Case Series: Long segment extra-arachnoid fluid collections: Role of dynamic CT myelography in diagnosis and treatment planning

Abstract

We report five patients in whom spinal MRI revealed extra-arachnoid fluid collections. These spinal fluid collections most likely resulted from accumulation of cerebrospinal fluid (CSF) from a dural leak. The patients presented with either compressive myelopathy due to the cyst or superficial siderosis (SS). All of these fluid collections were long segment, and MRI demonstrated the fluid collections but not the exact site of leak. Dynamic CT myelogram demonstrated the site of leak and helped in the management of these complicated cases. Moreover, we also found that the epicenter of the fluid collection on MRI was different from the location of the leak on a dynamic CT myelogram. Knowledge of these associations can be helpful when selecting the imaging studies to facilitate diagnosis and treatment.

Keywords: Long segment; dynamic CT myelography; extra-arachnoid fluid collections; spine.

Figure 1 (A-D)

Axial gradient-echo MRI (A) shows superficial siderosis around the cerebellar hemispheres and brainstem. (B) Sagittal T2W spine MRI shows a ventral fluid collection (thin white arrows) in the thoracic spine. Axial (C) and sagittal (D) immediate CT myelogram shows contrast pooling in the ventral collection (thick black arrows) with similar contrast density in the thecal sac and ventral fluid collection at the C₅-C₆ disc level, suggesting site of leak (notched black arrow)

Figure 2 (A-H)

Axial gradient-echo MRIs from inferior to superior (A-D) shows superficial siderosis around the cerebellar folia and brainstem. Sagittal T2W (E) and axial T2W (F) spine MRIs show a ventral fluid collection extending from C₂-D₉ (thick black arrows). Also noted is a thin rim of T2 hypointensity around the surface of the cord (thin white arrows) due to superficial siderosis. Sagittal immediate dynamic CT myelogram (G) shows leakage of contrast into the ventral collection at T₁-T₂ level (notched white arrow). Axial immediate dynamic CT myelogram (H) shows a lucent line in the ventral fluid collection, which may represent a fibrous band (thin white arrow). At surgery, a connection between the ventral collection and the main dural cavity was identified on the right at the T₁-T₂ level. Also identified were multiple abnormal blood vessels near the right nerve root sleeve, one of which was an acute bleeder and was the potential source of bleeding responsible for the superficial siderosis

Figure 3 (A-G)

Sagittal (A) and axial (B-D) T2W spine MRI showing extra-arachnoid fluid collection extending anteriorly from C₆ to T₁ level (thin white arrow), with mild indentation of the thecal sac, tracking to the left posterolateral epidural space (thick white arrow) from C7 to T₂ level and becoming ventral in the upper thoracic spine (notched arrow). Cord T2 signal changes are also noted (arrow head) (A-C). Dynamic immediate CT myelogram (E, F) in left lateral decubitus position showed communication between the collection and thecal sac and asymmetric accumulation of contrast in the left C₈ perineural sheath (white arrow), suggestive of traumatic pseudomeningocoele (F). On the delayed CT myelogram images (G) there was progressively increasing accumulation of contrast within the ventral extra arachnoid collection (curved arrow)

Figure 4(A-L)

Sagittal T2 W (A,B) and axial T2W (C) spine MRIs show the ventral extra-arachnoid fluid collection (thin white arrows) extending from C₂ down to L₃ level. The thecal sac and cervical cord is displaced posteriorly by this fluid collection (thick white arrow).MR myelogram (D) also demonstrates the ventral fluid collection (thick white arrows). Sagittal immediate dynamic CT myelogram (E) shows opacification of the ventral fluid collection, with similar density of contrast in ventral fluid collection and the thecal sac at C₃–C₄ and C₄–C₅ disc levels (white arrows). Axial immediate dynamic CT myelogram at C₄–C₅ (F) disc level shows contrast density in the thecal sac and the ventral fluid collection to be similar (thick black arrows), suggesting site of leak. Axial immediate dynamic CT myelogram at C6–C7 (G) disc level shows differential opacification of the ventral fluid collection and the thecal sac (thick white arrows). In addition, pseudomeningocoeles were identified on the left at multiple levels, more prominent at C₆–C₇ (G) and C₇–T₁ (H) levels (notched arrows). The nerve root sleeves on the right appear to be separated from the collection, with the differential contrast opacity within the right-sided nerve root sleeves (arrowheads); however, the left-sided nerve root sleeves (thick white arrow) appear to be incorporated within the ventral fluid collection. Also, note the effacement of the CSF space surrounding the cord due to extrinsic compression by the ventral fluid collection (G and H). The epicenter of the compression (C₆–C₇) is lower than the site of leak (C₄–C₅). Sagittal oblique reconstructions (I) of early dynamic CT myelogram shows pseudomeningocoles at multiple levels (white arrows) on the left in the cervical spine. Sagittal delayed dynamic CT myelogram (J) shows inferior extension of the ventral fluid collection into the thoracic region (white arrows). Axial immediate (K) and axial delayed (L) images from dynamic CT myelogram of the thoracic spine show progressive equilibration of contrast in the ventral fluid collection in the thoracic region on the delayed scans (L) (thick black arrows)

Figure 5 (A-J)

Sagittal (A) and axial T2W (B) cervical spinal MRIs demonstrate ventral extradural fluid collection (white arrows) and focal myelomalacia involving the right side of the cord (notched arrow) at the site of the stab injury. Axial T2W images at T1–T2 disc level (C) again demonstrate the ventral fluid collection and the cystic myelomalacia in the right hemicord, with focal right posterolateral tethering of the cord (curved arrow). Serial axial images obtained immediately after lateral decubitus (D), after 1×360° rotation (E), and after 2×360° rotations (F) show right posterolateral leak of contrast (thick black arrows) and left posterolateral fluid collection (E,F) (black arrow). Delayed axial CT myelogram (G,H) show differential opacification of the thoracic ventral fluid collection (white arrows). Sagittal delayed dynamic CT myelogram (I) demonstrates small triangular contrast extravasation posterior to the thecal sac (blue arrows) and differential opacification of the ventral fluid collection (white arrows). Oblique sagittal delayed CT myelogram reformats (J) show contrast leak (thick black arrow)