Sensorineural Hearing Loss will affect the majority of Superficial Siderosis patients and can be one of the earliest 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. 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. ¹
As free iron settles and hemosideron attaches to the eighth cranial nerve degeneration slowly results in bilateral-asymmetric sloping sensorineural hearing loss. Bilateral-asymmetric is defined as while both sides of your hearing will be affected it will not be an identical loss. Sloping describes how 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 hearing loss will progress to complete deafness in a significant percentage of those affected.
Audiologists often misidentify superficial siderosis induced sensorineural hearing loss as presbycusis in the early stages. Recent professional audiology journals have published articles regarding superficial siderosis and the importance of audiologists taking the initiative to identify at risk patients by matching their symptoms with trauma or clinical events from their medical history.
The slowly progressive nature of its clinical presentation can take as little as two or as long as 30 years. Since such a large portion of the eighth cranial nerve is exposed to cerebrospinal fluid the central myelin and micro-glia are extreme at risk.The damage to specialized, impulse-conducting cells (neurons) resulting in neuronal loss to the eighth cranial nerve and possible compression of the vascular structure from gliosis is viewed as permanent.
Some patients have opted to undergo Cochlear Implants with excellent success. Patients showing intact and functioning brainstem auditory conduction have proven a good predictor of cochlear implant success.