Six months after a documented complete left third nerve palsy, a patient's ptosis has partially improved but examination now reveals retraction of the left upper lid when the eye adducts or depresses, and slow adduction of the left eye on attempted upgaze. This pattern of aberrant regeneration most strongly suggests that the original cause was:
- A Compressive lesion such as an aneurysm or meningioma ✓
- B Diabetic microvascular infarction of the nerve
- C Myasthenia gravis
- D Chronic progressive external ophthalmoplegia
Correct answer: A. Compressive lesion such as an aneurysm or meningioma
Explanation
Aberrant regeneration of the third nerve produces synkinetic movements such as lid retraction on adduction or depression (pseudo-Graefe sign) and co-contraction of extraocular muscles. It develops after chronic compressive damage that disrupts axonal guidance, classically from a posterior communicating aneurysm, tumour or traumatic injury. Ischaemic diabetic third nerve palsies characteristically resolve completely without aberrant regeneration, which is the single fact that eliminates option B. Its presence therefore mandates imaging of the parasellar region.
Reference: Kanski's Clinical Ophthalmology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.