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AUTHOR INFORMATION
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Section 1 of 10
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| Author: Flor
M Muņiz, MD, Staff Physician, Department of Physical
Medicine and Rehabilitation, Thomas Jefferson
University
Coauthor(s): Gerald
Herbison, MD, Clinical Professor, Department of
Physical Medicine and Rehabilitation, Thomas Jefferson University
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| Flor M Muņiz, MD, is a member of the following medical
societies: American Medical
Association
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| Editor(s): Martin K Childers, DO, Associate
Professor, Department of Physical Medicine and Rehabilitation,
University of Missouri School of Medicine; Francisco
Talavera, PharmD, PhD, Senior Pharmacy Editor, Pharmacy,
eMedicine; Kat Kolaski, MD, Assistant Professor,
Departments of Orthopedics and Pediatrics, Wake Forest University
School of Medicine; Kelly L Allen, MD, Consulting
Staff, Department of Physical Medicine and Rehabilitation, Lourdes
Regional Rehabilitation Center, Our Lady of Lourdes Medical Center;
and Denise I Campagnolo, MD, MS, Director of
Clinical Trials Research, Barrow Neurological Institute, St Joseph's
Hospital |
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INTRODUCTION |
Section 2 of 10   |
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Background: Accepted
criteria for diagnosis of postpolio syndrome (PPS) are a prior history of
poliomyelitis, a stable period after recovery, a residual deficit of the
initial polio, new muscle weakness, and, sometimes, new muscle atrophy.
Fatigue and muscle pain need not be present to meet the criteria for the
syndrome.
Pathophysiology: One possible cause of PPS is
decompensation of a chronic denervation and reinnervation process to the
extent that the remaining healthy motor neurons can no longer maintain new
sprouts; thus, denervation exceeds reinnervation.
A second possible mechanism for PPS is motor neuronal loss due to
reactivation of a persistent latent virus. In addition to muscle atrophy
and denervation, foci of perivascular and interstitial inflammatory cells
have been found on 50% of biopsies of patients with PPS. Activated T cells
and immunoglobulin M and immunoglobulin G antibodies specific for
gangliosides also have been found.
Another possibility is an infection of the polio survivor's motor
neurons by an enterovirus that is different from the one responsible for
the patient's polio. Others sources hypothesize that PPS is merely the
loss of strength due to the usual stresses of aging and weight gain. In
patients with PPS, these processes occur in muscles that already are weak,
so the consequences are more noticeable compared with those of patients
who have not had polio.
Frequency:
- In the US: The incidence of PPS in previous acute
polio patients ranges from approximately 22-68%. PPS is estimated to
occur in 28.5% of persons who had paralytic polio. The current
prevalence is approximately 1.6 million cases. Suggestions have been
made that 100% of polio survivors, if tracked for a long period, can
develop some symptoms of PPS.
Age: Onset is approximately 30 years after the acute
polio.
History: Symptoms usually
appear earlier in patients who have very severe residual weakness, early
bulbar respiratory difficulty in the acute illness, and those who were
older when they contracted acute polio. PPS symptoms tend to occur first
in the weaker muscles.
- Fatigue: In individuals without polio or PPS, the functional
consequences of aging and loss of motor units may be unnoticeable until
a very advanced age. In the individual with PPS, any further loss of
strength may be more readily apparent. In contrast to patients with
chronic fatigue syndrome, postpolio fatigue is prominent in the early
hours of the afternoon and decreases after brief periods of rest.
PPS-related fatigue usually does not prevent patients from
working.
- Central
- Pathogenesis can include chronic pain, type A personality,
depression, dysfunctional reticular-activated system, sleep
disorders, and respiratory dysfunction.
- PPS produces somnolence and difficulty in concentrating and
remembering.
- Peripheral
- Pathogenesis may be metabolic exhaustion of the enlarged motor
units, neuromuscular junction transmission defects, scarring within
the motor neurons, or loss of motor units due to aging.
- PPS produces decreased muscular endurance and increased muscular
fatigability.
- Weakness
- A number of functional etiologies for weakness have been
hypothesized, including disuse, overuse, and chronic weakness, as well
as weight gain.
