J Neurosurg 92:711–714, 2000
Magnetic resonance appearance of multiple intracranial epidermoid cysts: intrathecal seeding of the cysts? Case report YASUSHI MIYAGI, M.D., PH.D., SATOSHI O. SUZUKI, M.D., PH.D., TORU IWAKI, M.D., PH.D., KATSUYA ISHIDO, M.D., PH.D., TAKEHISA ARAKI, M.D., PH.D., AND KAZUFUMI KAMIKASEDA, M.D., PH.D. Departments of Neurosurgery and Neurology, Kaizuka Hospital; and Department of Neuropathology and Neurological Institute, Faculty of Medicine, Kyushu University, Fukuoka, Japan A 44-year-old man presented to the hospital with multiple intracranial epidermoid cysts. The clinical manifestations of his disease included chronic headaches and one seizurelike episode. Findings determined by magnetic resonance (MR) imaging, surgery, and histological analysis indicated intrathecal and intraventricular seeding of the cysts. Spontaneous (nontraumatic) seeding of multiple daughter cysts from intracranial epidermoid cysts is still very rare and their multiple appearances on MR imaging should be distinguished from the simple scattering of oily contents due to cyst rupture.
KEY WORDS • multiple epidermoid cyst • dissemination
LTHOUGH there has been an increase in the number of reports in which MR imaging has documented multiple appearances of cyst contents scattered from ruptured epidermoid cysts,15 the occurrence of multiple intracranial epidermoid cysts is still very rare. Although the cause of multiple intracranial congenital tumors is not clear,9 some authors have reported pathological and/or radiological evidence that strongly suggests intrathecal dissemination of epidermoid cysts.6,7 Neurological diagnoses of such multiple fatty lesions are complicated by the possibility that they are ruptured epidermoid or dermoid cysts or multiple lipomas. To our knowledge, in this report we present the first MR imaging evidence of spontaneous intrathecal dissemination and seeding of multiple intracranial epidermoid cysts, confirming histological findings.
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Case Report History. This 44-year-old man was admitted to our hospital with an initial diagnosis of a brain tumor. He reported a 20-year history of gradually worsening headaches for which he regularly ingested 2640 mg acetylsalicylic acid per day, although he had refused to undergo an examinaAbbreviations used in this paper: CSF = cerebrospinal fluid; CT = computerized tomography; IQ = intelligence quotient; MR = magnetic resonance.
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tion. Two weeks before admission, he also experienced a single episode mimicking a generalized seizure. Examination. At admission, the patient was alert and had no complaints of neurological deficit, neck stiffness, or cutaneous lesions. His IQ was slightly low (verbal IQ 84, performance IQ 67, full-scale IQ 74). Laboratory tests showed that his tumor markers were within normal limits (CA19-9 10 U/ml, -fetoprotein 9.4 ng/ml, and carcinoembryonic antigen 1 ng/ml). The patient’s CSF contained no atypical cells and appeared normal. Electroencephalography measured no epileptic discharges, but revealed slow low-amplitude activity in the left frontal region. Computerized tomography scanning demonstrated a well-defined lobulated mass exhibiting homogeneous low density in the left frontal lobe, adjacent to the frontal skull base and the floor of the anterior horn of the lateral ventricle. Multiple nodular lesions with similar densities were also observed along the choroid plexus of the lateral ventricle. These homogeneous and extremely low density lesions suggested the presence of fat or oil within the cysts (100 to 40 Hounsfield units). An osteolytic change was also observed around the left anterior clinoid process, but the cysts did not extend to either the ethmoid or sphenoid sinus. Magnetic resonance imaging confirmed the presence of a primary lobulated mass lesion in the left frontal lobe adjacent to the frontal skull base (Fig. 1), and the ventricular system appeared mildly enlarged. The masses demonstrated homogeneously high signal intensity during both T1- and T2-weighted MR sequences, and 711
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FIG. 1. Preoperative plain MR images. A: Coronal section revealing multiple and lobulated oillike intensities in the left frontal lobe and their extension to the epidural skull base. B: Axial section revealing small lesions along the choroid plexus of the lateral ventricles. C: Sagittal section demonstrating multiple small lesions adjacent to the dura mater of the frontal skull base.
no perifocal edema was detected on the T2-weighted sequence. Multiple nodular lesions that were attached to the choroid plexus of the lateral ventricle did not move when the patient was moved from the supine to prone position.
FIG. 2. Intraoperative photographs showing many small cystic lesions (arrows) attached to the inner surface of the dura mater of the reflected dural flap (upper) and the skull base (lower).
