Neuromyelitis optica spectrum disorders and anti-myelin oligodendrocyte glycoprotein positive optic neuropathies

Abstract

Aim: To describe the clinical characteristics and treatments associated with antibody positive optic neuropathies including anti-myelin oligodendrocyte glycoprotein (MOG) and anti-aquaporin 4 (AQP4), alongside diagnostic modalities, investigations, and outcomes.

Methods: A cross-sectional single-centre retrospective case series consisting of 16 patients including 12 anti-MOG positive patients and 4 anti-AQP4 positive patients. Each of these patients had clinical signs and symptoms of optic neuritis and consisted of all patients who had a positive blood antibody result in our centre. Clinical findings including presence of a relative afferent pupillary defect, colour vision and disc assessment were recorded. Structured clinical exam and multimodal imaging was undertaken sequentially on each. Optical coherence tomography (OCT) scanning was preformed to examine the correlation between ganglion cell layer (GCL) thickness and visual acuity (VA) at presentation and as a determinant of final visual outcome in both groups. Initial and long-term treatment is also summarised.

Results: A total of 16 patients were included in the study consisting of 12 anti-MOG and 4 anti-AQP4 positive patients. Nine of the 16 patients were female and the average age of onset was 29.2y in the MOG group and 42y in the AQP4 group. There was no statistically significant correlation (Pearson correlation) between GCL thickness and presenting and final VA [r(10)=0.081, P=0.08 and r(10)=0.089, P=0.34 respectively]. The same statistical analysis was performed for the correlation between retinal nerve fibre layer (RNFL) and VA and similar outcomes were observed [r(10)=0.04, P=0.22 and r(10)=0.09, P=0.04]. No correlation was seen for initial RNFL thickness and final visual outcome in this group either [r(2)=0.19, P=0.38]. Visual field testing and radiological findings for each group are described.

Conclusion: No correlation between initial VA or RNFL and final visual outcome is identified. A broad range of visual field and radiographic findings are identified, a consensus on treatment of neuromyelitis optica spectrum disorders and anti-MOG positive optic neuropathies has yet to be accepted but initial high dose immunosuppression followed by low dose maintenance therapy is favoured.

Keywords: anti-aquaporin 4; anti-myelin oligodendrocyte glycoprotein; antibody; neuromyelitis.

Figure 1. An example of ganglion cell layer analysis of a patient with right anti-MOG positive optic neuritis

Marked thinning of the GCL in his right eye is noted in comparison to his left.

Figure 2. An example of a retinal nerve fibre layer analysis in a right anti-MOG positive optic neuritis with a swollen disc.

Figure 3. Octopus visual fields of a 35-year-old female with bilateral anti-MOG positive optic neuritis which displays constriction of inner field and enlarged blind spots bilaterally.

Figure 4. A coronal MRI showing bilateral enhancement of both optic nerves in female with bilateral anti-MOG positive optic neuritis.

Figure 5. Coronal MRI demonstrating high signal in canalicular components of both optic nerves with prechiasmal expansion in a patient with bilateral anti-AQP4 optic neuritis.