A 58-year-old man comes to the emergency department due to a 3-hour history of abrupt-onset weakness and numbness of the right lower extremity, as well as urinary incontinence. Two months ago, the patient was hospitalized due to left-sided weakness that resolved spontaneously after several hours. At that time, MRI of the head and MR angiography of the head and neck were normal, but the patient was found to have atrial fibrillation. An oral anticoagulant was prescribed at discharge, but the patient has been nonadherent with therapy. Blood pressure is 162/94 mm Hg and pulse is 102/min and irregularly irregular. Physical examination shows weakness and sensory loss in the right lower extremity. Babinski sign is present on the right. Speech is normal, and there is no facial weakness. Examination of the right upper extremity and the left extremities is unremarkable. An embolic occlusion affecting which of the following vascular regions is the most likely cause of this patient's current symptoms?

Question

A 58-year-old man comes to the emergency department due to a 3-hour history of abrupt-onset weakness and numbness of the right lower extremity, as well as urinary incontinence.  Two months ago, the patient was hospitalized due to left-sided weakness that resolved spontaneously after several hours.  At that time, MRI of the head and MR angiography of the head and neck were normal, but the patient was found to have atrial fibrillation.  An oral anticoagulant was prescribed at discharge, but the patient has been nonadherent with therapy.  Blood pressure is 162/94 mm Hg and pulse is 102/min and irregularly irregular.  Physical examination shows weakness and sensory loss in the right lower extremity.  Babinski sign is present on the right.  Speech is normal, and there is no facial weakness.  Examination of the right upper extremity and the left extremities is unremarkable.  An embolic occlusion affecting which of the following vascular regions is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

11ec160b_35b9_99fa_9249_450f299930a8_MD0001_00 This patient has had a stroke, resulting in motor and sensory deficits of the right leg (sparing the right arm). Based on the somatotopic organization of the brain (ie, homunculus), this is suggestive of a lesion affecting the medial portions of the left primary motor and somatosensory cortices. The patient's urinary incontinence is further suggestive of a lack of cortical inhibition of the micturition reflex, which occurs primarily in the frontal micturition center (medial frontal lobe). These areas are all supplied by the anterior cerebral artery. The Circle of Willis is somewhat protective against ischemic injury because it provides a potential alternate pathway for cerebral arterial blood flow. The anterior communicating artery (ACom) provides an anastomotic pathway between the bilateral anterior cerebral arteries, which may limit the severity of infarction if occlusion occurs proximal to the ACom (Choice B). Therefore, in a symptomatic anterior cerebral artery stroke, it is more likely that the obstruction is located distal to the origin of the ACom, where collateral blood flow does not occur. (Choice C) The inferior division of the middle cerebral artery (MCA) supplies the lateral portions parietal and temporal cortices. Occlusion typically causes sensory deficits of the arm and face, with sparing of motor function. In addition, visual field defects, Wernicke aphasia (dominant hemisphere), and profound hemineglect (nondominant hemisphere) often occur. (Choice D) The superior division of the MCA impacts the frontal lateral cortex, resulting in motor and, sometimes, sensory deficits that impact the face and arm. Broca aphasia (dominant hemisphere) is common. Hemineglect (nondominant hemisphere) is variable. (Choice E) Occlusion of the proximal MCA (ie, MCA stem infarct) results in profound defects due to the large area impacted. Deficits include hemiparesis, hemianesthesia, global aphasia (dominant hemisphere), hemineglect (nondominant hemisphere), gaze preference, and visual deficits (homonymous hemianopia). Educational objective: The anterior cerebral artery supplies the medial aspects of the frontal and parietal lobes. Occlusion can lead to sensory and motor deficits of the contralateral leg. Occlusion of the anterior cerebral artery distal to the anterior communicating artery can lead to more severe symptoms because there is no collateral blood flow from the Circle of Willis.

A 58-Year-Old Man Comes to the Emergency Department Due to a 3-Hour