eMedicine Specialties > Radiology > Brain/Spine
Dermoid Tumor, CNS
Updated: Feb 5, 2010
Introduction
Background
Dermoid tumors are not true neoplasms but are inclusion cysts composed of ectodermal elements. They are uncommon lesions, accounting for approximately 0.3% of all brain tumors. Dermoid tumors are often discussed with epidermoid tumors because of their similar appearance and developmental origin.
The dermoid tumor is hyperintense on this gadolinium-enhanced coronal T1-weighted image. Note the heterogeneity of the lesion posteriorly. The hyperintensity results not from the gadolinium contrast enhancement but instead from the short T1 of fat. Multiple hyperintense foci consistent with fat droplets are demonstrated in the subarachnoid spaces. A mild midline septal shift to the left is noted; this is due to compression of the right lateral ventricle by the dermoid tumor. A chemical-shift artifact is also noted at the superior marginal surface of the lesion.
Recent studies
Orakcioglu et al reviewed the charts of 5 men and 2 women with intracranial dermoid cysts and found that clinical presentations included focal neurologic deficits, epileptic seizures, persistent headache, mental changes, and psycho-organic syndromes. One patient underwent delayed ventriculo-peritoneal shunting after ruptured fatty particles caused obstructive hydrocephalus. In 3 patients, despite dermoid rupture into the subarachnoid space, hydrocephalus did not develop. In one patient, diffuse vascular supra-tentorial lesions occurred as a result of aseptic meningitis. The authors noted that diffusion-weighted imaging (DWI) hyperintensity in dermoid cysts is related to a decrease of water proton diffusion and should be used for both the diagnosis and follow-up of these lesions. In addition, they noted that although rupture does not necessarily cause hydrocephalus, radical removal of the tumor and close monitoring of ventricular size are necessary.[1 ]
A study by Jolapara et al indicated that diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) can together be used to analyze the microstructural anatomy of epidermoid tumors. Reporting on 10 patients with epidermoid tumors, the investigators measured directionally averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), DTM-like fractional anisotropy (FA), diffusion tensor mode values, and linear (CL), planar (CP), and spherical (CS) anisotropy from the tumors, as well as from normal-appearing white matter. The authors found that the epidermoid tumors demonstrated high FA but, according to the Dav and eADC values, no indication of diffusion restriction. Diffusion tensor mode values were close to -1, and CP values within the tumor were high.[2 ]
Similar results were obtained by Santhosh et al in a DTI/DTM analysis in 3 patients with epidermoid cysts. FA, Dav, eADC, and DTM, such as CL, CP, and CS, were measured from the tumor core and normal-appearing white matter. Epidermoid cysts showed high FA, with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were high, but not as high as that for the white matter. CP values were higher and CL values were lower than those obtained for the white matter in various regions.[3 ]
Handu et al analyzed the aspirates of epidermal inclusion cysts to identify cytologic features. The aspirates showed a clear background with high cellularity, along with nucleate and anucleate squames. In some cases, keratinous material was present but less than the cellular elements. In 31 cases, a diagnosis of infected EIC was made on the basis of dense inflammatory infiltrate in addition to the squames. Of 56 cases for which histopathology was available, 45 cases of EIC were diagnosed, 5 cases of dermoid cyst, 2 cases of branchial cyst, 2 cases of pilomatricoma, 1 case of sebaceous cyst, and 1 case of thyroglossal cyst.[4 ]
Pathophysiology
Dermoid and epidermoid tumors contain stratified squamous epithelium found in skin, but they also have histologic differences. Epidermoid tumors are lined with stratified squamous epithelium and have an outer connective tissue capsule. Dermoid tumors have an outer connective tissue capsule and are lined with stratified squamous epithelium that also contains hair follicles, sebaceous glands, and sweat glands. Centrally, both tumors contain desquamated epithelial keratin and some lipid material. The external surface of both tumors commonly has a smooth, lobulated, pearly appearance.[5 ]
Dermoid tumors are thought to arise from misplaced ectodermal elements during the third to fifth week of embryonic life, when the neural tube closes at the midline. This may explain the frequent midline location of dermoid tumors. In contrast, epidermoid tumors are often located lateral to the midline of the cranium. Dermoid tumors are more commonly associated with dermal sinus tracts and spinal abnormalities than are epidermoid tumors.
