V-shaped MRI change in the midbrain of a patient with artery of Percheron infarction

Abstract

A 68-year old man presented with acute onset bilateral ptosis [Figure 1a]. He was taking apixaban and cilostazol for atrial fibrillation and angina pectoris. Upon admission, he was alert, and his pupils were dilated 5 mm and unreactive to light. He developed paralysis of eye movements, except for lateral rectus, consistent with bilateral oculomotor paralysis [Figure 1b-g]. In addition, the patient had left hemianopsia. He did not have quadriplegia or any other neurological symptoms; these symptoms developed 12 h before admission and never improved. Anti-acetylcholine receptor antibodies were negative, whereas serum vitamin B1 and B12 levels were normal. Furthermore, diffusion-weighted magnetic resonance imaging (MRI) revealed infarction of bilateral thalami, rostral midbrain, and right occipital lobe [Figure 1h and i]. He was diagnosed with artery of Percheron (AOP) and posterior cerebral artery (PCA) infarction. Bilateral paramedian thalamic stroke is characterized by vertical gaze palsy, memory impairment, and coma;[1] however, our patient developed only bilateral oculomotor nerve paralysis. Moreover, cerebral peduncle infarction affected only the oculomotor nerve emerging from the brainstem. The nearby oculomotor nucleus and interstitial nucleus of Cajar remained unaffected. The thalami and midbrain are supplied by several small arterial branches exhibiting significant variability. AOP is an uncommon variant arising from PCA supplying bilateral thalami with rostral midbrain.[1] A study reported that AOP infarction occurred in only 0.6% of 2750 patients with ischemic stroke,[2] and AOP is rarely visualized after infarction.[1,3-5] Our patient demonstrated a typical V-shaped MRI change in the midbrain, which was reported in 67% of patients with AOP infarction.[1]