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Superficial siderosis of the central nervous system.



Abstract

The term superficial siderosis siderosis /sid·er·o·sis/ (sid?er-o´sis)
1. pneumoconiosis due to inhalation of iron particles.

2. hyperferremia.

3. hemosiderosis.
 is used to describe the haemosiderin deposition on the surface of the brain, spinal cord, brainstem and cranial nerve leptomeninges leptomeninges /lep·to·me·nin·ges/ (lep?to-me-nin´jez) sing. leptome´ninx   the pia mater and arachnoid taken together; the pia-arachnoid.leptomenin´geal

lep·to·me·nin·ges
n.
 following recurrent subarachnoid subarachnoid /sub·arach·noid/ (sub?ah-rak´noid) between the arachnoid and the pia mater.
Subarachnoid
Referring to the space underneath the arachnoid mater.
 haemorrhage. The concern is the cytotoxic nature of the haemosiderin on the underlying tissue causing slow but progressive and irreversible neurological dysfunction. Removal of the source of bleeding has little effect on the progression of clinical deterioration but halting the chronic subarachoid haemorrhage will reduce the iron load in the CSF and hence the cytotoxic risk. We present a case of superficial siderosis presenting with hearing loss and cerebellar signs highlighting the imaging findings.

[FIGURES 1-2 OMITTED]

Introduction

Superficial siderosis describes the hemosiderin hemosiderin /he·mo·sid·er·in/ (he?mo-sid´er-in) an insoluble form of tissue storage iron, visible microscopically both with and without the use of special stains.

he·mo·sid·er·in
n.
 deposition on the surface of the brain, brainstem, cranial nerves and spinal cord following recurrent subarachnoid haemorrhage. The diagnosis can be made on MRI. The gradient echo sequence (GRE) best demonstrates the haemosiderin deposition on the surface of the brain1 and should prompt one to search for the cause of haemorrhage in order to prevent the irreversible neurotoxic effects on the underlying cortex.

Case report

This 44-year-old patient presented with a history of night sweats and malaise. He was observed to be inco-ordinate, had weakness of the left leg and changes in speech. Of significance is a history of two episodes of sudden loss of consciousness 6 months previously. He complained of hearing loss in his left ear.

On examination, he had upper limb cerebellar signs of intention tremor and disdiadocokinesis. He was also ataxic, demonstrated heel to shin ataxia, broad-based gait and was unable to tandem walk. The Rhomberg test was negative. The hearing loss was determined to be of the sensorineural type.

[FIGURES 3-4 OMITTED]

Laboratory investigations were normal including full blood count, iron studies, clotting profile, thyroid function test thyroid function test,
n one of several tests to evaluate the function of the thyroid gland. These include protein-bound iodine, butanol-extractable iodine, radioactive iodine uptake, and radioactive iodine excretion.
 and erythrocyte sedimentation rate Erythrocyte Sedimentation Rate Definition

The erythrocyte sedimentation rate (ESR), or sedimentation rate (sed rate), is a measure of the settling of red blood cells in a tube of blood during one hour.
. His cerebrospinal fluid (CSF) was xanthochromic and contained abundant red blood cells Red blood cells
Cells that carry hemoglobin (the molecule that transports oxygen) and help remove wastes from tissues throughout the body.

Mentioned in: Bone Marrow Transplantation

red blood cells 
.

The MRI scans are diagnostic of superficial siderosis of the brain and spinal cord (Figs 1-5). There is 'staining' or lining of the meningeal me·nin·ge·al
adj.
Of, relating to, or affecting the meninges.



meningeal

pertaining to the meninges.


meningeal hemorrhage
 surface of predominantly the cerebellum, brainstem and cord, but this may also include the sylvian fissures more superiorly. This is seen on T1, T2 and gradient echo sequences. Magnetic resonant angiography (MRA) and magnetic resonant venography Venography Definition

Venography is an x-ray test that provides an image of the leg veins after a contrast dye is injected into a vein in the patient's foot.
 (MRV) were normal. No intraparenchymal haemorrhage was noted.

