Final answer:
An LMN lesion caused by poliovirus infection results in weakness, hypotonia, flaccid paralysis, hyporeflexia, and fasciculations due to the inability of the damaged lower motoneurons to properly signal muscles for movement and control.
Step-by-step explanation:
Poliovirus infection can lead to selective destruction of lower motoneurons (LMNs), presenting with signs of an LMN lesion. The key signs of such a lesion include weakness, hypotonia (decreased muscle tone), flaccid paralysis (loss of voluntary muscle control and tone), hyporeflexia (decreased muscle reflexes), and fasciculations (involuntary muscle twitching).
These symptoms occur because the LMNs are responsible for transmitting signals from the spinal cord to the muscles for movement. When these neurons are damaged, such as by poliovirus, their inability to function correctly leads to the noted LMN signs, profoundly affecting muscle function and control.