Lack of progression of neurologic deficit in survivors of paralytic polio: a 5-year prospective population-based study

Post-polio syndrome and risk factors in korean polio survivors: a baseline survey by telephone interview

Objective

To obtain information on the socioeconomic, medical, and functional status of polio survivors, and to use these results as the preliminary data for establishing the middle-aged cohort of polio survivors.

Methods

The subjects were recruited based on the medical records of multiple hospitals and centers. They were assessed through a structured questionnaire over the phone. Post-poliomyelitis syndrome (PPS) was identified according to the specified diagnostic criteria. Differences between polio survivors with or without PPS were evaluated, and the risk factors for PPS were analyzed by the odds ratio (OR).

Results

Majority of polio survivors were middle-aged and mean age was 51.2±8.3 years. A total of 188 out of 313 polio survivors met the adopted criteria for PPS based on the symptoms, yielding a prevalence of 61.6%. Mean interval between acute poliomyelitis and the development of PPS was 38.5±11.6 years. Female gender (OR 1.82; confidence interval [CI] 1.09-3.06), the age at onset of poliomyelitis (OR 1.75; CI 1.05-2.94), the use of orthoses or walking aids (OR 2.46; CI 1.44-4.20), and the history of medical treatment for paralysis, pain or gait disturbance (OR 2.62; CI 1.52-4.51) represented independent risk factors for PPS.

Conclusion

We found that the majority of Korean polio survivors entered middle age with many medical, functional, and social problems. Female gender, early age of onset of poliomyelitis, the use of orthoses or walking aids, and the history of medical treatment for paralysis, pain or gait disturbance were identified as the significant risk factors for PPS. A comprehensive and multidisciplinary plan should be prepared to manage polio survivors considering their need for health care services and the risk factors for late effects, such as PPS.

Selective disruption of acetylcholine synthesis in subsets of motor neurons: a new model of late-onset motor neuron disease

Motor neuron diseases are characterized by the selective chronic dysfunction of a subset of motor neurons and the subsequent impairment of neuromuscular function. To reproduce in the mouse these hallmarks of diseases affecting motor neurons, we generated a mouse line in which ~40% of motor neurons in the spinal cord and the brainstem become unable to sustain neuromuscular transmission. These mice were obtained by conditional knockout of the gene encoding choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine. The mutant mice are viable and spontaneously display abnormal phenotypes that worsen with age including hunched back, reduced lifespan, weight loss, as well as striking deficits in muscle strength and motor function. This slowly progressive neuromuscular dysfunction is accompanied by muscle fiber histopathological features characteristic of neurogenic diseases. Unexpectedly, most changes appeared with a 6-month delay relative to the onset of reduction in ChAT levels, suggesting that compensatory mechanisms preserve muscular function for several months and then are overwhelmed. Deterioration of mouse phenotype after ChAT gene disruption is a specific aging process reminiscent of human pathological situations, particularly among survivors of paralytic poliomyelitis. These mutant mice may represent an invaluable tool to determine the sequence of events that follow the loss of function of a motor neuron subset as the disease progresses, and to evaluate therapeutic strategies. They also offer the opportunity to explore fundamental issues of motor neuron biology.

Perinatal characteristics and risk of polio among Swedish twins

Prenatal exposure to adverse environmental conditions is related to increased adult mortality in regions where infections are highly prevalent, yet there is little evidence of the impact of perinatal conditions on the risk of severe infections throughout life. Using prospectively collected data from 21 604 like-sexed Swedish twins of known zygosity born in 1926-1958, we examined the risk of polio in relation to perinatal characteristics using cohort and nested co-twin case-control analyses. Polio incidence was determined through an interview in 1998, and linkage with the Swedish national inpatient and death registries. There were 133 cases of polio. In the cohort analysis, birth length, birthweight and head circumference were positively associated with polio risk. After adjustment for sex, birth year, gestational age at birth and within-twin pair correlations, twins of shortest length (<44 cm) had a 67% ([95% CI: 6%, 88%]; P=0.04) lower risk of polio compared with the reference group (47-49 cm). After additional adjustment for birth length, every 100-g increase in birthweight was related to a 34% increased risk of polio ([95% CI: -1%, 82%]; P=0.06), and every 10-mm increase in head circumference was related to a 17% greater risk of polio ([95% CI: 5%, 31%]; P=0.004). In co-twin control analyses among 226 disease-discordant twins, birth length, birthweight and head circumference were 0.3 cm (P=0.19), 84 g (P=0.07) and 3 mm (P=0.08) higher in cases than controls, respectively. Similar associations were observed among monozygotic (n=84) and dizygotic (n=142) twins. These findings suggest that early intrauterine growth restriction may be inversely related to the incidence of polio.

