Prevalence and Effect of Obesity on Mobility According to Different Criteria in Polio Survivors

OBJECTIVE

Obesity is a major and functionally important problem in polio survivors. The aim of this study was to investigate the prevalence of obesity using body mass index and percentage body fat in polio survivors and to analyze the relationship between obesity and mobility.

DESIGN

Eighty-four polio survivors were included. Anthropometric parameters, knee extensor strength, and the Short Physical Performance Battery were evaluated. A questionnaire was used to explore the late effects of poliomyelitis. Obesity was determined using both body mass index and percentage body fat.

RESULTS

The prevalence of obesity in polio survivors was 39.3% and 81.5% using the body mass index and percentage body fat criteria, respectively. The Short Physical Performance Battery scores were significantly different between the obese and nonobese groups as determined by percentage body fat (P < 0.05). Only percentage body fat was significantly associated with mobility after controlling for the confounding variables in obese polio survivors (P < 0.05).

CONCLUSIONS

Obesity in polio survivors was underestimated when the body mass index criteria were used. Percentage body fat was a significantly associated factor for mobility in obese polio survivors. Obesity determined by percentage body fat criteria is useful to address obesity-related problems in polio survivors.

"The car is my extra legs" - Experiences of outdoor mobility amongst immigrants in Sweden with late effects of polio

BACKGROUND

The aim of the study was to describe the experience of outdoor mobility among immigrants with late effects of polio living in Sweden. There is a need to understand more about this young group of persons since they often have problems with mobility and gait, but they may also face participation restrictions due to issues associated with integration into a new community and culture.

METHOD

A total of 14 young immigrants with late effects of polio participated and were interviewed individually. The study used a qualitative method to explore personal experiences and the interviews were analyzed through an inductive approach, using qualitative content analysis.

RESULTS

The analysis led to a major theme; self-image and acceptance, that comprised a changeable process and experiences of cultural, social, and gender-specific barriers, but also of environmental and personal factors that impacted their outdoor mobility. By using a car, the participants felt they could come across as normal which also increased their self-esteem.

CONCLUSIONS

Independent mobility is a major enabler for ongoing employment and being able to use a car increases the chances for integration into society for young immigrants with late effects of polio. Public transport is not considered to be adequate or efficient enough due to the participants' mobility impairments, but driving can prevent involuntary isolation and facilitate participation. A car can increase quality of life but may also be a facilitator for work and reduce the demand for societal support.

Gait patterns in association with underlying impairments in polio survivors with calf muscle weakness

The objective was to identify gait patterns in polio survivors with calf muscle weakness and associate them to underlying lower extremity impairments, which are expected to help in the search for an optimal orthosis. Unilaterally affected patients underwent barefoot 3D-gait analyses. Gait pattern clusters were created based on the ankle and knee angle and ankle moment shown in midstance of the affected limb. Impairment clusters were created based on plantarflexor and knee-extensor strength, and ankle and knee joint range-of-motion. The association between gait patterns and underlying impairments were examined descriptively. The Random Forest Algorithm and regression analyses were used to predict gait patterns and parameters. Seven gait patterns in 73 polio survivors were identified, with two dominant patterns: one with a mildly/non-deviant ankle angle, ankle moment and knee angle (n=23), and one with a strongly deviant ankle angle and a mildly/non-deviant ankle moment and knee angle (n=18). Gait pattern prediction from underlying impairments was 49% accurate with best prediction performance for the second dominant gait pattern (sensitivity 78% and positive predictive value 74%). The underlying impairments explained between 20 and 32% of the variance in individual gait parameters. Polio survivors with calf muscle weakness who present a similar impairment profile do not necessarily walk the same. From physical examination alone, the gait pattern nor the individual gait parameters could be accurately predicted. The patient's gait should therefore be measured to help in the prescription and evaluation of orthoses for these patients.

Faster Detection of Poliomyelitis Outbreaks to Support Polio Eradication

As the global eradication of poliomyelitis approaches the final stages, prompt detection of new outbreaks is critical to enable a fast and effective outbreak response. Surveillance relies on reporting of acute flaccid paralysis (AFP) cases and laboratory confirmation through isolation of poliovirus from stool. However, delayed sample collection and testing can delay outbreak detection. We investigated whether weekly testing for clusters of AFP by location and time, using the Kulldorff scan statistic, could provide an early warning for outbreaks in 20 countries. A mixed-effects regression model was used to predict background rates of nonpolio AFP at the district level. In Tajikistan and Congo, testing for AFP clusters would have resulted in an outbreak warning 39 and 11 days, respectively, before official confirmation of large outbreaks. This method has relatively high specificity and could be integrated into the current polio information system to support rapid outbreak response activities.

Characteristics of Patients at First Visit to a Polio Clinic in Sweden

AIM

Describe polio patients visiting a polio clinic in Sweden, a country where vaccination was introduced in 1957.

DESIGN

A consecutive cohort study.

PATIENTS

Prior polio patients.

METHODS

All patients (n = 865) visiting the polio clinic at Sahlgrenska University Hospital, Gothenburg Sweden, between 1994 and 2012 were included in this study. Data at first visit regarding patient characteristics, polio classification, data of electromyography, origin, assistive devices and gait speed as well as muscle strength were collected for these patients. Twenty-three patients were excluded because no polio diagnosis could be established. A total of 842 patients with confirmed polio remained in the study.

RESULTS

More than twenty percent of the patients were from countries outside the Nordic region and considerably younger than those from the Nordic region. The majority of the emigrants were from Asia and Africa followed by Europe (outside the Nordic region). Of all patients included ninety-seven percent (n = 817) had polio in the lower extremity and almost 53% (n = 444) had polio in the upper extremity while 28% (n = 238) had polio in the trunk, according to clinical classification of polio. Compared with a sample of the normal population, the polio patients walked 61-71% slower, and were 53-77% weaker in muscle strength of the knee and foot as well as grip strength.

