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Painful fourth cranial nerve palsy caused by posteriorly-draining dural carotid-cavernous sinus fistula.

A 65-year-old man with a dural carotid-cavernous fistula (DCCF) presented with sudden onset of painful trochlear nerve paresis. Typical signs of DCCF including conjunctival arterialization, chemosis, and proptosis did not become manifest until 4 months later. This unusual presentation of DCCF was caused by drainage of the fistula posteriorly into the inferior petrosal sinus with low flow. With this condition, patients may present with trochlear nerve palsy without a red eye. Although rare, DCCF must be considered in patients presenting with isolated painful trochlear palsy.