Teaching NeuroImage: Convergence spasm associated with midbrain compression by cerebral aneurysm.

A 72-year-old woman presented with intermittent diplopia. She had a history of vascular disease, but no history of stroke or psychiatric disturbance. On examination, she developed convergence spasm with associated miosis following fixation on near targets and during horizontal smooth pursuit (video, figure 1). The spasms were terminated with a blink. She had no ptosis, her eye movements were normal in range, and her pupils were equal in size with normal reactions to light. Neurologic examination was otherwise unremarkable. Five years prior to her current presentation, a left-sided terminal carotid artery aneurysm had been incidentally detected. The aneurysm gradually expanded to a diameter of 2.4 cm and compressed the midbrain (figure 2). The intermittent diplopia had developed in the months following endovascular coiling of the aneurysm. Convergence spasm is characterized by the inappropriate appearance of the near triad, which consists of convergence, miosis, and accommodation.1 Most patients are young and the cause is psychiatric; a focal lesion is rarely found.1 Since the neural substrate for the near triad is located in the midbrain, convergence spasm could occur Address correspondence and reprint requests to Dr. G. Michael Halmagyi, Department of Neurology, Royal Prince Alfred Hospital, Missenden Road, Camperdown NSW 2050, Australia [email protected]