Retinal Axonal Loss Begins Early in the Course of
Multiple Sclerosis and Is Similar between Progressive
Jeffrey M. Gelfand1, Douglas S. Goodin1, W. John Boscardin2, Rachel Nolan1, Ami Cuneo1, Ari J. Green1*
1University of California, San Francisco Department of Neurology, Multiple Sclerosis Center, University of California San Francisco, San Francisco, California, United States
of America, 2Departments of Medicine and Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, United States of America
Background: To determine whether retinal axonal loss is detectable in patients with a clinically isolated syndrome (CIS), a
first clinical demyelinating attack suggestive of multiple sclerosis (MS), and examine patterns of retinal axonal loss across MS
Methodology/Principal Findings: Spectral-domain Optical Coherence Tomography was performed in 541 patients with MS,
including 45 with high-risk CIS, 403 with relapsing-remitting (RR)MS, 60 with secondary-progressive (SP)MS and 33 with
primary-progressive (PP)MS, and 53 unaffected controls. Differences in retinal nerve fiber layer (RNFL) thickness and macular
volume were analyzed using multiple linear regression and associations with age and disease duration were examined in a
cross-sectional analysis. In eyes without a clinical history of optic neuritis (designated as ‘‘eyes without optic neuritis’’), the
total and temporal peripapillary RNFL was thinner in CIS patients compared to controls (temporal RNFL by 25.4 mm [95% CI
20.9 to 29.9 mm, p=0.02] adjusting for age and sex). The total (p=0.01) and temporal (p=0.03) RNFL was also thinner in
CIS patients with clinical disease for less than 1 year compared to controls. In eyes without optic neuritis, total and temporal
RNFL thickness was nearly identical between primary and secondary progressive MS, but total macular volume was slightly
lower in the primary progressive group (p,0.05).
Conclusions/Significance: Retinal axonal loss is increasingly prominent in more advanced stages of disease – progressive
MS.RRMS.CIS – with proportionally greater thinning in eyes previously affected by clinically evident optic neuritis. Retinal
axonal loss begins early in the course of MS. In the absence of clinically evident optic neuritis, RNFL thinning is nearly
identical between progressive MS subtypes.
Citation: Gelfand JM, Goodin DS, Boscardin WJ, Nolan R, Cuneo A, et al. (2012) Retinal Axonal Loss Begins Early in the Course of Multiple Sclerosis and Is Similar
between Progressive Phenotypes. PLoS ONE 7(5): e36847. doi:10.1371/journal.pone.0036847
Editor: Friedemann Paul, Charite ´ University Medicine Berlin, Germany
Received January 3, 2012; Accepted April 16, 2012; Published May 23, 2012
Copyright: ? 2012 Gelfand et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Investigators were supported by: NIH KL2 RR 024130 (AJG), T32 MH 090847 and American Academy of Neurology Clinical Research Training Fellowship
(JMG). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have read the journal’s policy and have the following conflicts: Jeffrey Gelfand: Dr. Gelfand has received honoraria from the
National MS Society for patient education and has received compensation for writing for Journal Watch Neurology. Douglas Goodin: Consultant for Teva, Novartis
and Serono, Advisor/Consultant for Bayer. W. John Boscardin: Nothing to disclose. Rachel Nolan: Nothing to disclose. Ami Cuneo: Nothing to disclose. Ari Green:
Advisor to Novartis on the use of Optical Coherence Tomography in MS and Service on the Endpoint Adjudication Committee for Applied Clinical Intelligence/
Biogen-Idec. This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials.
* E-mail: AGreen@ucsf.edu
Axonal loss is thought to be a major contributor to long-term
disability in multiple sclerosis (MS).  Axonal loss is most
conspicuous in the later stages of MS, [2,3] but MR imaging
studies suggest that more widespread axonal injury probably
begins much earlier in the disease course. At the time of a first
clinical relapse (a clinically isolated syndrome or CIS), CIS
patients tend to have smaller gray matter volumes on magnetic
resonance imaging (MRI) [4,5] lower brain N-acetyl aspartate
levels (a spectroscopic marker of neuroaxonal injury)  and
greater whole brain atrophy on MRI [7,8] compared to controls
without MS. Patients with early relapsing-remitting MS also
exhibit lower gray and white matter fractional volumes on MRI
than unaffected controls.  Such MRI findings may not be
entirely attributable to axonal loss, however, as brain atrophy
could reflect loss of non-neuronal cells (which constitute about half
of all cells in the human brain and over two-thirds of cells in
human cortical white matter),  neocortical demyelinating
lesions can potentially confound segmentation algorithms, [11,12]
and low NAA levels can indicate reversible axonal dysfunction in
the absence of frank axonal degeneration. 
