DNA replication is one of the most basic processes that occurs within a cell. Each time a cell divides, the two resulting daughter cells must contain exactly the same genetic information, or DNA, as the parent cell.
Other, less common causes of radial nerve palsy in the arm include compression at the fibrous arch of the lateral head of the triceps and compression by an accessory subscapularis-teres-latissimus muscle.
1 Fourth nerve palsy is often a congenital birth defect, which means that a baby is born with it. But a head injury, stroke, or tumor can also cause fourth nerve palsy.  The sixth cranial nerve can be damaged by infection, a stroke or tumor, increased pressure in the brain, and even migraines.