Late postpoliomyelitis muscular atrophy: clinical, virologic, and immunologic studies

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.

Identification of novel candidate protein biomarkers for the post-polio syndrome - implications for diagnosis, neurodegeneration and neuroinflammation

Survivors of poliomyelitis often develop increased or new symptoms decades after the acute infection, a condition known as post-polio syndrome (PPS). The condition affects 20-60% of previous polio patients, making it one of the most common causes of neurological deficits worldwide. The underlying pathogenesis is not fully understood and accurate diagnosis is not feasible. Herein we investigated whether it was possible to identify proteomic profile aberrations in the cerebrospinal fluid (CSF) of PPS patients. CSF from 15 patients with well-defined PPS were analyzed for protein expression profiles. The results were compared to data obtained from nine healthy controls and 34 patients with other non-inflammatory diseases which served as negative controls. In addition, 17 samples from persons with secondary progressive multiple sclerosis (SPMS) were added as relevant age-matched references for the PPS samples. The CSF of persons with PPS displayed a disease-specific and highly predictive (p=0.0017) differential expression of five distinct proteins: gelsolin, hemopexin, peptidylglycine alpha-amidating monooxygenase, glutathione synthetase and kallikrein 6, respectively, in comparison with the control groups. An independent ELISA confirmed the increase of kallikrein 6. We suggest that these five proteins should be further evaluated as candidate biomarkers for the diagnosis and development of new therapies for PPS patients.

Treatment of picornavirus infections

The picornaviruses are a diverse group of viral pathogens that together comprise the most common causes of infections of humans in the developed world. Within the picornavirus family are three well-known groups of human pathogens-the enteroviruses (including polioviruses, coxsackieviruses, and echoviruses), the rhinoviruses, and the hepatoviruses (including hepatitis A). Recently, the parechoviruses (formerly, echoviruses 22 and 23) have been classified as a fourth genus of human picornaviruses. This article will focus on the enteroviruses and rhinoviruses agents, for which substantial effort has been expended and recent successes reported towards the development of safe and effective antiviral therapy.

Antiviral therapy for enteroviruses and rhinoviruses

The picornaviruses are a diverse group of viral pathogens that together comprise the most common causes of infection of humans in the developed world. Within the picornavirus family are three well-known groups of human pathogens--the rhinoviruses, the enteroviruses (including polioviruses, coxsackieviruses and echoviruses) and the hepatoviruses (including hepatitis A virus). This article will focus on the rhinoviruses and enteroviruses, agents for which substantial effort has been expended, and recent successes reported, toward the development of safe and effective antiviral therapy.

Distinguishing clinical and electrodiagnostic features of X-linked bulbospinal neuronopathy

X-linked bulbospinal neuronopathy (XLBSN) or Kennedys disease is a rare inherited neuromuscular disease characterized by adult-onset muscle weakness, usually in a limb-girdle distribution. It is frequently misdiagnosed despite a distinctive clinical presentation, usually due to the absence of a clear family history, and perhaps also due to failure of recognition. Accurate diagnosis is crucial for genetic counseling purposes and because alternative diagnoses usually carry a poorer prognosis. We evaluated 4 patients with XLBSN and one symptomatic female heterozygote patient. Based on our clinical observations in these patients and a systematic review of previously reported cases, the following clinical and electrophysiologic features when present in the setting of adult-onset muscle weakness, are strongly suggestive of the disorder: 1) facial weakness, 2) facial twitching or fasciculations, 3) tongue weakness and atrophy, 4) postural hand tremor, 5) hypo- or areflexia, and 6) absent or low-amplitude sensory nerve action potentials despite clinically normal sensation. We also hypothesize regarding the possibility of partial expression of the abnormal XLBSN gene in a symptomatic heterozygote female patient.

Persistent poliovirus infection in mouse motoneurons

Poliovirus (PV) is the causal agent of paralytic poliomyelitis. Many survivors of the acute disease, after decades of clinical stability, develop new muscular symptoms called postpolio syndrome. It has been hypothesized that the persistence of PV in the spinal cord is involved in the etiology of this syndrome. To investigate the ability of PV to persist in the spinal cord after the onset of paralysis, we exploited a mouse model in which most animals inoculated with a mouse-adapted mutant survived after the onset of paralysis. Light microscopy and ultrastructural immunohistochemical studies and reverse transcription followed by nested PCR performed on spinal cord from paralyzed mice demonstrated that PV persisted in the mouse spinal cord for at least 12 months after the onset of paralysis. This mouse model provides a new tool for studying poliomyelitis evolution after the onset of paralysis.