The retina provides an attractive site for assessing axonal loss in
MS, [3,14] as the retinal nerve fiber layer (RNFL) is composed
almost entirely of axons. Retinal nerve fiber layer thickness can be
quantified using optical coherence tomography (OCT), a non-
invasive technique in which the backscatter of infrared light is used
to generate cross-sectional images. [15,16] Previous studies in MS
have demonstrated thinning of the RNFL and a reduction in
macular volume, most prominently in eyes previously affected by
optic neuritis. [3,14,17,18,19,20,21,22,23,24] RNFL thinning in
PLoS ONE | www.plosone.org1 May 2012 | Volume 7 | Issue 5 | e36847
MS appears to progress over time, [25,26] and is associated with
greater disease severity  and greater cortical gray matter
While brain imaging measures suggest that axonal injury occurs
early in the course of MS, including in patients with a CIS, [4,7]
previous work using time-domain OCT did not detect retinal
axonal loss in patients with a CIS. [29,30] There are at least three
possible explanations for this apparent inconsistency between
brain MRI and retinal OCT: 1) retinal pathology in MS may not
reflect pathology in the rest of the brain; 2) MRI metrics may be
confounded by involvement of non-neuronal structures; and/or 3)
the lower spatial resolution of earlier-generation time-domain
OCT methods may have made it harder to detect differences in
retinal thickness early in the disease course. Newer spectral-
domain (SD)-OCT techniques enable faster image acquisition and
improved image registration, permitting greater reproducibility
and accuracy. 
We hypothesized that retinal axonal loss occurs early in the
course of MS. In this cross-sectional analysis, we examined
whether RNFL thickness measured using SD-OCT differs
between patients with high-risk CIS and unaffected controls.
Another question that remains unsettled in the literature is
whether retinal axonal thinning differs between patients with the
primary progressive and secondary progressive phenotypes of MS.
Some previous studies using time-domain OCT found no
significant RNFL thinning in PPMS compared to patients with
relapsing MS, [19,24] while another study reported prominent
RNFL thinning and macular volume loss in both primary and
secondary progressive MS.  In this analysis, we also examined
whether SD-OCT patterns of RNFL thinning differ between
patients with primary progressive and secondary progressive MS.
Finally, point estimates of RNFL thickness in MS vary greatly in
the literature, [17,32] making it challenging to calculate the
sample sizes necessary when using OCT as an outcome in clinical
trials of neuroprotective and neurorestorative therapies. For this
reason, we also examined how SD-OCT measures of retinal
axonal thickness differ by disease stage and subtype.
In summary, the two major questions we examine using this
large cross-sectional dataset of retinal SD-OCT measures in MS
are: 1) Is RNFL thinning detectable in patients with a CIS, the first
clinical stage of MS?, and 2) Does retinal axonal loss differ
between the primary progressive and secondary progressive
phenotypes of MS?
All patients age 18 and older with a high-risk CIS or MS (by
2005 International Panel Criteria)  imaged using SD-OCT at
the UCSF MS center between January 2008 and October 2011
were considered for inclusion in this study. Patients were excluded
from analysis if a disease other than MS better explained their
symptoms or if there was a history of glaucoma, diabetes, uveitis,
age-related macular degeneration, retinal disease, severe myopia
(as measured by a 26 or stronger prescription) or a cataract
significant enough to affect OCT quality. Unaffected controls were
recruited from the community and included some spouses and
friends of patients with MS. All participants provided written
informed consent, and the UCSF Committee on Human Research
approved the study protocol.
MS stage and subtype (CIS, RRMS, SPMS and PPMS) were
established by the treating MS specialist and confirmed by study
investigators (JMG and AJG) through chart review. A CIS was
defined as a first monosymptomatic clinical demyelinating attack
typical of MS without evidence of dissemination in time.  In
order to enrich the CIS group for patients at highest risk of
progressing to MS,  CIS patients with at least one T2
hyperintensity typical of demyelination on conventional brain
MRI were considered to be ‘‘high-risk’’ and were included for
analysis.  A prior episode of symptomatic demyelinating optic
neuritis was diagnosed when there was a history of a subacute
episode of visual blurring or visual loss associated with eye pain
and when this event was confirmed by medical record review and
subject interview. Age was measured at the time of the OCT
evaluation. Disease duration was defined as the time from the first
clinical symptom attributable to MS to the SD-OCT examination.
