Polio: long-term problems

Review article : The late effects of poliomyelitis: aetiology and rehabilitation

Decades after their acute infection, many polio survivors are suffering renewed muscle weakness, increasing respiratory difficulties, musculoskeletal pain, fatigue and cold intolerance which lead to a 'second disability'. Some symptoms are due to chronic mechanical strain caused by using joints rendered unstable after the acute infection. The cause of others, such as postpoliomyelitis muscular atrophy, is . unknown although overuse, ageing, disuse atrophy and metabolic fatigue of axon sprouts in the abnormally large motor units may play a role. The aim of rehabilitation is to halt the progress of the condition and reduce its physical and psychological impact. Reduction in strenuous activity is important. The use of orthoses or a wheelchair may help to reduce pain and the energy cost of mobility. Respiratory aids such as the cuirasse can improve health. Counselling and peer group support can help the patient to accept his physical limitations.

Wearable monitoring devices for assistive technology: case studies in post-polio syndrome

The correct choice and customization of an orthosis are crucial to obtain the best comfort and efficiency. This study explored the feasibility of a multivariate quantitative assessment of the functional efficiency of lower limb orthosis through a novel wearable system. Gait basographic parameters and energetic indexes were analysed during a Six-Minute Walking Test (6-MWT) through a cost-effective, non-invasive polygraph device, with a multichannel wireless transmission, that carried out electro-cardiograph (ECG); impedance-cardiograph (ICG); and lower-limb accelerations detection. Four subjects affected by Post-Polio Syndrome (PPS) were recruited. The wearable device and the semi-automatic post-processing software provided a novel set of objective data to assess the overall efficiency of the patient-orthosis system. Despite the small number of examined subjects, the results obtained with this new approach encourage the application of the method thus enlarging the dataset to validate this promising protocol and measuring system in supporting clinical decisions and out of a laboratory environment.

Randomized controlled trial of strength training in post-polio patients

Many post-polio patients develop new muscle weakness decades after the initial illness. However, its mechanism and treatment are controversial. The purpose of this study was to test the hypotheses that: (1) after strength training, post-polio patients show strength improvement comparable to that seen in the healthy elderly; (2) such training does not have a deleterious effect on motor unit (MU) survival; and (3) part of the strength improvement is due to an increase in voluntary motor drive. After baseline measures including maximum voluntary contraction force, voluntary activation index, motor unit number estimate, and the tetanic tension of the thumb muscles had been determined, 10 post-polio patients with hand involvement were randomized to either the training or control group. The progressive resistance training program consisted of three sets of eight isometric contractions, three times weekly for 12 weeks. Seven healthy elderly were also randomized and trained in a similar manner. Changes in the baseline parameters were monitored once every 4 weeks throughout the training period. The trained post-polio patients showed a significant improvement in their strength (P < 0.05). The magnitude of gain was greater than that seen in the healthy elderly (mean +/- SE, 41 +/- 16% vs. 29 +/- 8%). The training did not adversely affect MU survival and the improvement was largely attributable to an increase in voluntary motor drive. We therefore conclude that moderate intensity strength training is safe and effective in post-polio patients.

Gait analysis on the treadmill - monitoring exercise in the treatment of paraplegia

STUDY DESIGN

A prospective study was performed to evaluate the gait training of seven consecutive spinal cord injured patients and 10 controls on a treadmill using instrumented gait analysis and video documentation.

OBJECTIVES

To determine whether it is possible to maintain gait motion within physiological limits during treadmill training.

SETTING

Primary and secondary care unit for spinal cord injury, Heidelberg, Germany.

METHODS

Treadmill training was instituted as early as possible. Gait analysis was performed when the patients were stable enough to walk without manual aid from therapists and enough endurance to allow measurements. A control group of healthy volunteers were examined as well. Video documentation and a camera system using passive markers were employed.

RESULTS

Treadmill training started with weight reduction of 25% of bodyweight (18 (0-35) kg), maximum walking speed 0.28 (0.15-0.7) m/s and maximum walking duration 4.7 (3-7) min. At the end of the training, weight reduction decreased to 9.3 (0-20) kg, maximum walking speed increased to 0.67 (0.23-1.1) ms with a maximum walking duration of 11 (8-15) min. 3-D motion analysis of hip, knee and ankle demonstrated joint excursions almost entirely within the limits of normal gait. Exceptions were due to fixed contractures.

