Objective: A patient with cervical internal carotid artery (ICA) dissection presented with visual loss and a mydriatic pupil that resolved after angioplasty and stenting.
Clinical presentation: A 49-year-old woman presented with a unilateral dilated tonic pupil and transient monocular visual loss and subsequently developed speech disturbance. Angiography revealed a left cervical ICA dissection with significant luminal narrowing. The ophthalmic artery filled retrograde through external carotid artery branches and reconstituted the supraclinoid ICA. Computed tomographic perfusion showed significant hypoperfusion of the left hemisphere. Magnetic resonance imaging showed punctate boundary zone infarcts.
Intervention: The patient experienced pressure-dependent left hemispheric transient ischemic attacks and pressure-dependent ocular findings despite anticoagulation. She underwent uncomplicated left ICA angioplasty and stenting. The flow through the ophthalmic artery became anterograde. The tonic pupil returned to symmetry with the contralateral pupil, and the patient's symptoms resolved completely.
Conclusion: Cervical ICA dissection can manifest with a tonic mydriatic pupil. Treatment with angioplasty and stenting of the dissected segment can restore flow and resolve the pupillary abnormality. A pathophysiological mechanism for the mydriasis is proposed.