Transsynaptic Retrograde Degeneration: Clinical Evidence with Homonymous RGCL Loss on OCT

Homonymous Hemiatrophy of Macular Ganglion Cell Layer as a Marker of Retrograde Neurodegeneration in Multiple Sclerosis-A Narrative Review

Retrograde axonal neurodegeneration along the visual pathway-either direct or trans-synaptic-has already been demonstrated in multiple sclerosis (MS), as well as in compressive, vascular, or posttraumatic lesions of the visual pathway. Optical coherence tomography (OCT) can noninvasively track macular and optic nerve changes occurring as a result of this phenomenon. Our paper aimed to review the existing literature regarding hemimacular atrophic changes in the ganglion cell layer identified using OCT examination in MS patients without prior history of optic neuritis. Homonymous hemimacular atrophy has been described in post-chiasmal MS lesions, even in patients with normal visual field results. Temporal and nasal macular OCT evaluation should be performed separately in all MS patients, in addition to an optic nerve OCT evaluation and a visual field exam.

[OCT in Neuroophthalmology]

Optical coherence tomography (OCT) has become the most important innovation in ophthalmology over the last 30 years and is used routinely, especially in the diagnosis of retinal and glaucomatous diseases. It is fast, non-invasive and reproducible. Since the procedures can offer such a high resolution that the individual retinal layers can be visualised and segmented, this examination technique has also found its way into neuroophthalmology. Especially the peripapillary nerve fibre layer (RNFL) and the ganglion cell layer (GCL) provide valuable diagnostic and prognostic information in cases of visual pathway disease and morphologically unexplained visual disorders. OCT is helpful in determining the cause of optic disc swelling and EDI-OCT can reliably detect buried, non-calcified drusen. This article is intended to provide the reader with an overview of current and future applications of OCT in neuroophthalmology and knowledge of possible pitfalls.

Detailed Evaluation of Macular Ganglion Cell Complex in Patients with Multiple Sclerosis

Introduction:

Retinal nerve fiber layer thickness has been used for monitoring of disease activity in patients with multiple sclerosis (MS). Macular ganglion cell complex (GCC) layer of retina also can be measured by OCT and has been suggested as a potential biomarker in MS. In this study we investigated the macular GCC and its role as a potential biomarker in patients with Multiple Sclerosis (MS).

Methods:

A prospective cohort-study, subjects consisted of Relapsing-Remitting MS patients (n=62) and healthy controls (n=60). Eyes of MS patients were divided into two subgroups according to the history of the optic neuritis (ON). Standard peripapillary-RNFL and macular scan protocol, and retinal auto-segmentation of spectral-domain OCT were performed. Macular RNFL (mRNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL), and GCC (the sum of these former three layers) were recorded. The macula was divided into nine sectors using the ETDRS grid (4×9=36 variables).

Results:

In total, 50 eyes of 36 patients had previous ON attacks. 35/36 GCC parameters were thinner in MS patients and subgroups compared to the control group (p<0.05). When the eyes with and without a history of optic neuritis were compared, 25 of 36 parameters were thinner in those with ON. There were strong correlations between visual acuity-GCC parameters and EDSS scores in patients with a history of optic neuritis. However, no such relationship was found in those without an ON story.

Conclusion:

Ganglion cell complex gets thinner in patients with MS with a decreasing order of GCL, IPL, and mRNFL. The examination of GCC in detail could be a beneficial biomarker for MS.

How do intracranial tumors associated with visual pathways affect quadrant and sectoral based optical coherence tomography measurements: The effect of intracranial tumors on RNFL and GC-IPL thickness

AIM

To investigate the quantitative sectoral and regional changes of retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL) thickness in different types of intracranial tumors associated with visual pathways.

METHODS

This comparative retrospective study included 58 eyes of 30 patients with intracranial tumors and the data of 62 eyes of 31 healthy subjects. The RNFL and GCIPL thicknesses were analyzed using spectral-domain optical coherence tomography (OCT). The tumors were classified into ones that affect pre-geniculate and post-geniculate pathway.

RESULTS

The mean RNFL thickness in temporal quadrant was significantly thinner in eyes with intracranial tumors affecting the pre-geniculate optic pathway compared to controls (p = 0.04). In contrast, the mean superior quadrant RNFL thickness was significantly thicker in eyes with brain tumors associated with post-geniculate optic pathway (p = 0.01). The mean GC-IPL thicknesses of the inner ring superotemporal, superonasal, inferotemporal and inferionasal sectors and outer ring superonasal and inferonasal sectors were significantly thinner in eyes with intracranial tumors affecting the pre-geniculate optic pathway compared to control eyes (p = 0.02, p = 0.001, p = 0.02, p = 0.003, p = 0.008 and p = 0.03 respectively).

CONCLUSION

The results of this study showed that significant changes can be seen in the different RNFL quadrants and GC-IPL sectors in eyes with intracranial tumors affecting pre-geniculate or post-geniculate optic pathway. OCT is a very useful imaging technique to quantify these structural changes which take place during the neurodegeneration process of visual pathways in intracranial tumors.

Direct and transsynaptic retrograde degeneration and optic nerve head microvascular changes in patients with hemianopia

PURPOSE

To investigate optic nerve head (ONH) microvascular changes secondary to transsynaptic retrograde degeneration (TRD), comperatively with direct retrograde degeneration and healthy controls.

METHODS

Patients with hemianopia due to intracranial lesion included in the study. Intracranial lesion was categorized by location: postgeniculate (causing TRD), chiasmal (causing direct retrograde degeneration). For the postgeniculate lesions, the eye on the same side of the lesion was defined as the ipsilateral eye and the eye on the opposite side as the contralateral eye. Optic disc microvasculature was evaluated with the help of optic coherence tomography angiography.

RESULTS

Sixteen eyes of 16 patients with chiasmal lesion, 28 eyes of 14 patients with postgeniculate lesion, and 30 eyes of 30 healthy subjects were included in the study. Ipsilateral eyes of the patients with postgeniculate lesion had decreased vessel density at the temporal sectors compatible with the affected nasal side of the visual field. Contralateral eyes showed no reduction of the vessel density at the affected nasal sectors. The eyes with chiasmal lesions had decreased vessel density at the peripapillary region and nasal half of the ONH compatible with temporal hemianopia. Vascular changes in the chiasmal lesion were more prominent than those of the postgeniculate lesion. Retinal nerve fiber layer and ganglion cell complex thickness were reduced.

CONCLUSION

Vessel density of ONH was reduced in patients with homonymous hemianopia, providing evidence for TRD secondary to acquired postgeniculate lesion. Direct retrograde degeneration was more prominent in affected sectors when compared to TRD.