Dynamic electromyography and muscle biopsy changes in a 4-year follow-up: study of patients with a history of polio

Improving Strength and Fatigue Resistance in Post-Polio Syndrome Individuals with REAC Neurobiological Treatments

Post-Polio Syndrome (PPS) is a chronic condition characterized by the emergence of new symptoms and functional decline in individuals who previously had polio. Despite advances in medical understanding, management of PPS remains challenging. This study aimed to evaluate the use of neurobiological modulation treatments using Radio Electric Asymmetric Conveyer (REAC) technology on fatigue and muscle strength. An open-label study was conducted with 17 patients submitted to four neuromodulation protocols: Neuro Postural Optimization (NPO), Neuro Psycho Physical Optimization (NPPO), Neuro Psycho Physical Optimization-Cervico Brachial (NPPO-CB), and Neuromuscular Optimization (NMO). The Time Up and Go (TUG) test, Handgrip Strength Test, and Revised Piper Fatigue Scale (RPFS) were used to assess participants' fatigue and muscle strength, being applied at the beginning and end of each protocol. The results obtained from the improvement in strength, physical endurance, and particularly the RPFS behavioral dimension, affective dimension, and psychological sensory dimension, through the utilization of REAC neurobiological modulation treatments, highlight this correlation. These results suggest that these treatments could be considered as a potential therapeutic approach for PPS.

Inter-muscular networks of synchronous muscle fiber activation

Skeletal muscles continuously coordinate to facilitate a wide range of movements. Muscle fiber composition and timing of activation account for distinct muscle functions and dynamics necessary to fine tune muscle coordination and generate movements. Here we address the fundamental question of how distinct muscle fiber types dynamically synchronize and integrate as a network across muscles with different functions. We uncover that physiological states are characterized by unique inter-muscular network of muscle fiber cross-frequency interactions with hierarchical organization of distinct sub-networks and modules, and a stratification profile of links strength specific for each state. We establish how this network reorganizes with transition from rest to exercise and fatigue-a complex process where network modules follow distinct phase-space trajectories reflecting their functional role in movements and adaptation to fatigue. This opens a new area of research, Network Physiology of Exercise, leading to novel network-based biomarkers of health, fitness and clinical conditions.

Automatic detection of F-waves and F-MUNE in Two Types of Motor Neuron Diseases

INTRODUCTION/AIMS

Motor unit number estimation by F-waves (F-MUNE) is an uncommonly used MUNE technique. The aim of this study was to analyze the sensitivity of F-MUNE values elicited with newly developed software in motor neuron diseases.

METHODS

F-waves were recorded by 300 submaximal stimuli from abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles of 35 patients with amyotrophic lateral sclerosis, 18 with previous poliomyelitis, and 20 controls. The software extracted the surface motor unit action potentials (sMUAP) and calculated the F-MUNE values. CMAP Scans were also recorded to obtain step% and MScanFit.

RESULTS

sMUAP amplitudes were higher and F-MUNE values were lower in both muscles of the patients than in controls. F-MUNE values were able to distinguish the patients from controls. Significant correlations were found between F-MUNE and MScanFit in patient groups.

DISCUSSION

The new F-MUNE software gave promising results in revealing motor unit loss caused by motor neuron diseases.

How Long does Denervation Take in Poliomyelitis? Or is it a Lifetime?"

Background and Objective:

This study aims to determine the period of reinnervation in patients with poliomyelitis. This research was conducted to identify the appearance of denervation potentials in patients with poliomyelitis as indicators for reinnervation.

Materials and Methods:

A total of 246 male patients with poliomyelitis were assessed electrophysiologically between 1988 and 2007. The mean age was 22.8 (18–42). It has been an average of 19.9 ± 4.9 years since the beginning of complaints from the patients.

Results:

The patients had no complaints of newly developing muscle weakness, fatigue, muscle and joint pain, and difficulties in breathing and swallowing. Neurological examinations revealed the absence of myotomal pain and sensory loss. Upon assessment of the patients’ limbs, the following findings were revealed: two patients had left upper and lower limb involvement, two patients had left upper and right lower limb involvement, 6 patients had left upper limb involvement, 12 patients had both lower limb involvement, 105 patients had left lower limb involvement, 1 patient had both upper limb involvement, 2 patients had right lower and upper limb involvement, 12 patients had right upper limb involvement, 6 patients had both lower limb involvement, 95 patients had right lower limb involvement, and 3 had all the three extremities affected. The needle electromyography revealed the presence of denervation potentials in 25.2% (62) of the patients.

Conclusion:

When poliovirus attacks the motor neuron, this neuron may be completely destroyed, damaged, or unaffected. Reinnervation occurs when nearby functioning motor units send out terminal axon sprouts to reinnervate the damaged muscle fibers. As a consequence of poliomyelitis, several muscle fibers become atrophic and fibrotic, but others continue to survive. This study showed that patients with a history of poliomyelitis experienced denervation with subsequent reinnervation for many years.

A neurophysiological approach to nerve transfer to restore upper limb function in cervical spinal cord injury

A successful nerve transfer surgery can provide a wealth of benefits to a patient with cervical spinal cord injury. The process of surgical decision making ideally uses all pertinent information to produce the best functional outcome. Reliance on clinical examination and imaging studies alone can miss valuable information on the state of spinal cord health. In this regard, neurophysiological evaluation has the potential to effectively gauge the neurological status of even select pools of anterior horn cells and their axons to small nerve branches in question to determine the potential efficacy of their use in a transfer. If available preoperatively, knowledge gained from such an evaluation could significantly alter the reconstructive surgical plan and avoid poor results. The authors describe their institution’s approach to the assessment of patients with cervical spinal cord injury who are being considered for nerve transfer surgery in both the acute and chronic setting and broadly review the neurophysiological techniques used.

