We thank Dr. Aboul-Enein et al. for their interest about our recent paper. We apologize for the missing references. For the first one (Bichuetti et al.) we missed it in our pubmed research probably due to a misclassification of the key words. For the second one (Aboul-Enein et al.), the paper was not published before our article was in press. We are a little bit concern to include in our references abstract of posters. Many mistakes can be include in abstract form of poster that are frequently submitted quickly due to the deadline of the congress. It was the case concerning our poster explaining the differences between the abstract from Multiple sclerosis and our recent paper. Of course the right number of patients and controls is in the full paper. We think that the most important fact is that all the three papers are in the similar direction confirming that normal apparent white and grey matter are really normal in NMO evaluated by spectroscopy MR.

Conflict of Interest:

None declared

Sir,

we have read with great interest the paper by de Seze et al., entitled "Magnetic resonance spectroscopy evaluation in patients with neuromyelitis optica" (1).

Neuromyelitis optica (NMO) is a rare disease and most studies rely on a small sample size. Calling attention to previous publications on magnetic resonance spectroscopy (MRS) in patients with NMO might strengthen the results of de Seze et al. Bichuetti et al (2) and our group (3) achieved nearly identical results as found by de Seze et al.

Furthermore we performed chemical shift imaging MRS at 3 Tesla, a technique able to quantify absolute concentrations of the metabolites in the normal appearing white matter (NAWM) instead of metabolite ratios only.

De Seze et al and our group presented their data previously as posters at the same session of the 23th Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) in 2008 (3, 4). We were therefore aware of their data and find it confusing that metabolite ratios in the NAWM of NMO patients and healthy controls presented at ECTRIMS (3) were essentially the same as published in JNNP(1), while the number of NMO patients changed from 25 to 24, and the number of healthy controls from 15 to 12.

NMO is a rare disease and the number of patients included in studies is generally low. To overcome this limitation data for each patient should be traceable.

We would like to ask the authors to provide detailed information in order to explain these confusing data.

References:

1. de Seze J, Blanc F, Kremer S, et al. Magnetic resonance spectroscopy evaluation in patients with neuromyelitis optica. J Neurol Neurosurg Psychiatry. 2010; 81:409-11.

2. Bichuetti DB, Rivero RL, de Oliveira EM, et al. White matter spectroscopy in neuromyelitis optica: a case control study. J Neurol. 2008; 255:1895-9. Epub 2009 Jan 22.

3. Aboul-Enein F, Krssak M, Hoftberger R, Prayer D, Kristoferitsch W. Diffuse white matter damage is absent in neuromyelitis optica. AJNR Am J Neuroradiol. 2010; 31:76-9. Epub 2009 Sep 12.

4. de Seze J, Blanc F, Kremer S, et al. Magnetic resonance spectroscopy evaluation in patients with neuromyelitis optica. Multiple Sclerosis 2008; 14:S101-S101.

5. Aboul-Enein F, Krssak M, Jecel J, et al. Magnetic resonance spectroscopy in neuromyelitis optica. Multiple Sclerosis 2008; 14:S101- S101.

Conflict of Interest:

None declared

Dear Editor,

We read with interest the article written by de Seze et al(de Seze, Blanc et al. 2010), published on the April 2010 issue of the Journal of Neurology, Neurosurgery and Psychiatry. The authors describe a transversal investigational research comparing magnetic resonance spectroscopy (MRS) of NAWM and NAGM of 24 patients with NMO, 46% of whom had brain abnormalities, and 12 healthy subjects. In this study, the authors found no difference on Naa/Cr of NAWM and NAGM in patients with NMO comparing to healthy controls, an information that corroborates the idea that there is no silent and continuous degenerative process in the SNC tissues of patients with NMO(Wingerchuk, Pittock et al. 2007).

The authors state that they had no previous knowledge of MRS studies on NMO, so we would like to share our experience evaluating the NAWM of 16 patients with NMO and 16 age matched healthy control subjects. We described similar results, i.e., there was no difference in NAWM of patients and healthy volunteers(Bichuetti, Rivero et al. 2008). We also included patients with brain abnormalities and cautiously positioned the voxel away from brain lesions to avoid changes in the metabolic pattern of the spectrum in this region. We further evaluated 41 patients with relapsing NMO in order to clarify if the brain abnormalities seen on recent studies(Pittock, Lennon et al. 2006; Bichuetti, Rivero et al. 2008) correlate with a worse prognosis, and found that there is no different on annualized relapse rate and progression index between patients with or without brain abnormalities, in our cohort.(Bichuetti, Oliveira et al. 2009). We were not able to evaluate the impact of NMO-IgG positivity in our cohort since the test was not available in Brazil during the period we conducted the study.

We congratulate de Seze et al for their very interesting work and would like to encourage them and other investigators to look for their clinical data in order to search for clinical marker of disease severity, as well as MRI/clinical correlations.

Aboul-Enein, F., M. Krssak, et al. (2010). "Diffuse white matter damage is absent in neuromyelitis optica." AJNR Am J Neuroradiol 31(1): 76 -79.

Bichuetti, D., E. Oliveira, et al. (2009). "Neuromyelitis optica in Brazil: a study on clinical and prognostic factors." Mult Scler 15(5): 613 -619.

Bichuetti, D. B., R. L. Rivero, et al. (2008). "White matter spectroscopy in neuromyelitis optica: a case control study." J Neurol 255(12): 1895-1899.

Bichuetti, D. B., R. L. Rivero, et al. (2008). "Neuromyelitis optica: brain abnormalities in a Brazilian cohort." Arq Neuropsiquiatr 66(1): 1-4.

de Seze, J., F. Blanc, et al. (2010). "Magnetic resonance spectroscopy evaluation in patients with neuromyelitis optica." J Neurol Neurosurg Psychiatry 81(4): 409-411.

Pittock, S. J., V. A. Lennon, et al. (2006). "Brain abnormalities in neuromyelitis optica." Arch Neurol 63(3): 390-396.

Wingerchuk, D. M., S. J. Pittock, et al. (2007). "A secondary progressive clinical course is uncommon in neuromyelitis optica." Neurology 68(8): 603-605.

Conflict of Interest:

None declared