Международный неврологический журнал 1(55) 2013

Introduction

The hypothalamus, medial ventral thalami and subthalamic-mesencephalic junction are most commonly irrigated by perforating arteries arising from both P1 segments of the posterior cerebral artery (PCA). Rarely, however, a single paramedian artery originating as a common trunk from a unilateral P1 will branch and give bilateral paramedian supply. This normal anatomic variant was first described by G.  Percheron, named as the artery of Percheron, and wasclassified as type IIb in the G. Percheron classification dating from 1976 [1, 2]. Occlusion of this artery most likely causes bilateral paramedian thalamic and mesencephalic infarctions [3].

We report a young patient (in their early 30s) who presented with sudden onset of visual disturbance and speech difficulties. The exclusive and unique characteristics of this case are young age of the patient, rare clinical presentation of speech difficulties with no loss of consciousness. Additionally, a review of the literature, from 1981 to 2009, and analysis of 51 reported cases of occlusion of artery of Percheron allowed us to identify demographic characteristics and the most widely reported clinical signs and symptoms.

Case report

A young (in their early 30s) male patient presented with acute onset of visual distortion (seeing wavy lines) and extreme speech difficulties. He had no significant past medical history. He denied using any kind of over the counter medications, illicit drugs or prescribed medications. He was not a smoker and drank only occasionally. Physical examination revealed that he was alert and oriented with no history of syncope, loss of consciousness or gait instability. His corneal reflexes were intact and his pupils were normally reactive to light and symmetrical. The deep tendon reflexes were +2 and symmetrical. Cardiovascular examination demonstrated regular rhythm with no murmur or gallop. Due to his significant neurological deficit, MR imaging was performed, approximately 3 h after the onset of the patient's symptoms. The MR images showed bilateral high signal intensity on fluid attenuated inversion recovery and fast spin echo T2 weighted images, in the paramedian thalami and rostral midbrain, more prominent on the left side (figure 1).

Additionally, trace diffusion weighted imaging showed high signal intensity, in corresponding regions. MR angiography demonstrated the presence of a single, large vessel arising from the P1 segment of the left PCA, consistent with the artery of Percheron (figures 1 and 2). Echocardiography was subsequently performed disclosing a patent foramen ovale and presumably no intracardiac thrombosis. Lower extremity Doppler ultrasound was normal with no evidence of deep vein thrombosis. Heparin was started immediately and the foramen ovale was closed by interventional cardiology on the second day of his admission. Hypercoagulation workup was performed before starting intravenous heparin. Prothrombin times and partial thromboplastin times were normal. Factor II, factor V, antithrombin III, protein C, protein S and anticardiolipin antibodies were all within normal limits. Gene assay was unremarkable.

Discussion

A review of the literature on PubMed, from 1981 to 2009, revealed 51 reported cases of bilateral paramedian thalamic infarcts in the presence of an artery of Percheron (table 1). A total of 20 articles reported 51 patients, among whom 19 were women and 32 were men (M/F ratio of 1.7 : 1). The most common age at presentation was over 50 years of age (mean age 59 ± 6 years), ranging from a 1-day-old male neonate to a 91-year-old male. Analysis of all previously reported cases demonstrated a wide variety of reported clinical signs and symptoms. The most common clinical presentations were: visual disturbance, particularly vertical gaze palsy (55 %); confusion and decreased alertness (49 %); coma (30 %); memory impairment — that is, anterograde amnesia with difficulties in verbal and visual learning (28 %); and behavioral problems (23 %). Numerous typical presentations are presented in table 1 [3–22]. Although the most common clinical presentation is loss of consciousness, it was not observed in our patient and he presented with visual disturbance, which is another presentation commonly seen with this syndrome. This may be due to the fact that in our patient involvement was unilateral. He also had speech difficulties, which is one of the rare presentations.

There are a variety of risk factors for stroke — diabetes mellitus, hypertension, hyperlipidemia, smoking and oral contraception consumption. In our case, patent foramen ovale predisposed the patient to an embolic accident. This may also be the reason for presentation at a younger age.

The most common method of diagnosing bilateral paramedian thalamic infarction and occlusion of the Percheron artery is MRI/MR angiography, replacing CT scan in the early 1990s.

Petit et al. described bilateral paramedian thalamic infarcts with CT imaging [4]. They describe a 33-year-old woman on oral contraceptives who had presented with sudden onset of neurological disorders characterized by decreased alertness, absence of motor and verbal spontaneity, anterograde amnesia with difficulties in verbal and visual learning, and paralysis of upwards and downwards ocular movements affecting mainly saccadic movements while her convergence was normal [4]. Reilley et al. presented six patients with bilateral paramedian thalamic infarction with both CT and MRI [9].

Observation of specific neurologic-neuropsychological patterns, such as confusion and visual disturbance (particularly vertical gaze palsy), should raise the question of occlusion of the artery of Percheron. Detection of bilateral paramedian thalamic and mesencephalic lesions is most reflective of a vascular etiology in the distribution of the artery of Percheron. Top of the basilar syndrome can also manifest with similar clinical presentation but it is frequently associated with larger infarctions, involving the cerebellum, occipital lobes and temporal lobes [3]. Echocardiogram should always be performed in these patients to evaluate any cardiac source of emboli, as seen in our patient. To our knowledge, there are no cases of bilateral paramedian thalamic and mesencephalic infarcts that have been reported in a young patient with a patent foramen ovale.

In conclusion, occlusion of the artery of Percheron causes bilateral thalamic and mesencephalic infarction. A vast variety of presentations have been reported with this entity, most common of which are visual disturbance, particularly vertical gaze palsy, confusion and decreased alertness, coma, memory impairment, difficulties in verbal and visual learning, and behavioral problems. Demonstration of a single trunk arising from the P1 segment of one of the PCAs on MRI/MR angiography is the most reliable method of evaluating and confirming the presence of this diagnosis.