Enhancement of central nervous system remyelination in immune and non-immune experimental models of demyelination

Studies in both humans and experimental animals indicate that there is potential for full remyelination following CNS demyelination, but the factors that control the degree of myelin repair are unknown. In the Theiler's virus model of demyelination CNS remyelination can be promoted either by global immunosuppression or by selective immunoglobulin therapy. In this paper we discuss whether immunoglobulin-mediated remyelination is a characteristic of immune-mediated demyelination, or whether immunoglobulin-mediated remyelination also occurs in the toxic-traumatic model of lysolecithin-induced demyelination. Our data support the hypothesis that even in a non-primary immune model of demyelination, manipulating the immune system can be beneficial in myelin repair.

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.

Electrophysiological studies in children with paralytic poliomyelitis

Ten healthy children (Group I), twenty children with acute spinal poliomyelitis (Group II and III) and twenty children of post-polio residual paralysis (Group IV) between the age group of 9 months to 4 years were the study subjects. The motor nerve conduction velocity (MNCV), standardized distal motor latency (SDML) and motor latency (M-RL) were similar in all the groups studied No H-reflex could be elicited in children with acute spinal poliomyelitis seen within one week of onset of paralysis (Group II). The H-max from 4-6 week group (III) improved with time in 9-12 month (Group IV) but did not attain the control (Group I) value. The H-reflex latency (H-RL) which was prolonged in Group III children returned back to normal value in children with residual paralysis (Group IV). The M-max which was significantly reduced in Group II children further decreased in Group III children before showing a significant rise in children with residual paralysis (Group IV). The M-max showed a significant correlation to duration of paralysis during the first week of onset of the disease process and with the muscle power assessed clinically in children with residual paralysis (Group IV). The H/M ratio of children with acute paralysis (Group III) was similar to control while that of residual paralysis was significantly lower in comparison to controls. However, the corrected H/M ratio of children with acute paralysis (Group III) and residual paralysis (Group IV) was significantly lower than the controls. There was significant increase in corrected H/M ratio in group IV children compared to group III.

Final checkpoint in the drug-promoted and poliovirus-promoted apoptosis is under post-translational control by growth factors

The treatment of HeLa subline (HeLa-B) cells with cycloheximide or Actinomycin D resulted in a rapid (approximately 1.5 h and approximately 2.5 h, respectively) development of morphological and biochemical signs of apoptosis. The addition of fetal bovine serum to the cycloheximide-treated or Actinomycin D-treated cells suppressed the apoptotic reaction, as evidenced by the postponement of the DNA fragmentation for at least 9 and 5 h, respectively. A similar suppressive effect was observed upon the serum addition to cells undergoing abortive infection with poliovirus, which died of apoptosis in the absence of the serum. The serum appeared to exert its anti-apoptotic effect without any appreciable lag and even immediately blocked further progress of ongoing DNA fragmentation. The epidermal growth factor also suppressed, although less efficiently and more transiently, the apoptotic reaction promoted by the metabolic inhibitors. It is concluded that growth factors may affect, without modulating either transcription or translation, the balance of pro-apoptotic and anti-apoptotic activities at a final checkpoint, just preceding the irreversible effector step of apoptosis.

Dysphagia and post-polio syndrome: past, present, and future

Swallowing difficulties, oral motor weakness, and oral pharyngeal paralysis have been reported in the historical literature on polio and post-polio. Attention to this finding was minimal in the original epidemics as many persons with bulbar polio who may have been dysphagic did not survive. Swallowing was often supplemented by artificial feeding for those who were placed in respirators. Although swallowing difficulty was often present in the acute stages of the initial attack, it usually subsided or disappeared after several weeks. In cases in which bulbar polio was diagnosed, swallowing impairment may have lingered, but most survivors learned to produce compensatory maneuvers to aid them to swallow and did not complain of difficulty. In the recent decades of the 20th century, many persons who had believed themselves fully recovered from the insult of polio began to experience new symptoms; among them were new or heightened complaints of swallowing difficulty. Studies of these patients with PPS have revealed that dysphagia is not only present but may be progressive, and suggest that there is a slowly progressive deterioration of the bulbar neurons of PPS patients underlying the finding of new or exacerbated swallowing signs. Patients with PPS should be referred to speech-language pathologists for evaluation of voice, phonatory-respiratory, and swallowing function and initiation of appropriate remediation strategies to avoid the potential negative consequences of dysphagia.

