Spinal Epidermoid cyst MRI

Clinically: A 30 y o male with neurogenic bladder. 

Findings:

This MRI lumbar spine show a spinal intra dural cystic signal intensity well defined lesion hypo intense on T1, hyper intense on T2 with restricted diffusion on Dw images. 

An associated expansion and scalloping of bony spinal canal. 

Lesion is confined to spinal canal and not extending out of neural foramen. 

Lesion is non enhancing on post contrast, except thin rim of enhancement on post contrast T1. 

Imaging diagnosis : Spinal Epidermoid Cyst.

Urinary bladder show diffuse wall thickening, irregularity with trabeculations attributed to associated Neurogenic bladder. 

Spinal Epidermoid Cyst

They are usually extra medullary but rarely can be intra medullary. They may be congenital or acquired.
Spinal epidermoid cysts are uncommon.

Unlike intracranial epidermoid cysts, which are almost always congenital in origin, most of spinal epidermoid cysts are acquired. Although present since birth, congenital epidermoid tumours often do not present until the second to fourth decade of life.
Males are more commonly affected than females.

Spinal epidermoid cysts may asymptomatic and discovered incidentally. If symptomatic, motor disturbances, pain, sensory disturbances, and bowel or bladder dysfunction may be present.
Congenital spinal epidermoids result from anomalous implantation of ectodermal cells during closure of the neural tube between the third and fifth week of embryonic life.
Acquired spinal epidermoids are a late complication of lumbar puncture, resulting from implanted epidermal elements into the spinal canal. The time interval between lumbar puncture and tumour diagnosis ranges from 1 to more than 20 years. Acquired spinal epidermoids are generally extramedullary and situated near a vertebral interspace.

Congenital epidermoids usually occur at the conus or cauda equina. Acquired cysts are found in the lower lumbar region.
Epidermoid cysts are commonly associated with spinal malformations such as spina bifida and hemivertebrae.

On CT, a well circumscribed mass, hypodense (similar to CSF),  minimal to no enhancement on post contrast, calcification is rare. Associated osseous changes include an expanded spinal canal, laminar thinning and vertebral body scalloping. 

On MRI typical signal characteristics include hypointense (similar to CSF) on T1, hyperintense (similar to CSF) on T2 and slightly hyperintense compared to CSF on FLAIR due to incomplete signal suppression. On T1 C+ (Gd) no enhancement or a thin rim of capsular enhancement. Characteristic bright signal on Diffusion with corresponding low intensity on ADC map. Signal intensity may be homogeneous or heterogeneous according to the variable water, lipid and protein composition of the cyst.

Spinal epidermoid cysts are slow growing.
Surgery is the treatment of choice, complete excision.
If the cyst wall is tightly adherent to the cord parenchyma, the wall should be left in place, however this leads to a risk of recurrence.

Differential diagnosis include spinal arachnoid cyst which lacks brightness of restricted diffusion on DWI, complete signal suppression on FLAIR. Vertebral anomalies uncommon.
Spinal dermoid cyst usually contains fatty elements, less likely to demonstrate diffusion restriction on DWI, patients are usually younger than 20 years of age.
Spinal neurenteric cyst common in thoracic and cervical regions, ventral to spinal cord with associated vertebral anomalies.