DOI: 10.1148/rg.246045034
RadioGraphics 2004;24:1655-1674
© RSNA, 2004
Lumps and Bumps on the Head in Children: Use of CT and MR Imaging in Solving the Clinical Diagnostic Dilemma1
Fanny E. Morón, MD,
Michael C. Morriss, MD,
Jeremy J. Jones, MD and
Jill V. Hunter, MD
1 From the E. B. Singleton Department of Diagnostic Imaging, The Texas Children’s Hospital, Baylor College of Medicine, MC2–2521, 6621 Fannin St, Houston, TX 77030. Recipient of a Certificate of Merit award for an education exhibit at the 2003 RSNA scientific assembly. Received March 12, 2004; revision requested April 5 and received June 14; accepted June 16. All authors have no financial relationships to disclose. Address correspondence to M.C.M. (e-mail: mcmorri1@texaschildrenshospital.org).
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Abstract
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Lumps and bumps of the scalp are a common presenting complaint in children and often pose a diagnostic dilemma. These lesions can be difficult to image, with evaluation confounded by their small size. However, accuracy in diagnosis is critical because the diagnostic and therapeutic implications can vary significantly. The clinical examination can be helpful in developing the differential diagnosis and the imaging strategy. Often, however, a single imaging study is insufficient, and the radiologist finds it necessary to image with more than one modality to correctly diagnose a lesion and provide adequate information for the surgeon. Radiography and ultrasonography are often the initial screening diagnostic tests, followed by magnetic resonance (MR) imaging or computed tomography (CT) for more detail. Multidetector thin-section CT and thin-section MR imaging with surface coils are beneficial in the work-up of these small lesions of the head and neck. The use of newer MR imaging sequences such as heavily T2-weighted single-shot turbo spin-echo imaging and diffusion-weighted imaging can improve the characterization of difficult lesions. Familiarity with the variety of new imaging tools and techniques that are available can help characterize pediatric head and neck lesions and guide clinical management.
© RSNA, 2004
Index Terms: Brain neoplasms • Brain, hernia, 10.1461 • Face • Head, CT, 10.1211, 20.1211 • Head, MR, 10.1214, 20.1214 • Head and neck neoplasms, 10.3141, 10.3622, 20.362, 20.366 • Head and neck neoplasms, diagnosis
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LEARNING OBJECTIVES FOR TEST 4
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After reading this article and taking the test, the reader will be able to:
- Describe the differential diagnosis for palpable lumps and bumps on the pediatric head.
- Discuss the importance of complete and appropriate imaging for preoperative assessment of these lumps and bumps.
- Develop an imaging strategy for diagnosing these lesions.
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Introduction
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Lumps and bumps on the head are a common complaint in children and often a source of concern for parents. The differential diagnosis for the examining physician is broad, and radiologic evaluation is often requested (1,2). A wide spectrum of congenital lesions (eg, encephaloceles, nasal gliomas, dermoid and epidermoid cysts, benign tumors) and acquired lesions (eg, sarcoma, Langerhans cell histiocytosis [LCH], metastatic neuroblastoma, infectious or traumatic lesions) are commonly encountered. Current imaging modalities such as thin-section computed tomography (CT), surface coil magnetic resonance (MR) imaging, and MR angiography can be helpful in characterizing these lesions.
In this article, we review the neuroimaging techniques used in evaluating head and neck lesions in children. We also discuss and illustrate the benefits of using various imaging modalities to characterize these congenital and acquired lesions.
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Imaging Techniques
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Neuroimaging techniques in the pediatric head and neck run the gamut from radiography to ultrasonography (US) to CT and MR imaging. Radiography and US have been the mainstays of imaging in the evaluation of masses of the pediatric head and neck. The bone margins and location of lesions such as LCH are well seen at radiography of the skull and strongly suggest the diagnosis. US is a fast and relatively inexpensive modality for evaluating masses of the head and neck and has been particularly useful in evaluating cystic or vascular masses. However, the masses discussed and illustrated in this article are complex, and many have important connections to the central nervous system (CNS) that can be seen only with cross-sectional imaging modalities such as CT or MR imaging. CT and MR imaging provide greater anatomic detail, which is critical for surgical planning and, with respect to malignant lesions, is important in therapeutic planning and prognosis. In addition, CT and MR imaging often provide more detailed information about the vascular anatomy.
The imaging of a lesion in the pediatric head begins with a reasoned consideration of the differential diagnosis. After initial clinical evaluation, the first decision is whether to use CT or MR imaging. Children with lesions on the head are often sent from the primary care provider’s office for head CT to evaluate the "bump in the skin." An examination by the radiologist is often necessary to localize the lesion and develop a differential diagnosis. If the lesion is the type that may have a small intracranial connection (eg, dermoid cyst), MR imaging is generally the modality of choice. Many times, the exact nature of the lesion is not known, in which case CT becomes the initial screening modality. In such cases, thin-section CT through the lesion with and without the intravenous administration of contrast material is performed. If the lesion is small, thin-section CT (0.625–1.25-mm sections) through the lesion may be performed after the lesion has been localized with thicker-section CT. Depending on the location of the lesion, coronal or sagittal reformatted images may then be obtained to display the lesion and its anatomic relationships with adjacent structures. Such thin-section imaging has become routine with the rapid scanning and reformation capabilities of the latest generation of multisection scanners. In cases in which a lesion is known (eg, nasofrontal dermoid cyst), 0.625-mm images may be used to examine for a tiny bone defect in the nasofrontal region that indicates an intracranial connection. In cases of lytic lesions seen in LCH or frankly destructive malignant lesions such as neuroblastoma, CT may be useful as the primary modality in defining the areas of bone destruction and tumor spread. In cases in which the lesions are large, CT sections are typically 2.5–5 mm in thickness. CT is often used in addition to radiography by oncologists to track bone healing in LCH.