Patients with post-polio syndrome are more likely to have subclinical involvement as compared to polio survivors without new symptoms

Background:

Post-polio syndrome (PPS) is a condition that affects polio survivors decades after recovery from an initial acute attack. It is a well-known entity that limbs thought to be nonaffected by polio survivors commonly demonstrate electromyography (EMG) evidence of prior polio. Although the diagnosis of PPS requires a remote history of acute paralytic polio, clinically unapparent damage caused by poliovirus can be associated with PPS later in life.

Objective:

To evaluate EMG abnormalities and late progressive symptoms in limbs thought to be nonaffected by polio survivors, in order to determine the prevalence of subclinical motor neuron involvement in those fulfilling criteria for PPS comparing to those without such symptoms.

Materials and Methods:

Clinical and EMG findings of 464 limbs in 116 polio survivors who had been admitted to our clinic were analyzed. Affection of the limbs by polio was classified based on the patient's self-report on remote weakness during the acute phase of poliomyelitis, muscle strength measured by manual muscle testing, and four-limb needle EMG.

Results:

Seventy-six of the patients (65.5%) met the criteria of PPS. Needle EMG studies revealed subclinical involvement in 122 out of 293 (42%) limbs with no history of remote weakness during the acute phase of poliomyelitis. Prevalence of subclinical involvement was found 47% in polio survivors who met the criteria of PPS compared to 33% in those without PPS (P = 0.013). Among the limbs that had developed new weakness in PPS patients, 33.5% had subclinical involvement.

Discussion and Conclusion:

Subclinical involvement is common in limbs thought to be nonaffected by polio survivors, and this is especially present in those fulfilling criteria for PPS. New muscle weakness may develop in apparently nonaffected, subclinically involved muscles. Thus we believe that four-limb EMG studies should be performed in all polio survivors, especially in those with the symptoms of PPS.

The effects of poliomyelitis on motor unit behavior during repetitive muscle actions: a case report

Background

Acute paralytic poliomyelitis is caused by the poliovirus and usually results in muscle atrophy and weakness occurring in the lower limbs. Indwelling electromyography has been used frequently to investigate the denervation and innervation characteristics of the affected muscle. Recently developed technology allows the decomposition of the raw surface electromyography signals into the firing instances of single motor units. There is limited information regarding this electromyographic decomposition in clinical populations. In addition, regardless of electromyographic methods, no study has examined muscle activation parameters during repetitive muscle actions in polio patients. Therefore, the purpose of this study was to examine the motor unit firing rates and electromyographic amplitude and center frequency of the vastus lateralis during 20 repetitive isometric muscle actions at 50% maximal voluntary contraction in healthy subjects and one patient that acquired acute paralytic poliomyelitis.

Case presentation

One participant that acquired acute type III spinal poliomyelitis (Caucasian male, age = 29 yrs) at 3 months of age and three healthy participants (Caucasian females, age = 19.7 ± 2.1 yrs) participated in this study. The polio participant reported neuromuscular deficiencies as a result of disease in the hips, knees, buttocks, thighs, and lower legs. None of the healthy participants reported any current or ongoing neuromuscular diseases or musculoskeletal injuries.

Conclusion

An acute bout of poliomyelitis altered motor unit behavior, such as, healthy participants displayed greater firing rates than the polio patient. The reduction in motor unit firing rates was likely a fatigue protecting mechanism since denervation via poliomyelitis results in a reduction of motorneurons. In addition, the concurrent changes in motor unit firing rates, electromyography amplitude and frequency for the polio participant would suggest that the entire motorneuron pool was utilized in each contraction unlike for the healthy participants. Finally, healthy participants exhibited changes in all electromyographic parameters during the repetitive muscle actions despite successfully completing all contractions with only a slight reduction in force. Thus, caution is warranted when quantifying muscular fatigue via motor unit firing rates and other electromyographic parameters since the parameters changed despite successful completing of all contractions with only a moderate reduction in strength in healthy subjects.

Examination of motor unit control properties of the vastus lateralis in an individual that had acute paralytic poliomyelitis

The purpose of the study was to examine motor unit (MU) recruitment and derecruitment thresholds and firing rates of the vastus lateralis between 2 healthy (HE) individuals (women, ages = 19 and 23 years) and 1 individual (man, age = 22 years) who acquired acute poliomyelitis (PO). Each participant performed submaximal isometric trapezoid muscle actions of the leg extensors from 20% to 90% maximal voluntary contraction in 10% increments with a sensor placed on the vastus lateralis to record electromyography. Electromyographic signals were decomposed into the firing events of single MUs. Linear regressions were performed on the firing rates at recruitment and peak firing rates versus the recruitment thresholds and the derecruitment versus recruitment thresholds. In addition, data were pooled together from all contractions to examine differences between PO and HE with independent samples t-tests calculated for firing rates at recruitment, peak firing rates, recruitment thresholds, derecruitment thresholds, and duration of MU activity. The results demonstrated systematic differences in MU control strategies between the PO and HE. There were differences in the recruitment thresholds (P < 0.001; HE = 30.5% ± 22.2% maximal voluntary contraction; PO = 14.5% ± 5.0% maximal voluntary contraction), firing rates at recruitment (P < 0.001; HE = 7.4 ± 2.5 pulses per second; PO = 6.2 ± 1.7 pulses per second) and peak firing rates across the force spectrum (P = 0.001; HE = 22.2 ± 5.8 pulses per second; PO = 20.3 ± 2.3 pulses per second), altered derecruitment versus recruitment relationships (HE slope = 0.82 derec/rec, PO slope = 1.78 derec/rec), and duration of MU activity (P < 0.001) between the PO (18.6 ± 2.4 seconds) and HE (15.3 ± 3.0 seconds). Future research should examine the possible differences in MU behavior between PO and HE as a result of fatigue to further elucidate disease-related changes in MU properties.