Prolonged benefit in post-polio syndrome from comprehensive rehabilitation: a pilot study

PURPOSE

To report physical, psychological and functional outcomes from a pilot study of a multi-disciplinary rehabilitation programme for post-polio syndrome (PPS).

METHOD

Twenty-seven participants completed the nine-day programme and were available for re-assessment at three and six months. Physical outcome measures were muscle strength and endurance; psychological outcomes included illness perceptions (IPQ), depression and anxiety (HADS); functional outcomes were fatigue (HFS) and client-centred occupational performance and satisfaction (COPM).

RESULTS

There was no significant change at six months for muscle strength or anxiety. Significant improvements were recorded for exercise endurance, depression and levels of fatigue. A shift towards an endorsement that the patient's own behaviour could be important in symptom severity of PPS was seen. Five out of 24 participants demonstrated significant clinical changes in occupational performance and satisfaction on the COPM.

CONCLUSIONS

Prolonged benefits were found for physical, psychological and functional outcomes. A qualitative study is planned to investigate the patient-reported benefits of attending the programme such as the support gained interacting with others with similar disability and in lifestyle adjustment such as pacing of physical activities.

Perceived disability, fatigue, pain and measured isometric muscle strength in patients with post-polio symptoms

BACKGROUND AND PURPOSE

Several years after the acute polio illness, patients may develop new post-polio symptoms. The purpose of the present study was to evaluate patients with post-polio symptoms with regard to perceived fatigue, functional ability, muscle strength, pain and with regard to measured physical fitness and isometric muscle strength. In addition, the relationship between the results of these subjective and objective measurements was investigated.

METHOD

This was a prospective cross-sectional study in which 32 patients with post-polio symptoms were included. Main outcome measures were the Fatigue Severity Scale (FSS), the Disability Rating Index (DRI), pain intensity, pain distribution, self-reported and measured muscle strength and oxygen uptake.

RESULTS

A marked reduction in isometric muscle strength compared to normal data, high scores in fatigue, widespread pain, low oxygen uptake and difficulties in performing some daily activities were found. Self-reported general muscle strength, pain intensity and pain distribution correlated significantly with patients' perceived fatigue and function at the activity level. There was no significant correlation between self-reported and measured results except for that found between isometric muscle strength in the legs and patients' perceived general muscle strength and oxygen uptake.

CONCLUSIONS

Evaluation of pain intensity, pain distribution, perceived muscle strength, fatigue and ability to perform daily tasks reveals important aspects of health status in patients with post-polio symptoms. Reduction in isometric muscle strength was not reflected in those tests or in reported symptoms, and should be monitored independently using a sensitive assessment tool. Accurate screening of isometric muscle strength in isolated muscle groups contributes to therapeutic management in making a functional diagnosis at the level of body function and structure when designing specific training programmes and in motivating patients. An evaluation combining self-reports with sensitive muscle strength measures provide supplementary information and is appropriate for evaluating these patients in physiotherapy practice.

Electrophysiological findings in a cohort of old polio survivors

A population-based cohort of poliomyelitis survivors was established and followed for 15 years (mean time since polio was 40 years). Over time, the cohort demonstrated a modest decline in summated compound muscle action potential amplitudes (CMAP) and a moderate decline in the summated motor unit number estimates (MUNE). There was no association between symptoms of late deterioration and magnitude of decline. Rather, the presence of these symptoms was associated with the magnitude of the residual deficits. Two patterns of neuron loss were modeled (linear and proportional decline). The summated MUNE was a more sensitive measure of loss of motor units than was the summated CMAP and appears to be a more valid measure of attritional loss of anterior horn cells. Of these two models of neuron loss, the proportional loss of motor neurons was a better fit of the data than a linear loss.

