Third nerve palsy with pupillary sparing is seen in all except:

Answer is B (Aneurysm of posterior communicating aery): If the pupil is entirely normal, with all other components of an occulomotor palsy present aneurysm is so rare that an angiogram is seldom indicated. - Harrison Isolated pupil-sparing occulomotor palsy Most cases are thought to result from microvascular infarction of the nerve. Somewhere along its course from the brainstem to the orbit Major risk factors are: Diabetes Hypeension Vascular disease Major presentation is with pain. Spontaneous recovery over a period of months is the rule.