Spinal dermoid cysts are uni or multilocular cystic tumors lined by squamous epithelium containing skin appendages (hair follicles, sweat glands, sebaceous glands) 6. They are congenital in origin.
Forty percent are intramedullary, and 60% are extramedullary 6.
This article specifically relates to spinal dermoid cysts. For a discussion of intracranial dermoid cysts refer to the article: intracranial dermoid cyst.
Spinal dermoid cysts are uncommon overall but account for nearly 20% of intradural tumors seen in patients younger than one year of age 2. They generally present in patients younger than 20 years. Males and females are affected equally 6.
May be associated with occult spinal dysraphism.
Spinal dermoid cysts are often asymptomatic and discovered incidentally. If symptomatic, motor disturbances, pain, sensory disturbances and bowel or bladder dysfunction may be present 4. They may become acutely symptomatic if rupture occurs 7.
Dermoid cysts are benign. They result from inclusion of epithelial tissue within the neural groove during embryonic development. Like epidermoid cysts, they have a lining of stratified squamous epithelial cells; unlike epidermoid cysts, they also contain sebaceous glands, sweat glands and hair follicles, which account for the fat intensity signal seen in these lesions. Unlike true neoplasms which grow by progressive cell division, dermoid cysts enlarge by desquamation of normal cells and secretion of dermal elements into the cystic cavity.
Spinal dermoid cysts are most often located in the lumbosacral region (60%) and cauda equina (20%) 6. They are rarely found in the cervical or thoracic spine.
They have variable imaging appearances, but commonly appear as a mass of CSF density/intensity with fat density/intensity components 2.
- well defined mass
- isodense to CSF, often with hypodense components (fat)
- calcification may be present
- minimal enhancement may be demonstrated
- widening of the spinal canal, flattening of the pedicles and laminae and osseous erosions may be demonstrated
Signal intensity may be homogeneous or heterogeneous. Typical signal characteristics include:
T1: hypo or hyperintense
- hypointense: water content
- hyperintense: due to the presence of fatty secretions of sebaceous glands
- T2: hyperintense
- FLAIR: hyperintense compared to surrounding CSF
- T1 C+ (Gd): no enhancement or mild rim enhancement
- DWI: less likely to show diffusion restriction than epidermoid
If rupture occurs, multifocal T1 high signal areas (fat) are demonstrated within the subarachnoid space and/or ventricular system.
Treatment and prognosis
Although benign and slow growing, dermoid cysts carry a risk of rupture which is associated with a high morbidity and mortality 7. A dermoid cyst can rupture during surgery, after a trauma or spontaneously.
Surgical excision is the treatment of choice, resulting in improvement or stablilisation of symptoms in the majority of patients 4.
General imaging differential considerations include:
spinal arachnoid cyst
- CSF intensity on all sequences
- no restriction on DWI
- signal suppression on FLAIR
- vertebral anomalies uncommon
spinal epidermoid cyst
- does not contain fatty elements
- more likely to demonstrate diffusion restriction on DWI
- usually present in the second to fourth decades of life
spinal neurenteric cyst
- CSF intensity on all sequences
- thoracic and cervical regions most common
- usually ventral to the spinal cord
- associated vertebral anomalies common
- homogeneously hyperintense on T1 and T2 weighted images
- cervical and thoracic regions most common
- heterogenous appearance on T1 and T2 weighted images (fat, soft tissue, fluid, calcium)
- heterogenous enhancement of solid portions
- rarely diagnosed in patients older than two years of age
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- 8. 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;43 (1): 19-27. Eur J Radiol (link) - Pubmed citation