Sensorineural Hearing Loss

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Hearing Loss will affect 95% of Superficial Siderosis patients. Unexplained hearing loss or tinnitus will often be one of the earliest clinical symptoms of Superficial siderosis 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 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 hemosiderin attaches to the eighth cranial nerve, degeneration slowly results in bilateral-asymmetric sloping sensorineural hearing loss. Unless hemosiderin deposits can be removed from the cranial nerve, hearing loss will progress to complete deafness in a significant percentage of those affected.

Bilateral-asymmetric describes 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.

 

Audiologists often misidentify sensorineural hearing loss arising from Superficial siderosis as early-stage presbycusis. Recently professional audiology journals have published articles regarding Superficial siderosis. Audiologists’ importance in identifying at-risk patients by matching their symptoms with past trauma or clinical events from their medical history will facilitate early detection.

Its clinical presentation’s progressive nature may present as quickly as two or as long as 10 years. Since such a large portion of the eighth cranial nerve is exposed to cerebrospinal fluid, the central myelin and micro-glia are extremely at risk. The damage to specialized, impulse-conducting cells (neurons) resulting in neuronal loss to the eighth cranial nerve and possible vascular structure compression from gliosis is viewed as permanent.

Some patients have opted to undergo Cochlear Implants with excellent results. Determining, pre-procedure, if the patient has intact and functioning brainstem auditory conduction has proven a good predictor of cochlear implant success.

 

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Updated: November 9, 2020
Sources: Superficial siderosis is a rare neurologic disease characterized by progressive sensorineural hearing loss, cerebellar ataxia, pyramidal signs, and neuroimaging findings revealing hemosiderin deposits in the spinal and cranial leptomeninges and subpial layer. The disease progresses slowly, and patients may present with mild cognitive impairmentnystagmus, dysmetria, spasticity, dysdiadochokinesia, dysarthriahyperreflexia, and Babinski signs. Additional features reported include dementia, urinary incontinence, anosmia, ageusia, and anisocoria. Superficial siderosis MedGen UID: 831707 •Concept ID: CN226971 •Finding Orphanet: ORPHA247245
Living With SuperficialSiderosis Website PubMed Reference Library 
¹Neurologic/Head and Neck Imaging
Intracranial Causes of Ophthalmoplegia: The Visual Reflex Pathways
Seth T. Stalcup, August S. Tuan, John R. Hesselink
Author Affiliations
Published Online: Aug 30, 2013, https://doi.org/10.1148/rg.335125142

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