eEdE-84-9486
J Starkey1, M Fujii1, J Kim2, T Moritani3, Y Numaguchi1
1 St.
Luke's International Hospital, Tokyo, Japan, 2Brigham & Women’s Hospital, Boston, MA, 3University of Iowa Hospitals and
Clinics, Iowa City, IA
Disclosures|None
The authors have no conflicts to disclose.
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Aims Scalp anatomy & trauma
Scalp injuries are common
Imaging features of infant
scalp injuries related to
birth trauma have been
well described but adult
traumatic scalp lesions
have not.
We aim to teach scalp
gross and imaging
anatomy and CT and MRI
imaging appearance of
various traumatic scalp
injuries.
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24 yo M following motor vehicle accident
Axial CT
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Outline Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
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Terms How to describe soft tissue injury
Contusion
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Hematoma
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Laceration
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Poorly defined
Well-defined
Soft-tissue defect
Blood products dispersed within
a soft tissue without
aggregation, likely due to
crushed arterioles and venules.
May have a similar appearance
to other soft tissue fluids (e.g.
edema) or other processes (e.g.
scarring, infiltrating infection or
malignancy, etc.).
A “body of blood”, in other
words a blood collection with
clear borders. May have a
similar appearance to other
fluid collections (e.g. infection,
injection sites, cysts, seromas,
etc.)
A soft tissue defect of the skin
and deeper scalp tissues.
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Outline Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
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CT scalp window Easily evaluate the scalp
Makes tissues of the
scalp discernable for
easy visualization of site
of impact, especially
when contusions/
hematomas are
mild/small.
W: 220
L: -20
Axial Bone Window
Axial Brain Window
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Axial Scalp Window
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Case 54 yo M with fall, rule out bleed
Axial Scalp Window
Axial Brain Window
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Axial Bone Window
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This skull fracture was missed initially. The scalp window makes the scalp contusion
easy to find compared to a standard brain window, allowing for careful search for an
underlying fracture. Even though a subtle fracture such as this does not generally
require treatment, the patient may complain of continuing headache and come back
for repeat imaging (e.g. to look for new bleeding), at which time the fracture would
be even less obvious.
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Outline Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
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Anatomy Scalp layers schematic
1. Epidermis/dermis
2. Subcutaneous layer
3. Galeal aponeurosis
4. Loose connective tissues
5. Periosteum
1
2
The loose connective tissue
layer (4, subgaleal/
subaponeurotic space) is
where most bleeding occurs
because the layers above it can
move freely on it and this layer
is where the arteries run, just
under the galea.
3
4
5
The thickness of the
loose connective tissues
layer depends on the
area of the skull. It is
often very thin. The
periosteum is uniformly
thin and highly adherent,
especially at sutures.
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Anatomy Scalp gross
1. Epidermis/dermis
2. Subcutaneous layer
3. Galeal aponeurosis
4. Loose connective tissues
1
5. Periosteum
2
3
4
0 cm
1 cm
5
5
This is an intraoperative
image of the
temporoparietal region.
The subgaleal
(subaponeurotic) plane is
relatively easy to dissect,
while the periosteum
requires a special tool to
remove.
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Anatomy Scalp layers on CT
1. Epidermis/dermis
1
2. Subcutaneous layer
2
3. Galeal aponeurosis
3
4. Loose connective tissues
4
5. Periosteum
5
The galeal aponeurosis
and loose connective
tissues are thin in many
areas. The periosteum is
non-visualized except
under rare circumstances
(e.g. calcification).
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Anatomy Scalp layers on MRI
1. Epidermis/dermis
2. Subcutaneous layer
3. Galeal aponeurosis
1
4. Loose connective tissues
2
5. Periosteum
3
4
5
Axial MRA. The resolution
and intensities of tissues
vary with the sequence, but
the fibrous galea and
periosteum are
hypointense. The
periosteum is not normally
visible unless lifted off the
bone (e.g. by blood).
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Cases Bumps
Case 1: 55 yo M, rule out injury
Axial T1
Axial T1
Fat sat
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Axial T2
Axial T2
Fat sat
Case 2: 38 yo M, fall
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Axial CT
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Axial CT
Zoomed
These subgaleal lipomas nicely
demonstrate the hypointense aponeurosis
on T1/T2 and hyperdense aponeurosis on
CT. Unlike subcutaneous lipomas which
move freely because of the underlying
loose connective tissues, lipomas in the
loose connective tissues layer are
immobile on physical exam. Though
trauma brought attention to them, these
lesions are incidental findings.
