Isolated Trochlear Nerve Palsy Associated with Carotid-Cavernous Sinus Fistula: A Case Report

Abstract

Purpose: To report a case of isolated trochlear nerve palsy caused by carotid-cavernous sinus fistula. Method: A case report. Result: A 67-year-old woman suffered from intermittent thunderclap headache and acute onset of vertical diplopia when in left gaze and right-head tilt. Routine ocular examinations were unremarkable with the exception that the three-step test revealed right superior oblique muscle palsy. A brain magnetic resonance imaging and artery series (MRI/MRA) revealed a carotid-cavernous sinus fistula in the right cavernous sinus. Conventional cerebral angiography confirmed that the lesion was fed by meningeal branches of the internal carotid artery with flow posteriorly to the inferior petrosal sinus, and then to the internal jugular vein. Trans-arterial embolization (TAE) was performed, and a Guglielmi Detachable Coil (GDC) placed. The vertical diplopia resolved significantly after TAE but pulsatile tinnitus remained. Conclusion: Ocular motor nerves palsy associated with a cavernous sinus lesion usually involves the third, fourth, and sixth cranial nerves. Isolated the fourth nerve palsy caused by carotid-cavernous sinus fistula (CCSF) is uncommon. In this case, we propose the following: (1) Thunderclap-type headache could appear as a first symptom in CCSF. (2) Isolated trochlear nerve palsy due to the cavernous sinus lesion is uncommon, clinicians should be alert of its possibility.