The Expanded Disability Score Scale (EDSS),  was deter-
mined by the treating MS specialist and confirmed by the study
investigators through record review.
High contrast visual acuity was measured using a computerized
Early Treatment Diabetic Retinopathy Study (ETDRS) chart
(ProVideo system, INNOVA Systems, Burr Ridge, Illinois) and
analyzed using the logarithm of the Minimum Angle of Resolution
(LogMAR) scale. Low contrast vision was assessed using a
computerized chart (ProVideo system) at 20/200 measuring the
lowest contrast level at which subjects could read letters. Scoring
for low contrast vision was assigned on a 5 to 100 point scale with
5 points given for every step-up in low-contrast ability (i.e.
100 points for reading at 1.2% contrast and 5 points for best
reading ability at 100% contrast). Color vision was assessed using
Hardy-Rand-Rittler plates (scored as the number correct out of 19
Spectral-Domain Optical Coherence Tomography
SD-OCT was performed using the Spectralis OCT platform
(Heidelberg Engineering, Heidelberg, Germany), which performs
up to 40,000 A scans per second using an 870 nm bandwidth light
source. SD-OCT retinal thickness scans were obtained by a
trained technician and replicated three times by a single operator
within a single session. Correction for spherical errors was adjusted
prior to each measurement. The peripapillary RNFL was
measured at a distance of 3.4 mm from the center of the papilla.
For peripapillary B-scans, 0 degrees was defined as the nasal-most
edge of the disc. The nasal quadrant RNFL was defined as the
region between 315 and 45 degrees and the temporal quadrant
RNFL as the region between 135 and 225 degrees. For macular
volume measurements, 20615 degree raster scans were performed
consisting of 19 high-resolution line scans. Scans with insufficient
signal to noise or edge detection or retinal thickness algorithm
failure were excluded and measurements were repeated until good
quality was achieved.
Multiple linear regression was used to examine differences in
RNFL thickness (total RNFL, temporal RNFL and nasal RNFL)
and macular volume between groups, adjusting for age and sex.
To account for possible inter-eye correlations when two eyes from
the same patient were included in the model, the standard error
was adjusted using the clustered sandwich estimator. Possible
modification of the association between age or disease duration
and retinal thickness outcomes by disease subtype was assessed by
including interaction terms for age or disease duration with disease
subtype in the regression models. A p-value of 0.05 or less was
considered to be statistically significant. Statistical analyses were
Retinal Axonal Loss in Multiple Sclerosis
PLoS ONE | www.plosone.org2May 2012 | Volume 7 | Issue 5 | e36847
performed using Stata 12 (StataCorp, College Station, TX).
Figures were generated using GraphPad Prism 5.
541 patients with MS or CIS met inclusion criteria, including 45
patients with high-risk CIS; 403 with relapsing-remitting (RR)MS;
60 with secondary-progressive (SP)MS; and 33 with primary-
progressive (PP)MS. Within the high-risk CIS group, 22 patients
had a clinical disease duration of less than 1 year (40 eyes were
studied in this group) and 8 of the CIS patients presented with
optic neuritis as the first clinical symptom. A comparison group of
53 unaffected controls was also studied. Table 1 lists baseline
demographic and clinical information for each patient population.
Table 2 lists retinal SD-OCT measures categorized by MS stage
and subtype and optic neuritis history, together with measures of
high and low contrast visual acuity and color vision testing.
Retinal Nerve Fiber Layer Thinning is Detectable in
Patients with a Clinically Isolated Syndrome, the Earliest
Clinical Stage of MS
In the eyes of CIS patients without prior symptomatic optic
neuritis, the total RNFL was thinner compared to unaffected
controls, and was especially thin in the temporal peripapillary
region (the temporal RNFL was thinner by 5.4 mm [95% CI 20.9
to 29.9 mm, p=0.02] adjusting for age and sex). There was no
difference in macular volume between CIS patients and controls.
