Clinical spectrum of muscle weakness in human West Nile virus infection

Poliomyelitis has recently been identified as a cause of muscle weakness in patients with West Nile virus (WNV) infection. However, the clinical spectrum of WNV-associated weakness has not been described. We reviewed data on 13 patients with WNV infection. Patients with muscle weakness were classified into one of three distinct groups based on clinical features. Group 1 comprised five patients who developed acute flaccid paralysis, four with meningoencephalitis and one without fever or other signs of infection. Paralysis was asymmetric, and involved from one to four limbs in individual patients. Electrodiagnostic studies confirmed involvement of anterior horn cells or motor axons. Group 2 involved two patients without meningoencephalitis who developed severe but reversible muscle weakness that recovered completely within weeks. Muscle weakness involved both lower limbs in one patient and one upper limb in the other. Group 3 consisted of two patients who experienced subjective weakness and disabling fatigue, but had no objective muscle weakness on examination. In addition to the three distinct groups, two other patients developed exaggerated weakness in the distribution of preexisting lower motor neuron dysfunction. We conclude that the clinical spectrum of WNV-associated muscle weakness ranges from acute flaccid paralysis, with or without fever or meningoencephalitis, to disabling fatigue. Also, preexisting dysfunction may predispose anterior horn cells to additional injury from WNV. Awareness of this spectrum will help to avoid erroneous diagnoses and inappropriate treatment.

Quadriceps muscle strength and voluntary activation after polio

Quadriceps strength, maximal anatomical cross-sectional area (CSA), maximal voluntary activation (MVA), and maximal relaxation rate (MRR) were studied in 48 subjects with a past history of polio, 26 with and 22 without postpoliomyelitis syndrome (PPS), and in 13 control subjects. It was also investigated whether, apart from CSA, MVA and MRR were determinants of muscle strength. Polio subjects had significantly less strength, CSA, and MRR in the more-affected quadriceps than control subjects. MVA was reduced in 18 polio subjects and normal in all controls. PPS subjects differed from non-PPS subjects only in that the MVA of the more-affected quadriceps was significantly lower. Both CSA and MVA were found to be associated with muscle strength. Quadriceps strength in polio subjects was dependent not only on muscle mass, but also on the ability to activate the muscles. Since impaired activation was more pronounced in PPS subjects, the new muscle weakness and functional decline in PPS may be due not only to a gradual loss of muscle fibers, but also to an increasing inability to activate the muscles.

The reorganisation of motor units in different motor neuron disorders

A study was made of the degree and sequence of neurophysiological changes during motor unit reorganisation in motor neuron disease (MND), spinal muscular atrophy (SMA), and prior polio. Concentric needle EMG was used in conjunction with our own computerized EMG-LAB system. Motor unit action potential (MUAP) parameters were measured in 543 muscles on weak and maximum effort. MUAP amplitude and area were found to increase in the early stages of damage, declining to normal or subnormal values in the course of the disease. It was concluded that in MND there is a pathological sequence: denervation--reinnervation--terminal denervation. The increase in MUAP amplitude and area in the early stages of lesion, reflecting reinnervation, was much greater in SMA than MND and most marked in prior polio. The eventual decrease is an expression of terminal decompensation.

Predictors of virologically confirmed poliomyelitis in India, 1998-2000

As we progress toward eradication of polio, a growing proportion of cases of acute flaccid paralysis (AFP) reported are due to causes other than polio. AFP surveillance data from India for 1998-2000 were analyzed to determine the sensitivity and specificity of signs and symptoms present at initial case investigation and of residual weakness (which is used to classify AFP cases) for virologically confirmed poliomyelitis. Sensitivity was highest for age of <5 years (93%-97%) and residual weakness (74%-96%). Residual weakness was more sensitive among children aged <5 years. Cases of AFP in patients aged <5 years who have fever and asymmetrical paralysis are most likely to be confirmed as poliomyelitis. In countries with suboptimal surveillance for AFP, these results may help to prioritize investigation of AFP cases. The high sensitivity of residual weakness demonstrates the importance of 60-day follow-up examination for all patients with AFP, particularly those for whom the initial case investigation was inadequate or delayed.