CONCLUSION

The younger patients with polio emigrating from countries with different cultures may lead to a challenge for the multi professional teams working with post-polio rehabilitation and are of importance when planning for the care of polio patients the coming years.

[Hypotonic syndrome in the newborn infant]

Hypotonia is understood to refer to a pronounced decrease in muscle tone that affects normal motor development and that may affect the axial muscles as well as those of the limbs and, sometimes, the face. It is a very challenging clinical picture because it consists in a fairly wide range of conditions that affect different areas of the central and peripheral nervous system and may be the expression of pathologies that can be either benign or of an uncertain prognosis. These cover myopathies, metabolic disorders, diseases based on genetic causes, pathologies affecting the endocrine glands and progressive or chronic diseases, among other aetiologies. The important development of medicine today has made a number of tools available to the examiner with which to refine or pronounce a diagnosis. Such instruments include the developments achieved in genetic research, together with studies conducted in imaging and optical and electronic microscopy. However, in spite of having all this material available for use, it is still the clinical features that allow a rational use to be made of these advances to be able to point towards the possible causation, topographic location and developmental control. It is useful, for the diagnostic approach and the use of auxiliary methods, to know the topographic location of the disorder, whether it is situated in the brain, the cerebellum, the stem, the spinal cord, the peripheral nerves, the myoneural junction or the muscle.

Lightning can strike twice: an unlucky patient of neurological interest

Poliomyelitis, once a worldwide epidemic, is becoming increasingly rare owing to the introduction of the polio vaccine in the 1950s. It is estimated that the number of cases of polio has reduced by 99% since the Global Polio Eradication Initiative (GPEI) started in 1988. Amyotrophic lateral sclerosis (ALS) is another relatively uncommon condition which also affects anterior horn cells with debilitating neurological, and deadly, consequences. An unusual case of an aggressive form of ALS developing in a 72-year-old patient with paralytic poliomyelitis in childhood is presented. Her initial presentation was puzzling, and our approach to the diagnostic dilemma is discussed.

The meaning of gender while aging with paralytic polio

The purpose of this article is to report the influence of gender on aging with childhood onset paralytic polio. The hermeneutic phenomenological exploration of gender was done using multiple qualitative interviews with 25 women, age 55 to 75 years of age, who had polio since before 14 years of age. We noted three themes: (a) the movement of her body, (b) integrating body and gender, and (c) gender discrepancies. Findings are discussed in the context of gendered expectations and the women's bodies.

Femoral neck bone mineral density in ambulatory men with poliomyelitis

We evaluated bilateral femoral neck bone mineral densities (FNBMDs) in 32 men with poliomyelitis and their matched controls. Men with poliomyelitis had significantly lower FNBMD in both legs, and FNBMD was lowest in their shorter legs. Knee extensor strength and regular exercise were important predictive factors associated with decreased FNBMD.

INTRODUCTION

People with poliomyelitis (polio) are prone to leg fractures after mild trauma. The flaccid paralysis, asymmetric involvement, and underdeveloped growth of afflicted legs may lead to osteoporosis of either leg, characterized by different patterns. This study aimed to measure their femoral FNBMD and to explore the factors associated with changes in FNBMD in either leg.

METHODS

We did a prospective study to evaluate bilateral FNBMD with dual-energy X-ray absorptiometry in 32 men with polio (age range, 41-57 years; mean, 47 years) and 32 age- and body mass index-matched controls. Measuring the difference in leg length, we classified the legs of each polio subject as "longer" or "shorter." In addition, we chose the right leg of each control as a reference leg. We then used the Mann-Whitney U test to compare FNBMD of these three groups of legs and searched for the factors associated with FNBMD using stepwise multiple regression analyses.

RESULTS

Compared to the reference leg, men with polio had significantly lower FNBMD in both their longer and shorter legs, by 13% and 23%, respectively. The difference in FNBMD between the two legs of polio subjects was significant. Knee extensor strength and regular exercise were two important factors associated with bilateral FNBMD in men with polio.

CONCLUSIONS

Men with polio had lower bilateral FNBMD. FNBMD of the shorter leg should be the choice for predicting the risk of hip fracture in men with polio because on average, the shorter leg has lower BMD.

Limited trafficking of a neurotropic virus through inefficient retrograde axonal transport and the type I interferon response

Poliovirus is an enteric virus that rarely invades the human central nervous system (CNS). To identify barriers limiting poliovirus spread from the periphery to CNS, we monitored trafficking of 10 marked viruses. After oral inoculation of susceptible mice, poliovirus was present in peripheral neurons, including vagus and sciatic nerves. To model viral trafficking in peripheral neurons, we intramuscularly injected mice with poliovirus, which follows a muscle-sciatic nerve-spinal cord-brain route. Only 20% of the poliovirus population successfully moved from muscle to brain, and three barriers limiting viral trafficking were identified. First, using light-sensitive viruses, we found limited viral replication in peripheral neurons. Second, retrograde axonal transport of poliovirus in peripheral neurons was inefficient; however, the efficiency was increased upon muscle damage, which also increased the transport efficiency of a non-viral neural tracer, wheat germ agglutinin. Third, using susceptible interferon (IFN) alpha/beta receptor knockout mice, we demonstrated that the IFN response limited viral movement from the periphery to the brain. Surprisingly, the retrograde axonal transport barrier was equivalent in strength to the IFN barrier. Illustrating the importance of barriers created by the IFN response and inefficient axonal transport, IFN alpha/beta receptor knockout mice with muscle damage permitted 80% of the viral population to access the brain, and succumbed to disease three times faster than mice with intact barriers. These results suggest that multiple separate barriers limit poliovirus trafficking from peripheral neurons to the CNS, possibly explaining the rare incidence of paralytic poliomyelitis. This study identifies inefficient axonal transport as a substantial barrier to poliovirus trafficking in peripheral neurons, which may limit CNS access for other viruses.

