neurologia i neurochirurgia polska 50 (2016) 180–184 Available online at www.sciencedirect.com ScienceDirect journal homepage: http://www.elsevier.com/locate/pjnns Case report Midbrain and bilateral paramedian thalamic stroke due to artery of Percheron occlusion Magdalena Restel, Ałła Graban, Grzegorz Witkowski, Danuta Ryglewicz, Halina Sienkiewicz-Jarosz * 1st Department of Neurology, Institute of Psychiatry and Neurology, Warsaw, Poland article info abstract Article history: Introduction: Bilateral thalamic strokes are rare manifestations of posterior circulation Received 11 December 2015 infarcts. Usually the etiology is cardioembolic or small vessel disease combined with Received in revised form individual anatomical predisposition. The symptoms include a variety of neurological 9 January 2016 deficits depending on thalamic structure involvement, such as paresthesias or numbness, Accepted 14 January 2016 hemiparesis with increased reflexes and Babinski sign, third cranial nerve palsy, speech and Available online 24 January 2016 cognition disturbance, memory impairment and stupor. Neuroimaging usually reveals Keywords: Case presentation: We report a case of 61-year-old man, active smoker (25/per day, 50 pack- ischemic loci in adequate thalamic nuclei. Thalamic stroke years) with untreated hypertension who presented at admission consciousness impairment Artery of Percheron occlusion (Glasgow Coma Scale score 9 points), left pupil dilatation without reaction to light, left eye Consciousness disturbance deviation downwards and outwards, vertical gaze paralysis and left-sided hemiplegia. Initial brain computed tomography (CT) was normal. Brain magnetic resonance with diffusion weighted imaging and fluid attenuation inversion recovery sequences (MR DWI/FLAIR) performed on admission showed ischemic changes in bilateral thalami, which were confirmed in routine MRI. Thrombosis of basilar artery and cerebral venous was excluded in CT angiography. Further diagnostic assessment revealed hyperlipidemia, paroxysmal atrial fibrillation and renal cancer with hepatic metastases. Conclusion: Bilateral thalamic stroke due to artery of Percheron occlusion is a rare presentation of stroke, which can be overlooked in routine CT scan. If diagnosed, it requires further evaluation for stroke risk factors, especially cardiovascular disorders associated with increased embolic risk. # 2016 Polish Neurological Society. Published by Elsevier Sp. z o.o. All rights reserved. * Corresponding author at: I Klinika Neurologiczna, Instytut Psychiatrii i Neurologii, Al. Sobieskiego 9, 02-957 Warszawa, Poland. Tel.: +48 22 45 82 548; fax: +48 22 45 82 566. E-mail address: jarosz@ipin.edu.pl (H. Sienkiewicz-Jarosz). http://dx.doi.org/10.1016/j.pjnns.2016.01.008 0028-3843/# 2016 Polish Neurological Society. Published by Elsevier Sp. z o.o. All rights reserved. neurologia i neurochirurgia polska 50 (2016) 180–184 1. Introduction The thalamus, a part of diencephalon, is a structure located between the cerebral cortex and the midbrain, which is involved in receiving, modifying and transferring sensory and motor signals and which regulates consciousness, sleep and alertness by relaying limbic system information [1]. The thalamus is supplied with blood by several arteries: the polar artery which derives from posterior communicating artery, paramedian thalamic-subthalamic arteries (arising from segment P1 of posterior cerebral artery), inferolateral (or thalamogeniculate) artery and choroidal arteries all arising from segment P2 of posterior cerebral artery [2]. In some individuals both thalami are supplied by artery of Percheron, which is a single artery that derives from posterior cerebral artery and its occlusion may result in bilateral thalamic infarction [2]. Ischemic or hemorrhagic lesions in different vascular territories of thalamus result in various neurological syndromes. Polar artery occlusion usually causes infarction of anterior group of thalamic nuclei with neuropsychological deficits (abulia and apathy), personal changes, memory impairment (especially in left-sided infarcts) and consciousness disturbances [3–6]. Paramedian thalamic-subthalamic arteries supply centromedian part of the thalamus and their occlusions result in decreased level of consciousness (arousal impairment, lethargy and hypersomnolence), neuropsychological disturbances and vertical gaze impairment, loss of convergence