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|LETTERS TO EDITOR
|Year : 2018 | Volume
| Issue : 3 | Page : 839-840
The mysterious case of bilateral sensory neural hearing loss (superficial siderosis)
Pushpendra N Renjen, Dinesh Chaudhari
Department of Neurology, Indraprastha Apollo Hospitals, New Delhi, India
|Date of Web Publication||15-May-2018|
Dr. Pushpendra N Renjen
C-85, Anand Niketan, New Delhi - 110 021
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Renjen PN, Chaudhari D. The mysterious case of bilateral sensory neural hearing loss (superficial siderosis). Neurol India 2018;66:839-40
Superficial siderosis of the central nervous system (SSCN) is an unusual cause of progressive sensorineural hearing loss; however, bilateral sensory neural hearing loss (SNHL) is the most common clinical presentation of SSCN. Hemosiderin deposition along the leptomeninges, subpial tissues, and subependyma of the ventricles as a result of chronic and recurrent subarachnoid hemorrhage induces intracellular uptake of iron, leading to damage to the neural tissue.,, Traumatic cervical nerve root avulsions, as well as the presence of neoplasms and vascular abnormalities are some of the causes of siderosis. Nevertheless, in as many as 46% of the patients, no source for the siderosis is identified.,,,
A 35-year old male patient presented to our hospital with a 20-year history of gradual progressive bilateral hearing loss, which started in the left ear and worsened over the years; eventually the patient developed profound bilateral hearing loss. Few years after the onset of hearing loss, he started experiencing slurring and distortion of speech, which worsened significantly during the last 1 year. He denied any history of loss of smell, chronic recurrent headaches, spinal trauma, head injury, intracranial surgery, or excessive alcohol consumption. He had no positive family history of similar hearing or gait disturbances. He had sought medical opinion in many hospitals in different parts of the world, and series of neuroimaging as well as laboratory studies were conducted; however, no definite cause was found.
Neurological examination showed evidence of dysarthria with scanning speech, dysmetria, bilateral sensorineural deafness, abnormal heel-to-shin test, and unsteady gait with swaying to the left side. There was no clinical involvement of the pyramidal, extrapyramidal, or the autonomic system. Routine laboratory investigations as well as cerebrospinal fluid (CSF) cell analysis, serum iron studies, and serum ceruloplasmin were within normal limits. Pure tone audiometry (PTA) showed bilateral profound sensory-neural hearing loss (SNHL) whereas brainstem evoked response audiometry (BERA) showed bilateral SNHL involving the central brainstem auditory pathways more than the peripheral cochlea.
The T2-weighted [Figure 1] magnetic resonance (MR) images of the brain showed diffuse cerebellar atrophy with hemosiderin staining over the cerebellar and cerebral hemispheres and on the surface of brainstem, suggestive of superficial siderosis. The gradient echo (GRE) MR images showed the characteristic low signal with blooming effect of hemosiderin deposition.
|Figure 1: T2-weighted images of MRI brain showing hemosiderin staining over the cerebellar hemispheres and on the surface of brainstem, suggestive of superficial siderosis|
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The noncontrast computed tomography (CT) scan of the head revealed an expansile arachnoid cyst, 7.7 × 2.8 × 4.4 cm, in the midline of the occipital bone with a breech of the inner table. In view of the suspicion of the superficial siderosis in relation to the arachnoid cyst, a CT cisternography was performed. The CT cisternography revealed contrast enhancement in the subarachnoid space, and the expansile arachnoid cyst was likely explained by the dural tear that had led to extravasation of contrast from the subarachnoid space into the intradiploic space in occipital bone [Figure 2].
|Figure 2: (a) Non-contrast CT scan of the head showing an arachnoid cyst in the midline of occipital bone with a breech of the inner table. (b) CT cisternography demonstrating a dural tear that led to extravasation of contrast from the subarachnoid space into the intradiploic space in the occipital bone|
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The source of chronic subarachnoid bleed was found to be the erosion of the intradiploic space by the underlying expansile arachnoid cyst. The patient underwent a midline suboccipital craniotomy, decompression of the arachnoid cyst, and closure of dural opening with fascia lata graft. Lipid soluble oral iron chelator deferiprone was started in a low dose, and gradually the dose was increased with a close watch on the complete blood count and the liver function tests. The patient responded well to the surgery and the iron chelator. His hearing has improved significantly after 6 months of therapy. His gait has became steadier and his speech has also improved after the treatment.
Superficial siderosis of the central nervous system was first described in 1908 by R.C. Hamill. Its pathogenetic mechanism and clinical manifestations have been a matter of significant interest and there have been many reports in the neurology literature since the 1960s. However, the fact that bilateral sensory-neural hearing loss is the most common presentation of SSCN is still not so familiar to clinicians because it is a very rare disease and generally not described in neurological texts.,
Iron from red blood cells in the subarachnoid space is preferentially taken up by the Bergmann glia in the cerebellum, brainstem, spinal cord, eighth cranial nerve, and the cerebral cortex; iron is stored as ferritin within the glial cells. With continued subarachnoid bleeding, the glia are overwhelmed by the ferritin load and die. Their loss exposes neurons to free iron which is toxic to cells because it catalyzes the breakdown of hydrogen peroxide to superoxide, a reactive oxygen species that can cause lipid peroxidation, membrane dysfunction, and neuronal cell death. The eighth cranial nerve is the one that is most susceptible because it exposes the most surface area-to-volume. Thus, the most common and often the first symptom that the patients experience is sensorineural hearing loss.
Idiopathic bleeding is the major source of subarachnoid bleeding, accounting for 35% of all cases, which is followed by bleeding associated with tumors (15%), brain trauma (13%), and arteriovenous malformations (9%). In the present case, a high index of suspicion for the presence of superficial siderosis along with the specific imaging helped us in finding the source of chronic subarachnoid bleed, which was surgically corrected. The patient currently remains on deferiprone, and has shown a significant response to the treatment. In conclusion, every case of bilateral SNHL with an unknown cause should undergo hemosiderin-specific imaging. If the source of chronic subarachnoid bleed is found and corrected, the response to oral deferiprone (30 to 90 mg/kg/day) is significant.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]