Premature pubarche and the growth of the trunk in paralysed children

In a hospital supervising prolonged orthopaedic treatment of children suffering from neurological affections, isolated premature pubarche appeared very frequently in children suffering from severe paralytic sequelae of acute anterior poliomyelitis. These subjects had a greater progression of scoliosis and segmental disproportion than comparable subjects of the same age. Supine length and crown-rump length were studied during growth in 16 paralysed boys and 22 paralysed girls with premature pubarche. The results were compared with those of two control populations, one normal group (274 girls, 246 boys), the other a paralysed group (49 boys and 38 girls). Paralysed children (group with premature pubarche and control group) all show considerable shortening of the legs. Up to age 11 for girls and 13 for boys, children with premature pubarche had longer trunks than normal, while supine length was normal. Premature slowing of growth then occurred, bringing the trunk to normal values and supine length to very low values for age. This is ascribed to premature pubertal growth of the trunk. The roles of hormonal changes and neurological damage are discussed.

Change in lower limb isokinetic muscle strength of polio survivors over 5-year follow-up

To evaluate the muscle strength of the lower limbs over time in polio survivors during 5 years of follow-up and to examine the rate of change in their muscle strength, we performed a prospective, longitudinal study of polio survivors (n = 63: 61 with postpolio syndrome) living in the community who participated voluntarily. Their isokinetic knee-extensor and knee-flexor muscle strength (peak torque) at angular velocities of 60 and 120 deg/sec, using a fixed dynamometer (Biodex) were measured over a 5-year period. At 5-year follow-up, approximately 90% of the subjects had decreased knee extensor strength at both angular velocity of 60 and 120 deg/sec: similarly, at both angular velocities, approximately 80% of the subjects had decreased knee flexor strength. The annual average rate of decrease in the peak torque of the knee extensors was significantly greater than that of the flexors at both angular velocities, and the difference in the rates between the extensors and the flexors was marked at the faster angular velocity. The polio survivors had a progressive decrease in lower limb isokinetic muscle strength over time. In addition, the annual rate of decrease of the knee-extensor, the so-called weight bearing muscle, was greater than that of the knee-flexor.

A method to measure the accuracy of loads in knee-ankle-foot orthoses using conventional gait analysis, applied to persons with poliomyelitis

OBJECTIVES

To determine (1) the forces and moments passing through knee-ankle-foot orthoses (KAFOs) during walking and (2) the accuracy with which these loads can be measured using conventional gait analysis techniques.

DESIGN

Comparative case series.

SETTING

Rehabilitation facility with human movement laboratory (gait lab).

PARTICIPANTS

Four patients with poliomyelitis wearing KAFOs.

INTERVENTIONS

KAFOs were instrumented with a load cell, and walking data were concurrently collected using conventional gait analysis.

MAIN OUTCOME MEASURES

Load measurements and gait parameters.

RESULTS

Predominant orthotic loads (knee joint forces and moments) were composed of knee flexion moments and axial compression forces. With conventional gait analysis, peak knee joint moments were substantially underestimated compared with those directly measured using the load cell. Defining the knee axis anatomically versus at the orthotic axis, tracking it dynamically, and compensating for each patient's corrected knee flexion contracture resulted in considerable improvements in the gait lab estimates of knee joint moments.

CONCLUSIONS

A practical method that directly measures moments and forces in conventional KAFOs has been applied to show that conventional gait analysis techniques substantially underestimate knee joint moments in the KAFOs of persons with poliomyelitis. Underestimation of orthotic loads could result in underdesigned orthotic components and ultimately higher incidence of component failure in clinical applications.

TGF-beta1 suppresses T cell infiltration and VP2 puff B mutation enhances apoptosis in acute polioencephalitis induced by Theiler's virus

GDVII and DA strains of Theiler's murine encephalomyelitis virus (TMEV) differ in VP2 puff B. One week after GDVII virus infection, SJL/J mice had large numbers of TUNEL+ apoptotic cells with a relative lack of T cell infiltration in the brain. DA viruses with mutation in puff B induced higher levels of apoptosis than wild-type DA virus, but levels of inflammation in brains were similar between DA and DA virus mutants. The difference in inflammation among TMEVs could be due to TGF-beta1 expression that was seen only in GDVII virus infection and negatively correlated with CD3+ T cell infiltration.

Polio's painful legacy

Some of the people who contracted polio in the 1950s epidemic are now experiencing new symptoms. Yet post-polio syndrome (PPS) is often not recognised.

Characterization of early steps in the poliovirus infection process: receptor-decorated liposomes induce conversion of the virus to membrane-anchored entry-intermediate particles

The mechanism by which poliovirus infects the cell has been characterized by a combination of biochemical and structural studies, leading to a working model for cell entry. Upon receptor binding at physiological temperature, native virus (160S) undergoes a conformational change to a 135S particle from which VP4 and the N terminus of VP1 are externalized. These components interact with the membrane and are proposed to form a membrane pore. An additional conformational change in the particle is accompanied by release of the infectious viral RNA genome from the particle and its delivery, presumably through the membrane pore into the cytoplasm, leaving behind an empty 80S particle. In this report, we describe the generation of a receptor-decorated liposome system, comprising nickel-chelating nitrilotriacetic acid (NTA) liposomes and His-tagged poliovirus receptor, and its use in characterizing the early events in poliovirus infection. Receptor-decorated liposomes were able to capture virus and induce a temperature-dependent virus conversion to the 135S particle. Upon conversion, 135S particles became tethered to the liposome independently of receptor by a membrane interaction with the N terminus of VP1. Converted particles had lost VP4, which partitioned with the membrane. The development of a simple model membrane system provides a novel tool for studying poliovirus entry. The liposome system bridges the gap between previous studies using either soluble receptor or whole cells and offers a flexible template which can be extrapolated to electron microscopy experiments that analyze the structural biology of nonenveloped virus entry.

