Electrodiagnostic studies showed widespread but variable denervation, reduced compound muscle action potentials (CMAPs), and normal sensory nerve action potentials (SNAPs), consistent with a severe, asymmetric process affecting anterior horn cells
or motor axons.
One hypothesis is that the reduction of the number of anterior horn cells
at the initial onset of the poliovirus is a factor.
Morphometric study of cervical anterior horn cells
and pyramidal tracts in medulla oblongata and the spinal cord in patients with cerebrovascular diseases.
Electrodiagnostic studies, however, displayed reduced compound muscle action potentials, normal sensory nerve action potentials, and widespread denervation, consistent with a severe, asymmetric process involving anterior horn cells
or motor axons.
Patients with flaccid paralysis have perivascular lymphocytic infiltration in the spinal cord, microglial nodules, and loss of anterior horn cells
Destruction of the spinal anterior horn cells
may also cause acute flaccid paralysis (AFP), presenting as asymmetric limb weakness, hypoflexia or areflexia, and acute bowel or bladder dysfunction that may appear without signs of meningoencephalitis.
Werdnig-Hoffman disease is a neuromuscular disorder caused by loss of anterior horn cells
and motor nuclei of cranial nerves V through VIII.
This report describes six cases of WNV-associated AFP in which clinical and electrophysiologic findings suggest a pathologic process involving anterior horn cells
and motor axons similar to that seen in acute poliomyelitis.
In addition, WNV-associated acute flaccid paralysis was discussed; the paralysis is caused by localized infection of the anterior horn cells
of the spinal cord, resulting in signs and symptoms similar to poliomyelitis.