 There are postsurgical changes of suboccipital craniotomy and resection of the posterior arch of C1 for resection of posterior fossa tumor. There is near-total if not total resection of the tumor in the surgical bed. There are foci of restricted diffusion along the medial surface of the left cerebellar hemisphere and left inferior cerebellar peduncle with some foci of susceptibility effect, which favors postsurgical change rather than minimal residual tumor. Deformity involving the inferior cerebellar vermis, fourth ventricle, and dorsal brainstem remains but improved. There are foci of T1 hyperintensity involving the interpeduncular cistern which was present preoperatively.There are scattered foci of T2/FLAIR hyperintensity in the supratentorial white matter which are nonspecific but compatible with chronic small vessel ischemic changes. 9 x 10 mm lesion involving the left aspect of the pituitary gland is again seen. No other intracranial mass, mass effect, midline shift, or herniation. There is mild prominence of the lateral and third ventricles similar to prior. There is a small fluid collection in the posterior fossa surgical bed which may represent seroma or perhaps pseudomeningocele.
1. Expected postsurgical changes of posterior fossa epidermoid/dermoid tumor resection. There is no definite evidence of residual tumor in the surgical bed. Minimal foci of restricted diffusion along the medial left cerebellar surface and left inferior cerebellar peduncle may be postsurgical although given the signal features and location of the original tumor, minimal residual foci of tumor in these regions is not entirely excluded; more definitive assessment can be made on follow up study.2. There are T1 hyperintense foci in the interpeduncular cistern which are also evident on outside preoperative studies. Findings suggest prior dermoid rupture/CSF dissemination.3. 9x10 mm lesion involving the left aspect of the sella again seen. Dedicated pituitary MRI with gadolinium can be considered for further evaluation as clinically indicated.