Evaluation of healthy and diseased muscle with magnetic resonance elastography

OBJECTIVE

To investigate whether a new tissue-imaging technique, magnetic resonance elastography (MRE), offers a viable, noninvasive way to study healthy and diseased muscle.

DESIGN

Convenience sample.

SETTING

A magnetic resonance imaging (MRI) laboratory.

PARTICIPANTS

Eight control subjects (4 men, 4 women), between the ages of 24 and 41 years, with normal neuromuscular examinations and histories, and 6 subjects (3 men, 3 women), ages 17 to 63 years, with lower-extremity neuromuscular dysfunction (1 with childhood poliomyelitis, 2 with flaccid, 3 with spastic paraplegia).

INTERVENTIONS

Subjects lay supine with their legs within the coils of a 1.5T MRI machine, with their feet strapped to a footplate positioned so that the axes of rotation of their ankles coincided with the apparatus. All subjects were tested in a no-load (0 torque) condition. Control subjects were also evaluated as they isometrically resisted ankle dorsi- (20.2Nm, 40.5Nm) and plantar- (8.2Nm, 16.4Nm) flexion moments. Subjects with neuromuscular dysfunction were evaluated in the same manner, except 1 individual with residual lower-extremity strength who could only be tested in the resting and passive ankle dorsiflexion modes. Shear waves were induced with a 150-Hz electromechanic transducer located over the belly tibialis anterior. MRE images were collected with a gradient-echo technique gated to the transducer's motion. Wave-phase propagation was visualized with 8 equally offset images across 1 vibration-cycle.

MAIN OUTCOME MEASURES

Changes in shear-wave wavelength (lambda) and muscle stiffness (as expressed by the shear modulus [G]) in the tibialis anterior and gastrocnemius muscles.

RESULTS

Wavelength and G differed between the groups in all the muscles studied, and increased as the load increased. Moreover, lambda and G in the neuromuscular disease group at rest (eg, 3.88+/-0.48cm; range, 2.87-4.91cm; 38.40+/-00.77kPa; range, 22.35-59.67kPa) and in the lateral gastrocnemius were, respectively, more than 1.5 and 2.4 times larger than they were in the same muscle in the control group (2.56+/-0.28cm, 16.16+/-00.19kPa; P=.0002) (1Pa=1N/m(2)).

CONCLUSIONS

Shear-wave wavelength and muscle stiffness increased with load in healthy muscle. In addition, at least for our sample, these quantities differed significantly between muscles with and without neuromuscular disease. In summary, MRE appears to provide in vivo physiologic information about the mechanical properties of muscle at rest and during contraction that is not otherwise available. The potential of this technique for monitoring the effects of treatment and exercise on both healthy and diseased muscle merits further research.

Generating pathological gait patterns via the use of robotic locomotion models

In this article we explore the feasibility of modeling normal and pathological human gait using a relatively simple five-element model. We use a robust, nonlinear control scheme to regulate the gait patterns of the model. Simulated gait patterns are generated through the use of five constraint relationships that depend on four gait parameters. Two pathological conditions due to muscle weaknesses were simulated by modifying the control torques at the joints. We demonstrate that the model successfully approximates the qualitative and quantitative dynamic trends that were observed in normal and pathological human locomotion.

Poliovirus pathogenesis in a new poliovirus receptor transgenic mouse model: age-dependent paralysis and a mucosal route of infection

We constructed a poliovirus receptor (PVR) transgenic mouse line carrying a PVR delta cDNA driven by a beta-actin promoter. We refer to this model as the cPVR mouse. The cPVR mice express Pvr in a variety of tissues (including small intestines, brain, spinal cord, muscle, blood and liver) and are susceptible to infection after intraperitoneal, intracerebral or intramuscular inoculation of poliovirus. After intraperitoneal inoculation, poliovirus replication is observed in cPVR muscle, brain, spinal cord and, notably, small intestine. The cPVR mice exhibit a striking age-dependent paralysis after intramuscular infection, with 2-week-old mice being 10,000-fold more susceptible to paralytic disease than adult mice. The cPVR mice are also susceptible to paralysis following intranasal infection with poliovirus. After intranasal infection, virus replication is observed in the olfactory bulb, cerebrum, brain stem and spinal cord, suggesting that intranasal infection of cPVR mice is a model for bulbar paralysis. Intranasally infected mice frequently display unusual neurological behaviours. The PVR transgenic mouse reported here provides the first available model for a mucosal route of infection with poliovirus.