Motor unit number estimates correlate with strength in polio survivors

Motor unit number estimation (MUNE) has been proposed as an outcome measure in clinical trials for the motor neuron diseases. One major criticism of MUNE is that it may not represent a clinically meaningful endpoint. We prospectively studied a cohort of polio survivors over a period of 15 years with respect to MUNE and strength. We identified a significant association between thenar MUNE and arm strength, extensor digitorum brevis MUNE and leg strength, and the summated MUNE and global strength of the polio survivors. These findings confirm the clinical relevance of MUNE as an outcome measure in the motor neuron diseases and provide further validation for its use in clinical trial research.

Prevalence and risk factors of post-polio syndrome in a cohort of polio survivors

OBJECTIVE

To investigate frequency and associated factors of post polio syndrome (PPS) in an Italian cohort of people with prior poliomyelitis.

METHODS

We screened subjects admitted for poliomyelitis at the paediatric hospital of the University of Palermo during the time frame 1945-1960. Patients who developed PPS were identified through a structured questionnaire and a neurologic examination. PPS diagnosis was made according to specified diagnostic criteria. Frequency of PPS was calculated in the selected cohort of polio survivors. The association with the investigated risk factors (sex, age at onset of polio, extension and severity of polio, education, associated diseases, cigarette smoking, trauma, polio vaccination) was analysed by the calculation of the odds ratio.

RESULTS

Forty-eight participants met the adopted diagnostic criteria for PPS, giving a prevalence of 31.0%. The prevalence rate was significantly higher in women than in men (p=0.02). Logistic regression analyses revealed a significant inverse association with onset of poliomyelitis at over 12 months of age (OR 0.33; CI 0.14-0.79) a higher degree of education (OR 0.20; CI 0.07-0.79), and a significant association with the presence of other diseases (OR 9.86; CI 3.69-26.34).

CONCLUSIONS

In our survey one-third of patients with prior poliomyelitis had PPS. Higher age at onset of poliomyelitis is inversely associated with PPS. The association with other diseases may indicate that a chronic physical stress, particularly in already weak motor units, can contribute to the development of signs and symptoms of PPS. Our results also suggest the impact of socio-economic conditions on the risk of PPS.

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.

Postpolio syndrome: a challenge to the health-care system

The practical eradication of poliomyelitis in industrialized countries marks one of the most important achievements of world health policy. Yet, disability induced by polio not only continues to exist among survivors with paralytic sequelae, but may also be further accentuated in a considerable number of affected subjects by the development of postpolio syndrome (PPS). PPS aggravates the motor sequelae already present in such subjects and reduces their functional capacity to the point where it affects their activities of daily living and worsens their quality of life. Inasmuch as development of PPS questions the concept of poliomyelitis as a static disease it poses a challenge not only to health professionals but also to policy-makers tasked with providing the necessary health-care measures and appropriate resources. This study sought to review research on this syndrome and to draw up some recommendations that might prove useful to the health authorities for decision-making purposes.

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.

A comparison of 4 questionnaires to measure fatigue in postpoliomyelitis syndrome

OBJECTIVE

To assess the comparability and reproducibility of 4 questionnaires used to measure fatigue in postpoliomyelitis syndrome (PPS).

DESIGN

Repeated-measures at a 3-week interval.

SETTING

University hospital.

PARTICIPANTS

Convenience sample of 65 patients with PPS.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Fatigue Severity Scale (FSS), the Nottingham Health Profile (NHP) energy category, the Polio Problem List (PPL) fatigue item, and the Dutch Short Fatigue Questionnaire (SFQ).

