Lesions of the Scalp
eEdE-56
Dilan Samarawickrama, M.D.
Ashok Srinivasan, M.D.
University of Michigan
Disclosures
• The authors have no relevant financial
disclosures.
Objectives
1. Review the anatomy of the scalp,
including the blood and nerve supply
2. Review pathologies that involve the scalp
Scalp Anatomy
Layers of the Scalp
 The scalp has 5 layers
1. Skin
2. Subcutaneous connective tissue
3. Gala aponeurotica
4. Subgaleal loose areolar connective tissue
5. Periosteum of the skull (also called the
pericranium)
Epidermis (red arrow)
Dermis (yellow arrow)
containing coarse collagen
Subcutaneous fat
(green arrow)
Vessels running adjacent to
the galea (blue arrow)
Epidermis (red arrow)
Dermis (yellow arrow)
containing coarse collagen
and vascular plexus
Subcutaneous fat
(green arrow) with
traversing fibrous strands
Occipitalis muscle
(orange arrow)
BTFE 3D sequence
Skin of the Scalp
 The skin contains hair follicles, sebaceous
glands, and sweat glands.
 It is the thickest skin in the body.
 On imaging, the skin will enhance after
contrast due to the rich subdermal plexus.
Subcutaneous Tissue
 This is a thin layer of fat with fibrous strands
splitting the fat into lobules. The fibrous
strands connect the dermis to the galea.
 This layer is rich in vessels and lymphatics.
 The blood vessels in this layer are attached
to the crossing the dermis. If they are cut,
they are unable to vasoconstrict due to their
attachments. This is why scalp lacerations
can bleed profusely.
Galea Aponeurotica
 This is a dense fibrous layer that extends
over the vertex between the frontalis muscle
anteriorly and the occipitalis muscle
posteriorly. It blends in laterally with the
temporalis fascia. The galea is thick at the
vertex and thinner in the temporal region.
 The major arteries course along the galea.
From here, these arteries ramify superiorly
into the subdermal plexus.
Subgaleal Connective Tissue
 It is thought to be an avascular tissue, but there are fine
vessels coming from the galea and skull. Emissary veins
also course in this area and communicate with the
sinuses.
 This loose layer is what allows the scalp to glide over the
skull. Because of this looseness, this layer is what
results in scalp avulsions with trauma. This is also the
layer surgeons use to create scalp flaps.
 Blood that collects in this layer eventually pools around
the eyes (“raccoon eyes”) due to obstruction in other
directions from fascia or muscle.
Importance of the Emissary Veins
 There are two important points regarding the
emissary veins in the subgaleal tissue
1. Rupture of the veins can lead to subgaleal
hemorrhage. These veins may be torn during
delivery, particularly vacuum-assisted deliveries,
leading to significant hematoma in the newborn
scalp.
2. These vessels can spread infection
intracranially as the emissary veins communicate
with the dural venous sinuses.
Pericranium
 The pericranium is firmly attached at the
sutures. But in between, it is loosely attached
to the bone.
 Subperiosteal hematoma can lead to tension
on the periosteum and ossification of the
periosteum.
Sensory Innervation of the Scalp
 The sensory innervation of the scalp is
primarily from branches of cranial nerve V
and the rami of C2 and C3.
 The cranial nerve V1 branch innervates the
forehead. The cranial V3 branches innervate
the temple and anterior periauricular region.
 The occipital nerves, which arise from C2 and
C3, innervate the vertex, posterior scalp, and
posterior periauricular region.
Importance of the
Innervation of the Scalp
 While headache can have many causes, compression of
the nerves to a region of scalp may lead to the sensation
of headache. For example, the zygomaticotemporal
nerve passes through the temporalis muscle to innervate
the temple and the occipital nerves pass through
posterior cervical muscles to innervate the posterior
scalp. Muscle tension may cause compression on these
nerves and the feeling of headache.
 Damage to the nerves during surgery may cause
neuralgias of the head.
Arterial Supply of the Scalp
 Each side of the scalp has 5 major arteries.
Two arterial branches from the ophthalmic
artery supply the forehead. However, the
major arterial supply to the scalp is from the
external carotid artery branches, including the
superficial temporal artery, occipital artery,
and posterior auricular artery.
 The scalp has extensive arterial
anastamoses. With just one temporal artery,
the entire scalp can remain viable.
Tumors of the Scalp
Atypical Fibroxanthoma
 AFX typically presents as an ulcerated nodular lesion on
severely sun damaged skin in patients in elderly patients.
 75% occur in the head and neck. The scalp and ear were
identified as the most common sites of presentation in 65%
and 23% of cases, respectively.
 They are now regarded as cases of dermatofibrosarcoma
protuberans (DFSP), which are more recently referred to as
atypical benign fibrous histocytoma.
Atypical Fibroxanthoma
These occur in skin damaged by sun/UV radiation.
Differential for Malignant Scalp Masses in Adult
 The most common malignant scalp tumors
(in Taiwanese patients) in order of frequency
found in one study by C.S. Chiu et al.
1. Basal cell carcinoma (44% of cases)
2. Squamous cell carcinoma (17% of cases)
3. Metastases to the scalp (13% of cases)
4. Angiosarcoma (7% of cases)
 Melanoma only accounted for 2% of cases
Basal Cell Carcinoma
Squamous Cell Carcinoma
The vertex of the scalp is a common location for
primary scalp tumors. Notice how even the scout
shows subtle thickening of the skin.