or pupils abnormalities [6–9]. In case of inferolateral (or thalamogeniculate) artery infarctions, dorsal and posterolateral regions of the thalamus are involved, which clinically results in Dejerine– Roussy syndrome with sensory loss, hemiparesis and sometimes poststroke thalamic pain [6,10]. Characteristic clinical features for posterior choroidal arteries infarcts are visual deficits (mainly quadrantanopia) with visual hallucinations, mild sensory or motor impairment and hyperkinetic syndromes (e.g. ataxia, tremor, dystonia, chorea) [7,11,12]. Thalamic strokes represent 3% of all ischemic strokes and only 11% of all vertebrobasilar infarcts [13,14]. Bilateral infarcts are rare and have been reported in several case presentations [15–17]. Most thalamic strokes involve median part of thalamus (25%) and 72% of them are ischemic [18]. The incidence of bilateral thalamic stroke is unknown. The main risk factors for thalamic strokes are atrial fibrillation, hypertension and atherosclerosis secondary to cigarette smoking, diabetes mellitus, hypertension or dyslipidemia. These conditions are usually associated with multiple lesions [18]. Other conditions, which are associated with increased embolic risk, such as congenital atrial septal defect [15] or other inherited cardiac disease (e.g. hypertrophic or dilated cardiomyopathy) can be also a cause as well as other conditions associated with increased embolic risk (such as neoplasms, hypercoagulable states). As a rather rare causes of thalamic stroke are listed migraine and vasculitis secondary to chronic central nervous system (CNS) infections [6,18]. Brain MRI is a reference imaging modality for thalamic stroke and should be performed as primary or at least 181 confirmative imaging method with routine FLAIR/DWI and T1 and T2 sequences [19]. Brain CT is useful for hemorrhagic lesion exclusion. As far as artery of Percheron imaging is concern MR/CT angiography or conventional angiography should be considered, but probability for occlusion detection is small [19]. 2. Case report 61-year-old man, active smoker (25/per day, 50 pack-years) with untreated hypertension was admitted due to consciousness disturbance and left-sided paresis. The exact time of beginning of the symptoms was unknown – the patient was found unconscious early in the morning on the day of admission (wake-up stroke). In Emergency Room his Glasgow Coma Scale (GCS) score was 9, in neurological examination the left pupil was dilated, without reaction to light, and left eye was deviated downwards and outwards. Moreover, patient presented with vertical gaze paralysis and left-sided hemiplegia with bilateral Babinski sign. An urgent brain CT scan was performed, but it did not revealed any acute ischemic changes in thalamic region (Fig. 1), although there were signs of previously silent ischemic lesions localized mainly in deep structures of the brain. Brain MRI DWI/ FLAIR performed on admission showed ischemic changes consistent with acute infarction in bilateral thalami (Fig. 2). Symmetrical areas of low signal intensity were shown on ADC maps bilaterally in paramedian thalami, symmetrical areas of high signal intensity were presented on diffusion weighted images (DWI), in FLAIR only subtle hyperintense signals were seen in corresponding areas (which suggested acute lesions). Carotid and transcranial Doppler ultrasound revealed hemodynamically irrelevant 40% stenosis of the left internal carotid artery and 30% stenosis of the right internal carotid artery. Blood flow in basilar, vertebral and visible intracranial arteries was normal. The routine MRI (Fig. 3) performed 3 days after admission confirmed subacute infarction in bilateral thalami and anteromedial midbrain suggesting occlusion of the artery of Percheron (AOP). The hyperintense signal intensity along the pial surface of the midbrain interpeduncular fossa representing the ‘‘V sign’’ [19]. Computed tomography angiography (both arterial and venous phases) did not revealed direct signs of AoP occlusion, although there was secondary evidence for it. During hospitalization, the patient was newly diagnosed with hyperlipidemia and paroxysmal atrial fibrillation. He remained slightly somnolent for several days. Initially his level of consciousness gradually improved, but his oculomotor symptoms and pupils remained stable. After 10 days of hospitalization level of consciousness had begun worse, without evidence of epilepsy or new vascular lesions. Additional diagnostic work up performed because of increased levels of D-dimers showed renal cancer with hepatic metastases. The functional as well as neuropsychological outcome was pure, partially probably because of severe comorbidity. The long-term outcome was also unfavorable, 3 months after stroke, the patient was fully dependent on relatives with persistent somnolence and apathy. 