What is the LEAST likely cause of CN III aberrant regeneration?

• A. Tumor
• B. Trauma
• C. Vasculopathic (diabetes)
• D. Aneurysm

Answer: (C)

Aberrant regeneration happens when damaged axons attempt to regrow and sometimes rewire to wrong targets, producing misdirected signals during eye movements. This kind miswiring is most likely after insults that actively injure the nerve and provoke regeneration, such as trauma or compressive lesions from tumors or aneurysms. In contrast, diabetic (vasculopathic) CN III palsy is driven by ischemia of the nerve’s central fibers and tends to spare the parasympathetic outer fibers, with recovery that does not involve the same regenerative misrouting. Because the ischemic mechanism lacks the regenerative remodeling that causes aberrant synkinesis, this is the least likely scenario to produce aberrant regeneration.