Evidence of presence of poliovirus genomic sequences in cerebrospinal fluid from patients with postpolio syndrome

The postpolio syndrome (PPS) is characterized by new neuromuscular symptoms occurring 30 to 40 years after the acute episode of poliomyelitis paralysis. The presence of the poliovirus RNA genome in the cerebrospinal fluid from 10 patients with PPS and from 23 control patients was sought by using reverse transcription and a PCR specific for polioviruses and/or other enteroviruses. Poliovirus-specific genomic sequences in the 5' untranslated region and in the capsid region (VP1) were detected by reverse transcription PCR in 5 of 10 patients with PPS but in none of the control patients. Sequencing confirmed the presence of mutated poliovirus sequences. This finding suggests persistent viral infection in the central nervous system related to the presence of poliovirus genomes.

Muscle strength in postpolio patients: a prospective follow-up study

Forty-three former polio patients now complaining of new progressive muscle weakness (symptomatic patients) plus 13 former polio patients without new neuromuscular complaints were included in the study. The symptomatic patients reported high frequencies of other neuromuscular complaints and a decline in their functional level. Most frequent complaints were general fatigue, low backache, and muscle pain (97.7%, 86%, and 79.1%, respectively) and a decline in the ability to walk (80%). In a prospective follow-up averaging 2.1 years, the muscle strength of 26 muscles in all four limbs of each patient was assessed by manual muscle testing and was also measured isometrically using a handheld dynamometer. During the follow-up period, we did not find a significant decrease in muscle strength in the symptomatic patients as compared to patients without new neuromuscular complaints.

Pathogenetic mechanisms of post-polio syndrome: morphological, electrophysiological, virological, and immunological correlations

To understand the mechanism of post-poliomyelitis muscular atrophy (PPMA) and the post-polio syndrome (PPS) in general, we performed the following studies: (1) histopathology in spinal cord sections from patients who died 9 days to 44 years after acute paralytic poliomyelitis; (2) enzyme histochemistry, immunocytochemistry (for lymphocyte subsets, MHC antigens and N-CAM) and polymerase chain reaction (PCR) for poliovirus RNA in the muscle biopsies from symptomatic or asymptomatic muscles of post-polio patients; (3) determination of lymphocyte subsets and circulating IgG or IgM antibodies against GM1 and poliovirus; (4) virological studies in the spinal fluid for oligoclonal bands and search for poliovirus genome with PCR; (5) electrophysiological studies including single fiber EMG, fiber density and macro-EMG; and (6) [31P] exercise MRS spectroscopy on previously affected muscles to search for a metabolic correlate of fatigue. These studies concluded that in PPS a continuing dysfunction is present in the spinal cord motor neurons, resulting in ongoing muscle denervation and reinnervation first evident at the axonal branch points. Symptoms are related to attrition of the oversprouting motor neurons which after a period of time cannot support all their axonal sprouts, resulting in failure of re-reinnervation. In some patients with PPS there is also an ongoing immune activation and presence of defective viral particles in the spinal fluid. However, their role in the pathogenesis of PPS is presently unknown.

Detection of poliovirus antibodies and poliovirus genome in patients with the post-polio syndrome

To investigate the role of poliovirus (PV) infection in the development of the post-polio syndrome (PPS), we studied the serum, spinal fluid, peripheral blood lymphocytes, and muscle from 47 patients with PPS. We found high titers of IgM PV antibodies (up to 1:250) in the serum of 6 patients, compared to very low titers (less than 1:50) in normal subjects or disease controls. By polymerase chain reaction, using primers of the replicase PV gene, we amplified PV sequences in the peripheral blood lymphocytes in 7 of 37 patients and in the CSF in 4 of 40 patients, but in none of the controls. Sequencing of the amplified product confirmed that it belonged to PV type 1 with a 99.3% homology. We conclude that some patients with PPS have in the serum high titers of IgM anti-PV antibodies, implying an ongoing antibody response to a viral antigen. The presence of PV-RNA in the CSF or lymphocytes suggests possible persistence of mutated virus or defective PV particles. The significance of these findings in the pathogenesis of PPS remains to be determined.

