Clinical question: Intracranial abscess. Signs and symptoms: High WBC in CSF. Pre-and post-enhanced brain MRI:Diffusion weighted images are unremarkable.Examination of a straight extensive postoperative changes a wide left suboccipital craniectomy and grid placement of a mesh at the level of the craniectomy site. Large CSF signal intensity extra-axial collection in the posterior fossa on the left with several mass effect on the fourth ventricle demonstrate no change in its size and overall mass effect. The fourth ventricle also remains in stable since prior exam. Approximately 8.5 mm herniation of cerebellar tonsils through the foramen magnum is fairly similar to prior exam.Examination however demonstrate significant interval increased in pseudomeningocele at the surgical site since prior study. This finding demonstrate no mass effect on the intracranial content. In largest transaxial dimensions of this collection is approximately at 64 x 66 -mm.Extensive pulsation artifact from this collection precludes precise assessment for detection of abnormal enhancement. Within this limitation however there is a very thin linear enhancement along the anterior aspect of extra-axial CSF collection intracranially. This appearance is within expected post operative change. There is also no detectable T2/flair hyperintensity of cerebella at the site to suggest presence of an infectious process/abscess. There is no convincing evidence of leptomeningeal or intraparenchymal enhancement. There is enhancement of the soft tissues or suboccipital region surrounding the pseudomeningocele which is also within expected postop change. The enhancement is less conspicuous since prior study. This observation could represent internal improvement or be as result of significant flattening and displacement of the surrounding soft tissues due to interval increased expansion of pseudomeningocele.
1.Negative diffusion weighted images.2.Extensive postoperative changes of a wide left suboccipital craniectomy with stable intracranial postoperative changes and without convincing evidence of an infectious process/abscess formation as detailed.3.Significant interval increased pseudomeningocele posterior to the craniectomy site as detailed. Mild enhancement of surrounding soft tissues are expected postop changes. No convincing evidence of an abscess formation.