General Medical Information

The Cranium

Susan D. John
Michael D. Maves

Scalp
The cranium is covered by the hair-bearing scalp, which is divided into layers of skin and subcutaneous tissue, galea aponeurotica, loose connective tissue, and periosteum or pericranium covering the calvarial vault. The blood supply of the scalp comes from the paired supraorbital and supratrochlear arteries anteriorly, the terminal branches of the superficial temporal arteries laterally, and the occipital vessels posteriorly. This rich vascularity provides a network on which small scalp flaps can be based and rotated, as in the management of male pattern baldness. Sensation to the scalp is provided by branches of cranial and spinal nerves.

Calvaria
The bony vault of the cranium, the calvaria, consists of the unpaired frontal bone, the paired parietal bones, and the unpaired occipital bone. In the lateral aspect, the greater wing of the sphenoid bone and the temporal bone complete the cranium. There is a rich layer of diploic bone between the inner and outer tables of the calvaria. This is a source for split-thickness calvarial bone grafts, which often are used in head and neck reconstruction. The calvarium is thickest at the external occipital protuberance and in the parietal region. It is thinnest over the temporal region. This allows ready access for neurotologic operations on the middle fossa. The venous circulation of the calvaria is provided by diploic veins, which drain to the veins of the scalp or into the dural venous sinuses. In some instances the diploic veins are connected to each other, and this communication allows osteomyelitis that originates in the frontal sinus to involve the frontal bone, scalp, and dura.