Superficial siderosis is the chronic deposition of hemosiderin in the subpial layer of the brain and spine

• It's due to chronic, low grade bleeding and only uncommonly due to an acute subarachnoid haemorrhage.
• 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 warfarin 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.

1. Hemosiderin is low signal on T2 and Gradient Echo type sequences.
2. Look for a rim of low signal outlining the cord (Blue and Pink arrows below).

• Hemosiderin deposition on Nerve Roots can result in arachnoiditis. Look for:

  1. Low signal of nerve roots (Orange arrow).
  2. Clumping and abnormal distribution of nerve roots (Green Arrow and centre image with asymmetric nerve root distribution).
  3. Enhancement of nerve roots.

• If you see hemosiderosis on a spinal MRI look for an underlying cause.
• You need to image the whole spine and also the brain to look for a cause of the chronic bleeding.

We look at the complications of Superficial Siderosis in the next post.