Life purpose: effect on functional decline and quality of life in polio survivors

This article explores the protective effects that finding a purpose in life has on the level of physical and mental impairment and overall quality of life. Results were gathered from a national sample of 2,153 polio survivors. Although the combined social and physical experience of living with the disabling effects of polio has been associated with accelerated aging due to an increased allostatic load, finding a purpose in life may diminish these effects. The findings of this study indicate that purpose in life is associated with less perceived decline in health. Moreover, purpose in life is predictive of better quality of life despite levels of physical and mental impairment. Rehabilitation nurses should consider ways to help persons with polio maintain activities and interests that promote their sense of purpose in life.

Clinical presentations of acute paralytic poliomyelitis

The concern about the emerging profile of poliovirus associated morbidity and mortality in the 21st century is legitimate [Paul Y. Clinical presentations of acute paralytic poliomyelitis. Vaccine 2005;23:5283]. Rather than case reports of several thousands, patients number at the most in few thousands. Furthermore, better diagnostic techniques have been offered to those handling patients with clinical syndromes resembling acute flaccid paralysis. Bizarre and unconventional clinical presentations might well be a rule than exception in near future. Furthermore, MRI can be used in the diagnosis of anterior horn infection and would play an important role in diagnosis of poliomyelitis [Kornreich L, Dagan O, Grunebaum M. MRI in acute poliomyelitis. Neuroradiology 1996;38(4):371-2]. Imaging techniques would be important in diagnosis of acute flaccid paralysis.

Age-dependent poliovirus replication in the mouse central nervous system is determined by internal ribosome entry site-mediated translation

Mouse cells are not permissive for the replication of human rhinovirus type 2 (HRV2). To determine the role of the HRV2 internal ribosome entry site (IRES) in determining species specificity, a recombinant poliovirus (P1/HRV2) was constructed by substituting the poliovirus IRES with the IRES from HRV2. This recombinant virus replicated in all human and murine cell lines examined, demonstrating that the HRV2 IRES does not limit viral replication in transformed murine cells. P1/HRV2 replicated in the brain and spinal cord in neonatal but not adult mice transgenic for the poliovirus receptor, CD155. Passage of P1/HRV2 in mice led to selection of a virus that caused paralysis in neonatal mice. To determine the relationship between HRV2 IRES-mediated translation and replication of P1/HRV2 in mice, recombinant human adenoviruses were used to express bicistronic mRNAs in murine organs. The results demonstrate that the HRV2 IRES mediates translation in organs of neonatal but not adult mice. These findings show that HRV2 IRES-mediated translation is a determinant of virus replication in the murine brain and spinal cord and suggest that the IRES determines the species specificity of HRV2 infection.

Manifestations of West Nile neuroinvasive disease

Since its introduction to North America in 1999, West Nile virus, an arthropod-borne flavivirus, has become the most significant cause of epidemic encephalitis in the western hemisphere. While most human infections with the virus are asymptomatic and the majority of symptomatic persons experience febrile illness, severe neurologic manifestations, including meningitis, encephalitis, and poliomyelitis may be seen. This review summarizes the virology, epidemiology and pathogenesis of human infection with West Nile virus, and details recent advances in our understanding of the pathophysiology and various clinical manifestations of infection.

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.

Reflexes in prior polio and their relation to weakness and anterior horn cell loss

The aim of this study was to evaluate the reflex pattern in patients with prior polio and to relate these findings to the degree of anterior horn cell (AHC) involvement and loss of muscle force. Twenty-five prior polio subjects were investigated with electromyography (EMG), force testing and reflex studies, which included the patellar and Achilles reflex, H-reflex, T-response and interlimb reflex (ILR). The clinical reflexes, H/M-ratio and T-response amplitude at rest were positively correlated with force and negatively correlated with the degree of AHC loss. The H/M-ratio was decreased compared with age matched controls. ILR was present in 68% of the prior polio patients but did not exist in controls. The presence of the ILR was not correlated with the degree of AHC loss or force. The reflex studies gave two main findings. The first is reduced excitability of monosynaptic connections in the motor neuron pool, which is related to weakness. The other is the presence of ILR as an indicator of interneuronal hyper-excitability, which is not related to weakness.

Improvement of a Questionnaire Measuring Activity Limitations in Rising and Sitting Down in Patients With Lower-Extremity Disorders Living at Home

OBJECTIVE

To improve a self-administered questionnaire that includes 42 dichotomous items and measures activity limitations in rising and sitting down (R&S) in patients with lower-extremity disorders who live at home.

DESIGN

Cross-sectional study.

SETTING

Outpatient clinics of secondary and tertiary care centers.

PARTICIPANTS

Patients (N=759; 47% men; mean age +/- standard deviation, 60.7+/-15.2y) living at home, with lower-extremity disorders resulting from stroke, poliomyelitis, osteoarthritis, amputation, and complex regional pain syndrome type I.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

(1) Unidimensionality, indicating that items assess only a single construct; (2) fit with the one-parameter logistic model (OPLM), yielding information about patient and item location parameters; (3) intratest reliability, indicating consistency of patients' item scores; and (4) content validity, indicating completeness with which the items cover the important aspects of the construct that they are attempting to represent.