MR imaging is also a powerful imaging tool for diagnosing lumps and bumps on the pediatric head. It offers excellent soft-tissue contrast and the advantages of multiplanar imaging. In addition, advanced techniques such as MR angiography and MR venography display the arterial and venous anatomy. Some of the lesions described in this article may cross fascial planes and invade important structures such as the skull base, and these findings are best seen with MR imaging. The use of surface coils also enhances the usefulness of MR imaging in evaluating the intracranial connections of small lesions such as dermoid cysts and atretic encephaloceles. Some of these lesions are just a few millimeters in size and have tiny connecting tracts to the CNS that can be seen only at thin-section MR imaging performed with optimum soft-tissue contrast techniques. These lesions often have fluid-signal-intensity tracts that can be seen at heavily T2-weighted MR imaging. We often use a "dermoid" protocol for thin-section imaging of tiny lesions (eg, nasal dermoid cysts) that may have sinus tracts. In these cases, we place small, flexible phased-array surface coils over the area of interest to provide optimal anatomic detail. These coils come in a variety of sizes and are available from multiple vendors. With small children, it is necessary to use small coils that fit easily over the face and inside the head coil. We generally combine routine sagittal T1-weighted and axial T2-weighted MR imaging of the head and neck with thin-section surface coil imaging. We use a surface coil with 2-mm-thick sections to obtain images in the two or more orthogonal planes that best demonstrate the lesion. For nasal dermoid cysts, we have found the axial and sagittal planes to be optimal, whereas for nasal gliomas or anterior encephaloceles all three planes (axial, sagittal, coronal) may be useful. Small occipital lesions are also usually best seen on axial and sagittal images. Routine unenhanced and contrast material–enhanced T1-weighted MR imaging and heavily T2-weighted imaging are standard in the evaluation of nasal dermoid cysts, gliomas, and encephaloceles as well as atretic encephaloceles. Use of fat saturation is helpful for contrast-enhanced imaging. Short inversion time inversion-recovery T2-weighted MR imaging is also often used to display the margins of cystic lesions such as venolymphatic malformations in the neck. Standard MR venographic and MR angiographic sequences are used when a lesion is near a dural venous sinus or is suspected of having an abnormal arterial supply. These sequences are often performed with a surface coil to optimize visualization of the target lesion. In any case that involves the CNS, imaging routinely also includes T2-weighted and contrast-enhanced T1-weighted imaging through the entire brain with a head coil.
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Congenital Lesions
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Congenital midline masses include encephaloceles, nasal gliomas, and dermoid and epidermoid cysts. These lesions occur in the nasofrontal region, the occiput, or the cranial vertex. Transsphenoidal encephaloceles occur at the skull base and are not visible at clinical examination but may be seen as nasopharyngeal masses and are part of the spectrum of encephaloceles seen in children.
Embryologic Features
Encephaloceles have a complex embryology that in some cases is not clearly defined. Nasal gliomas, nasofrontal encephaloceles, and dermoid and epidermoid cysts are believed to have a similar embryology, and the embryology of these lesions is probably the best understood (3). The first 12 weeks of fetal development are important in the formation of the face. In the 3rd and 4th gestational weeks, the neural fold develops and forms the neural tube. As the neural tube forms, neural crest cells migrate laterally and anteriorly around the eye to the frontonasal process. The neural crest cells in the frontonasal region primarily form centers of mesenchymal cells, which will become the bone, cartilage, and muscles of the face. The mesenchymal structures of the skull base are formed from these centers, which eventually fuse and ossify. Spaces are formed between these centers prior to fusion and are important in the development of congenital nasal masses. The space between the frontal and nasal bones is known as the fonticulus frontalis. Abnormal closure of this space is believed to lead in some cases to an ectopic rest of extracranial glial tissue, which will become a nasal glioma. If there is frank herniation of intracranial tissue containing meninges and a subarachnoid connection, an encephalocele is formed. The space between the nasal bones and the precursor structures of the septum and nasal cartilages is called the prenasal space. It is believed that during development, the dura mater projects through the fonticulus frontalis or more inferiorly into the prenasal space. This dural element normally regresses, but if it persists, it may remain in contact with the epidermis and trap ectodermal elements, leading to dermoid cyst formation.
Encephaloceles have more diverse and less well understood embryologic features. Occipital encephaloceles are generally believed to be related to either abnormal neural tube closure occurring by the 6th week, or perhaps to a localized "blowout" of cerebral tissue occurring later at around 8–12 weeks gestation (4). In contrast, it has been theorized that transsphenoidal encephaloceles (discussed later) are related to the formation of the skull base and the migration of cephalic neural crest cells (5).
