Bilateral Paramedian Thalamic Infarction Maximiliano A. Hawkes, MD,* Julieta E. Arena, MD,* Cecilia Rolla´n, MD,w Virginia A. Pujol-Lereis, MD,* Carlos Romero, MD,w and Sebastia´n F. Ameriso, MD* Introduction: Rarely, both paramedian thalami receive arterial blood flow from a single unilateral vessel arising from the first segment of 1 posterior cerebral artery. This artery has received the name of artery of Percheron (AP). There is no consensus regarding the true prevalence of this anatomical variant. Bilateral paramedian thalamic infarcts are uncommon (0.1% to 2% of ischemic strokes). The main cause is the occlusion of the AP due to cardioembolism. Diffusion-weighted magnetic resonance imaging demonstrates the lesion in the acute setting. Materials and Methods: From September 2004 to October 2011, we identified 5 patients who had bilateral paramedian thalamic infarcts. We describe clinical findings and diagnostic imaging patterns observed in these cases and review the literature. Results: Three men and 2 women with bilateral paramedian thalamic infarction probably due to occlusion of AP are described. Mean age at presentation was 58 ± 24 years. Magnetic resonance imaging showed the lesion in all patients. Four patients presented loss of consciousness as initial symptom. Only 1 patient evidenced mesencephalic extension of the infarct on magnetic resonance imaging, although 4 presented abnormal ocular signs. No patients received intravenous thrombolisis because of delayed diagnosis. All patients were discharged home. A 90-year-old woman recovered completely and the other 4 subjects persisted with cognitive symptoms and gaze abnormalities. Conclusions: Clinical presentation and imaging patterns described in this group of patients were similar to published data. High level of suspicion based on clinical and imaging findings is essential for early diagnosis of this rare condition. None of our patients had an early diagnosis of acute ischemic stroke and received proper thrombolytic treatment. Key Words: bilateral paramedian thalamic infraction, artery of Per- cheron, thalamic infarction (The Neurologist 2015;20:89–92) P aramedian thalamic and rostral mesencephalic arterial supply is generally dependent on the paramedian thalamic arteries. These vessels arise from the first segment of the posterior cerebral arteries (P1) bilaterally. In 1973, Percheron described an anatomic variant of the typical anatomy 1,2 in which a solitary arterial trunk branches from one of the proximal segments of either posterior cerebral artery. This vessel is known as the artery of Percheron (AP). 3 There is no consensus regarding the true frequency of this variant, but some authors describe it in up to one third of the population. 4 Bilateral paramedian thalamic infarcts are rare (0.1% to 2% of ischemic strokes). 5–8 The main cause is the occlusion of the AP because of cardioembolism. 4–6,8–12 Patients typically present with decreased level of consciousness, vertical gaze palsy, and behavioral and cognitive changes. 4–8,10,11,13,14 Dif- ferential diagnoses include internal cerebral vein thrombo- sis, 4,7,9 top of the basilar artery infarction, and infiltrating neoplasms. 4,7 Diffusion-weighted magnetic resonance imaging (DWI-MRI) is the method of choice for diagnosis in the acute setting. Angiography may be used to visualize the AP, but is probably usually not needed as part of the routine diagnostic algorithm. 4 We report 5 cases with typical clinical and radio- logic features of AP infarction. MATERIALS AND METHODS In a review of hospital records from September 2004 to October 2011, patients with ischemic stroke were identified. Among them we searched for those who presented bilateral paramedian thalamic infarcts. We describe clinical and imag- ing characteristics of these subjects. The study was previously approved by the Institutional Ethics Committee. RESULTS Among 1682 patients with documented ischemic stroke, 5 subjects (3 males and 2 females) had bilateral paramedian thalamic infarctions. Mean age at presentation was 58 ± 24 years. MRI during the first week confirmed diagnosis in all patients. Four patients presented loss of consciousness as the initial symptom and 1 subject was found at home confused and without recall of previous 48 hours. One patient showed mesencephalic extension of the infarction on MRI, although 4 presented abnormal ocular signs. Cardioembolic sources were demonstrated in 3 subjects [atrial fibrillation in 1 and patent foramen ovale (PFO) with high risk of paradixical embolism scores 15 in 2] and the remaining 2 patients were classified as “embolic strokes of undetermined source”. 16 No patients received intravenous thrombolisis because of delayed diag- nosis. All patients were discharged to their home. A 90-year- old woman recovered completely and the other 4 subjects persisted with cognitive symptoms and gaze abnormalities. Case 1 A 46-year-old man, with otherwise negative past medical history was found at home confused, with no recall of the previous 48 hours. On physical examination he was alert, apa- thetic, with mild expressive aphasia. Brain computed tomog- raphy (CT) scan and MRI showed lesions in both paramedian thalamic regions, consistent with a subacute ischemic stroke. Magnetic resonance angiography (MRA) was normal (Fig. 1). Transesophageal echocardiography with microbubbles injection From the Departments of *Neurology; and wRadiology, Rau´l Carrea Institute for Neurological Research, FLENI, Ciudad auto´noma de Buenos Aires, Buenos Aires, Argentina. The authors declare no conflict of interest. Reprints: Sebastia´n F. Ameriso, MD, Department of Neurology, Rau´l Carrea Institute for Neurological Research, FLENI, Montan˜eses 2325, Ciudad de Buenos Aires, Argentina 1428. E-mail: sameriso@fleni. org.ar. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1074-7931/15/2005-0089 DOI: 10.1097/NRL.0000000000000047 CASE REPORT/CASE SERIES The Neurologist  Volume 20, Number 5, November 2015 www.theneurologist.org | 89 Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.