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ECR 2019 / C-2186
Skull lesions in pediatrics: a mnemonic to remember them.
Congress: ECR 2019
Poster No.: C-2186
Type: Educational Exhibit
Keywords: Education and training, Dysplasias, Cancer, Education, MR, Digital radiography, CT, Paediatric, Neuroradiology brain, Bones
Authors: N. RUEDA RUIZ1, L. A. MORENO GOMEZ1, J. Echeverry muñoz1, M. R. ROYERO ARIAS2; 1BOGOTA, DI/CO, 2Medellin/CO
DOI:10.26044/ecr2019/C-2186

Findings and procedure details

We propose two mnemonics (Figure 2) to remember the most frequent pathologies according to the age of presentation as well as a schematic summary of the clinical, radiological and key findings by modality that allow the identification of the pathology between the differential diagnoses. We present a series of original cases from our pediatric reference center to describe the main findings of the lesions.

 

Fig. 2
References: Fundación SantaFe de Bogotá , Fundación SantaFe de Bogotá University Hospital - BOGOTA/CO

Figure 2. Mnemonics proposed for easy access to the most frequent pathologies of the skull, according to the age group, in pediatrics.

 

Wormian bones. (Figure 3).

  • Small bones often found within the sutures and fontanelles of the skull, especially near the lambdoid suture. They are a simple anatomical variant (General population prevalence varies from 8 to 15%).
  • With more than 10 wormian bones skeletal dysplasia should be suspected (cleidocranial dysostosis, pycnodysostosis, congenital hypothyroidism, rickets, imperfect osteogenesis) (Text`s reference 8)

 

Fig. 3
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 3. 5 years old boy with imperfect osteogenesis. 3D volume rendering reconstruction and lateral radiographs of the skull shows numerous wormian bones. AP radiographs of the leg evidence multiple dense lines in the distal femur and proximal tibia associated with dense metaphyseal bands along the cartilaginous plates related to biphosphonate therapy.

 

 

Epidermoid Cyst(Figure 4)

  • Slow-growing benign lesions secondary to congenital or posttraumatic epidermal or dermal inclusions within the diploe. 
  • On CT epidermoid cyst are seen as well-demarcated osteolytic lesions with sclerotic borders, homogeneously hypodense, which tend to expand into both the inner and outer tables. MR images show a fluidlike signal intensity on T1- and T2-weighted images and high signal intensity on DWI, without enhancement after gadolinium administration.

(Text`s reference 4)

 

Fig. 4
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 4. 1 year old boy. MRI sequences show small cyst 6 mm in diameter in relation to the outter table in the right occipital region, restricted diffusion in DWI.

 

DErmoid Cyst 

  • Their appearance on CT may be similar to epidermoid cysts, but calcifications and extension into the adjacent soft tissues are more frequent.
  • On MRI, they usually have heterogeneous appearance, sometimes with a fatty signal intensity on T11WI images and enhancement of a thick peripheral capsule after gadolinium administration. 

(Text`s reference 4)

 

Sinus Pericranii (Figure 5-6).

  • Is a transosseous venous vascular channel that connects the intracranial venous system with an epicranial or subgaleal vein, typically in the midline frontal region (40%). 
  • Congenital cases may have other associated congenital vascular anomalies such as cavernous hemangioma, venous angioma, aneurysmal malformation of the internal cerebral vein, and von Hippel-Lindau disease

(Text`s reference 6)

 

Fig. 5
References: Fundación SantaFe de Bogotá , Fundación SantaFe de Bogotá University Hospital - BOGOTA/CO

Figure 5. Tubular continuity solution of the parietal bone table, at the right parasagittal side through which venous vascular structure is observed, draining the superior longitudinal sinus and communicating with a small hyperdense subgaleal image adjacent.

 

Fig. 6
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 6. 7 years old boy. MRI T2 sequences evidence dilated extracranial frontal vein which communicates with the superior sagittal sinus by a transcalvarial emissary vein. Axial gradient echo shows low signal with blooming.

 

Meningocele/Cephaloceles (Figure 7).

  • Meningocele is a part of classification of cephaloceles only with meninges or cerebrospinal fluid. 
  • The role of imaging is to define the osseous defect, delineate the contents, map out the vascular structures within the cephalocele, and assess any coexisting intracranial anomalies. The brain parenchyma within a congenital cephalocele is often abnormal.

