Case 7: Only Paralyzed
On his latest visit, this patient had severe paralysis of the lower part of the face, arm, and leg, all on the same side. Stretch reflexes in the arm and leg were brisk, and muscle tone was increased. The plantar response was dorsiflexor. He had marked dysarthria, but no other findings that suggest a large cortical infarct like a visual field or sensory defect, aphasia, or neglect. In fact, all other aspects of his neurologic exam were normal.
Diagrams
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Occlusion of a single lenticulostriate branch
Note
Expert Note Case 7.
Only Paralyzed
The lenticulostriate branches are small diameter penetrating arteries that arise directly from the MCA stem and supply most of the internal capsule and basal ganglia. Blockage of a branch that supplies the internal capsule may produce a tiny infarct (or lacune) in the posterior limb of the internal capsule where the corticobulbar and corticospinal tracts run on their way from the motor cortex to the brainstem and spinal cord. Corticobulbar fibers are believed to lie in the most anterior in the posterior limb, followed in turn by corticospinal fibers for arm and then the leg. Depending which lenticulostriate branch is occluded, a lacunar infarct might affect only part of these fibers, producing contralateral paralysis of just the lower face and arm, or perhaps just of the arm and leg.
In this patient, a tiny lacunar stroke produced major deficits because of its location. In other cases, small lacunar strokes produce no abnormalities detectable on neurologic exam. The old real estate broker's adage about 'location, location, location' is particularly applicable in this situation. Spontaneous unwanted, involuntary movements (so-called extrapyramidal motor syndromes) following an ischemic stroke are rare, but when they occur they may be the consequence of occluding lenticulostriate vessels that normally supply the basal ganglia.