- Asymmetric and scattered weakness may be present.
- Some authors have found evidence that previously unaffected
muscles later become weak; in these cases, they discovered that the
patient was unaware or had not been told that the particular muscle
had been affected during the acute episode.
- Muscle pain
- Deep aching pain may be a component of a myofascial pain syndrome
or fibromyalgia.
- This feature is extremely prevalent in PPS.
- Gait disturbance: Difficulty with gait is caused by progressive
weakness, pain, osteoarthritis, or joint instability; it is common in
patients who previously used assistive devices but later discarded
them.
- Respiratory problems
- Respiratory disorders are most prevalent in patients with residual
respiratory muscle weakness.
- These changes cause chronic microatelectasis, diminished pulmonary
compliance, increased chest wall tightness, chronic alveolar
hypoventilation, decreased cough and expiratory flow, and decreased
clearing of secretions.
- The new respiratory difficulties are not only related to new
respiratory muscle weakness but also to scoliosis, pulmonary
emphysema, cardiovascular insufficiency, or poor posture.
- A central component also may occur because acute bulbar polio
often affects the medullary structures, including the reticular
formation and sleep regulatory system.
- Swallowing problems
- These difficulties can occur in patients with bulbar and nonbulbar
postpolio.
- Subclinical asymmetrical weakness in the pharyngeal constrictor
muscles is almost always present in all postpolio muscular atrophy
patients, including those who do not complain of new swallowing
difficulties.
- Autonomic dysfunction: The cause is unclear; the peripheral
component could include muscular atrophy and, therefore, diminished heat
production.
- This disorder is not uncommon in patients left with residual
bulbar dysfunction or severe respiratory compromise.
- Sleep apnea appears to be due to a combination of the following:
- Central apnea, due to a residual dysfunction of the surviving
bulbar reticular neurons
- Obstructive apnea, due to pharyngeal weakness and increased
musculoskeletal deformities from scoliosis or emphysema
- Postpolio muscular atrophy, resulting in diminished muscle
strength of the respiratory, intercostal, and abdominal muscle
groups
- Another possible symptom in some patients with PPS is the flat
back syndrome, which consists of the inability to stand erect because
of forward flexion of the trunk and pain in the low back and
legs.
- The flat back syndrome typically occurs in patients with
diminished lumbar lordosis as a result of instrumentation of the spine
for scoliosis, vertebral fracture, or degenerative joint
disease.
- The trunk extensor musculature plays an essential role in
maintaining upright posture, and it may be that PPS-related weakness
in this musculature represents a major contributing factor to the flat
back syndrome in these patients.
Physical: Progressive weakness and atrophy may be
observed in muscles that were affected initially by the poliovirus or in
muscles that were spared clinically, which tends to happen in an
asymmetric distribution. Fasciculations sometimes can be observed in
atrophic muscles, as a result of the lower motor neuron injury.
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DIFFERENTIALS |
Section 4 of 10 |
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Amyotrophic Lateral
Sclerosis
Hypothyroid Myopathy
Multiple
Sclerosis
Other Problems to be Considered:
Anemia
Chronic infection
Collagen
disorders
Deconditioning
Depression
Hypothyroidism
Infectious
myopathy
Myasthenia gravis
Weakness due to aging
Weight
gain
Investigators initially believed that poliovirus could
cause amyotrophic lateral sclerosis (ALS), but there is no evidence of
this risk. Studies that show an association between both pathologies are
infrequent and are greatly outnumbered by negative reports. The role, if
any, of nonparalytic polio and polio vaccines to ALS is not clear. With
such a high proportion of the population having antibodies to polio, it
may not be feasible to differentiate ALS with respect to the presence or
absence of polio antibodies. Still, further long-term studies for both the
classical and Western Pacific forms of ALS with respect to past polio
outbreaks are desirable.
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Lab Studies:
- Obtain the following laboratory studies to exclude other
conditions:
Imaging Studies:
- CT scan and MRI can be ordered to rule out other possible diagnoses
or structural neurologic processes (eg, stroke, multiple sclerosis,
tumor).