RESULTS

Correlations of scores between questionnaires were all significant (P<.01) and ranged from.43 (between the NHP energy category and the PPL fatigue item) to.68 (between the PPL fatigue item and the SFQ). Scores on the second visit, normalized to a 0 to 100 scale, were: FSS, 78+/-15; NHP energy category, 47+/-35; PPL fatigue item, 81+/-17; and SFQ, 65+/-22. Except for the difference between the FSS and the PPL fatigue item, the differences in scores between the questionnaires were significant (P<.01). Scale analysis indicated that all questionnaires measured the same unidimensional construct. The reproducibility of the FSS, the PPL fatigue item, and the SFQ was moderate. The smallest detectable change was 1.5 points for the FSS, 2.0 points for the PPL fatigue item, and 1.9 points for the SFQ.

CONCLUSIONS

Although the questionnaires measure the same fatigue construct in PPS, the results are not interchangeable because the ranges of measurement differ. The NHP energy category, in particular, appeared to have a high detection threshold. The moderate reproducibility of the questionnaires indicates a lack of precision, especially when applied at the individual patient level.

Le syndrome post-poliomyélitique

Postpoliomyelitis syndrome is a clinical syndrome characterized by late progression of symptoms, neuromuscular weakness, fatigue and pain, several (more than 20) Years after acute anterior poliomyelitis. In the United States, where it has been mainly described, frequency is estimated between 20 and 30p.100 in patients with sequelae of poliomyelitis. Although the cause is still unknown, postpoliomyelitis syndrome is likely due to degeneration and dysfunction of terminal axons of enlarged post-polio units, with a possible role of inflammatory reaction driven by persistence of the polio virus. Due to lack of specific therapy, rational therapeutic approaches are symptomatic, including exercise, reassurance and life-strategies for fatigue.

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.

Post-polio syndrome and total health status in a prospective hospital study

New loss of function among patients with previous polio is frequently reported and has several causes. All patients referred to the Department of Neurology, Haukeland University Hospital, Bergen, for 13 months during 2000-2001 with diagnosis late effects of polio were examined prospectively to identify their symptoms and loss of function. Eighty-five patients aged 47-91 years with mean of 61 years were included. The most common complaints were pain (44%), muscular weakness (27%), and fatigue (16%). Muscular weakness occurred in lower limbs in 75%, in respiratory muscles in only 5%. Walking in stairs was impaired in 72% and outdoor walking in 65%. Seventeen patients (19%) reported no loss of function. Post-polio syndrome was diagnosed in 26% of the patients. Polio-related loss of function including cervical and lumbosacral radiculopathies, mononeuropathies and degenerative joint disease were found in an additional 53%. Eleven patients (13%) had distinct non-polio-related disorders that caused new loss of function. The remaining 8% had a stable condition. In conclusion, the majority of polio patients who seek hospital, experience a new loss of function because of polio-related disorders. A careful neurological examination is necessary to identify the correct diagnosis and treatment.

Perceived health in a population based sample of victims of the 1956 polio epidemic in the Netherlands

OBJECTIVE

To investigate perceived health and its relation to residual paresis from polio, late onset neuromuscular symptoms following poliomyelitis (LSP), and sex, in a population based sample of polio survivors.

METHODS

350 subjects traced from the notification records of the Dutch 1956 polio epidemic received a mailed questionnaire on residual polio paresis and new neuromuscular symptoms. Perceived health was measured using the Nottingham health profile. Respondents with new muscle weakness and new neuromuscular symptoms were considered as cases with LSP.

RESULTS

Health problems were perceived by 151 of the 260 respondents. Respondents with residual paresis had significantly more health problems than clinically recovered respondents for the Nottingham health profile category of physical mobility. The perceived health of respondents with LSP (45.5%) was significantly worse than that of respondents without LSP for all the health profile categories. Among the respondents with LSP, health status did not differ between those with residual paresis and those who had recovered, except for physical mobility. Female respondents with LSP reported worse health status than male respondents with regard to physical mobility and social isolation.

CONCLUSIONS

In this population based sample, health problems were frequently reported. They were mainly related to late onset neuromuscular symptoms following poliomyelitis, which were perceived by a substantial proportion of all polio survivors-not only subjects with polio residuals but also individuals who (subjectively) had recovered from polio.

Risk of falling: predictors based on reduced strength in persons previously affected by polio

OBJECTIVES

To examine the contributions of sensorimotor factors to postural control and falling in people with prior polio and to determine whether these contributions differ from those found in normal populations.

