N-acetylaspartate concentration in the chiasm measured by in vivo proton magnetic resonance spectroscopy.
OBJECTIVE
To measure the concentration of N-acetylaspartate (NAA) in the chiasm of both normal controls and patients with chiasmal optic neuritis by in vivo proton magnetic resonance spectroscopy (1H-MRS).


METHODS
Ten normal subjects (age range, 22 to 40 years; mean, 31 years; seven men and three women) and two patients with chiasmal optic neuritis were examined at the Sapporo Medical University Hospital. Localized 1H-MRS spectra of the chiasm were obtained using a whole-body 1.5-T magnetic resonance system.


RESULTS
1H-MRS spectra of the chiasm were obtained in all subjects. The level of NAA concentration in the optic chiasm was 15.73 +/- 1.43 mM (mean +/- SD) in normal subjects. In contrast, the NAA levels in the two patients with chiasmal optic neuritis were significantly lower (P < 0.001). The level of NAA in the two patients was significantly increased after improvement of visual acuity and visual fields following corticosteroid pulse therapy.


CONCLUSIONS
These results suggest that 1H-MRS enables us to estimate the concentration of NAA in the chiasm. The NAA concentration in the optic nerve measured by 1H-MRS may be a new clinical parameter to monitor the axonal damage following optic neuritis.
Department of Ophthalmology, School of Medicine, Sapporo Medical University, Sapporo, Japan. mashoyu5@beige.plala.or.jp
Masato
M
Hashimoto
Kenji
K
Ohtsuka
Kuniaki
K
Harada
D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism*; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008775:Methylprednisolone / Q000008:administration & dosage; D008875:Middle Aged; D009897:Optic Chiasm / Q000378:metabolism*; D009902:Optic Neuritis / Q000188:drug therapy / Q000378:metabolism*; D011522:Protons; D020551:Pulse Therapy, Drug; D014794:Visual Fields
D005938:Glucocorticoids; D011522:Protons; D001224:Aspartic Acid; C000179:N-acetylaspartate; D008775:Methylprednisolone