Other Tests:
- Electrodiagnostic studies are used to rule out other neurologic or
neuromuscular disorders in the differential diagnosis. The following 5
phases of electrodiagnostic study findings of anterior horn cell disease
have been recognized:
- Acute myelitis (first month)
- Late changes during functional stability (eg, fasciculations,
positive waves, fibrillations, increased amplitude and duration of
motor unit potentials)
- In PPS, sensory conductions should be normal; motor conductions
usually are normal but may be slow. In late stages, amplitude decreases
significantly.
- Single fiber electromyography: Increased jitter and blocking is
noted. This observation is related to the fact that, in PPS, variable
degrees and different types of neuromuscular transmission failure have
been found in affected patients who had associated histologic signs of
reinnervation in their muscle biopsies.
- Functional and structural abnormalities of neuromuscular junction
are common but not necessary conditions for the diagnosis of PPS. These
neuromuscular junction transmission defects typically are observed in
the early stage of the neuronal degeneration that produces PPS. Whether
neuromuscular junction transmission defects increase with the passage of
time is unclear.
Histologic Findings: In the
chronically denervated muscles of patients with PPS, there are secondary
myopathic features, including endomysial inflammation and rare vacuolated
fibers.
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TREATMENT |
Section 6 of 10 |
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Rehabilitation Program:
- Physical Therapy: The basic management principles
for individuals with PPS include energy conservation and pacing one's
activities. Although basic, these activity modifications may be
difficult for some patients to accept.
Reports on exercises are conflicting, but the key factor seems to be
exercise intensity. Strengthening exercises should be nonfatiguing. A
specific suggestion is to exercise every other day, and the perceived
rate of exertion should be less than "very hard." Loads should be held
for only 4-5 seconds, and there should be a 10-second rest between bouts
and a 5-minute rest between sets. The patient should perform about 3
sets of 5-10 repetitions.
In addition to specifying exercises for those body areas experiencing
the deleterious effects of disuse, the exercise prescription also should
consider how to protect (1) muscles and joints that are experiencing the
adverse effects of overuse and (2) body areas with very significant
chronic weakness (generally, areas where the muscles have less than
antigravity strength on manual muscle testing).
Results of these exercises vary. Strengthening programs performed as
described show a 60% increase on isokinetic strength, improved
cardiorespiratory status, no decline in strength in 6-12 months, and 5%
increase in isometric strength.
Electrical stimulation has been used to strengthen weakened muscles
or to re-educate muscles weakened through disuse, as well as to decrease
pain.
For myofascial pain, consider heat, electrical stimulation, trigger
point injections, stretching exercises, biofeedback, muscle relaxation
exercises, or static magnetic fields for trigger points.
For gait disturbances, assistive devices can be used, but sometimes
patients refuse because of the philosophy of "not giving in." Treatment
also can involve limitation of ambulation to shorter distances and the
use of orthotics for joint protection.
- Occupational Therapy: Patients usually benefit from
different adaptive techniques and equipment to perform any activities of
daily living, as well as education and energy conservation techniques.
- Speech Therapy: Speech evaluation usually is
recommended with any suggestion of swallowing problems. The therapist
teaches the patient about different techniques to improve his/her
swallowing function.
Consultations:
- When the patient reports respiratory problems, a full pulmonary
evaluation may be required.
- Sometimes, the patient may even need mechanical respiratory
support.
- A sleep evaluation may be necessary for suspected sleep
apnea.
- Orthopedists: The patient may present with various joint deformities
that may require orthoses and sometimes even surgery.
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MEDICATION |
Section 7 of 10 |
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Medications, most of which address
fatigue, have been used with only partial success in patients with
PPS.
Drug Category: Anticholinesterases -- Some
authors have reported that one of the mechanisms for production of fatigue
may be related to neuromuscular junction transmission deficits; however,
treatment with anticholinesterases has been successful in only half of the
cases; this low success rate has been attributed to the variety of
neuromuscular junction defects believed to be present in PPS. The
mechanism of response to anticholinesterases also is unclear because some
patients experience improvement in muscular strength, rather than
improvement in fatigability.
Drug Name
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Pyridostigmine (Mestinon) -- Acts
in smooth muscle, the CNS, and secretory glands where it blocks
action of acetylcholine at parasympathetic sites and facilitates
transmission of impulses across the myoneural junction.