Post-polio syndrome spinal cord pathology. Case report with immunopathology

Post-polio syndrome (PPS) describes the clinical onset of progressive muscular weakness many years after survival of acute paralytic poliomyelitis, often in muscle groups clinically unaffected by the original disease process. Prior pathologic descriptions of this often disabling, but not usually fatal, syndrome have been scanty. These have emphasized the presence of persistent or new inflammation in the meninges, spinal cord, and muscles of affected patients. The inflammation suggests several pathogenetic hypotheses, including persistent active poliovirus infection, autoimmune attack on central and peripheral nervous system elements, or increased vulnerability of poliovirus-damaged tissue to new infections. We have recently examined the central nervous system from a PPS patient. The cord showed focal perivascular intraparenchymal chronic inflammatory infiltrates. Immunoperoxidase staining demonstrated that the infiltrates were virtually pure populations of B lymphocytes (immunopositive with antibody L26, and immunonegative with the T cell marker UCHL1 as well as the macrophage marker HAM56). There were rare macrophages (HAM56 immunopositive) and no T cells. The character of the infiltrates suggests that PPS could be an autoimmune disorder mediated by antibodies produced in situ, and not by a cell-mediated process. Additional important pathological features were the presence in the anterior horns of axonal spheroids and of moderate Wallerian degeneration in the lateral columns. The brain was entirely unremarkable, with no detectable cell loss of gliosis in the internal capsules or precentral gyri.

The post-polio syndrome as an evolved clinical entity. Definition and clinical description

Post-polio syndrome (PPS) refers to the new neuromuscular symptoms that occur at least 15 years after stability in patients with prior acute paralytic polio-myelitis. They include: (1) new muscle weakness and atrophy in the limbs, the bulbar or the respiratory muscles [post-poliomyelitis muscular atrophy (PPMA)] and (2) excessive muscle fatigue and diminished physical endurance. PPS is a clinical diagnosis that requires exclusion of all other medical, neurological, orthopedic or psychiatric diseases that could explain the cause of the new symptoms. Routine electromyography is useful to confirm chronic and ongoing denervation and exclude neuropathies. Muscle biopsy, single fiber electromyography (EMG), macro-EMG, serum antibody titers to polio virus, and spinal fluid studies are very useful research tools but they are rarely needed to establish the clinical diagnosis. PPS is a slowly progressive phenomenon with periods of stability that vary from 3 to 10 years. Current evidence indicates that PPS is the evolution of a subclinically ongoing motor neuron dysfunction that begins after the time of the acute polio. It is clinically manifested as PPS when the well-compensated reinnervating process crosses a critical threshold beyond which the remaining motor neurons cannot maintain the innervation to all the muscle fibers within their motor unit territory.

Macro EMG follow-up study in post-poliomyelitis patients

We investigated the muscle strength and motor unit (MU) territory of five patients with postpolio syndrome (PPS), six stable patients with prior poliomyelitis, and five healthy volunteers. The MU territory was assessed by measuring amplitudes of motor unit potentials (MUPs) recorded by the macro EMG technique. The investigations were repeated after 11-20 months (mean 15.6). The macro MUP amplitudes in both patient groups were markedly increased (P = 0.02). However, no statistical difference was found between the two groups in the initial amplitude values. Macro MUP amplitudes obtained on repeated examinations did not differ significantly from the initial macro MUP amplitudes in any of the three groups. In three individual PPS patients, a decline in muscle strength on the follow-up study was documented, providing the diagnosis of post-poliomyelitis muscular atrophy (PPMA). The three PPMA patients had the highest initial macro MUPs. Two of them showed a decrease in macro MUP amplitudes on follow-up. These findings suggest that a later breakdown of oversized MUs may play a role in the pathogenesis of PPMA.

Comparative study of spinal cord ubiquitin expression in post-poliomyelitis and sporadic amyotrophic lateral sclerosis

This study addresses the suggested possible pathogenetic relationship between the late-onset muscular atrophy in patients with the prior diagnosis of poliomyelitis and amyotrophic lateral sclerosis (ALS). For this purpose we applied immunohistochemical techniques to determine the presence of pathological structures that were stained for ubiquitin (a protein involved in degenerative processes) in the spinal cords of patients with a history of poliomyelitis and compared the results with those of ALS, a condition in which cytoplasmic ubiquitin-positive inclusions are invariably found in the anterior horn cells. Our results indicate that post-poliomyelitis patients have no ubiquitin-reactive inclusion bodies in these cells; however, some immunopositive globular and cord-shaped structures are seen in less-affected areas. Similar structures were also found in the spinal cords from patients with ALS and from normal individuals. Our findings would suggest that the pathogenesis of late muscular atrophy in post-poliomyelitis patients is dissimilar to that of ALS.