The total and temporal RNFL were thinner in the subgroup of
CIS patients with clinical disease for less than one year compared
to controls (the total RNFL was 6 mm thinner than controls [95%
CI 21.5 to 210.6 mm, p=0.01] and the temporal RNFL was
6.3 mm thinner than controls [95% CI 20.7 to 211.9, p=0.028,
adjusting for age and sex). There were no differences in total,
temporal or nasal RNFL thickness or macular volume between the
eyes of CIS patients without optic neuritis and fellow eyes of CIS
patients with a history of unilateral optic neuritis. Follow-up
information about disease activity was available for 36 of the CIS
patients – 7 were subsequently diagnosed with relapsing-remitting
MS by International criteria.  There were no differences in
baseline total, temporal or nasal RNFL thickness or total macular
volume between CIS patients who subsequently developed RRMS
and those who remained categorized as CIS when analyzing all
eyes or restricting the analysis to eyes without prior symptomatic
RNFL Thickness Is Similar in Primary and Secondary
Progressive MS in Eyes Without Prior Optic Neuritis
There was no meaningful difference in age between the PPMS
and SPMS groups (p=0.89). RNFL thickness was clinically
indistinguishable between patients with PPMS and SPMS in eyes
without a history of symptomatic optic neuritis (see Figure 1 and
Tables 1 and 2). Color-coded scatter plots of temporal RNFL
thickness by age (Figure 2A) and disease duration (Figure 2B)
illustrate how PPMS and SPMS non-optic neuritis eyes exhibit
similar amounts of RNFL loss, but how this occurs earlier in the
clinical duration of disease in patients with PPMS. Total macular
volumes were lower in patients with PPMS compared to SPMS in
eyes without optic neuritis (the macular volume was 0.10 mm3
lower in the PPMS group [95% CI .002–0.19 mm3, p=0.046,
adjusting for age and sex]).
Temporal-Predominant RNFL Thinning in MS is Most
Pronounced In Advanced Stages of Disease, Even in Eyes
Previously Affected by Symptomatic Optic Neuritis
In general, compared to controls, eyes with a prior history of
optic neuritis demonstrated thinning of the retinal nerve fiber
layer, most conspicuously and severely in the temporal quadrant,
which contains fibers of the papillomacular bundle (Figure 1,
Tables 1 and 2). A similar pattern of temporal-predominant
peripapillary RNFL thinning was observed across MS subtypes in
eyes without prior symptomatic optic neuritis. RNFL thinning was
increasingly prominent in patients with more advanced stages of
the disease – SPMS.RRMS.CIS – and most pronounced in
eyes previously affected by symptomatic optic neuritis – SPMS
optic neuritis.RRMS optic neuritis.CIS optic neuritis. This
gradation persisted after adjusting for cumulative number of optic
neuritis episodes. This indicates that even in eyes previously
affected by symptomatic optic neuritis, advanced disease stage is
associated with proportionally greater retinal axonal thinning.
There was no apparent modification of the association between
age or disease duration and temporal RNFL thickness by disease
This study demonstrates that 1) retinal axonal thinning begins
early in the course of MS and independently of the occurrence of
symptomatic optic neuritis and 2) that in the absence of
symptomatic optic neuritis, RNFL thickness is nearly identical
between progressive MS subtypes.
Table 1. Demographics.
MSPrimary Progressive MS
Age Mean (SD) 34.6 (11.1)39.3 (10.2)**42.3 (11.1)**51.4 (10.7)**52 (11.8)**
Sex (% Female)5780**72*6845
Median (IQR) in years
–1 (0.3–2.5)6.7 (2.7–12.1) 13.5 (6.4–21.2)8.6 (4–11.7)
Status Scale (EDSS)
–1.5 (1–2)2 (1.5–3.5) 5.5 (4–6.5)5.5 (4–6.5)
**p,0.01 – Statistical differences refer to comparison with unaffected controls.
Retinal Axonal Loss in Multiple Sclerosis
PLoS ONE | www.plosone.org3May 2012 | Volume 7 | Issue 5 | e36847
Table 2. RNFL Thickness and Macular Volume by MS Stage and Subtype.
Eyes with Prior
Low Contrast Vision
Color Vision (HRR
Plates) (0–19 Scale)
Total RNFL Mean (SD) mm
Temporal RNFL Mean (SD)
Nasal RNFL Mean (SD) mm
Macular Volume Mean (SD)
**p,0.001. Statistical differences refer to comparison with healthy controls using linear regression to adjust for age and sex. The standard error was adjusted for possible intra-patient inter-eye correlations. CIS=Clinically Isolated
Syndromes, RRMS=Relapsing-Remitting Multiple Sclerosis, SPMS=Secondary Progressive Multiple Sclerosis, PPMS=Primary Progressive Multiple Sclerosis; RNFL=Retinal Nerve Fiber Layer.
