Diagnostic utility of delayed cerebral angiography in suspected artery of Percheron infarction presenting as bilateral paramedian thalamic infarction: A case report

Abstract

The artery of Percheron (AOP) is a rare anatomical variant in which a solitary perforating artery arising from a unilateral posterior cerebral artery supplies both paramedian thalami, with or without the rostral midbrain. Occlusion of the AOP results in a characteristic pattern of bilateral paramedian thalamic infarction; however, diagnosis is often challenging because the responsible vessel is rarely visualized on routine vascular imaging. A 68-year-old man was admitted to our hospital with severe disturbance of consciousness. On admission, his Glasgow Coma Scale score was E1V1M4 and his National Institutes of Health Stroke Scale score was 40. Magnetic resonance imaging demonstrated acute bilateral paramedian thalamic infarctions. Magnetic resonance angiography (MRA) did not clearly visualize the artery of Percheron; a small perforating branch arising from the left P1 segment appeared poorly visualized or interrupted, although this finding could reflect the spatial-resolution limitations of MRA. Given the characteristic bilateral paramedian thalamic infarct pattern, artery of Percheron infarction was suspected. The patient was treated conservatively with dual antiplatelet therapy and rehabilitation. After his systemic condition had stabilized and his level of consciousness had improved, digital subtraction angiography (DSA) was performed on hospital day 30 to reassess the posterior circulation and perforating arterial anatomy. DSA demonstrated a perforating artery arising from the left P1 segment and coursing toward the bilateral paramedian thalami, anatomically consistent with the artery of Percheron. Based on the characteristic infarct distribution together with the angiographic anatomy, artery of Percheron infarction was considered highly likely, although the angiographic finding did not directly prove that this vessel had been the acute culprit. After 45 days of hospitalization, the patient was transferred to a rehabilitation hospital; he was able to communicate verbally but remained wheelchair dependent, with a modified Rankin Scale score of 4. This case highlights the potential diagnostic value of delayed DSA in selected patients with suspected artery of Percheron infarction. Delayed angiography may provide useful anatomical information after the patient’s clinical condition has stabilized; however, the angiographic findings should be interpreted together with the characteristic infarct distribution rather than as direct proof of the acute culprit vessel.

Introduction

The artery of Percheron (AOP) is a rare anatomical variant in which a single thalamoperforating artery originates from the P1 segment of one posterior cerebral artery (PCA) and supplies both paramedian thalami [1], with variable contribution to the rostral midbrain. Occlusion of this artery results in a characteristic pattern of bilateral paramedian thalamic infarction with or without midbrain involvement [1,2]. Although AOP infarction accounts for only a small proportion of ischemic strokes, it represents an important cause of bilateral thalamic infarction.

The clinical manifestations of AOP infarction are diverse and include altered consciousness, hypersomnolence, memory impairment, confusion, and vertical gaze palsy [[2], [3], [4], [5]]. Because the responsible vessel is extremely small, direct visualization by computed tomography angiography (CTA) or magnetic resonance angiography (MRA) is often difficult. Therefore, diagnosis is usually based on characteristic clinical and radiological findings rather than direct demonstration of the occluded artery.

We report a patient with bilateral paramedian thalamic infarction in whom delayed cerebral angiography demonstrated a perforating artery arising from the left P1 segment with anatomy consistent with an artery of Percheron, supporting the diagnosis without directly proving the acute culprit vessel.

Case presentation

A 68-year-old man with a history of hypertension and dyslipidemia was brought to our hospital because of severe disturbance of consciousness. He had been independent in all activities of daily living before stroke onset (prestroke modified Rankin Scale [mRS] score, 0). Four days before admission, he was last seen well. When he failed to appear at work, a colleague visited his home and found him unconscious. Emergency medical services were activated, and he was transported to our institution.

On arrival, his Glasgow Coma Scale score was E1V1M4, and the National Institutes of Health Stroke Scale (NIHSS) score was 40. Neurological examination demonstrated severe impairment of consciousness and quadriparesis (manual muscle testing grade 1 in all extremities). Electrocardiography showed no evidence of atrial fibrillation. Transthoracic echocardiography was not performed. His mRS score on admission was 5.

Magnetic resonance imaging revealed acute bilateral paramedian thalamic infarctions. Diffusion-weighted imaging demonstrated symmetrical hyperintense lesions involving both paramedian thalami, with corresponding hyperintense lesions on fluid-attenuated inversion recovery imaging. On MRA, the AOP itself was not clearly visualized. A small perforating branch arising from the left P1 segment appeared poorly visualized or interrupted; however, this appearance was considered nondiagnostic because of the limited spatial resolution of MRA. No definite basilar-tip occlusion was identified. Given the characteristic bilateral paramedian thalamic infarct distribution, AOP infarction was nevertheless suspected (Fig. 1).

Fig. 1.

Initial MRI and MRA. (A) DWI shows symmetric bilateral paramedian thalamic infarctions (arrows). (B) FLAIR imaging confirms corresponding bilateral paramedian thalamic lesions (arrows). (C) MRA does not clearly visualize the AOP; the suspected left P1 perforating branch is poorly visualized (arrowhead). This finding is not definitive evidence of acute occlusion because of the spatial-resolution limitations of MRA.

The patient was treated conservatively with dual antiplatelet therapy consisting of aspirin (100 mg/d) and clopidogrel (75 mg/d), followed by rehabilitation. No neurological deterioration or recurrent ischemic events occurred during hospitalization, and his level of consciousness gradually improved. During the subacute phase, dual antiplatelet therapy was de-escalated to single antiplatelet therapy with aspirin.

