Relationship of optic nerve and brain conventional and non-conventional MRI measures and retinal nerve fiber layer thickness, as assessed by OCT and GDx: a pilot study.
BACKGROUND
Measurement of retinal nerve fiber layer (RNFL) thickness in multiple sclerosis (MS) is gaining increasing attention.


OBJECTIVE
To explore the relationship between RNFL thickness as measured by optical coherence tomography (OCT) and scanning laser polarimetry with variable corneal compensation (GDx), and conventional and non-conventional optic nerve and brain MRI measures.


METHODS
Twelve relapsing-remitting (RR) MS patients (12 affected and 12 unaffected eyes) and 4 age- and sex-matched normal controls (NC) (8 unaffected eyes) were enrolled. Four MS patients had a history of bilateral optic neuritis (ON), four had a history of unilateral ON, and 4 had no history of ON. Optic nerve MRI measurements included the length of T2 lesions, measurement of optic nerve atrophy, magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) measures. Optic nerve atrophy was measured by a novel method with high reproducibility. Brain MRI measurements included T1 and T2 lesion volumes (LVs) and their relative MTRs, and tissue class specific atrophy, MTR and DTI measures. Measures of RNFL were evaluated with OCT and GDx. We also evaluated both high and low contrast letter acuities (LCLA) in order to determine the relationship between vision, MRI metrics, and retinal structural architecture.


RESULTS
LCLA, RNFL-OCT and optic nerve radius measures showed more robust differences between NC and MS patients, and between MS patients with affected and unaffected eyes. T2-LV and T1-LV, as well as gray matter atrophy, DTI and MTR measures were related to LCLA and RNFL thickness. Unique additive variance regression models showed that both brain and optic nerve MRI measures independently accounted for about 50% of the variance in LCLA and RNFL thickness. In reverse models, about 20% of the additional independent variance was explained by optic nerve or brain MRI metrics.


CONCLUSIONS
Measurement of RNFL thickness and radius of the optic nerve should be preferred to the other optic nerve MRI measures in clinical studies. Whole brain lesion and GM measures are predictive of impaired visual function with corresponding structural concomitants.
Frohman
Elliot M
EM
Department of Neurology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235, USA. elliot.frohman@utsouthwestern.edu
Dwyer
Michael G
MG
Frohman
Teresa
T
Cox
Jennifer L
JL
Salter
Amber
A
Greenberg
Benjamin M
BM
Hussein
Sara
S
Conger
Amy
A
Calabresi
Peter
P
Balcer
Laura J
LJ
Zivadinov
Robert
R
D000328:Adult; D000704:Analysis of Variance; D001284:Atrophy / Q000473:pathology; D001921:Brain / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000150:complications / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D009902:Optic Neuritis / Q000150:complications / Q000473:pathology; D009929:Organ Size; D010865:Pilot Projects; D012044:Regression Analysis; D012160:Retina / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014787:Vision Tests