Cranial defects are partly due to open cranial trauma or firearm penetrating injuries and partly due to surgical decompression, penetrating damage due to craniosynostosis or removal of cranial lesions. So, what are the causes of cranial defects? The following are the causes of cranial defects: 1, pediatric growth skull fracture. 2.Severe cranial injury or other types of cranial surgery for debridement and decompression as required by the condition. 3.Open craniocerebral trauma or firearm penetrating injury. 4, Cranial osteomyelitis and other lesions of the skull itself caused by penetrating cranial destruction or surgery to remove cranial lesions. 5.Crushed or depressed skull fractures that cannot be repositioned after reopening surgery.