Poliomyelitis, more commonly known as just polio, is a once common but now rare disease resulting from infection by the poliovirus. Most infected individuals develop no or non-serious symptoms as a result of the infection, but ~1% will develop life-altering disability (paralysis) due to the destruction of motor neurons.
Although once a common disease worldwide, polio is now virtually non-existent in the Western hemisphere due to immunisation. Only 1,579 cases were confirmed in 2009 worldwide 2. The virus is most commonly spread via the faecal-oral route. However, oral-oral transmission is possible.
Two forms of poliomyelitis can occur after infection with poliovirus 5:
- form of aseptic meningitis
- flu-like prodrome followed by muscular stiffness +/- paresthesia
- biphasic illness with symptoms of non-septic meningitis, followed by a few days of being symptoms free then paralysis develops
- lower limbs more often affected than upper limbs
Conventional radiograph and CT
With acute infection, no radiographic features are typically evident.
Chronically, findings are characterised by atrophy of involved areas, including of bone and muscle, which may be similar to other neuromuscular disorders. The extent of fatty muscle atrophy and/or bone atrophy may be striking. Often there are associated deformities due to involved muscles, most commonly flexion, abduction and external rotation at hip joint.
Neuroimaging may reveal ALS-like abnormalities in the affected areas of the ventral motor tracts in the spine and/or motor cortex, which are characteristically hyperintense on T2WI 3,4.
Extensive fatty muscle atrophy may be seen in affected areas of the musculoskeletal system, which may be unilateral or bilateral.
Treatment and prognosis
In the modern Western world, poliomyelitis is prevented by vaccination. As no cure for poliomyelitis itself is available, treatment is supportive and designed to prevent complications and a quick recovery. Antibiotics are given to prevent infection of weakened muscles. Often an extended period of rehabilitation is necessary to regain full function of affected body parts 6.
Prognosis depends on the extent of motor neuron destruction by the time treatment is started and varies from complete recovery to severely debilitating paralysis 7.
History and etymology
"Poliomyelitis" derives from the Greek πολιός ("grey") and μνελός ("marrow"), indicating how the disease affects the spinal cord grey matter. J Heine first described it in 1840 8 and the epidemic form described by Oskar Medin in 1890. Hence, it is sometimes known as Heine-Medin disease 9.
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- 9. Pearce JM. Poliomyelitis (Heine-Medin disease). J. Neurol. Neurosurg. Psychiatr. 2005;76 (1): 128. doi:10.1136/jnnp.2003.028548 - Free text at pubmed - Pubmed citation