(Text reference 12)

 

Fig. 7
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 7. 11-year-old boy with daily headache. MRI T2 sequences shows a solution of continuity in the midline of the skull base in the sphenoidal and ethmoidal bones, of 20 mm diameter. Liquid content is observed through the defect. The content of the encephalocele partially occupies the posterior aspect of the nasal fossa and the nasopharynx. These findings are compatible with sphenoidal ethmoid meningoencephalocele.

 

Iatrogenic / Cephalohematoma:(Figure 8-9)

  • A subperiosteal hemorrhage that results from tearing of delicate vessels that traverse through the bone into the scalp. 
  • Are confined to suture borders where the periosteum is tightly adherent to the membranous tissue of the sutures. 
  • Is a benign condition, which usually does not require specific therapy. Most cephalohematomas resolve within a few weeks to months, depending on their size. Usually when the hematoma fails to resorb, progressive subpericranial osteogenesis results in a calcified cephalohematoma with incidence between 3% to 5% of all cephalohematomas.

(Text`s reference 7)

 

Fig. 8
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 8. Axial y sagital CT scan (bone window and soft tissue) and T1 sequence at MRI shows a calcified crescentic extra-cranial lesion adjacent to the outer table of the left parietal bone. 

 

Fig. 9
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 9. Patient with thickening of the skull secondary to chronic overdrainage in peritoneal ventricle derivation.

 

Leptomeningeal Cyst

  • Post-traumatic leptomeningeal cysts usually occur after head trauma during the first 3 years of life. It often arise in the cranial convexity, but sometimes occurring in the orbital roof and the posterior fossa. 
  • Dural laceration that accompanies the skull fracture is the mechanism of this complication. 
  • In radiography, the fracture zone that accompanies the soft-tissue thickness can be seen. CT and MRI are other modalities used in the diagnosis. 
  • CT scans are especially useful in detecting the bone fractures. 
  • MRI is useful for distinguishing leptomeningeal cysts from other pathologies. The leptomeningeal cysts are isointense to CSF on both T1-weighted and T2-weighted MRI. The associated pathologies, such as encephalomalacia, subdural fluid collection, hematomas, and ventricular dilatation, can also be seen on CT and MRI.

(Text`s reference 5)

 

Encephalocele.(Figure 10)

  • Intracranial tissue that herniates through a defect in the cranium results in an encephalocele. 
  • Are commonly found in occipital location (75% of cases) and they are usually associated to intracranial anomalies. 
  • CT may be used to display the bone anatomy, but the intracranial connection is best defined with MR imaging and the extention of cerebral tissue in an encephalocele. Occipital encephaloceles commonly involve the cerebellar or cerebral hemispheres even the dural venous sinuses.

(Text`s reference 11)

 

Fig. 10
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 10. Newborn with respiratory distress. Coronal y axial CT shows a nasoethmoidal defect in the midline with herniation towards the nasopharynx of apparent meningeal and encephalic tissue.

 

Intraosseous Hemangioma. (Figure 11)

  • The skull is their second most frequent localization after the spine, and frontal and parietal bones are the more often affected sites. 
  • On CT scans, they appear as expansive lesions with thin margins and intralesional spicules, radiating from uncommon center, with marked and homogenous enhancement after contrast administration. They generally erode the outer layer of the skull, with a relative sparing of the inner table.

(Text`s reference 2)

 

Fig. 11
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 11. Axial, coronal y sagital CT scan (bone window and soft tissue) shows “sunburst” pattern of spicules radiating within lytic lesion, large parietal skull hemangioma with minimal extension to adjacent soft tissues.

 

Osseous Venous Vascular Malformation. (Figure 12)

  • Osseous venous malformations are benign slow-growing vascular bone tumors that account for 2–10% of benign calvarial lesions and 0.2% of all bone neoplasms. 
  • CT shows a well-circumscribed intradiploic, osteolytic lesion, with mild expansion of the outer table and relative sparing of the inner table. A sunburst pattern of trabecular thickening radiating from a common centre is the classic finding. 
  • On MRI, the serpentine vascular channels can be identified and the appearance depends on the fat content and vascularity of the lesions. They are characteristically isointense to hyperintense on T1-weighted images and hyperintense on T2-weighted images with a “bunch of grapes”appearance. These bony lesions enhance diffusely after contrast administration. They can simulate a malignant neoplasm.

