<P> It should be borne in mind, however, that the branched structure of the oculomotor nerve means that damage sustained at different points along its pathway, or damage caused in different ways (compression versus loss of blood supply, for example), will result in different muscle groups or, indeed, different individual muscles being affected, thus producing different presentation patterns . </P> <P> Compressive oculomotor nerve damage could result in compression of the parasympathetic fibers before any disruption of the motor fibers occurs, since the parasympathetic fibers run on the outside of the nerve . Therefore, one could have lid ptosis and mydriasis (a "blown" pupil) as a result of parasympathetic fiber compression before the "down and out" position is seen . </P> <P> Oculomotor palsy can arise as a result of a number of different conditions . Non traumatic pupil - sparing oculomotor nerve palsies are often referred to as a' medical third' with those affecting the pupil being known as a' surgical third' . </P> <P> The origins of the vast majority of congenital oculomotor palsies are unknown, or idiopathic to use the medical term . There is some evidence of a familial tendency to the condition, particularly to a partial palsy involving the superior division of the nerve with an autosomal recessive inheritance . The condition can also result from aplasia or hypoplasia of one or more of the muscles supplied by the oculomotor nerve . It can also occur as a consequence of severe birth trauma . </P>

What other signs are commonly seen apart from blepharoptosis to define a third cranial nerve palsy