Single fiber EMG Fiber density and its relationship to Macro EMG amplitude in reinnervation

The objective was to elucidate the relation between the Macro EMG parameters fiber density (FD) and Macro amplitude in reinnervation in the purpose to use the FD parameter as a surrogate marker for reinnervation instead of the Macro amplitude. Macro EMG with FD was performed in 278 prior polio patients. The Biceps Brachii and the Tibialis anterior muscles were investigated. FD was more sensitive for detection of signs of reinnervation but showed lesser degree of abnormality than the Macro amplitude. FD and Macro MUP amplitude showed a non-linear relation with a great variation in FD for given Macro amplitude level. The relatively smaller increase in FD compared to Macro amplitude in addition to the non-linear relationship between the FD and the Macro amplitude regarding reinnervation in prior polio can be due to technical reasons and muscle fiber hypertrophy. The FD parameter has a relation to Macro MUP amplitude but cannot alone be used as a quantitative marker of the degree of reinnervation.

Comparing axonal excitability in past polio to amyotrophic lateral sclerosis

INTRODUCTION

Poliomyelitis causes selective destruction of anterior horn cells and usually has a stable disease course post-infection. We assessed the excitability characteristics in patients with a stable course after past poliomyelitis and compared them with changes described in amyotrophic lateral sclerosis (ALS).

METHODS

The excitability characteristics of motor and sensory nerves were studied in 10 subjects with stable past poliomyelitis.

RESULTS

Motor rheobase was increased, but there were no significant changes in strength-duration properties or depolarizing threshold electrotonus, as have been seen in previous studies of ALS.

CONCLUSIONS

There is minimal change in axonal excitability properties in patients with stable past poliomyelitis. The results may signify sufficient compensation in the stable state of the disease. Increased subexcitability in 1 subject with demonstrable hyperexcitability may represent compensation for increased ectopic activity rather than a different process in surviving motor neurons. Muscle Nerve 50: 602-604, 2014.

Knowledge among physical education professionals about poliomyelitis and post-poliomyelitis syndrome: a cross-sectional study in Brazil

BACKGROUND

Post-poliomyelitis syndrome is a clinical condition that can affect poliomyelitis survivors with the onset of new symptoms several years after the acute disease. These symptoms include new muscular weakness, fatigue, pain, onset or aggravation of muscle atrophy, muscle cramps, onset or aggravation of pre-existing difficulties in accomplishing daily life activities, cold intolerance, sleep disorders, dysphonia or dysphagia, and respiratory deficiency. The treatment of post-poliomyelitis syndrome requires a multiprofessional health team because the rehabilitation procedures include lifestyle changes, physiotherapy, avoidance of secondary complications, and physical exercise. As physical exercise is prescribed by physical education professionals, the assessment of knowledge about post-poliomyelitis syndrome among these professionals is very relevant. The aim of this study was to evaluate poliomyelitis and post-poliomyelitis syndrome knowledge among physical education professionals in Brazil.

METHODS

We invited participants with an academic degree in physical education (n = 217) to participate in this study. A self-administered survey (30 questions) was designed to probe knowledge about poliomyelitis and post-poliomyelitis syndrome. From the survey, we created a questionnaire to evaluate the performance of the professionals. The questionnaire was composed of 20 questions and a score was provided, varying from 0 (totally uninformed) to 20 (well informed).

RESULTS

Approximately 73% of surveyed participants had never heard of post-poliomyelitis syndrome, and only 19.4% had received information about the disease. Among those surveyed, 61.8% did not know whether restriction of physical activities was warranted for people with poliomyelitis sequelae, and only 32.3% knew that physical exercise (especially intense exercise) should be limited for patients with sequelae of paralytic poliomyelitis.

CONCLUSION

The findings of the present study indicate a critical need for improvement of knowledge about post-poliomyelitis syndrome among Brazilian physical education professionals.

Macro electromyography and motor unit number index in the tibialis anterior muscle: differences and similarities in characterizing motor unit properties in prior polio

Our objective was to establish the usefulness of the noninvasive method of the motor unit number index (MUNIX) in a large muscle and to study how macro electromyography (EMG) and MUNIX complement each other in describing the motor units (MUs) in prior polio. MUNIX and macro EMG were performed in 48 tibialis anterior muscles in 33 prior polio patients. In addition, the reproducibility of MUNIX was investigated. It is shown that MUNIX can be used to characterize MUs with high reproducibility, even in a large muscle. As judged by MUNIX values, the patients had a 25% reduction of motor neurons, whereas the macro EMG indicated a loss of 60% of the neurons. Macro EMG showed more pronounced changes compared with control material than the MUNIX. One of the reasons for this finding may be the difference in MU populations studied with the two methods.

Update on current and emerging treatment options for post-polio syndrome

Post-polio syndrome (PPS) refers to the clinical deterioration experienced by many polio survivors several decades after their acute illness. The symptoms are new muscle weakness, decreased muscle endurance, fatigue, muscle pain, joint pain, cold intolerance, and this typical clinical entity is reported from different parts of the world. The pathophysiology behind PPS is not fully understood, but a combination of distal degeneration of enlarged motor units caused by increased metabolic demands and the normal aging process, in addition to inflammatory mechanisms, are thought to be involved. There is no diagnostic test for PPS, and the diagnosis is based on a proper clinical workup where all other possible explanations for the new symptoms are ruled out. The basic principle of management of PPS lies in physical activity, individually tailored training programs, and lifestyle modification. Muscle weakness and muscle pain may be helped with specific training programs, in which training in warm water seems to be particularly helpful. Properly fitted orthoses can improve the biomechanical movement pattern and be energy-saving. Fatigue can be relieved with lifestyle changes, assistive devices, and training programs. Respiratory insufficiency can be controlled with noninvasive respiratory aids including biphasic positive pressure ventilators. Pharmacologic agents like prednisone, amantadine, pyridostigmine, and coenzyme Q10 are of no benefit in PPS. Intravenous immunoglobulin (IVIG) has been tried in three studies, all having positive results. IVIG could probably be a therapeutic alternative, but the potential benefit is modest, and some important questions are still unanswered, in particular to which patients this treatment is useful, the dose, and the therapeutic interval.

