Sequential Optic Neuropathy in Idiopathic Intracranial Hypertension: A Diagnostic Challenge of Possible Superimposed Nonarteritic Anterior Ischemic Optic Neuropathy

Idiopathic intracranial hypertension (IIH) and non-arteritic anterior ischemic optic neuropathy (NAION) are distinct optic nerve disorders that may present diagnostic overlap in patients with optic disc edema and shared vascular or structural risk factors. We report a 40-year-old woman with obesity and systemic vascular comorbidities who initially presented with painless vision loss in the right eye consistent with NAION. Four months later, she developed new left optic disc edema, accompanied by headaches and pulsatile tinnitus. Neuroimaging demonstrated partial empty sella, posterior globe flattening, and bilateral transverse sinus stenosis, and lumbar puncture revealed elevated opening pressure with normal cerebrospinal fluid composition, supporting a diagnosis of IIH. Following treatment with carbonic anhydrase inhibitors, papilledema partially improved; however, a new inferior arcuate visual field defect with worsening disc edema subsequently developed in the left eye, raising concern for possible superimposed NAION. During follow-up, disc edema gradually resolved while the visual field defect persisted. This case underscores the diagnostic complexity of distinguishing possible superimposed NAION from progressive papilledema-related visual loss and highlights the importance of considering ischemic optic neuropathy when new or asymmetric visual field defects develop in patients with IIH.