Retinal Axonal Loss in Multiple Sclerosis
PLoS ONE | www.plosone.org4 May 2012 | Volume 7 | Issue 5 | e36847
Previous studies using time-domain OCT to examine retinal
axonal degeneration in CIS found no differences in retinal nerve
fiber layer thickness or macular volumes between CIS patients and
controls. [29,30] This may reflect differences in study populations,
differences in methodology or the lower spatial resolution of the
time-domain OCT technique used in these previous studies. Other
studies have reported greater retinal axonal thinning in patients
with MS compared to patients with CIS. [21,36]
Temporal-predominant peripapillary retinal nerve fiber layer
thinning is characteristic in MS, [3,19,20,27,37] and the
prominence of this pattern of RNFL thinning in CIS patients
indicates that temporal-predominant RNFL loss begins early in
the disease course. The cause of temporal-predominant RNFL
thinning in MS is unknown. The RNFL is made up primarily of
retinal ganglion cell axons. There are three main types of retinal
ganglion cells that synapse in the lateral geniculate nucleus – 1)
smaller parvocellular cells, which are distributed overwhelmingly
in the macula, 2) larger magnocellular cells, which are distributed
primarily in the retinal periphery, and 3) koniocellular cells, which
are distributed more diffusely and sparser in number.  On the
standard peripapillary OCT scan, the RNFL temporal to the optic
disc consists primarily of parvocellular axons within the papillo-
macular bundle that subserve central vision.  Autopsy studies
of the lateral geniculate nucleus in people who died with late stage
MS have demonstrated a selective loss of parvocellular (smaller-
sized) axons in the lateral geniculate nucleus in MS with relative
preservation of magnocellular (larger-sized) axons.  Autopsy
studies of the spinal cord in patients who died with MS have also
Figure 1. Retinal Axonal Degeneration in Multiple Sclerosis is Increasingly Prominent in More Advanced Stages of Disease and
Proportionally Greater in Eyes Previously Affected by Symptomatic Optic Neuritis. Retinal Nerve Fiber Layer thickness (A, B, C) and
macular volume (D), as measured by spectral-domain optical coherence tomography (Heidelberg Spectralis) in a cross sectional sample of patients
with high-risk Clinically Isolated Syndromes (CIS) (n=45), Relapsing-Remitting MS (RRMS) (n=403), Secondary-Progressive MS (SPMS) (n=60),
Primary-Progressive MS (PPMS) (n=33) and unaffected controls (n=54). Both the total and temporal peripapillary RNFL were thinner in CIS patients
compared to controls in eyes without prior symptomatic optic neuritis. RNFL measures were nearly identical between SPMS and PPMS patients in
eyes without optic neuritis, but macular volumes were lower in PPMS compared to SPMS patients in eyes without optic neuritis (p,0.05). The black
dots denote the median, and the bars signify the interquartile range. *p,0.05, **p,0.001 refers to the comparison with unaffected controls using linear
regression to adjust for age and sex.
Retinal Axonal Loss in Multiple Sclerosis
PLoS ONE | www.plosone.org5 May 2012 | Volume 7 | Issue 5 | e36847
revealed a loss of smaller-sized axons in the lateral cortical spinal
tracts of the cervical and thoracic spinal cord, with relative
preservation of larger-sized axons.  Whether smaller sized
axons are more vulnerable to injury in MS is unknown. It is also
possible that smaller sized axons may remyelinate less efficiently
than larger sized axons following demyelinating injury, given
evidence from in vitro models of remyelination in which axonal
scaffold size appears to be a critical determinant of oligodendro-
cyte precursor cell differentiation.  More research is needed to
understand the cause of temporal-predominant thinning in MS.
In the absence of prior symptomatic optic neuritis, RNFL
thickness was nearly identical between patients with progressive
MS subtypes. These results differ from previous studies using time-
domain OCT that found no significant retinal thinning in PPMS
 and no difference in retinal thickness between PPMS and
other types of MS , and are consistent with the findings of
another study using time-domain OCT that found prominent
RNFL and macular volume loss in progressive MS.  These
results add to the mounting evidence of phenotypic similarities
between PPMS and SPMS. Measures of genetic susceptibility to
MS are similar between patients with primary and secondary
progressive phenotypes of disease,  as are measures of global
brain tissue damage and magnetization transfer imaging.  The
median age at time of disease progression was also indistinguish-
able between primary and secondary progressive MS patients in a
large French population-based study, as was the time it took to
reach major disability milestones.  In our study, macular
volumes were slightly lower in patients with primary MS
compared to eyes without prior ON in secondary progressive
MS patients. One possible interpretation of this result is that there
may be a proportionally greater loss of other neuronal elements in
the inner and outer retina in primary progressive disease. Future
studies using segmentation algorithms will be helpful in exploring
this possibly further.
