 Redemonstrated is evidence of the patient's known multifocal anaplastic astrocytoma. A dominant expansile infiltrating T1 hypointense and T2 hyperintense tumor involving much of the left pons, left midbrain, left cerebral peduncle and left thalamus is again noted. Based on multiple measurements on T2 sequences, this lesion appears somewhat decreased in size. For instance, on series 501, image 14 the lesion measures 19 x 32 cm compared to 23 x 36 cm previously. There are interval postoperative changes from a small craniotomy as well as a small area of encephalomalacia along the right lateral cerebellum which probably reflects site of prior biopsy. Abnormal T2 signal within this right lateral cerebellar hemisphere is smaller than before likely related to the biopsy. T2/flair signal abnormality within the left lateral cerebellar hemisphere has decreased in size. Questionable very subtle tumor infiltration involving the right ventral pons and the right ventral midbrain are not as well appreciated on this study. There appears to be no significant enhancement or restricted diffusion. A few scattered small foci of susceptibility weighted abnormalities are noted elsewhere which is nonspecific and may be related to microhemorrhage secondary to radiation therapy.The ventricles and sulci are unchanged. There is no midline shift or herniation. There are no extraaxial fluid collections or subdural hematomas. Flow voids are present within the major vessels indicating patency. The paranasal sinuses and mastoid air cells are clear.
1.Decrease in size of the known multifocal anaplastic astrocytoma as described above.2.Post-operative changes from a right lateral cerebellar biopsy.