DESIGN

Survey and case-control study.

SETTING

A falls and balance laboratory in Australia.

PARTICIPANTS

Forty persons with prior polio (age range, 28-71 y) and 38 age- and sex-matched control subjects.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Lower-limb muscle strength, sway, vision, lower-limb sensation, reaction time, foot-tapping speed, and falls.

RESULTS

Compared with the control subjects, the prior polio subjects performed similarly in sensory tests but worse in tests that involved a motor component. Within the prior polio group, lower-limb strength was strongly associated with postural sway on a compliant surface and explained more of the variance in sway than in control subjects. Prior polio subjects who fell multiple times had reduced lower-limb strength, slower reaction time, lower foot-tapping speed, and increased sway compared with those who fell less often. However, the rate of decline in lower-limb strength within the prior polio group did not exceed normal, age-related changes.

CONCLUSIONS

This investigation of prior polio subjects provides an appropriate model for studying muscle weakness as a falls risk factor. Weakness was directly associated with falls, and had an indirect effect mediated through increased sway.

Education, occupation, and perception of health amongst previous polio patients compared to their siblings

Patients with previous polio represent a challenge for neurological rehabilitation. We examined 168 previous polio patients and 239 of their siblings, the patients either from the 1950-1954 epidemic cohort, or from a cohort of hospital-admitted rehabilitation patients. Ninety-four paralytic patients and 74 non-paralytic patients were included. All patients and siblings answered the same questionnaires for socioeconomic and health factors and chi-square comparisons were performed. Previous polio did not affect the level of education. Both patients and siblings rated their educational options to have been good. Significantly less patients were full-time employed at the age of 40 years compared to their siblings (P=0.015). This was the result of a lower full-time employment rate amongst the paralytic patients, only 52% of this group being employed full-time. Male patients and paralytic patients reported to have experienced reduced professional options. More patients were living alone compared to their siblings (P=0.035). The perception of general health was lower amongst patients than siblings, as was assessment of total life situation and patients reported more frequently symptoms like pain and tiredness. In conclusion, previous polio had not lowered the polio patients' educational status, but fewer patients were employed full-time at the age of 40 years.

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.

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.

The postpolio syndrome--a critical comment to the diagnosis

OBJECTIVES

The postpolio syndrome (PPS) is said to comprise symptoms which are characteristic of a specific disorder affecting former polio sufferers many years after their acute disease. Localized muscular weakening with or without attendant pain and atrophy are claimed to separate patients with PPS from persons with unspecific common symptoms from the musculoskeletal system. Therefore our objective was to evaluate the specificity of the symptoms of the PPS.

MATERIAL AND METHODS

Eighty-one former polio sufferers were, based on clinical examination and a questionnaire, compared with 116 gender and age matched controls.

RESULTS

Significant differences between patients and controls of self-reported muscular weakening and pain in different locations were found. However, the level of similar complaints reported by the controls also was considerable.

CONCLUSION

We question the validity of the diagnosis in cases without localized atrophy or other objective signs of denervation.

Disability and functional assessment in former polio patients with and without postpolio syndrome

OBJECTIVES

To compare perceived health problems and disability in former polio subjects with postpolio syndrome (PPS) and those without postpolio syndrome (non-PPS), and to evaluate perceived health problems, disability, physical performance, and muscle strength.

DESIGN

Cross-sectional survey; partially blinded data collection.

SUBJECTS

One hundred three former polio subjects, aged 32 to 60yrs. This volunteer sample came from referrals and patient contacts. Criterion for PPS: new muscle weakness among symptoms.

MAIN OUTCOME MEASURES

Nottingham Health Profile (NHP), adapted D-code of the International Classification of Impairments, Disabilities and Handicaps, performance test, and muscle strength assessment.

