What is Superficial Siderosis?
Superficial siderosis is a slowly progressive chronic neurodegenerative condition due to iron toxicity from persistent subarachnoid bleeding. The human body has a limited capacity to rid itself of blood products in the subarachnoid space, but in ultra-rare cases, chronic or intermittent bleeding over the years to decades eventually leads to overwhelming amounts of toxic free-iron molecules.
These toxic free-iron molecules are curbed by a protein called ferritin which together forms a layer of hemosiderin around the brain, brain stem, spinal cord, and optic nerves. Long-term exposure is toxic to the tissue underneath resulting in hearing loss, imbalance, dizziness, weakness, numbness and bowel/bladder dysfunction.
Although easily identified by magnetic resonance imaging (MRI), superficial siderosis is often confused for other progressive neurological conditions such as multiple sclerosis, Parkinson’s, or multiple system atrophy.
- Due to the severe nature of the disease, in 2018 the Social Security Administration added superficial siderosis to the Compassionate Allowance list of conditions that allows for the fast-tracking of disability claims.
- Infratentorial superficial siderosis classic symptoms are ataxia, sensorineural hearing loss, and myelopathy. An estimated 95% of patients will experience hearing loss.
- In 2014 there were only an estimated 100 confirmed cases in the United States with 270 published studies worldwide since the beginning of the 20th century. Now identifiable by improvements in magnetic resonance imaging (MRI), the number of confirmed cases of infratentorial superficial siderosis patients in the U.S is rising. Dr. Michael Levy, a neurologist, is currently working on a standardized MRI diagnostic protocol.
- Researchers have identified the presence of cortical superficial siderosis as an early imaging indicator for patients at risk for dementia or Alzheimer’s disease. Unlike infratentorial superficial siderosis, those diagnosed with cortical superficial siderosis will not experience the same debilitating symptoms. Cortical superficial siderosis hemosiderin deposition is limited to cortical sulci over the convexity of the cerebral hemispheres, sparing the brain stem, cerebellum, and spinal cord.
- The neural damage may be permanent, and disability will continue to progress even if an active bleed source is repaired. Studies have identified oral chelation drug therapy with the ability to cross the blood-brain barrier to be the only option to slow or stop the degeneration.
How does Superficial Siderosis develop?
As individual blood cells travel through your subarachnoid space they begin to rupture through a process called Hemolysis. The bursting of cell walls creates a heme overload that triggers the Bergman Glia and Microglial cells to fight back by producing the enzyme heme oxygenase-1. This enzyme breaks down the heme and results in the release of free iron molecules, carbon dioxide, and biliverdin. Your body converts biliverdin into bilirubin and routes it out of your body through your liver. Glial cells manufacture ferritin which binds to the free iron.
Eventually, the ferritin bound free-iron molecules attach themselves by forming a layer of hemosiderin on the subpial layer that covers the nooks and crannies of your brain, brain stem, spinal cord, and surrounding tissue. Gravity comes into play. Laying down or sleeping positions the cerebellum to become a prime target. Walking or sitting upright makes your spine at risk the remainder of the day. Cranial nerve sections that run through your craniospinal fluid also may become covered in hemosiderin. This long-term exposure to free-iron molecules is toxic and may result in neural damage, cerebellar atrophy, and neurodegeneration.