EFNS guideline on diagnosis and management of post-polio syndrome. Report of an EFNS task force

Post-polio syndrome (PPS) is characterized by new or increased muscular weakness, atrophy, muscle pain and fatigue several years after acute polio. The aim of the article is to prepare diagnostic criteria for PPS, and to evaluate the existing evidence for therapeutic interventions. The Medline, EMBASE and ISI databases were searched. Consensus in the group was reached after discussion by e-mail. We recommend Halstead's definition of PPS from 1991 as diagnostic criteria. Supervised, aerobic muscular training, both isokinetic and isometric, is a safe and effective way to prevent further decline for patients with moderate weakness (Level B). Muscular training can also improve muscular fatigue, muscle weakness and pain. Training in a warm climate and non-swimming water exercises are particularly useful (Level B). Respiratory muscle training can improve pulmonary function. Recognition of respiratory impairment and early introduction of non-invasive ventilatory aids prevent or delay further respiratory decline and the need for invasive respiratory aid (Level C). Group training, regular follow-up and patient education are useful for the patients' mental status and well-being. Weight loss, adjustment and introduction of properly fitted assistive devices should be considered (good practice points). A small number of controlled studies of potential-specific treatments for PPS have been completed, but no definitive therapeutic effect has been reported for the agents evaluated (pyridostigmine, corticosteroids, amantadine). Future randomized trials should particularly address the treatment of pain, which is commonly reported by PPS patients. There is also a need for studies evaluating the long-term effects of muscular training.

The Course of Functional Status and Muscle Strength in Patients With Late-Onset Sequelae of Poliomyelitis: A Systematic Review

OBJECTIVES

To review systematically studies of late-onset polio sequelae on the course of functional status and muscle strength over time and to identify prognostic factors of change.

DATA SOURCES

We conducted a computerized literature search up to July 2004 in MEDLINE, EMBASE, CINAHL, Web of Science, PsychInfo, and the Cochrane controlled trial register using the key words: postpolio, postpoliomyelitis, postpoliomyelitis syndrome, post poliomyelitis muscular atrophy, and poliomyelitis.

STUDY SELECTION

Reports were selected by 1 reviewer if the study involved subjects with a history of poliomyelitis, the outcome measures described functional status or muscle strength, and follow-up was for at least 6 months.

DATA EXTRACTION

Studies were summarized with regard to population, design, sample size, outcome measures, results, and methodologic scores. Overlap in populations between studies was checked.

DATA SYNTHESIS

Of 71 potentially relevant studies, 19 were included (2 on functional status, 15 on muscle strength, 2 on both muscle strength and functional status). Two studies on the course of functional status had sufficient quality and reported inconsistent results. Four studies on the course of muscle strength had sufficient quality. Two studies reported a decline in strength and 2 reported no change. Decline in strength was only reported in studies with a follow-up period longer than 2 years. One study reported extent of paresis as a prognostic factor for change in perceived physical mobility.

CONCLUSIONS

Conclusions cannot be drawn from the literature with regard to the functional course or prognostic factors in late-onset polio sequelae. The rate of decline in muscle strength is slow, and prognostic factors have not yet been identified. Long-term follow-up studies with unselected study populations and age-matched controls are needed, with specific focus on prognostic factors.

Reproducibility of maximal quadriceps strength and its relationship to maximal voluntary activation in postpoliomyelitis syndrome11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVES

To determine what changes in maximal isometric strength can be detected in a symptomatic quadriceps muscle in patients with postpoliomyelitis syndrome (PPS) and to investigate the association between the variability in maximal strength and maximal voluntary activation (MVA).

DESIGN

Repeated-measures over a 3-week interval.

SETTING

University hospital.

PATIENTS

Convenience sample of 65 patients with PPS.

INTERVENTION

Dynamometer testing.

MAIN OUTCOME MEASURES

Maximal voluntary contraction (MVC) torque of the quadriceps was measured with a Kin-Com dynamometer and MVA was determined by twitch interpolation.

RESULTS

The mean difference between the 2 consecutive measurements was -0.7+/-12.8 Nm (95% confidence interval [CI], -3.9 to 2.5). The test-retest reliability was excellent for MVC torque (intraclass correlation coefficient [ICC]=.96; 95% CI,.93-.98) and moderate for MVA (ICC=.73; 95% CI,.56-.85). The smallest detectable change in MVC torque was 25% for an individual. The variability in MVA explained 18% of the variability in maximal strength.

CONCLUSIONS

Variability in maximal quadriceps strength, measured with a fixed dynamometer, was large and partly related to variability in MVA. This implies that even with optimally standardized strength testing, a follow-up of many years is required to objectify progression of quadriceps weakness in an individual patient with PPS. To demonstrate changes in strength in groups of patients in follow-up or intervention studies, feasible sample sizes are required.

Changes in macro electromyography over time in patients with a history of polio: a comparison of 2 muscles

OBJECTIVE

To investigate whether changes over time are different in a weight-bearing leg muscle than in a less heavily used arm muscle.

DESIGN

Prospective study.

SETTING

University hospital laboratory.

PARTICIPANTS

Twenty-three patients with a history of poliomyelitis.

INTERVENTION

Two investigations were performed 5 years apart, using macro electromyography and the patients' own assessments of symptoms in the tibial anterior and the biceps brachii muscles. Test-retest of macro electromyography was performed in controls and in patients with old polio.

MAIN OUTCOME MEASURES

Macro motor unit potential (MUP) and symptoms in the tibial anterior and biceps brachii over time.

RESULTS

The macro MUP amplitude increased by 24% (P<.05) in the tibial anterior but was unchanged in the biceps brachii muscle.

