RESULTS
The study was conducted with 130 eyes of 65 patients, 44 (67.7%) male
and 21 (32.3%) female, whose ages ranged from 18 to 59. The mean age
was 39.68 ± 9.99 years. The cases were divided into two groups as ”MS
Group” (n = 70) and ”Control Group” (n = 60). The duration of the
disease in the MS group ranges between 2 and 25 years, with a mean of
14.74 ± 5.85 years and a median of 15 years. According to MS types;
twenty-nine (44.6%) of the cases had RRMS and six (9.2%) had SPMS
type. There was no statistically significant difference between the
groups in terms of ONSD, SWE ON, SWE OD, and SWE perineural area levels
(p> 0.05). (Table 1).
In the MS group; there is no statistically significant difference
between patients with and without optic neuritis, in terms of mean age,
gender distribution, MS duration, MS types, ONSD, SWE ON, SWE OD, SWE
perineural area, and EDSS levels (p> 0.05). (Table 2).
There is no statistically significant difference in terms of ONSD, SWE
ON, SWE OD, and SWE perineural area between the MS patients with optic
neuritis and the control group (p> 0.05). (Table 3). There
is no statistically significant difference in terms of ONSD, SWE ON, SWE
OD, and SWE perineural area between the MS patients without optic
neuritis and the control group (p> 0.05). (Table 4)
DISCUSSION : MS is an autoimmune, chronic, inflammatory, and
demyelinating disease. While MS can lead to optical neuritis,
internuclear ophthalmoplegia, nystagmus, and saccadic dysmetria as
visual dysfunction, optic neuritis is the most frequently detected
one.15 It is often associated with severe visual loss.
Therefore, early diagnosis of optic nerve damage is extremely important.
Recently, ultrasonography has become an important adjuvant in the
evaluation of the optic nerve.16 We performed this
study considering that SWE can be an effective modality for evaluating
the optic nerve in the early diagnosis of optic neuritis due to
non-invasive and low-cost properties.
Volume loss and axonal damage in the retinal nerve fibers can be
observed in MS patients.15 The optic disc usually
appears normal but is mildly edematous in one-third of
cases.17 Also, autoimmune-related posterior uveitis or
vasculitis of the optic nerve in Wegener’s granulomatosis may cause
optic disc edema.18 This effect of autoimmune
pathologies on the optic disc may cause damage by similar mechanisms in
MS patients. The presence of the vascular network in the perineural area
may play a role in the development of optical neuritis by having immune
cells in this autoimmune inflammatory process.19 Thus,
we thought that the evaluation of the perineural area might be
beneficial and added this area to our research. In the literature, these
parameters have been evaluated with MRI in different
studies.20-22 However, there is no study in which all
three parameters were evaluated together on SWE.
In the literature, there is only one study evaluating sonoelastographic
findings in patients with MS, and only the optic nerve was evaluated in
this study.13 Besides, in another study; Batur et al.
evaluated both ON and retrobulbar tissue in patients with isolated optic
neuritis on SWE and reported that comparison of the normal eye with
isolated optic neuritis. The stiffness of the optic nerve in optic
neuritis was found higher than the contralateral normal optic nerve and
this difference was statistically significant.23 In
our study, we aimed to develop a different point of view; the optic disc
and perineural area were also evaluated in addition to the optic nerve,
and quantitative evaluation was made particularly on SWE to increase the
reliability of the study. Our study has been the first to evaluate all
these parameters together. Besides, we strengthened the clinical
effectiveness of our study by comparing our SWE measurements with the
EDSS score. EDDS is widely used in clinical trials and for the
assessment of MS. Since we thought the EDDS and sonoelastographic
parameters might have a relation, we also compared the SWE results with
the EDDS scores. Unfortunately, we could not find any significant
differences.
In Inal et al.’s study, the sonoelastographic changes in the optic nerve
in patients with MS were evaluated in terms of the elasticity of the
optic nerve based on the three main colorings in strain elastography
(SE) and SWE.13 According to this study, both SE and
SWE can be used to investigate inflammation in patients with MS and may
provide early diagnosis of optic neuritis. In our study, no
statistically significant difference was found in the comparison of the
optic nerve, optic disc, and perineural area SWE measurements between
the MS patients (with or without optic neuritis attack) and healthy
volunteers. According to these findings, our study results do not
support the results which they reported.
At this point, the disadvantages of SWE arise such as the difficulty of
the measurement technique and dependence on the operator. Optic nerve
diameter up to 5 mm is considered normal in a healthy
population.24,25 Inal et al. found that the mean optic
nerve diameter was 5.31 ± 0.48 mm (range, 3.8–6.5) in MS patients,
while this value was 5.22 ± 0.58 mm (range, 3.7–7) in healthy
volunteers. These findings support the concerns about the measurement.
In our study, this value was 3.03 ± 0.58 mm in the healthy population
and it was compatible with the information in the literature.
Optic neuritis may cause increased or decreased ONSD in the acute and
chronic phases.16,26,27 This may be an early and late
sign of optic neuritis. The hypothesis that optic nerve thickness and
stiffness may differ in optic neuritis with MS patients is the study’s
main purpose. However, we could not find any significant difference in
ONSD and SWE ON between patient groups with and without control and
optic neuritis. According to the optic neuritis stage, we anticipate
that non-classified patients may have led to these results.
One of the limitations of our study is that SWE is an operator-dependent
measurement method. Although our small size of the patient population
seems to be a problem, the prospective study design increases the
reliability of our results.