Background
Microbiology
- Single-stranded, positive-sense, unenveloped RNA virus in the family Picornaviridae, genus Enterovirus, species Enterovirus C
- Currently, the most common cause of poliomyelitis is oral vaccine-derived poliovirus
Pathophysiology
- Targets the spinal anterior horn cells
Clinical Manifestations
- 90-95% of cases are clinically inapparent; 4-8% are abortive after the prodrome; and only 1-2% proceed to major illness
- Incubation period of 9 to 12 days (range 5 to 35 days) before onset of prodrome
- Minor illness lasts a few days
- Fever, headache, sore throat, malaise, anorexia, vomiting, or abdominal pain
- Normal neurological exam
Spinal Paralytic Poliomyelitis
- 0.1% of all poliovirus infection
- 2 to 5 days after resolution of minor illness, onset of aseptic meningitis, with fever, headache, nuchal rigidity, vomiting, and a CSF pleocytosis
- Weakness and paralysis start within a few days
- Asymmetric, flaccid paralysis with increased DTRs
- Typically proximal more than distal muscles, and legs more than arms
- Typical pattern is one leg then one arm, or both legs then both arms
- Progresses to complete paralysis over 2 to 3 days
- Rarely sensory loss; if present, consider another diagnosis such as Guillain-Barré syndrome
Bulbar Paralytic Poliomyelitis
- Represents 5 to 25% of paralytic poliomyelitis during outbreaks
- Affects the cranial nerves, presenting with dysphagia, nasal speech, and dyspnea
- Pooling saliva
Polioencephalitis
- Uncommon
- Presents like any other cause of encephalitis
- Confusion, altered level of consciousness, and seizure
- May have spastic paralysis rather than flaccid
Postpoliomyelitis Syndrome
- See post-polio syndrome
- Median latency 36 years after an episode of paralytic poliomyelitis
- New onset weakness, pain, atrophy, and fatigue
- Can affect the respiratory muscles
Differential Diagnosis
- Paralytic poliomyelitis: other causes of acute flaccid paralysis
- Other enteroviruses, such as enterovirus A-71, enterovirus D-68
- West Nile virus
- Guillain-Barré syndrome, which would be symmetrical, bilateral ascending paralysis with loss of sensation, that progresses over 1 to 2 week and has minimal CSF pleocytosis with albuminocytologic dissociation
- Polioencephalitis: other causes of encephalitis
Diagnosis
- PCR is the only way to distinguish between wildtype polio and vaccine-derived
- Throat swabs during the first week of illness
- Feces for several weeks
- CSF not particularly sensitive, but is helpful when positive and should still be sent
- Acute and convalescent serology
Management