CONCLUSIONS

Our data suggests that it is possible to perform early gait training on a treadmill with no supportive orthoses within the physiologic range of joint motion. The risk for repetitive stress injuries or other negative effects is low.

Another look at polio and postpolio syndrome

Polio survivors will likely be accessing the health care system because of acute and/or chronic conditions as they age. Therefore, they will again be interacting with health care professionals, especially orthopaedic and rehabilitation nurses. A comprehensive understanding of polio and postpolio syndrome will give orthopaedic and rehabilitation nurses the knowledge they will need to help polio survivors and their families achieve their highest potential and quality of life.

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.

Movement energetics of individuals with a history of poliomyelitis

Principles for evaluating the functional capacity of, and, therefore, exercise testing, chronically-disabled populations such as individuals with a history of poliomyelitis are considerably less well established than those for able-bodied persons. Therefore, we examined the use of indexes of movement economy and cardiorespiratory conditioning based on the results of a submaximal exercise test and oxygen consumption studies in individuals with a history of poliomyelitis. Subjects (n = 48) were categorized into four distinct groups, ie, having normal movement economy and either normal (n = 12) or reduced cardiorespiratory conditioning (n = 11), or having reduced movement economy and either normal (n = 10) or reduced cardiorespiratory conditioning (n = 15). There was no relationship between the indexes of movement economy and cardiorespiratory conditioning (p > 0.05) supporting that these indexes reflected physiologically-distinct entities. Irrespective of movement economy, deconditioned subjects had a reduced forced vital capacity (% predicted) (p < 0.05) and a higher resting heart rate (HR) (p < 0.01) compared to conditioned subjects. The difference in resting HR was attributed to conditioning level rather than initial arousal because resting HR and VO2 were comparable on repeated tests (p > 0.05). Although there was no difference in steady-state HR (% predicted maximum) among the four groups (p > 0.05), VO2 (% pred max) was significantly lower for the deconditioned than the conditioned subjects (p < 0.01). We concluded that determining movement economy and cardiorespiratory conditioning with a submaximal exercise test may enhance assessment and treatment outcome evaluation, hence provide a rational basis for rehabilitation interventions in individuals with a history of poliomyelitis.

Post-polio syndrome. An emerging threat to polio survivors

The manifestations of post-polio syndrome typically occur 20 to 40 years after an acute episode of poliomyelitis and are confined to previously affected muscles. Because of motor unit remodeling and direct mechanical damage, weakness increases in individual muscles until it exceeds their narrow margin of reserve and becomes clinically apparent. Although the exact cause is not clear, generalized weakness often occurs when several muscles are affected and various postural limb strategies used by the patient are no longer able to compensate for the loss of muscle strength. The mainstays of treatment are life-style changes to avoid overexertion and use of light-weight orthoses and assistive aids to unload the extremities. Exercise and surgery have a limited role in management.

The effects of long-term non-fatiguing resistance exercise in subjects with post-polio syndrome

Measures of torque were used to evaluate changes in muscle strength and endurance in 17 patients with post-polio syndrome who did prescribed resistance exercise for up to 2 years. Exercise compliance averaged 75%, with 16 subjects increasing the weight lifted in training. Maximum torque was significantly increased in the exercised muscle compared to the control muscle; no difference was seen in muscle endurance. Individuals with post-polio syndrome can increase muscle strength by doing non-fatiguing resistance exercise, but they should undergo quantitative testing of muscle strength a minimum of every 3 months to guard against overwork weakness.

Recent views on amyotrophic lateral sclerosis with emphasis on electrophysiological studies

Peripheral electrophysiological studies are of particular value of elucidating the anatomy and pathophysiology of neuromuscular diseases, but they can also help in providing clues to the etiology of the disease. Recent studies of the motor units in chronic denervating conditions including amyotrophic lateral sclerosis (ALS) are reviewed. These indicate that reinnervation is a relatively active process which compensates for the progressive loss of motoneurons in ALS until more than 50% of the motoneurons have died. There seems to be no predilection for death of motoneurons of any particular size in ALS. Fasciculations may arise both proximally and distally. The dying-back change is not a major feature of ALS. These and other data cast doubt on the etiological theories that ALS arises from premature aging of motoneurons, deficiency of motoneuron trophic factors, or an inhibitor of a motoneuronal sprouting factor, and point to the need to study metabolic changes intrinsic to the motoneuron in ALS.