Melanoma
The vertex of the scalp is a common location for primary
scalp tumors, particularly those linked with sun exposure.
Melanoma
This is just one section of a patient with a scalp melanoma
that was much larger on adjacent sagittal slices. But notice
the subtle thickening of the skin relative to the rest of the
skin. Evaluation of the scalp on sagittal or coronal images
is very useful as small lesions may be easily missed on
axial images due to adjacent bone.
Metastasis to the Scalp
 The most common tumors to metastasize
to the scalp in order of frequency
1. Lung cancer (23%)
2. Colon cancer (12%)
3. Liver cancer (8%)
4. Breast cancer (8%)
Primary Undifferentiated Sarcoma
Congenital Scalp Mature Teratoma
Extragonadal germ cell
tumors of the head and
neck only account for 5%
of all germ cell tumors in
children. Those located in
the scalp are very rare.
This mass was excised
and was a teratoma on
pathology.
Congenital Lesions
Congenital Inclusion Cysts of the Scalp
 Dermoid cysts have a peak age distribution in the
1st decade. In general, dermoid cysts are more
common that epidermoid cysts in children. They
tend to occur in the midline, and can occur over the
anterior fontanel.
 Both epidermoid cysts and dermoid cysts are
inclusion cysts due to epithelial rests. Dermoid
cysts are distinguished from epidermoid cysts by the
presence of hair, sebaceous glands, and sweat
glands.
Congenital Inclusion Cysts of the Scalp
 Inclusion cysts are usually present at birth and can
develop gradually as secretion and internal
desquamation accumulate. Exocrine glands in the
cysts secrete a fluid similar to sweat.
 Dermoid cyst have been described as hyperintense
on T1 with variable signal on T2. But if the internal
fat content is relatively low, the lesion will reveal
CSF-like signal intensity on T2.
Dermoid Cyst
Dermoid Sinuses of the Scalp
 In the head, the most common location is
the external occipital protuberance (85%).
The next most common locations are the
nasion (11%) and the posterior parietal
area (5%).
 The depth to which they penetrate can
vary. Occipital dermoid sinus may extend
to the dura mater or further intracranially.
Fluid Collections in the Scalp
Fluid Collections in the Newborn Scalp
 Caput succedaneum is a serosanguinous, extraperiosteal fluid
collection that occurs due to pressure on the skull during vaginal
delivery. On imaging, it crosses suture lines.
 Subgaleal hematoma results from rupture of emissary veins during
delivery, especially vacuum-assisted deliveries. Like caput, it
crosses suture lines. It will have typical features of hematoma, such
as hyperdensity on CT and T1 hyperintensity on MRI. Newborns can
have significant hemorrhage into the subgaleal potential space and
develop shock.
 Cephalohematoma occurs beneath the periosteum. It will be limited
by the periosteal attachments to suture lines.
Caput Succedaneum
Fluid collection crossing suture lines
Calcified Cephalahematoma
Most cephalohematomas will resorb. But a
few can develop ossification of the overlying
periosteum and persist.
Chronic Abscess
There is a thickened
ring of periosteum. Air is
present in the abscess.
This was due to
Actinomycosis.
Vascular Lesions
Atretic Encephalocele with
Persistent Falcine Sinus
 These rare lesions generally occur within a few
centimeters of the lambda.
 They contain meninges and neural rests.
 Embryonic positioning of the straight sinus
(persistent falcine sinus) has frequently been
identified in these lesions.
Atretic Encephalocele with
Persistent Falcine Sinus
•
The internal cerebral veins meet, but then rise vertically as the falcine
sinus (red arrows). The normal straight sinus is not present (blue arrows).
The small subscalp protrusion is the atretic encepahlocele.
Cirsoid Aneurysm
This is a misnomer. This is an arterio-venous fistula of
scalp vessels. The term cirsoid aneurysm is used due to
variceal dilatation of the draining veins
(Greek kirsos = varix).
The majority occur as congenital anomalies, although
10-20% develops following penetrating trauma to the scalp.
In one series of 21 cases by Gurkalar et al., the superficial
temporal artery was involved in 90% of cases. It was the
primary arterial feeder in 70% of their cases.
Sinus Pericranii
 This purely venous entity is characterized by an
anomalous communication between the
intracranial dural sinuses (usually the superior
sagittal sinus) and dilated scalp veins
 The varicosities are intimately associated with
the periostium, are distensible, and vary in size
with changes in intracranial pressure
Sinus Pericranii
AVM
• MRI shows increased flow voids in the scalp. Angiogram shows
vessels from ophthalmic artery branches supplying the AVM. The
ophthalmic artery branches normally supply the forehead.
Hemangiomas of Infancy
 Hemangiomas of infancy (HOI) is an umbrella term for all the
cutaneous hemangiomas that primary occur in infancy.
 They are masses of plump, rapidly dividing endothelial cells.
 They are often absent or small at birth and grow rapidly in
early infancy.
 In a large series, 60% of HOI occurred on the head and neck.
 The growth characteristics of HOI are often divided
into phases: nascent, proliferating, involuting, and
involuted.
Hemangioma of Infancy
There are numerous flow
voids within this
proliferating scalp mass in
a child.
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