Optical Coherence Tomography Findings in the Optic Disc Before and After Removal of Brain Tumor in a Case of Foster Kennedy Syndrome.

We report a case of Foster Kennedy Syndrome (FKS) caused by a frontal lobe tumor in which the optic disc (OD) shape was first monitored by optical coherence tomography (OCT) before and after tumor removal. A 56-year-old male complained of decreased vision in the left eye and an abnormal visual field in both eyes. The OD showed swelling and redness in the right eye and paleness in the left eye. OCT was used to measure the thickness of the retinal nerve fiber layer (RNFL) and the optic nerve head (ONH). The average OD thickness in the right and left eyes was 647 and 335 μm, respectively. Goldmann perimetry revealed an enlarged Mariotte blind spot with paracentral scotoma in the right eye and central absolute scotoma with horizontal hemianopsia in the left eye. FKS was suspected, and MRI revealed a lobulated mass outside the brain parenchyma of the anterior base of the skull, severely compressing both the frontal lobes and the corpus callosum. The patient underwent surgery for tumor removal. Six months after surgery, the visual field improved, but a central scotoma remained in the left eye. The OD thickness in the right and left eyes was 360 and 279 μm, respectively. RNFL thickness decreased preoperatively in both eyes, reaching the atrophic range in the left eye. In conclusion, OCT analysis revealed edema in the swollen OD and in the atrophic one in FKS. Notably, the ONH may be within the normal range in the early stages of the disease.