CASE 11148 Published on 25.07.2013

Conus medullaris dermoid cyst with intracranial fat dissemination

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Foram Gala; Tejas Gosalia; Kunal Gala; Darshana Paunipagar; Bharat Gala.

Lifescan Imaging Centre,
Mumbai, India;
Email:drgalab@gmail.com
Patient

34 years, male

Categories
Area of Interest Neuroradiology spine, Anatomy, Neuroradiology brain ; Imaging Technique MR, CT
Clinical History
34-year-old male patient presented with gradual bilateral lower limb weakness and stiffness for 2 years. He had been limping for 6 months with symptoms worsening in last 2 months. Right lower limb power was 3/5 and 2/5 left side; extensor plantars reflex; hyper-reflexia. Sensory examination and cranial nerves were intact.
Imaging Findings
MRI of spinal cord showed a solid and cystic heterogeneously enhancing lesion arising from conus and extending downwards expanding the lumbar canal. The lesion showed predominant fat component, which was hyperintense on T1- and T2W images and suppressed on fat saturated images. Minimal soft tissue component revealed heterogeneous appearance on T2W images. The lesion showed no enhancement on post contrast images. Except for kinking of conus, no significant oedema was noted in the conus or cord.
CT images showed small foci of calcification along the inferior aspect of the mass. The mass measured approximately 8.7 cm in cranio-caudal extent.
There was no evidence of spinal dysraphism.
CT examination of the brain showed tiny fat density droplets in lateral ventricle and cortical sulci suggestive of rupture of cyst and lipid dissemination in subarachnoid space.
Discussion
Dermoid cysts are rare benign slow growing lesions of the central nervous system. These constitute about 1.1 % of all spinal cord tumours [1]. These occur from inclusion of ectopic embryonic rests of the ectoderm at the time of neural tube closure between the third and fifth week of embryonic development [2]. The neural tube closes last in the lumbo-sacral region, there is more chance that the process of neurulation may be disturbed and nests of cutaneous tissue may get trapped within the developing tube, giving rise to dermoid cyst. Hence intraspinal dermoid cysts are usually located in lumboscaral region involving conus (60%) followed by upper thoracic regions (10%) and cervical regions (5%).

Dermoid cysts are usually associated with congenital spinal dysraphisms like myelomeningocele, hypertrichosis, tethered cord and dermal sinus tracts [3].
Though they are congenital in origin, they present in 2nd or 3rd decade with slight male predominance. They are slow growing and reach large sizes at the time of presentation.
Symptoms are variable and depend on the size and location of tumour.
Commonly it presents with motor or sensory disturbances, backache and urological complaints. However if ruptures acutely, headache, vomiting, vertigo, aseptic meningitis, mental changes may be the presenting symptoms (4). A dermoid cyst can rupture during surgery, after a trauma or spontanenously.
Imaging appearance of dermoids is extremely heterogenous due to composite mixture of fat, calcium, soft tissue and fluid contents. CT is very useful in demonstrating fat and calcification. Fat is clearly demonstrated on MRI. Screening of entire spine and brain is done to look for dissemination of lipid droplets in subarachnoid space, suggestive of rupture.
Histopathological findings are classic for dermoid cyst with thick fibro-collagenous cyst wall lined by stratified squamous epithelium containing dermal appendages like hair, sebaceous glands, sweat glands and less commonly, teeth and nails. The presence of these dermal appendages differentiates dermoid from epidermoid cysts, which lack these structures [5].
Management consists of excision of the dermoid cyst as completely as possible. However if the wall of the lesion is densely adherent to cord, near total excision in such cases is acceptable.
Differential diagnosis include lipoma, epidermoid cysts, and intraaxial spinal cord tumours such as ependymomas, astrocytomas, and haemangioblastomas. Lipomas are homogenous with only fat content while epidermoid cysts usually are non-enhancing with CSF signal intensity and show restricted diffusion. Ependymomas, astrocytomas, and haemangioblastomas are usually associated with peritumoural cysts, significant cord oedema and enhancement.
Differential Diagnosis List
Ruptured conus dermoid cyst with intracranial fat dissemination
Spinal cord epidermoid cyst
Spinal cord lipoma
Final Diagnosis
Ruptured conus dermoid cyst with intracranial fat dissemination
Case information
URL: https://www.eurorad.org/case/11148
DOI: 10.1594/EURORAD/CASE.11148
ISSN: 1563-4086