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Introduction The AOP is a rare anatomic variant in which a solitary arterial trunk arises from the proximal segment of the posterior cerebral artery (PCA) and supplies the bilateral paramedian thalami and rostral midbrain. Occlusion may result in variable bilateral thalamic and midbrain infarcts. The clinical presentation is most commonly lethargy and somnolence thought to lack other localizing features. Often the diagnosis and treatment of stroke is delayed. Methods Here we present two cases of likely AOP infarcts which highlight the importance of considering this diagnosis on the differential of acute lethargy as timely treatment can lead to a significant difference in morbidity and mortality. Results Case 1: A 68‐year‐old male was initially admitted to an outside hospital with acute lethargy. He was transferred to our institution where he was found to be somnolent and required repeated stimulation to participate with interview. On further exam he was noted to have left ptosis, anisocoria, restricted left supra‐ and add‐ duction, and dysarthria. CT angiogram (CTA) showed no large vessel occlusion (LVO) or significant stenosis. Magnetic resonance imaging (MRI) demonstrated acute infarcts in the medial thalami and subthalamic nuclei bilaterally and uppermost portion of the midbrain. He was out of the window for IV thrombolytic. He was ultimately discharged to inpatient rehab with a persistent CN III palsy. Case 2: A 71‐year‐old female was evaluated emergently via telestroke for acute lethargy and was found to additionally have vertical diplopia, right facial palsy, and subsequent bilateral numbness of the face, arms, and legs. NIHSS 10 for LOC questions (1), facial palsy (2), motor drift (1 pt for each limb), sensory loss (1), aphasia (1), and dysarthria (1). She was treated with IV tenecteplase 179 minutes after the last known well and ultimately had complete symptom resolution. CTA was negative for LVO or significant stenosis. MRI brain demonstrated acute infarcts in the medial thalami bilaterally. Conclusion Here we present two cases of acute onset lethargy. MRI Brain revealed relatively symmetric restricted diffusion in the bilateral thalami of both patients suggesting the presence of an AOP variant. In contrast to the first case, signs of a posterior circulation infarct were quickly recognized in the second patient and IV thrombolytic administration resulted in return to baseline. In both cases there were subtle neurologic findings that suggested midbrain involvement – ptosis, restricted ductions, anisocoria. A high level of suspicion for bilateral thalamic infarct and potential AOP variant should be maintained in cases of acute lethargy. Careful neurologic exam often reveals other signs suggestive of posterior circulation infarct and timely therapeutics can significantly improve morbidity and mortality. |
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