A comparison of the effects of exercise and lifestyle modification on the resolution of overuse symptoms of the shoulder in polio survivors: a preliminary study

OBJECTIVE

To compare the effectiveness of exercise and lifestyle modification therapy in treating shoulder symptoms in polio survivors with lower-extremity weakness.

DESIGN

A randomized parallel group study.

SETTING

Research laboratory.

PARTICIPANTS

Twenty-three subjects recruited from a cohort of 194 polio survivors who had participated in a previous study had bilateral hip-extensor and knee-extensor weakness and reported experiencing shoulder pain on a regular basis with daily activity.

INTERVENTIONS

Subjects were randomly assigned to 1 of 3 treatment groups. Members of group 1 were placed on a home exercise program that focused on strengthening their hip and knee extensors. Members of group 2 were instructed in lifestyle modification techniques designed to avoid shoulder overuse. Members of group 3 received both interventions.

MAIN OUTCOME MEASURES

Shoulder symptoms were quantified in terms of number and severity. Isometric strength of bilateral hip and knee extensors was measured with a hand-held dynamometer.

RESULTS

Symptoms improved in all 3 groups. However, members of the exercise-only group (group 1) were the only ones to show a significant difference in both number and severity of symptoms when pre- and posttreatment values were compared.

CONCLUSIONS

Both exercise and lifestyle modification therapies that focus on reducing the stress related to lower-extremity weakness are effective in treating shoulder overuse symptoms in polio survivors. A trend toward greater improvement in shoulder symptoms in subjects who participated in the exercise program and who also showed a trend toward increased knee-extensor strength supports muscle strength and/or endurance as a key factor.

Long-term follow-up of patients with nonparalytic poliomyelitis

OBJECTIVE

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

DESIGN

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

SETTING

Neurology department at a university hospital.

PARTICIPANTS

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

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSION

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

Former poliomyelitis as a health and socioeconomic factor. A paired sibling study

Eighty former poliomyelitis patients and the sibling nearest in age and of same sex were examined with matched-pair analysis to evaluate the effect of previous poliomyelitis (polio) on social factors and general health. Fifty-four pairs with women (68 %), and 26 pairs with men (32 %) with a mean age 60.4 years were included. Data were collected by questionnaire. There was no significant difference in length of education between patients and siblings (categories < 8 years, 8-12 years, and > 12 years). Employment rate at age 40 years was 78 % for patients and 88 % for siblings (full-time or part-time); this difference was not significant. Educational options were considered to have been excellent by 38 % of the patients and 26 % of the siblings (not significant), with a fair agreement within the pairs (kappa=0.31). There was no significant difference regarding professional options; rated as excellent by 33 % of patients, and 28 % of siblings, with a fair agreement (kappa=0.25) also for this issue. Perception of general health today expressed on a horizontal VAS-scale (0-10) was significantly lower among the patients than the siblings, mean values of 5.8 and 6.8 (P < 0.001) respectively. Patients also reported a lower quality of life (P=0.03), and less energy for leisure activities (P=0.008). Post polio symptoms like muscular and articular pain, and abnormal tiredness were more common among patients than siblings, whereas there was no difference regarding coexisting illness. In conclusion, polio patients and their siblings reckoned their educational and professional options to have been at the same level. The patients were well educated and employed to the same degree up to the age of 40 years, but now at a higher age reported reduced general health.

A part of the ulnar nerve as an alternative donor nerve for functioning free muscle transfer: a case report

A patient with no active elbow flexion because of poliomyelitis-like syndrome underwent functioning free muscle transfer for elbow flexion reconstruction in which a part of the ulnar nerve was used as a donor motor nerve. Fourteen months after surgery the patient had achieved 120 degrees of active elbow flexion against gravity without functional deficit of the donor ulnar nerve. A part of the ulnar nerve can be used as an alternative donor motor nerve for reconstruction of chronic C5-C6 (or C5-7) brachial plexus injury.

Neurovirulence of type 1 polioviruses isolated from sewage in Japan

Sixteen type 1 poliovirus strains were isolated from a sewage disposal plant located downstream of the Oyabe River in Japan between October 1993 and September 1995. The isolates were intratypically differentiated as vaccine-derived strains. Neutralizing antigenicity analysis with monoclonal antibodies and estimation of neurovirulence by mutant analysis by PCR and restriction enzyme cleavage (MAPREC) were performed for 13 type 1 strains of these isolates. The isolates were classified into three groups. Group I (five strains) had a variant type of antigenicity and neurovirulent phenotype. Group II (four strains) had the vaccine type of antigenicity and neurovirulent phenotype. Group III (four strains) had the vaccine type of antigenicity and an attenuated phenotype. Furthermore, it was demonstrated that the virulent isolates were neutralized by human sera obtained after oral poliomyelitis vaccine (OPV) administration, and the sera of rats immunized with inactivated poliovirus vaccine. Although vaccination was effective against virulent polioviruses, virulent viruses will continue to exist in the environment as long as OPV is in use.

Submaximal exercise capacity and maximal power output in polio subjects

OBJECTIVES

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

DESIGN

Cross-sectional survey.

SETTING

University hospital.

PARTICIPANTS

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

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSION

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

Sabin attenuated LSc/2ab strain of poliovirus spreads to the spinal cord from a peripheral nerve in bonnet monkeys (Macaca radiata)

Vaccine-associated paralytic poliomyelitis is a serious concern while using the live attenuated oral polio vaccine for the eradication of poliomyelitis. The bonnet monkey model of poliovirus central nervous system (CNS) infection following experimental inoculation into the ulnar nerve allows the comparative study of wild-type and attenuated poliovirus invasiveness. Dosages >/=10(4) TCID(50) of Mahoney strain of poliovirus type 1 [PV1(M)] result in paralysis. In contrast, even with 10(7) TCID(50) of Sabin attenuated strain of poliovirus type 1 (LSc/2ab), no paralysis occurs, but virus spreads into the CNS where viral RNA is found in spinal cord neurons. While wild-type PV1(M) viral RNA replicates in neurons (and possibly in glial cells) and in cells around vessel walls, which may be mononuclear or endothelial cells, attenuated viral RNA is detected only in neurons. Systemic viraemia and gastrointestinal virus shedding occurs only in PV1(M)-infected animals. While a systemic serologic response is detected in both groups of animals, cerebrospinal fluid antibodies are detected only in animals infected with PV1(M). Both the PV1(M) and LSc/2ab strains spread to the cervical spinal cord and then to the lumbar spinal cord following ulnar nerve inoculation. Neuronophagia and neuronal loss are only seen in PV1(M)-infected monkeys in whom clinical paralysis is observed. Infection with LSc/2ab does not result in neuronophagia, neuronal loss or clinical paralysis. Spread of attenuated poliovirus in spinal cord neurons without causing paralysis following inoculation into the ulnar nerve is an important finding.

Dynamic water exercise in individuals with late poliomyelitis

OBJECTIVE

To evaluate the specific effects of general dynamic water exercise in individuals with late effects of poliomyelitis.

DESIGN

Before-after tests.

SETTING

A university hospital department.

PARTICIPANTS

Twenty-eight individuals with late effects of polio, 15 assigned to the training group (TG) and 13 to the control group (CG).

INTERVENTION

The TG completed a 40-minute general fitness training session in warm water twice weekly. Assessment instruments included the bicycle ergometer test, isokinetic muscle strength, a 30-meter walk indoors, Berg balance scale, a pain drawing, a visual analog scale, the Physical Activity Scale for the Elderly, and the Nottingham Health Profile (NHP).

MAIN OUTCOME MEASURES

Peak load, peak work load, peak oxygen uptake, peak heart rate (HR), muscle function in knee extensors and flexors, and pain dimension of the NHP.

RESULTS

The average training period was 5 months; compliance was 75% (range, 55-98). No negative effects were seen. The exercise did not influence the peak work load, peak oxygen uptake, or muscle function in knee extensors compared with the controls. However, a decreased HR at the same individual work load was seen, as well as a significantly lower distress in the dimension pain of the NHP. Qualitative aspects such as increased well-being, pain relief, and increased physical fitness were reported.

CONCLUSIONS

A program of nonswimming dynamic exercises in heated water has a positive impact on individuals with late effects of polio, with a decreased HR at exercise, less pain, and a subjective positive experience. The program was well tolerated (no adverse effects were reported) and can be recommended for this group of individuals.

