0071598626.pdf

388 Emergency Medicine

351.The answer is d.(Rosen, pp 1434-1435.)The CT image shows a large
hypodensity in the right parietal-occipital region representing an ischemic
stroke.Ischemic strokes comprise 80%of all strokes, with hemorrhagic
strokes accounting for the other 20%. Ischemic events include thrombotic
(thrombus forming at the site of an ulcerated atherosclerotic plaque), embolic
(thrombus embolized to a distal site), and lacunar(small terminal artery
occlusion) strokes. This patient likely had a cardioembolic secondary to atrial
fibrillation. Atrial fibrillation is an important risk factor for an embolic stroke,
particularly when patients are noncompliant with anticoagulation therapy,
as the patient in the vignette. Intracranial bleeding secondary to a hemorrhagic
event appears hyperdense on CT scan. The diagram above illustrates the
cerebral circulation.

352.The answer is b.(Rosen, pp 253-254.)ConsiderMSas a diagnosis in
presentations of various neurologic symptoms that are difficult to explain by a
single CNS lesion, particularly those occurring in a female in her third decade
of life. MS is a multifocal demyelinating CNS diseasethat in 30% of cases ini-
tially presents with optic neuritis(unilateral eye pain and decreasedvisual acuity).

Ant. cerebral A.

Ant. choroidal A.

Post. cerebral A.

Middle cerebral A.

Deep branches of

middle cerebral A.

Body of

caudate

Internal

capsule

Putamen

Claustrum

Globus

pallidus

Uncus

Subthalamic body

Red nucleus

Thalamus

(Reproduced, with permission, from Kasper DL et al. Harrison’s Principles of Internal
Medicine. New York, NY. McGraw-Hill, 2005: 2381.) (Courtesy of CM Fisher, MD.)