Encephaloceles
Intracranial tissue that herniates through a defect in the cranium results in an encephalocele (Fig 1) (6–8). Such lesions are called meningoceles when they contain only meninges and meningoencephaloceles if brain tissue is included in the herniated tissue. They occur in one of every 4,000 live births and are most commonly occipital in location (75% of cases) (Fig 2); lesions are frontoethmoidal in 15% of cases and basal in 10% (7). There are often significant associated intracranial anomalies (9,10). Occipital encephaloceles may be associated with Chiari or Dandy-Walker malformations and callosal or migrational anomalies (11). Frontoethmoidal lesions are not typically associated with these types of anomalies. Frontoethmoidal encephaloceles are also known as sincipital encephaloceles and are subdivided into nasofrontal, nasoethmoidal (Fig 3), and naso-orbital types. These encephaloceles are more common in South and Southeast Asian populations (12). They are found projecting along the nasal bridge between the nasofrontal sutures into the glabella (nasofrontal region), under the nasal bones and above the nasal septum (nasoethmoidal region) (Fig 3), or along the medial orbit at the level of the frontal process of the maxilla and the ethmoid-lacrimal bone junction (naso-orbital region) (Fig 4) (7,8,12). Frontoethmoidal encephaloceles manifest as a clinically visible mass along the nose. The intracranial root of most frontoethmoidal encephaloceles lies at the foramen cecum, a small ostium located at the bottom of a small depression anterior to the crista galli and formed by the closure of the frontal and ethmoid bones (7,8).
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Figure 1. Drawings illustrate aberrant development of the nasofrontal region leading to the formation of various midface masses. Schematic A shows that frontonasal encephaloceles form when the fonticulus nasofrontalis remains patent. Schematic B shows that nasal gliomas form when the dural diverticulum involutes late or only proximally through the foramen cecum, leaving sequestered neurogenic tissue that may be connected to the intracranial content by a fibrous stalk. As shown in schematic C, dermal sinuses result from a lack of involution of the dural diverticulum through the foramen cecum. Dermoid or epidermoid cysts may form along the dermal sinus tract due to desquamation of tissue lining the tract. (Reprinted, with permission, from reference 6.)
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Figure 2a. Occipital meningoencephalocele. Sagittal T1-weighted (a) and axial T2-weighted (b) MR images and MR venogram (c) show an occipital meningoencephalocele with no evidence of involvement of venous structures. The lesion consists predominantly of herniated meninges, but a small amount of brain tissue was found at surgery.
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Figure 2b. Occipital meningoencephalocele. Sagittal T1-weighted (a) and axial T2-weighted (b) MR images and MR venogram (c) show an occipital meningoencephalocele with no evidence of involvement of venous structures. The lesion consists predominantly of herniated meninges, but a small amount of brain tissue was found at surgery.
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Figure 2c. Occipital meningoencephalocele. Sagittal T1-weighted (a) and axial T2-weighted (b) MR images and MR venogram (c) show an occipital meningoencephalocele with no evidence of involvement of venous structures. The lesion consists predominantly of herniated meninges, but a small amount of brain tissue was found at surgery.
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Figure 3. Nasoethmoidal encephalocele. Midline sagittal reformatted image from CT data demonstrates a nasoethmoidal encephalocele (arrow). Frontal lobe tissue and the meninges extend under the nasal bones and above the septal cartilage.
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Figure 4a. Naso-orbital frontoethmoidal encephalocele in a 2-year-old patient. (a) Three-dimensional shaded-surface-display image from CT data shows a large, left-sided fronto-orbital mass. (b) Axial CT scan shows a left frontal lobe encephalocele that extends through the ethmoid bone into the orbit. (c) Axial T2-weighted MR image obtained at the same level as b helps confirm the presence of a frontal lobe encephalocele. The contents of the orbital vault were formed normally.
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Figure 4b. Naso-orbital frontoethmoidal encephalocele in a 2-year-old patient. (a) Three-dimensional shaded-surface-display image from CT data shows a large, left-sided fronto-orbital mass. (b) Axial CT scan shows a left frontal lobe encephalocele that extends through the ethmoid bone into the orbit. (c) Axial T2-weighted MR image obtained at the same level as b helps confirm the presence of a frontal lobe encephalocele. The contents of the orbital vault were formed normally.
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Figure 4c. Naso-orbital frontoethmoidal encephalocele in a 2-year-old patient. (a) Three-dimensional shaded-surface-display image from CT data shows a large, left-sided fronto-orbital mass. (b) Axial CT scan shows a left frontal lobe encephalocele that extends through the ethmoid bone into the orbit. (c) Axial T2-weighted MR image obtained at the same level as b helps confirm the presence of a frontal lobe encephalocele. The contents of the orbital vault were formed normally.
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Basal encephaloceles are internal and are not generally externally visible, although they may manifest as a lump or bump in the oropharynx or nasopharynx. Basal encephaloceles include transethmoidal, sphenoethmoidal, transsphenoidal, and frontosphenoidal varieties. Transsphenoidal and transethmoidal encephaloceles are the most common varieties, although they themselves are very rare (Fig 5) (8,13,14). The former project through a defect in the floor of the sella and into the nasal cavity, whereas the latter project through a midline or cribriform plate defect into the nasal cavity. Transsphenoidal encephaloceles may be associated with a cleft palate and may also project into the oral cavity. A transsphenoidal encephalocele splays the sphenoid bone, displacing the cavernous sinus laterally, and is positioned anterior to the dorsum sella (8,13,14). Important structures such as the pituitary gland, hypothalamus, optic nerves and chiasm, and anterior third ventricle are typically involved in transsphenoidal encephaloceles (8,13,14). Affected children may present with nasal obstruction.
