Increased Leptomeningeal Signal in MRI

T1 Leptomeningeal hyperintensity- melanin (neurocutaneous melanosis, metastatic melanoma), blood (subarachnoid hemorrhage), fat (ruptured dermoid).

T2 Leptomeningeal hyperintensity- melanin (neurocutaneous melanosis, metastatic melanoma), hyperoxygenation (general anesthesia/sedation), infection/meningitis, metastatic disease (pineal/posterior fossa).

T1 enhancement- melanin (neurocutaneous melanosis, metastatic melanoma), infection/meningitis, metastatic disease (pineal/posterior fossa).