Reduction of Retinal Thickness Ipsilateral to Hippocampal Sclerosis in Epilepsy

The thickness of the retinal nerve fiber layer, macula, and ganglion cell-inner plexiform layer in people with drug-resistant epilepsy

OBJECTIVE

Using Optical coherence tomography (OCT), we evaluated the association between peripapillary retinal nerve fiber, macular thickness, macular ganglion cell-inner plexiform layer, and drug resistance.

METHODS

In this cross-sectional study, we recruited people diagnosed with epilepsy and healthy controls. People with epilepsy were further stratified as drug-resistant or non-drug-resistant based on their response to anti-seizure medications. OCT measurements were conducted, and findings in right eye were analyzed.

RESULTS

Fifty-one drug-resistant participants, 37 non-drug-resistant, and 45 controls were enrolled. The average peripapillary retinal nerve fiber layer, ganglion cell-inner plexiform layer, and macular thickness were thinner in the epilepsy groups than in controls. The drug-resistant group had significantly lower average ganglion cell-inner plexiform layer thickness (p = 0.004) and a higher proportion of abnormal/borderline GC/IPL thickness (p = 5.40E-04) than the non-drug-resistant group. Nevertheless, no significant differences were seen between the average thickness of peripapillary retinal nerve fiber and macular thickness. The temporal sectors of these three parameters were also significantly thinner in the drug-resistant group than in the non-drug-resistant. In a multivariate regression model, drug resistance was an independent predictor of reduced ganglion cell-inner plexiform thickness (Odds ratios OR = 10.25, 95% CI 2.82 to 37.28). Increased seizure frequency (r = -0.23, p = 0.039) and a higher number of anti-seizure medications ever used (r = -0.27, p = 0.013) were negatively associated with ganglion cell-inner plexiform layer thickness.

SIGNIFICANCE

Individuals with drug-resistant epilepsy had a consistent reduction in average ganglion cell-inner plexiform layer thickness and the temporal sector of peripapillary retinal nerve fiber layer and macular thickness. This suggests that ganglion cell-inner plexiform layer thickness could potentially serve as an indicator of the burden of drug resistance, as it correlated with reduced thickness in individuals having more frequent seizures and greater exposure to ASMs.

PLAIN LANGUAGE SUMMARY

In our study, we used a special tool called OCT to measure how thick the retina is in people with epilepsy and in healthy control. We found that the retina was consistently thinner in all areas for those with epilepsy compared to healthy control. Particularly, a specific layer called the ganglion cell-inner plexiform layer was a lot thinner in the group that didn't respond to medications, and this thinning was related to how often seizures occurred and how much medications were taken. Also, certain parts of the retina were thinner in the drug-resistant group.

Association between retinal thickness and disease characteristics in adult epilepsy: A cross-sectional OCT evaluation

OBJECTIVE

Thinning of the peripapillary retinal nerve fiber layer (p-RNFL), as measured by optical coherence tomography (OCT), was recently introduced as a promising marker for cerebral neuronal loss in people with epilepsy (PwE). However, its clinical implication remains to be elucidated. We thus aimed to (1) systematically characterize the extent of the retinal neuroaxonal loss in a broad spectrum of unselected PwE and (2) to evaluate the main clinical determinants.

METHODS

In this prospective study, a spectral-domain OCT evaluation was performed on 98 well-characterized PwE and 85 healthy controls (HCs) (18-55 years of age). All inner retinal layers and the total macula volume were assessed. Group comparisons and linear regression analyses with stepwise backward selection were performed to identify relevant clinical and demographic modulators of the retinal neuroaxonal integrity.

RESULTS

PwE (age: 33.7 ± 10.6 years; 58.2% female) revealed a significant neuroaxonal loss across all assessed retinal layers (global pRNFL, P = 0.001, Δ = 4.24 μm; macular RNFL, P < 0.001, Δ = 0.05 mm3 ; ganglion cell inner plexiform layer, P < 0.001, Δ = 0.11 mm3 ; inner nuclear layer, INL, P = 0.03, Δ = 0.02 mm3 ) as well as significantly reduced total macula volumes (TMV, P < 0.001, Δ = 0.18 mm3 ) compared to HCs (age: 31.2 ± 9.0 years; 57.6% female). The extent of retinal neuroaxonal loss was associated with the occurrence and frequency of tonic-clonic seizures and the number of antiseizure medications, and was most pronounced in male patients.

SIGNIFICANCE

PwE presented an extensive retinal neuroaxonal loss, affecting not only the peripapillary but also macular structures. The noninvasive and economic measurement via OCT bears the potential to establish as a practical tool to inform patient management, as the extent of the retinal neuroaxonal loss reflects aspects of disease severity and sex-specific vulnerability.

PLAIN LANGUAGE SUMMARY

The retina is an extension of the brain and closely connected to it. Thus, cerebral alterations like atrophy reflect also on the retinal level. This is advantageous, as the retina is easily accessible and measureable with help of the optical coherence tomography. Here we report that adults with epilepsy have a significantly thinner retina than healthy persons. Especially people with many big seizures and a lot of medications have a thinner retina. We propose that measurement of the retina can be useful as a marker of disease severity and to inform patient management.