Optic coherence tomography (OCT) and visual evoked potential (VEP) assessment findings correlated with clinical measures of disability in patients with secondary progressive multiple sclerosis (SPMS), according to study findings published in the journal Multiple Sclerosis and Related Disorders.
This subtype of multiple sclerosis, SPMS, is characterized by progressively increasing neurological dysfunction in the absence of relapses or active inflammation. Visual involvement, especially in the form of optic neuritis, frequently occurs in patients with MS.
Researchers in Sweden conducted a quantitative, descriptive study of 27 patients (18 women, 9 men; mean age, 53 years; mean disease duration, 24 years) with SPMS who underwent OCT and VEP assessment at the department of neurology at Linköping University Hospital to determine the extent of optic involvement. A total of 15 patients were receiving disease modifying treatments, including rituximab (9 patients); interferon-beta (4 patients), naturalizumab (1 patient) and teriflumonide (1 patient). A control group of 48 healthy volunteers (33 women, 15 men; mean age, 49 years) underwent OCT and MRI scans, but not VEP examination.
The research objective was to compare the sensitivities of OCT and VEP in assessing the impact of MS on the visual pathways as well as to correlate these findings to clinical presentation and radiographic findings.
The researchers divided the eyes of the patients into 2 groups — MS optic neuritis eyes (MSON) and MS no history of optic neuritis (MSNON) eyes — based on their history of optic neuritis. History of optic neuritis was defined as:
- confirmed by an ophthalmologist,
- eye pain with vision loss followed by complete or partial recovery within weeks to months registered in clinical records, and an
- ophthalmologist’s examination suggesting optic neuritis was the cause of eye problems.
The researchers applied patient clinical assessments using the Expanded Disability Status Scale (EDSS) as a measure of SPMS disease severity. Magnetic resonance imaging (MRI) scans of the brain and spinal cord detected MS-related lesions.
They discovered that thickness of both the ganglion cell and inner plexiform layer (GCIPL) and the retinal nerve fiber layer (RNFL) on OCT correlated with VEP latency. GCIPL thickness and VEP latency also correlated with clinical presentation and disability levels as measured by the EDSS.
Patients in the MSON group had lower RNFL and GCIPL values than those in the MSNON group (P <.01). VEP P100 latency was significantly longer in individuals in the MSON group than in the MSNON group (P <.01), however, the amplitude did not significantly differ between the groups, the researchers noted. The eyes of patients in the MSON group had significantly higher VEP score than those in the MSNON group (P <.01)
Interestingly, since patients with SPMS do not experience relapses or show areas of active inflammation in the central nervous system, the MRI scans did not differ significantly between patients with SPMS and the healthy volunteers. This may indicate that MRIs may not be the optimal method of monitoring patients with SPMS compared with other more sensitive alternatives, such as OCT and VEP assessments.
“There was a good correlation between OCT and VEP, whereas there was no association to MRI findings indicating that OCT and VEP provide additional information to MRI and should be included in the follow-up of patients with SPMS,” the researchers concluded.
Study limitations included the small sample size, heterogeneity among patients, and lack of VEP examination in the control group.
Eklund A, Huang-Link Y, Kovácsovics B, Dahle C, Vrethem M, Lind J. OCT and VEP correlate to disability in secondary progressive multiple sclerosis. Mult Scler Relat Disord. Published online October 18, 2022. doi:10.1016/j.msard.2022.104255