Electromyographical evidence for exercise-induced diaphragm fatigue in patients with chronic cervical cord injury or prior poliomyelitis infection

The purpose of this study was to determine, in exercising patients, how much diaphragm force increases before electromyographical evidence of diaphragm fatigue occurs. The study was performed in ten male patients with complete cervical cord injury (CCI) at the C5 to C8 levels, and five male patients with prior poliomyelitis infection (PPI) requiring chronic treatment with intermittent positive pressure ventilation (IPPV) at night. We studied the time course of the diaphragmatic tension-time index (TTdi), the centre frequency (CFdi) of the diaphragm electromyogram (EMGdi) power spectrum, and the ventilatory parameters, during steady-state submaximal arm/leg exercise. During exercise, early signs of diaphragm fatigue were present in seven out of 10 CCI patients and in four out of five PPI patients, as indicated by a reduction in CFdi. The increase in TTdi achieved before reductions in CFdi occurred was twofold in both the CCI and PPI patients. All patients except for the PPI patients, who demonstrated a reduction in CFdi, showed an increase in minute ventilation (VE), achieved by increasing both their tidal volume (Vt) and the breathing frequency (fb). The PPI patients demonstrating reductions in CFdi during exercise also increased their VE however, this was achieved by increasing fb while Vt remained constant. Following the reductions in CFdi, the CCI patients further increased their TTdi throughout the exercise test, while the PPI patients reduced their TTdi values.

IN CONCLUSION

(1) During exercise, electromyographical evidence for diaphragmatic fatigue frequently occurred in the CCI and PPI patients studied; (2) Compared to the eightfold increase in TTdi seen in healthy subjects before reductions in CFdi occur, the TTdi values increased only two-fold before electromyographical evidence of diaphragm fatigue was present in these patients; (3) There is a clear discrepancy between the CCI and PPI patients who demonstrate electromyographical evidence of diaphragm fatigue, in terms of their ventilatory and TTdi responses.

Motor nerve conduction velocities calculated by F tacheodispersion in patients with anterior horn diseases

F tacheodispersion, a new neurophysiological technique based on F waves, was used to determine the motor nerve conduction velocities in 16 patients with motor neuron disease and 19 patients with sequelae following paralytic poliomyelitis. The findings were compared to two age-matched groups, each consisting of 20 healthy volunteers. In each subject the F wave maximal, minimal, mean conduction velocities and the difference between maximal and minimal velocities of the ulnar and peroneal nerves were calculated. M response distal latency, amplitude and conduction velocity were also measured. There was a statistical significant slowing of one or more of the F wave estimated velocities in the absence of M response abnormalities in 31.3% of nerves in motor neuron disease group and in 27.3% of nerves in the poliomyelitis group; between 6.3% and 37.5%, of the nerves studied showed a significant change in the difference between maximal and minimal conduction velocities. Our results favour the presence of changes of motor fibre conduction properties in some patients with anterior horn diseases.

Fatigue of chronically overused motor units in prior polio patients

This study was undertaken to investigate the mechanisms underlying fatigue of chronically overused motor units (MUs). The force of the tibialis anterior muscle (TA) and the firing properties of single MUs were studied during prolonged maximum voluntary effort in 10 prior polio patients selected such that daily living required all residual TA power. Almost all TA fibers were hypertrophic type I. Activities of intermyofibrillar succinate dehydrogenase (SDH) and calcium-stimulated myofibrillar adenosine triphosphatase (ATPase) were measured in single TA fibers from a representative patient. Neither insufficient motoneuron activation nor peripheral blocking of the electrical impulse played a major role in the loss of force during prolonged contraction or for slow recovery after contraction. The ratio of SDH to calcium-stimulated ATPase, representing the relation between energy resynthesis and energy utilization, was significantly (P < 0.001) lower in prior polio patients (0.230 +/- 0.096) compared to control (0.515 +/- 0.097) type I fibers.

