Intravenous enhanced 3D FLAIR imaging to identify CSF leaks in spontaneous intracranial hypotension: Comparison with MR myelography

Abstract

Purpose: To evaluate the clinical utility of intravenous gadolinium-enhanced heavily T2-weighted 3D fluid-attenuated inversion recovery (HT2-FLAIR) imaging for identifying spinal cerebrospinal fluid (CSF) leaks in patients with spontaneous intracranial hypotension (SIH).

Methods: Patients with SIH underwent MR myelography and post-contrast HT2-FLAIR imaging after an intravenous gadolinium injection. Two types of CSF leaks (epidural fluid collection and CSF leaks around the nerve root sleeve) at each vertebral level were compared between the 2 sequences. The total numbers of CSF leaks and vertebral levels involved were recorded for the whole spine. The sequence that was superior for the overall visualization of epidural and paraspinal fluid collection was then selected.

Results: Nine patients with SIH were included in the present study. HT2-FLAIR imaging was equivalent or superior to MR myelography at each level for detecting the 2 types of CSF leaks. In the 2 types of CSF leaks, the total numbers of CSF leaks and levels involved were higher on HT2-FLAIR images than on MR myelography, while no significant difference was observed for CSF leaks around the nerve root sleeve. In all 9 patients, HT2-FLAIR imaging was superior to MR myelography for the overall visualization of epidural and paraspinal fluid collection.

Conclusion: Intravenous gadolinium-enhanced HT2-FLAIR imaging was superior to MR myelography for the visualization of CSF leaks in patients with SIH. This method can be useful for identifying spinal CSF leaks.

Keywords: CHESS, Chemical shift selective; CSF, Cerebrospinal fluid; FLAIR, Fluid-attenuated inversion recovery; HT2-FLAIR, Heavily T2-weighted fluid-attenuated inversion recovery; Heavily T2-weighted 3D FLAIR; Intravenous gadolinium-enhanced MR imaging; MIP, Maximum intensity projection; MPR, Multiplanar reconstruction; MR myelography; MRI, Magnetic resonance imaging; SIH, Spontaneous intracranial hypotension; Spinal cerebrospinal fluid leak; Spontaneous intracranial hypotension; T1W, T1-weighted; T2W, T2-weighted; TSE, Turbo spin echo.

Fig. 1

Distribution of CSF leaks on MR myelography and HT2-FLAIR images. Two types of CSF leaks are most commonly observed at the T level (epidural fluid collection in (a) and CSF leaks around the nerve root sleeve in (b)).

Fig. 2

A 52-year-old female with SIH (case 7). Sagittal MR myelography (a) shows epidural fluid collection within the spinal canal dorsal to the dural sac at T5-8 (arrowheads). Epidural fluid collection ventral to the dural sac is invisible. Sagittal post-contrast HT2-FLAIR imaging (b) reveals contrast enhancement within the spinal canal that was absent in pre-contrast imaging (c), corresponding to epidural fluid collection shown in A. Note that enhanced CSF leaks are more widely distributed at T4, T9-11 dorsal, and T1-6 ventral to the dural sac (arrowheads). Axial MR myelography (d) shows CSF leaks in the dorsal epidural space (arrowhead) and around the left T6 nerve root sleeve (arrow). Unsuppressed fat, which is slightly hyperintense, obscures the CSF leak (asterisks). The dura mater is visible as a hypointense band-like structure (small arrow). Axial subtraction HT2-FLAIR imaging (e) depicts CSF leaks circularly surrounding the dural sac and around bilateral nerve sleeves (arrows). CSF is not enhanced in the subarachnoid space. MIP of MR myelography (f) provides a panoramic view of CSF leaks, with CSF leaks around the nerve root sleeves being more conspicuous on MIP of subtracted HT2-FLAIR imaging (g, arrowheads). Of note, epidural fluid collection, which was not differentiated from subarachnoid CSF on MIP of myelography, is clearly visible.

