What are the 3 primary etiologies of arachnoiditis?
1. Infectious (e.g. meningitis), 2. Inflammatory (e.g. acquired, intrathecal compounds, hemorrhagic), and 3. malignant (e.g. leptomeningeal carcinomatosis, hematogenous spread of metastases, CSF seeding from primary CNS tumor).
Multiple small intrathecal hyperdensities of varying sizes are seen along the length of the spinal canal. Again, these are more dense than bone.