Isolated third nerve palsy with pupillary sparing is seen in:

Diabetes Isolated third nerve palsy with pupillary sparing is seen in diabetic neuropathy involving cranial nerves. This is thought to arise due to anatomical arrangement of the nerve fibres in the occulomotor nerve. Parasympathetic fibres that control the pupillary function are superficial and spared from ischemic injuries typical of diabetes. In ishchemia, the nerve fibres in the core of the nerve are the first to be affected, as good collateral supply exists in the nerve periphery. But, in subarchnoid hemorrhage, aneurysmal rupture, tumour & trauma; superficial fibres will also be compressed & damaged leading to loss of pupillary reflex. Other causes which can also cause pupillury sparing occulornotor palsy. - vascular diseases - hpeension Spontaneous recovery over a period of months is the rule.