Superficial Siderosis (NXPowerLite)
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Transcript Superficial Siderosis (NXPowerLite)
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
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
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.