Dysphagia in postpolio patients: a videofluorographic follow-up study

In patients with a history of acute paralytic poliomyelitis (APP), late progressive muscle weakness may arise, known as the progressive postpoliomyelitis muscular atrophy (PPMA). In 43 patients with PPMA, 8 were evaluated for recent or late progressive dysphagia. The mean interval between APP and onset of swallow symptoms was 27.1 years (range 23-45); the mean age of the patients was 45.4 years (range 35-52). Initial videofluorography showed signs of slight-to-moderate oropharyngeal dysfunction in 6 patients (delayed swallow reflex, diminished peristalsis of constrictor pharyngeus muscle, diminished laryngeal elevation, retention of bolus). In 2 patients, no abnormalities were found. Seven patients were reexamined after 12-36 months (mean 18). All reported subjective progression of symptoms. Videofluorography showed minor changes in 1 patient and unaltered findings in 6. No signs of aspiration were found either clinically or by video. We conclude that patients with PPMA complaining of late dysphagia do not show a significant loss in oropharyngeal function on 1-3 years follow-up.

Postpolio syndrome--response to deprenyl (selegiline)

Two patients with postpolio syndrome are presented. The first case developed mild Parkinson's syndrome, for which she was treated with a levodopa/carbidopa combination followed by the institution of deprenyl. An unexpected improvement in the symptoms of postpolio syndrome was noted. The second patient who was unaffected by Parkinson's syndrome was started on deprenyl alone and reported a similar improvement in symptomatology.

Prior poliomyelitis: an immunohistochemical study of cytoskeletal proteins and a marker for muscle fibre regeneration in relation to usage of remaining motor units

Patients with prior poliomyelitis with paresis and excessive use (n = 8) and low use (n = 6) of residual anterior tibial motor units (MUs) during walking were subjected to muscle biopsy of the anterior tibial muscle (TA). Antibodies directed against cytoskeletal proteins, spectrin and desmin, and against Leu-19, a myoblast and satellite cell related antigen, were applied. In the patients with excessive use of residual MUs there was an almost total predominance of hypertrophic type I fibres. In the hypertrophic fibres, staining for spectrin and desmin was normal while staining for Leu-19 was seen in a few fibres. Scattered atrophic fibres seen in the patients with excessive use showed staining for spectrin, desmin and Leu-19. In the patients with low use of residual MUs there were extensive pathological muscle fibre changes. Increased staining for spectrin, desmin and Leu-19 was found in most of the atrophic fibres. The predominance of type I fibres in the patients with excessive use of residual MUs is suggested to be due to muscle fibre transformation. The normal staining pattern for spectrin and desmin in the hypertrophic fibres indicates a normal cytoskeletal structure which might suggest that the adaptive muscle fibre changes are adequate to meet the increased demand. The increased staining for spectrin, desmin and Leu-19 in the atrophic fibres might indicate an ongoing denervation process which earlier has been suggested as an important factor for the development of postpolio progressive muscular atrophy.

Choline metabolism as a basis for the selective vulnerability of cholinergic neurons

The unique propensity of cholinergic neurons to use choline for two purposes--ACh and membrane phosphatidylcholine synthesis--may contribute to their selective vulnerability in Alzheimer's disease and other cholinergic neurodegenerative disorders. When physiologically active, the neurons use free choline taken from the 'reservoir' in membrane phosphatidylcholine to synthesize ACh; this can lead to an actual decrease in the quantity of membrane per cell. Alzheimer's disease (but not Down's syndrome, or other neurodegenerative disorders) is associated with characteristic neurochemical lesions involving choline and ethanolamine: brain levels of these compounds are diminished, while those of glycerophosphocholine and glycerophosphoethanolamine (breakdown products of their respective membrane phosphatides) are increased, both in cholinergic and noncholinergic brain regions. Perhaps this metabolic disturbance and the tendency of cholinergic neurons to 'export' choline--in the form of ACh--underlie the selective vulnerability of the neurons. Resulting changes in membrane composition could abnormally expose intramembraneous proteins such as amyloid precursor protein to proteases.