Strengths of our analysis include the large sample size, which
allows for more reliable point estimates for the observed values of
retinal thickness at different stages of MS and the higher spatial
resolution of the spectral domain OCT technique used in this
study compared to time-domain OCT techniques used in some
previous studies.  While the cross-sectional study design
precludes comparison of differential rates of change over time
across MS subtypes, it is also advantageous for examining
associations with retinal thickness and disease stage over the
lifetime of disease, as MS typically evolves over decades. One
possible limitation of our analysis is that the control group was
slightly younger than the disease group, which could bias the
results, although we attempted to adjust for age using regression
This study demonstrates that retinal axonal thinning is
detectable in patients with a CIS; that retinal thinning is nearly
identical in patients with primary and secondary progressive MS
in eyes without prior symptomatic optic neuritis; and that RNFL
thinning is increasingly prominent in more advanced stages of
disease, even in eyes with prior symptomatic optic neuritis. These
findings support the possible utility of OCT as a marker of axonal
injury for trials of neuroprotective and neurorestorative therapies
in MS and support the idea that prevention of axonal injury is
relevant from the earliest clinical stages of disease.
Conceived and designed the experiments: JMG AJG. Performed the
experiments: JMG RN AC AJG. Analyzed the data: JMG DSG WJB RN
AC AJG. Wrote the paper: JMG DSG WJB AJG.
1. Trapp BD, Peterson J, Ransohoff RM, Rudick R, Mork S, et al. (1998) Axonal
transection in the lesions of multiple sclerosis. N Engl J Med 338: 278–285.
2.Bitsch A, Schuchardt J, Bunkowski S, Kuhlmann T, Bruck W (2000) Acute
axonal injury in multiple sclerosis. Correlation with demyelination and
inflammation. Brain 123(Pt 6): 1174–1183.
Figure 2. Associations of Temporal Retinal Nerve Fiber Layer Thickness by Disease Stage and Subtype with Age and Disease
Duration in MS. Temporal quadrant peripapillary retinal nerve fiber layer (RNFL) thickness by age (A) and disease duration (B) in MS patients in eyes
without a history of symptomatic optic neuritis. Note that temporal RNFL thickness is nearly identical between patients with primary and secondary
progressive MS, but disease durations tend to be greater in SPMS and shorter in PPMS for the same degree of RNFL loss. The solid line indicates the
slope as fitted by linear regression, and the dotted lines denote 95% confidence intervals. CIS=Clinically Isolated Syndrome; RRMS=Relapsing-Remitting
MS; PPMS=Primary Progressive MS; SPMS=Secondary Progressive MS.
Retinal Axonal Loss in Multiple Sclerosis
PLoS ONE | www.plosone.org6 May 2012 | Volume 7 | Issue 5 | e36847
3. Green AJ, McQuaid S, Hauser SL, Allen IV, Lyness R (2010) Ocular pathology Download full-text
in multiple sclerosis: retinal atrophy and inflammation irrespective of disease
duration. Brain 133: 1591–1601.
Fisher E, Lee JC, Nakamura K, Rudick RA (2008) Gray matter atrophy in
multiple sclerosis: a longitudinal study. Ann Neurol 64: 255–265.
Audoin B, Zaaraoui W, Reuter F, Rico A, Malikova I, et al. (2010) Atrophy
mainly affects the limbic system and the deep grey matter at the first stage of
multiple sclerosis. J Neurol Neurosurg Psychiatry 81: 690–695.
Wattjes MP, Harzheim M, Lutterbey GG, Klotz L, Schild HH, et al. (2007)
Axonal damage but no increased glial cell activity in the normal-appearing white
matter of patients with clinically isolated syndromes suggestive of multiple
sclerosis using high-field magnetic resonance spectroscopy. AJNR
Am J Neuroradiol 28: 1517–1522.
Brex PA, Jenkins R, Fox NC, Crum WR, O’Riordan JI, et al. (2000) Detection
of ventricular enlargement in patients at the earliest clinical stage of MS.
