A Good Neuro Question: The Internal Capsule

Q. A 74 year old women with a long history of Diabetes mellitus is brought to the emergency department with a sudden onset of hemiparesis on the right side of her body. On history she has a 25-pack-per year smoking history, and is currently on metformin and hormone replacement therapy. The patient shows no signs of AMS and answers all questions very well. Her vitals are BP of 144/92 mmHg and PR of 86/min. PE confirms loss of strength in the right upper and lower extremities. There is a right sided facial weakness that is present as well. The visual field is intact. A CT scan of the head is ordered to rule out cranial bleed. Occlusion of which of the following vessels is the most likely cause of this patients symptoms?

A. Anterior cerebral artery

B. Vertebral artery

C. Penetrating arterioles of the anterior limb of the internal capsule

D. Middle cerebral artery

E. Penetrating arterioles of the posterior limb of the internal capsule

F. Posterior cerebral artery

G. Infarction of the corpus callosum 

 

Answer: E. Penetrating arterioles of the posterior limb of the internal capsule

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Lacunar infarcts are small (< 0.5 cm) focal areas of parenchymal loss found in the basal ganglia, anterior or posterior limb of the internal capsule, pons and occasionally cerebral white matter. The five classic syndromes include:

1) Pure motor hemiparesis

2) Pure sensory stroke

3) Sensorimotor stroke

4) Ataxic hemiparesis

5) clumbsy-hand dysarthria

These are presumed to be of ischemic origin and due to occlusion of the penetrating arterioles of the aforementioned structures. Lacunar infarcts are particularly frequent in persons who suffer from hypertension or diabetes mellitus. The most common type of infarct is a pure motor lacunar infarct presenting with motor weakness of the contralateral side without any cortical sings i.e aphasia, agnosia, hemianopsia, neglect etc…

Pure motor infarcts most often occur in the genu of the posterior limb of the internal capsule where the descending corticospinal and corticobulbar tracts are located. Infarction of the anterior limb most often results in ataxic hemiparesis where both the pyramidal weakness and frontopontocerebellar (ataxia) systems are located

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