23-year-old female with history of Lhermitte-Duclos and left posterior fossa tumor resection on 2/23/15. Patient returned on 3/11/15 due to concern for meninigitis and was sent home with linezolid and cefepime. Patient states she had a generalized tonic-clonic seizure that lasted <2 min after a dose of cefepime. Evaluate for infection and abscess. Redemonstrated are postoperative findings related to a left occipital craniotomy for resection of a left cerebellar lesion. There is a resection cavity within the left cerebellum containing fluid of mixed intensity and minimal rim enhancement, which is likely post-surgical. There is interval increase in peripheral enhancement of the previously seen fluid collection superficial to the cranioplasty mesh, measuring approximately 4.5 x 1.7 cm (series 1001, image 4), and extends to the inferior margin of the mid C2 level. There is no diffusion restriction within the collection. Again noted are multiple foci of susceptibility artifact along the resection margin, consistent with blood products. Minimal rounded susceptibility is also present in the third ventricle. There is interval resolution of the other previously described areas of susceptibility artifact. The ventricles and sulci are unchanged without hydrocephalus. The cisterns remain patent. The left transverse sinus is patent. There is no midline shift. There are no areas of pathological leptomeningeal enhancement. Minimal linear T2/FLAIR hyperintensity is seen just above the midbody of the lateral ventricles, with extension through the right frontal lobe likely relating to a previous tract via right frontal burr hole.Normal flow-voids are demonstrated in the major intracranial vascular structures. There is abnormal up to 11-mm extension of the cerebellar tonsils below the level of the foramen magnum, likely relating to an acquired Chiari malformation. There is associated significant crowding at this level, although the cerebellar tonsil contour remains rounded. The midline structures and craniocervical junction are otherwise within normal limits.
1. Postoperative findings related to resection of a left cerebellar lesion consistent with dysplastic gangliocytoma. 2. No abnormal leptomeningeal enhancement to suggest meningitis, although lumbar puncture would be more sensitive. No intracranial abscess or empyema. 3. Again seen is a left suboccipital fluid collection superficial to the cranioplasty mesh which may represent a pseudomeningocele measuring 4.5x1.7 cm. There is interval increase in peripheral enhancement compared to prior postoperative MRI which may be related to evolving granulation tissue although superinfection of the collection is not excluded. No restricted diffusion within this collection to suggest pus. Consider sampling as clinically warranted.