Meningitis/abscess and pseudomeningocele. Also, history of fourth ventricle mass resection (cerebellar ganglioglioma) and posterior fossa decompression. Evaluate for changes. There are changes of previous suboccipital craniectomy and tumor resection. The overlying CSF intensity fluid collection is more distended, now measures 3 cm in depth compared to 2 cm previously. The collection is slightly more well circumscribed with better defined T2-hyperintense wall. The posterior wall at midline is inseparable from the skin but there is also susceptibility artifact in the region. There is suggestion of the area of direct communication of the CSF space with the pseudomeningocele to the right of midline on 701/4, with flow artifact.The surgical cavity in the inferior aspect of the fourth ventricle is slightly smaller. The contrast enhancement along the surgical margins has decreased since the prior examination. Ex vacuo enlargement and distortion of the fourth ventricle are unchanged as well as the chronic postoperative changes in the right cerebellar hemisphere, cerebellar vermis and the right-sided cerebellar peduncles. There is no acute infarct. Scattered foci of susceptibility effect are present in the resection bed as well as in the ventricular system. Tiny focus of T2-hyperintensity in the body of the left caudate nucleus is unchanged, likely chronic sequela of prior injury. Otherwise, the supratentorial brain is unremarkable.The incidental, eccentric to the right, CSF intensity pineal cyst, which measures up to 2 cm, is unchanged nor the associated mass effect on the tectum. The sylvian aqueduct remains patent and there is no lateral/third ventricular dilatation. Flow artifact continues to be more exaggerated in the region of the left foramen of Monro.The small cyst in the superior anterior aspect of the left maxillary sinus is unchanged. Mild mucosal thickening is present in the right ethmoid sinuses. The orbits are grossly unremarkable.
1.The suboccipital pseudomeningocele is larger with more convex margins than on the previous MRI from January 2016. It shows no definite signs of associated inflammation.2.Chronic and evolving postoperative findings are present in the posterior fossa without sign of definite tumor recurrence. However, flow-related artifact partially obscures the treatment bed, especially on postcontrast imaging.