some anatomical variations may be mistaken for pathologies,
some of which include enlarged parietal foramina and other like cranium foramina; wormian bones; arachnoide ganulation; transcalvarial venous channel; diffuse thickening of the skull; hyperaration of the skull bones. Fig. 2 Fig. 3
Congenital changes in size and shape of the skull
It is a condition in which one or more of the fibrous sutures prematurely fuses by ossification,
resulting in an abnormal head shape and sometimes abnormal facial features.
CT with three-dimensional (3D) image reformations is the best modality used for evaluation of sutures. Fig. 4 Fig. 5
Microcephaly Fig. 6
Achondroplasia is a congenital disorder that affects the endochondral ossification and is the most common cause of short-limb dwarfism.
It has numerous distinctive radiographic features and in the skull we can find relatively large cranial vault with small skull base; forehead with the depressed nasal bridge and narrowed foramen magnum. Fig. 6
Macrocephaly Fig. 6
Congenital scalp mass
Encephaloceles are characterized by a protrusion of cerebral and/or meningeal tissue through a congenital defect of the skull and dura,
usually located at or near the midline with an associated palpable mass.
They are more common in occipital location (75% of cases).
The CT is useful to evaluate the size and boundaries of the osseous defect and MRI is the best imaging modality to evaluate the contents within the encephalocele. Fig. 7
They are abortive rudimentary cephaloceles,
benign malformative lesions consisting of meningeal and vestigial tissues ,often midline and covered by skin.
MRI is the gold standard for delineating the contents and venous angiography MRI may show an incidental persisting primitive falcine vein,
as well as other anomalies of the venous sinuses. Fig. 8
Sinus pericranii consists of an abnormal communication between the intracranial and extracranial venous drainages,
via a small ostium.
Contrast-enhanced CT shows an enhancing epicranial mass composed of serpiginous vessels and is the most suitable mean of assessing the anomalous venous anatomy.
MR can be used to delineate the abnormal anatomy. Fig. 8
Plexiform neurofibroma is an uncommon variant of neurofibroma and it is pathognomonic for neurofibromatosis type 1.
plexiform neurofibromas develop in the orbit.
CT is non-specific.
MRI shows T1 low signal; T2 hyperintense +/- hypointense central focus (target sign).
The enhancement is variable,
although at least a portion of the tumor usually enhances. Fig. 9
Congenital skull bone failures
Aplasia cutis congenita
Aplasia cutis congenita is a rare disorder characterized by focal absence of the skin.
The scalp defect is associated with a defect in the underlying bone and dura mater,
with exposure of the brain and sagittal sinus. Fig. 10
Cleidocranial dysplasia is a skeletal dysplasia characterized by persistent fontanelles and aplasia/hypoplasia of the clavicles,
with a wide phenotypic variability. Fig. 10
Amniotic band syndrome
Amniotic band syndrome comprises of a wide spectrum of abnormalities,
all of which result from entrapment of various fetal body parts in a disrupted amnion.
In head and face,
it can lead to acrania,
anencephaly; facial clefts and nasal deformities. Fig. 10
Caput succedaneum Fig. 11
Subgaleal haematoma Fig. 11
Cephalohematoma Fig. 11
Subcutaneous emphysema; linear fracture and comminuted fracture Fig. 12
Ping Pong Fractute
Refers to a depressed skull fracture caused by inner buckling of the calvarium.
It is seen in newborns and children because of the soft and resilient nature of their bones and the fracture line is not visualised radiologically. Fig. 12
Also known as a leptomeningeal cyst is a late posttraumatic complication of skull fractures and it consists in herniation of cerebralspinal fluid or brain parenchyma into the subcutaneous tissue,
and subsequent widening of the fracture.
It´s seen on CT as a widening fracture in subsequent studies and the MRI can identify the bone defect and its contents. Fig. 13
Periorbital cellulitis Fig. 14
Cysticercosis is a parasitic infection caused by the larval stages of the pork tapeworm, Taenia solium.
The subcutaneous form of the disease is a relatively rare clinical entity.
CT images can demonstrate a cyst with a tiny calcification foci.
cysticercosis is seen as a cystic lesion that appears hyperintense on T2-weighted image and hypointense on T1-weighted image.
The scolex is also acknowledged as a tiny hypointense speck within the hyperintense cyst. Fig. 14
The MRI signal intensity is highly variable and depends on the proportions of water,
mucus and protein.
This entity is characterized by a well-defined lytic lesion without marginal sclerosis,
invading the inner and outer tables,
sometimes with a central residual bone density within it,
known as “buttom sequestrum” which in fact represents residual intact bone.
Its MRI signal intensity is equivalent to that of skeletal muscle,
which is T1 low-intermediate signal,
T2 high signal,
and demonstrate marked contrast enhancement. Fig. 16
Hyperostosis frontalis interna
it is characterized by benign overgrowth of the inner table of the skull bone,
most commonly affecting the frontal bone. Fig. 17
It is a genetic mutation that results in an abnormal differentiation and maturation of the osteoblasts,
with progressive replacement of normal bone by immature bone.
CT is the imaging modality of choice for the diagnosis because it can show the characteristic ground-glass matrix appearance (70–130 HU) in all or part of the lesion.
Intralesional calcifications may be present. Fig. 17
It is a chronic bone disorder characterised by excessive abnormal bone remodeling.
The characteristic appearance of paget disease includes homogeneous enlargement of the skull vault and thickening of the tables and of the trabecular bone,
leading to a loss of differentiation between these structures.
These manifestations are better characterized by CT. Fig. 17
Cirsoid aneurysms are rare arterio-venous fistulas of the scalp.
They can be congenital or posttraumatic.
In most cases,
the superficial temporal artery is the main supply to the fistula.
