Relation of vision to global and regional brain MRI in multiple sclerosis

Objective:

To examine the relation between low-contrast letteracuity, an emerging visual outcome for multiple sclerosis (MS)clinical trials, and brain MRI abnormalities in an MS cohort.

Methods:

T2 lesion volume and brain parenchymal fraction weredetermined for whole brain and within visual pathway regionsof interest. Magnetization transfer ratio histograms were examined.  Vision testing was performed binocularly using low-contrastletter acuity (2.5%, 1.25% contrast) and high-contrast visualacuity (VA).  Linear regression, accounting for age and diseaseduration, was used to assess the relation between vision andMRI measures.

Results:

Patients (n = 45) were aged 44 ± 11 years,with disease duration of 5 years (range <1 to 21),

ExpandedDisability Status Scale score of 2.0 (0 to 6.0), and

binocularSnellen acuity of 20/16 (20/12.5 to 20/25).

The average T2 lesionvolume was 18.5 mm³.

Patients with lower (worse) low-contrastletter acuity and high-contrast VA scores had greater T2 lesionvolumes in whole brain (2.5% contrast: p = 0.004; 1.25%: p =0.002; VA: p = 0.04), Area 17 white matter (2.5%: p < 0.001;1.25%: p = 0.02; VA: p = 0.01), and optic radiations (2.5%:p = 0.001; 1.25%: p = 0.02; VA: p = 0.007). Within whole brain,a 3-mm³ increase in lesion volume corresponded, on average,to a 1-line worsening of low-contrast acuity, whereas 1-lineworsening of high-contrast acuity corresponded to a 5.5-mm³ increase.

Conclusions:

Low-contrast letter acuity scores correlate wellwith brain MRI lesion burden in multiple sclerosis (MS), supportingvalidity for this vision test as a candidate for clinical trials.Disease in the postgeniculate white matter is a likely contributorto visual dysfunction in MS that may be independent of acuteoptic neuritis history.

Abbreviations:

BP = brain parenchymal;

BPF = brain parenchymal fraction;

DICOM = Digital Imaging and Communications in Medicine;

EDSS = Expanded Disability Status Scale;

ETDRS = Early Treatment Diabetic Retinopathy Study;

HIPAA = Health Insurance Portability and Accountability Act;

MS = multiple sclerosis; MSFC =

MS Functional Composite; OCT = optical coherence tomography;

PASAT = paced auditory serial addition test; ROIs = regions of interest;

VA = visual acuity.

From:

Departments of Neurology

Radiology and

Ophthalmology  

University of Pennsylvania School of Medicine,

Philadelphia, PA;

Department of Biostatistics

University of Alabama,

Birmingham, AL; and

Department of Neurology

The Johns Hopkins University School of Medicine,

Baltimore, MD.