What are the five layers of the scalp?
Skin, subcutaneous fat, galea aponeurotica, loose areolar tissue, and pericranium (remembered by the mnemonic: SCALP).
What fascial structure connects the frontalis muscle anteriorly to the occipitalis muscle posteriorly?
The galea aponeurotica.
What is the significance of the temporal line of the calvarium?
It is the line along which the deep temporal fascia fuses with the pericranium.
What is the pericranium?
The pericranium is the periosteum of the calvarial bones.
Which region of the scalp offers the greatest mobility?
The parietal region, located over the temporoparietal fascia.
What blood vessels supply the scalp?
The paired supratrochlear, supraorbital, superficial temporal, posterior auricular, and occipital blood vessels.
Which arteries are branches of the internal carotid artery? Which are branches of the external carotid artery?
The supratrochlear and supraorbital arteries arise from the ophthalmic artery, which is the first branch of the internal carotid artery. The others are branches of the external carotid artery.
What is the sensory innervation of the scalp?
The paired supratrochlear (V1) and supraorbital (V1) nerves, which supply forehead and frontoparietal scalp; the zygomaticotemporal (V2) nerve, which supplies the region lateral to the brow and the temporal region; the auriculotemporal (V3) nerve, which supplies the lateral scalp; and the greater occipital (C2) and lesser occipital (C2–3) nerves, which supply the occipital region.
On the deep surface of the temporoparietal fascia within the loose areolar tissue, along an imaginary line that connects the ear lobe to a point 1.5 cm above the lateral eyebrow (Pitanguy line).
What are the three layers of the calvarium?
Outer table, diploic space, and inner table.
What are the bones of the calvarium, and by which process are they formed during development?
The frontal, parietal, and temporal bones are formed by intramembranous ossification. The occipital and sphenoid bones are formed by endochondral ossification.
By what age is calvarial growth complete?
Calvarial growth is generally complete by 7 years of age.
What is aplasia cutis congenita?
Aplasia cutis congenita is a rare congenital disorder characterized by a localized absence of skin, dermal appendages, and, in some cases, subcutaneous tissues. Although it may occur anywhere on the body, the majority occurs on the scalp. In 15% to 30% of cases, aplasia cutis congenita may be associated with defects of the underlying skull or dura, exposing the brain and sagittal sinus, which can be life threatening.
How is aplasia cutis congenita treated?
The best treatment strategy remains a subject of debate. Small wounds that do not involve dura, brain, or sagittal sinus exposure can be managed conservatively with moist dressings. When the dura with enlarged veins, the brain, or the sagittal sinus are exposed, emergency coverage with skin grafts, allografts, or flap reconstruction may be indicated to prevent bleeding and infection. Many calvarial defects exhibit spontaneous bone growth, while others may need delayed cranioplasty.
Do all scalp defects require reconstruction?
No. Some partial-thickness defects may be left to heal by secondary intention. However, contracture may result, and the scar may have limited or no hair growth.
What factors may preclude use of local flaps for scalp reconstruction?
Wounds in which tension-free, broadly based flaps cannot be created. Also, prior radiation, surgery or infection, as well as tobacco use, corticosteroid use, or diabetes mellitus may result in flap loss or impaired wound healing and are relative contraindications.
Which scalp wounds are most amenable to primary closure?
Small scalp defects, usually less than 3 cm in diameter. Wide undermining is usually required since the scalp tissues have limited elasticity. Galeal scoring may be a useful adjunct.
Which scalp wounds are most amenable to skin grafting?
Those with a well-vascularized base for accepting the graft, such as those with intact fascia or pericranium.
Burring of the outer table until the vascularized diploic space is reached. Galeal, temporoparietal fascia, or pericranial flaps may also be rotated over calvarial bone prior to skin graft placement and will improve graft survival.
What are the drawbacks of skin grafting for scalp reconstruction?
Potential graft loss, especially when radiation is given, alopecia, poor color and thickness match, shiny appearance, and breakdown following even relatively minor trauma.
What are the potential benefits of acellular biologic matrices for scalp reconstruction?
Unlimited supply, no donor site morbidity, can be placed on minimally perfused surfaces, and may decrease need for flap reconstruction.
What are the potential downsides to using an acellular biologic matrix for scalp reconstruction?
May require skin grafting as a second procedure, requires a vascularized wound bed, alopecia, and prone to infection prior to becoming vascularized.
What are the benefits of tissue expansion in scalp reconstruction?
Tissue expansion can facilitate closure of wounds involving up to 50% of the scalp with hair-bearing tissue.
What are the drawbacks of tissue expansion in scalp reconstruction?
Frequent complications (up to 25%), including expander extrusion and infection, particularly in previously radiated tissues. Several weeks may be needed for healing and expansion after initial placement, making this a suboptimal technique for primary reconstruction when adjuvant therapy is indicated. A noticeable decrease in hair density may also occur.