A 68-year-old woman is brought to the emergency department due to right-sided weakness and double vision. The patient was well when she went to bed last night, but on waking, she had difficulty getting out of bed. She has a 20-year history of hypertension and type 2 diabetes mellitus. Blood pressure is 162/90 mm Hg and pulse is 84/min. On physical examination, the left eyelid is drooping, and the patient is unable to raise it. The left eye is deviated laterally, and the pupil does not constrict with either direct or consensual light stimulation. Extraocular movement in the right eye is normal, with brisk pupillary response. The right corner of the mouth droops slightly. Muscle weakness in the right arm and leg is present; muscle strength and reflexes in the left arm and leg are normal. Sensation to light touch and pain is intact bilaterally. Which of the following is the most likely diagnosis in this patient?

Question

A 68-year-old woman is brought to the emergency department due to right-sided weakness and double vision.  The patient was well when she went to bed last night, but on waking, she had difficulty getting out of bed.  She has a 20-year history of hypertension and type 2 diabetes mellitus.  Blood pressure is 162/90 mm Hg and pulse is 84/min.  On physical examination, the left eyelid is drooping, and the patient is unable to raise it.  The left eye is deviated laterally, and the pupil does not constrict with either direct or consensual light stimulation.  Extraocular movement in the right eye is normal, with brisk pupillary response.  The right corner of the mouth droops slightly.  Muscle weakness in the right arm and leg is present; muscle strength and reflexes in the left arm and leg are normal.  Sensation to light touch and pain is intact bilaterally.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d5b2_1fe8_bc81_611e0c7ac34d_MD0003_00 This patient with risk factors for stroke (eg, hypertension, diabetes mellitus) has crossed signs of: left oculomotor nerve (CN III) dysfunction (eg, ptosis, impaired pupil constriction, down-and-out eye, diplopia). right (ie, contralateral) face, arm, and leg weakness. Facial weakness impacts only the lower face, which is consistent with an upper motor neuron pattern. Because the brainstem is where most cranial nerves originate and many motor and sensory fibers cross the midline, acute ipsilateral cranial nerve deficits accompanied by contralateral hemiparesis or hemisensory loss (ie, crossed signs) are consistent with brainstem stroke. CN III originates in the midbrain of the brainstem, further localizing the lesion. In addition, facial weakness has an upper motor neuron pattern (spares the upper face), indicating that the lesion is above the pons. Left CN III palsy with contralateral weakness of the lower face (corticobulbar tract), arm, and leg (corticospinal tract) is most likely caused by a left midbrain infarction due to occlusion of mesencephalic branches of the posterior cerebral artery (ie, Weber syndrome). This syndrome can also develop due to obstruction of the perforating arteries of the basilar bifurcation. (Choice A) Infarctions in the left hemisphere (supplied by anterior, middle, and cerebral arteries) can cause contralateral (ie, right-sided) weakness, as seen in this patient. However, aphasia is frequently present (language lateralizes to the left hemisphere in most patients), and homonymous hemianopia is common, depending on the location of the occlusion (eg, middle vs posterior cerebral artery). Cranial nerve deficits are not usually seen. (Choices C and E) Pontine infarctions (due to occlusion of paramedian arteries arising from the basilar artery) can cause ipsilateral cranial nerve deficits with contralateral hemiparesis. However, the cranial nerves typically involved originate in the pons: trigeminal (CN V) (facial paresthesia), abducent (CN VI) (abducens palsy), facial (CN VII) (facial palsy), and vestibulocochlear (CN VIII) (vertigo). Pontine infarctions would not usually cause CN III deficit. originate in the pons (Choice D) Because midbrain infarctions cause ipsilateral cranial nerve deficits and contralateral arm and leg weakness, right midbrain infarction would cause right (vs left) CN III palsy with left (vs right) weakness of the lower face, arm, and leg. Educational objective: Crossed signs (ie, cranial nerve dysfunction with contralateral limb weakness) raise suspicion for a brainstem stroke. A midbrain infarction due to occlusion of the posterior cerebral artery results in Weber syndrome, which is characterized by ipsilateral oculomotor nerve (CN III) dysfunction accompanied by contralateral hemiparesis. References: Weber syndrome secondary to brain stem tuberculoma. (http://www.ncbi.nlm.nih.gov/pubmed/29941767)

A 68-Year-Old Woman Is Brought to the Emergency Department Due