Janica E. Walden, MD
UNC
Division of Neuroradiology
 Refers to the widespread rust-brown discoloration of
the surface of the CNS, secondary to hemosiderin
deposition.
 Hemosiderin is deposited in the subpial layers of the
brain and spinal cord, along the leptomeninges, and
along the subependyma of the ventricles.
 Hemosiderin deposition is a result of recurrent and
persistent bleeding into the subarachnoid space.
 Superficial hemosiderin deposition may be
accompanied by reactive gliosis, neuronal loss, and
demyelination.
 Recurrent SAH induces intracellular uptake of iron.
 Microglia, superficial astrocytes, and cerebellar
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Bergmann cells take up subarachnoid blood.
Intracellularly the heme is broken down into free iron
Free iron upregulates ferritin production, which
sequesters iron.
Ferritin biosynthesis is then overwhelmed by large
iron load, resulting in excess free iron.
Excess free iron may stimulate lipid peroxidation and
production of reactive oxygen species, leading to
localized tissue necrosis.
 Microglia and Bergmann glia uniquely sensitive to
iron-mediated cell damage
 Terminal processes of Bergmann glia that interface
with the SAS mediate iron uptake from the CSF,
inducing ferritin synthesis in these cells
 Ferritin sequesters iron but eventually overloaded
 Preferential involvement of CN VIII likely due to its
extensive lining with central myelin (supported by
siderosis-susceptible microglia).
 Also likely due to its course through the prepontine
cistern, exposing the nerve to abundance of iron
 Macroscopically, dark brown discoloration of
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leptomeninges, superficial CNS parenchyma, and
subependymal lining.
Leptomeninges are thickened
Varying degrees of neuronal loss, reactive gliosis, and
dymyelination.
Superficial folia of the cerebellum almost always involved
with loss of Purkinje cells and Bergmann gliosis.
CN VIII (sometimes CN’s I and II) exhibit dense
hemosiderin accumulation.
 Sometimes associated with demyelination and atrophy.
 No source in approximately 46% of patients
 Vascular abnormalities
 AVM’s, aneurysms, fragile capillary regrowth after brain
surgery
 Neoplasms
 Ependymomas, oligodendrogliomas, astrocytomas
 Trauma
 Cervical nerve root avulsions
 Progressive, bilateral sensorineural hearing loss (95%)
 Ataxia (88%)
 Pyramidal signs (76%)
 Occasionally, dementia, bladder incontinence,
anosmia, anisocoria, and sensory deficits.
 Men affected more than women (3:1)
 Analysis of CSF intermittently may show
xanthochromia, elevated red blood cell count, and
elevated iron and ferritin levels.
 In the past superficial siderosis was diagnosed almost
exclusively at autopsy.
 Advent of MRI facilitated in vivo diagnosis, and
indicated that SS is more common than previously
thought.
 T2WI and gradient echo susceptibility imaging
demonstrates characteristic hypointensity along the
pial surface/subarachnoid space of the brain and
spinal cord as well as ependyma of the ventricles
 Due to the paramagnetic nature of hemosiderin
 Less extensive, partially corresponding hyperintense rim
may be seen on T1WI
 May be due to presence of blood breakdown products at
different stages of evolution
 Tissue damage secondary to SS may be detected as atrophy
and signal intensity abnormality
 Findings are characteristically along the surface of the
brain stem and cerebellar vermis
 CN’s coated with hemosiderin detected by MR in only 25%
of cases
 Extent or distribution of siderosis doesn’t necessarily
correlate with severity of clinical disease.
Superficial siderosis
 Extra-arachnoid longitudinally oriented intraspinal
fluid collection frequently noted.
 Variably referred to as meningoceles,
pseudomeningoceles, diverticula, or epidural cyst
 Nerve root avulsions common association
 Within the spine, spinal cord atrophy common.
 Peripheralization or clumping of nerve roots may be
seen due to chronic SAH-related arachnoiditis.
 Management aimed at eliminating the cause of
recurrent SAH either by surgical or endovascular
treatment.
Superficial Siderosis
 Normal leptomeningeal melanin
 Variable thick hypointense rim on ventral surface of
medulla on T2WI, skin pigmentation
 MR sequence artifacts
 Meningioangiomatosis
 Rare benign lesion characterized by leptomeningeal
calcification and cortical meningovascular proliferation
 Coexistent NF in 50%
 Neurocutaneous melanosis
 Rare congenital phakomatosis
 Normal or abnormal brain surface venous structures
 Hsu Wendy C, Loevner Laurie A, Forman Mark S,
Thaler Erica R. Superficial Siderosis of the CNS
Associated with Multiple Cavernous Malformations.
AJNR 1999; 20: 1245-1248.
 Khalatbari Kimia. Case 141: Superficial Siderosis.
Radiology
 Kumar N. Neuroimaging in Superficial Siderosis: An
In-Depth Look. AJNR 2010; 31: 5-14.
 Nanda et al. Superficial siderosis-mechanism of
disease: an alternative hypothesis. Annals of Clinical
Biochemistry 2010; 47: 275-278.