CNS Dermoid Tumor (Cyst) Imaging
Updated: May 21, 2020
Author: Conway Lien, MD; Chief Editor: James G Smirniotopoulos, MD
Practice Essentials
Dermoid tumors are not true neoplasms but are inclusion cysts composed of ectodermal elements. They are uncommon, usually benign lesions, accounting for approximately 0.3% of all brain tumors and occur 4-10 times less frequently than do epidermoid tumors. Dermoid tumors are often discussed with epidermoid tumors because of their similar appearance and developmental origin.[1, 2, 3]
Dermoid cysts typically appear as nonenhancing low-density masses on CT scan and are hyperintense on T1-weighted MRI sequences with variable signal on T2-weighted sequences.[4]
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.[5] CT can show the location and content of the mass, as well as its relationship to the surrounding structures and their condition, while also allowing the physician to confirm intracranial extension indirectly.[6, 4]
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.[5] 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.[1, 2, 7, 8, 9, 10, 11, 12, 13, 14, 14]
Although ultrasonography 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 this modality.[15]
A dermoid tumor is an avascular mass on angiography; thus, angiography is seldom used in the study of dermoid and epidermoid tumors. However, displacement or encasement of blood vessels adjacent to the tumor may be well demonstrated by angiography (ie, MRA or CTA).
(See the images below.)
The dermoid tumor is hyperintense on this gadolinium-enhanced coronal T1-weighted magnetic resonance 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.
Sagittal T1-weighted image of the dermoid lesion in the same patient as the previous image again demonstrates hyperintensity consistent with fat content.
This epidermoid tumor is isointense relative to cerebrospinal fluid 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 patient as in the previous image) demonstrating no enhancement in this contrast-enhanced T1-weighted image.
Intracranial dermoid tumors most often present as headaches and visual disturbances. They are found in the anterior, middle, and posterior cranial fossae at similar frequencies but with clear predilections for the Sylvian fissure, sellar region, and cerebellar vermis. Outcomes following surgical excision are generally favorable.[16]
Rupture of an intracranial dermoid cyst is a rare event with considerable associated morbidity and potential mortality. Rupture is generally spontaneous, but in some cases, it can occur as a result of head trauma or surgery. When dermoid cystic tumors rupture, their contents spread into the ventricles and subarachnoid and/or subdural space. The clinical symptoms of acute rupture include headache, seizures, nausea, vomiting, vertigo, vision problems, aseptic chemical meningitis, hemiplegia, hydrocephalus, vasospasm, cerebral ischemia, mental changes, and coma.[17, 12, 13, 14]
In a study of 9 patients with ruptured intracranial dermoids, most patients presented with either headache or seizures. Two patients had hydrocephalus that required shunts. Characteristic radiologic features included fat droplets in subarachnoid spaces and hypointensity on susceptibility-weighted-Imaging with chemical shift artifact.[13]
Radiography
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.[18]
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
CT scanning is useful in the initial diagnosis of central nervous system (CNS) dermoid tumors if the typical findings are present. 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 Hounsfield units (HU) because of its fat content. The tumor may appear slightly heterogeneous because of additional ectodermal elements, including hair follicles, sebaceous glands, and sweat glands. Calcifications are frequent in the wall of the tumor. 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.[7, 19, 20, 21] MRI may be performed to further localize the lesion and to identify any involvement of adjacent structures.
A nonenhanced computed tomography scan of the head from an elderly woman with chronic headaches. This image 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 scan of the paranasal sinuses from 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-enhanced axial computed tomography 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.
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.[22, 23] Fat droplets in the ventricular or subarachnoid spaces strongly suggest rupture of a dermoid tumor.
