Spontaneous Intracranial Hypotension: A Systematic Imaging Approach for CSF Leak Localization and Management Based on MRI and Digital Subtraction Myelography

Type 1 CSF leak (SLEC-P). A, Schematic drawing shows the relationship of the intervertebral disc spur and a ventral dural tear. B, “Shoot though” lateral subtracted image of the thoracic spine DSM with the patient positioned prone on the table. The patient's head is toward the top of the image and feet at the bottom. The contrast material can be seen escaping from the ventral aspect of the thecal sac at the T7–8 level (arrow).

Type 2 CSF leak (SLEC-P). A, Schematic depiction of a proximal nerve root sleeve tear bridging the epidural and neural foraminal compartments. B–G, From a single patient. B, Sagittal T1WI of the brain shows the engorged pituitary gland (open white arrow) and dural thickening on the clivus (short white arrows). C, Sagittal T1WI of the brain shows a “positive venous distension sign” with a convex undersurface of the middle third of the dominant transverse sinus (short black arrow). D, T2-weighted axial MR image of the thoracic spine shows SLECs (white arrows) external to the dura (white arrowhead). E, Subtracted image from a prone thoracic DSM shows a posterolateral collection of contrast (black arrow). F and G, Subtracted and nonsubtracted images from a repeat right lateral decubitus DSM show contrast leaking into the extradural space (black arrows) from a tear along the proximal aspect of the right T11 root sleeve (long white arrow). Note the BB (nipple marker) placed on the skin for landmarking (dashed white arrow).

Type 3 CSF leak (SLEC-N). A, Schematic depiction of a CSF-to-venous fistula arising from a dural tear along the nerve root sleeve beyond the epidural compartment (see text). Nonsubtracted (B) and magnified, subtracted (C) images from separate left-side-down DSM runs in a patient negative for SLEC with SIH. A small vascular structure, in keeping with a tortuous vein of a CVF, can be seen coursing away from the root sleeve (arrows). An incidental normal diverticulum is also noted at the level above (arrowhead). D and E, Nonsubtracted images of decubitus DSMs of 2 other similarly presenting patients negative for SLEC demonstrating CVFs. Globular collections of contrast (dashed arrow) are commonly seen near the expected zone of origin of the vein, possibly representing a focal extravasation (pseudomeningocele) of contrast or a diverticulum from which the vein appears to arise.

Type 4 CSF leak (SLEC-N). A, Schematic depiction of a distal nerve root sleeve dural tear occurring beyond the epidural compartment extravasating into the surrounding fascial planes and loose connective tissue without loculation or fistulization. B, CT of the head. Sagittal reformat in a patient negative for SLEC demonstrates large low-density (bilateral) subdural hemorrhages (asterisk). Note the prominent “venous distension sign” (short arrow) despite the large subdural hemorrhages. C, Axial CT image obtained 10–20 minutes post-DSM shows subtle extravasated contrast in the region of the right C8 nerve (arrow). Note that on this nondynamic CT (slightly degraded due to beam-hardening artifacts associated with the shoulders), there is little to help distinguish this extravasated contrast from a normal diverticulum. D, Subtracted image from a right-side-down decubitus DSM shows extravasation of contrast (arrows) into the paraspinal tissues from a leak along the mid-to-distal right C8 nerve root sleeve.