Superficial Siderosis of the Spine MRI Findings
What is it?
Superficial siderosis is the chronic deposition of hemosiderin in the subpial layer of the brain and spine.
Why does it occur?
Its due to chronic, low grade bleeding and only uncommonly due to an acute subarachnoid hemorrhage.
The cause can be difficult to determine but often patients have had trauma or trans dural surgery with resultant chronic low grade bleeding from those sites. Vascular malformations and rarely patients on long term warfrin with poor control can result in superficial siderosis.
There is also an association with spinal epidural cysts which are thought to result from a tear in the dura resulting in low grade chronic bleeding and formation of an extra dural arachnoid cyst. .
What to look for on MRI?
- Hemosiderin is low signal on T2 and Gradient Echo type sequences. Look for a rim of low signal outlining the cord.
2. Hemosiderin deposition on Nerve Roots can result in arachnoiditis. Look for
- Clumping and abnormal distribution of nerve roots.
- Enhancement of nerve roots.
3. Cord Oedema
Hemosiderin lining of the cord results in abnormal movement of CSF through the cord. This can result in cord oedema with increased T2 signal in the cord.
4. Extra Dural Arachnoid Cyst: Extra dural arachnoid cysts can be associated with superficial siderosis. The mechanism is thought to be from a tear in the dura resulting in low grade chronic bleeding resulting in siderosis and formation of an extra dural arachnoid cyst due to a leak from the dural tear.