Golden Grapes

Biopsy of the optic nerve sheath was pursued due to progression despite medical management. During surgery no orbital inflammation was noted. Upon incision of the optic nerve sheath purulent material came forth. Gram stain showed gram-positive cocci in clusters. Cultures grew methicillin-sensitive Staphylococcus aureus. Anaerobic, fungal, viral and acid fast cultures were negative. She subsequently developed temporal field loss in the left eye. MRI showed extension of enhancement and diffusion restriction into the optic chiasm diagnostic of abscess(1). The right eye was enucleated to remove infected material. Gross examination showed thickening of the optic nerve and peripapillary retina with focal choroidal thickening, vitreous opacities, and adhesions of orbital soft tissue to the globe. Microscopic examination showed neutrophilic infiltrate with cell debris in the optic nerve, peripapillary retina, vitreous and choroid. A choroidal infiltrate consisted primarily of polyclonal plasma cells and reactive lymphocytes. There were no findings of neoplasm or granulomatous inflammation. The patient has been treated with long term antibiotics. Her vision has remained stable and MRI has improved. Though bacterial infections of the orbital apex, orbit and brain are well described and a case of S. aureus retinal abscess has been reported(2), this case of optic nerve/chiasm abscess is unique in the modern literature to our knowledge. The causative agent, S. aureus, is an aerobic bacterium that is carried by 20-80% of the population primarily in the nares(3). In a retrospective study of 163 patients with brain abscesses it was the causative agent in 21%, following streptococci(35%) and unidentified(27%)(4). An unidentified source of the abscess(as was the case in our patient) was common in this study, occurring in 19% of patients. The only more common sources were post-operative and sinusitis. In our patient, the host factor of immunosuppression due to diabetes likely contributed to infection establishment and progression.