Although the infection rate is extremely high, majority (95%) of infections are inapparent or asymptomatic (1).
- The ratio of inapparent to paralytic infections may be as high as 1,000:1 in children and 75:1 in adults (2)
After the incubation period of three to twenty one days, poliomyelitis symptoms may manifest from a fever to aseptic meningitis or paralysis.
- abortive poliomyelitis
- patient may present with upper respiratory tract infection (sore throat and fever), gastrointestinal disturbances (nausea, vomiting, abdominal pain, constipation) and influenza like illness
- complete recovery occurs in less than one week
- nonparalytic aseptic meningitis
- stiffness of the neck, back, and/or legs is seen several days after a prodrome similar to that of minor illness
- complete recovery occurs after 2 to 10 days
- paralytic infection
- occurs in less than 1% of all infections (3)
- a biphasic prodrome may be observed (specially in children) where initial minor symptoms is separated by a 1- to 7-day period from more major symptoms (1)
- generally classified into spinal, bulbar and bulbospinal types
- spinal poliomyelitis
- most common form
- begins with symptoms of meningitis
- this is followed by severe myalgia and motor (spasms, fasciculations) symptoms.
- weakness and paralysis sets in after 1-2 days and is classically an asymmetrical, flaccid paralysis that peaks at 48 hours after onset
- proximal muscle groups are involved more than the distal muscle groups
- lower limbs are mainly affected
- bulbar poliomyelitis
- patient may present with vasomotor disturbances such as hypertension, hypotension and circulatory collapse, autonomic dysfunction, dysphagia, dysphonia, and respiratory failure (4)
- bulbospinal poliomyelitis
- a combination of bulbar and spinal forms
- sensation is unaffected by this condition
- rarely polio virus may cause an acute encephalitis which is clinically similar to other viral encephalitis (3,4)
When a badly- paralysed limb is picked up it has a floppy feel which, in the presence of normal sensation, is characteristic of the residual paralysis from poliomyelitis.
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