Hemosiderin deposition on Nerve Roots can result in arachnoiditis.

1. Clumping and abnormal distribution of nerve roots.
2. The normal symmetric distribution of nerve roots is lost and there is asymmetry in their distribution. (2nd and 3rd images below asymmetric distribution of nerve roots).
3. The nerves can also stick to each other resulting in the appearance of an enlarged nerve root (Green arrow).

1. Enhancement of nerve roots can occur but is not always present.
2. Enhancement is secondary to inflammatory changes induced by the hemosiderin deposition.
3. Giving contrast is not essential to making a diagnosis of arachnoiditis in superficial siderosis.

1. Superficial siderosis of the cord  (Pink arrow) can result in cord oedema (Blue arrow).
2. WHY IS THAT? 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.

1. Extra dural arachnoid cysts (Green arrow) can be associated with and result in superficial siderosis (Pink arrow).
2. 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.