Left Occipital Intradiploic Epidermoid Cyst: A Rare Entity with Imaging and Surgical Insights

Case Findings Clinical presentation A 30-year-old male presented with a progressive, painless left occipital swelling for 3 months, associated with the persistent headaches. Examination revealed a firm, smooth, non-tender swelling without neurological deficits. Imaging findings: [Figure 1a-e] Magnetic Resonance Imaging (MRI) demonstrated a well-circumscribed, T1 hypointense, T2 hyperintense lesion within the diploic space of the left occipital bone with diffusion restriction, consistent with an intradiploic epidermoid cyst. Computed Tomography (CT) showed an expansile bony defect with thinning of the inner and outer tables. MR venography revealed compression of the left transverse sinus without thrombosis.Figure 1: Preoperative MRI of the patient shows T1 hypointense (a), T2 hyperintense (b), Diffusion restricting lesion (c) in the left occipital bone. Preoperative CT—Bone Window (d) shows Lytic expansile bony lesion in the left occipital bone. MR Venogram (e) shows the absence of flow in the left transverse sinus due to compression by the lesion. Intraoperative images (f) show cheesy white material in the left occipital bone and (g) shows the exposed unilateral transverse sinus after removing the lesion. Postoperative CT (h) shows complete excision of lesion with defect reconstruction using bone cement cranioplastySurgical management: [Figure 1f, 1g] A left occipital craniotomy was performed for total excision. Intraoperatively, a thick-walled cyst filled with pearly white, caseous material was noted, adherent to the dura. Complete excision was achieved, preserving the dura, and the resultant calvaria defect was reconstructed using bone cement. Postoperative outcome: [Figure 1h] The patient recovered uneventfully with resolution of headaches. Follow-up imaging confirmed total excision and stable reconstruction. Discussion Intracranial intradiploic epidermoid cysts are rare, benign lesions of ectodermal origin, most found in the frontal and occipital bones. They account for only 0.2%–1.8% of intracranial lesions, with the intradiploic variety comprising less than 25% of cases. Though often asymptomatic, larger cysts may cause compressive symptoms.[1,2] Surgical excision is the treatment of choice to prevent recurrence. Large lesions, such as in our case, can cause significant bony erosion and sinus compression, necessitating careful preoperative planning and cranioplasty for structural integrity.[1] This case highlights the importance of considering intradiploic epidermoid cysts in the differential diagnosis of occipital swellings. Early surgical intervention ensures optimal outcomes and prevents potential complications. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.