CONCLUSIONS

An increase in the macro MUP amplitude of the tibial anterior muscle, but not of the biceps brachii, most likely indicates a more pronounced ongoing denervation-reinnervation process over time in the tibial anterior. This difference could be activity dependent, but other factors cannot be excluded.

How to interpret normal electromyographic findings in patients with an alleged history of polio

OBJECTIVE

In some patients with a history of polio, the electromyography is normal, not showing the typical neurogenic signs. The aim of this study was to explain the normal findings in electromyography, especially in paralytic polio.

DESIGN

Retrospective study.

SUBJECTS/METHODS

Concentric needle electromyography, macro electromyography (including single fibre electromyography) and neurography were performed in various combinations in 688 patients with an alleged history of polio.

RESULTS

Thirty-five patients with paralytic polio had normal or minimally abnormal neurophysiology. In 6 patients the diagnosis of polio was rejected and was instead found to be other diagnoses. Three patients had a very atypical history. Of the 26 with possible paralytic polio, 17 showed a strong suspicion of previous paralytic polio without any neurophysiological signs of degeneration of the anterior horn cells.

CONCLUSION

If neurophysiological findings are normal in patients with a history of polio, the original diagnosis may be incorrect. However, the absence of electromyography changes does not entirely exclude a previous history of polio with transient functional loss without degeneration of anterior horn cells vulnerable for later functional impairment.

Lifestyle and late effects after poliomyelitis. A risk factor study of two populations

BACKGROUND

Patients with polio often experience new symptoms (muscle weakness, pain, fatigue and respiratory problems) many years after the acute disease. This study examined possible interactions between lifestyle factors (overweight, physical inactivity, smoking) and late polio with new symptoms.

METHODS

A total of 148 patients hospitalized for acute polio in 1950-1954 at Haukeland University Hospital, Norway and 128 patients, hospitalized for acute polio in 1958 at Tartu University Hospital, Estonia responded to a mailed questionnaire regarding lifestyle and late polio with new symptoms. Multiple regression analysis, two samples t-test and chi-square analysis were undertaken.

RESULTS

Mean body mass index (BMI) and percentage of smokers did not differ in the two cohorts, while polio patients were physically less active in Estonia. The physically active patients in both cohorts had significantly lower odds for experiencing polio-related late muscle pain (OR = 0.21; 95% CI = 0.08-0.55) and fatigue (OR = 0.32; 95% CI = 0.14-0.75). With increasing age the patients had significantly higher odds for experiencing new muscle weakness (OR = 1.03; 95% CI = 1.00-1.07), fatigue (OR = 1.04;95% CI = 1.01-1.07) and breath shortness (OR = 1.04; 95% CI = 1.00-1.07).

CONCLUSION

Physically inactive patients are at a higher risk for late polio-related symptoms. An active lifestyle should be recommended for patients with polio sequels.

Prediction of voluntary activation, strength and endurance of elbow flexors in postpolio patients

To examine the long-term effects of polio, maximal voluntary strength and voluntary activation of elbow flexor muscles of 177 patients from a postpolio clinic were investigated using twitch interpolation. Muscle endurance was studied in 142 patients during 45 min of submaximal exercise, and predictors of impaired muscle performance were investigated. Twenty-nine of 177 patients (16.4%) had impaired voluntary drive to their elbow flexor muscles, but only 16 (9.0%) had markedly reduced elbow flexor strength, despite 74 (41.8%) reporting they were initially affected in their tested limb and 172 (97.2%) patients reporting new generalized symptoms. Seven patients had impaired muscle endurance in the tests of strength and voluntary drive. During the submaximal exercise, 16 patients (11.3%) had impaired peripheral muscle endurance with normal voluntary activation. These results confirm a low incidence of impaired upper-limb muscle performance in postpolio patients, despite many patients having subjective symptoms consistent with postpolio syndrome. There was an increased relative risk for impaired muscle function in those patients with a subjective decrease in strength in the tested limb, a recent decline in activities of daily living in their tested limb, and who used orthotic devices in their tested limb. Monitoring of function in prior-polio patients with impaired muscle performance may be useful, particularly when combined with investigation of other potential contributory factors to the functional impairment.

Perceived health and physical functioning in postpoliomyelitis syndrome: a 6-year prospective follow-up study

OBJECTIVES

To study prospectively the health status, and especially the physical functioning, of polio survivors with and without postpoliomyelitis syndrome (PPS), and to identify prognostic determinants of change in physical functioning.

DESIGN

Prospective cohort study; measurements at baseline and after 1, 2, and 6 years.

SETTING

University hospital in the Netherlands.

PARTICIPANTS

Seventy-six subjects with PPS and 27 without PPS.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The Nottingham Health Profile (NHP) physical mobility category.

RESULTS

Subjects with PPS had significantly poorer health status than subjects without PPS. No significant differences in mean NHP physical mobility scores between baseline and 6 years were found; both groups had improved after 1 year, after which there was a slow decline over the next 5 years. During the first 2 years, strength measurements showed little decline that was not related to changes in NHP physical mobility score. A physical performance test revealed no mean change in the first 2 years, but the subgroup with a decline above the 75th percentile eventually deteriorated 10.5+/-16.3 points on the NHP physical mobility category (P=.01) at 6 years from baseline. This subgroup had more extensive paresis than the other subjects, although it was not significant (P=.07). The extent of paresis at baseline was the only prognostic determinant for an increase in NHP physical mobility problems after 6 years.

CONCLUSIONS

Subjects with and without PPS did not differ with regard to changes in health status in a 6-year period. The fact that the extent of paresis was a prognostic factor for a decline in physical functioning is in accord with a (slow) decline in muscle mass, as a late effect of polio, that may lead to a decline in physical functioning as the reduced muscle capacity becomes less able to meet the demands of daily physical activities.