Late effects of polio: critical review of the literature on neuromuscular function

Many individuals who have had poliomyelitis are now complaining of several new problems attributed to their former illness including muscle atrophy; fatigue; progressive weakness; and muscle, back, and joint pain. This paper critically examines the literature regarding the neuromuscular effects of poliomyelitis. Weakness resulting from poliomyelitis was due to destruction of anterior horn cells. After the illness, muscle strength was partially recovered as a result of several physiologic adaptive mechanisms including terminal sprouting and reinnervation, myofiber hypertrophy, and, possibly, myofiber type transformation. Several pathophysiologic and functional etiologies have been proposed for late neuromuscular deterioration, but none has been proven. In fact, to date, there is no objective evidence documenting progressive loss of strength in polio survivors. Studies attempting to differentiate polio survivors with and without symptoms of deterioration have resulted in conflicting results; however, it appears reasonable to conclude that symptomatic postpolio subjects had a more severe illness with greater loss of neuromuscular function. Exercise may be helpful for many postpolio patients, but the prescription must be tailored to the individual to avoid problems of overuse or excessive fatigue.

Post-polio fatigue: a 31P magnetic resonance spectroscopy investigation

Changes in high energy phosphates (HEP) and intramuscular pH during exercise were measured in 17 patients with post-polio fatigue and in 28 healthy controls using 31P magnetic resonance spectroscopy (MRS). Subjects performed a dynamic hand grip exercise at low and high intensity. Mean changes in the HEP and pH showed no significant differences between the groups, although the post-polio group's response was highly variable. Six patients showed evidence of a lower lactate accumulation during the high intensity exercise when compared with controls. These data suggest that the whole body fatigue experienced by polio survivors is not related to any systemic metabolic abnormality.

Intrathecal immune response in patients with the post-polio syndrome

BACKGROUND

The syndrome of progressive muscular atrophy decades after acute paralytic poliomyelitis (post-polio syndrome) is not well understood. The theory that physiologic changes and aging cause the new weakness does not explain the immunologic abnormalities reported in some patients. An alternative explanation is persistent or recurrent poliovirus infection.

METHODS

We assessed the intrathecal antibody response to poliovirus and intrathecal production of interleukin-2 and soluble interleukin-2 receptors in 36 patients with the post-polio syndrome and 67 controls (including 13 who had had poliomyelitis but had no new symptoms and 18 with amyotrophic lateral sclerosis). Intrathecal antibody responses to measles, mumps, herpes simplex, and varicella zoster viruses were also determined.

RESULTS

Oligoclonal IgM bands specific to poliovirus were detected in the cerebrospinal fluid of 21 of the 36 patients with the post-polio syndrome (58 percent) but in none of the control group (P less than 0.0001). In quantitative studies there was evidence of increased intrathecal synthesis of IgM antibodies to poliovirus only among the patients with the post-polio syndrome; there was no increased synthesis of IgM to measles, mumps, herpes simplex, or varicella zoster viruses. The patients with post-polio syndrome had significantly higher mean (+/- SD) (cerebrospinal fluid levels of interleukin-2 and soluble interleukin-2 receptors than the controls (8.1 +/- 5.3 vs. 1.4 +/- 0.8 U per milliliter and 159.6 +/- 102.9 vs. 10.7 +/- 6.2 U per milliliter, respectively). The intrathecal synthesis of IgM antibodies to poliovirus correlated with the cerebrospinal fluid concentrations of interleukin-2 (P less than 0.0005) and soluble interleukin-2 receptors (P less than 0.001).

CONCLUSIONS

An intrathecal immune response against poliovirus is present in many patients with the post-polio syndrome. In some of these patients the recrudescence of muscle weakness may be caused by persistent or recurrent infection of neural cells with the poliovirus.

