Which strokes make the afflicted unable to speak?

Broca's area: Strokes that affect the language center (broca's area) usually in the left side of the brain result in speech disturbance and often weakness or paralysis of the right arm and leg. This can be due to impaired circulation due to hardening of the arteries or hemorrhage due to hypertension. In left handed patients the anatomy is reversed and the speech center may be on the right side of the brain.

Left side: Most commonly strokes affecting the left side of the brain can include the areas that control language and affect speaking. A good evaluation is necessary to determine which area is affected, if the problem is also associated with problems with language comprehension, or if there are problems affecting the muscles that need to work properly to speak.