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Cases Classic pediatric
Case 1: 10 month old, fall
Axial CT
Axial T2
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Axial T1
Sagittal T2
Case 2: 17 month old, fall
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Axial T2
Coronal T2
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Axial T2
Coronal T2
Case 1: “Classic” subgaleal hematoma. In an infant, the subgaleal space can hold enough blood to cause shock and death. Most
cases are caused by birth trauma. Case 2: Subperiosteal hematoma. The galeal aponeurosis is lifted with a small subgaleal
collection. More centrally, the periosteum can be seen, with a hematoma underneath, caused by a skull facture.
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Case 78 yo F, fall
Axial Scalp Window
Axial FLAIR
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Axial MRA
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Parietooccipital subgaleal hematoma in typical configuration adjacent to the skull.
Note the hypointense aponeurosis visible on both FLAIR and MRA. On initial CT the
hematoma is limited to the right but spreads to the left side on subsequent MRI
obtained for other reasons.
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Outline Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
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Extent Loose connective tissues
Anterior-Posterior: The galeal aponeurosis is a thin fibrous
sheet that connects to the frontalis muscle anteriorly, which
continues to the periorbital region to contact the superior nasal
bridge and run beneath the orbitalis muscles. Therefore,
hematomas that occur in the loose connective tissues can extend
anteriorly and inferiorly to involve the periorbital and superior nasal
regions. This is why trauma remote from the orbits can still cause a
“black eye.” Posteriorly, the aponeurosis connects with the
occipitalis muscle.
Lateral: The aponeurosis connects with the temporalis muscle and
runs along the superficial temporal fascia, part of what surgeons term
the superficial muscular aponeurtic system (SMAS). Therefore,
hematomas which arise in the subgaleal space and extend laterally
and inferiorly will not enter into the temporal fat pads. They can
extend to the auricularis muscles at the more posterolateral spaces.
Images this slide courtesy of Visible Body
(www.visiblebody.com)
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Extent Anterolateral spaces coronal
3a
The aponeurosis (3a) combines anteriorly
and inferiorly to become the superficial
temporal fascia (3b).
3a
1
5a
2
1
5a
4a
4b
2
4a
Deep to the aponeurosis is the superficial
temporal fat pad (4a) and the deep temporal
fat pad (4b), covered by the superficial and
deep layers of the temporalis fascia. These
and the temporalis muscle (5a) fill the
temporal fossa. The gateway of the
superficial temporal artery scalp branches is
through the anterior superficial temporal fat
pad.
1. Epidermis/dermis
2. Subcutaneous layer
4b
3a/b. Galeal aponeurosis/superficial temp. fascia
4a/b. Superficial & deep temporal fat pads
5b
3b
5b
3b
5a/b. Temporalis/masseter muscles
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Extent Anterolateral spaces coronal
3a
When contusions or hematomas in the
subaponeurotic (subgaleal space) occur,
they will remain outside of the superficial
temporal fascia and temporal fat pads
(4a/4b). At the level of and inferior to the
zygoma, the aponeurosis becomes less
well defined and blood can extend deeper
into the subcutaneous tissues (3b).
3a
1
5a
2
1
5a
4a
4b
Potential space for subgaleal hematoma.
2
4a
1. Epidermis/dermis
2. Subcutaneous layer
4b
3a/b. Galeal aponeurosis/superficial temp. fascia
4a/b. Superficial & deep temporal fat pads
5b
3b
5b
3b
5a/b. Temporalis/masseter muscles
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Extent Anterolateral spaces axial
Patient 1
Axial CT
Patient 2
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Axial CT
Patient 3
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Axial T2
The same structures are readily apparent in 3 different patients on CT/T2. The
orbicularis oculi muscle is continuous with the superficial temporal fascia, a
continuation of the galeal aponeurosis. The superficial and deep temporalis fascia
define the superficial and deep temporal fat pads, respectively.
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Case 48 yo F, fall
Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
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Left frontal subgaleal hematoma. The superior portion of the superficial temporal
fat pad maintains normal density; note that in this location fat will be under the
hematoma, not because the hematoma is in the subcutaneous fat but because fat
from the temporal fossa is located deeper. Blood extending to the skin surface and
small air bubbles in the hematoma indicate a small laceration.
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Case 75 yo M, motor vehicle accident
Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
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Note that the bilateral subgaleal hematomas connect in the midline and extend
beneath the frontalis and orbicularis muscles. The superior portion of the superficial
temporal fat pad maintains normal density. A small laceration is present on the
right.
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Case 78 yo F, fall
Axial Scalp Window
Axial FLAIR
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Coronal FLAIR
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Left subgaleal hematoma extends to the left superior nasal area on initial CT. On
both the CT and an MRI performed several days later, the blood products are limited
to the space outside of the left superficial temporal fascia, with the underlying
superficial and deep temporal fat pads uninvolved.
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Case 29 yo M, fall
Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
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Different 29 yo on axis to compare.
