Poliomyelitis is an acute inflammatory infection that affects
the lower motor neurons of the spinal cord and causes flaccid
paralysis, muscle atrophy, hypotonia, and areflexia. In the acute
to subacute phase, there is inflammation, active gliosis, and
neuronophagia of the ventral horn cells. Hyperintense signal on
T2-weighted images and enhancement of the ventral aspect of the
spinal cord correlate with these pathologic findings. The
differential diagnosis for these MR findings includes multiple
sclerosis, acute disseminated encephalomyelitis (ADEM), HIV
myelitis, and acute transverse myelitis.
Infection with the poliovirus occurs only in humans and is
spread by the fecal-oral route. There is no effective treatment.
Infection by the wild poliovirus has not been reported in the
United States since 1980. The predominant form of the disease is
now vaccine-associated paralytic poliomyelitis (VAPP). VAPP occurs
sporadically in infants who receive the oral polio vaccine and in
their parents, who are susceptible due to fecal excretion of the
live virus. Seven to ten cases of VAPP are reported annually in the
United States, with an incidence of one case per 2.5 million doses
1. Malzberg MS, Rogg JM, Tate CA, et al: Poliomyelitis:
Hyperintensity of the anterior horn cells on MR images of the
spinal cord. AJR 161:863-865, 1993.
2. Querfurth H, Swanson PD: Vaccine-associated paralytic
poliomyelitis. Arch Neurol 47:541-544, 1990.
3. Strebel PM, Sutter RW, Cochi SL, et al: Epidemiology of
poliomyelitis in the United States one decade after the last
reported case of indigenous wild virus-associated disease. Clin
Infect Dis 14:568-579, 1992.
Prepared by Lara A. Hardesty, MD, University of Pittsburgh/Magee
Hospital, Pittsburgh, PA, and Blaise V. Jones, MD, Department of
Radiology, Penn State-Milton S. Hershey Medical Center, Hershey,