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These neuroradiological studies led us to a preoperative diagnosis of multiple epidermoid or dermoid cysts or lipomas. Magnetic resonance imaging detected no associated lesion in the spinal canal. Operation. The patient underwent a left frontal craniotomy. When the dural flap was incised and reflected, multiple small cystic lesions were found on the inner surface of the frontal convexity dura mater as well as on the frontal fossa dura mater (Fig. 2). These convexity lesions had not been detected on any preoperative MR image. The diameters of the cystic lesions ranged from 2 to 5 mm. Each lesion displayed a homogeneous color, with different lesions ranging from golden yellow to white. The arachnoid membrane on the left frontal cortex was turbid and thick, suggesting chronic arachnoiditis. The large, lobulated cystic mass lesion in the left frontal lobe was resected via transcortical and subfrontal approaches. White waxy flakes filled the cyst walls. Although the contents of the cysts were completely removed, the cyst walls could not be completely resected because they extended deep under the skull base. As many dural lesions as possible were removed; however, the intraventricular lesions detected by preoperative MR imaging were not investigated. Pathological Findings. Histopathological analysis revealed that the multiple small cystic lesions were attached to dura mater (Fig. 3) or embedded in cerebral tissue. Well-differentiated and stratified squamous epithelial cells without any cutaneous appendages focally lined the cyst walls; flaky, keratinous debris occupied the lumen. Although these findings were consistent with those indicating an epidermoid cyst, the majority of the cyst walls lacked epithelial linings. There were signs of chronic inflammatory reactions against degenerative debris with cholesterol clefts, such as infiltration of lipid-laden macrophages and multinucleated giant cells, as well as calcification. There was no malignant tissue. Postoperative Course. Postoperatively, the patient experienced a headache and loss of appetite. Three weeks postoperatively, enlarged ventricles with periventricular lucency were observed on CT scanning, suggesting a J. Neurosurg. / Volume 92 / April, 2000
Intrathecal dissemination of epidermoid cyst
FIG. 3. Photomicrographs demonstrating the histopathological features of the multiple intracranial cysts. A: A 5.5 4.5–mm cyst is shown adhering to the convexity dura mater. B: A well-differentiated and stratified squamous epithelium is seen lining the cystic cavity. The inset shows a high-power-field view of the epithelium. C: The cyst shown in B is seen to contain flaky keratinous debris. D: Associated degenerative changes are shown. Arrows indicate foamy macrophages and arrowheads indicate small areas of calcification. H & E. Bar = 625 m (A), 200 m (B and C), and 100 m (D).
communicating hydrocephalus; this was successfully treated by inserting a ventriculoperitoneal shunt. The patient’s headaches dissipated and he continued to recover uneventfully without experiencing an epileptic seizure. He was discharged without any neurological deficits 2 weeks after the ventriculoperitoneal shunt was inserted. Discussion Multiple generations of epidermoid or dermoid cysts have been postulated to arise from incidental multiple epithelial components in the neural groove.9,11 However, it has also been well documented that epidermoid cysts in the nervous system can reproduce following experimental implantation of epithelial cells of the skin,14 trauma,13 or multiple lumbar punctures.2 Floating fatty globules have been observed during surgery for ruptured epidermoid or dermoid cysts.8,15 Smith, et al.,12 defined the “satellite lesions” that they observed during surgery as “adherent fat due to chronic inflammation.” The occurrence of multiple epidermoid cysts due to spontaneous (nontraumatic) intrathecal seeding is extremely rare. We could only find mention of these cysts in reports of two other cases, both of which were confirmed by autopsy.7,10 Because our patient J. Neurosurg. / Volume 92 / April, 2000
had experienced no head trauma or lumbar puncture, the dissemination of the epithelial clusters into the CSF could reasonably be explained as a result of asymptomatic ruptures or a spontaneous breakdown of the wall of the cyst located in the frontal lobe. In the present case, analysis of the specimen containing small cysts with dural attachment indicated that cyst formation took place after seeding of disseminated epithelial components onto the inner surface of the dura mater and was not due to chronic inflammation around fatty globules. In general, epidermoid cysts typically appear on CT scans as low-density areas similar to CSF.3 For this reason, cysts in subarachnoid spaces can sometimes be visualized only by metrizamide-enhanced CT cisternography.9 As observed in this case, multiple epidermoid cysts occasionally demonstrate extremely low density on CT scanning, similar to the fat density of a dermoid cyst or lipoma.7 Such atypical epidermoid lesions present as a high signal intensity on T1-weighted MR images and, therefore, forming a diagnosis of multiple fatty lesions (including dermoid and epidermoid tumors) or lipomas seems impossible without operative exploration or histological analysis. Because cyst mobility strongly indicates that the floating oil has spilled from ruptured epidermoid or dermoid 713
Y. Miyagi, et al. tumors8,12,15 and excludes the occurrence of multiple lipomas, the cyst mobility associated with changes in the patient’s position and the fluid level formation of the multiple fatty globules observed on CT or MR images are immensely important to determine during the preoperative neuroradiological study. Some cases of multiple epidermoid or dermoid cysts have demonstrated a distribution of fatty globules that is not dependent on gravity. Smith, et al.,12 have suggested that fat that is not gravity dependent is not merely trapped between sulci, implying that it is adherent. In the absence of histological findings, a similar CT or MR imaging appearance of multiple fat globules in intraventricular or subarachnoid spaces was interpreted as multiple lipomas.5 In contrast to lipomas, some epidermoid or dermoid cysts are reported to involve various complications, including malignant transformation, hemorrhage, chronic arachnoiditis, spontaneous cyst rupture followed by aseptic meningitis, vasospasm, and hydrocephalus.1,4 Great caution should therefore govern interpretation of multiple intracranial fatty lesions observed on CT or MR images. In the present case, the intraventricular lesions were not removed and histologically defined because opening the ventricles was deemed too invasive for the patient. The daughter cysts that were excised were found to be benign and would not have caused a severe problem for the patient. However, the daughter cysts might have caused minor problems such as chronic arachnoiditis, headache, hydrocephalus, or symptomatic epilepsy, as observed in our case. Therefore in our opinion, as long as there is no risk of surgical complication, such daughter cysts should be completely removed if possible. In summary, we have documented, for the first time, the MR imaging appearance and the operative findings of intrathecal dissemination of epidermoid cysts, confirmed by their histological characteristics. We also have stressed the complexity of the neuroradiological diagnosis of multiple fat-intensity lesions.
2. 3. 4. 5. 6.
7. 8. 9. 10. 11. 12. 13. 14. 15.
tions from an intracranial epidermoid cyst: case report and literature review. Neurosurgery 24:574–578, 1989 Choremis C, Economos D, Papadatos C, et al: Intraspinal epidermoid tumours (Cholesteatomas) in patients treated for tuberculous meningitis. Lancet 2:437–439, 1956 Davis KR, Roberson GH, Taveras JM, et al: Diagnosis of epidermoid tumor by computed tomography. Analysis and evaluation of findings. Radiology 119:347–353, 1976 Dubois PJ, Sage M, Luther JS, et al: Malignant change in an intracranial epidermoid cyst. J Comput Assist Tomogr 5: 433–435, 1981 Hädecke J, Buchfelder M, Triebel HJ, et al: Multiple intracranial lipoma: a case report. Neurosurg Rev 20:282–287, 1997 Hekster REM, Lambooy N: Multiple low (fat) attenuating lesions associated with an intracranial dermoid cyst: multiple dermoids or cyst rupture? A case report. Diagn Imaging 50: 229–231, 1981 Itoh T, Terai Y, Fujimoto S, et al: [Multiple intracranial epidermoid. Case report.] Neurol Med Chir 28:1203–1208, 1988 (Jpn) Laster DW, Moody DM, Ball MR: Epidermoid tumors with intraventricular and subarachnoid fat: report of two cases. AJR 128:504–507, 1986 Ogawa T, Sekino H, Fuse T, et al: [Multiple intracranial epidermoids located in the brain stem and the middle cranial fossa. Case report.] Neurol Med Chir 25:393–397, 1985 (Jpn) Olmstead EV: Multiple epidermoid cysts of the leptomeninges associated with a chromophobe adenoma of the pituitary. J Neuropathol Exp Neurol 11:329–334, 1952 Russell DS, Rubinstein LJ: Pathology of Tumours of the Nervous System, ed 5. London: Edward Arnold, 1989, pp 690–695 Smith AS, Benson JE, Blaser SI, et al: Diagnosis of ruptured intracranial dermoid cyst: value of MR over CT. AJNR 12: 175–180, 1991 Smith CML, Timperley WR: Multiple intraspinal and intracranial epidermoids and lipomata following gunshot injury. Neuropathol Appl Neurobiol 10:235–239, 1984 Van Gilder JC, Schwartz HG: Growth of dermoids from skin implants to the nervous system and surrounding spaces of the newborn rat. J Neurosurg 26:14–20, 1967 Yoshimoto K, Nishio S, Suzuki S, et al: Movable oil in the brain: intracranial ruptured dermoid tumors. Case illustration. J Neurosurg 86:734, 1997
Acknowledgments We thank Mrs. Lucia Griffin for her assistance and Dr. George T. Mandybur for his helpful comments regarding this manuscript. References 1. Abramson RC, Morawetz RB, Schlitt M: Multiple complica-
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Manuscript received May 24, 1999. Accepted in final form December 13, 1999. Address reprint requests to: Yasushi Miyagi, M.D., Ph.D., Department of Neurosurgery, University of Mississippi Medical Center, 2500 North State Street, Jackson, Mississippi 39216. email:
[email protected].
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