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| Adult Dose |
60 mg PO tid (in experimentation)
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| Pediatric Dose |
Not established
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| Contraindications |
Documented hypersensitivity; GI or
GU obstruction; cardiac arrhythmia, asthma, and increased bronchial
secretions
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| Interactions |
Pyridostigmine increases effects of
depolarizing neuromuscular blockers; increases toxicity of
edrophonium
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| Pregnancy |
C - Safety for use during pregnancy
has not been established.
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| Precautions |
Caution in bronchial asthma and
those receiving a cardiac glycoside; overdose may cause cholinergic
crisis, which may be fatal; atropine IV should be readily available
for treatment of cholinergic reactions | Drug Category: Antivirals -- Contradictory
information on use. No significant improvement found by some authors
compared with placebo.
Drug Name
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Amantadine (Symmetrel) -- May act
to release dopamine from dopaminergic terminals and other central
sites.
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| Adult Dose |
Not established
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| Pediatric Dose |
Not established
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| Contraindications |
Documented hypersensitivity
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| Interactions |
Drugs with anticholinergic or CNS
stimulant activity increase amantadine toxicity; the concurrent
administration of hydrochlorothiazide plus triamterene with
amantadine may increase plasma concentrations
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| Pregnancy |
C - Safety for use during pregnancy
has not been established.
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| Precautions |
Caution in liver disease,
uncontrolled psychosis, eczematoid dermatitis, seizures, and
patients receiving CNS stimulant drugs; reduce dose in renal disease
when treating Parkinson disease; do not discontinue this medication
abruptly | Drug Category:
Corticosteroids -- Have been studied but with no good
results.
Drug Name
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Prednisone (Deltasone) -- Must be
metabolized to the active metabolite prednisolone for effect.
Conversion may be impaired in liver disease.
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| Adult Dose |
Not established
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| Pediatric Dose |
Not established
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| Contraindications |
Documented hypersensitivity; viral
infection; peptic ulcer disease; hepatic dysfunction; connective
tissue infections; fungal or tubercular skin infections; GI disease
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| Interactions |
Coadministration with estrogens may
decrease prednisone clearance; concurrent use with digoxin, may
cause digitalis toxicity secondary to hypokalemia; phenobarbital,
phenytoin, and rifampin may increase metabolism of glucocorticoids
(consider increasing maintenance dose); monitor for hypokalemia with
coadministration of diuretics
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| Pregnancy |
B - Usually safe but benefits must
outweigh the risks.
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| Precautions |
Abrupt discontinuation of
glucocorticoids may cause adrenal crisis; hyperglycemia, edema,
osteonecrosis, myopathy, peptic ulcer disease, hypokalemia,
osteoporosis, euphoria, psychosis, myasthenia gravis, growth
suppression, and infections may occur with glucocorticoid
use |
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FOLLOW-UP |
Section 8 of 10 |
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Prognosis:
- The symptoms of PPS are slowly progressive with periods of stability
from 3-10 years.
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MISCELLANEOUS |
Section 9 of 10 |
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Medical/Legal Pitfalls:
- PPS might be mistaken for any of the conditions described in the
differential diagnosis. Because of this possibility, failure to diagnose
PPS properly could end up with the physician administering medications
or treatments to the patient that do not correspond to the pathology
process, not improving his/her condition and possibly giving the patient
multiple adverse effects from the medications used.
Special Concerns:
- Certain psychological issues have been studied in relation to PPS,
including the following:
- Most studies reveal that depression is not related to PPS
symptomatology or the level of residual physical
disability.
- Type A behavior is significantly higher in the polio population
than in a control population.
- Overall, normal psychological and emotional functioning has been
found in patients with PPS, compared with controls.
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BIBLIOGRAPHY |
Section 10 of
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| NOTE:
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| Medicine is a constantly
changing science and not all therapies are clearly established. New
research changes drug and treatment therapies daily. The authors,
editors, and publisher of this journal have used their best efforts
to provide information that is up-to-date and accurate and is
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contraindications should be confirmed in the package insert. FULL DISCLAIMER
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Postpolio
Syndrome excerpt
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