Macroelectromyography: a review of the technique and its value in the investigation of neuromuscular disorders

The background for the macroelectromyography technique, which was developed by Erik Stålberg to measure the size of motor unit potentials in human muscles, is reviewed. The method employs a modified single-fiber electrode with a large nonselective recording surface capable of recording the activity from all the fibers of a motor unit. The findings in normal subjects and its application in the study of motor unit recruitment are described. The value of the technique in the investigation, diagnosis, and monitoring of various neuromuscular diseases, including primary myopathies and neurogenic conditions, is discussed.

Long-term follow-up of patients with nonparalytic poliomyelitis

OBJECTIVE

To examine patients with previous nonparalytic poliomyelitis in search of muscle atrophy, weakness, and other late symptoms of poliomyelitis.

DESIGN

A mailed questionnaire followed up with neurologic and neurophysiologic examinations of respondents who reported symptoms possibly related to the late sequelae of polio.

SETTING

Neurology department at a university hospital.

PARTICIPANTS

Thirty-nine of 47 patients diagnosed with nonparalytic poliomyelitis and hospitalized at a Norwegian hospital between 1950 and 1954, during the Norwegian polio epidemic.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Electromyography to determine function of the anterior tibialis, vastus lateralis, and biceps brachii muscles; nerve conduction studies of the sural, peroneal, and tibial nerves; motor and sensory nerve conduction velocity, and compound muscle and sensory nerve action potentials, and distal latencies.

RESULTS

Twenty-five of 47 patients (53.2%) reported symptoms possibly related to the late sequelae of poliomyelitis. Eight of 20 examined symptomatic patients had normal neurologic and neurophysiologic findings, whereas 9 others had other medical conditions that could explain the symptoms. Three patients (6.7%) had neurologic and neurophysiologic findings and development of symptoms consistent with motoneuron damage.

CONCLUSION

Some nonparalytic patients may have subclinical acute motoneuron damage with subsequent development and manifestation of motor weakness and neuromuscular symptoms many years later. These symptoms should be considered a differential diagnosis in patients who have a history of nonparalytic poliomyelitis.

Submaximal exercise capacity and maximal power output in polio subjects

OBJECTIVES

To compare the submaximal exercise capacity of polio subjects with postpoliomyelitis syndrome (PPS) and without (non-PPS) with that of healthy control subjects, to investigate the relationship of this capacity with maximal short-term power and quadriceps strength, and to evaluate movement economy.

DESIGN

Cross-sectional survey.

SETTING

University hospital.

PARTICIPANTS

Forty-three polio subjects (25 PPS, 18 non-PPS) and 12 control subjects.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Power output, oxygen uptake, and heart rate were measured in an incremental submaximal cycle ergometry test. Maximal short-term power was measured in 5-second all-out efforts. Knee extensor strength was measured on a chair dynamometer.

RESULTS

The mean submaximal power +/- standard deviation at 80% of heart rate reserve of 83.8 +/- 29.9 watts in the polio subjects was significantly less than the mean submaximal power of 142.1 +/- 30.4 watts in the control group. However, expressed as a percentage of the maximal short-term power, submaximal power did not differ between the groups. Strength and maximal short-term power correlated significantly (p < .005) with submaximal power (r = .64 and .76, respectively). The oxygen uptake was higher than theoretically expected for the given submaximal power output in polio subjects, and appeared to increase with increasing asymmetry in strength and power between legs. No differences were found between PPS and non-PPS subjects.

CONCLUSION

The submaximal work capacity of polio subjects was severely reduced, mainly in association with the reduced muscle capacity. And, because of a reduced movement economy, their energy cost was elevated. Although muscle loads in activities such as walking and climbing stairs differ from cycling, they also may require elevated relative levels of effort, predisposing subjects to premature fatigue in sustained activity.

Varied clinical patterns, physical activities, muscle enzymes, electromyographic and histologic findings in patients with post-polio syndrome in Taiwan

STUDY DESIGN

A study of the clinical features, physical activity, muscle enzyme, electromyography and histopathological alternations of muscles in patients with post-polio syndrome (PPS).

OBJECTIVE

To assess the varied patterns of PPS in Taiwan.

SETTING

Taiwan.

METHODS

Thirty-one patients who fulfill the inclusion criteria of PPS were selected for study. Clinical features, physical activity scale, serum concentrations of creatine kinase, electromyography and histopathological alterations of muscles were assessed and correlated to the causes of PPS patients.

RESULTS

Patients with PPS in Taiwan are relatively young, with a mean age of 39.3 years. Elevated concentration of creatine kinase was found predominantly in male patients with higher physical activities. Electromyographic examinations as well as histological tests of affected muscles revealed prominent evidence of chronic and active denervation with reinnervation in PPS patients.

CONCLUSION

Patients with PPS in Taiwan are young. Thus, PPS should not be attributed to aging. Physical attrition with degradation of nerve terminals is considered the main cause of this disease.

SPONSORSHIP

This study was supported by the National Science Council, Republic of China under grant no. NSC-83-0412-B002-302.

Muscular effects in late polio

New or increased muscular weakness, fatigue and muscle and joint pain with neuropathic electromyography (EMG) changes in a person with a confirmed history of polio constitute the cardinal symptoms of the post-polio syndrome. Unusual tiredness or fatigue is a common complaint in late polio subjects as is intolerance to cold. Fatigue in polio subjects can have several explanations: emotional fatigue, central nervous system fatigue, 'general' fatigue and/or neuromuscular fatigue. Some studies indicate central fatigue, but it is unclear how often and to which degree there will be a central muscular fatigue. Polio patients are known to be deconditioned (reduced function because of low activity level), and aerobic power is reduced. Defects in the neuromuscular transmission may be present but are not seen in all post-polio subjects with reduction in force and increased fatigability. The fatigue experienced by late polio patients is most likely an augmented peripheral muscle fatigue. Possible explanations may be an imperfection in the sarcoplasmatic reticulum with altered calcium release mechanisms (activation) or in sliding filament function (contractile properties). This may be a secondary effect to the enlarged muscle fibres. However, the prolonged subjective feeling of fatigue reported despite unchanged maximal voluntary contraction (MVC) remains unexplained.