Fig. 3

A 50-year-old female with SIH (case 4). Sagittal MR myelography (a) shows retrospinal fluid collection at C1-2 (arrow) also known as the C1-2 sign. Unsuppressed paraspinal and subcutaneous fat is observed in the posterior neck (arrowhead), obscuring or mimicking the CSF leak. Sagittal post-contrast HT2-FLAIR imaging (b) shows the enhancement of the retrospinal CSF leak (arrow), which is more clearly visible on subtracted HT2-FLAIR images (c) due to the canceling of the fat signal. Paraspinal CSF leaks in the interspinous space are also noted at C3-4 to C6-7 (arrows).

Fig. 4

A 50-year-old female with SIH (case 4, same patient as in Fig. 3). Sagittal fat-suppressed T2W imaging (a) displays subtle arched hyperintensities in the interspinous epidural space at the lumbar level (arrows), termed the “Dinosaur tail sign”, which may reflect a subtle amount of CSF leakage. MR myelography (b) shows this sign at L2-3 to L4-5 (arrows). This sign is stronger on post-contrast HT2-FLAIR images (c) than on pre-contrast images (d), and is more conspicuous, particularly at T12-L1 and L1-2 (arrows). Epidural fluid collection, which is observed dorsal and ventral to the dural sac as a hypointense line (b, small arrows), is also more clearly visible. Each image in the lower row (e-h) shows the magnification of the lumbosacral traditional area in the upper row (a-d). On fat-suppressed T2W images (e), epidural venous plexuses (arrowheads) are more hypointense than epidural fluid collection (arrows) ventral to the dura mater (small arrows). MR myelography (f) shows that epidural venous plexuses (arrowheads) are more hypointense than epidural fluid collection (arrows), indicating stronger contrast between veins and fluid than on fat-suppressed T2W images. Of note, post-contrast HT2-FLAIR imaging (g) showed no or the weaker enhancement of veins (arrowheads) than that of CSF leaks (arrows). These venous structures are mildly hyperintense on pre-contrast HT2-FLAIR images (h, arrowheads).

Fig. 5

A 16-year-old male with SIH (case 5). Sagittal MR myelography (a) and fat-suppressed T2W imaging (b) show linear-shaped fluid collection (arrow) within sacral epidural fat caudally extending from the distal termination of the dural sac, which reflects an epidural CSF leak. The filum terminale internum (a, small arrow) fuses with the distal end of the dura mater. The basivertebral veins (arrowheads) and epidural venous plexuses (dotted arrows) are mildly hyperintense on MR myelography (a), while these venous structures exhibit hyperintensity on fat-suppressed T2W imaging (b). In contrast to pre-contrast HT2-FLAIR imaging (c), post-contrast HT2-FLAIR imaging (d) shows the marked enhancement of the CSF leak and greater conspicuity than MR myelography. Of note, post-contrast HT2-FLAIR imaging shows no or only the weak enhancement of the veins described above (d, arrowheads and dotted arrows).

Fig. 6

A 40-year-old female with SIH (case 6). Sagittal MR myelography (a) shows a meningeal diverticulum at the left S2 (arrowhead), while post-contrast HT2-FLAIR imaging (b) shows no enhancement of the meningeal diverticulum despite enhancing CSF leaks in the epidural space (arrowheads).

Fig. 7

A 31-year-old male with SIH (case 9). Axial MR myelography (a) shows the dilated epidural venous plexus (arrowhead) within epidural fluid collection and the dura mater (arrows). Post-contrast HT2-FLAIR imaging (b) shows no enhancement of the epidural venous plexus (arrowhead) with the enhanced CSF leak. Furthermore, CSF is not enhanced in the subarachnoid space.

Fig. 8

A 50-year-old female with SIH (case 4, same patient as in Fig. 3). Axial MR cisternography (a) of the head shows the C1-2 sign (arrow). In contrast to pre-contrast HT2-FLAIR imaging (b), post-contrast HT2-FLAIR imaging (c) shows contrast enhancement of the C1-2 sign (arrow), while fat-suppressed T1W imaging (d) shows the weak enhancement of this sign (arrow). This retrospinal fluid collection is continuous with epidural fluid collection (c, small arrow). Of note, the suboccipital cavernous sinus (arrowheads) and epidural venous plexus (dotted arrows) show no or weaker contrast enhancement on post-contrast HT2-FLAIR imaging (c) than on T1W imaging (d). These venous structures exhibit stronger contrast enhancement than CSF leaks on T1W imaging.