the MCID score of 18.5[8]. Regarding strength improvements, we were able to achieve success in progressing the right knee extensors from 3- to 4/5, and right dorsiflexors  from 3 to ⅘ . The shoulder strengthening interventions were successful in both decreasing reported levels of pain (as noted from a decrease in VAS from 6-2/10) as well as an overall decrease in reported levels of disability in the right shoulder (as noted from a significant decrease in DASH scores from 75 to 10/100, considering the MCID is 10.83[9]. After regularly attending aquafit sessions for 6 months, the patient had reported being able to perform the recommended exercises for 25 minutes before needing to stop for a rest, in addition to reporting decreased levels of fatigue following sessions. He has since stated that he intends to continue participating in weekly aquafit sessions for the remainder of the year. His fatigue severity scale has decreased from a 48 to a 20, which is a clinically significant decrease in this outcome measure as the MCID is 20.2[10].

We will refer our patient to an Occupational Therapist for an assessment of how they may adapt his workplace to enable him to write on the board for longer periods of time, as well as for a home assessment which may involve incorporating additional seating areas such as a stool in his shed to enable him to continue working without having to stand. Furthermore, we recognize that explaining the progressive nature of post-polio syndrome and accepting this difficult reality will be difficult for our patient. As such, we will enrol him in a post-polio syndrome support group ran by the March of Dimes Canada with weekly sessions to ensure that our patient establishes a solid social support network and continues to learn about tools and information to enable him to live his life to an optimal capacity. Based on our patient meeting his treatment goals and achieving safe and independent functional abilities to perform his ADLs and IADLs, we will discharge him from our current intensive physiotherapy treatment consisting of two sessions per week. Given the progressive nature of PPS, we will follow-up with him over the phone monthly for brief status updates and addressing questions, and have in person follow-ups every 3 months to assess the progression of the disease and revise goals and refine his home exercise program to more accurately reflect his functional abilities.

Discussion

In brief, PPS is a long term side effect of a poliomyelitis infection resulting in an absence of reinnervation to compensate for the ongoing denervation, or overall fatigue in the motor unit that took on additional muscle fibers to compensate for the original effects of polio syndrome[11]. Common symptoms include muscle weakness, general fatigue, and pain, as well as the appearance of these symptoms approximately 15 years after an initial polio infection[11].

A 40 year old male with a recent diagnosis of PPS was referred for physiotherapy treatment. A thorough assessment had uncovered issues related to both upper and lower extremity function, presenting as weakness in the right knee extensors as well as in the dorsiflexors of the right ankle, leading to his struggles with walking and standing endurance. Additionally this patient was experiencing compensatory right shoulder pain, which is commonly seen in patients with weak knee extensors[2]. The summation of the above mentioned symptoms had begun negatively impacting activities such as walking short distance, decreased standing tolerance, as well as pain with overhead activities that eventually cascaded down to affect his participation at work as a substitute teacher as well as at home with his woodworking hobby and as a coach for his son’s soccer team. Our treatment approach was multifaceted, not only incorporating interventions for improving strength and function while decreasing levels of pain and disability, but also did well to educate the patient on the nature of the disease, and the importance of prioritizing daily activities so that he may better manage levels of fatigue.

One treatment we employed for our patient with PPS was hydrotherapy which has been found to be effective, especially in warm water to decrease pain which may be applied to conditions such as Guillain Barre or amyotrophic lateral sclerosis (ALS)[12], but not Multiple Sclerosis as warm temperatures may exacerbate fatigue and delays transmission of signals through the demyelinated neurons[13].

PPS is similar to other neuromuscular conditions such as ALS, Guillain Barre syndrome, and multiple sclerosis in terms of a progressive nature. Thus, focusing treatment on delaying and limiting the progression of these conditions and equipping patients with the tools to self-manage the specific impairments associated with each disease should be prioritized as part of any treatment to maintain their participation in life situations and overall quality of life. It is also important to consider the psychological aspect of being diagnosed with a progressive condition which may be difficult to cope with for some individuals, and accordingly encourage this group of patients to participate in support groups to build their social support networks.

Self-study questions

1. List one important outcome measure that measures a PPS related variable in the activity domain of the ICF model.

a. The fatigue severity scale

b. Glasgow coma scale

c. Visual analog scale

d. Activities specific balance scale

2. What should be included with the education component of your treatment for an individual experiencing PPS

a. Rest management strategies (i.e. pacing)

b. Progressive nature of the disease

c. Progression of relapses and remissions of PPS

d. Encouragement to push until muscle failure when performing strength training

e. A and b

3.  Which of the following are necessary components for the diagnosis of PPS based on the March of Dimes diagnostic criteria.

a. history of paralytic poliomyelitis

b. a period of stable neuromuscular function (typically 15+ years)

c. the gradual onset of new weakness or fatiguability, associated symptomatology that follows a minimal course of one year

d. The ruling out of alternative explanations for the presentation

e. All of the above

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Li Hi Shing S, Chipika R, Finegan E, Murray D, Hardiman O, Bede P. Post-polio Syndrome: More Than Just a Lower Motor Neuron Disease. Frontiers in Neurology. 2019;10.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 Lo J, Robinson L. Post-polio syndrome and the late effects of poliomyelitis: Part 2. treatment, management, and prognosis. Muscle & Nerve. 2018;58(6):760-769.
  3. 3.0 3.1 Lo J, Robinson L. Postpolio syndrome and the late effects of poliomyelitis. Part 1. pathogenesis, biomechanical considerations, diagnosis, and investigations. Muscle & Nerve. 2018;58(6):751-759.
  4. Physical Relaxation Techniques [Internet]. Self-guided.com. 2020 [cited 15 May 2020]. Available from: http://www.self-guided.com/physical-relaxation-techniques.html
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  6. Davidson A, Auyeung V, Luff R, Holland M, Hodgkiss A, Weinman J. Prolonged benefit in post-polio syndrome from comprehensive rehabilitation: A pilot study. Disability and Rehabilitation. 2009;31(4):309-317.
  7. Gautschi O, Joswig H, Corniola M, Smoll N, Schaller K, Hildebrandt G et al. Pre- and postoperative correlation of patient-reported outcome measures with standardized Timed Up and Go (TUG) test results in lumbar degenerative disc disease. Acta Neurochirurgica. 2016;158(10):1875-1881.
  8. Beauchamp M, Harrison S, Goldstein R, Brooks D. Interpretability of Change Scores in Measures of Balance in People With COPD. Chest. 2016;149(3):696-703.
  9. Franchignoni F, Vercelli S, Giordano A, Sartorio F, Bravini E, Ferriero G. Minimal Clinically Important Difference of the Disabilities of the Arm, Shoulder and Hand Outcome Measure (DASH) and Its Shortened Version (QuickDASH). Journal of Orthopaedic & Sports Physical Therapy. 2014;44(1):30-39.
  10. Pouchot J, Kherani R, Brant R, Lacaille D, Lehman A, Ensworth S et al. Determination of the minimal clinically important difference for seven fatigue measures in rheumatoid arthritis. Journal of Clinical Epidemiology. 2008;61(7):705-713.
  11. 11.0 11.1 Gonzalez H, Olsson T, Borg K. Management of postpolio syndrome. The Lancet Neurology. 2010;9(6):634-642.
  12. Johnson C. Aquatic Therapy for an ALS Patient. American Journal of Occupational Therapy. 1988;42(2):115-120.
  13. Simmons R, Ponsonby A, van der Mei I, Sheridan P. What affects your MS? Responses to an anonymous, Internet-based epidemiological survey. Multiple Sclerosis Journal. 2004;10(2):202-211.