In a study of 9 patients with ruptured intracranial dermoids, most patients presented with either headache or seizures. Two patients had hydrocephalus that required shunts. Characteristic radiologic features included fat droplets in subarachnoid spaces and hypointensity on susceptibility-weighted-Imaging with chemical shift artifact.[13]
Dermoid tumors located in the fourth ventricle do not often cause obstructive hydrocephalus. The differential diagnosis includes tumors that commonly cause hydrocephalus, such as ependymomas, medulloblastomas, hemangioblastomas, or cystic astrocytomas of the fourth ventricle.
Epidermoid tumors often have attenuation similar to that of cerebrospinal fluid (CSF), but these lesions 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.
Magnetic Resonance Imaging
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.
Most dermoid tumors have signal intensity characteristics similar to those of 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 because of 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.[24, 12, 13, 14]
In a study of 9 patients with ruptured intracranial dermoids, most patients presented with either headache or seizures. Two patients had hydrocephalus that required shunts. Characteristic radiologic features included fat droplets in subarachnoid spaces and hypointensity on susceptibility-weighted-Imaging with chemical shift artifact.[13]
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 magnetic resonance 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).[25, 26]
(See the images below.)
This epidermoid tumor is isointense relative to cerebrospinal fluid 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 patient as in the previous image) 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 previous image) that is similar to the signal intensity of cerebrospinal fluid. 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 previous image). Note that the epidermoid has higher signal intensity than the adjacent cerebrospinal fluid. 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.[27, 28] 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 MRIs. FLAIR sequences frequently demonstrate a heterogeneously increased signal intensity in epidermoid tumors as compared to that in arachnoid cysts. Diffusion-weighted imaging shows definitive high signal intensity (whiteness) in epidermoid tumors and low signal intensity (blackness) in arachnoid cysts.
Orakcioglu et al reviewed the charts of 5 men and 2 women with intracranial dermoid cysts and found that diffusion-weighted imaging 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.[3] 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.[3]
A study by Jolapara et al indicated that diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) can be used together to analyze the microstructural anatomy of epidermoid tumors.[29] The investigators found that the epidermoid tumors demonstrated high fractional anisotropy (FA) but, according to the directionally averaged mean diffusivity (Dav) and exponential apparent diffusion coefficient (eADC) values, no indication of diffusion restriction. Diffusion tensor mode values were close to -1, and planar anisotropy (CP) values within the tumor were high.[29]
Similar results were obtained by Santhosh et al in a DTI/DTM analysis in 3 patients with epidermoid cysts. 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 linear anisotropy (CL) values were lower than those obtained for the white matter in various regions.[30]
Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). 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.
Author
Conway Lien, MD Consulting Staff, Department of Radiology, Santa Clara Valley Medical Center; Vice Chairman, Department of Radiology, San Jose Regional Medical Center
Conway Lien, MD is a member of the following medical societies: American College of Radiology, American Society of Neuroradiology, Radiological Society of North America
Disclosure: Nothing to disclose.
Coauthor(s)
Mahesh R Patel, MD Chief of MRI and Staff Neuroradiologist, Department of Radiology, Santa Clara Valley Medical Center
Mahesh R Patel, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, Radiological Society of North America
Disclosure: Nothing to disclose.
Specialty Editor Board
Bernard D Coombs, MB, ChB, PhD Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.
Chief Editor
James G Smirniotopoulos, MD Chief Editor, MedPix®, Lister Hill National Center for Biomedical Communications, US National Library of Medicine; Professorial Lecturer, Department of Radiology, George Washington University School of Medicine and Health Sciences
James G Smirniotopoulos, MD is a member of the following medical societies: American College of Radiology, American Society of Neuroradiology, Radiological Society of North America
Disclosure: Nothing to disclose.
Additional Contributors
Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR Professor Emeritus of Radiology, Louisiana State University Health Sciences Center, New Orleans; Clinical Professor of Radiology, Tulane University School of Medicine
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, Louisiana State Medical Society, Radiological Society of North America, Royal College of Physicians and Surgeons of Canada, Royal College of Radiologists, Royal Society of Medicine, Orleans Parish Medical Society, American Society of Spine Radiology, American Society of Functional Neuroradiology, Southern Radiology Conference
Disclosure: Nothing to disclose.
