Contralateral

Contralateral means situated on, or relating to, the opposite side of the body or a reference point. Etymologically, it comes from the Latin contra, meaning opposite, and lateralis, meaning side.

In anatomy and neurology, contralateral organization is common because many neural pathways cross to the opposite side. Examples include the corticospinal tract, which decussates at the medullary pyramids to produce motor control on the opposite side of the body; the spinothalamic tract, which crosses within the spinal cord to convey pain and temperature to the contralateral brain; and the dorsal columns, which ascend ipsilaterally before crossing in the brainstem. In the brain, the right hemisphere largely processes sensory and motor information from the left side, and vice versa, reflecting a contralateral representation of the body.

Clinically, a lesion in one cerebral hemisphere often yields contralateral deficits in movement, sensation, or perception. For example, a left hemisphere stroke may cause right-sided weakness and sensory loss, or visual field deficits if optic radiations are involved. Another related phenomenon is contralateral neglect, typically from right parietal damage, leading to inattention to the left side of space. The term contralateral is also used in surgical planning and diagnostic testing to specify the opposite side relative to a reference point.

See also: ipsilateral, decussation, cross-hemispheric projection.