Congenital epidermoid tumors may develop from inclusion of ectodermal epithelial elements at the time of neural tube closure or during the formation of the secondary cerebral vesicles. Acquired epidermoid tumors are believed to form due to trauma, frequently lumbar puncture, with epithelial cells deposited within the lumbar spinal canal. Sites of epithelial deposition can occur anywhere between the neural tube and the overlying skin surface. This distribution may account for the presence of dermal sinus tracts or dimples, which are more commonly associated with dermoid tumors.
Dermoid tumors are solitary; they expand slowly over many years due to the central accumulation of epithelial debris and glandular secretions. Common intracranial sites of dermoid tumors include the posterior fossa (within the fourth ventricle or cerebellar vermis) and the suprasellar region.
A congenital lumbar dermal sinus may terminate in an epidermoid or, less frequently, dermoid tumor within or near the conus medullaris or cauda equina and is often associated with spinal dysraphism. A congenital nasal dermal sinus may be associated with dermoid or epidermoid tumors. Other dermoid tumor sites include the scalp, skull, and orbit. Epidermoid tumors are most commonly located near the cerebellopontine angle, but they may also occur in parasellar areas and may be intradiploic in cranial bones. Intracerebral epidermoid occurrence is very rare.
Frequency
United States
Dermoid tumors account for approximately 0.3% of brain tumors and occur 4-10 times less frequently than do epidermoid tumors.
Mortality/Morbidity
- Central nervous system (CNS) dermoid and epidermoid tumors are usually benign, slow-growing lesions that rarely undergo malignant transformation.
- Morbidity depends on the location of the tumor and on the involvement of adjacent structures. The rupture of a dermoid tumor can cause a granulomatous chemical meningitis that, in rare cases, produces infarction from arterial vasospasm.
Race
No known racial predilection exists.
Sex
There is a slight male predominance of dermoid tumors. Epidermoid tumors occur with similar frequency in male and female patients.
Age
Intracranial dermoid tumors are seen most frequently in patients up to 20 years of age. In contrast, epidermoid tumors are most often first diagnosed in patients aged 40-50 years.
Anatomy
Dermoid tumors are often located at the cranial midline (as seen in the images below) within the posterior cranial fossa, suprasellar cistern, and subfrontal areas. Epidermoid tumors are typically lateral and are most frequently located in the cerebellopontine angle; in the suprasellar and parasellar regions; in choroidal, sylvian, and interhemispheric fissures; or intraventricularly.
Elderly woman with chronic headaches. A nonenhanced computed tomography (CT) scan of the head demonstrates a well-circumscribed, cystic, low-attenuating lesion located at the cranial midline in the suprasellar region, posterior to the third ventricle. A small focus of calcification is noted at the posterior margin of the tumor.
The suprasellar lesion (same patient as in the image above) is hypointense on a subsequent axial T1-weighted image. The crescentic posterior rim of hyperintensity represents the fat chemical–shift artifact.
Gadolinium-enhanced axial T1-weighted image demonstrating nodular focus of enhancement in the right side of the suprasellar lesion (same patient as in the above 2 images).
Axial T2-weighted fast spin-echo magnetic resonance image demonstrating a hyperintense cystic component in the lesion (same patient as in the above 3 images).
Spinal dermoid tumors are most commonly situated near the thoracolumbar junction and tend to involve the conus medullaris and cauda equina. About 50% are intradural intramedullary, and 50% are intradural extramedullary. Extradural location is least common. Less common sites of dermoid tumors include the scalp (the most common location in childhood), skull, orbit, nasal and oral cavities, and neck.
