Poliomyelitis - Causes, Symptoms and Treatments:
Poliomyelitis, also called polio or infantile paralysis, is an acute communicable disease caused by the poliovirus and ranges in severity from in apparent infection to fatal paralytic illness. First recognized in 1840, poliomyelitis became epidemic in Norway and Sweden in 1905. Outbreaks reached pandemic proportions in Europe, North America, Australia, and New Zealand during the first half of this century. Incidence peaked during the 1940s and early 1950s, and led to the development of the Salk vaccine.
Minor polio outbreaks still occur, usually among nonimmunized groups such as the Amish of Pennsylvania. The disease usually strikes during the summer and fall.
Once confined mainly to infants and children, poliomyelitis mostly occurs today in people over age 15. Adults and girls are at greater risk for infection; boys, for paralysis.
If the central nervous system (CNS) is spared, the prognosis is excellent. However, CNS infection can cause paralysis and death. The mortality for all types of poliomyelitis is 5% to 10%.
Causes of Poliomyelitis:
The poliovirus has three antigenically distinct stereotypes I, II, and III - all of which cause poliomyelitis. These viruses are found worldwide and are transmitted from person to person by direct contact with infected oropharyngeal secretions or feces. The incubation period ranges front 5 to 35 days- 7 to 14 days on average.
The virus usually enters the body through the alimentary tract, multiplies in the oropharynx and lower intestinal tract, then spreads to regional lymph nodes and the blood. Factors that increase the risk of paralysis include pregnancy; old age; localized trauma, such as a recent tonsillectomy, tooth extraction, or inoculation; and unusual physical exertion at or just before the clinical onset of poliomyelitis.
Signs and symptoms of Poliomyelitis:
Manifestations of poliomyelitis follow three basic patterns. Inapparent (subclinical) infections constitute 95% of all poliovirus infections. Abortive poliomyelitis (minor illness), which accounts for 4% to 8% of all cases, causes slight fever, malaise, headache, sore throat, inflamed pharynx, and vomiting. The patient usually recovers within 72 hours. Most cases of inapparent or abortive poliomyelitis go unnoticed.
Major poliomyelitis, however, involves the CNS and takes two forms: nonparalytic and paralytic. Children commonly show a biphasic course, in which the onset of major illness occurs after recovery from the minor illness stage. Nonparalytic poliomyelitis produces moderate fever, headache, vomiting, lethargy, irritability, and pains in the neck, back, arms, legs, and abdomen. It also causes muscle tenderness, weakness, and spasms in the extensors of the neck and back, and sometimes in the hamstring and other muscles. (These spasms may be observed during maximum range-of-motion exercises.) Nonparalytic polio usually lasts about a week, with meningeal irritation persisting for about 2 weeks.
Paralytic poliomyelitis usually develops within 5 to 7 days of the onset of fever. The patient displays symptoms similar to those of nonparalytic poliomyelitis, with asymmetrical weakness of various muscles, loss of superficial and deep reflexes, paresthesia, hypersensitivity to touch, urine retention, constipation, and abdominal distention. The extent of paralysis depends on the level of the spinal cord lesions, which may be cervical, thoracic, or lumbar.
Resistance to neck flexion is characteristic in nonparalytic and paralytic poliomyelitis. The patient will "tripod"extend his arms behind him for support - when he sits up. He'll display Hoyne's sign-his head will fall back when he is supine and his shoulders are elevated. From a supine position, he won't be able to raise his legs a full 90 degrees. Paralytic poliomyelitis also causes positive Kernig's and Brudzinski's signs.
When the disease affects the medulla of the brain, it's called bulbar paralytic poliomyelitis, which is the most perilous type. This form affects the respiratory muscle nerves, which leads to respiratory paralysis, and weakens the muscles supplied by the cranial nerves (particularly the IX and X), producing symptoms of encephalitis. Other signs and symptoms include facial weakness, diplopia, dysphasia, difficulty in chewing, inability to swallow or expel saliva, regurgitation of food through the nasal passages, and dyspnea as well as abnormal respiratory rate, depth, and rhythm, which may lead to respiratory arrest. Fatal pulmonary edema and shock are possible.
Complications - many of which result from prolonged immobility and respiratory muscle failure-include hypertension, urinary tract infection, urolithiasis, atelectasis, pneumonia, myocarditis, cor pulmonale, skeletal and soft -tissue deformities, and paralytic ileus.
Diagnosis of Poliomyelitis:
Diagnosis requires isolation of the poliovirus from throat washings early in the disease, from stools throughout the disease, and from cerebrospinal fluid (CSF) cultures in CNS infection.
Coxsackievirus and echovirus infections must be ruled out. Convalescent serum antibody titers four times greater than acute titers support a diagnosis of poliomyelitis. Routine laboratory tests are usually within normal limits; however, CSF pressure and protein levels may be slightly increased and white blood cell count elevated initially, mostly due to polymorphonuclear leukocytes, which constitute 50% to 90% of the total count. Thereafter, mononuclear cells constitute most of the diminished number of cells.
Rarely, certain group A and B coxsackieviruses (especially A7), several echoviruses, and enterovirus type 71 may produce muscle weakness or paralysis that cannot be clinically differentiated from paralytic poliomyelitis. Guillain-Barre syndrome is often confused with paralytic poliomyelitis. CNS involvement due to mumps or herpesviruses, meningoencephalitis due to arboviruses in certain geographic areas, tuberculous meningitis, or brain abscess should also be considered.
Treatment of Poliomyelitis:
Treatment is supportive and includes analgesics to ease headache, back pain, and leg spasms; morphine is contraindicated because of the danger of additional respiratory suppression. Moist heat applications may also reduce muscle spasm and pain.
Bed rest is necessary only until extreme discomfort subsides; in paralytic polio, this may take a long time. Paralytic polio also requires long-term rehabilitation using physical therapy, braces, corrective shoes and, in some cases, orthopedic surgery.
Special cansiderations of Poliomyelitis:
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