Polio

Polio

Infection by RNA virus of the enterovirus group (3 types). Now an insignificant disease in Western/Industrialised countries – last major outbreaks in 1940’s and 1950’s due to develop to use of Sabin and Salk vaccines. Estimated to be about 275 000 new cases a year in developing countries. Starts as a febrile illness and can result in asymmetric paralysis. Most patients seen today with this have long standing deformities from under or over treatment of early disease. Transmitted by oral-faecal route; incubation of 7-10 days; subclinical infections are common (90% asymptomatic); poor sanitation and hygiene is considered a major factor in outbreaks.

Due to death of anterior horn cells from an acute viral infection  partial or complete paralysis of muscles supplied by motor unit that have been dennervated by necrosis (weakness does not develop until 50-60% of lower motor neurons are destroyed).

Clinical features:
Subclinical infections are common. Two forms – paralytic and non-paralytic.
Fever, drowsiness, neck stiffness (in both forms) – in paralytic form (occurs in a minority)  muscle pain, progresses to asymmetrical muscle weakness/paralysis  partial recovery of muscle strength. Respiratory muscles involved in severe cases. Flaccid paralysis of anterior muscles; muscle wasting; contractures common; leg length differences

The degree of recovery depends on the number of motor neurons that recover from initial infection. Muscle strength and functional recovery occurs by 3 processes:
1) Re-innervation of muscle fibres by axon sprouting of viable nerves
2) Hypertrophy of muscle fibres that remain innervated
3) Motor learning (compensatory processes  may mask full extent of true recovery)

Involvement of foot:
Pes cavus, inverted foot, claw toes, equinus, trigger hallux, retracted lessor toes.
Fragile skin with trophic changes. Pressure lesions
Many foot deformities may be due to residual affects following tendon transfer surgery.
46/318 of those with polio (median age 54yrs) were seeing a Podiatrist in one study .

Management:
Supportive; may need respirator for respiratory muscle paralysis.

Management of foot:
Depend on deformity. AFO’s; custom footwear; molded orthoses (eg EVA) for pressure relief
Skin care; lesion reduction

iron lungs

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