After a right hemisphere stroke, which finding indicates a patient has left lingual weakness during oral peripheral mechanism examination?

A protrusion of the tongue to the left of midline is indicative of left lingual weakness following a right hemisphere stroke. This occurs because the motor control for the tongue is primarily located in the opposite hemisphere of the brain. When a stroke affects the right hemisphere, it can lead to weakness or paralysis on the left side of the body, including the left side of the tongue.

In this context, if the tongue protrudes to the left of the midline, it signifies that the left side is weaker and unable to exert the same force as the right side, causing it to deviate in that direction. This weakness may manifest as difficulty in controlling the tongue, resulting in an asymmetrical posture when extended.

The other options do not reflect the same specific sign of left tongue weakness. While deviation to the right or absence of movement may indicate other types of impairments, they do not specifically delineate left lingual weakness post-right hemisphere stroke. Additionally, a deviation of the tongue to the midline may suggest an absence of unilateral weakness, aligning more with normal functioning rather than indicating a lateralized weakness.