Lateralization of cutaneous inflammatory responses in patients with unilateral paresis after poliomyelitis

Unilateral paresis remaining after poliomyelitis may affect the expression of inflammatory diseases by lateralization of the disease manifestations. The purpose of this study was to assess the impact of the unilateral paresis after poliomyelitis on lateralization of neurogenic inflammation and immune responsiveness. The delayed-type hypersensitivity (DTH) reaction to tuberculin was used as an in vivo measure of antigen-specific T lymphocyte reactivity. Assessment of axon reflex vasodilatation was simultaneously employed to test for neurogenic inflammation. Fourteen of the 16 polio patients displayed a positive DTH reaction to tuberculin. All but two showed weaker DTH reaction on the paretic- compared to the contralateral-side (P = 0.001). Magnitude of electrically evoked axon reflexes significantly correlated to asymmetries of DTH responses. We conclude that damage of lower motor neuron leads to ipsilateral down-regulation of T cell-mediated cutaneous inflammation. This lateralization of DTH responses is related to deficiencies in motor and sympathetic innervation of the paretic extremity.

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.

Diaphragm function in patients with cervical cord injury or prior poliomyelitis infection

Diaphragm function was evaluated in cervical cord injury patients (CCI), 1-3 years after injury (CCI(1-3)) and 10 years or more after injury (CCI(> or = 10)), as well as in a group of prior poliomyelitis infection patients (PPI), requiring intermittent positive pressure ventilation (IPPV) for about 6 h per night. Measurements included transdiaphragmatic pressure swings (delta Pdi) at rest, during maximal inspiratory efforts against closed airways (delta Pdi(max)) and during sniff manoeuvres (ie maximal inhalation through the nose, delta Pdi(sniff)), vital capacity normalized to age and height (VC(%pred)), tidal volume (Vt), relative inspiratory time (Ti/Ttot), breathing frequency (f(b)), and the tension-time index of the diaphragm (TTdi = delta Pdi/delta Pdi(max) x Ti/Ttot). The median VC(%pred) was 50% in the CCI(1-3) group and 57% in the CCI (> or = 10) group, but only 28% in the PPI group. Delta Pdi(max) values were similar for the CCI(1-3) (11.8 kPa) and CCI(> or = 10) (11.9 kPa) groups but were lower (71. kPa) in the PPI group. Due to the reduction in delta Pdi(max), the PPI group had higher delta Pdi/delta Pdi(max) values than the CCI groups, however, the TTdi was similar amongst the different groups studied. A submaximal exercise test in five cervical cord injury patients and in five polio patients with similar delta Pdi(max), delta Pdi(sniff) and TTdi values at rest revealed clear group differences with respect to force development, in that CCI patients showed significant increases in TTdi, while PPI demonstrated only minor changes. In CCI patients, an increase in ventilation was accompanied by an increase in delta Pdi/delta Pdi(max) while in contrast, the PPI patients showed no increase in delta Pdi/delta Pdi(max). We conclude that CCI patients, both recently and previously injured, have a similar maximal inspiratory force and are less impaired than the PPI patients. The TTdi at rest is similar in all groups, but the PPI patients react to inspiratory loads with little increases in TTdi, while the CCI patients increase their TTdi above fatiguing (0.15) levels. The different behaviours may be linked to loss of sensory pathways in the CCI patients.

Pattern of denervation in clinically uninvolved limbs in patients with prior poliomyelitis

In most cases of poliomyelitis, motor neuron death is extensive. In mild cases primarily involving one limb, the pattern of neuron death has not been fully determined. Nine mildly affected patients were studied systematically for electrophysiologic evidence of denervation by sampling one muscle in each limb. Fiber density was found to be increased in all but one muscle. Needle electromyography and turns and amplitude plots of the interference pattern were abnormal in all muscles in weak limbs and the majority of muscles in unaffected limbs. Turns: amplitude ratios were lower in muscles in weak limbs and greater in muscles in unaffected limbs in a pattern suggesting a horizontal gradation of motor neuron death across the spinal cord. This may be attributed to axonal transport of the virus. The horizontal pattern of sub clinical involvement in mild cases of poliomyelitis was compared and found to be similar to reported patterns of progression of limb weakness in amyotrophic lateral sclerosis type motor neuron disease.

