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Bilateral Thalamic Infarction by Percheron Occlusion Infarto Talâmico Bilateral por Oclusão da Artéria de Percheron Walter J. Fagundes-Pereyra1, Alexandre Neves Furtado2 Filipe Machado Barcelos2 Jovarci Motta2

ABSTRACT Objective: The artery of Percheron is an uncommon single trunk variant of the thalamoperforating that supplies the paramedian thalamic territory bilaterally and the rostral midbrain. Four cases of artery of Percheron (PA) occlusion with bilateral paramedian thalamic infarctions are reported, considering aspects of its clinical and radiological presentation, as well its prognosis. Methods: Four patients with infarcts due to PA occlusion were diagnosed. The data for the study were retrospectively obtained from the medical records of patients. Results: Four patients with PA infarctions were diagnosed. All patients have presented a symmetrical bilateral paramedian infarction, and two of them also presented midbrain involvement, with abnormal images on MRi and CTs. Clinical presentations have included sudden onset of bilateral palpebral ptosis, headache, ophthalmoplegia, aphasia, prostration, confabulation, mental confusion and ataxia. Conclusion: Although rare, occlusion of artery of Percheron should be part of the differential diagnosis when symmetrical bilateral paramedian thalamic and mesencephalic lesions occur. Key words: Cerebral Arterial Diseases; Stroke; Brain Infarction; Cerebral Infarction; Infarction, Posterior Cerebral Artery RESUMO Objetivo: A artéria de Percheron é uma variante rara das artérias tálamoperfurantes, representada por um tronco único que irriga o território talâmico paramediano bilateral e o mesencéfalo rostral. Quatro casos de oclusão da artéria de Percheron com infartos talâmicos paramedianos bilaterais são relatados, considerando aspectos de sua apresentação clínica e radiológica, bem como seu prognóstico. Métodos: Quatro pacientes com infartos decorrentes da oclusão da artéria de Percheron foram diagnosticados. Os dados do estudo foram obtidos dos respectivos prontuários. Resultados: Quatro pacientes com infartos decorrentes da oclusão da artéria de Percheron foram diagnosticados. Todos os pacientes apresentaram infarto talâmico paramediano bilateral simétrico, e dois deles também apresentaram envolvimento mesencefálico, com imagens anormais na ressonância magnética e tomografias. Manifestações clínicas incluem início súbito de ptose palpebral bilateral, dor de cabeça, oftalmoplegia, afasia, prostração, confabulação, confusão mental e ataxia. Conclusão: Apesar de rara, a oclusão da artéria de Percheron deve fazer parte do diagnóstico diferencial quando lesões talâmicas paramedianas bilaterais simétricas e mesencefálicas ocorrerem. Palavras-chave: Doenças Arteriais Cerebrais; Acidente Vascular Cerebral; Infarto Encefálico; Infarto Cerebral; Infarto da Artéria Cerebral Posterior

thalamic infarctions, considering aspects of its clinical and Introduction radiological presentation, as well its prognosis and treatment.

The artery of Percheron (PA) is an uncommon anatomic variant of the thalamoperforating arteries, represented by a single trunk that arises from the P1 segment of one of the posterior Methods cerebral arteries (PCA). This artery supplies the paramedian thalamic territory bilaterally and the rostral midbrain5,11. When The data for the study were retrospectively obtained from it is occluded, the thalamic infarcts are always bilateral and the analysis and systematic review of the medical records of medial, with or without mesencephalic involvement3,8. patients. All of them occurred between 2010 and 2012, and had Magnetic Resonance imaging (MRi) (including FLAIR We report four cases of PA occlusion with bilateral paramedian

1Médico do Departamento de Neurocirurgia do Hospital Estadual Dr. Dório Silva. Professor do Departamento de Clínica Cirúrgica da Universidade Federal do Espírito Santo (UFES). 2Acadêmico do curso de Medicina da Universidade Federal do Espírito Santo (UFES).

Received June 30, 2014. Accepted Dec 12, 2014 WJ Fagundes-Pereyra, AN Furtado, FM Barcelos, J Motta. - Bilateral Thalamic Infarction by Percheron Artery Occlusion J Bras Neurocirurg 25 (1): 20 - 23, 2014 23

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and DWI, T2, T2 gradient, T1, and T1 postcontrast sequences) recovery. Two of them progressed well, but remain with some and Computed Tomography scan (CTs) studies. Two patients eye movement disorder. In the other one, bilateral ptosis were submitted to digital angiographies and two patients had disappeared after one year, but the sphincter control was lost, angio-MRi studies. and the walk and speech prosecute with difficulty. The study is in accordance with the ethical standards of the Helsinki Declaration and was submitted to the Research Ethics Committee (CEP) of the Center of Health Sciences of the Federal University of Espírito Santo (CCS/UFES), in accordance with Resolution 196/96 of the National Health Council (CNS). It was approved under protocol number 420.293. The CEP waived the presentation of the term of free and informed consent (TCLE), understanding that this is an observational study, not running for any intervention, risk or exposure to the sample, and does not allow the identification of the research subjects. Figure 1: llustrative representation of the three different thalamic vascular supplies, showing the artery of Percheron in B: an asymmetrical single trunk arising from the P1 segment of one of the posterior cerebral arteries.

PCoA = Posterior Communicating Artery; SCA = Superior Cerebellar Artery; PCA = Posterior Cerebral Results Artery; BA = Basilar Artery; PA = Percheron’s Artery; TPA = Thalamoperforating Arteries.