Presentation
Dermoid tumors grow slowly. Symptoms and signs are associated with the location of the tumor and the mass/pressure effect on adjacent tissues. Suprasellar tumors can cause visual abnormalities from compression of the optic chiasm. Diabetes insipidus and hypopituitarism may occur. Parasellar tumors may be associated with seizures from mass effect or extension to the temporal lobe and sylvian fissure.
Intraventricular dermoid tumors are most frequently located in the fourth ventricle and sometimes cause hydrocephalus. It has been suggested that the cerebrospinal fluid (CSF) flow may occur through interstices on the surface of the tumor.
Dermoid tumors in the spinal canal may cause back or leg pain due to mass effect. Headache and meningitis may occur if an associated dermal sinus tract becomes infected. Vertebral abnormalities, such as diastematomyelia, hemivertebra, and scoliosis, are frequently associated with dermal sinuses, dermoid tumors, or epidermoid tumors.
Dermoid tumors can rupture, releasing lipid contents into the ventricular or subarachnoid spaces (as seen in the image below). This causes a chemical meningitis that can lead to recurrent symptoms, most commonly headache. The subsequent meningeal inflammation may result in arterial vasospasm and, rarely, stroke and death.
Axial gadolinium-enhanced T1-weighted image of a lesion demonstrating a hyperintense signal. In addition, multiple small foci of hyperintense signal are present along the sulci of the right temporal lobe. These represent fat droplets in the subarachnoid space, left by the focal rupture of the dermoid tumor.
Preferred Examination
Dermoid tumors are often first detected on computed tomography (CT) scans. Low attenuation values consistent with fat are suggestive of the diagnosis of dermoid tumor. Calcifications are frequent in dermoid tumors and are best seen through CT scanning.
Magnetic resonance imaging (MRI) is the preferred diagnostic procedure — not only because of its high spatial resolution, but also because of its multiplanar format — for optimal depiction of the location of dermoid tumors and the involvement of adjacent structures. The fat components that are characteristic of dermoid tumors are well demonstrated through MRI. Fat droplets located in the ventricles or subarachnoid spaces due to dermoid tumor rupture also are better appreciated with MRI than through other studies.
Differential Diagnoses
Arachnoid Cyst
Craniopharyngioma
Epidermoid, Brain
Other Problems to Be Considered
Ependymoma
Hemangioblastoma
Cystic astrocytoma
Germinoma
Cysticercosis
Teratoma
Lipoma
Radiography
Findings
Focal erosion of the calvarial bone may be present adjacent to a dermoid tumor of the scalp or orbit. In particular, epidermoid tumors of the skull can cause local bone expansion or erosion and round, intradiploic, lytic lesions with a thin, sclerotic margin. Deformity of the sella may occur from parasellar dermoid tumors. Spinal dermoid tumors can cause focal vertebral bone erosion, widening of the vertebral spinal canal, and flattening of the pedicles and laminae.
Degree of Confidence
Large, calvarial dermoid tumors can be visualized on plain skull radiographs, but radiographs have low sensitivity in depicting intracranial dermoid tumors. CT scanning and MRI demonstrate the location and imaging features of intracranial lesions.
Computed Tomography
Findings
A dermoid tumor appears as a well-circumscribed, predominantly cystic mass on a CT scan (as seen in the images below), with decreased attenuation in the range of -20 to -40 HU because of its fat content. The tumor may appear slightly heterogeneous due to additional ectodermal elements, including hair follicles, sebaceous glands, and sweat glands. Calcifications are frequent in the wall of the tumor.
Elderly woman with chronic headaches. A nonenhanced computed tomography (CT) scan of the head demonstrates a well-circumscribed, cystic, low-attenuating lesion located at the cranial midline in the suprasellar region, posterior to the third ventricle. A small focus of calcification is noted at the posterior margin of the tumor.
Coronal computed tomography (CT) scan of the paranasal sinuses in a 26-year-old man with sinusitis. A large, well-circumscribed, low-attenuating, cystic lesion is present in the right temporal lobe, lateral to the cranial midline. Note the peripheral, marginal calcification in the lesion. No erosion is seen in the adjacent bone of the sella.