By hospital day 30, his systemic condition had stabilized and his level of consciousness had improved compared with admission. Because further characterization of the posterior circulation and perforating arterial anatomy was considered clinically meaningful in the setting of the unusual bilateral paramedian thalamic infarct pattern, digital subtraction angiography (DSA) was performed. DSA demonstrated a perforating artery arising from the left P1 segment and coursing toward the bilateral paramedian thalami (Fig. 2). This anatomy was consistent with an artery of Percheron. Although the vessel may have represented a recanalized AOP, the angiographic appearance alone could not establish that it had been the acute culprit vessel.

Fig. 2.

Follow-up DSA on hospital day 30. (A) Anteroposterior and (B) lateral views show a perforating artery arising from the left P1 segment and coursing medially toward the bilateral paramedian thalami (arrowheads), anatomically consistent with an AOP. This finding supports AOP anatomy but does not directly prove that the vessel was the acute culprit.

After 45 days of hospitalization, the patient was transferred to a rehabilitation hospital. At the time of transfer, he was able to communicate verbally but remained wheelchair dependent for mobility. His modified Rankin Scale score had improved from 5 on admission to 4 at transfer. Reliable serial documentation of vertical gaze and memory function was not available in the retrospective medical record, and these features were therefore not inferred.

Discussion

The AOP is an uncommon anatomical variant first described by Percheron. In this variant, a solitary perforating artery arising from one PCA supplies both paramedian thalami and occasionally the rostral midbrain. Occlusion of the AOP produces a characteristic pattern of bilateral paramedian thalamic infarction [1,2].

The most common clinical manifestations of AOP infarction are altered mental status, hypersomnolence, coma, memory impairment, and vertical gaze palsy. These symptoms are attributed to involvement of the paramedian thalamic nuclei and ascending reticular activating system. In the present case, severe disturbance of consciousness was the predominant manifestation, which is consistent with previous reports [[2], [3], [4], [5]].

Diagnosis of AOP infarction is often challenging. Although MRI typically demonstrates bilateral paramedian thalamic infarction, the responsible artery is rarely visualized because of its small caliber. Consequently, CTA and MRA frequently fail to identify the occluded vessel. Previous studies have emphasized that diagnosis is usually established based on the characteristic infarct distribution rather than direct vascular imaging findings [1,2,5]. In the present case, the AOP itself was not directly visualized on initial MRA, and the apparent poor visualization or interruption of a left P1 perforating branch could have reflected the spatial-resolution limitations of MRA rather than true occlusion. Nevertheless, the bilateral paramedian thalamic infarct pattern raised strong suspicion for AOP infarction. Electrocardiography revealed no evidence of atrial fibrillation, although a cardioembolic source could not be completely excluded because transthoracic echocardiography was not performed.

The unique aspect of the present case is the demonstration of a perforating artery arising from the left P1 segment on follow-up angiography. Its origin and course toward the bilateral paramedian thalami were anatomically consistent with an AOP. However, definitive proof that this vessel was responsible for the acute infarction is not possible. The diagnosis therefore rests on the combination of the characteristic bilateral paramedian thalamic infarct distribution and the angiographic demonstration of compatible vascular anatomy. The vessel may have represented a recanalized AOP that became visible during the subacute phase, but this interpretation remains inferential. Similar angiographic observations have rarely been reported in the literature [6].

Only a limited number of reports have described angiographic findings suggestive of AOP anatomy [6]. Therefore, delayed cerebral angiography may provide useful anatomical information in selected patients with bilateral thalamic infarction when the diagnosis remains uncertain.

The differential diagnosis of bilateral paramedian thalamic lesions includes top-of-the-basilar syndrome, deep cerebral venous thrombosis, Wernicke encephalopathy, other metabolic or toxic encephalopathies, inflammatory diseases, and neoplastic lesions [1,2,7]. Top-of-the-basilar syndrome was considered less likely because no definite basilar-tip occlusion was identified on MRA. Deep cerebral venous thrombosis can also produce bilateral thalamic abnormalities, but the acute symmetric diffusion-restricted lesions in a paramedian arterial distribution, together with the later demonstration of a unilateral P1 perforating artery supplying the bilateral paramedian thalami, favored AOP infarction. Nonvascular causes were less consistent with the abrupt severe neurological presentation and the characteristic arterial-territory MRI pattern. Thus, the diagnosis in this case was supported by the convergence of the clinical syndrome, infarct distribution, and vascular anatomy rather than by any single imaging finding.

The present patient demonstrated profound neurological impairment at presentation, with a Glasgow Coma Scale score of E1V1M4 and an NIHSS score of 40. Despite the relatively limited infarct volume on MRI, bilateral involvement of the paramedian thalami can result in severe impairment of consciousness due to disruption of the ascending reticular activating system [2,4,8]. His level of consciousness gradually improved with conservative management and rehabilitation; by transfer, he could communicate verbally but remained wheelchair dependent, with the mRS score improving from 5 to 4. Reliable serial assessments of vertical gaze and memory were not available in the retrospective record. More broadly, severe neurological presentations may not be fully explained by or reflected in early imaging alone. Although the underlying mechanism differs, Wolie et al. [9] similarly emphasized the importance of integrating serial neurological assessment with available imaging in a patient with severe initial neurological impairment and initially unrevealing head CT findings [9].

Conclusion

We reported a case of bilateral paramedian thalamic infarction strongly suggestive of artery of Percheron infarction. Delayed DSA demonstrated a perforating artery arising from the left P1 segment with anatomy consistent with an AOP, thereby supporting the diagnosis. The angiographic finding should not be regarded as direct proof that this vessel was the acute culprit. In patients presenting with bilateral paramedian thalamic infarction and impaired consciousness, AOP infarction should be considered, and delayed vascular imaging may provide useful anatomical information in selected cases.

Patient consent

Written informed consent for publication of this case report and accompanying images was obtained from the patient and/or the patient's legal representative.