RESULTS

PPS subjects (n = 76) showed higher scores (p < .001) than non-PPS subjects (n = 27) within the NHP categories of physical mobility, energy, and pain. On a 16-item Polio Problems List, 78% of PPS subjects selected fatigue as their major problem, followed by walking outdoors (46%) and climbing stairs (41%). The disabilities of PPS subjects were mainly seen in physical and social functioning. No differences in manually tested strength were found between patient groups. PPS subjects needed significantly more time for the performance test than non-PPS subjects and their perceived exertion was higher. Perceived health problems (NHP-PhysMobility) correlated significantly with physical disability (r = .66), performance-time (r = .54), and muscle strength (r = .38). With linear regression analysis, 54% of the NHP-PhysMobility score could be explained by the performance test (time and exertion), presence of PPS, and muscle strength, whereas strength itself explained only 14% of the NHP-PhysMobility score.

CONCLUSIONS

PPS subjects are more prone to fatigue and have more physical mobility problems than non-PPS subjects. In former polio patients, measurements of perceived health problems and performance tests are the most appropriate instruments for functional evaluation.

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.

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.

Electromyographic and neuromuscular variables in unstable postpolio subjects, stable postpolio subjects, and control subjects

OBJECTIVE

To compare strength and endurance variables obtained in the quadriceps muscles of postpolio and control subjects over a 7-year interval with macro and single fiber electromyography (EMG) variables.

DESIGN

A controlled inception cohort study.

SETTING

Neuromuscular research laboratory of a university hospital.

SUBJECTS

A cohort of 23 postpolio and 14 control subjects. All postpolio subjects had a history, physical examination, and EMG consistent with previous poliomyelitis, and had greater than antigravity strength in the quadriceps muscle tested. Unstable postpolio subjects acknowledged new quadriceps weakness over the 7-year period of the study (n = 11), and stable postpolio subjects denied new weakness of the quadriceps over the same period (n = 12).

MAIN OUTCOME MEASURES

All subjects had tests of neuromuscular function of the quadriceps muscles at the onset of this study and yearly over a 7-year period. EMG variables were determined on a separate day after the seventh year of neuromuscular measurements. Neuromuscular variables measured were isometric knee extension peak torque, isometric endurance (time to inability to maintain knee extensor contraction at 40% of maximal torque), tension time index (TTI) (product of isometric endurance time and 40% of maximal torque), and recovery of torque at 10 minutes after the endurance test. EMG variables were macro EMG and single fiber EMG (jitter, fiber density, and percent blocking).

RESULTS AND CONCLUSIONS

Unstable postpolio subjects did not lose strength more rapidly than stable postpolio subjects or control subjects. Unstable postpolio subjects were significantly weaker, had decreased TTI, larger macro EMG amplitude, greater jitter, blocking, and fiber density in comparison with stable postpolio subjects (all p < .05). Strength was negatively correlated with macro EMG amplitude in the stable postpolio group (p < .05). The slope of the regression line of strength over 7 years did not correlate (p > .05) with neuromuscular or EMG variables in control, stable, or unstable postpolio subjects.

Acquired motor neuron disorders

The acquired motor neuron disorders are a heterogeneous group of conditions in which motor neuron degeneration or dysfunction produces the predominant manifestation of weakness, while the sensory system is clinically spared. The disorders most commonly seen in clinical practice are amyotrophic lateral sclerosis, late manifestations of poliomyelitis, and lower motor neuron syndromes, including motor neuropathy. Less often, acquired motor neuron disorders may complicate metabolic, toxic, or systemic disorders. The pathogenesis of most acquired motor neuron disorders is poorly understood, and treatment is mainly supportive; however clues to understanding the pathogenesis of amyotrophic lateral sclerosis are emerging, and new pharmacologic therapies are available. There is a growing sense of hope that combinations of drugs that are currently being tested may impact the survival of amyotrophic lateral sclerosis.

Management of postpolio syndrome

Recent research has shed light on the pathogenesis of the postpolio syndrome and has helped explain its symptoms and the rationale for management. The aim of this article is to familiarize physicians with this syndrome. The history, acute infection, definition, and diagnosis are discussed, as well as the various symptoms and their management. People with postpolio syndrome can educate health professionals about this condition and can help others inflicted with this syndrome. Thus far, no cure is available. A correct diagnosis is important, and the physician must realize that severe comorbidities tend to afflict people with this syndrome. Numerous management options are available to help these people enjoy a high quality of life.