Neurology 54: 1689–1691.
Chen JT, Narayanan S, Collins DL, Smith SM, Matthews PM, et al. (2004)
Relating neocortical pathology to disability progression in multiple sclerosis
using MRI. Neuroimage 23: 1168–1175.
Chard DT, Griffin CM, Parker GJ, Kapoor R, Thompson AJ, et al. (2002) Brain
atrophy in clinically early relapsing-remitting multiple sclerosis. Brain 125:
10. Azevedo FA, Carvalho LR, Grinberg LT, Farfel JM, Ferretti RE, et al. (2009)
Equal numbers of neuronal and nonneuronal cells make the human brain an
isometrically scaled-up primate brain. J Comp Neurol 513: 532–541.
11. Calabrese M, De Stefano N, Atzori M, Bernardi V, Mattisi I, et al. (2007)
Detection of cortical inflammatory lesions by double inversion recovery
magnetic resonance imaging in patients with multiple sclerosis. Arch Neurol
12. De Stefano N, Matthews PM, Filippi M, Agosta F, De Luca M, et al. (2003)
Evidence of early cortical atrophy in MS: relevance to white matter changes and
disability. Neurology 60: 1157–1162.
13. Davie CA, Hawkins CP, Barker GJ, Brennan A, Tofts PS, et al. (1994) Serial
proton magnetic resonance spectroscopy in acute multiple sclerosis lesions. Brain
117(Pt 1): 49–58.
14. Frisen L, Hoyt WF (1974) Insidious atrophy of retinal nerve fibers in multiple
sclerosis. Funduscopic identification in patients with and without visual
complaints. Arch Ophthalmol 92: 91–97.
15. Blumenthal EZ, Parikh RS, Pe’er J, Naik M, Kaliner E, et al. (2009) Retinal
nerve fibre layer imaging compared with histological measurements in a human
eye. Eye (Lond) 23: 171–175.
16. Frohman E, Costello F, Zivadinov R, Stuve O, Conger A, et al. (2006) Optical
coherence tomography in multiple sclerosis. Lancet Neurol 5: 853–863.
17. Fisher JB, Jacobs DA, Markowitz CE, Galetta SL, Volpe NJ, et al. (2006)
Relation of visual function to retinal nerve fiber layer thickness in multiple
sclerosis. Ophthalmology 113: 324–332.
18. Burkholder BM, Osborne B, Loguidice MJ, Bisker E, Frohman TC, et al. (2009)
Macular volume determined by optical coherence tomography as a measure of
neuronal loss in multiple sclerosis. Arch Neurol 66: 1366–1372.
19. Henderson AP, Trip SA, Schlottmann PG, Altmann DR, Garway-Heath DF,
et al. (2008) An investigation of the retinal nerve fibre layer in progressive
multiple sclerosis using optical coherence tomography. Brain 131: 277–287.
20. Pulicken M, Gordon-Lipkin E, Balcer LJ, Frohman E, Cutter G, et al. (2007)
Optical coherence tomography and disease subtype in multiple sclerosis.
Neurology 69: 2085–2092.
21. Costello F, Hodge W, Pan YI, Freedman M, DeMeulemeester C (2009)
Differences in retinal nerve fiber layer atrophy between multiple sclerosis
subtypes. J Neurol Sci 281: 74–79.
22. Serbecic N, Aboul-Enein F, Beutelspacher SC, Graf M, Kircher K, et al. (2010)
Heterogeneous pattern of retinal nerve fiber layer in multiple sclerosis. High
resolution optical coherence tomography: potential and limitations. PLoS One
23. Kitsos G, Detorakis ET, Papakonstantinou S, Kyritsis AP, Pelidou SH (2011)
Perimetric and peri-papillary nerve fibre layer thickness findings in multiple
sclerosis. Eur J Neurol 18: 719–725.
24. Siepman TA, Bettink-Remeijer MW, Hintzen RQ (2010) Retinal nerve fiber
layer thickness in subgroups of multiple sclerosis, measured by optical coherence
tomography and scanning laser polarimetry. J Neurol 257: 1654–1660.
25. Talman LS, Bisker ER, Sackel DJ, Long DA, Galetta KM, et al. (2010)
Longitudinal study of vision and retinal nerve fiber layer thickness in multiple
sclerosis. Ann Neurol 67: 749–760.
26. Henderson AP, Altmann DR, Trip AS, Kallis C, Jones SJ, et al. (2010) A serial
study of retinal changes following optic neuritis with sample size estimates for
acute neuroprotection trials. Brain 133: 2592–2602.