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Figure 5. Transsphenoidal encephalocele. Coronal T2-weighted MR image shows a transsphenoidal encephalocele anterior to the dorsum sella that projects into the nasopharynx and causes downward displacement of the optic apparatus, hypothalamus, and anterior recess of the third ventricle.
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Surgery is the treatment used for encephaloceles, and MR imaging is the best imaging modality for defining the contents of an encephalocele prior to surgery. High-resolution CT may also be used to display the bone anatomy, but the intracranial connection is best defined with MR imaging. The extent of cerebral tissue in an encephalocele is also better defined with MR imaging, which aids in prognosis and surgical planning. Occipital encephaloceles commonly involve the cerebellar or cerebral hemispheres and may involve the dural venous sinuses. MR imaging with MR venography is used to demonstrate brain tissue and venous involvement in these lesions. MR imaging is very useful in differentiating a frontoethmoidal encephalocele from a nasal glioma or nasal dermoid cyst. MR imaging also best depicts associated intracranial anomalies. In basal encephaloceles, involvement of the pituitary gland, hypothalamus, optic nerves and chiasm, and third ventricle is best defined with MR imaging.
Atretic encephaloceles should be mentioned because they are included in the differential diagnosis of skin-covered midline scalp masses in childhood. They are typically parietal in location and contain meninges and neural rests (15). A vertically positioned straight sinus is commonly associated with these malformations, and anomalies of the tentorial incisura and superior sagittal sinus have also been reported (Fig 6) (15,16). These malformations are also seen occasionally in the occipital region (Fig 7). Atretic encephaloceles contain a fibrous stalk at their base that connects to the dura mater. Association with intracranial anomalies is variable, and some children may have normal clinical outcomes with no associated intracranial anomalies (15).
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Figure 6a. Vertically positioned straight sinus with persistent fetal anatomy. Sagittal T2-weighted MR image (a) and sagittal (b) and coronal (c) MR venograms demonstrate a vertically positioned straight sinus (black arrow in a, arrow in b) and a fenestrated superior sagittal sinus (arrowheads in c) resulting from deflection around the tract of a histologically proved atretic parietal encephalocele (white arrows in a).
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Figure 6b. Vertically positioned straight sinus with persistent fetal anatomy. Sagittal T2-weighted MR image (a) and sagittal (b) and coronal (c) MR venograms demonstrate a vertically positioned straight sinus (black arrow in a, arrow in b) and a fenestrated superior sagittal sinus (arrowheads in c) resulting from deflection around the tract of a histologically proved atretic parietal encephalocele (white arrows in a).
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Figure 6c. Vertically positioned straight sinus with persistent fetal anatomy. Sagittal T2-weighted MR image (a) and sagittal (b) and coronal (c) MR venograms demonstrate a vertically positioned straight sinus (black arrow in a, arrow in b) and a fenestrated superior sagittal sinus (arrowheads in c) resulting from deflection around the tract of a histologically proved atretic parietal encephalocele (white arrows in a).
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Figure 7a. Atretic meningocele. Axial T2-weighted (a) and contrast-enhanced T1-weighted (b) surface coil MR images show a bilobed lesion with heterogeneous signal intensity in the midline suboccipital region with a connection through the occipital bone to the intracranial compartment.
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Figure 7b. Atretic meningocele. Axial T2-weighted (a) and contrast-enhanced T1-weighted (b) surface coil MR images show a bilobed lesion with heterogeneous signal intensity in the midline suboccipital region with a connection through the occipital bone to the intracranial compartment.
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Nasal Gliomas
Nasal gliomas occur near the root of the nose (where the cranial portion of the nose joins the forehead), are composed of dysplastic glial tissue, and are congenital nonneoplastic lesions best categorized as heterotopia (17). A nasal glioma may be connected to the brain by a stalk of tissue in up to 15% of cases, but the stalk does not contain a direct fluid-filled tract that communicates with the subarachnoid spaces; therefore, a nasal glioma is distinct from an encephalocele, which does contain such a connection to the intracranial subarachnoid spaces (Fig 1). Nasal gliomas are intranasal in 30% of cases, extranasal in 60%, and mixed in 10% (7,17). Extranasal gliomas are usually seen in a paramedian location at the bridge of the nose external to the nasal passage (Fig 8), whereas intranasal lesions are usually located within the nasal passage medial to the middle turbinate bone. Surgical resection is used to treat these lesions. Nasal gliomas are often isointense relative to normal brain at MR imaging (Fig 9), which is the imaging modality of choice. High-resolution surface coil MR imaging is often useful in demonstrating the intracranial stalk.
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Figure 9a. Nasal glioma. Coronal T1-weighted (a) and sagittal T2-weighted (b) MR images show bilateral paranasal masses. On T1- and T2-weighted images, the signal intensity of nasal glioma is similar to that of brain.
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Figure 9b. Nasal glioma. Coronal T1-weighted (a) and sagittal T2-weighted (b) MR images show bilateral paranasal masses. On T1- and T2-weighted images, the signal intensity of nasal glioma is similar to that of brain.
