Types of Superficial Siderosis
Introduction
The research community’s knowledge and understanding of superficial siderosis is ever-evolving. With three known recognized subvariants of superficial siderosis, it remains crucial treating clinicians are aware of the most recent data. While medical opinions remain divided, anecdotal patient reports and first-hand evidence observed over the last six years have demonstrated while surgical intervention may slow progression, as long as hemosiderin remains in place, the symptom progression will continue.
Your physician will review your MRI to determine which type of superficial siderosis is present. There are three variations which present a unique set of symptoms.
There is currently no means available to reverse neural degeneration once it occurs. The damage suffered in the brain, spinal cord, or cranial nerves is permanent, with the exception of the olfactory cranial nerve. This nerve has demonstrated a unique ability to regenerate and reverse the damage once free iron and the resulting oxidative stress are removed.
Superficial Siderosis Subvariants
INFRATENTORIAL SUPERFICIAL SIDEROSIS, TYPE 1 (CLASSICAL) (ISS)
Infratentorial superficial siderosis, type 1 (classical) (iSS), or superficial siderosis of the central nervous system, is a profoundly disabling degenerative subvariant of superficial siderosis affecting the brain and spinal cord. iSS affects all races, ethnicities, and genders, with onset manifesting at any age. Persistent long-term hemorrhage into the subarachnoid space results in a neuro-toxic accumulation of free iron products on the brain and pia mater from circulating cerebrospinal fluid. This circulation distribution process may also result in hemosiderin deposition in the supratentorial region. Bergman glia and microglia cells in the cerebellar cortex function as conduits for iron entering the tissue, facilitating ferritin biosynthesis resulting in accumulation within the superficial layer of astrocytes, the gray matter of the brain, oligodendroglia, and sub-ependymal tissue.
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INFRATENTORIAL SUPERFICIAL SIDEROSIS, TYPE 2 (SECONDARY)
Infratentorial superficial siderosis, type 2 (secondary), displays radiologically in an infratentorial region but is restricted to a single area extensively involving intracranial hemorrhage with only a thin rim of hemosiderin in adjacent areas. Iron and heme products are introduced from a major single acute intracranial hemorrhagic event and are not distributed via the circulation of cerebral spinal fluid. Clinical features will be restricted to the affected region. For example, a patient may present with symptoms of gait/truncal ataxia or balance issues, but their hearing may never display any impairment beyond the ordinary aging process. (Kharytaniuk N. et al, Practical Neurology 2022; 22:274-284)
CORTICAL SUPERFICIAL SIDEROSIS (CSS)
Cortical superficial siderosis (cSS) radiologically presents only in the supratentorial region of the cerebrum, limited to cortical sulci favoring cerebral convexities of the cerebral hemispheres. It is most often associated with cerebral amyloid angiopathy (CAA), where rupture of amyloid-laden leptomeningeal arterioles results in subarachnoid bleeding over the cerebral convexities, resulting in subpial cortical hemosiderin. The etiology is primarily recognized as an age-related cerebral small vessel disorder.
Patients with Alzheimer’s disease are nearly seven times more likely than other patients to radiologically display a serpentine pattern of cortical superficial siderosis (cSS) hemosiderin deposition across the brain’s surface. (Zonneveld et al, Feb 25, 2014, Neurology)