Spatial organization of the haversian bone in man

The osteons in all human long bones are grouped in two helical antirotary systems of opposite oblique directions, situated in the contralateral walls of the diaphysis. Several arguments support the hypothesis that this special architecture arises from functional adaptations and that it depends on the orientation of the first principal stress. A new macroscopic method based on the filling of vascular canals of the undecalcified, polished bone with India-ink enabled us to study the spatial architecture of the haversian bone in the entire diaphysis. The osteon directions in normal and atypical femurs was compared with the direction of the first principal stresses, determined analytically in a cylindrical tube model of the diaphysis subjected to a combination of bending, torsion and compression. Under combined loading with the bending moment in the frontal plane to the medial side and with the torque moment in the sense of external rotation, the direction of the first principal stresses corresponded with the direction of osteons in the diaphysis of the femur. In both cases, the first principal stresses, as well as the osteons, were oriented in the opposite oblique direction in the medial and lateral walls of the model and of the bones. Between the two oblique fields a sharp boundary with an atypical organization of the principal stresses and osteons existed. In atypical femurs the osteonal orientation was longitudinal (likely unloaded femurs) or rotated 90 degrees (markedly anteriorly convex femurs). These observations support the hypothesis of a causal relation between the loading mode and the dominant osteonal direction. The organization of the haversian bone seems a typical example of functional adaptation.

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

We completed a prospective, population-based cohort study of polio survivors in Olmsted County, Minnesota, between 1986 and 1993. We identified 50 individuals who had had paralytic polio between 1935 and 1960, as representative of all 300 cases of paralytic polio in the county. We completed detailed quantitative clinical and electrophysiologic studies at entry and after 5 years. These studies demonstrated stable neuromuscular function within the cohort, although 60% of the individuals were symptomatic. In two-thirds of the symptomatic patients, the causes of their symptoms were unrelated to earlier polio. For the 20% of patients who had unexplained muscle pain, perception of weakness, and fatigue, a mechanical disorder most likely underlies their symptoms.

Spontaneous CNS remyelination in beta 2 microglobulin-deficient mice following virus-induced demyelination

Animal models with selective genetic immunodeficiencies are useful tools to identify pathogenic mechanisms of disease. Resistant (C57BL/6F 129/J) (H-2b) mice are rendered susceptible to Theiler's murine encephalomyelitis virus-induced demyelination by genetic disruption of the beta 2 microglobulin gene [beta 2 m(-l-)]. The absence of beta 2 m prevents the expression of major histocompatibility complex class I molecules and normal levels of functional CD8+ T cells. We tested whether genetic depletion of beta 2 m would permit CNS remyelination after chronic demyelination induced by the Daniel's strain of Theiler's virus. In contrast to the minimal spontaneous remyelination observed in SJL/J mice after infection with the Daniel's strain of Theiler's virus, chronically infected beta 2 m(-I-) mice showed extensive and progressive spontaneous CNS remyelination at 6, 12, and 18 months after infection. Spontaneous remyelination by both oligodendrocytes and Schwann cells occurred despite the presence of persistent virus antigen and RNA, but was associated with diminished virus-specific humoral and delayed-type hypersensitivity responses. These experiments support the hypothesis that the immune response inhibits myelin regeneration after virus-induced CNS demyelination.

Mode of spread to and within the central nervous system after oral infection of neonatal mice with the DA strain of Theiler's murine encephalomyelitis virus

Theiler's murine encephalomyelitis virus is a neurotropic enterovirus known to cause biphasic neural disease after intracerebral inoculation into adult mice. The present study characterizes a neonatal mouse model with a high disease incidence for the study of the acute phase of the pathogenesis of the DA strain of Theiler's murine encephalomyelitis virus after oral infection. The route of viral spread to and within the central nervous system (CNS) was determined by examining the kinetics of viral replication in various organs and by performing histopathological analysis. Viral antigen was detected widely in the neonatal CNS, mainly in the gray matter, and it was asymmetrical and multifocal in its distribution, with considerable variation in lesion distribution from animal to animal. Necrotizing lesions appeared to expand by direct extension from infected cells to their close neighbors, with a general disregard of neuroanatomical boundaries. The diencephalon showed particular susceptibility to viral infection. Other areas of the CNS, including the cerebellum and dentate gyrus of the hippocampus, were consistently spared. Neurons with axons extending peripherally to other organs or receiving direct input from the peripheral nervous system were not preferentially affected. The kinetics of viral replication in the liver, spleen, and CNS and the histopathological findings indicate that viral entry to the CNS is via a direct hematogenous route in orally infected neonatal mice and that the disease then progresses within the CNS mainly by direct extension from initial foci.

