 There are unchanged postoperative findings are related to burr hole for previous left frontal lobe biopsy. There is unchanged confluent T2 hyperintensity throughout the bilateral cerebral hemispheres, most prominent within the frontal lobes. There are unchanged focal regions of cystic volume loss and an unchanged focus of T1 hyperintense susceptibility within the posterior callosal body. There has been interval increase in size of previously linear enhancement within the left thalamus into a now peripherally enhancing 11x 7 mm lesion with associated T2 hyperintensity and adjacent linear enhancement. There is no evidence of elevated perfusion although evaluation of a lesion of this size in this location is somewhat limited. In comparison with prior exams, areas of cystic volume loss previously showed a similar enhancing evolution prior to becoming frankly cystic. There is unchanged dura-arachnoid thickening along the left cerebral hemisphere and less prominently along the right frontal lobe. There is no evidence of acute infarct. The ventricles and basal cisterns are unchanged in size and configuration. There is no midline shift or herniation. The major cerebral flow voids are intact. There is maxillary sinus mucosal thickening.
Developing left thalamic ring enhancement has an appearance similar to that of the scattered regions of cystic volume loss prior to them becoming cystic. The differential diagnosis includes a subacute lacunar infarct vs radiation necrosis with tumor progression felt much less likely. The examination is otherwise stable. 