RESULTS

Thirty-nine of 42 items: (1) loaded on 1 component (variance explained, 59%; item component loadings, >or=.51), (2) showed good fit with the OPLM (P=.15), (3) had a good intratest reliability (Cronbach alpha=.96), and (4) had a good content validity (all important aspects represented).

CONCLUSIONS

A unidimensional scale that fits with the OPLM has been developed for measuring activity limitations in R&S in patients with lower-extremity disorders who live at home.

Functional Measures Across Neurologic Disease States: Analysis of Factors in Common

OBJECTIVE

To describe the underlying dimensions for a range of functional measures across 3 neurologic diseases at different time points.

DESIGN

Multiple cohort study.

SETTING

Combination of public hospital wards and community.

PARTICIPANTS

Patients (N=308) from 3 cohorts: paralytic poliomyelitis (n=38), mean of 25 years previously, assessed once; acute stroke admitted to hospital and followed up for 12 months postdischarge (n=181); and traumatic brain injury (TBI), admitted to hospital and followed up for 12 months postdischarge (n=89).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Barthel Index, FIM instrument, Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) physical component score (PCS) and mental component score (MCS), Community Integration Questionnaire (CIQ), and the London Handicap Score (LHS). Measures were compared at 2 time points: pre-event status for stroke, TBI and the polio cohort, and 12-month postdischarge status for stroke and TBI.

RESULTS

The different measures generally correlated highly within disease states at each time point. Principal components analysis revealed 2 underlying dimensions, a physical dimension onto which loaded the Barthel Index, FIM, PCS, and LHS and a cognitive/emotional dimension onto which loaded the MCS and, for subjects with polio, the CIQ. These 2 dimensions accounted for 69% of the variance in measures at the pre-event time point and 85% of the variance at the 12-month time point.

CONCLUSIONS

These data suggest 2 basic underlying dimensions across a wide range of measures in 3 different neurologic conditions even at different time points. Most of the variation in the measures can be captured using the 2 component summary scores (PCS, MCS) of the SF-36.

Increased fidelity reduces poliovirus fitness and virulence under selective pressure in mice

RNA viruses have high error rates, and the resulting quasispecies may aid survival of the virus population in the presence of selective pressure. Therefore, it has been theorized that RNA viruses require high error rates for survival, and that a virus with high fidelity would be less able to cope in complex environments. We previously isolated and characterized poliovirus with a mutation in the viral polymerase, 3D-G64S, which confers resistance to mutagenic nucleotide analogs via increased fidelity. The 3D-G64S virus was less pathogenic than wild-type virus in poliovirus-receptor transgenic mice, even though only slight growth defects were observed in tissue culture. To determine whether the high-fidelity phenotype of the 3D-G64S virus could decrease its fitness under a defined selective pressure, we compared growth of the 3D-G64S virus and 3D wild-type virus in the context of a revertible attenuating point mutation, 2C-F28S. Even with a 10-fold input advantage, the 3D-G64S virus was unable to compete with 3D wild-type virus in the context of the revertible attenuating mutation; however, in the context of a non-revertible version of the 2C-F28S attenuating mutation, 3D-G64S virus matched the replication of 3D wild-type virus. Therefore, the 3D-G64S high-fidelity phenotype reduced viral fitness under a defined selective pressure, making it likely that the reduced spread in murine tissue could be caused by the increased fidelity of the viral polymerase.

RNA viruses have the highest error rates in nature, resulting in the likelihood that each virus differs from other viruses in the population by one or more mutations. The consequence of this “infidelity” is that the viral population as a whole, under selective pressure from the immune system or antiviral drugs, may benefit from adaptive changes in a subset of its members. Therefore, it has been theorized that RNA viruses need high error rates to survive in complex environments. We tested this hypothesis using a drug-resistant poliovirus that contains a mutation in its polymerase that reduces errors during replication. We found that this high-fidelity mutant virus has reduced growth in mice, a complex environment where mutations may be required for growth and spread within the infected animal. At least part of this attenuation is likely due to the high fidelity of this mutant virus, since it was unable to compete with the low-fidelity version of the virus in the context of a defined selective pressure. Therefore, it is likely that mutations do benefit viral populations, especially in complex environments such as an infected animal or human.

The physiological challenges of the 1952 Copenhagen poliomyelitis epidemic and a renaissance in clinical respiratory physiology

The 1952 Copenhagen poliomyelitis epidemic provided extraordinary challenges in applied physiology. Over 300 patients developed respiratory paralysis within a few weeks, and the ventilator facilities at the infectious disease hospital were completely overwhelmed. The heroic solution was to call upon 200 medical students to provide round-the-clock manual ventilation using a rubber bag attached to a tracheostomy tube. Some patients were ventilated in this way for several weeks. A second challenge was to understand the gas exchange and acid-base status of these patients. At the onset of the epidemic, the only measurement routinely available in the hospital was the carbon dioxide concentration in the blood, and the high values were initially misinterpreted as a mysterious "alkalosis." However, pH measurements were quickly instituted, the Pco(2) was shown to be high, and modern clinical respiratory acid-base physiology was born. Taking a broader view, the problems highlighted by the epidemic underscored the gap between recent advances made by physiologists and their application to the clinical environment. However, the 1950s ushered in a renaissance in clinical respiratory physiology. In 1950 the coverage of respiratory physiology in textbooks was often woefully inadequate, but the decade saw major advances in topics such as mechanics and gas exchange. An important development was the translation of the new knowledge from departments of physiology to the clinical setting. In many respects, this period was therefore the beginning of modern clinical respiratory physiology.