Angiography is the investigation of choice. Fig. 18
Skull bone infarction
A skull bone infarction can be an uncommon complication of the sickle
as typically these are located in the long bones and
rarely in the skull.
The MRI is the imaging modality of choice for the
diagnosis although the findings are similar to those found in
osteomyelitis and include bone marrow edema,
abdnormal enhancement of adjacent soft tissues. Fig. 19
Lipomas are benign tumours composed of mature adipocytes. On CT,
they appear like round or ovoid,
homogeneous mass with fat attenuation (-50 to -100 HU),
typical subgaleal and more rarely intraosseous.
MR demonstrates the drop out intensity on fat-supressed
Scalp tumor of vascular origin.
MR imaging findings in hemangioma are frequently diagnostic.
On T2-weighted images,
hemangiomas generally appear as multiple high-signal-intensity and internal reticular low-signal-intensity areas may be present,
representing fast flow within vessels,
or foci of calcification.
On T1-weighted MR images,
the signal intensity of these lesions is usually intermediate. Fig. 21
Cyst with keratin content lined by walls of stratified squamous epithelium resembling the external root sheath of hair follicle.
Findings suggestive of the diagnosis are round or ovoid,
soft tissue mass with calcifications that does not involve the underlying bone.
It appears isointense to brain on T1; inhomogeneously hypointense on T2 and with internal “blooming” on T2* that suggests calcifications. Fig. 22
Epidermoid and Dermoid cysts
Epidermoid cysts frequently occur laterally in the parietal or frontal bone On CT,
they are seen as well-demarcated osteolytic lesions with sclerotic borders.
MR images show a fluidlike signal intensity on T1- and T2-weighted images and high signal intensity on DWI.
They usually do not enhance after gadolinium administration.
Dermoid cysts frequently involve the midline,
particularly near the anterior fontanelle.
Their appearance on CT may be similar to that of epidermoid cysts.
they usually have a more heterogeneous appearance with a fatty signal intensity on T1-weighted images and enhancement of a thick peripheral capsule after gadolinium administration. Fig. 23 Fig. 24
Basal cell carcinoma and squamous cell carcinoma
They are hardly distinguishable from images.
Findings suggestive of diagnosis are ulcerated,
infiltrating and irregular enhancing soft- tissue mass that may cause bone erosion or permeative appearance of bone.
Gorlin-Goltz syndrome is a rare phakomatosis characterized by multiple odontogenic keratocysts,
basal cell carcinoma,
falx cerebri calcifications,
among others. Fig. 25 Fig. 26
Skull bone tumors
Osteoma is a mature bone tumor. The presence of multiple osteomas on the skull should prompt the search for Gardner syndrome.
CT images show a small,
well-defined round or oval lesion that is usually dense and homogeneous. Fig. 27
This is a benign slow-growing vascular bone tumor.
CT typically shows a well-defined lucent lesion with sclerotic margins and a reticulated internal structure radiating from the center to the periphery described as “sunburst” or “spoke-wheel” pattern.
It erodes the outer table and spares the inner table.
It enhances homogeneously after contrast injection.
MRI better depicts the extension of the lesion and its relationship to the adjacent neurovascular structures.
Hemangiomas are heterogeneously hyperintense on T2 and hyperintense on T1 and enhances initially focal,
and then diffuse,
after contrast media administration. Fig. 28
It is a rare subtype of meningioma.
CT usually shows an osteosclerotic lesion,
which is frequently associated with destructive,
and spiculated borders,
suggestive of the diagnosis.
the lesion has low signal intensity on T1-weighted images and it has variable signal intensity on T2-weighted images.
Moderate homogeneous enhancement is usually evident after contrast media injection. Fig. 29
Secondary lymphoma is much more common than primary lymphoma,
although both are relatively rare.
Radioimaging is not definitively diagnostic because the appearance can mimic that of metastatic carcinoma,
tissue diagnosis is mandatory for proper diagnosis and management.
In our case,
we demonstrate a lymphoma in the left zygomatic process that appears as a lytic non infiltrative lesion wich is hypointense on T2,
has a hypersignal on DWI and enhances after gadolinium administration. Fig. 30
Myeloma is a malignant disease of the bone marrow characterized by a monoclonal proliferation of plasma cells. CT images shows multiple small,
roundish osteolytic lesions that are relatively uniform in size,
with sharp and nonsclerotic margins,
the classic “punched-out” lesions.
the lesion is hypointense on T1 and hyperintense on T2 and enhancing after contrast medium administration. Fig. 31
Chordoma is an uncommon malignant tumour that originates from embryonic remnants of the primitive notochord.
The clival region is the second most common location.
Typically the mass projects posteriorly at midline,
indenting the pons.
CT evaluation is usefull to assess the degree of bone involvement and shows well-circumscribed destructive lytic lesion centrally located in clivus,
within intratumoral calcifications. MRI provides anatomical delineation of adjacent structures and appears as T1 intermediate to low intensity; T2 very high signal,
SWI/GE variable intralesional hemorrhage and heterogenous enhancement with a honeycomb appearance corresponding to low T1 signal areas within the tumor after contrast media administration. Fig. 32
Metastases represent the most frequent cause of multiple skull lesions.They are usually secondary to breast,
and thyroid cancers in adults and to neuroblastoma or sarcomas in children. The imaging pattern is not specific and most commonly appears as an aggressive osteolytic lesion which enhances homogeneously after contrast administration,
but heterogeneous enhancement,
peripheral ring enhancement,
or lack of enhancement (sclerotic lesions) can be observed.
Miscellaneous Fig. 34
Cutis verticis gyrata
Masticatory muscle hypertrophy
Copper beaten skull
Other findings Fig. 35
Front silicone implants
External occipital protuberance
Metal fragments of firearm
Metal plastic surgery clips