HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Correspondence to:

VIEWS & REVIEWS: N. Kumar, A. A. Cohen-Gadol, R. A. Wright, G. M. Miller, D. G. Piepgras, and J. E. Ahlskog Superficial siderosis Neurology 2006; 66: 1144-1152 [Abstract] [Full text] [PDF]

Correspondence: Submit a response to this article

Correspondence published:

Superficial siderosis

Mario Savoiardo, Elio Maccagnano, Davide Pareyson, and Marina Grisoli   (7 August 2006)

Reply from the Author

Neeraj Kumar   (7 August 2006)

Superficial siderosis 7 August 2006
Mario Savoiardo, Istituto Nazionale Neurologico Via Celoria 11, 20133 Milano, Italy, Elio Maccagnano, Davide Pareyson, and Marina Grisoli Send Correspondence to journal: Re: Superficial siderosis msavoiardo{at}istituto-besta.it Mario Savoiardo, et al.	We read with interest the article by Kumar et al and compliment the authors for their thorough review on the subject. [1] In the legend to Figure 1H, the authors state that hemosiderin deposition is present along the nerve roots of the cauda equina. We are not convinced that the signal intensity of the roots is low enough to demonstrate presence of hemosiderin. We have never seen MRI signs of siderosis on the nerve roots [2] even recently. As mentioned in the article, hemosiderin deposition can occur on the first and second cranial nerves, that are part of the central nervous system (CNS), and on the 8th cranial nerve because in this nerve the transition from central to peripheral myelin occurs even more than 1 cm away from the brainstem. In all other cranial nerves, the transition is within 1 or 2 mm, as occurs along the nerve roots entering or exiting the spinal cord. [3] Koeppen et al offered the explanation in several papers: the development of superficial siderosis requires an active process by the CNS glial cells, and therefore only occurs where there is central myelin. The ferritin repressor protein present in microglia, Bergmann glia and astrocytes promotes conversion of heme to ferritin and hemosiderin resulting in damage to the nervous tissue, perhaps through iron-catalyzed lipid peroxidation. [3,4] The phenomenon of superficial siderosis does not occur on peripheral myelin formed by the Schwann cells. In their seminal paper, Koeppen and Dentinger [3] state that "spinal roots were iron-negative and devoid of stainable ferritin". The best illustration of the "white" aspect of the nerve roots contrasting the dark spinal cord was presented by Friede in his book on developmental neuropathology and more recently reported with permission by us. [5] If siderosis of the cauda equina is now allegedly demonstrated by MRI, superficial siderosis would involve not only the CNS but also the peripheral nervous system. Therefore, we should hypothesize a new, different mechanism that might lead to deposition of hemosiderin on the peripheral myelin of the nerve roots of the cauda equina. Do the authors have an explanation or hypothesis in support for such a pathogenetic mechanism? Lastly, on Figure 2G, we do not recognize any vessel on the anterior surface of the spinal cord. The line indicated by the arrows is probably the anterior dural sheet. References 1. Kumar N, Cohen-Gadol AA, Wright RA, Miller GM, Piepgras DG, Ahlskog JE. Superficial siderosis. Neurology 2006;66:1144-1152. 2. Bracchi M, Savoiardo M, Triulzi F, et al. Superficial siderosis of the CNS: MR diagnosis and clinical findings. AJNR Am J Neuroradiol 1993;14:227 -236. 3. Koeppen AH, Dentinger MP. Brain hemosiderin and superficial siderosis of the central nervous system. J Neuropathol Exp Neurol 1988;47:249-270. 4. Koeppen AH, Dickson AC, Chu RC, Thach RE. he pathogenesis of superficial siderosis of the central nervous system. Ann Neurol 1993;34:646-653. 5. Savoiardo M, Grisoli M, Pareyson D. Polyradiculopathy in the corse of superficial siderosis of the CNS. J Neurol 2001;248:1099-1100. Disclosure: The authors report no conflicts of interest.
Reply from the Author 7 August 2006
Neeraj Kumar, Mayo Clinic 200 First Street SW, Rochester, MN 55902 Send Correspondence to journal: Re: Reply from the Author kumar.neeraj{at}mayo.edu Neeraj Kumar	I agree with Savoiardo et al that the evidence provided by Koeppen et al eloquently illustrates that the phenomenon of superficial siderosis spares the spinal roots. [3,4] Equally compelling evidence is provided by the illustration published by Savoiardo et al. [5] It would therefore be unlikely that that Figure 1H indicates hemosiderin deposition along the cauda equina. I am grateful to the authors for bringing this to my attention. There was evidence of arachnoiditis of the roots of the cauda in Case 7 (Figure 1J). Arachnoiditis is recognized in superficial siderosis as being a secondary phenomenon. In an exhaustive review of reported patients with superficial siderosis, lower motor neuron signs were noted in 8% of patients and were likely due to arachnoiditis or root avulsion. [6] An anterior horn syndrome has been reported in association with superficial siderosis. [7] Anterior horn cell involvement by hemosiderin is known but typically there is limited neuronal fallout. [6] The motor root exit zone has been hypothesized to be an additional site of iron deposition that may result in a lower motor neuron pathology. [7] Case 26 illustrated in figure 2G likely did have prominent vessels in a more posterior location. A better illustration from the same patient has been published earlier. [8] References 6. Fearnley JM, Stevens JM, Rudge P. Superficial siderosis of the central nervous system. Brain 1995;118:1051-1066. 7. Turner B, Wills AJ. Superficial siderosis associated with anterior horn cell dysfunction. J Neurol Neurosurg Psychiatry 2002;72:274-275. 8. Wilden JA, Kumar N, Murali HR, Lindell EP, Davis DH. Unusual neuroimaging in superficial siderosis. Neurology 2005;65:489. Disclosure: The author reports no conflicts of interest.