Serum insulin-like growth factor-I (IGF-I) does not correlate positively with isometric strength, fatigue, and quality of life in post-polio syndrome

OBJECTIVES AND BACKGROUND

To determine if serum insulin-like growth factor-I (IGF-I) levels are associated with strength, body mass index (BMI), fatigue, or quality of life in post-poliomyelitis syndrome (PPS). PPS is likely due to a distal disintegration of enlarged post-polio motor units as a result of terminal axonal sprouting. Age-related decline in growth hormone and IGF-I (which support terminal axonal sprouts) is proposed as a contributing factor.

METHODS

As part of the North American Post-Poliomyelitis Pyridostigmine Study (NAPPS), baseline data on maximum voluntary isometric contraction (MVIC), BMI, subjective fatigue (fatigue severity scale, Hare fatigue symptom scale), health-related quality of life (short form health survey-36; SF-36), and serum IGF-I levels were gathered on 112 PPS patients. Pearson correlation coefficients were calculated to evaluate the association between serum IGF-I and MVIC in 12 muscles, BMI, two fatigue scales, and SF-36 scale scores.

RESULTS

There is a significant inverse correlation of IGF-I levels with MVIC in left ankle dorsiflexors (r=-0.30, P<0.01), and left and right knee extensors (r=-0.22, -0.25, P=<0.01, 0.01), but no significant correlations in other muscles. When men and women were evaluated separately, inverse correlations of IGF-I levels with MVIC were found only in men. IGF-I correlated inversely with BMI (r=-0.32, P=0006) and age (r=-0.32, P=0.0005). IGF-I did not correlate with the fatigue or SF-36 scales.

CONCLUSIONS

In this exploratory study, we found that contrary to our expectations, IGF-I did not correlate positively with strength. IGF-I correlated negatively with strength in several lower extremity muscles, BMI, and age. IGF-I is likely not an important factor in the pathogenesis of fatigue and in determining quality of life in PPS, but its role on strength should be studied further.

Electrodiagnostic studies in amyotrophic lateral sclerosis and other motor neuron disorders

The clinical electrodiagnostic medicine (EDX) consultant asked to assess patients with suspected amyotrophic lateral sclerosis (ALS) has a number of responsibilities. Among the most important is to provide a clinical assessment in conjunction with the EDX study. The seriousness of the diagnoses and their enormous personal and economic impact require a high-quality EDX study based on a thorough knowledge of and experience with motor neuron diseases (MNDs) and related disorders. Clinical evaluation will help determine which of the EDX tools available to the EDX consultant should be applied in individual patients. Although electromyography (EMG) and nerve conduction study are the most valuable, each of the following may be helpful in the assessment of selected patients based on their clinical findings: repetitive nerve stimulation, motor unit number estimate, single-fiber EMG, somatosensory evoked potential, autonomic function test, and polysomnography. The pertinent literature on these is reviewed in this monograph. The selection and application of these EDX tools depend on a thorough knowledge of the MNDs and related disorders.

Strength assessment in postpolio syndrome: validity of a hand-held dynamometer in detecting change

OBJECTIVES

To investigate the validity, the intraexaminer and interexaminer reproducibility, and the ability to detect change of a hand-held dynamometer (HHD) in strength measurements in former polio subjects.

DESIGN

HHD measurement of knee extensor strength was compared with the criterion standard of a chair dynamometer measurement in 49 subjects. The "break" method was used for HHD measurements. Reproducibility was studied for six lower extremity muscle groups in 28 subjects. The measurements were performed by one experienced and one inexperienced examiner on two separate occasions, with an interval of 1 week. The examiners were blinded to each other's and to previous results.

SETTING

University hospital.

SUBJECTS

Volunteer sample of former polio subjects.

RESULTS

For knee extension, the forces that could be measured with the HHD were limited to approximately 200N. Although the intraclass correlation coefficients were high (.75 to .98), the 95% limits of agreement between measurements showed large intervals for differences between two measurements (ratio intervals ranging from .76-1.52 to .52-2.77). The intraexaminer reproducibility for the experienced examiner was superior to that of the inexperienced examiner. The reproducibility of the inexperienced examiner showed systematic bias, with significantly higher strength values for the second session measurement of three muscle groups.

CONCLUSION

The device has good validity in the lower force range. However, because the agreement between measurements was poor, it has limited ability to detect a change in muscle strength. Therefore, this method is unable to detect small changes in lower extremity muscle strength in former polio patients.

Overexpression of GAP-43 induces prolonged sprouting and causes death of adult motoneurons

In neurodegenerative diseases, neurons undergo prolonged periods of sprouting. Whether this sprouting compromises these neurons is unknown. Here, we examined the effect of axotomy on adult motoneurons undergoing prolonged sprouting in transgenic mice that overexpress GAP-43 (growth-associated protein). Sciatic nerve injury in these adult mice results in motoneuron death, but has no effect in non-transgenic mice. Thus, continued growth of motor axons renders adult motoneurons susceptible to nerve injury and compromises their long-term survival. The progressive nature of neurodegenerative diseases may therefore be caused by prolonged sprouting.

Association of muscle strength and electrophysiological measures of reinnervation in diabetic neuropathy

Motor function was assessed in 34 non-insulin-dependent and 19 insulin-dependent diabetic patients with macroelectromyography and isokinetic dynamometry. Fiber density (FD) and the amplitude of the macro motor unit potential (macro MUP) of the anterior tibial and lateral vastus muscles were obtained and maximal isokinetic strength of the ankle and knee extensors were determined. All patients underwent standardized clinical examination including a neurological disability score (NDS), quantitative sensory examination, and conventional motor nerve conduction studies. The amplitude of the macro MUP and FD of the anterior tibial muscle were increased in neuropathic patients without weakness (P < 0.05) and further increased in neuropathic patients with weakness (P < 0.05). The NDS was related to the FD and the amplitude of the macro MUP for the anterior tibial and lateral vastus muscle [r=0.55-0.75 (P < 0.005)]. Muscle strength of ankle and knee extensors correlated with the FD [r=-0.69 (P < 0.0001) and r=-0.58 (P< 0.001), respectively] and with the amplitude of the macro MUP of the two muscles [r=-0.63 (P < 0.0001) and r=-0.37 (P < 0.05), respectively]. Our findings support the hypothesis that loss of muscle strength in diabetic patients is due to incomplete reinnervation following axonal loss.