Discussion

The term superficial siderosis is used to describe the haemosiderin deposition on the surface of the brain, spinal cord, brainstem and cranial nerve leptomeninges (1) following recurrent subarachnoid haemorrhage.

Patients present with a triad of progressive bilateral sensorineural hearing loss Sensorineural hearing loss
Hearing loss caused by damage to the nerves or parts of the inner ear governing the sense of hearing.

Mentioned in: Tinnitus

sensorineural hearing loss 
 (95%), cytotoxic consequences on the cerebellum of limb and gait ataxia and myelopathy myelopathy /my·elop·a·thy/ (mi?e-lop´ah-the)
1. any functional disturbance and/or pathological change in the spinal cord; often used to denote nonspecific lesions, as opposed to myelitis.

2.
. (2) All three occur in only 39% of patients with the sensorineural hearing loss most commonly manifested. (3) It leaves the patient almost totally deaf. Later, severe dementia, anosmia Anosmia Definition

The term anosmia means lack of the sense of smell. It may also refer to a decreased sense of smell. Ageusia, a companion word, refers to a lack of taste sensation.
, bladder disturbance (26%) and hyperreflexia (24%) occur. Our patient presented with cerebellar dysfunction and hearing loss.

As with all acute subarachnoid haemorrhage (SAH), the CSF demonstrates increased protein (100%) and is xanthochromic (75%) but can be normal as chronic subarachnoid haemorrhage can occur intermittently. (3)

The eighth cranial nerve eighth cranial nerve
n.
See vestibulocochlear nerve.


Vestibulocochlear nerve (Eighth cranial nerve)
Nerve that transmits information, about hearing and balance from the ear to the brain.
 is commonly affected as it has a long segment exposed to CSF (4) and is particularly well lined by myelin that is supported by haemosiderin-sensitive microglial cells. In addition, the eighth cranial nerve lies in the pontine cistern which is a large pool of CSF subjected to greater CSF flow. The result is greater axonal damage. The same theory applies to the susceptibility of the olfactory nerves to increased iron load. The second cranial nerve sec·ond cranial nerve
n.
See optic nerve.
 is entirely within the CNS and is thus spared from the damaging effects of this process.

This occurs three times more commonly in males and has a broad age range (14-77 years) of presentation.

The cause of the recurrent SAH is determined on imaging in only 50% of cases (3) and includes dural dural /du·ral/ (dur´'l) pertaining to the dura mater.

dural

pertaining to the dura mater.


dural ossification
see dural ossification.
 pathology, postsurgical CSF cavity with neovascularity, bleeding central nervous system (CNS) tumours (ependymoma, oligodendroglioma oligodendroglioma /ol·i·go·den·dro·gli·o·ma/ (-den?dro-gli-o´mah) a neoplasm derived from and composed of oligodendrocytes in varying stages of differentiation.

ol·i·go·den·dro·gli·o·ma
n.
 and astrocytoma astrocytoma /as·tro·cy·to·ma/ (as?tro-si-to´mah) a tumor composed of astrocytes; the most common type of primary brain tumor and also found throughout the central nervous system, classified on the basis of histology or in order of ), vascular malformations (arteriovenous malformations and cavernous malformation near the brain's surface), aneurysms, and in the spinal cord--tumours, arteriovenous malformations and traumatic nerve root avulsion The immediate and noticeable addition to land caused by its removal from the property of another, by a sudden change in a water bed or in the course of a stream.

When a stream that is a boundary suddenly abandons its bed and seeks a new bed, the boundary line does not change.
. (2)

Pathologically there is brown discoloration of the leptomeninges of the cerebellum (especially the vermis vermis /ver·mis/ (ver´mis) [L.] a wormlike structure, particularly the vermis cerebelli.

vermis cerebel´li  the median part of the cerebellum, between the two lateral hemispheres.
), basal frontal lobe, olfactory bulb, temporal cortex, brainstem, cranial nerves, spinal cord, nerve roots, ependyma ependyma /epen·dy·ma/ (e-pen´di-mah) the membrane lining the cerebral ventricles and the central canal of the spine.epen´dymal

ep·en·dy·ma
n. pl.
 and subpial tissue of < 3 mm deep. (1) The vermis of the cerebellum is particularly susceptible due to its close anatomical relation to the roof of the fourth ventricle and the compartmentalisation of CSF, therefore resulting in consistent increased exposure to CSF contents.