Contractile properties in single muscle fibres from chronically overused motor units in relation to motoneuron firing properties in prior polio patients

The relation between motoneuron firing rate in vivo and maximum velocity of unloaded shortening (Vmax) and myosin isoform composition in single chemically skinned muscle fibres was investigated in chronically overused motor units. Ten patients with loss of a large proportion of the motoneuron pool due to a prior polio lesion and compensatory overuse of residual neurones were studied and compared with normal individuals. The tibialis anterior muscle (TA) was chosen and prior polio patients who used all residual TA motor units at high rates during the normal step cycle were selected. In prior polio patients, all motor units fired at approximately 40 Hz when maximum voluntary force was reached. A common firing rate of 30 Hz yielded 70-90% maximum force. In normal subjects, on the other hand, maximum TA force was reached when low threshold units fired at 25-30 Hz and high threshold units at 50 Hz. Myosin heavy chain (MHC) and light chain (MLC) isoforms were resolved by 6% and 12% sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), respectively, and quantified densitometrically. In the whole biopsy cross-sections, types I, IIA and IIB MHC proportions were 97, 3 and 0% in a typical prior polio patient and 65, 25 and 10% in an age- and sex-matched control subject. Vmax differed significantly (p < 0.001) between type I fibres from the patient (0.54 +/- 0.12 ML/s) and the control subject (0.29 +/- 0.08 ML/s). The composition and relative contents of essential and regulatory MLC isoforms differed in single type I MHC fibres from the control subject and prior polio patient. 65% of the fibres co-expressed the fast and slow isoform of the regulatory light chain (MLC2) in the patient, while this combination was only observed in one of the control type I fibres. All prior polio fibres with a Vmax higher than 0.45 ML/s, except one, co-expressed MLC2s and MLC2f and the only control fibre co-expressing the slow and fast MLC2 isoform had the highest Vmax (0.50 ML/s) among control fibres. On the other hand, a high relative content of MLC3 was not associated with a high Vmax in type I MHC fibres. It is suggested that the composition of fast and slow isoforms of MLC2 has a significant modulatory influence on Vmax within type I MHC fibres. This combination of MLCs and high Vmax in type I MHC fibres is probably induced by chronic motor unit overuse and an altered motoneuron firing pattern.

The neurovirulent GDVII strain of Theiler's virus can replicate in glial cells

The distribution, spread, neuropathology, tropism, and persistence of the neurovirulent GDVII strain of Theiler's virus in the central nervous system (CNS) was investigated in mice susceptible and resistant to chronic demyelinating infection with TO strains. Following intracerebral inoculation, the virus spread rapidly to specific areas of the CNS. There were, however, specific structures in which infection was consistently undetectable. Virus spread both between adjacent cell bodies and along neuronal pathways. The distribution of the infection was dependent on the site of inoculation. The majority of viral RNA-positive cells were neurons. Many astrocytes were also positive. Infection of both of these cell types was lytic. In contrast, viral RNA-positive oligodendrocytes were rare and were observed only in well-established areas of infection. The majority of oligodendrocytes in these areas were viral RNA negative and were often the major cell type remaining; however, occasional destruction of these cells was observed. No differences in any of the above parameters were observed between CBA and BALB/c mice, susceptible and resistant, respectively, to chronic CNS demyelinating infection with TO strains of Theiler's virus. By using Southern blot hybridization to detect reverse-transcribed PCR-amplified viral RNA sequences, no virus persistence could be detected in the CNS of immunized mice surviving infection with GDVII. In conclusion, the GDVII strain of Theiler's murine encephalomyelitis virus cannot persist in the CNS, but this is not consequent upon an inability to infect glial cells, including oligodendrocytes.

Dynamic electromyography and muscle biopsy changes in a 4-year follow-up: study of patients with a history of polio

Eighteen patients who had had polio 29-56 years prior to the first investigation were studied on two occasions, 4 years apart. Isokinetic and isometric strength measurements and Macro EMG were performed in 28 legs. Muscle biopsy specimens were obtained on both occasions from 11 legs. On average the muscle strength was 56% of control values at the first examination, and decreased by another 8% during the observation period. The muscle fiber area was increased compared to that of controls and did not change significantly. Macro EMG, comprising muscle fiber area and number of muscle fibers, and/or single fiber EMG showed clear signs of reinnervation in all legs. The motor units at the first examination were increased 11-fold, on average, compared with age-matched control values. During the observation period, reinnervation continued and the size of motor units increased by another 56% as a result of ongoing denervation, that is, loss of neurons. This compensation was particularly pronounced in patients with stable conditions. The parameters studied did not reveal any definite pattern predicting future development of new muscle weakness in individual subjects.