Contrast enhancement is uncommon, but some enhancement may be seen in the wall. If enhancement is present in a suprasellar tumor, other diagnoses should be considered, including craniopharyngioma, teratoma, or germinoma. Fat droplets in the ventricular or subarachnoid spaces strongly suggest rupture of a dermoid tumor.
Dermoid tumors located in the fourth ventricle do not often cause obstructive hydrocephalus. The differential diagnoses include tumors that do commonly cause hydrocephalus, such as ependymomas, medulloblastomas, hemangioblastomas, or cystic astrocytomas of the fourth ventricle.
Epidermoid tumors often have attenuation similar to CSF, but they may have hyperattenuation on nonenhanced images because of high tumoral protein content, hemorrhage, or cellular debris. The wall of epidermoid tumors may sometimes enhance after intravenous administration of contrast medium.
Degree of Confidence
CT scanning is useful in the initial diagnosis of CNS dermoid tumors if the typical findings are present. A fat-fluid level in the ventricles or fat droplets in the subarachnoid spaces due to dermoid tumor rupture adds additional confidence to the diagnosis.
MRI may be performed to further localize the lesion and to identify any involvement of adjacent structures.
Magnetic Resonance Imaging
Findings
Most dermoid tumors have signal intensity characteristics similar to fat—that is, they are hyperintense on T1-weighted images and hypointense on T2-weighted images. Fat-suppression techniques may be helpful in confirming the presence of fat in the lesion. Centrally, dermoid tumors may appear inhomogeneous due to the presence of hair follicles, calcifications, and cellular debris.
Rupture of a dermoid tumor (as seen in the images below) can result in fat droplets in the subarachnoid spaces or ventricles, with T1 high signal intensity. Fat-fluid levels may be found anteriorly in the lateral ventricles. A chemical-shift artifact is often present on T2-weighted images as a markedly hypointense band posterior at the fat-fluid interface.
Axial gadolinium-enhanced T1-weighted image of a lesion demonstrating a hyperintense signal. In addition, multiple small foci of hyperintense signal are present along the sulci of the right temporal lobe. These represent fat droplets in the subarachnoid space, left by the focal rupture of the dermoid tumor.
The dermoid tumor is hyperintense on this gadolinium-enhanced coronal T1-weighted image. Note the heterogeneity of the lesion posteriorly. The hyperintensity results not from the gadolinium contrast enhancement but instead from the short T1 of fat. Multiple hyperintense foci consistent with fat droplets are demonstrated in the subarachnoid spaces. A mild midline septal shift to the left is noted; this is due to compression of the right lateral ventricle by the dermoid tumor. A chemical-shift artifact is also noted at the superior marginal surface of the lesion.
Vascular displacement or encasement by the dermoid tumor may be demonstrated by means of magnetic resonance angiography (MRA) or CT angiography (CTA).
Epidermoid tumors are usually hypointense on T1-weighted images and hyperintense on T2-weighted images (ie, epidermoid tumors are slightly more hyperintense with a heterogeneous signal relative to CSF on T1 and T2 sequences). (See the images below.)
This epidermoid tumor is isointense relative to cerebrospinal fluid (CSF) on a nonenhanced T1-weighted axial image. The lobulated extra-axial mass surrounds the right cerebral peduncle and extends to the suprasellar region and the interpeduncular cistern. In contrast, a dermoid tumor will demonstrate a high T1 signal intensity because it contains fat constituents.
Epidermoid tumor (same as in the image above) demonstrating no enhancement in this contrast-enhanced T1-weighted image.
T2-weighted axial image demonstrating a hyperintense signal (in the same epidermoid tumor as in the above 2 images) that is similar to the signal intensity of cerebrospinal fluid (CSF). Compression by the epidermoid tumor mass has widened the interpeduncular cistern and narrowed the right cerebral peduncle.