Four patients with PA infarctions were diagnosed. Neoplasm and infectious or inflammatory diseases were considered as exclusion criteria. All patients have presented a symmetric bilateral paramedian thalamus infarction. Two of them also presented midbrain involvement. Three were men and one was a woman. The mean age was 61 years-old (51–72 years). Clinical presentations have included sudden onset of bilateral palpebral ptosis, headache, ophthalmoplegia (vertical gaze palsy), aphasia, somnolence, prostration, confabulation, mental confusion and ataxia. Clinical data of each patient are presented in Table 1. All patients presented abnormal signal intensity on MRi and hypodensity on CTs involving the bilateral paramedian thalamus (Figure 2). Two of them also have presented the same image abnormalities in the midbrain (Figure 3). Two patients were submitted to a digital angiography in which was not observed abnormalities of the supra-aortic, carotid and vertebral arteries. The basilar artery was also patent. The follow up ranged from 6 to 14 months (mean 9.3 Figure 2: MRi of bilateral paramedian thalamic infarction (T2-weighted MRi in A, C and D and T1-weighted MRi in B). Horizontal sections, from dorsal (A) to months). No deaths were observed. One patient has had total ventral (D) – Patient 3.

WJ Fagundes-Pereyra, AN Furtado, FM Barcelos, J Motta. - Bilateral Thalamic Infarction by Percheron Artery Occlusion J Bras Neurocirurg 25 (1): 20 - 23, 2014 24

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originating from P1 segments of posterior cerebral arteries (Figure 1): in the first type, small branches arises from both P1 segments (Figure 1A); in the second type, there is an asymmetrical common trunk arising from one of the P1 segments providing bilateral distribution (Figure 1B); in the third type, branches emanate from an arterial arcade, bridging the two P1 segments (Figure 1C)7,11,12. The second type is referred as artery of Percheron11. Occlusion of this vessel causes a bilateral thalamic stroke, which involves the paramedian nuclei10. Strokes limited to paramedian territories account for about 22% to 35% of all thalamic infarcts1,9,13, and their most frequent etiology is cardioembolism2,9. Ischemic lesion may affect the thalamic nuclei in different

Figure 3: Fluid-Attenuated Inversion Recovery (FLAIR) MRi revealing the midbrain combinations and produce sensorimotor and behavioral involvement in a bilateral paramedian thalamic infarction – Patient 3. syndromes depending on which nuclei are involved14. Bilateral infarction in the paramedian artery territory may Table 1. Clinical data presentation of four patients with bilateral thalamic infarction result in an acutely ill and a severely impaired patient14. Follow Clinical Image Midbrain Such signs could be associated with cognitive impairment, Patient Sex Age up Outcome Status studies involvement (months) especially amnesia and executive dysfunction, and mood Mental confusion, CTs, MRi, 14 1 F 57 Yes 8 EMD changes . Disorientation, confusion, hypersomnolence, deep prostration, Angio-MRi EMD coma or akinetic mutism (awake unresponsiveness), and Mental CTs, MRi, Good recovery, 2 M 72 confusion, No 14 Angio-MRi without deficits severe memory impairment with confabulation are prominent headache Mental behavioral features, often accompanied by eye movement confusion, Mental sphincter 14 confusion, EMD, abnormalities . Vertical gaze paresis is a common symptom in CTs, MRi, control 3 M 51 somnolence, Yes 8 DA disturbance, palpebral ptosis, bilateral paramedian infaction and it is highly suggestive of the walk and ataxia, aphasia speech thalamo-subthalamic localization of the lesion4, as observed in abnormalities Mental confusion, CTs, MRi, our patients, associated with palpebral ptosis. 4 M 64 No 6 EMD confabulation, DA headache, EMD Differential diagnosis of the amnestic syndrome resulting from EMD = eye movement disorder; DA = digital angiography; MRi = Magnetic Resonance imaging; CTs = Computed Tomography scan paramedian territory infarction should include the thiamine- deficient Korsakoff syndrome that destroys the medial dorsal thalamic nuclei and mamillary bodies15. Conclusion Percheron’s artery is generally too small to be visualized by angio-MRi and its existence can only be hypothesized on the The details of thalamic vascularization were first studied by basis of the distribution of ischemic lesions10. So, its occlusion Duret, Foix and Hillemand, and subsequently by Lazorthes is only indirectly diagnosed. 14 and Plets et al. . Most of the perforating branches from the The diagnosis should be made as early as possible, within P1 segments of PCA have an ipsilateral distribution (78%); the time limit for thrombolytic therapy, since its efficiency bilateral or even contralateral distributions may be observed in decreases rapidly6. The treatment includes the routine 11 22% of individuals . treatment for stroke. None of our patients were admitted in the Percheron studied the variations of this arterial supply and therapeutic window to thrombolytic therapy. its distributions, and described three different types of supply We conclude that although rare, occlusion of the artery of

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Percheron should be part of the differential diagnosis when with post-mortem examinations. Contemp Neurol Ser. 1971;7:1- symmetrical bilateral paramedian thalamic and mesencephalic 206. lesions occurred.

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WJ Fagundes-Pereyra, AN Furtado, FM Barcelos, J Motta. - Bilateral Thalamic Infarction by Percheron Artery Occlusion J Bras Neurocirurg 25 (1): 20 - 23, 2014