Impaired primary hemostasis with normal platelet function in Duchenne muscular dystrophy during highly-invasive spinal surgery

A defective, normal or enhanced hemostasis has been reported in Duchenne muscular dystrophy (DMD). A retrospective analysis of intra-and postoperative (up to 36 h) estimated blood losses was performed in 156 patients undergoing spinal surgery for: DMD (n = 31), idiopathic scoliosis (IS) (n = 70), poliomyelitis (n = 10), cerebral palsy (CP) (n = 28), spinal muscular atrophy (SMA) (n = 17). Platelet aggregation and bleeding times were also investigated in DMD patients. Immunohistochemistry for dystrophin was performed in platelets, megakaryocytes and blood vessels of normal tissues. DMD patients showed significantly higher intraoperative estimated blood losses (DMD: 3495+/-890 ml; IS: 2269+/-804 ml; poliomyelitis: 2582+/-1252 ml; CP: 2071+/-683 ml; SMA: 2464+/-806 ml; P < 0.05), while postoperative blood losses were similar among different groups. Higher estimated blood losses in DMD were independent of the duration of surgery, body weight, gender, age, vertebral levels or preoperative Cobb angle. DMD children had significantly prolonged bleeding times, but retained normal platelet function. From control samples dystrophin was expressed in vascular smooth muscle cells, but not in platelets. DMD appears to be characterized by immediate bleeding during highly-invasive surgery and increased bleeding time without platelet abnormalities. Considering dystrophin expression in normal vascular smooth muscle cells, these results altogether suggest a selective defect of primary hemostasis in DMD, likely to be due to impaired vessel reactivity.

A 15-year follow-up of neuromuscular function in patients with prior poliomyelitis

A population-based cohort of poliomyelitis survivors was established and followed for 15 years (mean time since poliomyelitis was 40 years). Over time, the cohort demonstrated only a modest decline in function as measured by strength measurements, electrophysiologic assessments, and timed functional tasks. 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.

How is walking speed related to muscle strength? A study of healthy persons and persons with late effects of polio

OBJECTIVES

To evaluate the relationship between walking speed and muscle strength in the lower extremities in healthy persons and in persons with late effects of polio and to compare the models for these relationships.

DESIGN

Retrospective analysis.

SETTING

University hospital department.

PARTICIPANTS

An urban sample of 144 healthy men and women (age range, 40-79 y) and 234 (146 women, 88 men) subjects with late polio.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Muscle strength in the lower extremities was measured and combined into an index. Walking speed for spontaneous and maximal walking was measured. A nonlinear regression model was developed.

RESULTS

Evidence was provided for the nonlinear relationship between walking speed and strength. A specific strength threshold could not be identified. The asymptote of this curve for maximal walking was 2.57 m/s in the healthy group and 2.02 m/s in the subjects with late effects of polio. A high body mass index (>25 kg/m2) lowered the asymptote.

CONCLUSIONS

It is important to prevent strength decrease that approaches the critical level where a further reduction affects walking speed more evidently. The difference in the relationship between muscle strength and walking speed for the 2 groups studied may partly depend on biomechanic imbalance between muscle groups.

Hormone replacement therapy and health behavior in postmenopausal polio survivors

OBJECTIVES

Little is known about menopause and hormone replacement therapy (HRT) use in women with disabilities. The objectives of this study were to explore the health behaviors, health outcomes, and efficacy of HRT in a group of postmenopausal polio survivors and to compare selected outcomes to nationally representative cohorts.

METHODS

One hundred and thirty-one postmenopausal polio survivors completed self-report surveys on health behaviors, HRT use, functional status, and psychosocial well-being. During a physical examination, fasting cholesterol and body mass index (BMI) were collected. Independent sample t-tests and Chi-square analysis were used to compare HRT users and non-users on health behaviors and health outcomes; logistic regression was used to predict HRT use.

RESULTS

Prevalence of HRT use was 58%. Only BMI predicted HRT use (OR = 0.30, CI: 0.11-0.81). HRT users had better high density lipoprotein (HDL), low density lipoprotein, total cholesterol/HDL ratios, lower BMIs, were more confident when communicating with their physicians, more likely to discuss menopause with their physician, and experienced greater overall stress. HRT was not associated with health behavior, health-related quality of life, mood, or life satisfaction. Compared to non-disabled women, more of these women had higher total cholesterol, obesity, more sleeping problems, and were less likely to vigorously exercise or smoke.

CONCLUSIONS

HRT did not confer substantial benefits in these postmenopausal polio survivors to warrant them using HRT at a higher rate than their non-disabled peers. Comparisons to their non-disabled peers suggested they may be at higher risk for adverse health problems associated with postmenopause.

Use of a standardized menopause symptom rating scale in a sample of women with physical disabilities

OBJECTIVE

To determine the psychometric properties of a menopause symptom rating scale developed on nondisabled women in a sample of women polio survivors with physical disabilities.

DESIGN

The 25-item Menopause Symptom List (MSL) was administered to 190 women between ages 40 and 65 not taking hormone or estrogen therapy. Factor analysis, bivariate correlation, and analysis of variance were performed to determine the scale's underlying structure, construct validity, and association with menopausal status.

RESULTS

Factor analysis revealed four factors: (1) psychological, (2) somatic-sensory, (3) somatic-sleep, and (4) vasomotor. Factors 1 and 3 were associated with postpolio sequelae, self-rated health, positive and negative affect, life satisfaction, and perceived stress. Factor 2 was associated with postpolio sequelae, basic activities of daily living, self-rated health, negative affect, life satisfaction, and perceived stress. Factor 4 was associated with postpolio sequelae, self-rated health, negative affect, and perceived stress. Comparison by menopause status found Factors 1 and 3 significantly differed between groups (F(2,181) = 6.68 and 4.17, respectively; P = 0.02). Contrary to expectations, vasomotor factor severity was not distinguished by menopause status.

