Sensorineural Hearing Loss will affect the majority of Superficial Siderosis patients and can be one of the first clinical symptoms to present.
The eighth cranial nerve is a sensory nerve with two main components: the vestibular nerve, which is responsible for balance, and the cochlear nerve, which is responsible for hearing.
it is especially sensitive to damage from superficial siderosis caused by the breakdown of slow or repeated episodes of subarachnoid hemorrhage into hemosiderin (Fig 13). It is postulated that the sensitivity of cranial nerve VIII to subpial hemosiderin deposition is due to its long cisternal segment, which exposes it to a high concentration of iron, in combination with the fact that the transition from central to peripheral myelin occurs near the IAC in cranial nerve VIII but relatively close to the brainstem in cranial nerves III–XII. The central myelin and the microglia that produce it are especially sensitive to siderosis. The high iron concentration lining the brain and cranial nerves will cause local magnetic inhomogeneity and is most easily visualized on susceptibility-weighted or gradient-echo T2*-weighted images (15,16). ¹
Hemosiderin and the associated free iron attaches to areas of the eighth cranial nerve slowly causing degeneration resulting in bilateral, asymmetric sloping sensorineural hearing loss. The high-frequency hearing will diminish first with lower frequency loss in the later stages as the disorder progresses. Unless hemosiderin deposits can be removed from the cranial nerve complete deafness is very likely.
Audiologists often misidentify SNHL as presbycusis in the early stages. The slowly progressive nature of its clinical presentation can take as little as ten or up to 30 years. The neuronal loss to the eighth cranial nerve and possible compression of the vascular structure from gliosis was thought to make hearing loss permanent. New advances in stem cell research may offer future opportunities for nerve repair.
Some patients have opted to undergo Cochlear Implants with excellent success.