Circulatory autonomic failure 50 years after acute poliomyelitis

A 59-year old woman who presented with postural dizziness 50 years after an acute episode of poliomyelitis is described. There were no new neurological signs and no evidence of motor neuron disease. She had postural hypotension with an abnormal Valsalva. Investigations led to a diagnosis of hypo-adrenergic orthostatic hypotension, with a predominantly preganglionic sympathetic lesion and intact vagal baroreflex pathways. Although pure autonomic failure and multiple system atrophy are possible causes of circulatory autonomic failure, no other new neurological or autonomic features have developed during a 2 year follow-up. We propose that hypo-adrenergic orthostatic hypotension may be a late complication of poliomyelitis. Deterioration in ambulatory ability in a patient with previous poliomyelitis should additionally include assessment of cardiovascular autonomic function.

Dysphagia in patients with the post-polio syndrome

BACKGROUND AND METHODS

Dysphagia may develop in some patients many years after an attack of acute paralytic poliomyelitis. To identify clinical or subclinical signs of oropharyngeal dysfunction, we examined 32 patients (mean age, 48.9 years) with the post-polio syndrome (defined by new weakness in the limbs). Of the 32 patients, 14 had symptoms of new swallowing difficulties, and 18 were asymptomatic in this respect; 12 had a history of bulbar involvement during acute poliomyelitis. Swallowing function was assessed objectively by ultrasonography, videofluoroscopy, and an oral motor index score for 10 components of oral function.

RESULTS

All but 1 of the 32 patients, regardless of whether they had new symptoms or previous bulbar involvement, had some abnormality on detailed testing of oropharyngeal function; only 2 patients had any signs of aspiration. The mean oral motor index score (a quantitative measure of oral sensorimotor function) in the patients was higher than that in age-matched normal subjects (P less than 0.001). Videofluoroscopy showed abnormalities of varying severity, including unilateral bolus transport through the pharynx, pooling in the valleculae or pyriform sinuses, delayed pharyngeal constriction, and impaired tongue movements. On ultrasonography, the mean (+/- SD) duration of wet swallows was significantly longer in the symptomatic patients than in the asymptomatic patients (2.67 +/- 0.70 vs. 1.65 +/- 0.42 seconds). The four patients who were reexamined two years later had objective signs of worsening oropharyngeal function and corresponding new symptoms.

CONCLUSIONS

In patients with the post-polio syndrome, the bulbar muscles often have clinical or subclinical signs of dysfunction. These abnormalities suggest that in bulbar neurons there is a slowly progressive deterioration similar to that in the muscles of the limbs.

Nucleic acid detection systems for enteroviruses

The enteroviruses comprise nearly 70 human pathogens responsible for a wide array of diseases including poliomyelitis, meningitis, myocarditis, and neonatal sepsis. Current diagnostic tests for the enteroviruses are limited in their use by the slow growth, or failure to grow, of certain serotypes in culture, the antigenic diversity among the serotypes, and the low titer of virus in certain clinical specimens. Within the past 6 years, applications of molecular cloning techniques, in vitro transcription vectors, automated nucleic acid synthesis, and the polymerase chain reaction have resulted in significant progress toward nucleic acid-based detection systems for the enteroviruses that take advantage of conserved genomic sequences across many, if not all, serotypes. Similar approaches to the study of enteroviral pathogenesis have already produced dramatic advances in our understanding of how these important viruses cause their diverse clinical spectra.

Postpolio syndrome

The recurrence of symptoms many years after the rehabilitation of individuals who survived the acute illness, poliomyelitis, is a major concern. The purpose of this article is to provide information to the nurse practitioner (NP), who, as a primary health care provider, may be the first health professional to encounter persons with such complaints. Although no cure has been identified, diagnosis and treatment is available and is important to the psychosocial well-being of those who suffer from postpolio syndrome. This article reviews research on the syndrome including etiology, pathophysiology, symptoms and management, psychological issues, and the role of the aging process. Some areas where further research is indicated are also identified.

Prior poliomyelitis-reduced capillary supply and metabolic enzyme content in hypertrophic slow-twitch (type I) muscle fibres