An 8-year longitudinal study of muscle strength, muscle fiber size, and dynamic electromyogram in individuals with late polio

Twenty-one subjects with polio 24 to 51 years prior to the first examination were studied on three occasions, each 4 years apart with measurements of muscle strength and endurance for knee extension, macro EMG, and muscle biopsy from vastus lateralis. On average the muscle strength decreased during the 8-year follow-up by 9-15%. Endurance decreased during the observation period. The muscle fiber area was markedly increased in most subjects. There was a decrease in the capillarization during the follow-up. Macro EMG was increased in all subjects (range 3-42 times control) and increased in 20 legs during the 8-year follow-up, but showed a decrease in 8 of 9 legs with an approximative breakpoint when macro MUPs were around 20 times the normal size. Thus, evidence of on-going denervation/reinnervation as well as of failing capacity to maintain large motor units was demonstrated. SFEMG showed a moderate degree of disturbed neuromuscular transmission.

Motor unit size estimation of enlarged motor units with surface electromyography

Surface EMG is hardly used to estimate motor unit (MU) characteristics, while its non-invasiveness is less stressful for patients and allows multi-electrode recordings to investigate different sites of the muscle and MU. The present study compares motor unit potentials (MUPs) obtained with surface EMG and macro EMG during voluntary contraction of the biceps brachii muscle of patients with enlarged MUs caused by prior poliomyelitis. Averaged surface MUPs were obtained by means of needle EMG (SMUP1) and surface EMG (SMUP2) triggering. The MUPs area and peak amplitudes correlated well when comparing the macro MUP and SMUP1 of the same MUs. When MU populations of different patients were compared, the SMUP1s and SMUP2s were equally sensitive to pathology as macro MUPs. In this, the late non-propagating positive wave (only present in unipolar recordings) is more robust than the triphasic propagating wave. Therefore, surface EMG can be used for detecting enlarged MUs.

The role of electromyography in neurology

A review is given of the role of electromyography (EMG) for diagnosis, pathophysiological description and monitoring of patients with disorders of the peripheral nervous system. Various EMG methods are presented and their principal differences are discussed. The usefulness of these methods varies depending on the pathology to be studied. With modern quantitative methods for analysis, EMG has become more sensitive and accurate and is therefore an important part in the evaluation of the neurologic patient. EMG results are usually combined with findings from other neurophysiological investigations (neurography, evoked potentials), histochemistry, biochemistry and most importantly with the clinical signs to give as complete a picture of the condition as possible. The usefulness of EMG depends on a number of factors other than the quality of the investigation as such. These aspects are discussed briefly.

Postpolio muscular dysfunction: relationships between muscle energy metabolism, subjective symptoms, magnetic resonance imaging, electromyography, and muscle strength

Eleven patients with previous polio were studied. The concentration of energy-related metabolites and energy charge was measured from the vastus lateralis muscle, as was isometric muscle strength of knee extension. Cross-sectional area of the quadriceps femoris muscle was calculated from magnetic resonance imaging. Reinnervation was studied using macroelectromyography. Muscle weakness, pain, and newly acquired muscle weakness in the legs was estimated by the patients. The findings in the legs in which the patients experienced new loss of muscle function were compared with the stable legs. There were no significant differences between these groups in any of the objectively measured variables. Only hip pain correlated with new loss of muscle function. Creatine phosphate was decreased in 5 patients. The symptoms and subjective muscle strength did not correlate with any of the objective measurements. There were no significant relationships between energy-related metabolites and postpolio symptoms.

Reduction in thigh muscle cross-sectional area and strength in a 4-year follow-up in late polio

OBJECTIVE

To study changes in cross-sectional thigh muscle area and muscle strength in late polio subjects over a 4-year period.

DESIGN

Longitudinal study of a cohort of polio survivors, comparing subjects who acknowledge (unstable) with those who do not acknowledge (stable) new muscle weakness.

SETTING

University hospital.

SUBJECTS

Eighteen subjects (6 men, 12 women) with polio-myelitis sequelae (39 to 46 years of age) were studied on two occasions 4 years apart; the first examination was 37 to 44 years after onset of polio. Subjects were recruited through hospital registers, newspaper advertisement, and a patient organization.

OUTCOME MEASUREMENTS

Thigh muscle and intermuscular and intramuscular adipose tissue (AT) cross-sectional areas were measured by computed tomography. Isometric muscle strength for knee extension and flexion was measured using a Kin-Com dynamometer.

RESULTS

Cross-sectional muscle area decreased on average 1.3 +/- 3.6 cm2 (1.4%, p < .05); the intermuscular and intramuscular AT area increased 1.8 +/- 3.4 cm2 (12.1%, p < .05). When divided by legs in which subjects reported (unstable) or did not report (unstable) or did not report (stable) increased muscle weakness, unstable legs showed significant reduction (p < .05) in muscle area, whereas stable legs did not. Estimated total thigh muscle strength decreased 7.8% +/- 2.9% (p < .01), with a significant (p < .001) reduction in unstable legs (13.4% +/- 4.3%) but not in stable legs. The reduction in strength appears to be greater than the reduction in cross-sectional muscle area, but there is still a significant correlation (r = .44, p < .05).

CONCLUSION

The present results demonstrate not only progress of muscle weakness, but also of muscle atrophy in postpolio subjects.