CONCLUSIONS

Menopause symptom scales standardized on nondisabled women should be used cautiously with women with physical disabilities. Associations between construct validity measures and menopause symptomatology suggest a complex relationship between physical disability and menopause.

Long-term excretion of vaccine-derived poliovirus by a healthy child

A child was found to be excreting type 1 vaccine-derived poliovirus (VDPV) with a 1.1% sequence drift from Sabin type 1 vaccine strain in the VP1 coding region 6 months after he was immunized with oral live polio vaccine. Seventeen type 1 poliovirus isolates were recovered from stools taken from this child during the following 4 months. Contrary to expectation, the child was not deficient in humoral immunity and showed high levels of serum neutralization against poliovirus. Selected virus isolates were characterized in terms of their antigenic properties, virulence in transgenic mice, sensitivity for growth at high temperatures, and differences in nucleotide sequence from the Sabin type 1 strain. The VDPV isolates showed mutations at key nucleotide positions that correlated with the observed reversion to biological properties typical of wild polioviruses. A number of capsid mutations mapped at known antigenic sites leading to changes in the viral antigenic structure. Estimates of sequence evolution based on the accumulation of nucleotide changes in the VP1 coding region detected a "defective" molecular clock running at an apparent faster speed of 2.05% nucleotide changes per year versus 1% shown in previous studies. Remarkably, when compared to several type 1 VDPV strains of different origins, isolates from this child showed a much higher proportion of nonsynonymous versus synonymous nucleotide changes in the capsid coding region. This anomaly could explain the high VP1 sequence drift found and the ability of these virus strains to replicate in the gut for a longer period than expected.

Musculoskeletal pain in polio survivors and strength-matched controls

OBJECTIVES

To determine whether a significant difference exists between musculoskeletal symptoms of polio survivors and those of older adults with no history of polio, and to determine if activity level and strength predict pain in either group.

DESIGN

Matched research design.

SETTING

A research laboratory in a rehabilitation setting.

PARTICIPANTS

Fifty-four polio survivors and 54 adults with no history of polio were matched for gender, race, and bilateral knee extensor strength and selected from a cohort of 316 subjects who participated in a study on the relation between activity level and health status.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Location and severity of musculoskeletal pain, activity frequency and intensity level, maximum voluntary isometric strength, and physical performance measures.

RESULTS

Polio survivors reported significantly more symptoms than the matched controls ( P <.05). Symptom status among the polio survivors was strongly associated with performance strain, perceived exertion, and activity intensity. Although the polio survivors had activity frequencies and habitual walking speeds that were similar to those from the matched controls, there was evidence that they performed activities at higher intensity levels.

CONCLUSIONS

Activity level is a factor in the development of musculoskeletal symptoms in polio survivors. Polio survivors who perform at higher intensity levels are more likely to have moderate to severe pain and more mobility difficulties.

Heparan sulfate-independent infection attenuates high-neurovirulence GDVII virus-induced encephalitis

The high-neurovirulence Theiler's murine encephalomyelitis virus (TMEV) strain GDVII uses heparan sulfate (HS) as a coreceptor to enter target cells. We report here that GDVII virus adapted to growth in HS-deficient cells exhibited two amino acid substitutions (R3126L and N1051S) in the capsid and no longer used HS as a coreceptor. Infectious-virus yields in CHO cells were 25-fold higher for the adapted virus than for the parental GDVII virus, and the neurovirulence of the adapted virus in intracerebrally inoculated mice was substantially attenuated. The adapted virus showed altered cell tropism in the central nervous systems of mice, shifting from cerebral and brainstem neurons to spinal cord anterior horn cells; thus, severe poliomyelitis, but not acute encephalitis, was observed in infected mice. These data indicate that the use of HS as a coreceptor by GDVII virus facilitates cell entry and plays an important role in cell tropism and neurovirulence in vivo.

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.

Measuring activity limitations in climbing stairs: development of a hierarchical scale for patients with lower-extremity disorders living at home11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the author(s) or on any organization with which the author(s) is/are associated

OBJECTIVE

To develop a hierarchical scale that measures activity limitations in climbing stairs in patients with lower-extremity disorders living at home.

DESIGN

Cross-sectional study with Mokken scale analysis of 15 dichotomous items.

SETTING

Outpatient clinics of secondary and tertiary care centers.

PARTICIPANTS

Patients (N=759; mean age +/- standard deviation, 59.8+/-15.0y; 48% men) living at home, with different lower-extremity disorders: stroke, poliomyelitis, osteoarthritis, amputation, complex regional pain syndrome type I, and diabetic foot problems.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

(1) Fit of the monotone homogeneity model, indicating whether items can be used for measuring patients; (2) fit of the double monotonicity model, indicating invariant (hierarchical) item ordering; (3) intratest reliability, indicating repeatability of the sum score; and (4) differential item functioning, addressing the validity of comparisons between subgroups of patients.

RESULTS

There was (1) good fit of the monotone homogeneity model (coefficient H=.50) for all items for all patients, and for subgroups defined by age, gender, and diagnosis; (2) good fit of the double monotonicity model (coefficient H(T)=.58); (3) good intratest reliability (coefficient rho=.90); and (4) no differential item functioning with respect to age and gender, but differential item functioning for 4 items in amputees compared with nonamputees.

CONCLUSIONS

A hierarchical scale, with excellent scaling characteristics, has been developed for measuring activity limitations in climbing stairs in patients with lower-extremity disorders who live at home. However, measurements should be interpreted with caution when comparisons are made between patients with and without amputation.

A pilot study of falls, fear of falling, activity levels and fall prevention actions in older people with polio

BACKGROUND AND AIMS

Polio survivors are ageing, and reporting new complications including falls. The aims of this study were: 1) to determine the frequency of falls, circumstances surrounding them, and the consequences of falls in older people who have polio; and 2) to investigate the range of fall prevention interventions undertaken to reduce the individual's risk of falling.