Fanous AA, Gupta P, Li V. Analysis of the growth pattern of a dermoid cyst. J Neurosurg Pediatr. 2014 Dec. 14 (6):621-5. [QxMD MEDLINE Link].
Lynch JC, Aversa A, Pereira C, Nogueira J, Gonçalves M, Lopes H. Surgical strategy for intracranial dermoid and epidermoid tumors: An experience with 33 Patients. Surg Neurol Int. 2014. 5:163. [QxMD MEDLINE Link].
Orakcioglu B, Halatsch ME, Fortunati M, Unterberg A, Yonekawa Y. Intracranial dermoid cysts: variations of radiological and clinical features. Acta Neurochir (Wien). 2008 Dec. 150(12):1227-34; discussion 1234. [QxMD MEDLINE Link].
Kumaran SP, Srinivasa R, Ghosal N. Unusual Radiological Presentation of Intracranial Dermoid Cyst: A Case Series. Asian J Neurosurg. 2019 Jan-Mar. 14 (1):269-271. [QxMD MEDLINE Link].
Osborn AG. Diagnostic Neuroradiology. St Louis, Mo: Mosby-Year Book; 1994. 631-7.
Choi JS, Bae YC, Lee JW, Kang GB. Dermoid cysts: Epidemiology and diagnostic approach based on clinical experiences. Arch Plast Surg. 2018 Nov. 45 (6):512-516. [QxMD MEDLINE Link].
Calabrò F, Capellini C, Jinkins JR. Rupture of spinal dermoid tumors with spread of fatty droplets in the cerebrospinal fluid pathways. Neuroradiology. 2000 Aug. 42(8):572-9. [QxMD MEDLINE Link].
Ernemann U, Rieger J, Tatagiba M, et al. An MRI view of a ruptured dermoid cyst. Neurology. 2006 Jan 24. 66(2):270. [QxMD MEDLINE Link].
Messori A, Polonara G, Serio A, et al. Expanding experience with spontaneous dermoid rupture in the MRI era: diagnosis and follow-up. Eur J Radiol. 2002 Jul. 43(1):19-27. [QxMD MEDLINE Link].
Girishan S, Rajshekhar V. Rapid-onset paraparesis and quadriparesis in patients with intramedullary spinal dermoid cysts: report of 10 cases. J Neurosurg Pediatr. 2015 Oct 2. 1-8. [QxMD MEDLINE Link].
Garg K, Kumar R. Isolated central canal rupture of spinal dermoid. Report of 3 cases. J Neurosurg Spine. 2014 Sep. 21 (3):361-6. [QxMD MEDLINE Link].
Ramdasi R, Thorve S, Karnavat C. Explosion of dermoid cyst into five intracranial spaces- a rare event. Br J Neurosurg. 2019 Nov 12. 1-2. [QxMD MEDLINE Link].
Shashidhar A, Sadashiva N, Prabhuraj AR, Narasingha Rao K, Tiwari S, Saini J, et al. Ruptured intracranial dermoid cysts: A retrospective institutional review. J Clin Neurosci. 2019 Sep. 67:172-177. [QxMD MEDLINE Link].
Jacków J, Tse G, Martin A, Sąsiadek M, Romanowski C. Ruptured intracranial dermoid cysts: a pictorial review. Pol J Radiol. 2018. 83:e465-e470. [QxMD MEDLINE Link].
Stannard MW, Currarino G. Subgaleal dermoid cyst of the anterior fontanelle: diagnosis with sonography. AJNR Am J Neuroradiol. 1990 Mar-Apr. 11(2):349-52. [QxMD MEDLINE Link].
