Which physical examination finding is most likely in a patient who suffered a stroke in the right cerebral peduncle?

In the context of a stroke affecting the right cerebral peduncle, the most likely physical examination finding is left-sided hemiparesis. This can be attributed to the way the motor pathways are organized in the brain. The right cerebral peduncle carries motor signals from the cerebral cortex to the brainstem and spinal cord. When a stroke occurs in this area, it disrupts the pathways that control movement on the opposite side of the body.

The motor pathways cross over (decussate) at the level of the medulla or in the spinal cord, which means that damage to the right side of the brain will result in weakness or paralysis on the left side of the body. Thus, left-sided hemiparesis is the expected finding when there is damage to the right cerebral peduncle due to a stroke.

Other potential findings might include difficulty with coordination and movement, but the primary manifestation would be weakness on the contralateral side of the body, specifically left-sided hemiparesis in this case.