Each muscle of the skull has a different name, if you want the name of a specific one, you have to indicate where on the skull you are talking about.
Diastasis
Occipital is the term usually used when referring to the base of the skull.
Tetany is the medical term meaning inability to relax the muscles.
Costochondritis is inflammation of the muscles in the ribs
Craniotabes (abnormal softening of the skull )It could also be cranimalacia.cranimalaciaDecomposition...craniomalacia
Colic is the medical term meaning spasm of the visceral muscles.
intercostal muscles - from inter meaning 'between', and costa meaning 'rib'
rigormortis
Myologist is the term meaning specialist in the study of muscles, but an orthopedist is the typical specialist physician who treats muscle problems.
Tetany is the medical term continuous spasm of muscles; tetany may result from hypocalcemia.
Contracture or contraction
They are called sutures. They vary in specific names depending on which piece of the skull are sutured by them.