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Dermoid and Epidermoid Cysts
Dermoid and epidermoid cysts are found in a variety of locations around the skull and midface. They are thought to occur as a result of the persistence of ectodermal elements at sites of suture closure, neural tube closure, and diverticulation of the cerebral hemispheres as discussed earlier (7,17). Dermoid cysts contain ectoderm and skin elements, whereas epidermoid cysts contain ectoderm but no skin elements. Dermoid and epidermoid cysts are most commonly seen in midline and frontotemporal locations, followed by parietal locations. Midline locations include the anterior fontanelle, glabella, nasion, vertex, and subocciput (Figs 10, 11). Sutures that are commonly affected include the frontozygomatic, sphenofrontal, sphenosquamosal, squamosal, coronal, lambdoid, and parietomastoid sutures. Nasal dermal sinuses and dermoid and epidermoid cysts occur at multiple locations from the glabella to the columella. These lesions may be associated with external skin ostia or deep sinus tracts, which may potentially extend intracranially (Fig 1) (7,17). CT attenuation varies depending on content (eg, fat attenuation with dermoid cysts, fluid attenuation with epidermoid cysts). Similarly, the signal intensity at MR imaging depends on the contents of the cyst and may range from pure fluid signal intensity (hypointense on T1-weighted images, hyperintense on T2-weighted images) in an epidermoid cyst to a more complex signal intensity (hyperintense on T1-weighted images, hypointense on T2-weighted images) in a dermoid cyst. Epidermoid cysts typically have bright signal intensity on isotropic diffusion-weighted MR images (Fig 12) (18). Nasal dermoid cysts may be associated with a sinus tract that extends for variable distances in the prenasal space to the foramen cecum. High-resolution surface coil MR imaging is very useful in determining if there is a connecting tract to the foramen cecum (Fig 1). In such cases, sagittal T1-weighted or heavily T2-weighted images may best delineate the tract running beneath the nasal bones to the foramen. If the fluid is hyperintense on T1-weighted images, the tract will often be seen on both unenhanced T1-weighted images and T2-weighted images. Nasal dermoid and epidermoid cysts are typically surgically resected due to the potential for an intracranial connection and the risk of CNS infection, as well as for cosmetic reasons (19).
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Figure 10a. Nasal dermoid cyst. Axial T2-weighted (a) and sagittal unenhanced T1-weighted (b) MR images obtained with a 2-mm surface coil show a complex nasal lesion with a well-defined cyst at the nasal tip. Two additional cysts are seen along the septal cartilage. There was no intracranial connection. The hyperintensity of the lesion on the T1-weighted image reflects the lipid contents of the cyst.
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Figure 10b. Nasal dermoid cyst. Axial T2-weighted (a) and sagittal unenhanced T1-weighted (b) MR images obtained with a 2-mm surface coil show a complex nasal lesion with a well-defined cyst at the nasal tip. Two additional cysts are seen along the septal cartilage. There was no intracranial connection. The hyperintensity of the lesion on the T1-weighted image reflects the lipid contents of the cyst.
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Figure 11a. Occipital dermoid cyst. Sagittal T2-weighted (a) and axial contrast-enhanced T1-weighted (b) surface coil MR images show a midline suboccipital cystic lesion (white arrow), with a sinus tract in the occipital bone (black arrow) and an infratorcular intracranial connection. The enhancement is due to infection of the cyst.
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Figure 11b. Occipital dermoid cyst. Sagittal T2-weighted (a) and axial contrast-enhanced T1-weighted (b) surface coil MR images show a midline suboccipital cystic lesion (white arrow), with a sinus tract in the occipital bone (black arrow) and an infratorcular intracranial connection. The enhancement is due to infection of the cyst.
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Figure 12. Epidermoid cyst with intracranial extension. Sagittal diffusion-weighted MR image demonstrates a subfrontal intracranial epidermoid cyst with bright signal intensity (arrow). (Case courtesy of Susan Blaser, MD, Hospital for Sick Children, Toronto, Ontario, Canada.)
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Benign Tumors
Vascular Lesions.—
Vascular anomalies of the face and scalp in childhood have generally been classified as either hemangiomas or vascular malformations. Hemangiomas are benign endothelial tumors that undergo cellular proliferation and accompanying enlargement in the 1st year of life, followed by gradual involution during childhood. Vascular malformations, on the other hand, consist of some combination of congenitally abnormal veins, lymphatic vessels, capillaries, or arteries. They tend to enlarge proportionately and progressively with the growth of the child, unless acutely complicated by trauma, hemorrhage, infection, or the hormonal influences of puberty (20–26).
