Introduction
Superficial siderosis, which was first reported by Hamill in 1908,Reference Hamill1 is a rare progressive disease of the central nervous system resulting from subarachnoid haemorrhage. Trauma and/or neurosurgery are the major causes of subarachnoid haemorrhage, although almost 50 per cent of superficial siderosis cases have unknown aetiology.Reference Sugimoto, Ito, Hatano and Yoshizaki2 The male-to-female ratio of superficial siderosis is 3:1. The age at onset of the symptoms varies from 14 to 77 years, with a mean age at onset of 44 years.Reference Sugimoto, Ito, Hatano and Yoshizaki2 Superficial siderosis can cause: sensorineural hearing loss (SNHL), in 95 per cent of patients; cerebellar ataxia, in 88 per cent; pyramidal signs, in 76 per cent; dementia, in 24 per cent; bladder disturbances, in 24 per cent; anosmia, in 17 per cent; and anisocoria, in 10 per cent. In addition, 13 per cent of superficial siderosis patients have sensory signs such as lower limb formication, diminished vibration sense and isolated loss of joint position sense.Reference Fearnley, Stevens and Rudge3
Superficial siderosis is caused by haemosiderin deposits on the cerebellar surface, brainstem surface and ventricular margins. They are shown as low-density regions on T2-weighted magnetic resonance imaging (MRI) scans because of the magnetic susceptibility effects of iron.Reference Grisoli, Maccagnano, De Simone and Savoiardo4, Reference Koeppen, Hurwitz, Dearborn, Dickson, Borke and Chu5 In the histopathological study of human temporal bone, hearing loss in a patient with superficial siderosis is most likely correlated with severe degeneration of spiral ganglion cells, despite the presence of remaining hair cells in the middle and apical turns of the cochlea.Reference Nadol, Adams and O'Malley6
Sensorineural hearing loss in superficial siderosis patients is usually treated with hearing aids. However, hearing aids are not effective for patients with severe hearing loss, and cochlear implants may be called for in such patients. Only 31 cases of superficial siderosis treated with cochlear implantation for SNHL have been reported. Even so, there is an ongoing debate regarding the effectiveness of cochlear implantation in superficial siderosis patients.Reference Modest, Carlson, Wanna and Driscoll7 In addition, to the best of our knowledge, there have been no reports evaluating the quality of life in superficial siderosis patients with a cochlear implant. This study assessed the quality of life of a superficial siderosis patient with bilateral progressive SNHL based on a Japanese-language translation of the Abbreviated Profile of Hearing Aid Benefit inventory,Reference Cox and Alexander8 and shows the clinical course of cochlear implantation.
Case report
The patient was a 38-year-old male. From his early twenties, he had bilateral progressive SNHL. At age 28 years, he began to use hearing aids in both ears. At age 29 years, the patient presented to a hospital with a chief complaint of bilateral motor disturbances in his extremities, and was subsequently diagnosed with superficial siderosis based on an MRI scan of the head. At age 37 years, the patient experienced an acute exacerbation of hearing loss in his right ear. He visited a hospital and was administered prednisolone, loop diuretic and vitamin B12 for 10 days. However, the hearing loss continued to progress, and an audiometric evaluation showed bilateral, nearly symmetric, severe SNHL. He was referred to our hospital for cochlear implantation.
An audiogram showed bilateral profound SNHL (Figure 1). The accuracy rate in a speech discrimination test using monosyllables was 0 per cent at 80 dB HL. There was no response (wave V disappears) in both ears at 90 dB HL in auditory brainstem response testing. There were no significant findings in computed tomography scans of the bilateral temporal bone. We could find the VIIIth cranial nerve by MRI. He had bilateral motor disturbances in his extremities, but no sensory disturbances. He could walk on crutches for short distances, but usually used a wheelchair. There was no cognitive disability, speech disability or other symptoms.
Fig. 1 Pre-operative audiogram. [ = bone conduction (masked) right ear; ] = bone conduction (masked) left ear; ○ = air conduction (unmasked) right ear; × = air conduction (unmasked) left ear
Cochlear implantation was performed using a Nucleus® CI422, with all active electrodes inserted into the right cochlea through the round window membrane. The patient had a good clinical course, with no complications following the procedure. There was significant improvement in his hearing three months after implantation (Figure 2).
Fig. 2 Sound field threshold with a cochlear implant (CI) three months after surgery.
Five months after the cochlear implant surgery, we evaluated the patient's quality of life based on a Japanese-language translation of the Abbreviated Profile of Hearing Aid Benefit inventory. The ease of communication, reverberation and background noise scores without a cochlear implant were 91.0 per cent, 84.8 per cent and 80.8 per cent, respectively. In contrast, the scores with a cochlear implant were 72.8 per cent, 60.7 per cent and 47.7 per cent, respectively. The aversiveness score was 18.5 per cent without a cochlear implant and 33.3 per cent with a cochlear implant (Figure 3).