Capillary supply and oxidative and glycolytic enzyme activities were determined in muscle biopsies from the tibialis anterior muscle in six prior polio patients and a control group. The polio patients, who had paresis and atrophy, but were able to walk normally by making maximal use of all remaining anterior tibial motor units, showed type I (slow-twitch) muscle fibre predominance with a mean (SD) of 98 (2%) type I fibres versus 81 (8)% in the controls (p less than 0.01) and muscle fibre hypertrophy, the average type I fibre cross-sectional area being 108% (p less than 0.005) larger than in the controls. The number of capillaries per muscle fibre was not significantly different from that in the control group, but with the increased muscle fibre area in the polio patients, the capillary density was significantly lower. The number of capillaries in contact with type I fibres relative to fibre area was 40% lower in the patients than in the controls (p less than 0.005). The levels of citrate synthase and phosphofructokinase were significantly lower (38% and 33%, respectively, p less than 0.05) in the patients than in the controls, indicating decreased oxidative and glycolytic potentials in the muscle fibres of the polio patients. It is proposed that the abnormal high-frequency activation of all remaining motor units during each step cycle recorded in these patients constitutes a stimulus for type I muscle fibre predominance and hypertrophy but that the overall low muscle usage results in a decreased stimulation of capillary proliferation and mitochondrial enzyme synthesis. The low capillary density and decreased oxidative and glycolytic enzyme potentials might be important factors for the development of muscle weakness, fatigue and muscle pain, which are commonly occurring symptoms in patients with prior poliomyelitis.

Clinical and electromyographic studies of postpoliomyelitis muscular atrophy

Eleven patients with progressive weakness following polio (postpoliomyelitis muscular atrophy syndrome) were compared electromyographically with nine patients who had stable strength following polio. Abnormalities included (1) abnormal motor unit characteristics in many muscles indicating widespread loss of motor neurons and reinnervation in muscles, including many not clinically affected by the polio; (2) prevalent spontaneous denervation potentials; and (3) abnormal single-fiber electromyographic jitter. These electromyographic abnormalities were similar in progressive and stable postpoliomyelitis patients even when muscles were separated by strength, stability, age and duration of the postpoliomyelitis state. Postpoliomyelitis muscular atrophy appears to be the clinically apparent end of the spectrum of abnormalities existing in all postpoliomyelitis patients.

Poliovirus vaccines. A continuing challenge

The control of poliomyelitis remains a provocative challenge. Alternative vaccination schedules, continuing research toward better vaccines, and ongoing international scientific, epidemiologic, and economic collaboration may make it possible to provide effective immunization for all children of the world and eventually may eradicate poliomyelitis worldwide, a goal set forward by the Expanded Programme on Immunization of the World Health Organization.

Lung function in patients with prior poliomyelitis

Lung volumes and spirometric flows, maximal respiratory pressures, lung diffusion capacity and blood gases were evaluated in 20 patients with prior poliomyelitis and compared with data from an age- and sex-matched control group. In the polio patients, static lung volumes and pulmonary flow capacity were significantly reduced to approximately 65% of the values of the control group. However, expiratory and inspiratory flows were normal in relation to lung volumes, while maximal respiratory pressures were significantly reduced in the polio patients. Static lung volumes and forced flows were correlated with the maximal respiratory pressures both in the polio patients and in the controls. However, when the muscle force in the polio patients decreased below a certain level, it became more important as a determinant of lung-flow capacity. The polio patients had a significantly increased PCO2 but a normal oxygen saturation and PCO2 was inversely correlated with the maximal respiratory pressures in the patients but not in the controls. The lung diffusion capacity was reduced in the polio patients compared to the controls, but less markedly than vital and total lung capacity. The findings indicate a restrictive respiratory dysfunction and alveolar hypoventilation most probably due to weakness of the respiratory muscles.

Isoelectric focusing studies of serum and cerebrospinal fluid in patients with antecedent poliomyelitis

The post-poliomyelitis syndrome (PPS) refers to symptoms of new weakness, fatigue, and pain years after recovery from acute poliomyelitis. Oligoclonal IgG bands have been reported in the cerebrospinal fluid (CSF) from PPS patients, suggesting that the syndrome is immune mediated or caused by persistent viral infection. We studied 15 paired serum and CSF samples and 6 unpaired CSF samples from a total of 21 patients with a prior history of poliomyelitis. Quantitative immune studies failed to show evidence for increased intrathecal IgG production relative to patients with noninflammatory central nervous system (CNS) disease. We found definite oligoclonal IgG bands in the CSF from only 1 patient, who also carried a diagnosis of multiple sclerosis. An isoelectric focusing poliovirus antigen overlay study showed evidence that suggested a CNS-specific antipoliovirus immune response in only 1 patient. Our results fail to support a dysimmune or persistent viral cause for post-poliomyelitis progressive muscular atrophy or PPS.