Hemangiomas are the most common tumor of infancy. It is estimated that they occur in 1%–2% of the population in general and in up to 10% of white persons (24). They occur more frequently in girls than in boys (
3:1 ratio), and their prevalence is higher in premature infants. Hemangiomas are present at birth in 30%–40% of cases, with the remainder generally being appreciated in the first months of life. More than one-half are located in the head and neck, with the most common sites of involvement being the midcheek, upper lip, and upper eyelid (22). Hemangiomas can be classified as focal, localized to a particular region, or diffuse and segmental. They may be superficial (red in appearance) or deep (flesh colored or blue in appearance) (24). The vast majority are managed clinically without imaging. However, hemangiomas that might affect the airway, disturb vision, or be associated with other anomalies may be imaged. These hemangiomas include cervicofacial or "beard distribution" hemangiomas, which are associated with subglottic hemangiomas, and deep bilateral parotid hemangiomas, which may directly impinge on the airway. Periorbital hemangiomas are often imaged to assess the extent of retro-orbital involvement and the potential for compromise of orbital movement and vision. Diffuse and segmental hemangiomas of the face often trigger neuroimaging for assessment of features of PHACE(S) syndrome, which consists of posterior fossa malformations, hemangiomas, arterial anomalies related to the intracranial circulation, coarctation of the aorta or cardiac anomalies, eye abnormalities, and, occasionally, sternal clefting or supraumbilical raphe (a fibrous band or cleft in the midline above the umbilicus) (Fig 13) (26–30). Multiplanar MR imaging provides an operator-independent method of demonstrating the deep and superficial extent of these masses. Typically, proliferating hemangiomas are isointense relative to muscle on T1-weighted images, have high signal intensity on T2-weighted images, demonstrate homogeneous enhancement, and have internal flow voids (21). The flow voids are highly suggestive but not a specific feature of hemangiomas. Rarely, malignant tumors such as alveolar soft-tissue sarcoma, fibrosarcoma, or rhabdomyosarcoma demonstrate similar vessels. An arteriovenous malformation or fistula is a high-flow lesion that may also demonstrate flow voids—usually, however, without a discrete soft-tissue mass at imaging. Therefore, clinical correlation and follow-up by an experienced radiologist is essential for characterization, and if the diagnosis is uncertain, biopsy might be considered (23). Hemangiomas do involute over time and are characterized by progressive fibrofatty metaplasia, with internal areas whose signal intensity is similar to that of fat at MR imaging (26). Because of this involution, the majority of hemangiomas do not require intervention. However, those that are ulcerated or affect vital structures may be treated initially, often with systemic corticosteroids as the first-line therapy (24).
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Figure 13a. PHACE syndrome. (a) Axial T2-weighted MR image reveals a predominantly preseptal right-sided soft-tissue mass that is isointense relative to brain. (b) Coronal contrast-enhanced T1-weighted MR image shows an intensely enhancing mass in the right cerebellopontine angle (arrow), a finding that is consistent with a hemangioma.
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Figure 13b. PHACE syndrome. (a) Axial T2-weighted MR image reveals a predominantly preseptal right-sided soft-tissue mass that is isointense relative to brain. (b) Coronal contrast-enhanced T1-weighted MR image shows an intensely enhancing mass in the right cerebellopontine angle (arrow), a finding that is consistent with a hemangioma.
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Venous malformations include a wide spectrum of dysmorphic and congenital venous lesions and are characterized clinically by a soft and nonpulsatile mass, often of bluish color. Up to 40% of venous malformations occur in the head and neck (26). MR imaging demonstrates a hyperintense mass on T2-weighted images, with occasional septation and variable enhancement. Phleboliths, which appear as a focal signal void, are a relatively specific characteristic (Fig 14) (21). As a low-flow lesion, the flow voids demonstrated with proliferating hemangiomas or high-flow arteriovenous malformations are not seen in venous malformations. Treatment typically involves some combination of sclerotherapy and surgical removal (26).
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Figure 14a. Facial venous malformation. Axial (a) and coronal (b) T2-weighted MR images show a markedly hyperintense mass containing hypointense phleboliths in the masticator space.
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Figure 14b. Facial venous malformation. Axial (a) and coronal (b) T2-weighted MR images show a markedly hyperintense mass containing hypointense phleboliths in the masticator space.
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A collection of nonmuscular scalp veins that communicate with the intracranial venous sinuses is described as sinus pericranii. These abnormal veins are often congenital in origin, although some investigators have postulated trauma as the cause in at least some cases. These veins are commonly appreciated in the frontal and parietal regions (Fig 15). Treatment usually consists of ligation of the communicating veins and surgical removal of the sinus itself (25).
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Figure 15a. Sinus pericranii. (a) Lateral radiograph shows diffuse as well as more discrete areas (arrows) of cortical thinning. (b) Sagittal contrast-enhanced T1-weighted MR image demonstrates a serpiginous scalp mass with avid enhancement. (c) Sagittal venous phase brain angiogram obtained after the injection of contrast material into the internal carotid artery demonstrates multiple small, transosseous vessels that supply the scalp venous malformation.
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Figure 15b. Sinus pericranii. (a) Lateral radiograph shows diffuse as well as more discrete areas (arrows) of cortical thinning. (b) Sagittal contrast-enhanced T1-weighted MR image demonstrates a serpiginous scalp mass with avid enhancement. (c) Sagittal venous phase brain angiogram obtained after the injection of contrast material into the internal carotid artery demonstrates multiple small, transosseous vessels that supply the scalp venous malformation.
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Figure 15c. Sinus pericranii. (a) Lateral radiograph shows diffuse as well as more discrete areas (arrows) of cortical thinning. (b) Sagittal contrast-enhanced T1-weighted MR image demonstrates a serpiginous scalp mass with avid enhancement. (c) Sagittal venous phase brain angiogram obtained after the injection of contrast material into the internal carotid artery demonstrates multiple small, transosseous vessels that supply the scalp venous malformation.
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Lymphatic malformations of the head and neck develop from lymphatic sacs that fail to communicate with the remainder of the lymphatic system. They are most commonly appreciated in the posterior triangle of the neck and axilla in the first 2 years of life. Macrocystic lymphatic malformations, sometimes referred to as cystic hygromas, have characteristic MR imaging features, manifesting as multiseptate cystic masses, often with intracystic hemorrhage or fluid levels (Fig 16). Treatment typically involves some combination of sclerotherapy and surgical resection (21).