Fig. 3 Abbreviated Profile of Hearing Aid Benefit scores with and without a cochlear implant (CI). EC = ease of communication; RV = reverberation; BN = background noise; AV = aversiveness
Discussion
Superficial siderosis is a rare condition characterised by recurrent subarachnoid bleeding. Haemosiderin deposits in the leptomeninges, subpial tissue, spinal cord, brainstem and/or the VIIIth cranial nerve result in eventual demyelination.Reference Yamana, Suzuki and Kitano9 Common clinical findings of superficial siderosis include SNHL, ataxia, dementia, anosmia and myelopathy; SNHL is one of the more frequent complaints.Reference Fearnley, Stevens and Rudge3, Reference Dodson, Sismanis and Nance10 The cause of the recurrent subarachnoid haemorrhages is not known in about 50 per cent of superficial siderosis cases.Reference Fearnley, Stevens and Rudge3 Superficial siderosis is difficult to manage, and there is no established treatment for the progressive neurological conditions, including SNHL, caused by iron deposition in the central nervous system.
To the best of our knowledge, there have been 31 reported cases of cochlear implantation for superficial siderosis, including 1 bilateral cochlear implant case (Table I).Reference Sugimoto, Ito, Hatano and Yoshizaki2, Reference Nadol, Adams and O'Malley6, Reference Modest, Carlson, Wanna and Driscoll7, Reference Irving and Graham11–Reference Ryan, Piplica and Zhang25 The existing literature indicates uncertainty regarding the efficacy of cochlear implantation in superficial siderosis patients who have SNHL. Wood et al. reported that two patients with superficial siderosis had limited benefit from cochlear implants one week and six months post-implantation.Reference Wood, Bird, Giles and Baber17 Previously, retrocochlear diseases affecting the central auditory pathway were considered a contraindication to cochlear implantation. However, a recent study reported on the clinical utility of cochlear implants in patients with superficial siderosis despite central nervous system involvement.Reference Modest, Carlson, Wanna and Driscoll7 Superficial siderosis is considered a retrocochlear disease, but, as is shown in Table I, many cases indicate the positive benefits of cochlear implants. In the present study, cochlear implantation resulted in remarkable improvement of the patient's audiometric threshold, and improvement in quality of life was quantified by his Abbreviated Profile of Hearing Aid Benefit score.
Table I Reported cases of cochlear implantation for sensorineural hearing loss in superficial siderosis patients
Y = years; CI = cochlear implant; mth = month; F = female; SNHL = sensorineural hearing loss; M = male; NR = not reported; L = left; R = right
The Abbreviated Profile of Hearing Aid Benefit inventory, a shortened version of the Profile of Hearing Aid Benefit inventory, is a 24-item self-assessment questionnaire in which patients report on their difficulties with communication and/or noise in various everyday situations. Although the Abbreviated Profile of Hearing Aid Benefit inventory was originally used to measure the effect of hearing aids, it is also useful in evaluating cochlear implants.Reference Buchman, Dillon, King, Adunka, Adunka and Pillsbury26 The Abbreviated Profile of Hearing Aid Benefit inventory contains four subscales: ease of communication, reverberation, background noise and aversiveness. Lower ease of communication, reverberation and background noise scores, and a higher aversiveness score indicate a better quality of life.
• Superficial siderosis is a very rare disease that often leads to progressive sensorineural hearing=loss
• A superficial siderosis patient's quality of life was quantitatively evaluated
• Cochlear implantation improved their quality of life
• Although hearing loss related to superficial siderosis is progressive, cochlear implantation can improve such patients' quality of life
Differences in Abbreviated Profile of Hearing Aid Benefit scores for this patient, associated with whether the implant was turned on or off, were checked for significance using the rules developed by Cox and Alexander.Reference Cox and Alexander8 The changes (more than 11 per cent) in each score (ease of communication, 91.0 per cent without a cochlear implant, 72.8 per cent with a cochlear implant; reverberation, 84.8 per cent without a cochlear implant, 60.7 per cent with a cochlear implant; background noise, 80.8 per cent without a cochlear implant, 47.7 per cent with a cochlear implant; and aversiveness, 18.5 per cent without a cochlear implant, 33.3 per cent with a cochlear implant) indicated that the cochlear implant made a very positive contribution to his quality of life. He is satisfied with the effect of the cochlear implant, and now enjoys musical concerts. Improvements to his quality of life associated with the cochlear implant could be quantitatively assessed using the Abbreviated Profile of Hearing Aid Benefit inventory. Although some unsuccessful cases of implantation have been reported, both audiological and social benefits can be expected from cochlear implants for superficial siderosis patients with SNHL.Reference Ryan, Piplica and Zhang25
Conclusion
To the best of our knowledge, this is the first report to assess the quality of life of a superficial siderosis patient with profound, bilateral, acquired hearing loss with and without a cochlear implant. Cochlear implantation is a promising therapeutic approach for progressive SNHL in superficial siderosis patients. It is also useful for enhancing quality of life. Wood et al. reported that patients with progressive neural deterioration of retrocochlear pathways might lose the benefits of cochlear implantation.Reference Wood, Bird, Giles and Baber17 Although gliosis, demyelination and neuronal loss in the central nervous system are usually progressive, cochlear implants may play a beneficial role in the management of SNHL in superficial siderosis patients.
