PMC4163907_01
(a) Sagittal T1 MRI shows descended tonsils at C2 level and occupying posterior aspect of the foramen magnum. CSF flow is blocked at this point (arrow). (b) Sagittal T2 MRI shows a small syrinx at C3-C4 level (arrow). (c) Axial T2 MRI shows that the posterior aspect of the foramen mag-num is occupied by the descended tonsils (arrows)
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F1
A magnetic resonance imaging (MRI) showed mild basilar impression, cerebellar tonsils at C2 level, a small syrinx at C3-C4, and no hydrocephalus [Figure 1a and b].
(a) Postoperative routine CT scan (48 h postoperative) shows the absence of complications. (b) Urgent cranial CT scan on the fifth postoperative day shows a posterior fossa epidural hematoma (white arrow) causing compression of cerebellar hemispheres, vermis, and fourth ventricle (gray arrow)
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F2
The immediate postoperative course was uneventful with a routine computed tomography (CT) scan performed 48 h after surgery demonstrating the absence of complications [Figure 2a]. Emergent CT scan revealed a posterior fossa epidural hematoma compressing cerebellum, upper spinal cord, and the fourth ventricle [Figure 2b].
(a) One year after initial surgical procedure, sagittal T1 MRI shows the patent bone decom-pression of the posterior fossa and fibrous tissue (arrow). (b) Sagittal T2 MRI: shows a great syrinx cavity at C3-C4 levels (white arrow) and the absence of CSF signal around the cerebellar hemispheres (arrowhead). (c) Axial T2 MRI at the level coincident with obex: it shows the intense adherence of arachnoid tissue (arrow), which produces a blockage of CSF flow
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F3
A remarkable enlargement of the previous syrinx cavity was also demonstrated at C3-C4 level [Figure 3].
(a) The syrinx cavity has become smaller (white arrow) and CSF signal appears in the pos-terior aspect of cerebellum-medulla (arrowhead). (b) The dural graft has been detached from the parenchymal surface (arrow)
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F4
The postoperative MRI showed decreasing of the sirynx and patency of the subarachnoidal space [Figure 4].