Some Common Neurological Constructs.

1.Subcortical (e.g., internal capsule) versus cortical lesion: Motor weakness (paresis) usually affects the face, arm, and leg equally.Primary sensory deficits (paresthesia, numbness) are more prominent because of involvement of the posterior limb of the internal capsule. Cortical lesions affect higher cortical sensory, manifesting as agnosia, agraphesthesia, and impairment of double simultaneous stimulation.Visual field defects are more common because visual tracts travel through the posterior limb of the internal capsule. Occipital lobe lesions produce visual field defect, but usually are not associated with motor or sensory deficit.Speech dysarthria is more common. A dominant cortical lesion produces aphasia and apraxia.2.Gerstmann's syndrome. This syndrome is commonly caused by a stroke affecting the left angular and supramarginal gyrus and clinically characterized by finger agnosia, left-right disorientation, agraphia, and dyscalculia.3.Watershed or border zone infarcts. Watershed areas are end-artery zones between superficial branches of a major cortical blood supply such as between the anterior cerebral artery-middle cerebral artery and middle cerebral artery-posterior cerebral artery. Bilateral watershed infarcts occur in severe hypotension or hypoxia, and unilateral watershed infarcts occur when the affected artery is stenotic, and collateral circulation cannot compensate in a hypotensive episode. [ABSTRACT FROM AUTHOR]