A rare stroke case with bilateral paramedian thalamic and mesencephalic involvement

Introduction: This report presents a rare stroke case with bilateral paramedian thalamic and mesencephalic involvement.Case: A 76-year-old man was evaluated in our emergency outpatient clinic for sudden-onset diplopia, speech disturbance, dizziness, and loss of balance while walking. Medical history: asthma and lumbar radiculopathy. Neurological examination (abnormal findings): restricted downward and outward gaze bilaterally, 1–2 beats of nystagmus on upward gaze, dysarthric speech, and ataxic gait. Brain diffusion MRI, carotid and brain CT angiography, cardiac evaluation, and biochemical laboratory tests were used. DWI showed diffusion restriction with an ADC correlate in the bilateral paramedian region of the medial midbrain, which was considered consistent with infarction of the artery of Percheron. Carotid and brain CT angiography showed no significant stenosis. On cardiac evaluation, the ECG showed sinus rhythm and EF was 60%; on 72-hour rhythm Holter monitoring, the underlying rhythm was sinus, and no malignant arrhythmia or deep bradycardia was detected. LDL was 82 mg/dL, and atorvastatin 10 mg was started. Dual antiplatelet therapy was started until the etiology could be determined (Figure 1).Discussion/Conclusion: The artery of Percheron is a rare anatomical variant in which a single trunk arises to supply the medial and inferior parts (paramedian regions) of both thalami. Occlusion of this artery can lead to bilateral thalamic infarction and, in some cases, midbrain involvement. Bilateral paramedian thalamic involvement usually produces the triad of altered consciousness, supranuclear vertical gaze palsy, and memory loss. It can also give rise to a mesencephalothalamic or thalamopeduncular syndrome that includes oculomotor disturbances, hemiplegia, cerebellar ataxia, and movement disorders. Occlusion of the artery of Percheron has been reported to account for approximately 0.1–2% of all ischemic strokes and approximately 4–18% of thalamic ischemic strokes. There are four infarct types: bilateral paramedian thalamic and midbrain infarction (most common, 35–43%) (our patient); isolated bilateral paramedian thalamic infarction (35–38%); bilateral paramedian thalamic, anterior thalamic, and midbrain infarction (14–26%); and bilateral paramedian thalamic and anterior thalamic infarction without midbrain infarction (least common, 5–6%). This case is presented because the oculomotor findings, diplopia, dysarthria, and imbalance, together with bilateral paramedian involvement on diffusion MRI, suggested the rare occlusion of the artery of Percheron, and because of its rarity in clinical practice (Figure 2).Keywords: