British Journal of Radiology 75 (2002),709-710 © 2002 The British Institute of Radiology
An unusual cause of epilepsy and mental deterioration
M van der Graaff, MD1 and
G Davies, MRCP, FRCR2
Department of 1 Neurology and 2 Radiology, St Lucas Andreas Hospital Amsterdam, PO Box 9243, 1006 AE, The Netherlands
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Introduction
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A previously well 51-year-old man presented 4 years ago with status epilepticus. CT (Figures 1 and 2
) was performed at that time. 2 years later he presented with another seizure, memory loss and slowing of thought. MRI was then performed (Figure 3). A year later he presented with severe headache, vomiting, unstable gait and urinary incontinence. His complaints subsided in 2 days. MRI was again performed (Figure 4).
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Figure 1. Initial CT scan. Reproduced with permission from Journal of Neurology, Neurosurgery and Psychiatry 1997;62:222.
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Figure 2. Initial CT scan. Reproduced with permission from Journal of Neurology, Neurosurgery and Psychiatry 1997;62:222.
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Figure 4. Second MR scan 1 year after Figure 3 . Reproduced with permission from Journal of Neurology, Neurosurgery and Psychiatry 1997;62:222.
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What does the CT (Figures 1 and 2) show? What is the cause of mental deterioration (Figure 3)? Why did the acute symptoms resolve (Figure 4)?
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Answer
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CT (Figure 1) showed a partially calcified right subfrontal tumour, consistent with a dermoid cyst, an intraventricular fat–fluid level (left) but also fixed fat (right frontal horn) (Figure 2). MRI 2 years later (Figure 3) showed marked hydrocephalus and fat in the aqueduct. The second MR scan (Figure 4) showed a flow void anterior to the fat in the aqueduct. The diagnosis was a ruptured dermoid cyst with progressive hydrocephalus due to obstruction of the aqueduct by fat, leading to mental deterioration. The spontaneous resolution is probably owing to temporary distension of the aqueduct caused by increased pressure in the lateral and third ventricle, manifested as a flow void on MRI (Figure 4). The patient initially refused surgery, but tumour debulking and ventriculoperitoneal drainage were eventually performed. Histology confirmed the diagnosis of adermoid cyst.
Intracranial dermoid cysts are rare congenital tumours and comprise 0.1–0.7% of intracranial tumours [1]. Dermoid cysts are ectodermal inclusion cysts containing cholesterol, keratinaceous debris and dermal appendages such as hair and sebaceous glands [2]. Tumour contents on CT are of low density and often contain fat. Calcification in the tumour is common, and there is no contrast enhancement. Intracranial dermoid cysts occasionally rupture spontaneously into the ventricles or intothe subarachnoid spaces. In such cases, intraventricular fat–fluid levels may be seen on CT or MRI[3]. Rupture of a dermoid cyst may be asymptomatic, or may lead to headache, focal neurological deficits, seizures or sterile meningitis [2,3]. The usual treatment of dermoids is surgery, asthese tumours tend to grow slowly. The prognosis of operated patients is generally good [4, 5]. Two mechanisms have been described for the development of hydrocephalus, the first being obstruction of the fourth ventricle or aqueduct by fat [6], as in our case. Larsson et al [7] postulate thatfat cannot be absorbed from the ventricles orfrom the subarachnoid space. However, in our case there was reduction in volume oftumour fat (Figures 5 and 6) over the years, suggesting that there is some sort ofabsorption. The second mechanism leading to hydrocephalus is the development of chemical meningitis due to irritation of the meninges by the contents of the dermoid cyst [8].
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Figure 5. Initial T1 weighted parasagittal MR image showing a marked amount of fixed fat in the right frontal horn.
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Figure 6. 2 years later. T1 weighted parasagittal MR image showing hydrocephalus and a reduction in the amount of fixed intraventricular fat in the right frontal horn compared with the initial scan (Figure 5).
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Received for publication November 30, 2000.
Accepted for publication April 17, 2001.
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References
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- Miller JD, editor. Northfield's surgery of the central nervous system (2nd edn). Oxford, UK: Blackwell, 1987:240–4.
- Smirniotopoulos JG, Chiechi MV. From the archives of the AFIP: teratomas, dermoids, and epidermoids of the head and neck. Radiographics 1995;15:1437–55.[Abstract]
- Smith AS, Benson JE, Blaser SE, Mizushima A, Tarr RW, Bellon EM. Diagnosis of ruptured intracranial dermoid cyst: value of MR over CT. Am J Neuroradiol 1991;12:175–80.[Abstract]
- Rubin G, Scienza R, Pasqualin A, Rosta L, Da Pian R. Craniocerebral epidermoids and dermoids, a review of 44 cases. Acta Neurochir (Wien) 1989;97:1–16.
- Bucciero A, del Basso de Caro ML, Carraturo S, Vizioli L, Cerillo A, Tedeschi G. Supratentorial dermoid cysts. Presentation and management of five cases. J Neurosurg Sci 1995;39:7–11.[Medline]
- Martin R, Krone A, Schuknecht B, Kuhn W. Rapid development of occlusion hydrocephalus by intraventricular fat possibly derived from a ruptured dermoid cyst. J Neurol Neurosurg Psychiatry 1989;52:134–5.
- Larsson EM, Brandt L, Holtas S. Persisting intraventricular fat–fluid levels following surgery on a ruptured dermoid cyst of the posterior fossa. Acta Radiologica 1987;28:489–90.[Medline]
- Jamjoom AB, Cummins BH. The diagnosis of ruptured intracranial dermoid cysts. B J Neurosurg 1989;3:609–12.[Medline]
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