British Journal of Radiology (2006) 79, 167-169
© 2006 British Institute of Radiology
doi: 10.1259/bjr/17232685
Ruptured spinal dermoid cyst with disseminated intracranial fat droplets
J G Cha, MD,
S-H Paik, MD,
J-S Park, MD,
S-J Park, MD,
D-H Kim, MD and
H-K Lee, MD
Department of Radiology, Soonchunhyang University Bucheon Hospital, 1174, Jung-dong, Wonmi-gu, Bucheon-St Gyeonggi-do, 420-021, Republic of Korea
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Abstract
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Fat droplets in the cerebrospinal fluid (CSF) is a well-known complication of ruptured intracranial dermoid tumours. We report an unusual case of a ruptured spinal dermoid tumour. MR images showed a tethered spinal cord and an intramedullary fat-containing mass. Fat droplets were revealed in the ventricles and the cisternal spaces on brain CT and brain MR. In the English literature, a ruptured spinal dermoid tumour accompanying a tethered spinal cord is extremely rare.
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Introduction
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Intraspinal dermoid tumours are rare benign, slow-growing tumours and tend to extend to the subarachnoid space. Dermoid tumours comprise 1.1% of intraspinal tumours [1]. There is no communication between the cyst and the subarachnoid space. Several causes including spontaneous, iatrogenic or traumatic rupture have been reported to result in dissemination of lipid material from the dermoid tumours into the subarachnoid space or ventricles. We report a case of spontaneously ruptured spinal dermoid tumour with disseminated intracranial fat droplets and tethered cord.
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Case report
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A 44-year-old man presented with a history of voiding difficulty starting 10 years ago and exacerbation 3 months prior to admission. There was no history of lumbar puncture or major operation. Physical examination revealed radiating pain down left S2 dermatome level (hyperaesthesia). Laboratory findings were normal. The patient underwent MRI of the spine using a 1.5 T scanner. T1 weighted (660/10/4 [repetition time/echo time/excitation]) (Figure 1a
) and T2 weighted (4000/123/4 [repetition time/echo time/excitation]) (Figure1b) images showed a hyperintense intramedullary mass at the level of L3–L5 and tethered cord. Brain CT (Figure 1c) and brain MR (4000/9/4 [repetition time/echo time/excitation]) (Figure 1d) demonstrated multiple small fat droplets in the intraventricular and cisternal space suggesting rupture of spinal dermoid cyst. The patient underwent a laminectomy from L2 to L5.
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Figure 1. (a) Sagittal T1 weighted (repetition time (TR) 660/echo time (TE) 10) spin-echo image demonstrates central hypointense and peripheral hyperintense intramedullary mass at the level of L3–L5 and tethered spinal cord. (b) Sagittal T2 weighted (TR 4000/TE 123) spin-echo image shows homogeneous hyperintense mass. (c) Brain CT shows fat droplets in both frontal and lateral ventricles and cisternal spaces. (d) Axial T1 weighted (TR 400/TE 9) revealed hyperintense lipid materials in left frontal and both lateral ventricles, and subarachnoid space.
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Discussion
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Spinal dermoids are dysontogenetic tumours arising from inclusion of ectopic embryonic rests of the ectoderm within the spinal canal at the time of neural tube closure between the third and the fifth week of embryonic development [2]. Dermoid tumours show a slight male predominance, and most dermoid tumours are revealed during the second and third decades. Dermoid tumours may be related to bony malformations, myelomeningocele [3], hypertrichosis and/or a dermal sinus tract. The lumbosacral region is most common site (60%) involving the cauda equina and the cornus medullaris followed by the upper thoracic (10%) and cervical (5%) regions [4]. They have a thick wall covered with stratified squamous epithelium containing dermal appendages such as hair, sebaceous glands, sweat glands and hair follicle and less commonly, teeth and nails [5]. Dermoid tumours commonly have areas of calcification. The relatively high signal from fat on MRI, especially the bright signal on T1 weighted images, makes identification of lipid droplets easy, particularly within the cerebral sulci, fissures, the perimedullary subarachnoid space and the central canal of the spinal cord. MRI has also shown more frequent asymptomatic spillage of lipid material [6].
Dermoid tumours may have two distinct portions, a lipid one and a more solid or more fluid one [4] as in our case, showing fat tissue in peripheral portion of the tumour and fluid content in the central portion. In addition, especially with leakage of lipid material, the use of intravenous contrast medium makes diagnosis of a meningeal inflammation easier.
Although dermoid tumours develop from the embryonic period, symptoms may not occur until adulthood due to their slow growth [1], symptoms and signs secondary to the space-occupying lesion are location-dependent and are due to the irritative effect on and/or compression of the adjacent structures. When accompanied by a tethered cord, particularly with small lesions, neurological symptoms can be elicited without mass effect.
Once rupture of the cyst occurs acute symptoms relate to chemical or aseptic meningitis [3], headache or seizures may be developed due to dissemination of lipid droplets in the cerebrospinal fluid (CSF) pathways. Lumbar arachnoiditis may be developed as a result of leakage of fat and proteinaceous material into the subarachnoid space. The highly irritative lipid content of dermoid tumours may cause severe inflammatory response, though spread of fat into the CSF may also be clinically silent [7].
After rupture of dermoid tumour occurs, lipid droplets float in the CSF and are passively conveyed by CSF movement. It can therefore spread throughout the subarachnoid space and ventricular system. Scearce et al [8] insisted that fat droplets reach the ventricles from the perimedullary subarachnoid space by retrograde flow through the foramina of Luschka and Magendie. To our knowledge, few cases of rupture of dermoid spinal tumours have been reported [8–12].
In conclusion, MRI is not only helpful in detecting intraspinal dermoid tumours and the fat droplets in CSF space even in an asymptomatic case of rupture of the tumour, but also diagnosing the associated congenital anomalies such as tethered cord, as is seen in our case.
Received for publication February 25, 2005.
Revision received May 6, 2005.
Accepted for publication May 6, 2005.
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References
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Abstract
Introduction