MRI can be used to make the diagnosis of superficial siderosis. The MRI GRE is the most sensitive, (1) and demonstrates thick dark signal lining the nervous system surfaces as a susceptibility artifact due to haemosiderin. This shows no enhancement. Because of the paramagnetic nature of haemosiderin, T1- and T2-weighted sequences demonstrate a blackened surface. (5) The seventh and eighth cranial nerves appear darker and thicker than normal.

Fluid attenuated inversion recovery (FLAIR) imaging suggests the diagnosis as the darker surface of the CNS and should prompt one to perform the GRE sequence. (3)

Once the diagnosis is made a search for the cause is indicated and includes contrast administration, MRA if an aneurysm is suspected and whole spine MRI.

The role of MRI is in the diagnosis of superficial siderosis, in terms of the easy detection of blood degradation products by GRE compared with computed tomography (CT), detecting a potentially treatable condition and avoiding unnecessary searches for other causes of hearing loss and ataxia. CT scan is relatively insensitive to the haemosiderin and may be suggested by a slightly hyperdense rim over the brain surface if the iron load is heavy. (3) It may demonstrate vermian atrophy and the underlying bleeding source.

[FIGURE 5 OMITTED]

The differential diagnosis includes: MRI sequence artifact seen on some but not all sequences, normal or abnormal surface veins, neurocutaneous melanosis melanosis /mel·a·no·sis/ (mel?ah-no´sis) melanism; disordered production of melanin, with darkening of the skin.

melanosis co´li
 or meningioangiomatosis. (1)

Neurocutaneous melanosis is a congenital syndrome consisting of benign pigmented cell tumour of the leptomeninges. It is suggested by the presence of a large congenital melanocytic nevus. Meningoangiomatosis is a rare benign focal lesion of the cerebellum and underlying cortex. The locality of the lesion, mixed signal characteristics and occasional contrast enhancement differentiates it from the diffuse nature of superficial siderosis.

Treatment is to treat the source of bleeding. There has been little success with iron or copper chelators as sole therapy. (4)

Conclusion

The imaging findings of superficial siderosis are a reflection of the recurrent subarachnoid haemorrhage. Careful inspection of the brain surface on T2 and FLAIR should prompt one to further imaging with GRE, contrast administration and MRA.

(1.) Osborn AG, Blaser SI, Salzman KL, et al. Diagnostic Imaging: Brain. Manitoba: Amirsys, 2004.

(2.) Feamley JM, Stevens JM, Rudge P. Superficial siderosis of the central nervous system. Brain 1995; 118: 1051-1066.

(3.) Levy M, Turtzo C, Llinas RH. Superficial siderosis: a case report and review of the literature. Nature Clinical Practice Neurology 2007; 3: 54-58.

(4.) Ushio M, Lwasaki S, Sugasawa K, et al. Superficial siderosis causing retrolabyrinthine involvement in both cochlear and vestibular branches of the 8th cranial nerve. Acta Oto-Laryngologica 126; 9: 997-1000.

(5.) Messori A, di Bella P, Herber N, et al. The importance of suspecting superficial siderosis of the central nervous system in clinical practice. J Neurol Neurosurg Psychiatry 2004; 75: 188-190.

Mayuri Govind, MB ChB, FCRad Diag (SA)

Department of Radiology, Inkosi Albert Luthuli Central Hospital, Durban

J Maharajh, MB ChB, FC Rad Diag (SA), MMed

Department of Radiology, Nelson R Mandela School of Medicine, and

University of KwaZulu-Natal, Durban
COPYRIGHT 2007 South African Medical Association
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Copyright 2007 Gale, Cengage Learning. All rights reserved.

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Title Annotation:CASE REPORT
Author:Govind, Mayuri; Maharajh, J.
Publication:South African Journal of Radiology
Geographic Code:6SOUT
Date:Dec 1, 2007
Words:1257
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