Spinal Cord Myelopathy: Sometimes, the vertebrae of achondroplastic children do not grow enough to allow sufficient space for nerves exiting and entering the spinal cord to pass in and out of the bony spinal column. If only a single nerve root is compressed, a child may experience pain, numbness or weakness in a specific arm or leg. They may seem to prefer using one hand over another very early as babies, or complain of pain in their back or affected arm. In more severe cases, the entire spinal cord can be compressed, causing weakness and numbness in the entire body below the spinal cord pinch as well as loss of bowel and bladder control.