Purpose or Case Report: An 11-year-old female presented with 3-weeks history of intractable vomiting, nausea, blurred vision, vertical nystagmus and ataxia with gait instability. A CT scan revealed a small calcification at the left craniocervical junction (CJJ) and mild effacement of the fourth ventricle (Figure). MRI showed a partially-enhancing medulla oblongata lesion and a non-enhancing cystic exophytic lesion abutting the left pre-medullary cistern. There was avid thick enhancement along the ventrolateral surface of the medulla oblongata. No restricted diffusion was present. MR spectroscopy demonstrated decreased NAA and elevated lactates. Based on imaging findings, a brainstem glioma with exophytic component was suspected. The CBC, CMP, ESR and CRP were normal. The patient underwent suboccipital craniectomy with C1 laminectomy, and an exophytic pale gray mass was identified. Multiple specimens were taken, and frozen diagnosis showed only necrosis. The cyst wall was resected. Resection of the brainstem component was limited by neurophysiology. Histologically, the lesion consisted of a fibrous cyst wall lined by columnar to pseudostratified columnar epithelium, findings reflecting a neuroenteric cyst. No glial tissue was identified. Gram stain and Grocott stain were negative for bacterial and fungal specimens. An empiric treatment with wide spectrum antibiotic was started. Follow-up MRI demonstrated near complete resolution of edema in the medulla oblongata, and substantial decrease in enhancement in anterolateral exophytic component and patient has substantially improved clinically. In retrospect, a sinus tract extended from the cystic lesion at the craniocervical junction into the brainstem causing edema, inflammation and enhancement which resolved once the cyst was surgically decompressed.

Conclusion:
This case shows a neuroenteric cyst connected to the brainstem, through a sinus tract leading to chronic inflammation and infection, resulting in imaging findings resembling a brainstem glioma. Surgical decompression of the cyst and antibiotic treatment resulted in resolution of the brainstem lesion.
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