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Figure 16a. Lymphatic malformation. Axial (a) and sagittal (b) T2-weighted MR images demonstrate a macrocystic, multiseptate mass with layered intracystic hemorrhage in the left posterior triangle of the neck.
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Figure 16b. Lymphatic malformation. Axial (a) and sagittal (b) T2-weighted MR images demonstrate a macrocystic, multiseptate mass with layered intracystic hemorrhage in the left posterior triangle of the neck.
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PHACE Syndrome.—
Rarely, large segmental or plaquelike hemangiomas of the scalp and face are associated with a spectrum of extracutaneous manifestations. PHACE(S) is the acronym coined to describe this spectrum. The majority of affected patients have only one accompanying finding, with posterior fossa and arterial abnormalities being the most common (28–31). Specific reported infratentorial abnormalities include Dandy-Walker malformation, ipsilateral cerebellar hypoplasia, and cerebellar vermian hypoplasia and cortical dysgenesis, among others (32). Contrast-enhancing masses involving the cerebellopontine angles, cerebellar meninges, hypothalamus, and perichiasmatic cisterns have also been described and are presumed to represent intracranial hemangiomas, since their growth and involution parallel that of the accompanying extracranial hemangiomas (Fig 13) (33). Specific arterial abnormalities include persistent primitive fetal arteries—most commonly a persistent trigeminal artery—and agenesis of the internal carotid or vertebral arteries, anomalies that are more commonly seen ipsilateral to the hemangioma (34). Progressive bilateral vasculopathy with stenoses, aneurysm formation about the vessels of the circle of Willis, and a moya-moya type of collateral vessel formation have also been noted (33,34).
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Acquired Lesions
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Sarcomas of the Head and Neck
According to the Agency for Research on Cancer, soft-tissue sarcomas account for 4%–8% of cancers in patients up to 14 years of age (2,35–37). Whereas head and neck primary sarcomas represent only 5%–15% of all adult sarcomas, 35% of all sarcomas in the pediatric population manifest in the head and neck (38–40).
Rhabdomyosarcoma.—
Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood (60% of cases) (38,41,42). Rhabdomyosarcomas of the head and neck generally have a better prognosis than those in the extremities. In most studies, approximately one-third of pediatric rhabdomyosarcomas occur in the head and neck region, the most common location (43,44). Rhabdomyosarcomas are slightly more common in males, and two-thirds of tumors occur in children less than 6 years of age (42). The most common histologic type is embryonal rhabdomyosarcoma, which accounts for 70%–80% of cases and is considered to have a more favorable prognosis. The second most common type is alveolar rhabdomyosarcoma, which accounts for 10%–20% of cases and is the type most frequently seen in adolescents and young adults (44). Alveolar rhabdomyosarcoma has an unfavorable prognosis, and treatment usually involves a combination of surgery, radiation therapy, and chemotherapy.
The presenting symptoms of rhabdomyosarcoma are variable and depend on tumor location, patient age, and the stage of the disease at diagnosis. In the head and neck, rhabdomyosarcomas are classified as (a) orbital, (b) parameningeal (including the pterygopalatine fossae, paranasal sinuses, middle ear, and mastoid process), or (c) superficial (Fig 17). At clinical examination, rhabdomyosarcoma may be difficult to differentiate from other soft-tissue lesions. The four cases of rhabdomyosarcoma reported by Chigurupati et al (45) were initially misdiagnosed as hemangioma, lymphangioma, lymphoma, and lymphadenopathy, respectively. In addition, Pratt et al (46) reported a significant delay in the diagnosis because the "swellings" identified clinically were initially treated as infection and were not recognized as potential neoplasms. Rhabdomyosarcoma may also be initially misdiagnosed as LCH or mastoiditis with osseous erosion when it occurs in the temporal bone. Because the current classification system is based on the degree of tumor spread at the time of diagnosis, imaging evaluation should include CT or MR imaging of the primary site and surrounding structures. Bone scintigraphy is also part of the initial work-up. For presurgical planning, it is necessary to make an accurate assessment of tumor size and extent, bone erosion, and intracranial invasion.
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Figure 17a. Naso-orbital rhabdomyosarcoma. (a) Axial contrast-enhanced CT scan shows a rim-enhancing soft-tissue mass of the left naris. (b) Axial contrast-enhanced CT scan of the orbit in a different patient shows a large, lateral orbital wall mass eroding bone and causing severe proptosis.
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Figure 17b. Naso-orbital rhabdomyosarcoma. (a) Axial contrast-enhanced CT scan shows a rim-enhancing soft-tissue mass of the left naris. (b) Axial contrast-enhanced CT scan of the orbit in a different patient shows a large, lateral orbital wall mass eroding bone and causing severe proptosis.
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At CT, most rhabdomyosarcomas are poorly defined and relatively homogeneous lesions with bone destruction. At MR imaging, they are homogeneous masses that are isointense to minimally hyperintense relative to muscle on T1-weighted images and hyperintense on T2-weighted images (47–49). Rhabdomyosarcomas manifest with mild to moderate enhancement at both CT and MR imaging. The bone destruction typically manifests as areas of signal loss in cortical bone with or without bone marrow infiltration. These findings may be seen with both unenhanced T1-weighted MR imaging sequences (which is probably the most useful sequence) and T2-weighted sequences. MR imaging is also the technique of choice in assessing the therapeutic response.
