Acute to Chronic Variants in the Imaging Spectrum of Superficial Siderosis: Case Series and Literature Review

Superficial siderosis is a rare neurodegenerative disease, related to the deposition of hemosiderin in the central nervous system secondary to recurrent bleeding into subarachnoid space and results in chronic or progressively neurological deterioration. It tends to be due to chronic slow haemorrhages in the setting of previous cranio-spinal trauma or neurosurgery that had been done decades ago. It is important to diagnose the disease as soon as possible because if left untreated it can cause progressive ataxia and deafness, which will require surgical intervention. There are three types of superficial siderosis: Type 1 (the classical infratentorial variant), which is characterised by symmetric deposits in the cerebellum, brain stem, or cranio-cervical junction; type 2 (secondary infratentorial subdural hygroma), an acquired non-communicating secondary supratentorial subdural hygroma (SSDH) subtype manifesting as limited asymmetric fluid collections related to a single intracranial bleeding event and supratentotrial superficial siderosis that represents deposition along cerebral convexities usually due previous hemorrhagic episodes. A singular form is "acute superficial siderosis syndrome," progressing much more rapidly than pure superficial siderosis and due to recurrent haemorrhages. The present case series is intended to describe and illustrate acute and chronic manifestations of superficial siderosis, emphasizing its distinct imaging appearances facilitating early recognition, leading to prompt management.