Chung LK, Lagman C, Duong C, Nagasawa DT, Tucker AM, Yong WH, et al. Dermoid Cyst of the Prepontine Cistern and Meckel's Cave: Illustrative Case and Systematic Review. J Neurol Surg B Skull Base. 2018 Apr. 79 (2):139-150. [QxMD MEDLINE Link]. [Full Text].
Ak R, Doğanay F, Doğan M. Rare cause of seizures: ruptured intracranial dermoid cyst. Clin Exp Emerg Med. 2019 Mar. 6 (1):89-90. [QxMD MEDLINE Link]. [Full Text].
Wang X, Gao J, Wang T, Li Z, Li Y. Intraspinal dermoid and epidermoid cysts: Long-term outcome and risk factors. J Spinal Cord Med. 2018 Dec 5. 1-6. [QxMD MEDLINE Link].
Roeder MB, Bazan C, Jinkins JR. Ruptured spinal dermoid cyst with chemical arachnoiditis and disseminated intracranial lipid droplets. Neuroradiology. 1995 Feb. 37(2):146-7. [QxMD MEDLINE Link].
Smith AS, Benson JE, Blaser SI, et al. Diagnosis of ruptured intracranial dermoid cyst: value of MR over CT. AJNR Am J Neuroradiol. 1991 Jan-Feb. 12(1):175-80. [QxMD MEDLINE Link].
Wilms G, Casselman J, Demaerel P, et al. CT and MRI of ruptured intracranial dermoids. Neuroradiology. 1991. 33(2):149-51. [QxMD MEDLINE Link].
Gao PY, Osborn AG, Smirniotopoulos JG, et al. Radiologic-pathologic correlation. Epidermoid tumor of the cerebellopontine angle. AJNR Am J Neuroradiol. 1992 May-Jun. 13(3):863-72. [QxMD MEDLINE Link].
Smirniotopoulos JG, Chiechi MV. Teratomas, dermoids, and epidermoids of the head and neck. Radiographics. 1995 Nov. 15(6):1437-55. [QxMD MEDLINE Link].
Fanous AA, Gupta P, Li V. Analysis of the growth pattern of a dermoid cyst. J Neurosurg Pediatr. 2014 Dec. 14 (6):621-5. [QxMD MEDLINE Link].
Kallmes DF, Provenzale JM, Cloft HJ, et al. Typical and atypical MR imaging features of intracranial epidermoid tumors. AJR Am J Roentgenol. 1997 Sep. 169(3):883-7. [QxMD MEDLINE Link].
Tampieri D, Melanson D, Ethier R. MR imaging of epidermoid cysts. AJNR Am J Neuroradiol. 1989 Mar-Apr. 10(2):351-6. [QxMD MEDLINE Link].
Chen S, Ikawa F, Kurisu K, et al. Quantitative MR evaluation of intracranial epidermoid tumors by fast fluid-attenuated inversion recovery imaging and echo-planar diffusion-weighted imaging. AJNR Am J Neuroradiol. 2001 Jun-Jul. 22(6):1089-96. [QxMD MEDLINE Link]. [Full Text].
Dutt SN, Mirza S, Chavda SV. Radiologic differentiation of intracranial epidermoids from arachnoid cysts. Otol Neurotol. 2002 Jan. 23(1):84-92. [QxMD MEDLINE Link].
Jolapara M, Kesavadas C, Radhakrishnan VV, et al. Diffusion tensor mode in imaging of intracranial epidermoid cysts: one step ahead of fractional anisotropy. Neuroradiology. 2009 Feb. 51(2):123-9. [QxMD MEDLINE Link].
Santhosh K, Thomas B, Radhakrishnan VV, et al. Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts. J Magn Reson Imaging. 2009 Apr. 29(4):967-70. [QxMD MEDLINE Link].
Brown JY, Morokoff AP, Mitchell PJ, et al. Unusual imaging appearance of an intracranial dermoid cyst. AJNR Am J Neuroradiol. Dec 2001. 22(10):1970-2. [QxMD MEDLINE Link]. [Full Text].