METHODS

A survey was conducted of members of the Eastern Polio Support Group of Victoria. Twenty-eight respondents (70%; 7 male, 21 female) had a mean age of 66 years and an average duration of 57 years since the onset of polio. The survey addressed demographic data, mobility, frequency and description of falls over the last 12 months, their consequences, and community services utilized. The Modified Falls Efficacy Scale (MFES) and Human Activity Profile (HAP) were also completed. Comparative data on the MFES and HAP were obtained from age- and gender-matched healthy community-dwelling older people.

RESULTS

Fourteen respondents (50%) reported one or more falls over the past 12 months, half reporting multiple falls. Two-thirds of falls occurred while walking. Of those who fell, 67% did not require medical attention. The highest percentage of injuries were bruises or grazes (44%), with one fracture reported. Sixty-one percent reported being fearful of falling, with an average MFES of 7.4 (+/-2.0), compared with the average of 9.7 (+/-0.5) for the age- and gender-matched controls (p<0.05). Only 5 of the respondents reported changing their level of activity as the result of a fall. A significant difference was identified on the Adjusted Activity Score (AAS) of the HAP between polio non-fallers (mean 56.3+/-19.1), polio fallers (mean 40.1+/-15.6) and age- and gender-matched controls (mean 73.5+/-10.3) (F2,46=25.5, p=0.000). The median number of fall prevention activities undertaken in the previous 12 months was one, 11 of the 28 respondents undertaking two or more. The most common interventions implemented were vision checks (42%) and review of medications by a doctor (25%).

CONCLUSIONS

A high rate of falling, fear of falling and low activity levels exist in older people with polio. There is a need for further research and clinical programs to reduce falls and injuries in this group.

Electrodiagnostic features of acute paralytic poliomyelitis associated with West Nile virus infection

West Nile virus (WNV) infection is a potentially fatal disease, with meningoencephalitis being its most common neurological manifestation. Guillain-Barré syndrome (GBS) has also been described, but acute paralytic poliomyelitis has only recently been recognized. We report the clinical and electrodiagnostic findings of five patients with WNV infection, who presented with acute paralytic poliomyelitis. Three patients manifested focal asymmetrical weakness, and two had rapid ascending quadriplegia mimicking GBS. Electrodiagnostic studies during the acute illness showed normal sensory nerve action potentials, compound motor action potentials of normal or reduced amplitude, and no slowing of nerve conduction velocities. Depending on the timing of the examination, fibrillation potentials were widespread, including in those with focal weakness. Cervical magnetic resonance imaging in one patient showed abnormal T2-weighted signals in the spinal cord gray matter. On follow-up, signs of clinical improvement were seen in one patient, whereas two remained quadriplegic and ventilator-dependent 5 months after the onset. This report highlights the value of the electrodiagnostic studies in the diagnosis and prognosis of focal or generalized weakness due to acute paralytic poliomyelitis associated with WNV infection.

Cell-dependent role for the poliovirus 3' noncoding region in positive-strand RNA synthesis

We previously reported the isolation of a mutant poliovirus lacking the entire genomic RNA 3' noncoding region. Infection of HeLa cell monolayers with this deletion mutant revealed only a minor defect in the levels of viral RNA replication. To further analyze the consequences of the genomic 3' noncoding region deletion, we examined viral RNA replication in a neuroblastoma cell line, SK-N-SH cells. The minor genomic RNA replication defect in HeLa cells was significantly exacerbated in the SK-N-SH cells, resulting in a decreased capacity for mutant virus growth. Analysis of the nature of the RNA replication deficiency revealed that deleting the poliovirus genomic 3' noncoding region resulted in a positive-strand RNA synthesis defect. The RNA replication deficiency in SK-N-SH cells was not due to a major defect in viral translation or viral protein processing. Neurovirulence of the mutant virus was determined in a transgenic mouse line expressing the human poliovirus receptor. Greater than 1,000 times more mutant virus was required to paralyze 50% of inoculated mice, compared to that with wild-type virus. These data suggest that, together with a cellular factor(s) that is limiting in neuronal cells, the poliovirus 3' noncoding region is involved in positive-strand synthesis during genome replication.

The double-stranded RNA-activated protein kinase mediates viral-induced encephalitis

The double-stranded (ds) RNA-activated protein kinase (PKR) plays an important role in control of viral infections and cell growth. We have studied the role of PKR in viral infection in mice that are defective in the PKR signaling pathway. Transgenic mice were derived that constitutively express a trans-dominant-negative kinase-defective mutant PKR under control of the beta-actin promoter. The trans-dominant-negative PKR mutant expressing transgenic mice do not have a detectable phenotype, similar to observations with PKR knock-out mice. The requirement for PKR in viral pathogenesis was studied by intracerebral infection of mice with a mouse-adapted poliovirus. Histopathological analysis revealed diffuse encephalomyelitis with severe inflammatory lesions throughout the central nervous system (CNS) in infected wild-type mice. In contrast, histopathological evaluation of virus-injected trans-dominant-negative PKR transgenic mice as well as PKR knock-out mice yielded no signs of tissue damage associated with inflammatory host responses. However, the virus did replicate in both models of PKR-deficient mice at a level equal to that observed in wild-type infected mice. Although the results indicate a clear difference in susceptibility to poliovirus-induced encephalitis, this difference manifests clinically as a slight delay in fatal neuropathy in trans-dominant-negative PKR transgenic and PKR knock-out animals. Our observations support the finding that viral-induced PKR activation may play a significant role in pathogenesis by mediating the host response to viral CNS infection. They support PKR to be an effective target to control tissue damage due to deleterious host responses to viral infection.