Tam-o-shanter skull

A cap is a form of headgear. Caps have crowns that fit very close to the head. [Source: Wikipedia ]

Synonyms
Thickening of skull vault with basilar invagination
May Be Caused by
 Common
Paget disease of bone
 Uncommon
Fibrous dysplasia
Neurofibromatosis
Osteogenesis imperfecta
Osteomalacia
Rickets