Reply:
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* N. Kumar

I thank Drs Savoiardo and Grisoli for adding to my Review Article on neuroimaging in superficial siderosis by providing 3 MR imaging illustrations of olfactory nerve involvement in this condition. I agree that anosmia and impaired peripheral vision may be under-reported symptoms.

“CSF hypovolemia” would mean decreased volume of CSF, and this term is preferred to “craniospinal hypotension” because a reduced CSF pressure may not describe the pathophysiology of the spectrum of abnormalities noted with dural defects.1,2

Hereditary hemochromatosis is unlikely to cause neurologic manifestations.3 To my knowledge, there is limited information to confirm the suggestion that the hyperattenuation seen on head CT in some patients with superficial siderosis is due to iron and not calcium. High-definition x-ray fluorescence mapping and spectroscopy of siderotic spinal cord tissue has not shown the presence of calcium.4 In many patients with superficial siderosis, no abnormality is noted on CT. Furthermore, many of the conditions associated with primary brain iron accumulation (neurodegeneration with brain iron accumulation) do not have abnormalities on CT, despite striking changes on brain MR imaging, particularly on gradient-echo sequences.5

## References

1.  1. Mokri B. Spontaneous cerebrospinal fluid leaks: from intracranial hypotension to cerebrospinal fluid hypovolemia—evolution of a concept. Mayo Clin Proc 1999;74:1113–23
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.4065/74.11.1113&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=10560599&link_type=MED&atom=%2Fajnr%2F31%2F8%2FE73.atom) 
    
    [Web of Science](http://www.ajnr.org/lookup/external-ref?access_num=000083499500007&link_type=ISI) 

2.  2. Miyazawa K, Shiga Y, Hasegawa T, et al. CSF hypovolemia vs intracranial hypotension in “spontaneous intracranial hypotension syndrome.” Neurology 2003;60:941–47
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6OToibmV1cm9sb2d5IjtzOjU6InJlc2lkIjtzOjg6IjYwLzYvOTQxIjtzOjQ6ImF0b20iO3M6MTk6Ii9ham5yLzMxLzgvRTczLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

3.  3. Russo N, Edwards M, Andrews T, et al. Hereditary haemochromatosis is unlikely to cause movement disorders: a critical review. J Neurol 2004;251:849–52
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1007/s00415-004-0445-9&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=15258788&link_type=MED&atom=%2Fajnr%2F31%2F8%2FE73.atom) 

4.  4. Koeppen AH, Michael SC, Li D, et al. The pathology of superficial siderosis of the central nervous system. Acta Neuropathol 2008;116:371–82. Epub 2008 Aug 12
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1007/s00401-008-0421-z&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=18696091&link_type=MED&atom=%2Fajnr%2F31%2F8%2FE73.atom) 

5.  5. McNeill A, Birchall D, Hayflick SJ, et al. T2* and FSE MRI distinguishes four subtypes of neurodegeneration with brain iron accumulation. Neurology 2008;70:1614–19
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6OToibmV1cm9sb2d5IjtzOjU6InJlc2lkIjtzOjEwOiI3MC8xOC8xNjE0IjtzOjQ6ImF0b20iO3M6MTk6Ii9ham5yLzMxLzgvRTczLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

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