Secondary health conditions among middle-aged individuals with chronic physical disabilities: implications for unmet needs for services

Data from the Aging with Disability (AwD) Study are used to examine variations in the types and frequency of secondary conditions experienced by 301 middle-aged individuals living with the effects of three disabling conditions: polio (n = 124), rheumatoid arthritis (RA) (n = 103), and stroke (n = 75). All respondents were randomly selected from a county rehabilitation hospital or a community-based subject pool. Secondary conditions are operationalized as (1) the number of new health problems diagnosed or treated since the onset of the primary disability and (2) the amount of change/decline in basic and instrumental daily activities since a previous reference period in the disability trajectory. Also analyzed are changes in use of assistive devices and unmet needs for services. Differences in secondary conditions are examined within the AwD sample by impairment group and between samples by comparing AwD rates to national estimates for the same cohort. Results reveal significant differences in the types of new health problems reported by persons living with polio, RA, and stroke and document marked disparities, or accelerated aging, between disabled and nondisabled adults. Findings are discussed in terms of the changing health care needs of persons aging with disability and the importance of improving access to preventive services, ongoing rehabilitation, and assistive technology.

Inspiratory muscle training in patients with prior polio who use part-time assisted ventilation

OBJECTIVE

To evaluate whether inspiratory muscle training in patients with prior poliomyelitis (and with symptoms and signs of hypoventilation) who use part-time assisted ventilation could improve symptoms and respiratory muscle function without adverse effects.

DESIGN

Intervention study with before-after trial.

SETTING

Training was performed in the patients' homes; assessments were performed at the hospital.

PATIENTS

Ten prior-polio patients were included. Three of them did not complete the trial, and their data were not included in results of training.

INTERVENTION

Ten weeks of daily inspiratory muscle training.

MAIN OUTCOME MEASURES

Spirometry, maximal inspiratory and expiratory pressures, inspiratory muscle endurance, and questions regarding activities of daily living were performed.

RESULTS

Inspiratory endurance capacity over 5 minutes improved from 10.7 to 16.7cm H2O (p < .05) assessed at 15 on the Borg scale, and most patients improved in activities of daily living. The whole-body endurance capacity remained stable over the studied period.

CONCLUSION

Inspiratory muscle training and close supervision can increase respiratory muscle endurance and improve well-being in patients with prior polio who use part-time assisted ventilation.

Surgical options in the management of residual foot problems in poliomyelitis

Although poliomyelitis is not encountered in the Western countries, it is still endemic in the underdeveloped world. Because the foot commonly is involved, an understanding of the causative factors and the available options of treatment is essential before surgical intervention. It is important to note that inadequate or improper surgical procedures potentially can lead to more disability; a well-planned approach to the foot problem, after considering the patient as a whole and understanding the principles involved, is the best option.

Neuromuscular rehabilitation and electrodiagnosis. 4. Specialized neuropathy

This self-directed learning module briefly highlights the differential diagnosis for acute weakness in patients with acute respiratory failure requiring prolonged mechanical ventilation. It is part of the chapter on neuromuscular rehabilitation and electrodiagnosis in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article includes a discussion on the role of exercise in the treatment of patients with the late effects of poliomyelitis or with acute inflammatory demyelinating polyradiculoneuropathy.

An insole pressure measurement system: repeatability of postural data

This study analyzed the ability of an in-shoe plantar pressure measurement system to provide repeatable measurements of postural sway data for both healthy and clinical patients. Each participant's in-shoe pressure data were recorded for three trials during each test session during quiet stance. Healthy individuals (n = 9) participated on three consecutive days while clinical participants (n = 5) were tested on one day. Nine response variables were measured to assess their postural stability. Intrasubject measures were evaluated using the Kerlinger reliability procedure. Values provided directly by the Parotec System for a single day of testing yielded the following average coefficients: r = 0.95 (left), r = 0.97 (right) with mean coefficient values from the three day tests of: r = 0.98 (left), r = 0.98 (right). Variables calculated from raw data on a single day produced mean coefficients of: r = 0.77 (left), r = 0.76 (right) and over three days of: r = 0.65 (left), r = 0.66 (right). The ability to record highly reproducible data of postural sway parameters should assist clinicians to treat patients more confidently for balance deficiencies.