27. Sepulcre J, Murie-Fernandez M, Salinas-Alaman A, Garcia-Layana A,
Bejarano B, et al. (2007) Diagnostic accuracy of retinal abnormalities in
predicting disease activity in MS. Neurology 68: 1488–1494.
28. Gordon-Lipkin E, Chodkowski B, Reich DS, Smith SA, Pulicken M, et al. (2007)
Retinal nerve fiber layer is associated with brain atrophy in multiple sclerosis.
Neurology 69: 1603–1609.
29. Outteryck O, Zephir H, Defoort S, Bouyon M, Debruyne P, et al. (2009) Optical
coherence tomography in clinically isolated syndrome: no evidence of subclinical
retinal axonal loss. Arch Neurol 66: 1373–1377.
30. Kallenbach K, Sander B, Tsakiri A, Wanscher B, Fuglo D, et al. (2011) Neither
retinal nor brain atrophy can be shown in patients with isolated unilateral optic
neuritis at the time of presentation. Mult Scler 17: 89–95.
31. Kiernan DF, Mieler WF, Hariprasad SM (2010) Spectral-domain optical
coherence tomography: a comparison of modern high-resolution retinal imaging
systems. Am J Ophthalmol 149: 18–31.
32. Parisi V, Manni G, Spadaro M, Colacino G, Restuccia R, et al. (1999)
Correlation between morphological and functional retinal impairment in
multiple sclerosis patients. Invest Ophthalmol Vis Sci 40: 2520–2527.
33. Polman CH, Reingold SC, Edan G, Filippi M, Hartung HP, et al. (2005)
Diagnostic criteria for multiple sclerosis: 2005 revisions to the ‘‘McDonald
Criteria’’. Ann Neurol 58: 840–846.
34. Fisniku LK, Brex PA, Altmann DR, Miszkiel KA, Benton CE, et al. (2008)
Disability and T2 MRI lesions: a 20-year follow-up of patients with relapse onset
of multiple sclerosis. Brain 131: 808–817.
35. Kurtzke JF (1983) Rating neurologic impairment in multiple sclerosis: an
expanded disability status scale (EDSS). Neurology 33: 1444–1452.
36. Costello F, Hodge W, Pan YI, Eggenberger E, Freedman MS (2010) Using
retinal architecture to help characterize multiple sclerosis patients.
Can J Ophthalmol 45: 520–526.
37. Kerrison JB, Flynn T, Green WR (1994) Retinal pathologic changes in multiple
sclerosis. Retina 14: 445–451.
38. Rizzo JF, III (2005) Embryology, Anatomy, and Physiology of the Afferent
Visual Pathway. In: Miller NR, Newman NJ, Biousse V, Kerrison JB, eds. Walsh
and Hoyt’s Clinical Neuro-ophthalmology. Philadelphia: Lippincott Williams &
Wilkins. pp 3–82.
39. Evangelou N, Konz D, Esiri MM, Smith S, Palace J, et al. (2001) Size-selective
neuronal changes in the anterior optic pathways suggest a differential
susceptibility to injury in multiple sclerosis. Brain 124: 1813–1820.
40. Ganter P, Prince C, Esiri MM (1999) Spinal cord axonal loss in multiple
sclerosis: a post-mortem study. Neuropathol Appl Neurobiol 25: 459–467.
41. Rosenberg SS, Kelland EE, Tokar E, De la Torre AR, Chan JR (2008) The
geometric and spatial constraints of the microenvironment induce oligodendro-
cyte differentiation. Proc Natl Acad Sci U S A 105: 14662–14667.
42. Gourraud PA, McElroy JP, Caillier SJ, Johnson BA, Santaniello A, et al. (2011)
Aggregation of multiple sclerosis genetic risk variants in multiple and single case
families. Ann Neurol 69: 65–74.
43. Rovaris M, Bozzali M, Santuccio G, Ghezzi A, Caputo D, et al. (2001) In vivo
assessment of the brain and cervical cord pathology of patients with primary
progressive multiple sclerosis. Brain 124: 2540–2549.
44. Confavreux C, Vukusic S (2006) Natural history of multiple sclerosis: a unifying
concept. Brain 129: 606–616.
Retinal Axonal Loss in Multiple Sclerosis
PLoS ONE | www.plosone.org7 May 2012 | Volume 7 | Issue 5 | e36847