182 neurologia i neurochirurgia polska 50 (2016) 180–184 3. Fig. 1 – Initial brain CT scan without any acute ischemic changes in thalamic region. Previous ischemic lesion within internal capsule and periventrical white matter. Discussion The presented patient had a classic triad of basilar syndrome including ocular symptoms (third cranial nerve palsy, pupils abnormalities), impaired consciousness (arousal impairment, lethargy and somnolence) and long tract neurological signs (left hemiparesis) [20]. In such cases it is essential to perform several diagnostic procedures to exclude basilar artery thrombosis and deep cerebral venous thrombosis (which can be a cause of bilateral thalamic infarcts, but usually its presentation is more dramatic and include symptoms of increased intracranial pressure) [21]. Brain CT and MR DWI/FLAIR allowed to exclude the infarction involving occipital lobe (or lobes), that could suggest basilar artery occlusion, but it did revealed symmetrical ischemic lesions in both thalami and anteromedial midbrain, which were consistent with clinical presentation. The ‘‘V sign’’ (identified in 67% patient with AOP and midbrain involvement) was visible as the hyperintense signal intensity along the pial surface of the midbrain interpeduncular fossa [19]. Carotid and basilar Doppler ultrasound was irrelevant. CT angiography was performed (arterial and venous phases), which revealed no signs of arterial or venous thrombosis. Although it also did not show evidence for artery of Percheron (AOP) occlusion it is not unusual as artery of Percheron is rarely visible on angio-MRI or Fig. 2 – Brain MRI performed at admission showed acute ischemic changes in bilateral thalami presenting as symmetrical areas of high signal intensity on diffusion-weighted images (DWI) (A), low signal intensity on ADC maps (B) and only subtle hyperintense signals in corresponding areas in FLAIR sequences (C) (white arrows). neurologia i neurochirurgia polska 50 (2016) 180–184 183 Fig. 3 – The routine MRI performed 3 days after admission showed subacute infarction in bilateral thalami and anteromedial midbrain (A–C) suggesting occlusion of the artery of Percheron (AOP). The hyperintense signal intensity along the pial surface of the midbrain interpeduncular fossa representing the V sign (A, white arrows). angio-CT or conventional angiography [19]. Further diagnostic procedures were performed to identify cardiovascular risk factors, which may have led to bilateral thalamic infarct. The patient was a smoker and had hypertension – two important factors contributing to small vessel disease, which has been reported as the main cause of AOP occlusion in several case series, followed by cardioembolism (on the contrary in young patients cardiogenic brain embolism is the most frequent) [4,6,22]. Paroxysmal atrial fibrillation was detected in 24-hour ECG monitoring. Usually disease prognosis is good, apart from patients with midbrain involvement – our patient not only had coexisting brainstem infarct, but also was found to have kidney neoplasm with hepatic metasteses – a hypercoagulable condition which itself is associated with poor outcome, but also with increase thromboembolic risk. 4. Conclusion In every patient presented with symptoms of brainstem involvement, such as consciousness impairment, oculomotor disturbances and limb paresis, basilar artery occlusion should be suspected. If diagnostic procedures reveal bilateral thalamic ischemic lesion, with or without midbrain involvement, artery of Percheron occlusion may be suspected. The treatment is usually similar to anterior circulation strokes and should include thrombolytic therapy. Although, it was proven that intravenous rt-PA administration is delayed in patients with posterior circulation stroke. The reason is probably delayed or missed diagnosis [23,24]. Conflict of interest None declared. Acknowledgement and financial support None declared. 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