Coronal T1-weighted image demonstrating a hypointense epidermoid tumor (same tumor as in the above 3 images). Note that the epidermoid has higher signal intensity than the adjacent CSF. There is a compressive mass effect on the third ventricle, but hydrocephalus is minimal.
Fast fluid-attenuated inversion recovery (FLAIR) sequences demonstrate slightly higher signal intensity than do fast spin-echo T2-weighted sequences in epidermoid tumors. Echo-planar diffusion-weighted imaging shows a hyperintense signal within epidermoid tumors. The calculated apparent diffusion coefficient (ADC) exceeds that of CSF, but it is less than that of the brain substance.
Magnetic resonance spectroscopy in epidermoid tumors has a lactate peak at 1.3 ppm. Additional protein metabolites, when present, can simulate brain abscess. Epidermoid tumors and arachnoid cysts have similar fluid attenuation on CT scans. They often have similar signal intensities on T1- and T2-weighted magnetic resonance images. FLAIR sequences frequently demonstrate a heterogeneously increased signal intensity in epidermoid tumors as compared with that in arachnoid cysts. Diffusion-weighted imaging shows definitive high signal intensity (whiteness) in epidermoid tumors and low signal intensity (blackness) in arachnoid cysts.
Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Systemic Fibrosis. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.
NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
Degree of Confidence
A unilocular cystic mass located at or near the cranial midline, with signal intensity similar to that of fat, is highly suggestive of a dermoid tumor. Epidermoid tumors are rarely hyperintense on T1-weighted images and may simulate a dermoid tumor. Definitive diagnosis then requires histologic correlation.
Ultrasonography
Findings
Sonography has a limited role in the evaluation of CNS dermoid tumors. In young children, subgaleal dermoid cyst of the anterior fontanelle has been assessed by sonography.
Angiography
Findings
Angiography is seldom used in the study of dermoid and epidermoid tumors. A dermoid tumor is an avascular mass on angiography. Displacement or encasement of blood vessels adjacent to the tumor may be well demonstrated by angiography.
Intervention
The treatment goal for dermoid and epidermoid tumors is complete surgical excision.[6,7 ]Resectability depends on the location of the tumor, as well as on the extent of the tumor's encroachment and on its inflammatory attachment to adjacent blood vessels and nerves.
Scalp tumors and intradiploic tumors of the skull are easier to excise completely than are intracranial tumors. Chemical meningitis may occur during removal of the dermoid or epidermoid tumor if its contents spill into the subarachnoid or ventricular spaces.
Chemotherapy and radiation therapy are not useful in the management of these tumors.
Patient Education:
For excellent patient education resources, visit eMedicine's Procedures Center. See also eMedicine's patient education article Dermoid Cyst Removal.
Multimedia
Media file 1: Elderly woman with chronic headaches. A nonenhanced computed tomography (CT) scan of the head demonstrates a well-circumscribed, cystic, low-attenuating lesion located at the cranial midline in the suprasellar region, posterior to the third ventricle. A small focus of calcification is noted at the posterior margin of the tumor.
Media file 2: The suprasellar lesion (same patient as in the image above) is hypointense on a subsequent axial T1-weighted image. The crescentic posterior rim of hyperintensity represents the fat chemical–shift artifact.
Media file 3: Gadolinium-enhanced axial T1-weighted image demonstrating nodular focus of enhancement in the right side of the suprasellar lesion (same patient as in the above 2 images).
Media file 4: Axial T2-weighted fast spin-echo magnetic resonance image demonstrating a hyperintense cystic component in the lesion (same patient as in the above 3 images).
Media file 5: Coronal computed tomography (CT) scan of the paranasal sinuses in a 26-year-old man with sinusitis. A large, well-circumscribed, low-attenuating, cystic lesion is present in the right temporal lobe, lateral to the cranial midline. Note the peripheral, marginal calcification in the lesion. No erosion is seen in the adjacent bone of the sella.
