The most commonly described underlying cause of<unk>  is chronic bleeding into the subarachnoid space of the brain, which releases erythrocytes, or blood cells, into the cerebrospinal fluid. The chronic bleeding can come from many sources such as from an arteriovenous malformation or cavernous malformation, myxopapillary ependymoma of the spinal cord, from chronic subdural hematoma, from a ventricular shunt, or from chronic subarachnoid hemorrhage. Chronic bleeding sources can also be a result of past brain surgery or CNS trauma, which may be the most common cause of<unk> , with<unk>  showing up many years later. In up to as many as half of all described cases the source of bleeding was never found.
Superficial siderosis
Geographic atrophy
Neurofibrillary tangle
Polymicrogyria
Posterior cortical atrophy
Amyloid plaques
Hippocampal sclerosis
Hemosiderin hyperpigmentation