Intradural extramedullary thoracic epidermoid cyst in the absence of dysraphism: A case report and literature review.

Background: Spinal epidermoid cysts (ECs) account for <1% of all intraspinal tumors. They may be congenital (i.e., resulting from ectodermal inclusions during neural tube closure) or acquired (i.e., secondary to trauma or repeated lumbar punctures). Their indolent growth is attributed to progressive desquamation of keratinized epithelial cells that produce increasing neurological symptoms/signs due to increased mass effect on surrounding neural structures. Case Description: A 32-year-old female presented with 3 months of bilateral dorsal paresthesias; on examination, she exhibited numbness dorsally and bilaterally in the T6 dermatome. The thoracic MR demonstrated an intradural extramedullary (IDEM) dorsal T6 cyst that compressed the cord and bilateral T6 nerve roots. She underwent a T5-T7 laminectomy with durotomy for gross total cyst resection. The histopathology confirmed an EC (World Health Organization 2021). Her postoperative recovery was uneventful, and at 12-postoperative months, she was asymptomatic without MR evidence of cyst recurrence. Conclusion: Spontaneous thoracic IDEM ECs without dysraphism are exceedingly uncommon. Magnetic resonance imaging, particularly with diffusion-weighted sequences, is essential for accurate preoperative diagnosis. Gross total microsurgical resection, including the cyst wall, is the treatment of choice, but adhesions may occasionally preclude such complete removal.