Superficial Siderosis
Superficial siderosis is a rare neurological condition characterized by the deposition of hemosiderin, an iron-storage complex, in the subpial layers of the central nervous system (CNS). This deposition results from chronic or intermittent bleeding into the subarachnoid space, leading to the accumulation of iron and subsequent neuronal damage.[1][2][3]
Clinical Features
The clinical presentation of superficial siderosis typically includes progressive cerebellar ataxia, sensorineural hearing loss, and pyramidal/UMN tract signs. These symptoms are due to the toxic effects of iron on neural tissues, particularly affecting the cerebellum, brainstem, and spinal cord. It's likely the unbound free iron causing free-radical mediated injury when protective mechanisms are overwhelmed.
Superficial siderosis can also cause pain - the two primary pain syndromes are headache and radiculopathy.[4][5]
- Headache is a common symptom associated with superficial siderosis, occurring in about 30% of patients. This headache is often due to meningeal irritation caused by subarachnoid blood. A history of low-pressure headache (e.g. orthostatic headaches) can be a clue to an underlying dural tear and CSF leak.[1] See also CSF Leak.
- Radiculopathy or polyradiculopathy with associated radicular pain can manifest as pain along the distribution of affected nerves. This may be associated with lower motor neuron signs. This may be due to arachnoiditis or nerve root stretching by ventral fluid collections.[1]
Myelopathy can occur due to direct cord compression from herniation through a dural defect or dynamic compression by intraspinal fluid collections. This manifests as pyramidal signs, sensory changes, and bladder issues.
Aetiology
The most common etiologies include dural defects, often resulting from trauma or surgical procedures or disc disease, which lead to chronic cerebrospinal fluid (CSF) leaks and subsequent bleeding. Other causes can include vascular malformations, tumors, or idiopathic sources of bleeding.
A spinal dural abnormality (most often a tear) is the most common identifiable cause of classic superficial siderosis. Many cases previously deemed 'idiopathic' likely had undetected spinal dural defects.[1]
Many of the other causes are relevant to MSK Medicine:
- Disc herniations (often calcified).
- Spinal osteophytes (sometimes spiculated) causing dural injury.
- Trauma, including prior spinal surgery or brachial plexus avulsion injuries leading to pseudomeningoceles.
- Connective tissue disorders associated with dural ectasia.
Diagnosis
Diagnosis is primarily made through magnetic resonance imaging (MRI), which reveals characteristic hypointense signals on T2-weighted images due to hemosiderin deposition. Iron-sensitive sequences, such as susceptibility-weighted imaging (SWI), are particularly useful in detecting these deposits.
MRI: Ventral intraspinal fluid collections are common signs of a CSF leak from a ventral dural tear, often related to disc/osteophyte pathology. They can be subtle and misdiagnosed as prominent epidural veins. Besides the fluid collections, look for T2-hypointensity coating the spinal cord surface, cord atrophy, and signs of arachnoiditis like nerve root clumping/peripheralization.
CT Myelography: Often necessary to pinpoint the exact site of the dural tear/leak, especially dynamic CT myelography for high-flow leaks or when a long fluid collection is present. The "nuclear trail sign" on CT can indicate a prior disc herniation as the cause.
Treatment
Treatment focuses on identifying and addressing the source of bleeding. Surgical repair of dural defects can halt the progression of the disease. Pharmacological treatment with iron chelators like deferiprone has been explored, but current data are insufficient to recommend its routine use. Epidural blood patches are generally considered ineffective for these types of chronic/potentially high-flow leaks.
Resources
References
- ā 1.0 1.1 1.2 1.3 Kumar, Neeraj (2021-06). "Superficial Siderosis: A Clinical Review". Annals of Neurology (in English). 89 (6): 1068ā1079. doi:10.1002/ana.26083. ISSN 0364-5134. Check date values in:
|date=(help) - ā Kumar, N.; Cohen-Gadol, A. A.; Wright, R. A.; Miller, G. M.; Piepgras, D. G.; Ahlskog, J. E. (2006-04-25). "Superficial siderosis". Neurology (in English). 66 (8): 1144ā1152. doi:10.1212/01.wnl.0000208510.76323.5b. ISSN 0028-3878.
- ā Posti, Jussi P.; Juvela, Seppo; Parkkola, Riitta; Roine, Susanna (2011-10). "Three cases of superficial siderosis of the central nervous system and review of the literature". Acta Neurochirurgica (in English). 153 (10): 2067ā2073. doi:10.1007/s00701-011-1116-0. ISSN 0001-6268. Check date values in:
|date=(help) - ā Iannaccone, S.; Golzi, V.; Sferrazza, B.; de Rino, F.; Smirne, S.; FeriniāStrambi, L. (1999-10). "Central Nervous System Superficial Siderosis, Headache, and Epilepsy". Headache: The Journal of Head and Face Pain (in English). 39 (9): 666ā669. doi:10.1046/j.1526-4610.1999.3909666.x. ISSN 0017-8748. Check date values in:
|date=(help) - ā Friedauer, Lucie; Foerch, Christian; Steinbach, Joachim; Hattingen, Elke; Harter, Patrick N.; Armbrust, Moritz; Urban, Hans; Steidl, Eike; Neuhaus, Elisabeth; von Brauchitsch, Sophie (2022-03-22). "The Acute Superficial Siderosis Syndrome ā Clinical Entity, Imaging Findings, and Histopathology". The Cerebellum (in English). 22 (2): 296ā304. doi:10.1007/s12311-022-01387-3. ISSN 1473-4230. PMC 9985565. PMID 35316464.CS1 maint: PMC format (link)
