A 58-year-old man from Delhi presents with severe, burning pain in his left leg following a motor vehicle accident 6 months ago. The pain is described as constant, with a sensation of 'pins and needles' and occasional electric shock-like quality. Physical examination reveals allodynia (pain with light touch) and hyperalgesia (exaggerated pain response to pinprick) in the affected limb. Nerve conduction studies and imaging are normal. He has already tried NSAIDs and paracetamol without relief. Which of the following mechanisms best explains the persistent pain despite normal structural imaging?