Media file 6: Contrast-enhanced axial computed tomography (CT) scan of the same lesion as in the above image shows partial marginal enhancement. The attenuation measurements in the center of the lesion are consistent with fat.
Media file 7: Axial gadolinium-enhanced T1-weighted image of a lesion demonstrating a hyperintense signal. In addition, multiple small foci of hyperintense signal are present along the sulci of the right temporal lobe. These represent fat droplets in the subarachnoid space, left by the focal rupture of the dermoid tumor.
Media file 8: The dermoid tumor is hyperintense on this gadolinium-enhanced coronal T1-weighted image. Note the heterogeneity of the lesion posteriorly. The hyperintensity results not from the gadolinium contrast enhancement but instead from the short T1 of fat. Multiple hyperintense foci consistent with fat droplets are demonstrated in the subarachnoid spaces. A mild midline septal shift to the left is noted; this is due to compression of the right lateral ventricle by the dermoid tumor. A chemical-shift artifact is also noted at the superior marginal surface of the lesion.
Media file 9: Sagittal T1-weighted image of the dermoid lesion again demonstrates hyperintensity consistent with fat content.
Media file 10: This epidermoid tumor is isointense relative to cerebrospinal fluid (CSF) on a nonenhanced T1-weighted axial image. The lobulated extra-axial mass surrounds the right cerebral peduncle and extends to the suprasellar region and the interpeduncular cistern. In contrast, a dermoid tumor will demonstrate a high T1 signal intensity because it contains fat constituents.
Media file 11: Epidermoid tumor (same as in the image above) demonstrating no enhancement in this contrast-enhanced T1-weighted image.
Media file 12: T2-weighted axial image demonstrating a hyperintense signal (in the same epidermoid tumor as in the above 2 images) that is similar to the signal intensity of cerebrospinal fluid (CSF). Compression by the epidermoid tumor mass has widened the interpeduncular cistern and narrowed the right cerebral peduncle.
Media file 13: Coronal T1-weighted image demonstrating a hypointense epidermoid tumor (same tumor as in the above 3 images). Note that the epidermoid has higher signal intensity than the adjacent CSF. There is a compressive mass effect on the third ventricle, but hydrocephalus is minimal.
Media file 14: Sagittal T1-weighted image demonstrating the suprasellar, prepontine, and interpeduncular cistern location of an epidermoid tumor.
References
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Keywords
dermoid tumor, dermoid, dermoid cyst, epidermoid, brain cyst, inclusion cyst, epidermoid cyst, dermoid cysts, dermoid cyst pictures, epidermoid tumor, inclusion cysts
Contributor Information and Disclosures
Author
Conway Lien, MD, Consulting Staff, Department of Radiology, Santa Clara Valley Medical Center
Conway Lien, MD is a member of the following medical societies: Radiological Society of North America
Disclosure: Nothing to disclose.
Coauthor(s)
Mahesh R Patel, MD, Chief, MRI, Department of Diagnostic Imaging, Santa Clara Valley Medial Center
Mahesh R Patel, MD is a member of the following medical societies: American Roentgen Ray Society, American Society of Neuroradiology, and Radiological Society of North America
Disclosure: Nothing to disclose.
Medical Editor
Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR, Professor Emeritus of Radiology, Professor of Clinical Radiology, Louisiana State University Health Sciences Center, New Orleans; Clinical Professor of Radiology, Tulane University School of Medicine; Active Staff, Department of Radiology, University Hospital
Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, American Society of Spine Radiology, Louisiana State Medical Society, Orleans Parish Medical Society, Radiological Society of North America, Royal College of Physicians and Surgeons of Canada, Royal College of Radiologists, and Royal Society of Medicine
Disclosure: Nothing to disclose.
Pharmacy Editor
Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.
CME Editor
Robert M Krasny, MD, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.
Chief Editor
James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics, Chairman, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences
James G Smirniotopoulos, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Head and Neck Radiology, American Society of Neuroradiology, American Society of Pediatric Neuroradiology, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.