| The
third cranial nerve controls a portion of eye movement, as well as
constriction of the pupil. When it is pressed upon, as in herniation
of the temporal lobe from increased intracranial pressure, the pupil
dilates (the nerve fibers which cause constriction of the pupil run
on the outside of the nerve). In a diabetic patient, if there
is small vessel disease causing the center of the third nerve to receive
insufficient blood, then there is difficulty with movement of the
eye (ophthalmoplegia), but reaction and constriction of the pupil
remain intact. |
