White matter spectroscopy in neuromyelitis optica: a case control study.

Background: Naa/Cr ratio in normal appearing white matter (NAWM) of patients with multiple sclerosis (MS) is altered beyond plaques, suggesting early axonal loss, and correlates to clinical disability. Brain lesions not typical of MS have been described in Neuromyelitis optica (NMO), and correspond to brain aquaporin-4 channel sites, but the evaluation of Naa/Cr ratio in NAWM of patients with NMO and its association to the presence of brain lesions and clinical disability have not been described.

Objectives: To evaluate the Naa/Cr of normal appearing white matter (NAWM) in 16 patients with NMO compared to healthy controls.

Methods: We performed brain magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) of 16 patients with NMO and compared to age matched healthy controls.

Results: NAWM Naa/Cr did not show statistical difference among patients and controls, neither between patients that had normal brain MRI and atypical brain lesions.

Conclusion: NAWM was found to have a normal Naa/Cr in patients with NMO, reinforcing the concept that the white matter is not primarily affected in this disease.