30 year-old female status post Chiari repair 2/20/2015, currently experiencing headache There has been interval suboccipital craniotomy for Chiari repair with reconstitution of a CSF space posterior to the cerebellar tonsils. There is an approximately 32 x 7 mm sagittal dimension collection which is slightly hyperintense on both T1 and T2 technique compared to CSF located within the posterior aspect of the surgical site. Posteriorly it is bounded by a thick hypointense line contiguous with the dura, and anteriorly there is a thin hypointense line which tapers to communicate with the dura at both ends. This is poorly imaged on axial images. CSF demonstrates biphasic flow posteriorly at the level of the cerebellar tonsils, which does not extend into the aforementioned posteriorly located collection.The visualized spinal cord is morphologically normal. No evidence of syrinx formation is seen. Spinal alignment is anatomic. No pathologic marrow replacement or marrow edema is suspected.A small central disk protrusion at C5-6 is unchanged. No significant degenerative disk disease is seen elsewhere in the cervical spine. No spinal canal or neuroforaminal stenosis is detected.
There has been interval suboccipital craniotomy for Chiari repair with reconstitution of a CSF space posterior to the cerebellar tonsils. There is an approximately 32 x 7 mm sagittal dimension collection which is slightly hyperintense on both T1 and T2 technique compared to CSF located within the posterior aspect of the surgical site. Posteriorly it is bounded by a thick hypointense line contiguous with the dura, and anteriorly there is a thin hypointense line which tapers to communicate with the dura at both ends. CSF demonstrates biphasic flow posteriorly at the level of the cerebellar tonsils, which does not extend into the aforementioned posteriorly located collection. This collection may represent extradural fluid behind a thin dural patch versus a loculated collection just anterior to the dural patch.