Three patients developed anisocoria as a result of third nerve palsies caused by intracranial lesions: two in the cavernous sinus and one in the mesencephalon. Pharmacologic testing using low concentration pilocarpine showed apparent preganglionic parasympathetic supersensitivity of the abnormal pupil. These findings are compatible with the existence of a proposed direct pathway from the midbrain to the eye, without synapse at the ciliary ganglion. Cholinergic hypersensitivity can occur, not only with postciliary ganglionic but also with preciliary ganglionic parasympathetic lesions.
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