Temporal Bone Histopathology in a Case of Sensorineural Hearing Loss Caused by Superficial Siderosis of the Central Nervous System and Treated by Cochlear Implantation

Abstract

Objectives To evaluate the histopathology of the temporal bones of a patient with documented superficial siderosis of the central nervous system who underwent right cochlear implantation six years before death. Background Superficial siderosis of the central nervous system is due to chronic or repeated subarachnoid hemorrhage and results in sensorineural deafness in 95% of affected individuals in addition to other neurologic findings. The deposition of hemosiderin in the meninges and around cranial nerves is thought to be causative. There have been no previous reports of temporal bone pathology in this disorder. This 57 year old man developed progressive, bilateral hearing loss starting in his 30's with loss of pure tone thresholds and word recognition. He underwent a right cochlear implant at age 51 with full insertion of the device. Methods The temporal bones and brainstem were fixed in formalin and prepared for histologic study by standard techniques. Special stains, including Gomori stain for iron were performed on sections of the temporal bones and cochlear nucleus. Results There was severe bilateral degeneration of the organ of Corti, spiral ligament, stria vascularis, and spiral ganglion cells. Gomori stain revealed iron deposits within the spiral ligament, stria vascularis and in the subepithelial mesenchymal tissue of the maculae of the vestibular system. Evaluation of the cochlear nucleus revealed iron deposits within glial cells and larger cells, probably macrophages, near the CSF surface. On the right side, the track created by the cochlear implant entered the scala tympani and continued to mm17, as measured from the round window. Discussion and Conclusions This is the first known case of superficial siderosis with documented temporal bone histopathology. Hearing loss was likely caused by severe degeneration of spiral ganglion cells in both ears, despite the presence of remaining hair cells in the middle and apical turns. This was consistent with cochlear neuronal degeneration and retrograde degeneration of spiral ganglion cells within the inner ear, or alternatively, consistent with primary degeneration of hair cells and neural structures within the cochlea. Despite the presence of neural degeneration, the patient achieved a word recognition score of 28% six months following implantation.

Vestibular end organ injury induced by middle ear treatment with ferric chloride in rats

“…24 In the present study, middle ear treatment with 70% FeCl 3 caused loss of hair cells, atrophy of the neuroepithelial layer in the ampulla, and apoptosis of the hair cells, which are consistent with the results obtained from patients with superficial siderosis. 24 In the presence of Fe 2þ and Fe 3þ ions, intracellular H 2 O 2 and O 2 À can undergo the Fenton reaction, which increases the levels of hydroxyl radicals. The hydroxyl radical is highly reactive and is thought to be the ROS most responsible for oxidative damage.…”

Electrophysiological Detection of Intracochlear Scalar Changing Perimodiolar Cochlear Implant Electrodes

“…Subject NRT-XPA-112 (NRT ratio 1.00) had a history of hearing loss because of superficial siderosis of the central nervous system. Superficial siderosis is associated with the degeneration of spiral ganglion cells (19). It is not known to date whether spiral ganglion degeneration moves homogenously or inhomogenously along the cochlea.…”

Vestibular function in superficial siderosis

“…In addition, cochlear damage can cause the vestibular deficits of SS. Specifically, temporal bone histopathology has revealed the atrophy of the superior and inferior vestibular nerves and the loss of hair cells [16], and caloric tests have revealed hyporeflexia [17-23]. Fukiyama et al reported that one cause of impaired balance is damage to the inner hair cells by the deposition of hemosiderin in the inner ear.…”