[Orthoses in patients with poliomyelitis]

Poliomyelitis, in spite of vaccination, is still a problem: in the third world as well as for the victims of the epidemics of the first half of this century, who now, becoming older, have growing difficulties to overcome their paralyses. They needed and still need orthoses for walking. How do they manage? And what can orthopedic technique offer them today?

Theiler's virus infection of 129Sv mice that lack the interferon alpha/beta or interferon gamma receptors

The Daniels strain of Theiler's virus causes a persistent infection of the white matter of spinal cord of susceptible mice, with chronic inflammation and primary demyelination. Inbred 129Sv mice are resistant to this infection; they present with mild encephalomyelitis and clear the infection within a matter of days. A very different outcome was observed with inbred 129Sv mice whose receptors for interferon alpha/beta or interferon gamma had been inactivated by homologous recombination. The former presented severe encephalomyelitis with acute infection of neurons, particularly in brain and hippocampus, and extensive infection with necrosis of the choroid plexus. Most animals died of this acute disease. The latter, presented the same early encephalomyelitis as the control 129Sv mice. However, they remained persistently infected and developed a very severe late infection of the white matter with extensive primary demyelination. This late disease looked like an exacerbated form of the chronic demyelinating disease observed in susceptible inbred mice such as the SJL/J or FVB strains. Our results show that the two interferon systems play nonredundant roles in the resistance of the 129Sv mouse to the infection by Theiler's virus. They also lend support to the notion that the Ifg gene is involved in the resistance/susceptibility of inbred strains of mice to persistent infection by this picornavirus.

Comparison of different mechanical ventilators for patients with poliomyelitis

Poliomyelitis can affect patients with severe hypoxia and hypercapnia. Historically, most of these patients were supported by mechanical ventilation via tracheostomy. However, this procedure can lead to serious complications. Subsequently, non-invasive alternative procedures have been introduced that provide mechanical respiratory support; these include negative pressure ventilators and positive pressure ventilation via a nasal, oral, and oronasal interface. Although these ventilators are effective, various limitations have been noted. The strapless oronasal interface positive pressure ventilator appears to have the fewest limitations, and through the use of advanced dental techniques and improved dental materials, this ventilator is easily fabricated and has been noted by patients to be more comfortable.

Clinical observations on acute poliomyelitis

During the years of the polio epidemics, most patients with the poliovirus had little or no paralysis. In those with paralytic polio, the extent of involvement of the anterior horn cells was often underestimated. Thus, patients with post-polio syndrome now often report that a limb was uninvolved; however, the original record will show clear evidence of initial paralysis that improved so that the patient no longer recognized the weakness. The epidemics were associated with great anxiety involving the patients, their families and all of society. Treatment was for the most part ineffective and was sometimes confused or inappropriate. Patients developed coping techniques that have been singularly useful and effective. These coping techniques often include strategies that require maximal athletic development of little-used muscles. The coping techniques developed by post-polio patients would be of great benefit to patients with other forms of disability. Review of the medical histories, biographies, and autobiographies of patients who had severe disability because of poliomyelitis reveals that they adopted firm convictions about their disease and their recovery. We must be aware of these convictions if we are to treat their later disabilities. These convictions include the belief that their condition can only improve, that their improvement is related primarily to the willingness of the patient to engage in exercise, and that improvement is more a thing of the spirit than of medication. Associated with this conviction is denial--often concurred with by the family--of the extent of the disability. Furthermore, the confusion of physicians that patients witnessed during the great epidemics suggests to patients that physicians can be of little help to them now. Convictions that were invaluable to patients who were young and vigorous become a liability when aging and progressive weakness supervene. Patients who had adapted to muscle weakness through great physical and emotional effort are unable to continue functions they had regained. However, such patients cannot accept that they do not continue to improve. Some become depressed, but this is unusual.

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.