(Text reference 1)

 

Fig. 12
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 12. 2 years old boy. Lateral x-ray shows lithic lesion with periostic reaction in "sunburst" with diploe thickening. MRI sequences with heterogeneous signal mass with foci of restriction to diffusion and heterogeneous enhancement after contrast with involvement of the internal and external diploe in the frontoparietal midline. Extrinsic compression on the superior longitudinal sinus, without thrombosis. It has vascular structures with a signal gap inside and thickening of the adjacent pachymeninge. Angiographic sequences of digital subtraction with multiple vascular structures inside the mass compatible with vascular malformation.

 

Osteoma

  • This juxtacortical lesion develops from the outer table, mainly of the frontal or parietal bone, and is either sessile or pedunculated. The lesion is usually solitary. The presence of multiple osteomas of the skull should prompt the search for Gardner syndrome. 
  • Radiography and CT show a small, well-defined round or oval lesion that is usually dense and homogeneous. The lesion spares the sutures but may extend into the ethmoid and frontal sinuses. It usually has a homogeneous low signal intensity on T1WI; its appearance on T2WI is variable, depending on the content of cortical and trabecular bone. Osteoma does not enhance after gadolinium administration. (Text`s reference 4)

 

Langerhans Histiocytosis(Figure 13)

  • Is a multisystemic disorder characterized by the abnormal proliferation of Langerhans cells in various tissues. This rare disease is most common in children, particularly those between 6 and 10 years old. The bones represent the most frequent site of involvement (75–80%). 
  • Multiple lesions may expand and coalesce, producing the appearance of a geographic map. 
  • CT frequently shows unequal involvement of the inner and outer tables. The center of the lesion may contain a sequestrum, which in fact represents residual intact bone.

(Text`s reference 4)

 

 

Fig. 13
References: Hospital Universitario San Vicente de Paul, Medellin, Colombia

Figure 13. 14 years old boy with headache. Axial, coronal and sagittal CT with 3D volume rendering reconstruction shows a well-defined lytic lesion with non-sclerotic borders and bevelled edges, located in the right parietal bone.

 

 

Fibrous Dysplasia(Figure 14).

  • This monostotic (70–80% of cases) or polyostotic disorder is discovered predominantly in children and young adults.
  • At the skull fibrous dysplasia is typically expanded, with focal cystic enlargement of the outer table. CT is the imaging modality for the diagnosis because it can show the characteristic ground-glass matrix appearance (70–130 HU) in all or part of the lesion. (Text`s reference 4)

 

Fig. 14
References: Fundación Hospital Pediátrico de la Misericordia. Bogotá, Colombia.

Figure 14. Axial, sagital and coronal CT bone window shows “ground-glass” appearance with expansion confined to the outer table of left frontal and sphenoidal bone.

 

Giant Cell Tumor

  • Benign bone tumor. 2% of all giant cell tumors occur in the head and neck and they predominantly affect the mandible. 
  • At imaging, central giant cell granuloma appears as a well-circumscribed soft-tissue mass, with bone remodeling and erosion, it enhances diffusely at contrast-enhanced CT. On T2WI it have a markedly hypointense signal in the presence of hemorrhage and/or hemosiderin. 

(Text`s reference 3)

 

Aneurismal Bone Cyst

  • This benign expanded bone tumor rarely affects the skull (1–6% of cases). 
  • It appears as a sharply defined expanded osteolytic lesion with thin sclerotic borders, although the tables appear disrupted when expansion is significant. This multilobulated lesion contains blood, which explains the frequent presence of fluid- fluid levels.

(Text`s reference 4)

 

 

MeTastasis And Tumors(Figures 15, 16, 17 and 18).

  • Metastases are uncommon malignant bone tumors in children. 
  • The most common calvarial metastases are from neuroblastoma.
  • Metastases may have an osteolytic, sclerotic or mixed pattern depending on the primary tumor. Metastases usually present as multiple osteolytic lesions with a soft-tissue component extending into adjacent tissues. 
  • On Magnetic resonance metastatic lesions are usually hypointense to isointense on T1-weighted images and enhance after contrast administration. The pattern of enhancement is variable and may be homogeneous, heterogeneous, peripheral ring or may lack enhancement according to primary mass.

(Text`s reference 1)

 

 

And finally, to complement the diagnostic approach, remember the location and appearance of computed tomography densities of the most frequent lesions in the pediatric skull (Figure 19)

 

 

Fig. 19
References: Fundación SantaFe de Bogotá , Fundación SantaFe de Bogotá University Hospital - BOGOTA/CO

Figure 19. Diagram of differential diagnoses according to the location and appearance of skull injuries in pediatrics.

 

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