Potential pitfall: some people, particularly young adult males, have large temporalis
muscles. These can mimic hematoma, especially if the head positioning is off axis,
making one side more prominent than the other. Note that the overlying
subcutaneous tissues are normal, however.
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Outline Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
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Blood supply ECA & ICA branches
Note that
arteries tend
to run at the
lower dermis
or just on
top of the
aponeurosis.
Both the
ECA and ICA
supply the
scalp.
Blood supply is derived mostly from the external carotid artery: superficial temporal artery, main branch passes
anterior to the tragus in the deep temporal fat bad. The occipital artery supplies the posterior scalp. The
anterior scalp is supplied partially by branches of the facial artery and partially by two small branches of the ICA’s
ophthalmic artery (supraorbital a., supratrochlear a.) that exit from the superior orbit. ICA and ECA vessels
anastomose freely.
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Case 74 yo M, fall
Axial Scalp Window
Axial MRA
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Axial MRA
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Left parietooccipital subaponeurotic hematoma on initial CT. MRA obtained
subsequently for other reasons revealed enlargement of the hematoma. A branch
of the left occipital artery can be clearly seen within the hematoma as the source of
bleeding. Note the clear depiction of the aponeurosis.
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Outline Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
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Case 23 yo F, fall
Axial Scalp Window
Axial Subdural Window
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Axial Subdural Window
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Right frontal subcutaneous glass. On further questioning, the patient had fallen
through glass. A small laceration with mild hemorrhage and high density foreign
body is present. Safety glass (i.e. leaded glass) is hyperattenuating. Wood or plain
glass are mildly hyperattenuating but can still often be identified.
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Case 79 yo M, fall
Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
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Cutaneous/subcutaneous benign calcifications. Perhaps a foreign body such as small
grains of dirt/sand could have a similar appearance, but the round shape and dermal
location are consistent with benign skin calcifications. Further, the subjacent soft
tissues have no signs of injury.
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Case 45 yo F, presenting with domestic abuse
Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
Axial Scalp Window
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Axial Scalp Window
Axial Bone Window
Cosmetic procedure changes. Images demonstrate high density along the frontal bone, an interior nasal bone implant, and
density in the area below the orbicularis muscles, consistent with forehead filler injections, cheek filler injections, and
rhinoplasty. The patient did not have radiological evidence of acute trauma.
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Case 24 yo M, grazed by train
Axial Scalp Window
Axial Scalp Window
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Coronal Scalp Window
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“Scalping” type injury. The patient has subgaleal blood and air with a large
laceration on the right running anterior to posterior with complete separation of the
aponeurosis from the skull superiorly and on the contralateral side.
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Summary Scalp anatomy & trauma
1
4
Scalp Window
Blood Supply
2
5
Layers
Cases
3
6
Terms
Extent
Use contusion, hematoma, and laceration
correctly.
Hematomas can spread anteriorly all the
way to the orbits and across the nasal
bridge, posteriorly to the occiput, and
laterally to the periauricular regions
W: 220, L: -20 for easy evaluation
The ECA supplies most of the scalp with
some ICA contribution anteriorly
Skin, subcutaneous tissues, aponeurosis,
loose connective tissues, periosteum
Trauma can be accompanied by foreign
bodies. Some non-traumatic entities can
mimic trauma.
Familiarity with scalp anatomy and various scalp injuries will help you
better understand and more accurately describe these common entities.
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Selected references Scalp anatomy & trauma
1.
af Geijerstam JL, Britton M. Mild head injury - mortality and complication rate: metaanalysis of findings in a systematic literature review. Acta Neurochir (Wien) 2003;145:843-850;
discussion 850
2.
Amaral L, Chiurciu M, Almeida JR, et al. MR imaging for evaluation of lesions of the
cranial vault: a pictorial essay. Arq Neuropsiquiatr 2003;61:521-532
3.
Bordignon KC, Arruda WO. CT scan findings in mild head trauma: a series of 2,000
patients. Arq Neuropsiquiatr 2002;60:204-210
4.
Davis DJ. Neonatal subgaleal hemorrhage: diagnosis and management. CMAJ
2001;164:1452-1453
5.
Ellis H, Mahadevan V. The surgical anatomy of the scalp. Surgery - Oxford
International Edition 2014;32:e1-e5
6.
Fabbri A, Servadei F, Marchesini G, et al. The changing face of mild head injury:
temporal trends and patterns in adolescents and adults from 1997 to 2008. Injury 2010;41:913917
7.
Le TH, Gean AD. Imaging of head trauma. Semin Roentgenol 2006;41:177-189
8.
Sinnatamby CS, Last RJ. Last's anatomy : regional and applied. Edinburgh ; New York:
Churchill Livingstone/Elsevier; 2011
Thank you!