Fibrosarcoma.—
Although rare, fibrosarcoma is one of the more common types of soft-tissue sarcoma. Approximately 5% occur in the head and neck region (50–52), and 25%–40% occur in children during the first 5 years of life, with up to 92% detected in the 1st year of life (53,54). The tumor is slightly more common in boys (60% of cases) (55). Congenital fibrosarcoma is a relatively indolent sarcoma that must be differentiated from the more aggressive spindle cell sarcoma of childhood. Infantile fibrosarcomas usually manifest as asymptomatic, enlarging soft-tissue masses, most commonly in the skin and soft tissues of the neck. Tumors may grow rapidly and reach a large size within a few weeks or months. At CT, fibrosarcoma generally has a homogeneous appearance with variable enhancement and bone remodeling. It has low to intermediate signal intensity with all MR imaging sequences. CT and MR imaging both demonstrate extension or infiltration into adjacent structures (Fig 18).
Langerhans Cell Histiocytosis
The term histiocytosis refers to a group of disorders that have in common the proliferation of pathologic Langerhans cells, a type of histiocyte from the monocyte-macrophage cell line (56). LCH has been divided into three forms on the basis of the organs involved, patient age at onset, and clinical course: localized, chronic disseminated, and fulminant-disseminated. Localized LCH is the mildest and most common form (70%–75% of cases) and involves either bone or lung. Lung involvement is uncommon in children, whereas bone involvement is typical and visceral involvement is occasionally seen. LCH corresponds to the so-called eosinophilic granuloma. Peak prevalence of LCH occurs between 1 and 4 years of age, and the disorder has a slight male predilection (57). Because the localized lesions in this age group are frequently painful lumps misdiagnosed as local trauma or seborrheic skin lesions similar to cradle cap, the disease may go undiagnosed (58). Head and neck manifestations of LCH occur in up to 73%–82% of children during the course of the disease. The skull and the skin are frequently involved (58–61) and were the most common sites of involvement in the series reported by DiNardo and Wetmore (58) and Irving et al (60). In a group study of 42 children by Meyer et al (61), 35 (83%) had at least one bone lesion. The calvaria is the most common location of osseous LCH (62). Other commonly involved sites include the orbit, maxilla, mandible, and temporal bone. Lesions of the temporal bone may manifest with cutaneous ear involvement similar to external otitis or with polyps of lesional tissue extending into the external auditory canal. If the mastoid portion of the temporal bone is involved, the disease may mimic a postauricular abscess, phlegmon, or otomastoiditis. Cranial nerves VII and VIII may also be involved, with symptoms of hearing loss and vertigo (63). At radiography, bone lesions in LCH usually appear lytic. Their borders may be either well or poorly defined, and they are classically described as "punched-out" lesions without reactive sclerosis or periosteal reaction (Fig 19) (64). In the skull, the lesion edges typically have a beveled appearance due to asymmetric destruction of the inner and outer tables of the skull. At CT, LCH appears as an enhancing soft-tissue mass with bone erosion (Fig 19b). At MR imaging, lesions have low to intermediate signal intensity on T1-weighted images, are hyperintense on T2-weighted images, and enhance diffusely on contrast-enhanced images. Extensive osseous destruction is often seen at MR imaging as well (Fig 20) (63). A combination of contrast-enhanced CT and MR imaging is often required for accurate long-term follow-up of repair of bone destructive lesions and of resolution of soft-tissue masses. Intracranial involvement by LCH is best followed up with MR imaging and usually manifests as hyperintense lesions on T2-weighted images.
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Figure 19a. LCH of the skull base. (a) Radiograph of the skull shows a typical punched-out lesion of the right occipital bone (black arrow) and a large erosive lesion of the left temporal bone (white arrow). (b) Axial CT scan again shows the erosive lesion of the left temporal bone (arrow), as well as a smaller erosive lesion of the right temporal bone (arrowhead).
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Figure 19b. LCH of the skull base. (a) Radiograph of the skull shows a typical punched-out lesion of the right occipital bone (black arrow) and a large erosive lesion of the left temporal bone (white arrow). (b) Axial CT scan again shows the erosive lesion of the left temporal bone (arrow), as well as a smaller erosive lesion of the right temporal bone (arrowhead).
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Figure 20a. LCH of the right orbit. Contrast-enhanced axial T2-weighted (a) and sagittal T1-weighted (b) MR images show a heterogeneous, enhancing, bone-eroding mass along the superior orbital rim.
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Figure 20b. LCH of the right orbit. Contrast-enhanced axial T2-weighted (a) and sagittal T1-weighted (b) MR images show a heterogeneous, enhancing, bone-eroding mass along the superior orbital rim.
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Metastatic Neuroblastoma
Neuroblastoma is usually a secondary metastatic lesion rather than a primary lesion of the head and neck. It may manifest with Horner syndrome and a metastatic mass at the skull base involving the cervical sympathetic ganglion. Clinical findings related to tumor metastases may be investigated with various imaging modalities (65). Traditionally, the radiologic evaluation of neuroblastoma has included intravenous urography, US, CT, bone scintigraphy, and metaiodobenzylguanidine scintigraphy. Neuroblastoma commonly metastasizes to the lateral orbital walls, manifesting clinically as two "black eyes" ("raccoon sign"), and to the skull base and calvaria (Fig 21). Recently, MR imaging has been demonstrated 
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Abstract
LEARNING OBJECTIVES FOR TEST...
