Epidermoid inclusion cyst
encapsulated, nonenhancing extradural mass is seen compressing the conus
medullaris. The mass is isointense to cerebral spinal fluid (CSF) on T1-weighted imaging (T1WI) and heterogenous on T2-weighted imaging (T2WI) with portions isointense and hypointense to CSF.
Epidermoid inclusion cysts are benign neoplasms composed entirely of
ectodermal tissue. Approximately 60% are congenital and 40% are acquired. As
demonstrated in this case, acquired epidermoids, arise from iatrogenically
implanted epithelial elements from procedures such as lumbar punctures or back
surgery. In particular, advancing a needle during lumbar puncture without the
stilette in place can implant epithelial elements into the spinal canal.
Epidermoids of the spine are rare and constitute less than 1% of
intraspinal tumors. They may be extramedullary intradural or extradural. Epidermoids are slow growing neoplasms that present with slowly progressive symptoms, such as radicular back pain, paresthesias, and sphincter dysfunction. The masses are encapsulated and contain desquamated epithelial
keratin and cholesterol crystals. Most often they are smooth or lobulated, but they
may occasionally be nodular.
As with intracranial epidermoids, acquired spinal epidermoids tend to follow CSF signal on both T1WI and T2WI. As in this case, the T2WI may be heterogenous with only portions of the mass demonstrating CSF signal. No enhancement is seen after the administration of contrast material. Diffusion-weighted
imaging should demonstrate restricted diffusion.
Treatment consists of complete surgical resection.
Key learning point: A nonenhancing mass in the region of the cauda
equina in a patient with a history of lumbar puncture or back surgery is
suggestive of an acquired epidermoid.
Kikuchi K, Miki H, Nakagawa A. The utility of diffusion-weighted
imaging with navigator-echo technique for the diagnosis of spinal epidermoid
cysts. Am J Neuroradiol. 2000;21:1164-1166.
- Potgeiter S, Dimin S, Lagae, L, et al. Epidermoid tumours associated with lumbar punctures performed in early neonatal life. Dev Med Child Neurol. 1998;40:266-269.